Hello!

Left (upper) channel on my 315 recently died but for some reason works when I short hot & cold on the output - which in its turn offsets balanced gear down the line. The following item loses 5-7 db on the left channel. I guess my short circuit makes it semi balanced, or something like that?

I will figure it out!

Anyway, since it's a 25 year old beast filled with ~60 Nover 16V 100 uf caps per channel I thought I might as well recap it. Actually it doesnt use any other cap than those Nover 16/100. In & out level stages, eq stages = all Nover 16/100. The power supply use two Nover 50V 4700 uf and one 16V 4700 uf.

Any tips on what to use instead? What cap would be suitable for audio and an upgrade. I'm looking at Elna (on Mouser) RFS-16V101MH3#5

Elna are 10 mm diameter instead of the Nover 6 mm but should fit. Spacing between legs are 5 mm on both the Elna and Nover.

Or would you recommend anything else?

(the 315 also uses a lot of Philips NE5534N opamps 🙂 )

Hi, I need some help, please.

I have two of these drivers. I can seem to calculate an ideal enclosure to make a sub with them.

I purchased these about 10 years ago, knowing what I know now, I wouldn't buy them again. From the response graph, they don't look like they go down low at all.


Woofer Speaker Driver - 10 Inch | Jaycar Electronics

Seems like a shame to chuck 'em in the bin, but am I just wasting my time with them?

Data in the attached .zip file

I'd appreciate any help or suggestions

SOLD.

Never made them.
12 page plans. One full size drawing.
$25 shipped usa lower 48.

FINISHED. WTB: Scan Speak (15m/4531) Sonus Faber Cremona midrange

No longer needed.
Speakers will be locally sold.

Hello.
I have a damaged Sonus Faber cremona Midrande (WOF30001)
Does anybody here has one or two original replacement units?

Although I know they are not standard versions, a pair of scan speak 15m/4531 could be interestig to try.

The problem in the midrange is that the coil wires are broken at soldering point with tinsel leads.
I have checked continuity at the voice coil and it is ok, but the soldering point is in bad condition.
Calle me crazy, but I managed to solder a pair of wires from the voice coil to the speaker terminals (I had nothing to loose) and the driver works good, but this is not a dewffinitive fix.

Another chance: Any of you here can make a good repair or knows where to do it at a reasonable price??





Thank you

Hi
I made the amplifier part of the device whose design I liked very much. It works successfully.

Since I don't have an oscilloscope, I can't do extensive testing. In my ear listening tests, I can say that I sounded better than any amplifier I had done before.

I apologize for not being able to use the English language well.

Hi everyone,

I’m looking to do individual output mods to my beloved Tascam portastudios (488, 488 mkII, 414 MKII).. I’m curious if anyone might be able to offer any guidance... I’m just getting a start with soldering... reading schematics... identifying/sourcing/ replacing components... and generally wrapping my head around audio electronics in general.

I’m looking for any info, but ideally, specifics would be most helpful. Service manuals for all three models mentioned are available..

Thanks!

I moded my 6th order bp idea to fix that air-compression thing and here it's (just a sketch, not scaled).

Could someone please sim this for me, cos I don't know how to...?

I'm now ready to build this and looking for dimensions.

If space is your concern, I have enough space in the room to place any large of a box.

For t/s reference, here's the driver I'm gonna use.
12TBX100 LF Drivers - B&C Speakers

Thanks in advance... 🙂

I originally made this preamp for a 6AS7. The gain was as expected only 1.7. I ended up needing more gain, so simply swapped the 6AS7 for a 6BX7. Got plenty of gain, almost 20dB (18.8x), and that with a much too low value for the plate resistor.
This sounded fine and I was happy, but I knew it was not optimal with the 2200ohm plate resistor (which is ok for the 6AS7) and I finally replaced the resistor with a 3900ohm value. I also replaced the 10uF! metallized film coupling cap with a proper 470nF value foil cap. (I paralleled 4 x 3.9nF COGs just for good measure).
Much better!
The plate load should actually be higher for the 6BX7, and if the 6BL7 is to be used it really really should be higher, more close to 10kohm. But it's a compromise with the available voltage, the current I want high, and so forth. As it is it sounds plenty good.
But if done again, and not just using parts at hand, I would get a proper tube rectified supply giving at least 250V. Alternative is of course choke load the plates, which I think will be my fix, enabling me to keep the lowish 175V supply rail.

Nothing special at all, just another pre. This can take 6SN7, 6BL7, 6BX7, and even the 6AS7.

Edit: the load lines shown are with a plate voltage of 175V, so that will be either with a higher b+ rail, or with choke load.

Hi there,


I have built couple of TABAQ variations, and quite like them. Especially the softness of MLTL. Have built none of multi-way units.


Requirements:


1. Two way with the main "star" being the woofer unit. Thinking ~6 inch woofer with tweeter or quality full-range. It can be 1.5 or 2.5 way, if it works.
2. Passive crossover.
3. Size is no limit! Any size, any size of the baffle, any shape of cabinet. Full size floor standers. No need to go high WAF but that does not mean that it has to look weird.
4. 40Hz F3 is ok, no need to go much lower, but will need to sound at least OK without woofer.
5. MLTL, TL, Horn or other. Everything works except open baffle or bass reflex. Also no line arrays for now. Pls no flame about this, this is personal preference, like color of cabinets. 🙂
6. The budget for drivers and crossovers is up to ~300-400EUR per pair, that is the same in USD, as the drivers tend to be cheaper on other side of the pond.
7. There has to be balance between the quantity and quality of sound, preference on... hmm.... maybe quality 60%, quantity 40%.
8. It will be driven by class D amp, but must sound well with others.
9. Drivers have to be available in EU.


Right now leaning to building 10F/8424 & RS225-8 FAST / WAW Ref Monitor MLTL version but still not decided. There is not much other on my mind...


Any advice is ok, be generous 🙂

Hello,
Could somebody know something about crossover for this ribbon Tweeter?
Key Features
Compact planar ribbon tweeter driver
High output and exceptional treble definition
Surface or flush mount installation
Potent neodymium magnetic design
Supports 4,000 Hz crossover, 12 dB/octave

Hi,

I replaced the 4 pin output socket of my unimproved 3009 with RCA jacks. Instead of connecting the ground wire to the ground socket I soldered it to the ground terminal of the left channel jack in order to avoid a separate ground wire from my preamp to the tonearm.

