Amp came in with shorted FETs on 1 side of the PS and 1 bank of the output, see 1st pic. I replaced the known defective parts. The amp powers up and has drive signal on both output sides and they match. The issue is the output under load at the speaker terminal.

With a 40hz signal input, and a 1ohm resistive output load, 1 side(negative terminal) looks like it is shifted slightly from the other, see pic 2 set to DC. The 3rd pic is set to AC for a better view. When the signal volume is increased to a higher level, the output begins to distort and starts drawing excessive current, see 4th pic. This level is well before clipping point. I have set the DC offset with the 1 pot to zero at idle but I'm not sure what that 2nd pot is used for. I adjusted it but didn't see any change, it's back to it's original set point. With the amp running at a low volume and no output distortion for several minutes I see no abnormal heat build up using a thermal camera. Any clues?

I am looking to buy a TP BIIIse Pro. I would prefer the 9028 version.

This project should be placed somewhere between Digital and ChipAmps 😉 It's my new volume control module basing on WM8816 from Wolfson. I call it 'WM STAMP', because executive part of it is very small.

Some details and basic functions:

- gain range from -111.5dB to +15.5dB
- gain step size: 0.5dB or 2.5dB

controls:
- IR remote (program can learn every RC5 remote commands)
- encoder
- standard, analog pot (ADC)

- optoisolation
- LCD or VFD 2x20 display
- backlight adjust

- output for 8 relay selector
- mute
- optional name for every input (like 'CD', 'DVD', 'TUNER', ...)

WM8816 is similar to PGA2310, but... opamps are outside 😉 This give many possibilities:
- many single opamps can be used
- discrete stage
- using some high power opamps we get good, headphone amp

Schematic diagram



I found WM8816 chip in:
Marantz PM-15S1 Reference Series Integrated Stereo Amplifier
Marantz PM-11S1 Reference Series Integrated Stereo Amplifier

Hi I broke my ankle and dislocated my foot so I am down for at least 10 weeks. so I am trying to figure out how to plan my next speaker. I want to downsize the excellent small thors. I already have switched to the nextel drivers and with a lot of help got them working pretty well in the old boxes. I rarely listen to them as they are downstairs and I really want to move the music party upstairs. So this is an opportunity to design and build the boxes. Attempt to mimic the small thor design making it smaller sacrificing bass. I would like to stay with the mltl style but there is very little information on how to do that. the fs is 40 on the woofers and the quarter wave would be just over 84 inches. the thors have a fs of 34 so they need 102 inches so I am pretty sure this will not work but can I change the length of the speaker by 83%? At this time here is my plan


design and build the boxes
use the current crossovers and measure

replace the parts in the crossover to get a slightly decreasing fr.
put is all together and live in musical bliss. here is a rough drawing of my plan for the boxes.

Hi all

I have a cassette stereo from an early 90s Volvo (stereo model TD-603) which I've got working again and now am putting Aux/Bluetooth inputs and removing the cassette player.

So far I've had good results tracing the tracks from the cassette pre-amp to what appears to be an audio processing chip (DIP20 Toshiba TA7764P). I've inserted new audio signal input leads close to the chip, leaving in the caps between signal lead and the chip (2.2uf 50v electrolytics). I cut the tracks near there, removing all the cassette pre-amp circuitry. This seems to work as it should with reasonably clean signal at the right level.

My questions would be...

* Should there be different caps (to the pair of elec. 2.2uf) or any other circuitry before the TA7764P? Both from an audio quality and protection point of view? It's going to have both Aux in, and a Bluetooth unit. I guess the Aux input may need to be a bit resilient because it will take various input devices - eg phones, mp3 players etc with different output levels etc.

* And on the subject of caps - I did have to replace one or two of the large ones - the biggest one had leaked and caused PCB damage. The circuit board is full of electrolytic caps (40 odd). If it was only a handful I might consider re-capping just to re-furb a 30-year-old device, but is there any in particular caps that would be a worthwhile swap? And if so, should I replace any with Tantalum or like-for-like LESR caps - or so-called 'audio' caps? (Without wishing to start a bar-room fight).

* I've read that it's good to short/ground unused audio inputs, to remove unwanted noise - but is it always the case? I am nervous about shorting anything! So should the Aux jack socket be shorted when there's no input (given it's in a car)? The 1/8" socket unit I have has extra pairs of pins that short when there's no jack in, giving that option. And - the Bluetooth unit I ordered (when it arrives) has an Aux input, which gets over-ridden when Bluetooth is active - is it OK to have a shorted Aux input into that, if I use that?

* The power supply for the Bluetooth unit: It hasn't arrive yet, but just to get it ready (the BT unit takes 5v-32v): I have a 7805 and a B0505S DC-DC isolator (incase it needs that). What would be the advisable circuit component sequence here, combining the 7805 and B0505S plus caps?
With caps, in the datasheets the B0505S specs 4.7uf in 10uf out. For 78XX it's 0.33uf in 0.1uf out.

Thanks for looking at this.

Cheers
Jim

Thought that I should report my latest fun with the "big-rig".

Uncoiled a "2mm square" (14AWG?) inductor and cut it in 1.2 meter lengths. Connected these bare/naked copper foil/ribbons to my speakers and experienced the best sounding cables so far in my book.

I have not done any A/B tests yet but will do soon.

Earlier I have tried Red Dawn, $1600 AudioQuests and several other cables, these are the best so far. They sound a little cleaner, more resolved than other cables I´ve tried. It´s like the high range is "cleaned up" and also the low level resolution seems to be better in the mids and high´s.

Must compare back and forth a couple of times with the old cables to make sure I´m not fooling myself . But there seems to be a not so small improvement.

It takes 10 minutes to make these cables and a coil is about $15!

My friend with the $1600 Audioquests did sound a little bit worried on the phone when I told him about this cheap, simple solution. 😀

/Peter

Original genuine Honey Badger PC boards (one pair). Unmolested in original bags. $39 plus actual shipping cost.

Too many projects, too little time...

These are currently sold out on the diyaudio.com store, of course.

Hello Guys, I hope you are fine. I upload this diagram concerning to an Class H American Audio amplifier which does not activate the high rail (+/-125V) to the output stage. This amplifier is supplied with +/-63V for low voltage and +/- 125V for high voltage but the man who is checking it out, said that when the volume is turned all way up, five volts are only given to the final stage for both rail. The amplifier sounds good but the output power is lesser than it can deliver. What test do you suggest for this amplifier? Thanks beforehand.

Based on the VH Audio's design, I made a pair of the OCC 5N 28 awg solid core silver cables last week. The results are amazing: open sound stage, airy, focused images and very detailed. I can hear more weak music tones and can now define the "distance between layers of music". 😀 They beat my 3 other diy solid core silver rca cables. 😡















What I'm going to do next? I'll re-do those cables which were twisted conductors in design 😀

I found 4 x "NOS" ILP HCA40 modules.

HCA40 data

Anybody know what they sound like / got experience with them?

Extract from the datasheet:
"The ILP HCA40 audio amplifier module offers the ultimate in high fidelity performance.
The unit, which is strongly biased into class A, exhibits audible smoothness and clarity and has been designed for the ultra high definition perfromance associated with class A operation."

Don't have a PSU at moment to test myself, but sounds interesting.

First off I want to thank everyone ahead of time for their time. I'm no audio or electrical engineer. I'm just a guy that wants to sit down after working the day job and then working on the farm and relax and enjoy some music.

I have dappled over the years and played around with various gear. Recently I liquidated alot of items to just settle on something that I feel I will like. I do enjoy the Dynamics of horns and just bought new two way Jubilee speakers and ordered radian PB950 drivers with beryllium diaphragms.

I'm older so I do have a nice turntable and enjoy vinyl. I also have a DAC2 from benchmark and have about 1tb of music on a hardrive. My other components are a tavish design phono preamp, the dude tube preamp, and I plan to use a citation II on the horns and a classe DR-8 on the bass bins.

So to be honest the active crossover and EQ of all of this will be new to me. I wanted to stay all analogue but looks like if I want everything dialed in right I have to go digital on the front end. This will allow me to crossover around 500hz, EQ, and get the time alignment of everything right. I want to learn more about all of this but between 60 hrs a week and also having cattle, I do not have time to research and learn more. So after some brief reading the DEQX HDP-4 looks like it is the best product on the markets for what I need to do. It does hurt my feeling knowing I will take my vinyl concert it to digital and then back to analogue but I see no way around this.

So is the DEQX the best product for what I'm trying to do? Also is the hardware in this unit some of the best on the market? Obviously I want quality A/D and D/A converters... I can find very little info on what hardware is in their units...

Wondering which microphone and which software are "best in budget" class for eq/room correction. Wondering which pay-for software is good and also which "free" software is also decent. Thank you.

