Hi everybody,

First post...I did try looking at other posts but couldn't find an answer.

A friend has asked me to look into some solutions to his bar. Even though my experience extends to plugging a guitar into an amplifier, I said I would give it a go just to see what was possible.

The Concept: Multiple inputs (TV, Spotify, Microphone etc) into one "mixer" and distributed to 3 separate rooms each with it's own set of stereo speakers. Every channel being completely interchangeable. The rooms are not massive so large speaker cabs are not necessary.

I didn't think I could find a mixer that does this but the good folks at Thomann pointed me in the right direction to this.

DAP-Audio iMix 7.3

MANUAL

Looks like all I could ask for except, I'm a little confused as to what goes between the iMix and speakers.

Presumably I would need an amplifier per speaker set or could I just hook up the RCAs to the bare wire speakers? Does this sort of mixer amplify considering the small size of the rooms, is additional amplification needed?

Thanks for any help you can give.

Hello DIYers

I just registered since I'm new to HiFi DIY (I´ve worked with large PA systems In clubs for several years, and built horn subs In the past).

I recently got into the idea of making a large 2-way for both HiFi and studio use, so I've built a 30L reflex box for a 8" woofer and large dome tweeter, for a 2000 hz crossover.

Today I ordered the parts, so I'm very excited to put it together to see how It sounds. They are as follows:

Dayton DS215-8 - 8" Mid/Woofer
Dayton Audio - DS215-8 8" Designer Series Woofer Speaker 8 Ohm

Monacor DT-300 - 1.2" Dome Tweeter
MONACOR: DT-300

Dayton XO2W-2K - 2000 Hz 2-Way Crossover
Dayton Audio - XO2W-2K 2-Way Crossover 2,000 Hz

They go into a 30L box with 2 ports of 5 cm circumference and 10 cm depth, i havent calculated the tuning, but I believe it to be around 40-50 Hz, correct me If I'm wrong.

I plan on driving the speakers with a Cambridge A500 amp:
Cambridge Audio A500 - Manual - Stereo Integrated Amplifier - HiFi Engine


My questions to you guys is: Will this work well? Do I need to dampen the tweeter due to It's higher sensitivity? What Is your overall opinion on this setup for a beginner audiophile just getting into DIY speakerbuilding?

All feedback Is greatly appreciated!
Thank you very much, I look forward to learn all that I can from the masters of this forum 🙂

a

Hello,

can anybody help with information of the Balanced Input Stage of this amplifier. Like to convert an older model from SE to balanced input.

In the VTL book is only the SE version.

Thank you,

Reinhard

The global class D audio amplifier market was valued at $2.49 billion in 2018, and is projected to reach $4.92 billion by 2026, registering a CAGR of 8.4% from 2019 to 2026. Class D audio amplifier is an electronic device, which multiplies the amplitude of the sound signals. Amplified sound signals can reach to the higher level and hence are suitable for loudspeakers or driving subwoofers. It offers varied advantages such as heat dissipation, energy efficiency, and space efficiency. It is an important consideration while designing portable music devices.

Class D Audio Amplifier Market Size, Share and Analysis | 2026

SOLD!
Up for sale is a slightly used 800VA power transformer from Talema.

Model: 55207-P1S2

Primary: 230V

Secondary: 2x 45V @ 8.889A

Size: 165mm x 65mm

Weight: 5.3 kg

Shipping worldwide.

Price: 60 EUR

I am also curious about your findings.
I can get a mosfet power audio amplifier. A Ohio PLX 2500.

But is it also possible to use these types of amplifiers as a power amplifier for your guitar setup in combination with a guitar preamp? For example Triaxis.
Or is this going to sound like sh*t?
I was wondering if this was possible as I could buy this cheaply. Perhaps still possible to make some tweaks. But I don't know if these amps are much different from the SS amps for guitars.
Of course the best combination is a triaxis with a mesa 2:90. But the budget is currently not sufficient there.
I was looking at an SS power amp to complement my 19 "rack. And by chance I came across the aforementioned amplifier. But I had no idea if this could just be combined with a guitar preamp.

Are these resistors 0.02 ohms or does anyone know the value ?

The resistors I’m referring to are the black resistors

Hi. I'm not doing just electronics, while stuck at home got a request from my love one 'the real boss' 😉 A place to start new plants and vegetables for our upcoming garden. Using some left over parts in my garage, I put together this...
Now I can return to my projects 😉
SB

Hi I'm new here and need some advice.

I have an Alpine MRV-M500 amp driving a JL Audio 10W3 sub. It's been fine for a long time but it started playing up a week ago.

Under moderate to heavy load the amp would cut out intermittently for a few seconds then come back on again. I'm not sure if it went into protection mode as it only has the one blue led, but it was powered the whole time.

I had it on the bench and noticed it draws 1.2A when switched on without any load on it, so I thought one of the output FETS might be faulty. I replaced all 4 plus the two driver IC's. Hooked it up again and it was working fine for around an hour until it cut out again. It now seems it's temperature related as it will start working again after half an hour or so.

Does anyone have any ideas what could be causing this? I'm thinking possibly thermal protection kicking in for no reason. The amp is barely getting warm up until it cuts out.

I can't find the circuit diagram for it anywhere which would make things a lot easier.

6sc7 shared cathode guitar preamp questions

Thanks in part to help from this forum, I've built or repaired about a dozen guitar amps over the past year. Finally hit a new one that has left me with some questions.

I bought a cheap, broken UPX-003a phono preamp thinking I'd turn it into a guitar preamp to get some of my smaller amps into high gain distortion. It uses a 6sc7 shared cathode dual triode, which I found was used in the Fender 5c2 Princeton, so I based my design on the 5c2 preamp (up through the volume pot but not including the tone control so far). The only significant difference is my power supply provides only 170V, so thus far I'm sticking with the original 68k and 47k plate resistors from the UPX-003a instead of the 250k resistors from the 5c2 — may adjust those values later, but for now I figure these will work.

So far so good, I have a little 5c2-ish preamp driving my Champ into glorious tube overdrive. Now for the questions:

1) Despite the relatively tame (compared to 12ax7) triodes running at lowish plate voltage, this thing produces a lot of gain! Is there any reason to worry about the signal level going into my amps? How much AC voltage can a 12ax7 grid handle?

2) The 5c2 has a fixed 250k / 75k voltage divider between the two 6sc7 stages. I thought I'd give myself a gain control, and installed a 500k pot there instead. But, if I turn that pot up beyond about 25%, the preamp goes into some kind of wild oscillation and starts producing periodic chirping noises. I'm guessing this has to do with the shared cathode, though it is bypassed. But I'm not sure how to think about how that works. Any ideas about what might be going on, or how to diagnose?

I'm attaching a quick drawing of exactly what I have.

For those who need help with repairs, please use your (unused) sig line to list the equipment you have, including the 12v power supply (or other supplies), multimeter, note whether you have a scope or not (scope make/model if you have one), even the soldering iron, hot air station...

All of this helps those who can help to determine what you can and cannot do without having to ask what equipment you have.

If you have a piece of test equipment go down (like your scope), make a note as to whether it's going to be repaired or replaced.

In Dean Martin's song "The Triche Trache", Dean refers to a musical instrument called a "Triche Trache". What is it?