Is this correct, I want to avoid hums.

Cheers,

New In Box, Never Mounted

1 Pair Tang Bang W3 - 881SJF 3" Full Range Speakers

Asking $33 with USPS Priority Mail and PayPal fees included.

These usually retail for $35 each without shipping.



Typo: 3" not 3'

Just finished refurbishing my dad's pre/power amps and am hooked 🙂

For my next project I would like to build a pre/power amp combo, starting with a preamp. There are so many options that I am getting a bit lost. Can anyone recommend a preamp build with the following criteria:

1. transistor-based (not valve) and class A, obviously
2. no phono stage, tape monitors etc
3. bass and treble controls
4. preferably sonically compatible with a good class A/B power amp
5. good/high quality

Many thanks!

I was taking a look at the MA graphs for various drivers (as you do) and I was struck by how useful the CHR90 frequency response could be.
First you have the built in baffle step response which all MA fans will be familiar with. Then we have a dip that is centered around 4kHz which seems to match up to the Fletcher Munson curves. Then there is a bit of a boost at around 10kHz which may be useful depending on your age.
Anyone else think this dip at 4kHz may be a good thing?

Anyone have one they would part with?

Thanks.

Hello all,
I have moved into a new place and am concerned about line noise. I do NOT have a dedicated line for my audio /video system (all low level source electronics, amps, TV, cable box (TV, internet). But this line only supplies the above and a few lighting receptacles. In addition I am adding a noise filter receptacle (audioquest) on the 1st in this chain.

In a previous question (which I cannot locate) about how to hook up the audioquest receptacle someone had recommended another line treatment that could be installed (Cdm???). ANY recommendations is greatly appreciated.

Hi, since this forum offered such great advice on my last project I am turning to you again in hope for some help.

I had this amp for a year now and I am rather satisfied with it.

Joyo AC-40 - Google Photos

There is only one problem: A permanent background hiss as soon as I turn it on at around 30db (background at 20db). I usually play this amp at volume 2, so its no biggy. But I would like to understand and fix if possible.

IF I turn up the volume of the MIC channel, the hiss increases a bit (about 7db at max volume). That seems to be expected.

But hear comes the funny thing and that I REALLY would like to get rid of.

IF I turn up the guitar volume at 5 a zing (or beep) is added that changes frequency as I go further. It peeks (frequency and volume wise) at 7 at 42db and is gone back to the "normal" background noise at 9. It sounds a bit like tuning an old radio.

I tried to record it with my phone. CAREFUL LOUD!

Any help on diagnosing/fixing this is greatly appreciated!

I am sufficient with a soldering iron and a multimeter, if that is of any help.

Suppose a DAC is driven in such a way as the following:

Since a DAC essentially converts a binary string into a voltage or current, and this is done every time a binary string is presented at its input, it makes sense to hold all digital inputs at a logic 1 if the succeeding bit is also 1. This should avoid having the corresponding bit going down and up at the arrival of the next binary string. So, it goes something like this:

If the present bit is 1 and succeeding bit is 1, hold the input bit at 1. If the next bit is 0, drop the input to 0 normally. The same holds for successive 0 bits. This, according to my logic, should minimise some noise issues at the output.

I am selling a clone of the Norwegian amplifier Electrocompaniet AW180. A differential amplifier powered by stabilized voltage. It will play several thousand amplifiers. Bias 450mA. 40.000uF for channel.Toroid 450W for channel.Price for amp 1300€

Hi all.
Didn't post for some time, being busy with non related audio stuff.
Under what topic should I post my Open Baffle DIY constructions (Not for sale, at least, not for now, since I am now in Vietnam and will be returning to Montreal, Canada in one to two years.)
Need to know how to post pictures ?

Hi All,

i need to capture audio from an external amp into android.

I made a cable which connects mono out to mic, got a normal 4 pole to 4pole cable, chopped halfway then joined speaker from Source to mic on recorder side (Android phone)
its working fine but i have couple of issues and needed help to find a better stable solution

1: audio has noise, any way to cut it? (to be honest i can live with it, its not extremely critical, point 2 is more)
2: i have noticed weird behaviour, if i plug android side first then it uses the cable to record audio but if source side is plugged in first then android cable then it doesnt detect and uses builtin mic only.
is there any way or official cable i can use, this is quite annoying as this setup is not mostly used by tech people so they can plug cable in wrong sequence and app not to work.
thanks in advance.
kaleem

Hi all,
I have modelled a little 6080 amp with 5687 drivers and all is well in LTSpice.
However when analysing my results it is obvious that the 5687 is a bit marginal to get full power out of the 6080's, so I decided to try substituting a 6DJ8 for the 5687.
At this point the model refuses to run failing with "Time step to small". How can two valve models behave so differently in exactly the same circuit ?

Shoog

Well, you didn't win but here's a shot at building one of the "vfet-less" kits. I've got a pair of 2sk82 KD-33 vfets that I'd like to donate.

Rather than giving Papa or Jason any more work;

Procedure:
You: Respond to this thread, first come first served.

Me: If you're first in line, I will respond and give you my email.

You: Will donate $100 to one of the two charities, and email me your receipt and paypal me $1 (so I can print a shipping label with your address).

Donations to two great charities – diyAudio Store

Me: I ship them to you. CONUS only, because I'm also covering the cost of shipping here.

Hello, we have put together a port velocity calculator for round flared ports.

You can input port radius, flare radius, port tuning frequency, enclosure volume and velocity speed at an unflared port that I personally calculate on WinISD
The spreadsheet will then calculate port length for one flared end port or two flared end port and ofcourse the new port velocity.

Enjoy!
T5B Sound team

port_velocity_calculator_3.xlsx | Failiem.lv.

Just wondering,

I have a British DAC, a little Beresford Caiman SEG towards which I grew an antipathy, I don't need the headphone amp, don't like the external brick called Dorado nor I like the power brick, nor the led lights which make it look like a xmas tree, insomma, I don't like it any longer if not for the versatility of inputs, two SPDIFs, one USB and one Coax.

Now, given I need no high-end nor whistles and bells, one box fitting it all with a decent number of inputs, unbalanced outputs, will feed signal through a MacMini for LossLess music via USB and a TV and AppleTV through SPDIF, very basic.

Is there anything which can be built at home with decent sound quality and meeting the above requirements?