Hello.

For free, you only pay shipping, I have a Stereo ASP for Lx521.3 speaker.
This is the 3 channel version, you need a crossover between midwoofer and midrange (1x 4mH coil and 1x 12uf cap).

I could not test it but when I got It some years ago it was working.
Maybe I have the proper P.S. too that would be included for free.

Selling my beloved AMC CD9 which I have modified and refurbished over the years. I am the original owner.
It sounds nothing like the stock; happy to provide the list of modifications.

The unit has two line outputs:
1) Opamp output with stock Philips NE5532N
2) Tube output
I can add 3 more opamps (BB OPA2134PA) if you want to try them out

Changed tray/laser assembly a year ago so you're good to go for 10+ more years.
If you live in the Bay Area auditioning can be arranged



Price is $500

Can anyone recommend a reasonably priced audio frequency spectrum analyzer which accepts electrical line level inputs?
Thanks,
Steve

Tip: Turning Mounting Hardware Black

Sometimes when installing a control pot rotary switch etc.
It would be nice to have the hardware black to match the panel or knob.

A simple solution that I found is to use some cold gun bluing
solution typically used for touchup on to turn the hardware black.

I normally will clean the hardware well and sometimes even
lightly sand it to get through any plating to the base metal.
(cleaning it well again after any sanding)

Put a little of the solution at the bottom of a paper cup.

Warm the hardware (a cigarette lighter is an easy way) and
drop it into the solution swirling it around until it turns black.

When done rinse well with water and lightly oil to prevent rusting
I typically buff it with a tissue or paper towel. to remove the excess
oil and the excess film of black on the hardware.



Please add your tip

Hello. Is this amp AIYIMA TPA3255 Power Amplifier 300Wx2 Class D Stereo Digital Audio Amp HiFi 2.0 Sound Amplifier Speaker Home Theater DIY|Amplifier| - AliExpress good enough for magnat supreme 202? I have heard good things about AIYIMA but i wonder if it can handle 200RMS without distortion.

Hi Guys,I'd appreciate if any of the experienced guys in here could refer me to a source which sells bulk flexible power cables made of pure copper or silver which is built by 2.5m"m *3 internal wires with non Chinese golden plated U.S plugs&IEC as well as to reasonably priced bulk XLR flexible interconnects made of minimum 4N silver or 5-6N copper with or without XLR connectors .I prefer all those cables to be made of 5N-6N silver.
I thank you in advance for your assistance.

I just found some panels loaded with 63 of these things. Mfr logo is 3 arrows pointing up and to the left. Date codes are 1998-1999, so they're not that old... Any idea who made them and what the "K" variant is? I find no data on it.

The new Avermetrics AverLAB Audio Analyser looks pretty interesting, especially at the $3000 pricing, it have the analog performance I'm looking for, and the digital audio I/O I need.... And I like that it's using ethernet instead of USB for the computer interface.

Do anybody know about the company or it's product ?
Anybody actually tried the AverLAB and can tell about it ?

Avermetrics | AverLAB

Hello Chaps,

I am trying to get in touch with SP 5A preamp owners. I would like to find out how versatile is the adjustable gain for low output MC cartridges. Is the input impedance adjustable between 100 and 47K Ohms?

Kind regards,

Horacio

Just found some in an old box. Looks brand new. Two gauges apparently. Would you recommend it for internal speaker wiring?

Can't find something with this color code. Should be 5 ohms, 5 Watt metal I think.

Would someone be able to help a brother out finding the grid current draw during A2 operation of a 2A3? Can't seem to find a datasheet with positive grid information. I would like to needlessly shunt regulate the negative supply of the source follower with a VR tube, for no other reason than it is pretty, and I have the space. I am concerned though, that during A2 operation, too much grid current will need to be sourced extinguishing the regulator.

Hi Folks;
This plate amplifier has me perplexed. There is 120 Hz buzz on the speaker output (low level) but audible. I don't have a schematic for this model V2W but maybe this is a simple problem?
The buzz on the speaker seems to be present on one power supply rail. I have straddled the noisy side with another 6800 ufd cap with no effect. First image is the speaker output;

Hey people! I've had an idea on my mind for years and now suddenly I have lots of time and little to know money so I was thinking of taking a crack at making compression drivers for true low end frequencies. (I have no Idea how low I can get)

Ideally im imagining a structure of epoxycrete with a very large, massively dangerous neodynium ring magnet, and a steel ring to create an appropriate magnetic field.

If this doesn't work, I was also considering trying what, funnily enough, might be much safer; a massive field coil with a substantial variac.

I thinking something like 5-6" driver ports

as far as I can tell, the impedance matching will be difficult, possibly requiring a very large horn, but I haven't done the math.

Also finding a material with a super low elastic modulus that I can also form into a dome readily, but still be light and stiff enough to handle the forces inherent in something this silly. I might need to dig up some of my old materials engineering texts to see what I can find. Possibly a novel constrained layer damped dome utilizing both organic and synthetic materials to achieve something without rediculous slew or oscillations in the audible band.

Am I crazy? good crazy? bad crazy? a fool? a mad scientist?
I've been milling this over in me head for around ten years and im ready to make it happen.

PLEASE share your ideas and opinioms! cheers!
(also forgive any typing errors, my keyboard is on its last legs)

Hello everyone. I just started reading about tubes from the book "Valve Amplifiers" from Morgan Jones. It introduces the cathod bias resistor and the cathod bypass capacitor by first explaining what happens if we omitt the capacitor. We actually have negative feedback which increases the anode resistance and decreases the gain. It starts by computing the gain before we add the cathode resistor ( A = μ(Rp/(ra+Rp)) ). When we add the resistor, the new gain is calculated by the universal negative feedback formula Afbk = A/(1 + βA). The feedback fraction β is equal to Rk/Rp and A is the gain we calculated previously. So far so good. He then proceeds to showing how to find the new anode resistance ra' and he uses the following formula: ra' = ra + (μ+1)Rk. I tried deriving the formula by setting Afbk = μ(Rp/(ra'+Rp)) = A/(1 + βA) and then solved for ra'. I ended up with ra' = ra + μRk and not ra' = ra + (μ+1)Rk. Why does this 1 exist there? Could you please help me because I always try to fully understand everything I read about and if I don't I give up....😕😕

If Viktor and Elekit made a 3.0 version of the TU-8600 here's what I'd love to see (so much so that I'd buy it and sell my 1.0 version).

Remote Volume -- Khozmo. khozomo remote attenuator. Isn't the ALPs pot a bit of a weak link anyway?

Single Ended Inputs -- Increase from 1 source to 2 sources minimum.

Bottom Panel Access -- It would be cool to have a bottom panel escape hatch where you could more easily enter/exit to swap out caps.

Feedback Adjustment -- I know this is asking a lot (the 3 above are more easily doable), but it would be cool to be able to adjust the feedback to one's subjective tastes. This is least important though--in my mind.

As a disclaimer, I am not trying to be critical. I love Elekit and Viktor. I do, however, think there are many people/customers/enthusiasts who would love these features a bit more than chasing tubes that cost $1k+. Also, the bottom hatch could allow people on a budget to choose their upgrades based on their situation and come back later to add in boutique caps, etc.

Viktor mentioned a remote might be coming. Can't wait.

Which FIR processors suitable for install loudspeaker management will allow downsampling by channel?

I'm researching platforms with FIR processing for phase correction. Many comments are made about the available number of taps for lower frequencies and how there never seems to be enough. But this can be done with significantly fewer taps by downsampling the low frequency channels in the processor, correct? Looking at some different platforms however (hoping for "affordable" ones like Xilica Solero) I don't see any reference to this. Not sure if it's unavailable or just weak documentation.

Hi. Does anyone know how to get the rms noise voltage for a given bandwidth from a spectrum graph? I mean, using a program like ARTA, REW or similar, get a noise plot using the Spectrum Display option and calculate e👎 or e^2👎.

Can't find something with this color code. Should be 5 ohms, 5 Watt metal I think.

I picked up a couple of tube mono blocks a little over month ago and I want to make sure I'm setting the bias at the correct level. The previous owner told me to set the bias to 90 but he also said some people prefer running them at 70. The bias is set externally and is shown on a digital readout. I've tried to set it as close to 90 as I can. The bias seems to float between 85-95. I'm using them with a pair of Wilson Watt Puppies 3/2 and when I push the amps the bias will go up to about 150. I know these are demanding speakers so I'm careful not to push the amps too much. Does this sound about right? Should I be setting the bias to something else? Thanks for any help you might be able to give me.

