1973 KA-8004 integrated amp with three push buttons for three sets of speakers, allowing the option of driving six speakers simultaneously. Only recently added third set and perplexed why so few amps offer this feature, including other amps of that era and newer designs as well. Kenwoods next amp, model 8006, had the conventional knob with maximum of 4 speakers: A, B, A & B, or C.

Seeking insight regarding enhanced design features (if any) the 8004 might incorporate to offer six speaker option, or did Kenwood throw caution to the winds for this particular model. 8004 lacks power output indicator or load warnings.

Graph is from 1975 McIntosh amp clinic. Kenwood trumped advertised McIntosh distortion levels. 8004 has never required service.

For those who are using active DSP, could you post what software you are using for measurement? And what equipment such as amp, DAC ...? And if you're using a Convolution software?

For example:

Measurement Software: REW, miniDSP plug-in, ...?

Equipment: miniDSP plate amp, DAC (brand?), ... ?

Convolver software: Equalizer APO, ....?

Am I missing anything?

so, i am waiting on my drivers as we speak. The idea is to start a journey with my first open baffle.

The fullrange will be the below model from Sonido. Tricky question starts now with the woofer and the XO.

Cuurent idea is a Faital 15PR-400 most probably on a U-Baffle to save some space ...

Hopefully over xmas i will find some time for a prototype ...

I found my way to this forum when i searched for something.I like vintage audio and i want to learn repair things and build things myself.So i think this is a nice site to register 🙂
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I built a passive pre amp with a 100k ohm pot - should I have used a 50k instead?

Hi i need advice on how to go about on this amplifier it was brought like this to me to repair

Hello!

I'm looking for a simple-ish, stable regulated vacuum tube based (silicon diodes for the rectifier and no zeners, for stability reasons) 0 to 250V bench power supply schematic.

I have 3 different input power supplies (one 300V and two 330V, all isolated) and separate PSUs for the heaters and stuff.

I have a few different kinds of tubes:
One 12AX7
Two 6AQ5
Two PCL85

Exotic tubes:
One TM-85 pulse tetrode with a max dissipation of 60W, similar to 8252
One 2C39A triode with a max dissipation of 100W

Cold-cathode voltage regulator:
VR-150

I am looking for peak current availability of about 0.5A, which both of my "exotic" tubes can handle.
Cooling the 2C39A is also not a problem, even at close to 100W of plate dissipation.

I have tried to build the Heathkit IP-32 with different values and a PCL85 and a 6AQ5 and trying to eliminate one of the regulator/refrence tubes, but it just doesn't work well.

Thank you!

Good morning is the first time I write on this forum, I apologize in advance if my writing is not correct, but I am using a translator.We come to the problem, this amplifier turns on regularly but there is no audio, not having the scheme I searched for some news on the forum and thanks to these I found the transistors Q57 and Q59 short, and also the two zener DZ9 and DZ11. Although the tensions have returned, the audio is not yet checked if there was the pwm signal on the gates of the final mosfets and these are absent.
At this point I think the pwm pulse is missing and it should be generated by the AD2K module, in fact there is no power supply on the IC LM219 terminals.
Without a scheme it is very difficult to work on it.
Does anyone in the forum have the wiring diagram of this module, or can you help me to resolve the fault?
Thank you

Hello, I'm new to the world of portable audio and I'm trying to make a Bluetooth speaker.

So, right now I have 2x10w 4ohm speaker and I need an amplifier to them.
I was thinking to buy a more powerful chip to deliver 2x10w with less THD+N than a simple 2x10w and them somehow, limit the power to not burn the speakers.

Getting in consideration I already have a Bluetooth receiver, that isn't important to the module integrates one.

I'm planning to use a 12v lithium battery (with a step down to power the BT receiver) and wanted it to be possible to charge with USB (so step up to 12v to battery?).

After this little explanation of what I want to do, what amplifier do you recomend for this?

Thanks in advance,
eX Radikal

P. S.: I've searched a little bit the forum before asking this question but came with no answer because everybody talks about too powerful amplifiers or to use in somewhere else but in a small BT speakers.

Hey all.