Grazie


Giovanni

Hello all!

Since I've been shunned to far away lands without my usual gear I've been fooling around with some transistor-based circuits in an effort to learn and hopefully make something cool sounding.

After building some fuzzfaces and rangemasters I started 'hacking' together a schematic for a positive-ground germanium preamp. When I say 'hack', i really mean it. But, to my surprise, the dang thing works and already sounds pretty good, considering.

My current issues and questions are these:

1) The variable resistor between the two gain stages works just fine up until about 95% of maximum volume and then just squelches out until there's no volume. I tried different pot values (1k to 500k) and increasing voltage from 9v to 12v - no change.

2) The frequency chart below says that this circuit is inherently dropping off pretty quickly under 200hz or so - how can I lower this? I want 80hz. (Note, I am using 2N527 transistors).

3) Since this is a total hack job, what could I do to improve it? I'm getting some good, colorful gain out of it at this point, but what are some options to try out and what have i done here that might be redundant or counter-productive?

Thanks and hope everyone's been doing great

Had my 368 as my entry into hifi and its awesome....but after looking around for more power, options being a c268 to bridge 300w per ch OR go with the new tech (which I prefer) being purifi amps. So c298 or more economically something like the VTV eval 1........BUT

has anyone opened up a 368 and just replaced the amp module with purifi amps? would the stock power supply handle this or would you swap that out for the SMPS that they usually come with?

i like the idea of hot rodding an amp and making it a sleeper 😎

thanks in advance


dan

If a audio dual matched transistor pair is used at the i/p of a balanced amp and each half fed with the two differential phases of the i/p signal, will the alternate heating and cooling effects on each device cancel out due to their proximity.

can we assume that the two devices are close enough for this to occur ?

can anyone think of any drawbacks of such a scheme ?

would the cancelation cover all relevant frequencies ?

does anyone know about this kind of stuff ?

mike

Hello, I've just left every experiment in DIY and bought one beautiful brand pair of speakers with dual chamber reflex:

Given my modest experience, it seems to me that reflex frequency is quite high, being speakers a bit boomy if not far from rear wall, and I would appreciate a suggestion to try lowering it. For my knowledge, a dual chamber reflex is made by a little chamber where is driver with a high frequency tuned vent opening in a big chamber with a low frequency tuned vent, opening out. So the first vent lets pass a larger band of frequency, after reduced by the second one.
My new loudspeakers seems to me exactly opposite: a large chamber with driver opening in a small chamber, so my questions are:
- how are the low frequencies filtered by the first low-pass vent able to pass through the second high-pass vent?
- where have I to work around to decrease the lower tuning frequency of cabinet, on the first or on the second vent?
Thank you very much.

Hallo,
I want to know the new products from Bumper/Zeuz. The old website is to find about
splash

I find only this website with a example of transducer:
12'' DC FR Series Woofer 1250Wmax - www.cybermarket.co.uk
additional
EARTHQUAKE SOUND CORPORATION vs. BUMPER INDUSTRIES
EARTHQUAKE SOUND CORP. v. BUMPER INDUSTRIES - 352 F.3d 1210 :: PreCYdent Search Engine

The last Adress, what I know was follow
BUMPER INDUSTRIES INC. USA.
8113 NW 54th. ST. MIAMI, FL. 33166
TEL: 305-592-3999 FAX: 305-593-1499
E-MAIL: bumperind@aol.com
...........WEB SITE: bumperspeakers.com

My delivery source and Bumper's european distributor 10 years ago was "ALTAI" in U.K. In the attachement the correspondence regarded new distributor and similar models from Zeuz (not Zeus)

A special feature was the ultimate ratio of price/quality and 10 years warranty

Perhaps one of you can find out for me the currently website of Bumper/Zeuz transducer - Thank you very much

In the process of removing the PCB board from my 300B amp, I learned that the cheapo wire insulation melted at a MUCH lower temperature than needed to unsolder the damn things... On top of that, there was so little room to get the iron in.

I think its best to solder tails on the board using ptfe or silicone coated, and splice in the leads where there is a bit more room, with double heat shrink... Thing is, I may want to go in and out a few times... Got me thinking, does anyone know of any type of disconnect or barrel plug that can be used to facilitate easy connecting / disconnecting of wires in a tube amp ? The B+ is 450v and the amperage is relatively low. I see connectors for 1kv and much higher amperage for electric cars, but dont want to spend $80 per!

If you've spent enough time in the Pass Labs forum, you will undoubtedly see references to Greedy Boyz. Since it's 2021 we should revise this or at least be considerate and start calling this group Greedy Kidz but that's not the point of my post.

If you are a Greedy Boy or Girl, you already know you are but if you are unsure, how do you figure that out? 😕😕😕

Feel free to share why you consider yourself a member of this nefarious group and wear your badge of dishonour honourably (yes it's Canadian spelling).

Being a fan of Papa and Wayne also does not qualify you as a Greedy Kidz, in fact, it's a prerequisite but it's the ability to take this to the point of 'too far' that will gain you this privilege of joining the undeserving.

I am one of the Greedy Boyz (or Girlz or Kidz if you don't care to identify) because I think the best amp is the next one I haven't built yet and I"ve built at least 1 of Papa's creations, enjoyed it, basked in it's glorious sound and then started researching the next one.

Please note, using the accolade 'fugly' alone doesn't qualify you as a Greedy Kidz but if you disagree, please feel free to explain.

As the creator of the term, I defer to the Mighty Zen Mod (MZM) to arbitrate 😀

Moderators, if any of this is inappropriate, please feel free to remove/lock

A device to boost the low end depending on level for closed cabinet.
With circuit diagrams and examples.

Greetings to all!

After several years of yearning I finally put together a lab to unleash my love for 70's electronics, and why not, audio.

Today I put my hands on a pair of Marantz speakers and a Magnum stereo.

Let's see what surprises await us.

Seventies.

Hi guys,

I have for sale audio oscillator Leader LAG 126S
- the item to have some signs of cosmetic wear, but is fully operational and functions as intended
- included original printed user manual

ship to: only EU
price: 370 EURO ( ex-work incl. shipping and paypal fees )
payment options: paypal

contact: milandks at pobox.sk / slovakia

regards
milandks

Hi,

I'm about to buy a pair of vintage full range drivers from the late 50'
Both drivers are 8 ohm and were connected in parallel on a push-pull 6BQ5 mono amp. in a console with a turn table.