Bobby Dipole

If you have two different drivers in series, and one is ~4-6dB more sensitive, can you compensate without effecting the other driver?

In my particular case, the two drivers are part of a 1st order low pass filter. The more sensitive driver is 3.7 Ohm, and the less sensitive is 3.8 Ohm.

Thanks.

Hello everyone!


I'm trying to get back into the swing of things in the tube world. When I was a teenager, I got interested in tubes and DIY audio in general, built a little tube preamplifier kit, and then promptly got hit with the real world when I moved out of my parents house and enlisted the USMC. Been a free man again for a while now, finished my degree, and got a real job, so now I want to get back into the DIY audio world. My hearing actually super damaged from crewing on the CH53E, but I've always wanted to design and build a tube amp; just copying someone else schematic won't itch the spot.



Been spending my time reading "Valve Amplifers" - 3rd edition (bought it when I was a teenager), and playing around with TubeCAD and SE Amp CAD, on a WinXP virtual box, as well as reading whatever I can find online. The following circuit is what I've come up with: Imgur: The magic of the Internet


The outputs from TubeCAD and SE Amp CAD: Imgur: The magic of the Internet


Some notes -

• 6C33C-B (yes I know the cyrillic is actually different letters, before someone points that out), was chosen as the output tube simply because I really like the way they look.
• 6J5 was chosen as the driver because, again, I like the look of the metal tubes, and I think, from what I seen in TubeCAD, they will have no issues driving the 6C33C-B
• The 6J5 grids are tied together with a 1 mega ohm resistor
• OPT is TTG-6C33CS
• SE Amp CAD says this isn't going to be a low distortion amp, but I'm going in knowing this. If it is really bad, maybe I can add some negative feedback? - My hearing probably isn't good enough anymore to actually tell.
• Intended speaker will be Fostex full range drivers (not sure which ones yet)

I know from my job, that models and simulations never translate 100% into the real world, but how far off base do you all think I am with the design so far?


Any glaring flaws that will make it blow up in my face at power on?


My goal is to get the circuit as good as possible before I buy parts to build a single channel to play around with.


Also, I'm a Forester for the USFS nowadays, ask me a tree related question!

Remind me to keep a credit card taped to my computer screen so that I can jump on stuff a little faster from now on. 😉

Hello!

I'v been signing in a choir for +10 years. With the pandemic, no choir can rehearse right now. While many things can be safely accomplished at a 6 feet distance, signing in a choir requires closeness and most certainly increases the risk of spitting the virus further.*

Software for online rehearsal do exist, and we are trying them, but they all have latency problems (of course) and are very hard to use for older and/or non-tech people.

I'd like to come up with a solution that will allow a choir to rehearse in the same location but at a safe distance from each other. If money wasn't an issue, the setup would look like something you would see in a studio, extended to let's say 50 people : 50 microphones, 50 pairs of headphone, a 50+ inputs mixer, a 50+ output headphone mixer, 50 microphone stands, etc.

My perfect solution has a few criteria, but I'll consider anything in between.

1. Somewhat affordable
2. Easy to build for someone with experience with audio, computers, technology, soldering
3. Easy to install and operate at each rehearsal

A few considerations / ideas :

Microphone and headphones

Best case scenario : using the most basic smartphone headset. Yeah, I know, they sound bad. But if you look for "virtual choir" videos that were made recently, they are all made with that type of microphone, and they sound more than OK for this purpose. The target audience here is not audiophiles.

Mixer

I think this is the most complicated part. I know that the signal from the headset microphone isn't compatible with a mixer, and that it needs a different voltage. Also, it's a choir, so signers are supposed to be their own potentiometer. So there is no need for a volume adjustment feature. Is there a product out there that can achieve that? If not, I can solder. I've seen many DIY passive mixer tutorials out there. Would something like that be feasible, if combine with an amplifier?

Long cable

There has to be a long cable between each signer and the mixer. Some signers are gonna be at 10 feet, other at 50 ft and so on. XLR cable a expansive, and my guess is that they might be overkill anyway if the carry a signal from a crappy headset. I've worked a lot with network cable in a previous life. Is it crazy to use good'ol cat 5 cable for this purpose? I'ts cheap and available everywhere. I would then create a physical femake RJ45 to female TRRS 3.5mm adapter for the signer end, and another kind of adapter for the mixer side.

My setup so far:

1. Normal cheap headset (for each signer)

2. Custom box adapter (for each signer) - TRRS input, potentiometer for the headphone volume, battery for the microphone (a diy version of that?), and each 4 wires (L, R, Ground, Mic) to a pair of wires in the ethernet jack.

3. Regular ethernet cable, various length (for each signer)

4. Custom mixer - Ethernet "inputs", all microphones inputs combined (with resistances?) to an XLR output. All L/R outputs combined to XLR inputs.

5. Some sort of amplifier or regular mixer connected to the custom mixer to amplify the microphone and send it back to the headphones.

So, am I completely crazy? I know it's a very long shot. I'd like to start with a prototype for my choir, and try it with 4 or 8 people. If it works, I'll look into a way to expand it and to put it in the hand of other choirs.

I'm not a audio / electronics pro. Just a hobbyist 🙂

Thanks for your help!

Felix

*For many experts, normally signing in a choir will not be possible before 2021 : Choirs may have to remain silent long after society reopens - Portland Press Herald

First post after browsing these forums for a year and playing with various ebay and ali inexpensive amps. I must not be an audiophile, because I find even the cheap amps sound quite good. I have a full house, multi-room audio system using Apple Airport Express, feeding small tube pre-amps and class D amps (TDA7498/E, TPA3116D2 (dual and single), TPA3255), driving various speakers from PSB, Paradigm, Energy, etc.

My question is regarding the ICE125ASX2 module setup in BTL to drive a continuous 200w into 8 ohms, to drive my collection of Energy 22's. I could have sworn I searched ebay/ali for a BTL icepower based finished amp to no avail. Then I came across this today:

BTL ICEPOWER Power amplifier HIFI Stereo ICE125ASX2 Digital power amplifier 250W | eBay

Definitely a price jump over my typical sub $100 amps. But I do want to be nice to my vintage Energy speakers 🙂

Thoughts? Does this look like a decently constructed amp?

Are there other icepower amps, with similar 200w continuous low distortion specs, around the same price range?

I'm not savvy enough (yet) for a diy build, without some hand holding. Hence why I'm looking for a finished product.

This isn't DIY however it is Class D.

My Sherbourn 5/1500A is behaving oddly, and according to the tech at Emotiva it needs 5 new relays and capacitors replaced. This is evidently a known problem. It randomly sputters & cuts out on various channels. When bench testing I couldn't get it to fail. When using another amp (2 channel) in its place all the inputs & speakers worked fine. I use this amp for height channels in a 7.4.1 system.

I was pretty excited about building a pair of IcePower 200ASC/200AC amps with Ghent cases. Then I found this amp;

MUSYSIC Professional 4-Channels 2x9600 Watts D-Class 1U Power Amplifier MU-D9600 | eBay

If the specs can be believed (300 Watts x 4 at 8 ohms) and a price of $299 I couldn't build something or repair my Sherbourn for this price.

Has anyone had any experience with this device or this company?