I've just ordered one of these to see how it performs in place of CCS cathode bias with a toroidal PT as OPT.


Has anyone tried this?


Bias Supply Modul for four Tubes (Single pcb to Control 4 Power Tubes) | eBay

Hi !

Here is a schematic of output tube BIAS servo published by Hopchik (Oleg from Voronezh), on DIYAudio.ru forum. According to feedback from forum members it works as expected. I didn't tried to assemble this schematic, posting here in hope someone could find it useful.

Link to original post on DIYAudio.ru
C???? ??????????????? ???????? ???????? ????

R19 and R20 connected to the grids of output tubes (CETKA in Russian means Grid).

I send a message to the author yet till now he didn't responded. Copyright notice on DIYAudio.ru states that copying and citation permitted if provides link to forum and nick of the author.

PS. What really bothers me with this and all similar servo schematics that they will modulate BIAS voltage during low-frequency high-level transient, possibly need low-pass RC filter with very high capacitance. Have to do some simulation in LTSpice.

Any feedback appreciated.

I have a pair, mint condition AD12202/ m4 12" Belgium i was going to make a pair of speakers for my office, I am dealing with prostate cancer and I must get rid of them. I can make someone a great deal. The 2 12" and the 2 tweeters are in excellent condition, and sound awesome.

Dear Members,

I built a tube amp, and I have problem with 50Hz noise, what is come from the PSU. The problem is after the 100uF, 100R, 330uF CRC filter 50Hz hum is audible, and base on the measurement the 50Hz noise is quite high 123mV RMS (512Vpp). I have built the PSU and the Tube stage together into one PCB so I have limited possibilities. I have two option:
Replacing the 100R resistor with MEC-100 electric choke
https://hfc-fs.s3-eu-west-1.amazonaws.com/s3fs-public/tentlabs_mec_datasheet.pdf

Or using a Mosfet filter parallel with the 330uF capacitor. I would like to implement the following circuit
HV Power Supply

I attached the Lt-spice simulation of the new circuit. What do you think If I solder two wire to the legs of the 330uF capacitor, and build a separate PCB with the few components, and connecting them parallel with the capacitor acording to the LT-spice circuit It will work?

Hi,

I currently have a DAC I build comprising of a CM6631A USB to I2S converter and a PCM1794A I2S to analog.

I'm looking to upgrade to four channels and believe USB is not the best way to do it. HDMI or Displayport (over USB-C) are available, so I've began looking at:

Buy Products Online from China Wholesalers at Aliexpress.com

My intention is to send stereo over four channels most of the time, and occasionally downmix 5.1 to 4.0 in Alsa (Linux) and send it over where I'll have a second PCM1794A available for the rear channel.

Can you see any issues with this approach or suggest alternatives?

I have an amp project where I am going to use an indirectly heated dual damper tube as a slow start device. It has a max DC output of 175ma 6BY5GA.

https://frank.pocnet.net/sheets/127/6/6BY5G.pdf

Can I use it in a hybrid bridge or as a pass device with the plates in parallel? Which is "better"? Does option B with parallel plates increase the tubes max DC rating of 175ma or lessen its voltage drop over option A?

I am not talking about Milton. For years I have enjoyed my little MHDT Lab Paradisea sitting between my Mac’s and my amplifiers. Mac’s have come and gone. Amplifiers have come and gone. The Paradisea has kept the music going.

Now, my newest Mac does not have Toslink. I am limited to USB or HDMI. Sadly, my Paradisea has neither. I have seen USB to Toslink converters but have not read anything about how well they do, nor about their audio quality. The Paradisea has Toslink, RCA, and BNC digital inputs. I have done several searches of this forum and am not having any luck. I would appreciate being pointed to a thread I may have missed and/or welcome any and all advise.

Thank you

Since I saw an unexpected friend, I thought I'd share a picture.