What I'm wondering is that the unit (Zenith console) is using 2 drivers which have differente cone construction even though they were both manufacturered the same year and by the same manufacturer.

One cone has a radial seam and the other cone is a one piece cone, no seam.

I have seem in many occasion this configuration in Zenith console, using 2 full range drivers located close to each other but with different cone construction…

Both drivers have the same basket, frame material, magnet type and size..

Why go to the trouble of using 2 slightly different drivers ? Any idea why would a manufacturer would do this ? I have some ideas but would like to hear yours first.

I'm probably making too much out of this but I keep wondering the reason for doing such a thing.

If there is sonic differences between the 2 cones, I would prefer to know now before moving ahead with this purchase.

Thanks,
Eric

How does this happen?......................................


content of message deleted by Moderation.

Just compare

Mundorf Mresist Ultra

https://hfc-fs.s3-eu-west-1.amazonaws.com/s3fs-public/mundorf_mreu_30_datasheet.pdf

Isabellenhütte PBH

https://www.isabellenhuette.de/fileadmin/Daten/Praezisionswiderstaende/Datenblaetter/PBH.PDF

Furthermore Mundorf is describing that the above mentioned resistor was developed together with a Resistor Company known for Laboratory Grade Production.

The used Alloy can be considered as Isabellenhütte Manganin

Everything fits.

p.s.: Price of course is not the same

Hi, I have traced my full range speaker and I simulated the baffle step diffraction using Loudspeaker Design Software . I want to blend it using FRD Blender and Minimum Phase Extractor . The problem is that I only have Excel 2011 and everytime I load the spreadsheet, I always got an error message and can't find the upload frd button.

Can anyone help me blend this file? The file for the woofer will be named woofer.frd and the file that I got from simulating using Loudspeaker Design Software will be named Baffle step diffraction set as loss.frd and Baffle step diffraction set as gain.frd

Thanks!

Today I plan to drink half a bottle Absolut Vodka.
Proud as I am it is a Swedish vodka.

So far I have taken 2/3 of half the bottle (375ml).
I feel rather good, as you can imagine.
Cheers or as we say in Swedish: Skål!

I'm building a balanced preamp using TI DRV134 receivers, OPA604 opamps, and OPA134 line drivers. I don't know what value of dual pot to use for the volume control bridging the DRV134's to the OPA604's? Thanks!

Hello,

I want to make a mono summing RCA cable to connect my audio interface/DAC to a mono amplifier. The input impedance of the amp is 30kΩ, the input sensitivity (2Ω, 100W, 1KHz) is 0.83V. The source max output level is +16dBu and i do not know its output impedance.

What value resistors should I use? Do I need a resistor on the summed output that goes to ground? What is the purpose of this resistor (can be seen in the schematic below)?



The amp is a wondom model WONDOM | STORE

The audio interface a Motu M4.

Does anyone know a company that carrier this tweeter online or otherwise. I am looking to buy two of them for a pair of two way tower speakers. Thanks in advance!

here is a schematic for a ocb that goes between my volume autoformer and the knobs. It uses Nixie tubes to display vol knob position. I have an option to use external 5 volt power you can set with a jumper. other than that its pretty straight forward. Just feel better if I get a few more eyes on it.
Thanks in advance!

Jeff

Hi guys, looking to upgrade my cayin 300b headphone amp anyone got this amp and tube rolled ? I want the best available. Thanks

I intended to do the right thing by replacing the old power supply caps in my model 3 amp. What I found were some caps that are much bigger in value and size, and voltage. The originals are 24,000 with a 60 volt surge rating. The new ones are 37,000 with a rating of 100V. After replacing the caps, the amp immediately blew the 8 amp main fuse. I then put a 6 amp current limiter in the incoming AC line after the fuse. It still blows the main fuse. I am thinking that I would be better off just getting 24,000 uf caps of the same voltage rating and calling it good. Any thoughts?

This is on a Harmon kardon Citation 11 Preamp. Replacing the Electrolytes I also tested the Jfeds with a Transistor tester. It is testing as 2 resistors consistently. The board still had output but engaging the EQ was noisy.\

It is Q506. It, Q508 and Q510 all are the same part number and test as P-Channel with symbol gate pointer close to the source lead.
As much as I have read tells me the company which made these was bought up years ago. The numbers are P1053 215 above Mfgr symbol 7233. Unable to cross reference.

I see lots of people put those cheap VU meters off ebay on their tube amps, but was wondering if it is possible to use a decibel meter for the same purpose, as i have some awesome vintage decibel meters and would love to incorporate them into a steampunk styled build.


Doesnt really need to accurately measure VU or anything, but just really to serve as a level meter to give some sort of indication to how much the amp is being driven.


Would they require shunting, or just hook up across the output?

So I am looking to sell my father's car. It's a 1997 Infiniti Q45 in good shape. It has been a long time since I have done any private car sales. Back then I would advertise on the Auto Trader or recycler. What are the best options today? I know of craigslist, Auto Trader is still around but mostly seems to be newer used. Anything else out there?

Been testing a bunch of tubes and I suspect there is a fault since the meter gives a slight reading on the first leakage test on my weston 981 tester.

Heater glows normal on first test, but glows like a light bulb as I switch to the next series of tests!

Seems to give an OK reading on emissions however.

It's a Sylvania 6v6gt
Any ideas? See photos.

Here's what I've collected and to the best of my knowledge it's all the latest renditions .

The BOM I used as a general guide and ordered resistors and other components to my preferences . not quite sure who that came from . Use at your own risk .