Hello guys,

I think that this is my first post here on diyAudio, so first I would like to say hello to all ladies and gentleman here

Just received my amp, and it is really in mint state... not a single scratch even under close inspection and upon opening the cover I have seen the well known "millennium spider net" inside... long time not used amp

But it suffers from strange issue I haven't seen until now... after powering on, there is some period of up to 15 seconds seconds when it is quiet (O know that HK use muting circuit), but when amp starts, the loud single pop (bang) came from the speakers (like champagne opening) and it is loud even the volume is at 0 and then some sort of irregular noise, more like hum can be hear for some time; approximately 15-30 seconds. After that everything is OK and it plays very nice. If I turn it off and on immediately I don't hear this. If I turn of for some short time it happens again. The speakers switch when switching from A to B and A+B or back produce the same champagne opening sound at every position change, but tape monitor switch can produce some noise as well. So it could be the switch issue, but why then this occurs just after turning on the amp and after some short period it stops... or maybe I don't hear this while playing the music 😕😕

Anybody have had similar issue or experience with HK?

Any help is welcome

Thanks,
Nikola

A common way to do a gain stage is to combine a common cathode circuit with a cathode follower. The common cathode block may be a triode strapped pentode. Something like this:




Since the cathode of the CF is close to the plate voltage of the pentode it is temping to connect the screen grid to the CF’s cathode. This will result in feedback from the CF to the input stage.




This will at least do two things: reduce the output impedance and linearize the CF.

Here are some measurements of the two circuits. Blue curve is without and red curve with g2-feedback. The output impedance is 690 ohm for the plain CF and 280 ohm with g2-feedback.
Most of the distortion belongs to the common cathode block, so it might be worthwhile to play with the working point for that stage.




Jan E Veiset

any idea of a small physical size neo tweeter with large waveguide for a diy coax project?

Hi all.

Searched for this issue, found nothing but forgive me if it's well known...

My Pro-Ject Debut Carbon DC (maybe 3 years-old) motor will often make a kind of 'toc toc toc toc...' fairly loud noise when started 'cold' (i.e. room temperature after being off for several hours/days). Seems noise has same frequency as motor rotation, once per turn I believe. Belt on or off, no difference. Moving motor on its suspension has no effect.

Curious thing is that after 10-20 minutes, the noise disappears and deck operates silently for as long as it is on afterwards.

Only mods are acrylic platter and Ortofon 2M Blue stylus in 2M Red cartridge, so nothing relevant here.

Anybody else? Does motor lubrication falls to bottom of motor and needs to be re-spread by heat? Cheers!

--Christian

Hi,

I came across some glass fuses with color coding rings on it. What value could they be?

Regards, Gerrit

I wish to express my admiration for the Threshold Stasis 3 in retrospect that is.
Although its modest powerspecification of two times 100 Watts RMS it has a powersupply that occupies 2/3 of the available space inside, its front is solid as the rest and above all beautifull sculpted in a three layer configuration.
All the hardware is of exceptional quality IMO and still looks very fine and new.
It can power my Infinity QLS's fullrange and sounds great also.
The only thing as can be seen from the pics is that the one kilowatt transformer is just too heavy for the bottomplate it seems.
The only other piece of audio gear that could match its fit and finish in the beginning of the eighties (1981 is my Stasis 3) is the Levinson ML-2.
Thank you Threshold Inc.
https://www.diyaudio.com/forums/attachment.php?attachmentid=844371&stc=1&d=1589566610
https://www.diyaudio.com/forums/attachment.php?attachmentid=844372&stc=1
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I have been thinking for a while about a small and "simple" synergy horn design and I came up with the following.
A 3D printed waveguide/phaseplug/reflex port device that fits in a 12" by 12" by 9" ply box.



The design process started with making a waveguide that sits on the HF exit of the BMS 6.5" Coax and naturally extends its flare.
The HF exit has a kind of an exponential metal flare where the very bottom of the throat has a diameter of about 1cm and mouth has a diameter of 3cm.





In Hornresp (Thanks for the great tool David!) I split the horn in 4 segments - the first being the HF exit of the BMS and the mid tap being between the 2nd and 3rd segment, so that I can play around with the distance from the throat of the horn.



Having in mind that I should keep the taps 1/4 wavelength (the BMS has a 1300Hz recommended crossover) I placed the taps 6cm from the horn throat.



After playing around with the length/area of the segments while trying to keep it under 12" in diameter I came up with the following design..

In order to extend the LF I decided to let the back side of the paper membrane be open to the rest of the ported box.



The REW measurement consists of the raw response of both HF and LF, with a 12db LR HP filter at 1200Hz on the HF. The taps/ports act like a natural bandpass/lowpass so I decided not to lowpass the LF.



The setup is bi-amped running through a dsp with FIR filters and with a bit of messing around I flattened the magnitude response as well as the phase to a certain degree.



It's a pretty nice sounding speaker!

Now the issues:
1) There are 2 nasty high Q dips at 6340hz and 7800hz.
I tried covering the midrange taps with tape and measuring and yes, the dips are caused by the taps...

2) When playing at high level the midrange taps reach critical air velocity and start distorting... I was kind of aware that it will happen 😀

Has anybody tried a similar design?
Or successfully managed to hide their midrange taps at such a high crossover frequency?

The current design is conical with one expansion flare at the horn mouth.
Any clever horn types that could be more suitable for the purpose?

I don't find much information about horns with rapid expansion...
Most of the information I stumble upon is horns that are very long compared to their throat circumference...

Let me know what you think!
Stan

Hello!
When ordering a ll1679PP transformer I was asked whether I want a PP or PPZ (parafeed zero gap) transformer.
No specification for a PPZ is available. I have only found out that they have twice induction comparing to a PP and no air gap.
Does anybody have experience in using such PPZ OT? What would be the best for KT88 based PP?

Greetings from lockdown in Wales, how are we all doing?

I've been keeping busy and decided to build a new sub for my surround sound in the living room.

Now I am no magician and can't just cast a spell to remember why I bought two lab-12 drivers 7-8 years ago for subwoofers that were definitely not a labhorn... but I did. I have been using one of them in a 100l reflex in the lounge for a while.

Knowing I had the spare driver knocking about gathering dust I decided I would try to build an isobaric box and reduce the volume.

The original 100l reflex (as Suggested byt user THINK on here) had 4 65mm diameter ports. I got large corks I could use to plug them up. Use 4 ports for 32Hz tuning with 3db bump at 40Hz, 3 ports open for 28Hz tuning with a little rise near 35Hz. 2 ports for 23Hz tuning that starts to dip then roll off near 30Hz. 1 port for a long slow roll off at 17Hz tuning. Most of the time I used it with 2 ports for home theater.



It was big and cuboid and didn't really fit anywhere nicely in the new house.

I didn't do a lot of reading before building the new one but I did read this:

Isobaric subwoofer box design - Advantages and disadvantages

After reading that and the comments I was expecting this box to be as "loud" or 3db "quieter" than my current sub. The disadvantages didn't really apply because the amp is fine at 3 Ohms for two Labs in parallel, I already owned the drivers, and I would build a thick single baffle for an easy build.

I modelled it in WinISD (Pro Alpha 0.5a7, I like being able to choose port length and have it adjust tuning, is it really flawed?) and compared to the old box' transfer function magnitude.


Red, yellow, green are three of the 100l tunings, purple is the isobaric.