The book was published in 1982.

how can one make this amp get out of protect faster?

im getting ready to replace the small caps on some 20 year old adcom amps & a preamp, & eventually will do some other brand amps i have & was wondering what the "best" brand/model caps are for the money. i know thats a loaded question & everyone has their own opinions. just wondering what most people use in the mid-fi price range.

im not looking for anywhere near the best, im actually on somewhat of a budget since im doing multiple units. this is only for the smaller electrolytic caps not the big power caps in the amps. im seeing lots of guys use nichicon & some say panasonic but they might be harder to find.

does changing these aged & cheap caps improve the sound of the amp or preamp?

im trying to place 1 order for all the caps i will need, mouser has another part i need to repair the tuner in the preamp so i will be ordering from them most likely.

Hi,
I just finished recapping two Adcom GFA-545 MKII amps. I replaced all electrolytics and set the bias. Both amps work great, however one of them has an annoying squeal during shutdown. The squeal occurs on both channels. One channel precedes the other by about half a second. It occurs about 5 seconds after flipping the switch off.
I can also make it squeal on powerup using a variac to slowly bring it up. It occurs when the AC input voltage is between 10 VAC and 50 VAC. The pitch of the squeal varies with the input voltage.
It appears to originate in the DC offset circuitry around the Adcom 3A IC. During power up it oscillates as viewed at pin 6 when the supply voltage on pin 7 is around 2 volts. As I bring up the input AC the supply voltage at pin 7 jumps to 10 volts and it immediately stops squealing.
Any thoughts on how to stabilize this op amp?

Hello!

Selling 5 different unused Speakers from the seventies. It is a inheritance from my father. They were keep safety (warm, dry etc.) an are working fine.

1) AD 0211 SQ 4 / 2422 257 32011/ DD 04 027 101 Philips
2) AD 70620/M4 / 2404 257 46101 / DD 01 220 102 Philips
3) AD 7066 /W4 / 242 257 47001 / DD 04 232 102 Philips
4) AD 81671/MFB4 / 2422 257 48607 / DD 00 145 126 Philips
5) ITT 49197 52282 LPB 120/90. F 7944

Please make me an offer. I will sell by piece (circa 60 speakers available).

I look forward to hearing from you!

Sorry the last thread was in error. this is the correct model. i changed the switches first after i checked for bad transistors. Now the audio is clean, yet missing from channel one. So i started pulling transistors, a test good.

I have some very large tubes I got years ago from a radio transmission tower, which I purchased from them, but have no idea what I can use them for ... does anyone have any idea?? (see photos)
...I have a few of them, and another really large one --- just thought to get them at the time for possible use later on...

Celestion TF0410MR ~4" - $35/pair, plus shipping, 2 pair available:

Celestion TF0410MR - Google Photos

One of the more popular mid-range drivers from Unity/Synergy horn projects. These are all new, in their boxes, 2 of the drivers have been mounted to a test baffle and measured for the purpose of testing for a Synergy horn build. These are very well built, and widely loved mid-range drivers. 8ohm

Celestion TF0510MR ~5" - $60/pair, plus shipping, 1 pair available:

Celestion TF0510MR - Google Photos

Same as the TF0410MR, I bought these to test for a synergy horn project. They've been mounted and measured, then put back in their boxes. 8 ohm

Peerless 830856 - $50/4 drivers:

Peerless 830856 - Google Photos

These are nice, truncated frame, Peerless woofers. I was going to make an MTM with a nice ribbon, or dome between them, but never got to it. These are in their original packaging, have never been measured or mounted. 8 ohm

Faital Pro 4FE35 ~4" - $35/pair, plus shipping, 2 pair available:

Faital Pro 4FE35 - Google Photos

You guessed it, more Synergy drivers. These are really nicely made little full range drivers. Check the forums and you'll find a lot of different designs that use these drivers. 8 ohm

HiVi B4N ~4" - $15/pair, plus shipping, SOLD!

HiVi B4N - Google Photos

Nicely made, shielded drivers. They look fantastic, and are used in many different designs. 8 ohm

HiVi B3S ~3" - $10/pair, plus shipping, SOLD!

https://photos.app.goo.gl/MeSkdVLjQghEEnnq8

Great looking, very nicely made, shielded full range drivers. Zaph Audio has a design that uses these, I made a pair for some friends and was really blown away by the sound they produce. Great for computer speakers, very nice little drivers. 8 ohm

HiVi T20-8 - $10/pair, plus shipping, 1 pair available: SOLD!

https://photos.app.goo.gl/2fTYFmhYEmt6Ynt56

Never used, don't remember how I ended up with them. They are in their original boxes. 8 ohm

That's it for now, I think I have some more domes, and some bigger Hivi woofers. I may also sell some of my Tang Band full range drivers as well. I need to dig them up first.