Enjoy , Woody

Folks,

My sincere thanks to Woody, this is the complete FetZilla documentation endorsed by me, now made 'sticky'.
I have also appended here a complete distortion analysis of the FetZilla. Two highly competent EE friends of mine here in Melbourne took distortion measurements of the FetZilla on Monday 27th Feb 2012. They are taken at 1KHz, into an 8R resistive load, at outputs respectively of 1W (+10dB), 13.3W (+20dB), and 26.5W (+23dB):

Fundamental 10.00dB Fundamental 20dB Fundamental 23dB
H2 -93dB 5.012E-10 H2 -78dB 1.585E-08 H2 -78dB 1.58489E-08
H3 unmeasureable H3 -93dB 5.012E-10 H3 -88dB 1.58489E-09
H4 unmeasureable H4 -105dB 3.162E-11 H4 -93dB 5.01187E-10
H5 unmeasureable H5 -102dB 6.31E-11 H5 -103dB 5.01187E-11
H6 -96dB 2.512E-10 H6 -106dB 2.512E-11 H6 -110dB 1E-11
H7 unmeasureable H7 -110dB 1E-11 H7 -101dB 7.94328E-11

H8, H9 and H10 are all unmeasureable

THD by voltage 0.00274% (1W, +10dB); 0.01284% (13.3W, +20dB), and 0.0134% (26.5W, +23dB)
Measurements below about -80 dB can be assumed to be insignificant except in ultraclean designs

These figures are surprisingly good, but with output bias set to 370ma the first 5.5 watts of output are in Class A, so perhaps not so surprising after all.

I would add that the THD does not correlate well with the sound qualilty; rather, it is the profile of the distortion artefacts that affect the perceived sound quality for the human ear.

Not bad for a jfet, two mosfets, and two lateral output fets - only five active devices in total!

My thanks to Graeme and Paul for generously giving their time to measure the FetZilla!

Cheers,

Hugh

This is a 6-channel amp.

I'm not getting audio out of the rear L and R channels after combing through several other faults out of this amp (Those faults have been fixed) not related to these channels.

There is no audio signal at any of the pins on XM3, but I do see audio for these channels on U5 OpAmp.

I played around with different input switch settings and still cannot get audio down to these channels. No signal on the IRFx540 so its not the terminals.

I'm going to pull the board back out of the sync later today. Any clues?

Thank you in advance

if somebody looking for those TEST CDs, still available from here:
Digital Test - 106 Plages De Demonstration Et Tests Numeriques / 106 Digital Tests & Demonstration Tracks (1988, CD) - Discogs

This thread is dedicated to applications of lm3886 running at 125°C Tj.


On "Talking about lm3886"thread you can read why this IC is designed to be used at high temperature.You also find as references, uploaded intimate thoughts, of revered gainclone experts.
ARTY " heating an amp ic rarely made it sound better to me.i prefer them as cold as possible within reasonable level.if it gets up to boiling point then the highs become grainy and i don't like that". _________________
AndrewT " I wish I did not follow your precedent and waste my time reading it.I will go and unsubscribe in the hope I don't bump into this Thread again. "
　
The maximum temperature advised by the datasheet is 150°C, although the thermal shutdown occurs at 165°C to be switched back on safely at 155°C. Running at 125°C leaves a margin of 25°C .Using lm3886tf isolated version which has thermal resistance of 2°C/W+0.2 for thermal compound ,provides about 10W acceptable dissipating power tolerance.
A straight forward idea for constant power dissipation, is class A,but looking on the figure bellow at Vs+/-25v you can see a strange flat curve from 5W to 30W Po the IC dissipates 15W to 17W.

lm3886load.png
　

If at 15W dissipation the Tj is 120° to allow at 20W to become 130° with 2.2°C/W ,then the heatsink temperature is to be adjusted about 85° (120-15*2.2) . I tailored two heatsinks shown bellow , adequate for 30° ambient temperature.
　heatsink.jpg
Both are 2.5cm thick developing both 200cm.sq.(buttom excl.) surface(air-metal contact).The shorter and wider one above weighs 105gr. It needs about 10mn to heat from 30°to 85°.The other weighs 65gr and requires only 5 minutes and costs half price.
The circuit to be used is non_inverting.For 31W it requires a gain of 23,feedback resistors 22k and 1k wil do,a 33k pulling down the mute to -V ,a 10k potentiometer and a pair of ceramic 100nf decoupling the rails. Power supplies are provided by two switching power supplies 24V3A each, adjusted 25V and you get the best sounding lm3886 ,on condition you are using it above 5W.
If this is suitable for outdoor use ,it is too high power, for use in an apartment.To realize it by yourself,adjust the sound to a comfortable level and mesure with a digital ac voltmeter the voltage on speaker,even with a low efficiency one you will be astonished how the average power is so low.Adjust it to be 5W (6.35v for 8ohms) and realize how loud the amp under design, should run, to be heated properly.
The remedy for this is to use an ordinary fullwave rectifier.If it is designed to provide 25V at 30W output ,then at low power, the supply voltage can go above 30V.On the curves above it shows the amp can dissipate 15W, starting at 2W output. Now new problems arise.At 10W continuous output, the supply is far above 25V,but from the begining of the design, up to 20W disssipation was considered ,but at transients, the supply capacitor's high voltage, charged at idle, must collapse rapidly in order to prevent overheating the output transistors above 250°.Here, the calculations are in jouls.The most important parameter is the dynamic thermal resistance of the output transistors shown on the figure bellow. A simple calculus math. could resolve the problem if it was a linear one.

　
If the value of the capacitor is decreased to lower stored energy, then the ripples become higher To keep the supply above +/_25V, the ac supply sould be increased ,that means higher energy stored, so to lower the capacitor value ,and so on. By estimation and trials the retained value of the capacitor is 3300uF along ac 2*22.3V (300VA PS transformer for two channels).
Now we have an amp good to function between 2W to 30W.
　
A parenthesis
******************
OPTIONAL READING
******************
The Gaincard from47Labs, became a reference ,as sea-level or freezing point of water,since a holly hifi magazine qualified it as,top grade.Ever since, IC amps are compared relatively to it.
COMPARING WITH GAINCARD

The Lm3875 used in Gaincard, needs to be heated Tj of 135° to have the thermal feedbacks canceled , instead of 125°, see figures bellow,Then the heatsink temperature must be 95°instead of 85°.
lm3886. lm3875

　lm3886bias.png. lm3875bias.png
Running at the same operating condition, the Gaincard delivers 25W instead of 30W.

　
lm3886. lm3875

　lm3886load.png. lm3875load.png
The dynamic thermal resistance being much higher,the Gaincard uses 1000uF capacitors with 2*23.6V ac instead of 3300uF 2*22.3Vac.This may be, results in lower dynamic sound (not shure).
lm3886 lm3875