As you can see from that, I'm getting a slight increase in extension from a box that's 67L net, or 2/3 the size. I'm putting it into an alcove on the side of the chimney breast and it's sized to suit, including some areas around the sides and back to hide wiring and internet hubs that sort of junk. It's also a shelf, so far no rattling items hah!




I'm very pleased with the build, it was going perfectly until I had a big woops with the router on one of the counterbores on the removable baffle 🙁 Not sure what to do about the squashed pics there.

Ok so now for the confusion. this sub is louder! I use a microphone to set the levels on my surround sound so they're all similar in my spot on the sofa 😀
and when I wired this up and switched it on for the first time I had to dial in 6db of attenuation to get it to the same level as the old sub.

To make me more confused I then looked at the modelled SPL in WinISD and it's showing it should be at least 6dB quieter than the old subwoofer. what the hell is going on? how does WinISD model isobaric drivers? I can't see an option for series or parallel.


Ok, help me understand this?
The impedance being half effectively means it's drawing more power from the amp if I haven't touched the volume knob? as it happens it has an indented reference level on the knob and I set the attenuation on the receiver.

If anyone fancies taking a stab at helping me get to grips with this I would appreciate it 🙂 I presume I'm just ignorant of some pretty important things happening with the science of it all.

Thanks,

Robyn

Hi !


I was recently given a DUAL CT 7030 FM/MW/LW radio receiver to repair.



I do have some knowledge on electronics, but never worked on any radio receiver. This was my 1st try, hopping I could learn something. I'll try to explain the problem I'm facing, and all the steps that took me there ... most likely, I'll describe a lot of incorrect things, but like I said, I'm trying to learn 🙂


When I got the receiver, everything powered up ok. Only static noise on FM band, and absolutely silence on everything else.


I was able to find the schematics, that I'll include later on, as well as the alignment tables. All power rails were ok, so had to look somewhere else. Probing on TP1 , I realised that the voltage was always above 9V, no matter the frequency I tried to receive on FM/MW/LW. At first, I thought it could have something to do with the PLL (IC601 SAA1057), changed the PLL, XTAL and in-series capacitor, but didn't solved the problem. So, I decided to isolate the FM from MW/LW tuning stage, and I started to have some voltage change (VCO) on MW/LW, but not on FM.


After some more poking around, I found out that the dual varicap (D4 KV1310) was bad, so I replaced it. Also tested the dual gate mosfet (Q1 2SK74) outside the circuit, and the Vgs was happening at random values (might be my testing skills ... don't know), but I also replaced it. After all those changes, there was some "life". I was now able to tune some FM stations, and even in stereo ... but, the auto scan feature couldn't pick a single station. That was when I realised that someone, before me, was already messing around with a lot of the variable tuning coils and capacitors 🙁


I never aligned a receiver before, I don't even have the right equipment ... or the right knowledge ... unfortunately. Even so, I tried something: tuned to a noise free station, and varying T102, I got the voltage between TP2 and TP3 to a value close to 0V. At this time, the auto scan feature, started to work 🙂 Just a small (big) problem. All the stations, I can only tune 100KHz above, this is, if the station is 98MHz, I can only tune it in 98.1MHz ... and this is all over the scale.


I was also poking around with L10 (it is actually L16 on the schematic, the actual L10 can't even be changed!! ... the schematic is very imprecise), to be able to set the VCO voltage coming from the PLL. But there is only one component to adjust it, and if I set the upper value, the lower value drifts as well.
Example:

If I set: 108MHz to 8.50V, I get 87.5MHz at 2.34V.
If I set 87.5MHz at 2.50V, I get 108MHz at 9.83V
(please see the alignment table in attach)


.. I ended up shooting for the middle: 9.17V at 108MHz and 2.37V at 87.5MHz ... but even so, this doesn't seem to make any difference, as the tuning frequency is always 100KHz above 😕


I have a 4 channel 100MHz digital scope, and a 100MHz function generator. My function generator, can provide a sweep frequency, and FM modulation signal up to 30MHz (I think). While in sweep frequency I can also trigger a square wave, with variable duty cycle on the Sync output.


I wanted to tune the FM discriminator (S curve). To do this, I will have to generate a center frequency of 10.7MHz, with a span of 75KHz ... right ? But where do I inject it ? on the 75ohm aerial input ? and with what amplitude ? (the minimum for my function generator is 2mVpp). On the scope side, do I have to put it in X-Y mode, with the Y channel connected to TP4 ? ... but, shouldn't I have to connect a ramp signal on the X channel ? (I can only have a square wave, not ramp signal/sawtooth signal, coming from my function generator).


As for the MW part of the receiver, well, I think I'll need to replace the IC201 (LA1245), as I have signal coming in pin 3 ... "something" getting out of pin 7, passing trough the passband filter T203, and going inside pin 9, but nothing coming out of pin 13. But, I'm not too worry about this, as where I live, there aren't any stations to be received on this band. Maybe later, I'll take care of that.


Can anyone help with the tuning of the FM discriminator ? and what can I do about the offset on the tuning frequency ? Any help is truly appreciated 😀


Link with schematic and alignment tables:

files

NOTE: On the schematic, I circled at green the components I have changed and at red is show the actual place of L8. And on the board silkscreen, there is also a mismatch between L7 and L8, but for circuit sake, just consider the placement of L8 show in red

Afternoon all,

I'm embarking on a lockdown project to convert an old Marshall solid state amp into a Vibrochamp style valve combo.

I've made a few changes to the circuit. Partly to tailor the tone to my tastes, partly as an attempt to improve some elements of the circuit which look a little dated by modern standards, but mainly to suit the spare parts I have to hand.

I was hoping for some advice on the layout of the amp. I've stuck pretty closely to the original component layout, so I would hope not to run into any major problems. Does anything about my layout leap out as problematic, or just plain wrong?

I'm particularly interested in keeping the noise as low as possible, to which end I've added extra filtering in power supply, and a further extra stage on the preamp valve.

Chassis space is tight, but I think I have all the major components organised logically, with the exception of the OT.
The logical place would seem to be in line with the power transformer and valves but 90 degrees off axis, at the opposite end of the chassis. Is it a good idea to have the OT so close to the input valve?
Alternatively, I could bolt it to the cabinet somewhere, but that would necessitate longer leads than ideal.

Finally, I'm using a bus bar for the zero volt signal return. What is the best place to connect this to the chassis?

Thanks for looking,

Matt.


Ps. Not shown on the diagram, AC enters on the back panel by the PT, On/Off and standby switches on the front panel opposite, with a solid state bridge rectifier mounted in between, in line with the reservior caps.

Greetings!


So I have this parametric eq or bandpass type circuit. I am quite happy with the sound, but i would like to change one thing. I would like it to function in a way, so that when the potentiometer is set to zero (maximum value) sound comes trough unaffected ( no cut or boost). But when you start to turn the pot clockwise, you start to get a boost at the desired frequency. I would like a boost at 2 - 6 khz(somewhere in there) with a low to medium Q. (not so critical for my application).



I was wondering if any of you skilled gentlemen could help me make the modifications, so the circuit would suffice my needs. If you have some other circuit in mind that would do this i am open to suggestions.


Many thanks in advance.

Hello. Do you know the difference between these two ways of applying feedback from the OT?

What would be the best method ?
Does one allow better PI performance than the other ?
Which one is lower noise ?


I am grateful for your help.