Offers accepted. I will package all shipments extremely well, to ensure everything makes it to you safely.

My Bryston BP25 Pre Amp has a bad relay and I am looking for a replacement(s). I've looked on google to no avail.
Part #NF4EB-4M-24V.

Can anyone help!

Thanks,

MAK

I'm unsure which Forum this should go in, Source or DAC but seeing as the question is about the DATA from the Source, here we are.

I am doing some very basic experiments with a 24 bit Ladder DAC, lots of resistors and a few shift registers. Very similar to the Sonic Solutions DAC, see the attached circuit. Mines not quite the same but very similar. My diagram is just a pencil sketch so far !
Early tests show it works but with a lot of noise, I have a long way to go yet ! Still, having a bit of fun !!

If I feed the DAC with 16 bit Data from a true i2S source (Philips CD Player pre the Filter or a SD Card Player I bought) the DAC seems to work and the MSB is where I would expect the MSB to be etc etc.
However, if I feed the DAC with 'converted EIAJ i2s' (see the circuit attached borrowed from Lampizator) the DAC sees the 16 bits but places them from the LSB 'upwards', if you see what I mean. So the MSB of the Data appears 8 bits 'down' from the DAC's MSB.
If I feed the 'converted i2S' into a TDA1541 (Pin 27 to +5V) it decodes it fine, but then it would, it's a 16 bit DAC chip.

I am obviously missing something in the differences between EIAJ and i2S.

Any help gratefully received.

P.

Hello everyone,

I’m in the middle of restoring my G36 and whilst I have the front separate from the back to carry out maintenance on the motors (clean old grease and replace bearings etc) and replace caps on the push button module with x2 type, I would like to take the opportunity to replace the motor run caps.
Taking apart a G36 is very time consuming so it’s worth doing all I can to service it.

Could I get advice please if these Kemet caps in the link below would work well on the G36? These are rated at 3.5uf 5%. I would welcome advice please and if these won’t do the job where can I get a set for my machine please? As I’m in the UK I’m trying to find stock in this country right now.

Also could I find out what type of diodes are used on the push button modules? Are they standard silicon diodes ? Would something like a 1N4001 work as a substitute?

Here is the link..
404 - File or directory not found.

Many thanks
J

This Akabak script simulates a tall BR with a RCF L18P400 at the bottom of the box and ports above. The hight of the box is just enough to stack the 18", a 10" midrange and a horn on top. I wanted to simulate a good port placement.

I started off by doing a WinISD simulation, a -3 dB bass shelf, giving about 280 liter volume.

Taking all the parameters to Hornresp, I could almost simulate the box using a stub. Anyway, exporting to akabak gave me a quick start into akabak.

I made a few mistakes. Shorting a vent to 0 is the trick for ending a section.

Hopefully this code can be reused

Is there a way to execute site and thread searches which return only those results containing embedded graphic attachments, such as schematic images?

The search criteria itself would still be regarding the text of the post title or body, but I want to restrict the displayed results to only those posts also containing a schematic graphic.

I would like to request for my account to be disabled/deleted as I don't use it anymore. Thank you.

Howdy,

I'm looking for a friendly member who is setup for SMD rework. I've got a small job that needs done - replacement of a 26-pin TSSOP. If you are willing to help out, please PM or email me.

Thanks in advance!

Anyone know offhand what size spaghetti tubing to use for film caps on a speaker crossover? And also wire size to extend the leads if needed? Been looking around but cannot seem to find a spec for the wire size/gauge.

Thanks!

- Jeff

Up for sale I have a pair of brand-new Vifa / Tymphany NE149W-08 5 1/4in midbass drive units.