　
Where the Gaincard excels, is at heatsink.It uses a tiny aluminum enclosure (10cm*8cm*4cm) with aboutt 2mm thick upper and lower plates linked firmly (thermally) by a 5mm thick side.
see the pictures of the heatsink dismentled.
http://www.6moons.com/audioreviews/47labs5/gaincard.html
The total radiating surface is 200cm.sq. But with the two heatsinks joint together, the bottoms are effective only by half ,this reduces the radiating surface to 160cm.sq. 15W dissipation highers the temperature from 30° amb. to 95°.
As the IC is mounted on the thin bottom plate, It creates a hot spot of 95° to be reduced to 60°-70° on the upper edje.With such heatsink primo,children are not injured accidentely,secondo it provides lower thermal inertia to reach 95°in less than 3 minutes.
　
*Gaincard temperatures are calculated/estimated for Tamb of 30°C.
**************
End of parenthesis
　
There are two more problems to resolve. 5minutes or 2 minuets ,it is still too long to heat up.The most important is still at low power.If you are listening as background music while reading or dinnig or simply it is late evening and you are listening a soothing music ,The amp will remain cold and provide you toy quality sound.
One step beyond.
How about powering this IC to its maximum voltage +/-40V.If I can provide 150ma at this voltage by a high impedance supply added uppon, then I get 15W dissipation at the first watt.
But who will swallow the 150ma if their is no signal?The IC will take it's share of 50-80ma,what is left, is taken by a pair of power zeners.The total power dissipated at quiescent now is 12W.How about I give a hand and make it 15W.By this the heatsink once heated to 85°it remains constant.
Signal,or not signal,is no more a question.As the IC dissipates at quiescent 4W the Tj min is about 95°.Just tiny watts and it goes to hell° and this, up to 30W output.
To make a high impedance supply toppling a full wave ,is to add a pair of capacitors across the bridge and add two diodes in series to transform the PS into a weak tripler.The values of the capacitors fix the supplementing current.47uF+(33uF/50Hz or 22uF/60Hz) .See the circuit bellow.


　 Basic3886circuit.png
basic3886.jpg


Yes the BASIC3886 is the 300B of semiconductors.Now it just got a power supply.Similar to 300B which requires also an adequate nonlinear driver and a decent output transformer to be called an audio amp,the BASIC3886 also needs some auxiliaries to deserve the title of 21st century audio amplifier.



THE BEST IS YET TO COME
　
KOKORIANTZ
　
Curves are extracted from TI datasheet.
　
　
　
　
　
　
　

　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　
　

Hello,

I recently installed my old PC450 amplifier into a new car. I had this amplifier for years with no issues.

In the new car I immediately noticed the amp got very hot and stopped outputting. I did not have an inline fuse installed.

I powered up with a current limited supply and found the output transistors were getting very hot. I removed them from the board and checked for shorts but found none. I replaced anyway and still have the same problem with new output transistors.

The amplifier powers up normal drawing normal current then after about 30 seconds it draws max current limit from the supply (5A) and all outputs get hot for all 4 channels.

Currently only the outputs for CH1 are on the board and the problem still occurs.

Any help would be greatly appreciated!😀

I have a pair of Classic Audio Nirvana 12s in some large cabinets approx 18 wide x 14 deep x 45 tall boxes. Built out of Baltic Birch Ply, internally braced. Speakers are in fantastic shape and have never been abused. I am asking $400 a pair. Basically buy the drivers get the boxes for free. I can demo them for you from my 300B SET amp. I picked up a pair of transmission line speakers on craigslist that are pure magic with my amp and no longer need the 12s.
I am in the portland area.

email me at jclass.audio@gmail.com or better yet text me at 541-231-2297

Jeff

I ordered two Jantzen 5.6 mh coils and one is now back ordered until end May. Any recommendations for similar value and low rdc ? I am a newbie and anxious to start my first cover. Thank!

Peavey ipr27500
Can somone/anyone answer me as to why my peavey amp ipr2 7500 is just cutting on and off on and off when i press power...... no input singal ...no output load is connected... ac line voltage is 110

Hi,

My request is for a preamp Haman/Kardon, Citation 11.

I am trying to find a replacement for Q508 (similar to Q506 and Q510) witch original was FET P- channel P 1053 by AMELCO .

Is someone able to help me?
Thank you.

Michel.

Hey all, I currently have a working Music Angel XD950MKII, but that is only after replacing some of the capacitors in the driver section, as it smoked in just a few minutes after the initial startup. Guess China-made 450WV capacitors don't necessarily mean they can actuall work at 450WV! Anyway, I have another capacitor that is starting to bulge, and I would like to replace it. Problem is, I can't identify what the value is. Have any of you come across this problem, and/or doesn anyone happen to know what the value of this capacitor is? There are two, one for each channel, but the ones in mine aren't the same and aren't marked with anything meaningful. The one that is bulging is the one on the right, this picture was taken prior to 'the bulge'. Thanks in advance! ~Elfox

I just bought a new Rega RB330 tonearm for my Systemdek IIX, replacing the stock Profile II tonearm.

I understand I need 222mm from the center of the tonearm mounting base to the spindle. Inserting the Rega tonearm in the stock tonearm board I am unable to get 222mm.

Do I need to cut a new tonearm board then drill and mount the new arm?
Does the thickness of the tonearm board matter? I would think yes for VTA. The stock board is 3/8”.
What’s the best way to ensure I get the 222mm from the spindle to the center of the tonearm base?

Thanks!

I have a Precision Fidelity C7 - in basic unmodified form. I want to bring it up to its highest spec. and would be grateful if anyone has a schematic to share for the 7A or REVISED model.

I will be using it with a Bent Audio MC Tx.(Silver) and a variety of power amps.

I will be very pleased to hear from anyone who has worked on this Pre.

Many thanks

Brian

Hi there,

I am selling a pair of high performance tweeters Fostex FT17H with base and 1uF Audyn True copper max. Retail price is about $150 for the tweeters and $120 for the caps ( total $270).

I am selling the pair at $135 plus shipping from 06851.

I am selling this 1m long Pangea AC-14SE power cable.
It is lightly used. Retails for $50.
Asking $30 shipped to USCON.