The amps are Antique Sound Labs KMP60-FOX DT 6C33 "Bella 60 Custom" mono blocks modded by Response Audio around 2006. I've spent hours trying to track down a user manual but have had no luck so far, it doesn't sound like there are too many of these amps out there and even fewer modded like mine.

The mods listed below appear to be what was done to my amps but could be slightly off.
**SoniCap Platinum Teflon coupling capacitors
**AuriCap film interstage coupling capacitors
**Upgraded power supply capacitors now housed inside the chassis.
**Mills non-inductive grid resistors.
**6C33 output tubes x4 pieces
**Sovtek 6SN7 input/driver tubes X10 pieces.

And these are the listed specs:
OUTPUT POWER -- 50W per channel (conservative)
Frequency responsible at 1W -- 18Hz--25000Hz + 1dB
Frequency responsible at full power ---20Hz--22000Hz + 1dB
Circuit Design --- Push-Pull - zero feedback, Cathode follower output
Distortion at 1W/45W-- <0.8% / <2%
Distortion at full power --- <6%
S/N Ratio -- 86dB (1mV) ( with A weight 95db 0.6mV)
Input impedance -- 100K
Output impedance -- 4, 8 & 16 ohm
Power request -- 340W MAXIMUM 115VAC
Input sensitive -- 1.2V
Dimensions in inches -- 15.75" X 10.6" X 9.5"
Net Weight 42 lbs. ea.

Photos!

Hello everybody,
I am new here and not sure if I post this in the correct thread. I'm currently working on an amplitude modulated microphone. It is a very old idea published originally in the 60th.
For it to work I need to generate a carrier frequency that is fed into a bifilar wound transformer to generate a higher voltage version of the same carrier with 0 deg phase and 180 deg phase.
I got it all working using a 10 kHz carrier signal. However so far I generate the signal using a function generator. Obviously not very convenient.


What I need is a reliable circuit that creates a 10 kHz (or similar frequency) sine wave with good frequency stability. I experimented a bit with quartz stabilized Colpitts oscillators but the results are not encouraging at all. I never got anything that looks close to a sine wave. All waveforms I got were quite distorted.


I could use a DAC and a filter but I thought there must be an easier way.

Any suggestions?


Thanks

Tube-breadboard adapters are available for prototyping on a standard breadboard (with a 2.54 mm hole pitch)

Appearance


Appearance with socket


Three types of sockets, Magnoval, Octal, Loktal

Completeness - board, sockets, pins

Cost $60 (free shipping)

The adapters can be installed on a standard breadboard, such as:

Hi.
when replacing electrolytic capacitors, are there specific types that need to be chosen?
what i mean is, when removing say for example a 6800uf 50v cap, which are relatively easy to source, there are many other things it seems to consider when you look at the filter choices.
There are no details of what these are on the original caps so how would i know for example what the leakage current,ripple current and series are? do these matter much, i guess they must do or they wouldnt be there as a choice or are these for more critical applications than for an audio amp?
i obviously dont buy any rubbish,i only get, where i can, panasonic,nichicon,rubycon etc but i always wonder about the other filters and whether they are important.


many thanks


paul

I have an 6500 primary to 8 ohm OPT. If I have a theoretically flat 4 ohm load is the OPT functionally equivalent to a 3250:8 OPT? Is it as simple as that?

Regulators.

Im in the process of adding regulators to my preamp and have built the tracking prereg circuit as illustrated in the LM317 data sheet http://www.national.com/ds/LM/LM117.pdf.

Now Im using apprx 18v input lines and the max voltage I can get on the output is only 8.54 volts. I was hoping to get about 15v, and im assuming that its impossible to get the full input on the output. Is the circuit running right?? and if so what can I change to increase the max output, if thats possible. Im all new to regulators so dont know much about them yet.

Cheers Matt

Hi, on the bay I've found a pcb kit with components (no tubes nor chassis, nor transformers, just pcb and pcb mounted components) with the attached schematic.

I'm thinking about buying it, because it's just around 20 euros, and I would like to mount more powerful octals (anything bigger than KT88 that doesn't costs like KT120&KT150?), and apply some mods, like shunt feedback and fixed bias.

What do you guys think? Is it something that can sound good?

Thank you in advance.
Roberto

I built a blameless amp based on a PCB from Jim's audio, but have been doing some tweaking to some component values. Mostly due to VAS problems relating to CCS. The rise time was really poor from the beginning, so I wanted to improve that, and it did not seem stable at transients. Also transients were carried over to the IPS CCS as it was.
I see ringing on the current of Q7 collector, and I think this is the root of my problem.

I tried replacing the VAS CCS with a resistor in sim, and then the square wave is super clean. Real life is worse than the simulation, and I see a significant change in the waveform when touching Q7 (VAS CCS). (see scope pics)

I plan to change the compensation later, but as it is now, it's standard miller.

Hope somebody has some easy fix for my problem 🙂

Somhow I made a doble post - maybe by doble klikking I dont know ---

Admin please delete this post, sorry for the trouble 🙂

What celebrates this amplifier is the depletion Mosfet LND150 (wrong on circuit). This component is an exception among transistors to have very linear transfer function at 5ma.

It has extraordinary high early with total 2.5pF on the drain, which makes it premium VAS transistor.

To keep low distortion and symmetrical saturation I used IRF9610 as CCS.
To get best sound of it I reduced the Blameless of Self to minimum, however the distortion at 1W is 0.004%. What makes this amp Audiophile not only it has dominant even order harmonics, it has OLBW of 36khz. The slew rate is 30V/us and can give undistorted full power to 130khz.
Of course it needs habitual accessories to be added.

For sale I have this super nice 100W Class A amplifier designed by no one else than ZenMod!

I assembled everything and realized my chassis were not big enough for all that glorious Class A and also my room was unfortunately too small for all the heat generated by these mono-blocs.

I have one channel assembled, the other one you just need to solder the output devices which are included. All transistors have been bought matched by ZenMod.

The input stage are assembled, just need to solder the JFets. I also have a second set of input stage almost fully populated. Everything is untested (never been connected to power but should be working perfectly.

Here's a few pictures of the beast in parts!

I'm asking SOLD$USD + shipping for the lot, offers are welcome but no low ballers. Shipping in North America preferably!

I also have two beautiful Audio Supreme encapsulated transformers from Toroidy. These are totally new, unused and bought for this project. I can sell them separately for $USD each plus shipping (they costed me 244Euros each plus shipping + import taxes, so you're getting a good deal). Again offers are welcome but no low ballers.

Here's the specs from Toroidy (I will double check this since I thought they were dual secondary and not quad)
TS 1200VA PRI: 119Vac
SEC : 4 x 17.5Vac (17.14A)
- Epoxy filled in the stainless steel box
- Need long leads (40cm solid wire – where possible)










Thanks
Do

Hello !

Maybe someone has encountered this type of defect before, a location would shorten the repair time.

Panasonic SA-PT 150 which has all the voltages ok from the source, checked one by one (I haven't checked the regular voltages on the board yet), has a strange behavior, starts from "Power On" -> displays AUX and freezes like this or starts from "Open / Close" -> displays "Open" and freezes like that.
Before and after freezing, do not accept any other commands.

Because I worked more on it today, I had the opportunity to notice that the finals heat up after a while, 20-30 minutes, about 60 ° C - which is much, I suppose at least one final is burned. I will try to isolate pin 5 STBY and pin 9 MUTE and power supply and see if they work, at least to see which consumes so much. I don't know if this is where the "freezing" comes from.

There is something strange, on the main board it is marked -13V at pin 10 connector H2002 (power plug) although on the diagram it is marked VCC_CTRL and in reality they are + 0.7V there. The same for pin 4 connector H2002 where it is marked + 13V although on the diagram and in reality it is + 9.1V.

Thanks.

Hello. I’m in search of Screws/bolts for fixation of Kef B139. I bought the speakers (Kef Concerto) back in 1973. Recently I replaced the T27’s and then I noticed, 2 screws/bolts , of the B139 woofer were missing …
(please don’t ask me how this is possible..)
I searched the internet for days now, but I even can’t find which kind of screws this are.
I do know that the screws have withworth thread , but there seem to be 3 different kind of withworth-types..
The screws have a lenght of about 2cm and a diameter of approximately 5mm. (see pictures) .
The same screw is also used for top fixation of the crossover-filter SP1004.
Can anyone tell me more about these screws , or perhaps someone has a few spare or identical screws they want to sell to me?
Or someone can direct me (link) to a store where they sell such screws ?
Thank you very much.
Eric

I am creating this thread in an effort to both collect information as well as advices regarding the KT88 power tube. Its not intended to be a general vacuum tube thread but instead focus solely on the KT88 in terms of manufacturers, variations and quality. Information about this tube can be found spread out, but collecting info can be somewhat tedious and time consuming. One of the reasons I am creating this thread is because I am in the planing stages of my own KT88 power amplifier and this meant that I needed information in order to know what to consider.
With virtually no prior experience (never built a tube amplifier before), using what is available online is a very good idea, so to anyone who either recognize their own review or contribute in to thread, thank you.