Superb compact midbass; coated pulp cone impregnated with wood fibres; aerodynamically profiled cast basket and FEA optimised neodymium motor with copper cap for reduced reflections, enhanced airflow and low distortion. Long-throw suspension with varied profile surround to reduce effects of the transverse wave. 1 1/2in voice coil on titanium former. Extended response, flexible and suited to multiple enclosure load types. Some images attached for those unfamiliar with the driver.

Brand new drivers; I'm asking £80 + shipping for the pair.

On the subject of packaging, I use cardboard wrap, and sustainable FSC rated outer cardboard boxes fastened with heavy-duty packing tape. These are reinforced inside with recycled heavy-duty cardboard and packed with recycled brown / grey packing paper and high quality bubble-insulation.

As always, thanks for looking. 🙂

Here is an example of a head phone jacket 1/4 inch ( 6.3 or 6.35 mm ) in a 10mm modushop slim line front panel. I didn't want a jacket with a big ugly nut on the front side. So the question (for this first time preamp builder) was how to attach such a jacket on the back side of the front panel? Although my solution is quite straight forward, I did not found clear photo examples on such a construction on the internet. So lets have a look, see photo's. I used the Cliff CL 12345 jacket with gold-plated contacts. The standoffs are 20 mm. More photo's of the jacket, the cavety needed and its further construction, and my build log of my preamp, can be found here:

AMB Laboratories DIY Audio Forums • View topic - α24 with M3 preamp built log&Q's

Hi does anyone know of this driver ic as i cannot find it. Pin number 6 and pin number 12 are directly connected separately to two gates on the output mosfets

I had a pair of surplus Scan Speak D2905-9500 tweeters that needed a home. After asking for a suitable 2-way design on this forum I decided to build a pair of Carl Richard’s original design “Intimates”. You can see Carl’s description of the speakers here: Introducing the "INTIMATES" (high WAF & quality sound) - Techtalk Speaker Building, Audio, Video Discussion Forum

These use Scan Speak “Revelator” 15W/8530K01 mid-woofers in a 15L (0.5cuft) ported cabinet with a “capacitor-less” first-order crossover. I built my own cabinets out of MDF with angled internal panels to mirror the internal dimensions of the Dayton Audio TWC-0.5CH curved-sided cabinets that Carl used. My cabinet walls are 18mm MDF. The baffle board is 25mm MDF.

The cabinets are finished with charcoal grey 80% sheen auto acrylic paint. It turned out a bit too battleship-grey looking for my liking. I wish I had used an off-white or cream colour. Oh well.

The Revelators blew my budget out of the water, so I went a bit cheap on the crossover inductors. I didn’t use foil for the tweeter inductor and I went slightly thinner on the woofer inductor wire. I mounted four parallel 47Ω 10W resistors so I can tweak the tweeter response. I’m currently only using three of the resistors to give about 15 ohms and the woofer/tweeter balance sounds pretty good.

The cabinets are fully lined with thick felt from a furniture removalist’s blanket. I haven’t added any stuffing or played with the port length yet. The port is 2” diameter and 9” long (50mm x 225mm).

I really like the sound of these speakers. The Revelators give them plenty of punchy bass and my ears are well used to the D2905 tweeters after listening to them for the last 10 years in my Ariel 6Cs. I’m listening to Tubular Bells as I type this (showing my age!). This piece has a lot of interesting sounds and I’m hearing stuff I haven’t noticed before. Acoustic guitar sounds superb. In fact, I’m starting worry I might like them more than my LX Minis!

Total cost was AUD1050 (although I already had the tweeters).

These will most likely end up wall-mounted in my workshop. Yeah, I know they are expensive workshop speakers, but I listen to music for hours at a time in my workshop. I like a lot of bass and I think these will perform well. They don't seem to be fatiguing based on the listening I have done so far. The Revelators have a sticky coating on the cones, so I will have to make grilles to keep the wood dust off them.

I'll post some pics below.