It is commonly recommended that if employing series connection of filaments in the amp design (2 * 6.3 V = 12.6 V transformer winding), that the tubes be matched and always replaced as a pair.

Does this also hold true for regulated DC filament supplies, whether those supplies be constant current or constant voltage?

Hello,

I have this amp TPA3116 Subwoofer Amplifier Board 2.1 Channel HIFI Bluetooth AMP 2*50W+100W | eBay powered by a very cheap 20 euro 24V laptop power supply (switchmode with ground) would a more expensive psu be worth it to eliminate noise?

Hi,
I would like to find a FISHER 55-A tube monoblock amplifier to make a stereo set,does any of you know or have one for sale?

Best regards
Miguel

Hello all,

I am a student considering a very modest 2-way speaker system using a 3" cone tweeter crossed over first order at 6,880 hz (2.2 mf capacitor @ 10.5 ohms) along with an 8" stock mid bass unit.... Fs 56 hz, Vas 25 l, Qts 0.8, Xmax 2 mm.

Case: The above configuration is intended to be used in a sealed box with Vb 40 litres (quite larger than its Vas and hence lightly loaded).

WinIsd shows the excursion limits will be reach with just 10 watts with reference to the band 60 hz and below.

Questions -

1. If i drive it past Xmax (say at 20 watts) long term and regularly, would its spider suffer fatigue and end up getting irreversibly looser?

2. Also would that effectively raise the Vas significantly, including effect irreversible changes in other T/S parameters?

3. If Vas does increase, then it would also take the system Qtc higher. Is it likely to happen?

4. In case of 3 above, would it have any effect on the excursion limited power handling 60 hz and below?

I hope to gain some guidance through the inputs by insightful designers here!

Thanks and regards,
Sujat

I have built Rod Elliot’s simple preamp supply with bits I had on hand. I will eventually be building an active crossover for the home system and am having a go at the basic building blocks for experience.

I have followed the schematic on figure 2. on his wonderful page: Power Supply for Preamps except I didn’t have 100nf ceramic capacitors and so used 1F ceramics.

With 2.2k resistors across the outputs world as to draw a ~5mA constant current and discharge the caps when off, I probed across the 10uf output capacitor (with a ground spring on the probe) and got much more noise than I was expecting.

The frequency of the spikes in the photo are at almost exactly 100Hz but I am baffled as to what might cause them, I was expecting much better noise performance?

Is the bridge rectifier?

So I am a newbie looking to experiment with an open-baffle lower-frequency speaker. The target frequencies are 45-200 Hz; my AV Receiver thinks this is a subwoofer while DIY forums don't think so 🙂

My question is specifically about this driver:

Lautsprecher Technik - Dynavox DY200-9A 8 inch 8 Ohm Woofer Speakers

It is very attractive on price and it is known to be used in open-baffle designs CT 306

So I wanted to get a couple of these and try to do what I could; worst case, I write the expenses off to experience.

But is the driver itself any good? I understand it's nothing hi-end 🙂 but is it workable, does it sound nice?

While the Visaton WS 25E is bigger and probably better, it's harder to write *that* off to experience; and I do wonder how much better it really is if we just think of the 45+ Hz range.

Advice on other inexpensive open-baffle-friendly woofers would also be much appreciated.

I’ll make this short and sweet, i have a friend that really needs to dump his collection due to the results of Covid 19 economy.
Monitor 4 speakers in great condition Model X Servo tube amps in excellent condition refreshed by Roy Esposito
Includes about 16 extra NOS tubes for amps

$1300 Pick up only

Need it gone this weekend

In Jax., Fl. Call or text nine o four-338- fourteen seventy

Hello,
Recently acquired this gorgeous Threshold SL10 but it sounds flat and clinical in comparison to my Pass korg B1. Like very flat.

So I had a peak and someone has been here before me. No surprise on an amp this old. Caps need to get replaced so they were. High quality black gate and Panasonic caps used by the looks of it.
But I noticed one cap in an unusual orientation and performing a simple image comparison shows maybe, just maybe one of these 47uf 50V caps is backwards.
Am I loosing my mind?

Context:
Both are driving Hypex ncore Nc400s with Klipsch Forte 3 at the helm.
Turntable is micro seiki DD40 with nagaoka MP-150.

I really thought the Threshold SL10 was going to hand it to the Pass Korg B1 but maybe I’m just super wrong.

Would love your thoughts.
Thanks and stay safe.
Jules

Hi,

Not sure if this is the right thread to post in. I'm on the hunt for 6 micron Aluminium foil (or thinner) with a paper backing that can be removed using water. I intend to use a cutter to make a trace and then glue that to some mylar.

Any help would be very much appreciated.

I am building an established design but for aesthetic reasons only, I want to put a 3/4" radius on the vertical edges of the baffle. Will this affect the sound in any way? The design fits my requirements perfectly so I don't want to spoil it. Simple language only please. I am a mere mortal and don't take easily to numbers or design software.

I'm looking for a preamp build for my dynamic mic and I already have an OPA2134PA that I don't use. Is there a build that I can use this opamp? Is it suitable for this application?

Hello:

I don't know if I'm in the right forum but here goes. I have a Harman/Kardon HK6500. I've owned it since new. I was wondering if anyone know what the dynamic power ratings are for this particular unit. 8,4,and 2 ohm power. I used to have a sales brochure which listed it but I've since lost it. Any help would be appreciated.

Thanks

Quick observation:

My midrange has Le of 0.54, and Re of 7.8, the calculated Zobel is 9.75Ohm, and 5.7uF.

However, during actual testing of the speaker, a more desirable result came from increasing the resistance, 18 Ohms & 5.6uF. (I know the cap value should have been changed, I'm just exploring options)

Here's the question:

If I only want to 'slightly' correct the impedance rise of the midrange, I obviously can't change Le, but can I use a higher Re in the calculation, thus giving me 'less' of an impedance correction.

Midrange is the Accuton C158-8-085

I am trying to cross to the Tweeter at 2,800 Hz, and with the 'proper' Zobel, the mid drops too soon, even with smaller inductors.

I have recently purchased the following Unbalanced to Balanced Convertor boards but the vendor now tells me that he has lost the parts list.

Can anyone help ?

K.G-dynahibal KG Kevin Gilmore Unbalanced to balanced preamplifier PCB | eBay

Hello all,


Since a few weeks the MTX RTT8P is randomly playing very soft but I cannot figure out what it is causing it.

It will play fine at some moment and the other moment almost all volume is gone.

Most of the time I can get it back up by setting the gain very high and then back into the original position.
The sub will play fine again for like 15 to 30 minutes before losing the volume again.



During all of this no protection light goes on nor does the power led go off so I'm really in the dark here.
Initially I thought it might be something with the audio source like the audio signal was gone but after testing from another source the same problem occurred.



Hopefully anyone has experienced something like this because I simply don't know where to look anymore.


Best regards,


Mob

Hello all,

I'm aiming to build a custom front loaded horn for an outdoor sound system.
The cabinet will be similar to altec m-17 (but smaller).
it should go between 150Hz and 1500Hz approximately.

I've been reading about horn theory and design. This paper (http://www.quarter-wave.com/Horns/Front_Horn.pdf, page 16) says that good driver for horn should have Qts between 0.15 and 0.25.