To put it simple. Locate or establish a high quality budget friendly KT88 (B) or a premium KT88 (P) which is in production (very important). The former focuses more on keeping the cost relatively low yet maintain a "representative" sound profile and build quality, while the later focuses more on absolute premium in both aspects, also here, the cost is of less value. NOS tubes of yesteryear (besides reference) has to be left on the sideline. Using older brands as a reference is fine since does older tubes is what started it all. I have collected source links at the bottom of the page.

The main reason for looking at new production is that generally speaking it should be the same or even better than NOS, but mostly, I/we can collect them for use in the future. As you know, tubes are consumable and need to be replaced from time to time, NOS tubes run out and at that stage you are left with what is being produced today, so one might as well look at what is considered good in 2020 >


Beam tetrode. Upgrade of KT66, designed by M-OV (GEC, UK). KT stands for 'Kinkless Tetrode.' KT88 and 6550 are very similar tubes. GEC was active between 1886 and 1999. The KT88 was introduced by GEC in 1956 as a larger variant of the KT66. It was manufactured in the U.K. by the MOV (Marconi-Osram Valve) subsidiary of G.E.C, also labelled as IEC/Mullard, and, in the U.S., Genelex Gold Lion.

The GEC KT88 is the reference, this is the tube most drool over. A single GEC KT88 can demand £300 or close to $390 - for a single tube. Fake or used tubes appear to be relatively common.


The M-OV or MOV Valve company does not existing anymore. NEW SENSOR in New York today owns the brand rights of the 'GOLD LION' brand. That is all they own. They do not use the original tools, neither are their new tools copies of the original tools. The GOLDEN LION tubes, sold by NEW SENSOR, are made in the Reflektor factory in Saratov Russia, and inside I see the plain old Electro Harmonix construction, as they used always, which resembles their 6L6 optically. Which for me is not a real KT88. Sorry. You can think of this what you want, and you should. The Golden Lion tubes made by new Sensor have nothing to do with the originals, made by the MO Valve company. Also, the quality of New Sensor doesn't even close.

So I do not recommend the expensive GOLDEN LION tubes, sold by NEW SENSOR. For the half the price you have Electro Harmonix by NEW SENSOR, and to me they seem identical. Quality is the same (medium) level. Problem with NEW SENSOR tubes, was for me, they develop gas on stock. They were fine when I received them, but sometimes tubes can be on stock for a few years, and I had several that developed gas.

What follows is only my personal opinion, from selling tubes since the last 25 years. I would prefer them in this order. Please excuse me for being a bit direct, but I do not want to contribute to any fairy tales and other kind of obscure stories. So what is good is good, and what is bad is bad, I just say it here.

Number1: GENALEX/GEC. Made in England. NOS with good test data, which is all you need. As you can blindly trust most other data, such as leakage etc. The holy grail of course, not available, and no realistic solution for that reason. Be careful with used tubes of this kind, because prices are still very high, but a great brand will not protect you from being sold tubes at the end of life. I would say, this is something to buy only from reliable professionals. And typically not buy it on Ebay without return option.

Number2: Svetlana C-Logo KT88. Hard to get, but possible. Looking for NOS.... your hunt may be successful.Keep apart the Winged-C Svetlana which are the ones made by Svetlana, and the S-LOGO not made by Svetlana at all, by made by REFLEKTOR and sold by NEW SENSOR. In fact Svetlana Petersburg sued New Sensor for this, and the result was some kind of arrangement. Just the C-logo, new Sensor did not get under their control. Also the words 'St. Petersburg' may only be used if made there indeed. So the C-Logo is the proof for genuine tubes from St. Petersburg. So my number #2 choice here is the original WINGED-C Svetlana.

Number3: The most realistic good choice: Chinese KT88. These seem to have the best price / performance ratio, but the Chinese mix a few bad tubes under the good, always. They get away with that, and they know it. So what leaves the factory, is a strange mix of mainly good tubes, and a few bad ones amongst them. Unclear matching, and not enough burn in. This makes them very suited for professional sellers that have really good equipment. (Meaning not just a Hickok tester). In industry this is called 'uptesting'. So a good dealer separates the bad from the good, and offer the good ones to his loyal customers, with fine matching data. From a lot of 100, you can get a good selection of such quads. For the less good ones there is a nice market on Ebay, where good product feedback is for low price and fast shipment anyway.

VALVE ART KT88, which is a Shuguang Factory Tube. Shuguang is the largest tube factory in China, and they brand the tubes for everybody who wants it, with any brand whatsoever. So the black beauty, golden treasure, green dragon, Valve Art, and very many more fantasy names, they all come from the same factory outlet, called SHUGUANG. Since many Chinese tubes are now better than there reputation, they are here under preferred brands.

Number4: Electro Harmonix - Sovtek - Svetlana S-logo. All the same tubes, just another jacket. You can take the lowest priced, Electro Harmonix. That is because the more expensive brands, are not better specified, no longer life, and no longer guarantee. Electro Harmonix is a reasonable tube for a reasonable price.

Number5: New Sensor owns the GOLDEN LION brand now, and like all tubes from them, they come from the same factory, called REFLEKTOR.

All recent production Reflektor tubes show random vacuum problems, more than any other tube brand I know. NOS Reflektor is generally good quality, but not as perfect as Svetlana. However new production Reflektor, I find disappointing. Vacuum can get lost, just by stocking unused tubes, grid to cathode shorts develop after shipment, and parameters are quite variable in general. I even had tubes which were mounted in the socket with one pin rotated. Which indicates they are tested before socketing but not after.
GOLDEN LION seem identical construction as ELECTRO HARMONIX, and from selling them, I quickly learned, they show the same random problems as any other brand from REFLEKTOR. Since the extreme price difference is not justified by the brand name only, they seem too expensive to me. So they are ranked quite low at this list, because of bad price-performance ratio.

The rest - I do not number it from here.

- JJ tubes. I do not want to be the big complainer, but I am no fan from JJ tubes, because O once bought some variation of JJ tubes. They began to drift already on the tube tester. I don't know what caused that, and I sold the lot quickly on Ebay. Even mentioning the problem, but it seemed not to be a problem for selling them.
- Fullmusic. I had many tubes from Fullmusic, which was actually quite a while ago. They seemed not adequately burned in. Test data on the boxes was not accurate at all, and I had quite gas problems.
- Tesla KT88. I can not speak here for older production, NOS tubes. I had many new production KT88 when the factory in Vrusovic still existed, but defect rate was terrible. What worried me even more, they used the old tubes to recycle the pins. (so the 'pearls' which are piece parts they buy from vendors - that looks like a glass pearl with the tube pin coming out).
- EAT KT88. I have to say I know little about them. What I do know, the production tools from Tesla (above) are now in use by KR, who builds the EAT tubes. The price of those is unusual high. So given their performance is good, they still have a poor price / quality ratio to my opinion.

THE NEVER ENDING KT88 RE-BRANDING LIST- (THIS IS WHAT YOU CAN GET, BUT MAY NOT NEED IT)

Don't let anyone mislead you. If there is one tube that a whole crowd of fakers have jumped on, a long time ago, it is the KT88. Every self-respecting faker has "finest" KT88 for sale, and his own brand. Of course, some respectable companies also make finest KT88, but how to keep the those apart? Apart from the Tesla re-brands and re-makes, these are probably all China tubes and.... ALL come from the same factory in China.

When I first ordered tubes from CEIEC China in 1997, there was the sales engineer, who some of yo perhaps still remember, his name was Mr. Li. He told me: Sir, what brand do you want on them?... I said: Well, your factory brand of course! They said: yes sir, we have that too. I was so shocked by this. This shows how easy it is to get "your own" great brand of Chinese tubes. However, when you know the Chinese better you will learn that the way to get quality from them is hard, very very hard, and impossible for most. For them, something that "works" good is a fine product. They sure can make quality but they prefer to sense very delicately what your minimum acceptance level is, and simply send you that. So you won't complain, and they can send you the lower quality, that they know some other company will reject. (or has rejected, and send back). A lot depends on how having a long history with your purchasing channel, and how they have learned about you, and what you find out and not find out.