Hi Guys!🙂
First of all, please try to forgive me for my bad english😱!!!
I would like to ask you what is the best type of metal for the best heat dissipation of an old (obsolete) audio integrated transistor ( TCA940, 10 watt max audio transistor).
Unfortunately the TCA940 heats a lot, so I want to build a very nice and useful (handmade-DIY) heat-sink for this transistor, because the (rare) common heat-sinks for the TCA940 on the market have a shape that doesn't fit the available space in my small circuit board.
I've a good idea how to do, but I've no idea about the best metal to use for the best heat dissipation.
I was thinking to use copper.
What do you think about copper as a possible solution? or does exist some other higher quality metal for the heat dissipation? I don't care about the price!
Please guys, help me!!! give me your opinion!
Thank you in advance for your kindness and patience!
Best Regards

Legendary Erno Borbely Original Kit assembled/ Tested - used little

Uses Toshiba Dual FETs (2SK389), low distortion Resistors/ Capacitors and 2SK216/2SJ79 Mosfets capable of driving low impedance Headphones ( 40 Ohm). Complete copy of Erno Borbely Document copy will be sent along with this Kit. Requires +/- 24V DC low noise Power Supply is preferred. One can use LM317/337T based PSU. I have Erno Borbely assembled Power Supply Regulator with Rectifier is suitable for this Kit. You can also buy DIYAUDIO super regulator kit and prepare nice LN PSU. Prefer US buyer but willing to ship internationally

send me a PM for Pricing/shipping costs etc

A friend of mine sold me their Pass Labs X5. While seemingly sonically perfect, it has certainly seen some "love."



A previous owner was a cat lover and possibly a smoker, so the internals were very dirty.



After spray-dusting, a thorough exterior wipe-down, and a DeOxIt pass on all the contacts, things have been sounding great.



What I'm wondering is... since the "wings" have seen a lot of love, and are quite easy to remove, what kind of tools do I need to either buff out the scratches? I think the tooling required to mill a proper replacement set is a bit outside my wheelhouse (though I'd love to learn!) and certainly beyond my budget for this restoration.

(I also suppose it's not outside the realm of possibility that Papa Nelson & co. have spares -- not exactly a DIY solution, but it might be the cheapest one!).

On an electronics side, I'm wondering if anyone here has worked on these and has any advice for tuning them up?

Just because it sounds really nice to my ears doesn't mean it's not out of spec and therefore could sound even better. I had a Rotel amplifier that I used for over a decade before I took it into a local amp repair shop for service when a channel went flaky. $120 later and I felt like I had a brand new amplifier because in addition to replacing a handful of bad caps, he also re-biased the channels. I don't think it sounded that good since the day I bought it. Maybe never.

I'm fairly new to electronics work, so I've never had the pleasure of re-biasing an amp. I don't even know if that's doable or advisable here... or something a neophyte should avoid for fear of life and limb... again, just looking for advice. I do have some local electronics expert friends in my DIY club I could work with if COVID weren't a present-day concern. Hard to get elbow-to-elbow when you shouldn't even be in the same room as people! 😀

I have buy for a lot of year a 9 Pin Aikido all in one PCB
and like to build it at the moment.
I like to use the 6N23P witch are the russian 6dj8 Tubes for all Postions and My Transformer do have measured:
247V AC 70ma
6,8C AC 2,5A
The value of capacitors ist clear , for the regulator i like to take the LM317T
Can i use alternativ for all MUR410G the 1N5402(D9, 10, 11, 12 ) ? Or ist it only as replace for the D5 -D8?
Now my big problem the Resistors;
I think this values are clear
R19 499 ohm
R20 124 Ohm
R1 1 M
R11 1M
R9 100k
R10 90K ( ? )
and the rest, i need realy help!

Can anyone help me please with the other resistor Values?
I like to use the recommended values B+ Voltage 200V for 6dj8



Thank you very much and regards from germany

I need to identify this 3way large switch. It's the channel selector switch. I count 16 legs plus the 4 post to solder the switch in place.
I disabled the switch cleaned and fine sanded.? Deoxit it and conditioned the switch yet it still cuts out the audio.

I am building a balanced-to-unbalanced receiver circuit ala ESP's Project 87 (Balanced Transmitter and Receiver II) and want to add the input filter as shown here., to trap out any RF disturbance. My question is: Does the selection of capacitor type here have any audible effect? Normally I use PolyPropylenes for any low-value capacitors in the audio path, but in this particular application, the size is quite a limiting factor; thus I am considering use of a MLCC COG type cap. Usually I would avoid any ceramics in the audio path, but in this case, is it really in the path? It would seem that the capacitor here would only be involved at super-sonic frequencies and thus a non-factor. Opinions?

Admitted, the title sounds weird. Actually, we already have a thread concerned with the use of LM1875, in particular with more in parallel, as power stage in a composite amplifier. The final aim there is to test such a composite amplifier in BTL-configuration. Without being aware when I bought my LM1875, I ended up with specimens that are probably “fake” and do not behave fully as LM1875 ICs delivered straight from TI. My “fake” LM1875 sometimes perform more like TDA2050. As the TDA2050 is pin-compatible with the LM1875 and their specifications are pretty much alike, this existing thread also include the use of TDA2050. ST no longer produces TDA2050 but a company in Taiwan, Unisonic, produces a version called UTC-TDA2050V that seems to perform very well and can be bought at a very good price. Such is for the existing thread.

Work with LM1875 and TDA2050 in the existing thread got to a point where it was difficult to disregard that other chip-amps may also be very suited for composite amplifiers. In particular for higher power levels. In posting #510 ( LM1875 in parallel configuration and used in a composite amplifier. ) of the existing thread, a scheme was drafted mentioning a plurality of chip-amp candidates.
Before a chip-amp is used in a composite amplifiers, its behavior should be investigated such that an implementation of the chip-amp is used in the composite amplifier that is 100% predictable and reliable. This sounds trivial but even the well known LM1875 showed some characteristics, like self-oscillation and de-rated operational limits, that took most of the time before the complete amplifier performed well. Another problem related to use of chip-amps at a gain below the minimum gain specified in the datasheet.

For other chip-amps than LM1875/TDA2050, where should the results from investigations be disclosed? The existing thread is already becoming comprehensive with LM1875/TDA2050 issues, parallel-coupling issues, controlling OP-AMP issues etc. Therefore, the present thread is started with the purpose to disclose experimental results and considerations relating to these further chip-amps, when using them below the minimum gain, when connecting them in parallel, when improving stability, when protecting them from overload etc.

FF

Anyone have any high res pics of this amp or knows what transistors go in the following locations .

Q304
Q308
Q301
Q305
Q302
Q306

The prices I have been seeing seem a bit too good to be true, shipping is free over a certain $ amount and that seems to apply to Canada as well.