These are however difficult to find in 10" and rather expensive
my choice came to this driver RCF L10 750 YK
with this indicated frequency response


and those T/S Parameters

• Resonance frequency (Fs): 68 Hz
• DC resistance (Re) (ohm): 5.10 ohm
• Mechanical factor: 4.20 Qms
• Electrical factor: 0.25 Qes
• Total factor: 0.24 Qts
• Bl factor (Bl) (T x m): 17.50 T x m
• Effective moving mass (Mms): 36.0 g
• Equivalent Cas air loaded (Vas): 26.0 liters
• Effettive piston area (Sd): 0.040 m2
• Max. linear excursion (Xmax): 3.0 mm
• Voice coil inductance @ 1kHz (Le1k): 0.50 mH
• Half-space efficency (Eff): 3.15%

But i Would like to know : WHAT PARAMETERS SHOULD I CHECK FOR DRIVER IN ORDER TO BUILD A FRONT LOADED HORN LOUDSPEAKER ?

Thanks in advance for your answers !


Alix

hello,
im designing a 3-way hifi build and was considering an MTMM configuration for mids and highs. however i dont think i have seen this configuration anywhere 😕 is it a bad idea? what problems may arise? when configuring the distance between mids and highs, do i follow MTM guidelines? will vertical lobing be weird? how do i best amp 3 mids, as 3x4ohm in series=12ohm or 3x8ohm in paralell=2.67ohm (was considering hypex/icepower class d amps but cant find any 2.67/12ohm data on them)?

thx for the help, cheers!

I purchased on Amazon .com the card of which I attach the images.
what I am interested in knowing is the type of component that I have to insert in the card and that I have circled in black, unfortunately I don't know the symbol.
moreover it seems to me that a different diet can be used, but in the photo that I attach and written in Chinese.
Someone can tell me which component I should use, and how to feed it.
Thank you all
Guido
If there is someone interested, I sell three 48v * 2 toroidal and two complete and assembled cards of the crescendo, of elektron + other 4 pairs of 2SK135 / 2SJ50 for 200 euros plus shipping costs.

I am looking for a sub for a 2SB631K and 2SD600K? They are used in the output section of an Audiobahn 4401Q

Around Easter 2000 it occured to me that an electrostatic AMT was theoretically possible using non perforated stator plates inserted between the spaces between the pleats. The membrane would be the standard ESL film with a conductive coating connected to a bias supply. One side of the HV audio drive is connected to all the stators in the forward facing pleat spaces and the other side to the stators in the rear spaces.

I now know that at least two others have come up with the same idea, as there have been two European patents issued.

The next idea that followed about two months later was to omit the stators, resulting in a more elegant design. The membrane would be made from foil coated film with alternate half pleats etched away. The etched areas would be given a conductive coating, preferably on the oposite side to the foil: the reason being that we need an insulating margin.

The "eureka" moment came with the realisation that we need two bias supplies; one positive and one negative. The odd numbered etched half pleats are biased negative and the even are biased positive. Similarly one side (phase) of the HV audio drive is connected to the odd numbered foil coated half pleats and the other side to the even numbered. With this taken care of we end up with a beautiful set of plus and minus signs resulting in the attraction and repulsion needed to produce AMT motion!

At this stage I had to admit to being pretty excited for the following reasons.
1. Ignoring the electronics etc we have the lowest cost transducer imaginable.
2.There are no magnets to get in the way of the acoustic design.
3.There is no size constraint due to the need to maintain a high flux density.
4. The pleats are individually accessible, meaning we can change the acoustic size with frequency to gain control over directivity.
5.We can change the pleat width, depth and length or curve the whole thing.
6. Has potential in wavefield synthesis and the OSD (Optimal Source Distribution, University of Southhampton, ISVR)

Having mentioned the excitement we come to the areas of doubt. Perhaps chief among them is the necessity of membrane tension to achieve stability, both static and under drive. To supply tension we have to wrap the membrane around something such as posts. While the span may be small and the tension minimal we still have the drum skin resonance. As it is a very small drum it may occur at a higher frequency than we would like. The wrapping post may have resonances too but they are also going to limit the ammount of air that can be displaced in their vicinity. Making the diaphragm more zig zag than parallel may help; something to be modelled by a fluid dynamics expert.

I could write about quite a few other aspects, and will attempt to post a drawing (zipped file) If someone more competent than me wants to post it unzipped feel free to do so. Anyone had similar ideas?

Keith

Hi, few questions about the input and output opamp circuits of a preamp.
Mostly copied from marantz receiver schematic.

Input:
- gain 3
- 22k input impedance? Want to keep it low for low noise, but is it ok?
- input Cap, wanted to omit it, but keep it safe.
- what is the purpose of R1 (470 ohms), and how to calc it?
- C2/3 should be some RF filters, as far as I know.



Output
- coupled to TC9459 vol control IC.
- 68k input impedance (marantz sr5200 as a reference)
- unity gain
- missing resistor on input (like the input stage).
Originally there is 470 ohm resistor in the marantz sheme. Purpose, value?
- coupling cap C1. Can I ommit it?
What if there is a DC offset and some constant current flow in the output of TC9459?
Would it cause the vol chip to distort?



P.S. I plan to put these circuits on one PCB with a common ground polygon.
This way it would be the closest to the input and output terminals.

I think I posted it in the wrong section...

Greetings,

This is my first solid-state power amp project (though I've built a few tube amps). I'm not going to pretend like this is a "groundbreaking" design- it's heavily based off the works of Douglas Self and (especially) Bob Cordell. I figured it would be best to start off with something "normal". After simulations, I committed the huge sin of going straight to a PCB layout, with the expectation that there would be a second revision. Images of my layout as well as a schematic are attached. You can see that there are some extra footprints on the PCB- I wanted to make sure that I had places for caps that might be needed.

To make a long story short, I have so far been unable to stabilize this thing. It's particularly bad into capacitive loads, as expected. The attached image shows an oscillation that occurs once the amplifier output exceeds something like 22 volts peak. This occurs into resistive, capacitive and open loads. Currently it is running off of +/- 34 V rails from my bench supply, which is current limited to 4 amps. In this case, the IPS, VAS and output stage are all running off the same rails (that's the orange wires in the photo). Note that the emitter resistors on the outputs are actually 0.47 ohms, not 0.22, simply because of what was on hand.

The Zobel network and output inductor aren't shown on the schematic. The Zobel network consists of a 10 ohm resistor and a .1 uF capacitor. The output inductor is of unknown value and is in parallel with a 3 ohm resistor.

C19 and C20 (which are in place of D1 and D2 on the board) made things a lot better, and C16 seemed to help some as well.

Here's a list of things that I tried that didn't help:
-470pF miller caps on the drivers and outputs
-33pF cap in parallel with R10 (unsurprisingly, it made things worse)
-Eliminated the pre-driver transistors and connected the bases of the drivers to the bias spreader with 4.7 ohm resistors (obviously the bias spreader had to change for that). Surprisingly, this didn't seem to help much, if at all.
-Second Zobel network after the output inductor.

Increasing the size of the miller cap C4 does eventually help, but at that point the slew rate is noticeably below 10V/uS. I'd like to see it better than that.

At this point, I'm starting to think that it must be a bad layout or major schematic error, since none of the things I've tried have solved the problem. I'd greatly appreciate some input from those with more experience dealing with this kind of thing.