This problem comes from one particular and actually quite normal Chinese trade method. That is, you are supposed to pay the price they ask, when it is a reasonable price for you personally, like they know it, and like you know it. If you THEN bargain on the price, they regard you no future business partner anymore. You lost your face. Speak in our words, they regards you dishonest. Next thing is, they send you lower quality, that they feel better suits your dishonest price. This they do with an oriental smile on their face, and you get screwed of course. For them this is not screwing, it is giving you what you deserve. The other way around doesn't work, like giving them a real good price and expect real good stuff. They think you must be pretty stupid. So you see, how hard this is, and why so many bad Chinese tube stuff is around. There just is no good way to talk straight with them.

Audio Classic. Sorry folks just REBRANDED Chinese tube
Golden Dragon, England. Sorry folks just REBRANDED Chinese tube.
KR Audio of very old production are re branded Tesla tubes. Some years ago, they got control over old Tesla tools, and now build their own KT88. So this here about re branding, is about very early KR KT88.

RUBY TUBES. I don't see many of them any more, but it was just a re branding name.
IET. Sorry folks just a REBRANDED Chinese tube - gets a bit boring
PHILIPS Miniwatt. Probably Tung-Sol
TAD. Just a brand name, they buy where they like.
Mullard never made KT88

PSVANE is no tube factory, just a brand name. Probably these are made by SHUGUANG. PSVANE KT88 TII has a gray shielding. The shield looks nice, but I have no idea what the practical purpose of this is. I wonder if they put a side getter on the inside of this shield? Probably not. But... where has the side getter gone then? I hope they did not leave it away? Since with KT88 a side getter is a must have. This place of the tube gets very hot, and that's what a getter needs. (Psvane update will follow)

Shuguang KT88-T. (Tressure series) With black coating, purpose of the coating unknown. RSD.

FullMusic KT88/c with carbon plates. Definitely the use of carbon is not recommended by me. This will lead to low lifetime if combined with Barium cathodes, and is only advised for thoriated tungsten tubes, ever since the history of tubes. And no... this engineering law has not changed recently. Well, not that I heard of. Against all knowledge, it has been tried with 300B some years ago, and it these were the lowest lifetime 300B ever, called 4300B. Also the Carbon tubes from Alesa Vaic were a disaster. But.. who cares. We all want to learn from our own mistakes. It has not been tried with KT88, so here is the next experiment, but I have seen enough of it. Do you believe in this? Well good luck.

Northern Electric KT88 is most likely a Fullmusic KT88/c rebranded.

TRONAL. Just marketing Name / brand name.

WESTERN ELECTRIC. Now, Western Electric stopped making tube a long time ago. There is however Charles Whitener who build fully legal replicas in a small factory of himself. I heard some story, they want to build they announced quads of Golden Lion for 1700$. - More info is needed.

- Why TESLA KT88 is NOT JJ KT88!

In the socialistic Czech Republic, it was believed the government was the most suited to lead a tube factory. After 40 years this appeared to be a mistake, and the factory was privatized, and during this process split in several companies. Strangely, also the act of privatization, was carried out under socialistic view. To say it more clear, it was not sold to the highest bidder, but sold for 'good' reasons to 'good' people. Here are some details as I can reconstruct. Some parts manufactured those yellow color street lamps, and mercury light bulbs, etc. I don't know what happened to this part.

The Czech Republic State TESLA electron tubes factory was split in several companies, during privatization. Here is as far as I can reconstruct what happened. Some parts manufactured those yellow color street lamps, and mercury light bulbs, etc. I don't know what happened to this part.

The part that made the Audio tubes, like EL34, ECC83 etc, was sold to Jan Jorgo, who owns now the JJ company.

The part that made the transmitter tubes, and some magnetron tubes was sold to Mr. Malinivic, a very friendly cigar smoking gentleman. His office looked like a cafe because of the smoke. He called the factory TESLA VRUSOVIC. He bought this plant including the buildings. They made some pretty interesting transmitter tubes, some had laser cut grids from a solid block of graphite. I was there and I saw it myself, it was an amazing small machine, but worked beautiful. So they just blast away all graphite, until a solid part is left that is actually is as fine as a tube grid, with very fine 'wires' of graphite. These are miracles of manufacturing. Just touch this grid, and it breaks. Once in the tube they are indestructible.

There was at that time great dissatisfaction about the profit on the transmitter tubes, and some klystrons and magnetrons they made. These tubes have to be evacuated in ovens for four or more days, using lots of energy, and using up the lifetime of the manufacturing equipment. Comes to that a declining market for transmitter tubes, that could not be compensated with higher prices. TESLA VRUSOVIC thought they would like to build a KT88 also, because profits were better than with transmitter tubes. However, all tools were in the hands of JJ, so he had to remake them all, which he actually did.

HOWEVER.... it is not only tools that make a tube. They found that out the hard way. They lost most of the knowledge, lost unreplaceable machines, and happily fired what they thought were useless old workers. Modern times were coming. Good-bye Lenin. They later learned these old men, were senior tube experts that can't be found and they couldn't make (good) KT88 without them. When they realized what they had done, they couldn't get them back. I have visited that production line myself in 2003, but that was after the loss of expertise, and it was in a dying condition. They were building the KT88 line up from scratch, even recycling glass parts from broken tubes. What I saw was a big mess.

Getting back 25 years of experience, but from whom, and how? Questions.... questions... Many bad tubes were the result of these attempts. I was looking and the production line, it looked a bit sad.

There was from 2001--2003 some retro production of the TESLA KT88, with the blue logo. I had three charges of them, and the overall failure rate was 10% within the first six months use. From this the statistic calculations say you have 35% chances on ONE bad tube in a QUAD. As you can understand, this made this business not very pleasant to do.

APRIL 2006. TESLA FACTORY PERMANENTLY CLOSED. This moves TESLA KT88 permanently to the Hall of NOS Tubes - END OF PRODUCTION. Perhaps somebody will take their old tools and re start from scratch again. Well, good luck with it.

KT88 Current Production List.

Electro Harmonix. Made for them by Reflektor Saratov, Russia.
Pro: Matching is done good. No issues with the specifications. When I verify them on the Russian L3-3 tester, using special KT88 cards, all parameters are as they should.
Contra: As with all new production tubes from Reflektor, vacuum can sometimes get lost just in storage, or cathode to grid short or lost vacuum appears directly or short after shipment sometimes.
Overall: Best value for the money.
-
Svetlana Winged C. Also called C Logo, written: =C=. Made by Svetlana Petersburg. It is still under current production here, though this factory as said to be closed now. So after 5 years or so, I move them to NOS. This is the Telefunken from Russia. The crowd never honoured this factory as they still could, and per definition wants to wait until it is too late. Added this, they choose totally wrong sales partners, no good distributer, and tried to pick private orders at the same time. Moreover, to my opinion it was a serious mistake to supply New Sensor with their tubes, and allowing them to use the brand Svetlana.

New Sensor started to sell Reflektor KT88 under the Svetlana S-logo brand, and it ended with legal trouble, which ended with a solution which was not very favorable to Svetlana Petersburg.

When the factory was still running, I tried to contact the Russian Svetlana. Their website was totally fuzzy to begin with, about who was in charge. Very quickly I was in contact with several people, in different countries, who all claimed to be a manager and in charge for collecting the money. I did not trust this, and I let go of it.

S-logo Svetlana. Made by Reflektor in Saratov, sold by New Sensor USA.
Pro: This tube is identical to Electro Harmonix KT88. Look for the pro's and con's there.
Con: Some like it some don't, but myself I do not like playing with brand names. IF Svetlana, then from the Svetlana factory.
-
JJ Czech Republic has bought the complete equipment for making Audio tubes, from Tesla, in the 1990's, when TESLA thought the market for audio tubes was not interesting anymore. Tesla wanted to focus on Transmitter tubes only. What a BIG mistake that was from Tesla. In the years after the sell off, the audio market soared, and transmitter tubes are sold less and less. The people at JJ are clever, and focussed very hard on making a good KT88, and they succeeded.
Pro: JJ KT88 is a plug & play tube, easy to buy everywhere, price is low, and competition is high. Made on original old TESLA Machines. Not using the superb TESLA Cathode materials though.
Contra:Tesla to my personal opinion is the lowest quality tube there is, I had new tubes here, which seemed not burned in at all. Already after 24 hours, they had totally changed, and not for the better. Only short form data sheets seem tot exist. Like when they little, they can not say something wrong. If you want to check for specifics in a JJ data sheet, you won't find it there. Like they build something like an ECC803S, but add a short from of the ECC83 data sheet with it. So by their own data sheet, their ECC803S is only an ECC83. The JJ KT88 data sheet is made similar. Just what you need always, in in there, and the rest not.
Conclusion: Given they are the lowest price tubes also, we should not complain about this. Not without reason, they are often used by manufacturers as first supply tubes.