AUDIO-HI.FI, Loudspeaker shop

I recently picked up a Adcom GFA-535-II off of Craiglist for $80. I found a service manual for it and have been looking under the hood. I’ve found that the schematic has an error and omission and thought I’d share my findings. I attached the service manual and the schematic extracted from said manual with the errors and omissions highlighted.

The Error

The schematic in the service manual shows to input to the VAS stage coming off of collection the feedback transistor (Q603/Q604) of the LTP. When I first saw this in the service manual schematic I was a bit baffled by the topology. I couldn’t figure out how this could possibly work. I opened up the unit and probed the connections with the continuity setting on my DMM and confirmed the error. The connection should be to the collector of input transistor in the LTP (Q601/Q602 not Q603/604).

The Omission

The omission is an electrolytic capacitor C637/638 bypassed by film cap C635/636. These are DC blocked caps in the feedback loop. In my unit (Rev-2 of the PCBs), these caps are mounted on the boards with silk screen and are spec’d at:

• C635/C636: Film 0.47μF 400V
• C637/C638: Electrolytic 22μF 50V

C637/C638 seems a bit undersized to me. I suspect this is due to space constraints as the caps were added as part of Rev-2 of the boards without any other apparent layout changes. The low pass filter formed in combination with the 1KΩ feedback resistor create a 7.2 Hz pole. This would typically be a 100μF cap in most designs for a 1.6Hz pole frequency.
I understand there are three versions of this situation:

• Original with no caps
• Caps installed on the underside of the PCB without silkscreen
• Caps installed on the top side with silkscreen (Rev-2 boards)

I found out about the omission from an article posted on the website Hoppe’s Brain (user Phloodpants on this site). The article is too big to attach, but a copy can be found here. It’s a good read if you’re interested in this amplifier. His website also has good information on these amplifiers and several mods.

Other Omissions?

One more item to note… The capacitors in the service manual go to C631/632. The omitted capacitors I found started at C635/C636. This suggests that C633/C634 exist somewhere. However, I could not locate them.

That’s all. I hope someone else finds this information useful.

hi folks,

well ive got the above amp which i have repaired a few times. however i'ts now popped one of the o/p trannys, they are craftily labelled f15n/f15p. obviously these are mf's own codes, a habit they are fond of so they can rip you off when you need replacements.
there's a total of 4 per channel.
i've no idea if they are mosfet or bipolar. circuit consists of (input to output ) - 5534 and 5532 , then x2 of each mps a92/a42 (which ive changed a few times), followed by 2sd649/669 pair then the big TO3 f15n/f15p pairs. there is a bias pot too.
amp always sounded good but is terribly designed from an engineering point. originally had x4 50V 10000uf smoothing caps, running at , u guessed it, over 50v (53ish). changed them for 63v while ago.
i actually wrote to MF 1st time those caps dried out, pointing out the problem. Engineering director wrote back claiming the caps were rated at +10% so 55v . pah! the cheek of it.
also the mpsa92/42's literally cook, along with two 1/4 1k0 metal film resistors which should def have been 1/2 watt.
anyway, im flat broke at the minute and need to revive this beast.

if anyone can help with any info i'd be extremely grateful.

many thanks

raymond

I have a 557 Power Amp that is part of a Meridian stack I bought back in 1998 or so (502, 500, 566-24, 557). It's all performed flawlessly on a daily basis since last week when my 557 turned on then promptly turned itself back off. The soft start begins as usual and the system turns on (if there is a source you can hear audio from both channels) then after a couple of seconds, I hear a click, the system mutes and the power down process starts. I removed all inputs and outputs and tested again with the same results.

I was able to find a 557 schematic and as far as I can tell, there is a DC offset tripping the DC Protection Circuit you can see at the bottom of the attached schematic. I'm getting about 250mV of DC at the P.A. out line (at C2) coming down through R8 (at C3) to the minus input of the top op amp and the + input of the lower op amp (at C4) then on to R25 (labeled DC Protection). This is causing the op amps to drive the output transistor that mutes the amp and trips the protection relay shutting the amp off. I'm thinking that one of the main electrolytic caps is bad due to the age of the amp. Has anyone seen this problem with a 557 before?

Also, there is an adjustable resistor labeled R27, VA 1111 (probably Voltage Adjust?) at position B4 in the schematic. Does anyone know if that is the DC offset adjustment? See image and schematic below in reference to description. It's an impressive protection system. Any help will be greatly appreciated.





Thanks,

Dean

Classic EL84 Stereo Push-Pull Amplifier PCB Hifi Tube Preamplifier Board Kit | eBay

Something like this seems interesting for a $60 kit plus some output transformers. Thoughts?

Hi, one year ago, I received a blast of four big lead batteries from my solar equipment, I lost both ears, not a at all but enough for not apreciate any more my equipments, as product of many years of get vaccum tubes for my projects, I got many of them. I have a old list I made several years ago, probably there are more, anyway I have list attached to this message you can check. If any of member make offers.
Best Regards
Esteban

LISTADO DE VALVULAS MIAS.xlsx - Google Drive

Also I have several tonearm, cartridges, turntables.

I uploaded a file with pictures from any other parts and components from my hifi chain. Loudspeakers, drivers, my record disc collection, with patienty is possible to see. More details are coming, today is hard day for me. I guess my way are headphones

Pictures: fotos hifi para vender - Google Drive

of the 'show me state'


http://www.kctv.com/Global/story.asp?S=5660988

from the place, where the official state bird, is a mule

I'm mucking around a bit with an A75 that a buddy brought over. Physically everything looks perfectly great inside this amp. Nothing is burned, no zener diodes are amiss, all the lights do that they are supposed to, but this thing only makes about 2W into 8 ohms at 0.1%THD/1kHz. Oddly the performance of the amp gets better at low frequencies, and it just about does its rated power at 100Hz.

I have adjusted the bias to 15mV, temporarily tacked in new PSU caps, reflowed the solder joints on the output devices, and I split the pre/power sections and verified that the preamp section isn't causing problems. At this point it's both channels of the amplifier that both have the exact same problem. Other than some power supply parts, I'm not seeing a whole lot that's shared between channels. All the voltage checks listed in the service manual are OK and the 2W the amp puts out sound decent.

I'm trying to do as little work to the board as I possibly can since it's single sided and rather sensitive, so I'm hoping someone has experience with this particular issue.