Rookie question from a non-audio technician-

A 36pF mica capacitor on one channel has ~1 Vdc with DMM leads across the capacitor leads. The other channel, same component shows zero Vdc.

The capacitor that measures 1 Vdc is bad?

I ordered new mica caps, (expensive compared to other components), but won't be here for a few days and I'm trying to learn.

I'm planning a spud headphone amp build. Started my tube DIY addiction with a Van Waarde OTL and now looking to try OPTs.

Perusing schematics from Bartola, Ciuffioli, ECP Audio and the like I went back and forth between basic single ended and Parafeed topology several times. Finally settled on Parafeed to hopefully keep things easier on the wallet.

Specifically I've been inspired WTFamps Papa Rusa (russian spud). The deciding factor for me to follow this design was the excellent design guide for the Papa Rusa that was extremely educational. With the low/high impedance switch this seems to be a good choice. My HP collection is currently Grado SR80 (32ohm), Massdrop AKG K7xx (62ohm) and Sennheiser 6xx (300ohm).

I'm thinking of building the stock Papa Rusa and upgrading as budget allows.
Upgrades I have planned:

• 
  OPT: Upgrade stock Edcor OPTs with sowter 8665 or Lundhal LL2765
  CCS: Walter Jung's LM317 + DN2540 Cascode, or Bartola's Gyrator
  B+ regulator: Salas Shunt High Voltage Regulator (SSHV2)
  Filament regulator: Salas Shunt Low Voltage Regulator SSLV

Updates as design & build progress.

In a second order filter, I know that it should be reverse the polarity of one driver to prevent a deep hole in crossover region. But what if the two drivers are designed to already have a hole at crossover point. Says the drivers are not meet at crossing point, to create some eq. For instant, woofer is crossed at 2kHz and tweeter is crossed at 3kHz — with the same Q — the crossover point should meet at 2.5 kHz. As can be seen, there’s an absolute hole on a crossing region. So, does it need to reverse the polarity of one driver?

1) Perfectly operational Salas phono simplistic Preamp in dual chassis ready for Side and top covers and power connector to connect the two. Quality CMC RCA's. I ran this unit with my Clearaudio Maestro wood for a few years and worked flawlessly and sound was amazing. $350ca plus shipping! SOLD!

2) PCB's of Salas phono simplistic Preamp - $25ca Plus shipping! - SOLD!

Reason for selling - When I moved I exited vinyl!

Royd Minstrel SE with steel integrated stands.Newer version with Royd improved bass/midrange(doesn’t gum up!!).Great sound.UK sale only. £175 plus postage.

The "Edge" software application does not have a feature to model beveled or rounded-over edges. However, there may be a way to model this in two steps. Unfortunately, I do not have the theoretical understanding of how "Edge" works to know if this proposed method is valid. My suspicion is that it is not totally valid, but it will give a workable estimate.

Let us assume we have a 300mm x 200mm baffle, and we mount a driver in the center. The edges of the baffle have been beveled with a 45 degree 25mm deep bevel on all four edges. The flat portion of the baffle is now reduced to 250mm x 150mm, while the outermost edges of the baffle or cabinet remain 300mm x 200mm.

If we run two simulations in Edge, one at 300 x 200 mm, and one at 250 x 150 mm, we will get two different curves. I suspect that if we average those curves together, we will get a good estimate of the true response with the bevel. The peaks and valleys of the two curves tend to average out to something much smoother than either one by itself...

Thoughts?

I want to synchronize my SMPS controller to a fixed clock derived from my Class-D amplifiers (divided by 2) to avoid any potential noises produced by beating between all them.

My amplifiers run at 300KHz, and after a comparator, counter and optocoupler I get a clean TTL 150KHz waveform, because I want a SMPS switching frequency of 75KHz.

I want to feed it (with a small cap in series) to the SYNC input of the SG3525 controller.

My questions are:

a) Can the Rt, Ct and Rd components in the SG3525 be set so the approx. free-running switching frequency is also 75KHz, or do they need to be set at a much smaller freq. so SYNC operates correctly? (I would like the control board to be operative with or without synchronization, at approx the same sw. frequency)

b) Must this sync signal be 50% duty cycle or can it be, say, 25%?

Best regards,
Pierre

Just a few hours ago, I was a happy person, changed my smartphone display with a new one for the first time.


A few minutes later, while the phone was still working great, I saw a gap where there wasn't enough glue, in the bottom side of the phone and I injected more of it, then I let it aside to let dry the glue dry. I clamped the display using two laundry pegs. Rechecked the phone, it was alright.

An hour later I found it sadly that the display was blank and it had stopped working. No backlight, only the touchscreen remained working, as it obeyed blind finger commands.

My only suspicion is the glue, which is polyurethane based. I put lots of it and it contains some kind of smelly volatile solvent, smells a lot like contact cement (xylene and/or toluene). What reason could there be? The glue cannot attack metals, but what about plastics?

I have no idea.

For sale are the following tubes. If you have any questions or are interested in any of these tubes please send me a PM. Thank you.

1)

A pair of EI 12AX7 ECC83 vacuum tubes. Although these tubes are labeled as Telefunken they were actually manufactured by Ei in Yugoslavia. These tubes have long, smooth plates and halo getters. They have been tested for shorts, grid leakage and gas on a restored and calibrated Sencore TC-142. The results are as follows:

Shorts: PASS
Gas: PASS
Emission:
Tube 1: Triode 1: 100% Triode 2: 100%
Tube 2: Triode 1: 100% Triode 2: 100%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube under test by one step and noting any significant reduction in emission performance. Both triodes of both tubes performed excellently.

I would like $60 plus shipping for these tubes.


2)

A Mullard ECC81 12AT7 vacuum tube. This tube has a square getter and has the code sequence Tk1 B8F with the "B" signifying the Blackburn, England Mullard plant where this tube was produced. This tube has been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1: Triode 1: 100% Triode 2: 99%

In addition this tube has had a life test performed on it which entails reducing the filament voltage of the tube under test by one step and noting any significant reduction in emission performance. Both triodes of the tube performed excellently.

I would like $35 plus shipping for this tube.


3)

A pair of General Electric 12AY7 tubes. These tubes have angled square getters and grey plates. They have been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1: Triode 1: 95% Triode 2: 94%
Tube 2: Triode 1: 95% Triode 2: 95%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube under test by one step and noting any significant reduction in emission performance. Both triodes of both tubes performed excellently.

I would like $55 plus shipping for these tubes.



4)

A trio of 6679 12AT7 tubes manufactured by RCA. The 6679 tube was originally manufactured for mobile communication and maintain output even with variations of filament voltage. They are equivalent to a 12AT7 tubes. These tubes have square getters and all three have the date code of "6122" which equates to the 22nd week of 1961. These tubes have been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1: Triode 1: 102% Triode 2: 103%
Tube 2: Triode 1: 102% Triode 2: 102%
Tube 3: Triode 1: 102% Triode 2: 102%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube under test by one step and noting any significant reduction in emission performance. Both triodes of all three tubes performed excellently.

I would like $65 plus shipping for these tubes.