SOVTEK KT88. Made by Reflektor in Saratov, sold by New Sensor USA.
Pro: This tube is identical to Electro Harmonix KT88. Look for the pro's and con's there. What I like about this tube, is the coke bottle glass shape.
Con: Some like it some don't, but myself I do not like playing with brand names.

Source or Reference:
1) The KT88 / KT66 /6550 Directory
2) General Electric Company - Wikipedia
3) https://en.wikipedia.org/wiki/KT88
4) https://www.europeanaudioteam.com/en/e.a.t.-kt88-diamond-valve-wp000023.html
5) https://www.thetubestore.com/shuguang-treasure-kt88-z
6) http://www.shuguangdianziguan.com/product/
7) https://www.thetubestore.com/shuguang-kt88-98
8) https://www.thetubestore.com/preferred-series-kt88
9) https://www.tubeampdoctor.com/en/tad-kt88-str-blackplate-premium-matched
10) https://jacmusic.com/valveart/intro.htm
11) https://psvanetube.com/wordpress/product/kt88-tii-quad/
12) http://www.kraudio.com/
13) https://sgdz.world.taobao.com/shop/....14.17.60c94cc2oZjhKX&user_number_id=90563453
14) https://www.hifi-amplifiers.com/en/...e-quad4-kt88t-vacuum-tube-matched-p-5246.html

Hi everyone!
I am a new member so thanks everyone for the very useful infos I already found here, I hope to write in the right section and that I will understand your answers 🙂
I am a newbie, and this is my first build, I did some simple repair to my tape recorders (mostly mechanical and recap) and I'm studying the basic of electronics, but I am still at the beginning. Anyway I can solder reasonably well, can read simple schematics, and have some basic tools (including some components, breadboard and multimeter), so I feel ready (maybe 🙂 ) for my first project.

I am a musician and "sound artist" and I need a simple mixer for live reproduction of some field recordings and electronic sounds in places with no PA and no electricity (I will use battery T-amps and small passive speakers), so I am planning to build a virtual earth mixer to my specific needs:

- portable: maybe in a guitar pedal enclosure;
- battery powered: with two 9v batteries or two 12v Li-ion battery packs;
- 3 or maybe 4 stereo inputs: I have two digital players (with line out) and some cassette recorders, probably unity gain will be ok;
- two stereo outputs: I need to send the stereo tracks to one stereo output or the other or both;
- no need for balancing/panning, master pot or eq;
- double gang pots for each stereo track;
- I may also need mute switches but I'll about it later.

I found some schematics here:
Simple Mixer Schematics
also discussed here in the past

I removed balance and master pots and made a drawing with scheme-it, I hope it's clear, at least to understand the idea.

Now with the questions:

Is it right? I am thinking to use NE5534, are the components values ok for those op amps?

In the sketch I just connected the input jacks to two identical mixers, is it ok or some kind of buffer is needed to split the signal?

Thanks in advance for any help!

So.
The last time I slung solder at this level was when I built a Heathkit DX-60 with my dad in the early 70's.
I ran across an older Dynaco ST-70 a couple of years ago, refreshed it, and that led to this endeavor.

Edcor XPWR155 & GXE15-8-5K transformers.
Triad C-14X choke & 100uF Tenco motor run.

Stock bill of materials, with the exception of the first cap (33uF) to give me some flexibility in rectifiers.
Settled in on 470 ohm cathode resistors after measuring several options in the circuit.

recorded numbers:
nos 5AR4 & el34s. 400 B+, 30.4 V across the resistor for ~61mA plate current.
If my math is correct, which is no sure thing

nos 5AS4 & 6P3SE (6П3СE). 375 B+ & 26.8 V drop for ~54mA.
Same math caveat.

Case had a bit of "Measure once, cut twice & it's still too small" 🙂
Top plate is from SendCutSend & it worked *fine*, in spite of my less than stellar CAD skills.

All in all, for my first tube amp build ever I am very, very happy.
Enjoying Janos Starker playing the Bach cello suites as I type.

George, thank you very much for a grand design and a quality set of instructions!

Help needed!

I am trying to restore an ancient Dynaco ST120 and it actually amplifies and it puts out the power it is supposed to, but it draws way too much ilde current. One channel draws a little more than 1A and the other slightly less than 2Amps. There is no high frequency oscillation (if there is it is below 120MHz)!

For an amplifier that boast no quiescent current this seems a bit too much. So there must be a fault somewhere - but I simply can't find it. The transistors check within the specified specifications, the resistors too and I have changed the diodes and changed/checked the electrolytics. But obviously, there's something I have overlooked - does anybody have an idea where to look and/or how to overcome the problem?

Commercial available Tube/Valve buffered Line Preamplifier (OTL Headphone Amp) without Voltage Gain (= Unity Gain) Overview wanted

I am looking for an overview of commercial available tube pre- and OTL single ended headphone-amplifiers without voltage gain stage - i. e. only a cathode follower in the signal pad according one of this circuits:

OTL versions of "White Cathode Follower Power Buffers:
New Adventures in the White Cathode Follower
Simple Tube Math & White Cathode Follower Power Buffers (scroll down to the OTL versions of "White Cathode Follower Power Buffers")

Cathode Follower Circuits Overview:
https://www.pearl-hifi.com/06_Lit_Archive/14_Books_Tech_Papers/Broskie_John/1999/01_08_Oct_99.pdf
https://www.pearl-hifi.com/06_Lit_A...04/Sec_19/991_White_Follower_Optimization.pdf

Power Follower Version (Single Ended OTL)
More SE OTL & 32-Ohm Speakers
http://tubecad.com/2020/01/blog0489.htm
https://www.tubecad.com/2010/12/blog0195.htm

The only commercial available version I know in this kind is Audion's model "Silver Night Line" - go to
https://trueaudiophile.com/audion-silver-night-line-mm-phono-stage-pre-amp-new/
but it is probably a special edition because not listed on their own currently homepage - go to
http://www.audion.co.uk/pre-amps.html

OTL headphone amps like those under
https://drop.com/?origin=/buy/dark-voice-366se
and
https://theguruchoice.com/amplifiers/best-tube-headphone-amps-review/
unfortunately all with a lot of voltage gain along the signal pad and thus more or less colored sound character.
if there were such OTL headphone versions with only a cathode follower in the signal pad, that would be perfect .

In general, most clean, tight and neutral sonic character provide only a power follower topology, independent of the fact whether there are tubes or MOSFET/BjT transistors are in use.

Therefore I would like to know various brands and models of preamps in the kind of the above mentioned model from Audion.
Check out in this case also post #18 and #19 under
https://www.diyaudio.com/forums/ana...buffered-preamp-passive-volume-control-2.html
and pot #26 under
https://www.diyaudio.com/forums/everything-else/169484-wrong-op-amps-3.html
and post #85 under
https://www.diyaudio.com/forums/sol...-pure-classa-se-despite-low-idle-power-9.html
Thank you for an advice

P.S.: This URL's don't provide the wanted information:
https://www.diyaudio.com/forums/tubes-valves/58757-heretical-unity-gain-line-stage.html
https://www.diyaudio.com/forums/tubes-valves/59244-heretical-unity-gain-line-stage-ii.html

P.S. - II :
I am looking also for commercial available solid state line pre-amplifiers in this kind:
https://www.diyaudio.com/forums/pass-labs/309592-current-version-b1-buffer-preamp.html
go to post #16 under
https://www.diyaudio.com/forums/pass-labs/309592-current-version-b1-buffer-preamp-2.html#post6576099

Hi guys!

I have some questions.
How to properly set up a DSP limiter time constants (attack and release times) for RMS limiting for a 3 way passive speaker with a passive crossover network?
In tri-amp configuration with active crossover, setting up the limiter for each band isn't so difficult because there are some empirical methods for tuning attack and release times as a function of voice coils sizes. But with passive crossover isn't so trivial because all bands comes from one amplifier channel. So the goal is protecting the 3 way passive system from thermal damage with minimal audible limiter artifiacts.
The setup is:

• 2 x 10" midbass, 2.5" voice coil, 250W RMS/driver
• 1 x 8" mid, 2.5" voice coil, 250W RMS
• 2 x compression drivers, 3" voice coil, 110W RMS/driver
• The passive crossover does not contain protection.
• The systems high pass frequency is 100Hz.

I know the power distribution between the drives, simulated with continuous flat response signal and pink noise cf. 6dB. (Attached images)
The second question is the DSP has attack times from 0.3 ms up to 100 ms and release times from 2x to 32x the attack time. But these time constants seem more like peak limiting settings. Is this usable for RMS limiting in this configuration?

Thank you all for your replies!

Hi Folks,


first of all hello to everyone on the forum - a newbie here 😉


I'm tinkering with various electronics. Recently I took a challenge of repairng a decent Bluetooth headset and decided to use one of CSR modules. I managed to go through the hassle of getting it to talk to the FT232RL and after getting it to link, I made backups as usually advised in such cases.

Then I started playing around with settings for the csra64215. It came with no DAC setting so I took care of that, but while tinkering with event/button settings, I changed events for power on and power off...and now I'm in a bit of trouble.
The thing does not turn on at all, PST does not see it, no LED activity, etc.
All I did was to set Power Off and Power On events to Logical input ID 1 (which is a MFB line / PIO18).
Any idea how to make it boot again?
If I could only make it to force-start, I'd load the backup, but since I get no power/comms, I'm stuck...


Looking forward to all suggestions
Cheers
L

Hi guys....

Many people say the port can be kept anywhere it does the same job.

But does the sound waves coming from the port and the sound waves coming from driver interact with each other differently based on where the port is ??

Let's say for a 2 way Bookshelf, a port on the front, or rear, or side, or at the bottom gives exact same result ??

Or does it depend on which frequency range the speaker is playing ?? In subs the wavelengths are too huge. In two way BS, we have smaller and larger wavelengths as well.

Any inputs will be greatly appreciated.
Thanks - Audfrknaveen

Hello everybody .
I have a technical question for you.
there are many types of horns and waveguides, but which is the best technology for the diffusion of low frequency audio waves?.

Never mind.

Hi,

I got this pair of woofers for free when I did a deal about its sibling P17WJ.


I say sibling because they are more like distant cousins than brothers Except the magnet system NOTHING is the same... WH has a stamped basket, feels like a little thicker membrane and the dust cap is as soft as concrete, way stiffer than the membrane, made from thick polypropylene maybe twice as thick as the membrane, you can't push it in even one little bit. The membrane is also s lot flatter and the dustcap is probably 2" wide, yes just the dustcap. It looks like it has a 32mm voice oil as WJ but that is all I can get out of them...

The driver also a lot shorter than WJ when standing on their magnets.. makes me think about auto sound...

Anyway i was wondering if anyone have any information about them? A datasheet or measurement would be great but right now anything helps in finding out what to do with them...

Hi all,

I have a pair of Dali AX1 active speakers for two years..
I use them for TV and phone with BT..
Recently I bought a Teac TN3B turntable and connect it to my speakers aux input.
I may say it's sound is "acceptable".
But one question has been puzzling me ever since I connected them;
Is my Dali's aux input a real analog input or it goes to an ADC then volume control then DAC and finally the amplifier stage..😕
So anybody has a circuit diagram or service manual or some excact information about that ?
Thanks in advance for any kind of helps..

Hi folks,

My goal is probably naive, but thanks to the expertise of your all, let's find out.

Let's start by taking a pentode. Let's say I'm choosing the PL36 just for example, to operate it in class A SE

I drew a 1.7k loadline, which thanks for the short Patrick Turner guides is chosen by the simple formula Rl = Ua/Ia*0.9

Ua = 170V
Ug2 = 170V (seen by the graph)
Ia = 90mA
Pd = 15.3W

By the graph, we can see a symmetrical loadline with a voltage swing of 310Vpp, translating to 110Vrms, resulting in a theoretical power output of 110^2 / Rl = 7.11W

And this results in a maximum efficiency of 7.11/15.3*100 = 46.5%. So far, so good.

Of course this operation is extremely non-linear and we need to apply feedback. Are we facing a small problem here?
From practice and simulations, I think yes. If we apply too much feedback, we will be limited in swing due to the small bias point, which is -Vgk = 22V by looking at the graph.

This is where I need your advice. I had this problem with deeper CFB where the bias point, due to the tube's nature, was not negative enough, limiting the power due to limited voltage swing.. For some time I though that not all tubes are suitable for pentode operation and feedback. But is this true?

If we take a look at the PL36 situation, we can deduce from the graph the gain is currently 7. When applying feedback, what happens when it becomes, let's say, 3. It will then need a bias point of Vgk -52V.

Does the bias point shift when the tube operates is CFB, as it is a pseudo-UL mode?

LTSpice gives the power back when I decrease the load. Of course this makes a lot of sense, because we're limiting the needed voltage swing for the same amount of power output.

Thanks folks!

Not used, not soldered, stored as spareparts for my speakers.
Approx 2years old.
Price 120E+shipping.

I have a Behringer DDM4000 mixer that has a 3pin crossfader .

Iv been trying to find a fader to replace the cuurent with and have only managed to find the Infinium X1 that im struggling to fit as my current faders ribbon is hard wired to the main board of the mixer and the Infinium Fader has a Mal pulg on its ribbon that was supposed to just fit into the Mainboard.

So my question is.

Iv seen many other 3 pin cross faders that would fit nicely on the current ribbon (attached to mainboard)

but hte models are for pioneer ect.

But as they are 3 pin (with a 3pin female on the fader), is it not logical to think that they will work on my mixer. The mixers ribbon Being hardwired to the mainboard but has a Male 3 pin Terminal that would fit right into any 3 pin female fader.

Whats the rules when it comes to fader replacment.

Im hoping to buy a generic 3 pin fader and try this.

Any advice???

READY BUILT AND UNUSED NUTUBE PREAMP INCLUDING KORG NUTUBE.JUST ADD CASE AND VOLUME CONTROL. VERY SIMILAR TO PASS B1 NUTUBE AS PETE MILLETT WORKED CLOSELY WITH KORG .£100.

I been happy with my coral beta 8 and eminence beta 15a OB rig for a few years now but have often wondered about matching white woofers and then I seen these: Yamaha JA-3803 15'' woofers (sale pending) For Sale Or Trade - Canuck Audio Mart

I know jbl has white woofers and some generic Jvc, pioneer etc exist but would the ja3803 work better than the eminence?

What 15" white woofers do I want? 🙂

*found*

I am looking to buy a Pete Millett Soundcard Interface. No, the PCB kits are not available on ebay anymore. The RMS Meter seems to be obsolete too.


Looking to buy a complete device or a kit including at least PCB, front- and rearpanel and the RMS Meter display.

hello,

any good links from Russia in order to buy audio parts ?

have a nice day.

Please forgive my ignorance on this.

Can someone, anyone explain to me why this device,
LM2940CT -5.0 P+
is a positive 5 volt regulator?

Check out the pic which I hope I deleted the inline pic
that never seems to be viewable. So I attached it at the end.


It sure looks like a minus 5 volt device to me.
What am I missing?

Cheers,

Hello everyone, happy new Year!

I was thinking about bringing every LED from my amp (F4) to the front-panel.
That is, 2 from the universal PSU, 2 from the amp-channels, and (?) 2 from the speaker protection (if they light up at all) - so 2 or 3 different sources.
Brightness will be adjusted through resistors.

Will their respective brightness be the same (with the same resistors), or will they vary depending the source (PSU/OS), and I'll have to experiment until it's right?

The resistors can be with the led on the frontplate, right?

TIA
david

Check this thing out! 25mm Corundum dome, copper, underhung, rear chamber, great power response, super flat FR, 1,200hz recommended crossover!

Looks like it'll be a giant killer! I kind of want to spend $100 right now on a pair!

Peerless DA25TX00-08 1" Corundum Dome Tweeter

Hi, guys. I am new to this forum - this is my first post. And I am new to the DIY audio scene, but I am already learning a ton. I hope this post is not too long. And I hope to get your feedback.

I am looking to build a high-end DIY floorstander. I've scoured the interwebs and forums, including this one, looking for something that'll pique my interest. I've looked at the major players like Selah, Meniscus, and many others. I've come across a lot of examples on this forum, but nothing that exactly strikes me. Yes, I did use the search function and read through a lot of posts.

I am a physicist and biomedical engineer by training, but I do not have experience designing speakers. And to get to a level of skill necessary to design something that I would like both aesthetically and aurally, would take a considerable amount of time. So for now I think I am best off building an existing design, if possible.

And therein lies my conundrum. So many DIY plans are basic rectangular boxes. Nothing wrong with that to be sure, but I would like something a little more...complex and elegant, with curves and flowing lines (I am drawn to certain Sonus Faber designs, for example, but not as avante garde as the B&W Nautilus). I am an experienced woodworker with a well equipped woodworking and machine shop, and a large inventory of exotic woods and veneers. I am looking for a building challenge. I am also quite good with a soldering station, so building the crossover is no problem.