5)
A trio of RCA 12BH7 tubes. These tubes have long, grey plates and halo getters. They have been tested for shorts, grid leakage and emission on a restored and calibrated Sencore TC-142. The results are as follows:

Shorts: PASS
Grid Leakage: PASS
Emission:
Tube 1: Triode 1: 93% Triode 2: 91%
Tube 2: Triode 1: 93% Triode 2: 93%
Tube 3: Triode 1: 96% Triode 2: 96%

In addition these tubes have had a life test performed on it which entails reducing the filament voltage of the tube under test by one step and noting any significant reduction in emission performance. Both triodes of all three tubes performed excellently.

I would like $35 plus shipping for these tubes.

I understand the main thing to know about mounting torroids and that is to not let both sides of the steel bolt come in contact. As that will create a short circuit winding that will fry the transformer.... My chassis space is limited but if I can mount a 3 inch torroid on top of a 5 inch one I'll have room. I'd be leery to pass an 8mm steel bolt through each torroid, thus coupling them on the axis. But what if that bolt were made of nylon? I seem to remember seeing commercial products that mounted two torroids coaxially, but can't find that photo now.

Do think I'm ok using a nylon bolt, I already verified on the breadboard that I can stack them with no ill effects when experimenting. So would you see any long term effects using a nylon bolt and stacking them in the permanent chassis?

Hi all,

Which do you prefer and why? On paper the sziklai pair is superior - lower distortion, fewer high order harmonics and better temperature stability. However, in real life the driver transistor of the sziklai pair can oscillate on switch off requiring compensation capacitors and perhaps degrading sonics.

Theory aside, what do you prefer in a practical circuit and why?

Look forward to your thoughts!

Hi,

The EQ slider leds / lights became very dimmed for no reason. the EQ still works great , he slider functions to modify sound still works fine for both channels.

Please find the attached pictures and service manual as well. Do you think some of the components might got weaker? like any capacitors etc? Need some help please. it's a vintage EQ which produces amazing sound and i have to fix it regardless.

Looking forward.
Mobin

Looking to buy a pair of woofers, to experiment with dipole bass. Since experimenting wanted to buy used

Either of the above 10" woofers would be great if folks have some and not using.

I am located in California (Sacramento or SF)

Thanks

Shri

hi guys ive breadboarded this circuit and it works but the offset is too high (0.5v) and im thinking i used the wrong resistor values, for R1 and R2.

the transistors are BC550

what R values should I go for?

thank you in advance.

I am remodeling my family room and want to make it a better “listening” environment for stereo and a future multi-channel system. Many years ago I read Earl Geddes book “Premium Home Theater” and one of my big takeaways was his recommendation to use CLD to absorb bass while preserving midrange and treble liveliness. Although Geddes also recommends CLD for sound isolation it is not the highest priority for me since one corner of my room has an open ½ flight of stairs to the kitchen with no good way to enclose it.

I am planning to incorporate CLD into the ceiling, the front wall and one sidewall using isolation clips, 7/8” steel hat channel plus 2 layers of drywall with visco-elastic mastic. My room is about 8ft x 14ft x 24ft.

Is high mass of the constraining layers needed for optimum bass absorption? There seems to be plenty of data (and science) indicating that high mass is very important for sound isolation (which makes sense) but I don’t know if that is also the case for low frequency absorption. Lightweight ½” drywall is readily available and I would consider that a diy project; however, installing 4ft x 14 ft sheets of high density 5/8” drywall on the ceiling is more than I want to tackle and I would hire that out. (All butt joints can be avoided by using 14 ft lengths.)

Any other thoughts on my plan would also be appreciated.

Hi
Has anuone a schematic for Threshold fet ten/HL.

Not for fet ten/e

Hello to all,

I am trying to make my fist 2.1 boombox. I would like to be portable and also to use it outdoors. I have choose some parts (please check the links below) but I can not understand if it will be loud enough.

One from the woofers below
Dayton Audio DS135-8 5" Designer Series Woofer Speaker

Dayton Audio DC160-4 6-1/2" Classic Woofer Speaker

one set of full range speakers
Dayton Audio RS75-4 3" Reference Full-Range Driver 4 Ohm

Dayton Audio RS100-4 4" Reference Full-Range Driver 4 Ohm

Fountek FE85 3" Full-Range Speaker Driver

Amplifier
TPA3116 2.1 Digital Audio Amplifier Board HIFI DC 12 24V BASS Speaker 50W*2+100W 767775830347 | eBay

I am glad to hear your recommendations and also I would like ask if you are thinking that I have to built a crossover. How I can calculate any crossover?

Lately I've been thinking about the difference between vintage and modern (also super good/average sounding) guitars, amps and pedals. I've read/watched a lot about PRS, I love the sound of prs guitars and amps (although I don't own any), for some reason they just sound better/more vintage-y to me than most other modern gear. I've read that they obsess over every little detail (like putting a capacitor in the carlos santana model to make it sound like its plugged into a really long cable).

This begs the question: how can we replicate parasitic and component drift properties of components and things like pickups and cables to make them sound more vintage, and do we even want to?. I've heard of people putting caps in paralell with resistors and vice versa, does any of this work or is it just sake oil? Also, wouldn't that decrease the total impecance by a LOT?

My research reveals that over decades, component values drift up ad down and they aquire parasitic properties like capacitance and inductance (which may be why vintage gear sounds warmer, because the extra capacitance cuts treble). But I could not find out how much they change, how can we quantify this? i.e. How exactly (quantifyably) does age affect components?

For example: a vintage pickup sounds different now than when it was made (correct me if I'm wrong). What happened to the pickup in the 60+ since it was made, and how do we replicate it? My best ideas would be a cap in paralell and to weaken the polepieces' magnetic field somehow.

Another example: will putting caps in paralell with the resistors and resistors in paralell with the caps on a new amp, make it sound more like a vintage amp (or any circuit really)?

Thanks for reading and I'm looking forward to hearing different peoples' opinions on this 🙂

Hi all. My Sinclair sub decided to stop thumping recently. I run my speaker through its amp and they still operated but the 8" sub simply developed a hum (60Hz). I have it on the bench for testing but don't have a schematic and wonder if anyone knows where I can buy a service manual or access the circuit diagram. I've written to Sinclair but haven't heard back yet. I don't know the age of it but looking at Sinclair's website it's fairly ancient as they do list an owner's manual in their archive. Any help will be appreciated - thanks.
Regards Johnno

So just got around to Re-Capping My NAD 3020i Amplifier which I've had for around 3 years, It's never given me any problems and this is the first time I've had the hood off.

The first thing I noticed was that it's fitted with ST Microelectronics output transistors MJ2955 and MJ3055, the codes on the transistors are 99045, 99051,and 99044, I've tried to see if I can get a date for these codes but so far drawn a blank.

Something is telling me they just don't look original, The other NAD's I've worked on have all had Motorola transistors fitted.

Anyway, I was wondering if this would be a good candidate for fitting the 0.33R Emitter Resistors and the 4R7 Base Stopper Resistors.

Would appreciate other members Thoughts.

Fun to have but the reality is I haven’t used it in a long time as I’m not building much these days. Works fine.

Seems like they go from $200-600 on eBay. Not sure why the range is so high. But I’d love for someone here to have it. $300 Plus shipping OBO.

I would like to know how to increase the gain of this pcb to attack 2 tweeters cut in 8000 hz




NE5532 * 24 ultra baja distorsion 12W*2 Auriculares Estereo Amplificador Board Para Estereo | eBay