So to the specifics:
floor standing (nothing on stands)
probably passive crossovers, but I am possibly open to active
mostly for 2 channel music, but occasionally a movie or two
I listen to a lot of classical, movie scores, and classic rock
my room volume is large (ceiling vaulted to 14 ft (4.26m), but irregular in shape and open to the kitchen on one end and large-ish foyer to the side
I'd prefer not to have to pull them 6 feet into the room (3 feet is ok), so open baffles are probably not the best option
no particular price limit, but if I could stay under $4000 for everything except the boxes that would be great
would like it to be sonically as good as it can be (I realize this is vague, but I'm really trying to max out the performance as best I can)
should be pleasing to look at, form-wise (I can use exotic veneers and automotive clear coat to achieve a fine finish, but don't just want to put fancy wood on a square box)

My motivation is two-fold:
1. To build the best sounding speaker possible for my money
2. To challenge myself with building a unique and functional work of art

Note that saving money is not my goal. I really enjoy woodworking and audio, and this is a great way to marry the two together.

Are there any great designs out there that you can recommend? I am sure there is a ton of stuff out there I haven't seen. Or should I consider hiring out the design phase?

I know the part number is RVW41D1100-ND. It's out of stock everywhere, Digikey may get it on June 1; I doubt it. I know there are others available with the built-in light; don't want one of those unless I must. Can anyone refer me to another source, or does anyone have one to sell?

Also, to replace it, do I remove the amp's bottom panel or the top? I see several hex bolts that appear to allow me to remove either panel. Don't want to remove anything unnecessarily.

Any help is appreciated.

-------------------------------
UPDATE: I can also use the DP version RVW42D1100, which is in stock at Digikey.

About the rare failure of the output inductor，Worse distortion performance，need help~

About the rare failure of the output inductor， why does it significantly worsen the distortion data? I need help~

In order to verify whether the circuit is normal, I built a test circuit board. There are only a few differences between the test circuit board and the circuit diagram. The test board eliminates the power tube in the blue box, and the current amplifier stage uses only two pairs of NJW0302/0281. The rest is exactly the same.

I tried to reduce the gain to 26dB to optimize the distortion performance as much as possible, and reduce the value of the negative feedback resistor to optimize the noise performance as much as possible. After testing, this is the best performance that the temporary test circuit board can achieve:
THD+N (8Ω/50W and 80kHz bandwidth):
20Hz 0.0009%
1kHz 0.0007%
20Khz 0.0017%


But in the experiment I encountered a strange problem. The output inductor on the test board will seriously deteriorate the distortion performance. When using a 3uH vertically placed output inductor, 20Khz THD+N 0.01%! When using 1uH horizontally placed output inductor, 20KhzTHD+N 0.007%! When I short-circuit the output inductor with a piece of wire, THD+N has been amazingly improved~It's unbelievable...

I have checked the square wave step response of the amplifier with a 100Mhz oscilloscope. There is no obvious overshoot or damped oscillation. No obvious parasitic oscillation was found on the sine wave.
I checked the materials of the two inductors and I confirmed that they are copper.
I checked the Zobel resistor and confirmed that it is not damaged.
The power transformer is placed far away, it should not cause electromagnetic interference, and I have tried to change the orientation of the test circuit board, but it has no effect.

I can't find the cause of the problem~~

Friends, can anyone tell me how to solve this problem? What caused it?

thank you all

is this an ok way to solder? i filled the tiny holes with solder basically turning them in to tabs. what is the worst case scenario should i expect in the long run? tia edit am i the only one who cant see the picture i just uploaded?

Jeff,

I am recapping a Pilot 232. Would you recommend a particular brand or type of coupling cap for this EL84 tube amp?

Bruce

I repaired the PS of this amp - 8x IRF3205 and A1266 driver pairs with BD140 units. Amp powers and plays, but seems to drop into protect at very high gain/output. 1-ohm load, rated at 1000w at 1ohm. The amp draws about 70A from the bench and then falls into and then back out of protect. Thats probably only about 500w if that. Just before protect engages, the amp starts to clip.

Is this normal or is there something going on? I figured 1000w true (if it IS true) would pull over 100A from my bench.

Thank you

Jeff,

I am recapping a Pilot 232. Would you recommend a particular brand or type of coupling cap for this EL84 tube amp?

Bruce

Hi, I am in the process of building an F5. I just tested the power section and my results were odd. First problem. When it is plugged in it is on. The on off switch has no effect either way. I am almost certain I wired the PEM wrong. Second problem, one channel produces 26.3 volts. The other produces one. So, is it the switch problem or maybe a bad solder? Any other ideas?

I am not an electronics pro. I have build ACAs and a bottle head quickie successfully in the past. Help is welcome.

Thanks!

Okay, What I need is a good diagram or photo of how to wire the PEM. I have a double fuse PEM that came with the hardware kit for the deluxe chassis from the DIY audio store.

Hi !

I'm a big fan of extreme dynamic loudspeaker like Altec Lansing Pro VOTT and 409-8C and duplex.

I quit the pro audio world since 20 years to go with boring home loudspeaker without never finding again the same details and dynamic of sound.

Now I'm ready for new DIY project and I want to know what's the best bang for the buck 2021 audiophile quality HORN and 15 or 18" woofer brands, to reach the sound of my sweet childhood pro audio drivers....

Thanks in advance ! 😀

nicK

Greetings,
I'm new here but have been using a pair of NC400/SMPS600-V3 mono-amps for a few years. I'd appreciate any comment or help to troubleshoot an issue with one of the amps.
The amps have been plugged in but powered off for about a year. Upon turning on a few days ago, one amp did not respond. The fuse is not open. The caps, coils, and visible components appear to be intact and good shape. However, the row of LEDs in the middle of the NC400 module flashes red at every 2 seconds.
How do I find the error? Will I need to replace either the Amp or the PS module? I've written to Hypex but haven't receive any reply yet.



Thanks in advance for your time and help.

Hello, and thanks for stopping by.

Although I have built my own guitars, tube amps, FX pedals, and work as an Engineering R & D tech at Zoll Medical, this particular facet of things is unchartered territory for me. I'll just try to dive in and see where this goes.

Having been a professional guitarist that dreamed about having Cello/violin like melody expression I build a guitar with no frets and it is to be played with only an Ebow.(electronic bow) So, for frequency range, that means my lowest note is around 80 Hz and the Ebow with the pickup I use will generate up to 10-12Khz, which, is unusual for a normal guitar which usually uses speakers that roll off around 5-6K at the most.

Considering this expected range, I thought it would be a reasonable idea to use a high power full range speaker, could be 8", 10" or 12". I don't think I need to go 12", for this application an 8" full range speaker may be fine. I'd like this system to be loud enough to work in small to medium rooms, and I'd like to get "the sound" on stage so, a sort of fully produced sound on stage to be stereo mic'd and act as the stage monitor as well. This rig will be in stereo with stereo effects so, I'm looking at 2 cabinets powered with a 2 channel Crown or QSC power amp, probably 300 watts would do.

Just to clarify, the Ebow/fretless "guitar" goes into a DI/Neve mic pre/Kurzweil Rumour 2 channel reverb-ambience processor then finally out to a 2 channel power amp and into the 2 cabinets, each with a full range speaker.

This is what I picture as far as what I know in life about sound so far plus, I can look to keep it fairly compact and maybe affordable (maybe).

So all of this seems to live somewhere in the middle of "Hi-Fi, live sound and guitar amp". Least of all, guitar amp - I have my Fenders and Marshall for that. I will also be using IR pedals to emulate different wooden violin/cello body resonances and such so, my choices in speakers/cabs may want to lean toward at least a little "flatter responce". It certainly doesn't need to be super accurate or flat, just not super colored or have high distortion like a guitar amp. Like a little good sounding stereo PA system for the stage. If I ever need huge volume, I'll mic up the two cabs.

So I've been looking at various full range speakers by Eminence, Celestion and a few others that I cant even remember, and wondering if I choose a speaker then match a fitting cabinet, or the other way around. I probably can't afford to custom build speaker cabs based on the speakers electrical/mechanical characteristics so, I'll be trying to find a decent match of speaker and cabinet that is reasonably affordable, just for starters.

So, in your opinion, considering my particular application, how would you recommend I look at putting this together? I'd surely be interested in your ideas. It doesn't have to be perfect to start, I just need a reasonable start and take it from there as I learn the elements, and experience the issues.

Thanks so much for reading through this, I know it was a bit loaded post
Best,
Phil Donovan

In the last few months, I have been considering building either a La Scala, Belle or other similar horn based speaker. I would be open to other horn speakers builts/designs that forum members think sound better than the La Scala or Bella speakers. I was wondering if any forum members would share their speaker builds with me. This is the first time I have tried to build a horn type speaker and would appreciate any help or guidance. Thank You Greg Edwards

PS- Anyone in the Missouri or Northern Arkansas that build speakers?

From what I gather these modules are meant for balanced input, and using unbalanced input (by connecting RCA ground to pin 3?) will provide half the gain?

What would be the best way of using these with a RCA input?
Hopefully without needing an additional board like the Ghent RTX module.