Hi, just got a second hand Dynaco's mk3. Bought it as a modded ones.
Upon inspection, I found that the ultralinear taps unused and instead to have a separated transformer feeding a 240Vdc to the pins 4 of the 6550 output tubes.
I have to say that this amp do have a solid state rectifiers and extra 1000uF at 800Vdc caps of power supply filtration.
B+ is at 500Volts.
It use the standard 6AN8 input/driver boards.
I know in certain Heathkit and Fisher amps the screen supplies are derivative from B+ with RC filters, but why not use ultralinear taps on original output transformers??
I know that the ultralinear taps are part of the design of Dynaco to minimize THD. Globalized with NFB.
Just a curiosity.


I know in big FM transmitter plate B+ supply do have a separated screen supply, make sense in non output transformer design as FM is RF couple to the antennas.


🙂

Hello Friends !

Please help share Protections schematic for Class D Amplifiers for driver stage and speakers..

Pcba2z Solutions

I've got a tube/transistor tester of some kind of Italian brand. The problem is that I don't have the service manual and without it is impossible to operate it.

Does anyone know this one, or better, has anyone a operation manual for this tube tester.


The text on the tester says that it's a

Provavalvole / Provatransistori model 891 and it comes from Chinaglia Belluno Italy.

Hey everyone!

I have a tube preamp that I decided to upgrade all the components to higher end stuff.
All components are still the same value but tighter tolerance but better components (PRP resistors, Nichicon fine gold capacitors and Mundorf Evo capacitors )
My issues are I lost most of my bottom end? Not sure what components caused the drop in low end maybe some experts here will have a idea?
The pre amp is a soundstage vacuum two preamplifier And I cant find any schematic on it is as well. I will post some before and after pictures of the components that were changed.

Thanks in advanced !

hi!

Here is my audioscope project - just because I like uncommon methods to visualize sound
Some time ago, I used a similar circuit as an optical gimmick in an EL84 SE tube amplifier. (With a smaller and round crt YouTube ).

It consists of the electronics out of a 1,77" viewfinder from an early 1980s video camera. I don´t remeber the camera brand and type where it´s teared down from, but it should be easy to find something similar for little money in the Bay.
Newer camera types usually are downsized and contain less impressive CRTs.

After reverse engineering the viewfinder, put it into operation carefully with the right connections and voltages. Just a small mistake in your considerations, and it burns... I speak from experience 😀
The horizontal deflection coil is disconnected from the circuit, the vertical stays untouched. I´ve integrated a terminating resistor in place of the x-deflection coil, to keep the circuit running.
With a small audio amplifier module like PAM8403, it´s able to modulate the CRT deflection.

This procedure is easily reproducible and not critical, if you manage to analyse the viewfinder electronics right 🙄


-> video: YouTube

Having perused as many Citation 12 threads as I can find looking for a answer i have decided to post it up here.
Most of the threads are aged. They discuss the Pass Mods mostly which at that point it's something other then a Citation by H/K. I have been hoping to not go that route. This Amplifier sounds great as is when playing. First fired up by me it crackled loudly on power up. I have been looking at Variacs since then. Over time it has diminished to a small crackle which persisted on power off on the left channel only. The right channel is quiet on power up or down with exception of the mild thump this type of topography is known for. That is not bothersome.

My attempts to quiet the crackle proceeded to do a electrolytic replacement. First the Power caps and input coupling caps on the chassis. C1,C2, C3,C4,C5,C6, It went well but the crackle persisted.

Next were the 8 caps on the main board. This entails another lesson. Before replacing them had I had enough light to see the cracked resistor, 27ohm 2w
R738. It was the only resistor on the board with a gold band which tells me it had already been replaced once.

I got real lucky and found a direct replacement. I had already replaced all the Ecaps. c703 & 4, C705 & 6, C707 & 8, C 711 & 12,

After replacing all this I adjusted the bias to 30mv. As close to 29.6 as I could. Did the crackle go away? no.. Just the left side. but it plays great and sounds superb.

Of note are the bias pots positions are much different. The right channel is 3/4 across the range. The Left channel, with crackle is only 1/4 across the range.

While playing I feel heat coming from one output transistor. I make it out to be Q4, which gets its input through R736.
This is where I seek some guidance. looking at the schematic is there a likely suspect heating up both Q4 and R738, which goes to ground.
The trim pot is also in this leg which is also getting it's voltage from Q3. My first suspect is R732. Any other suspects? I have yet to take voltage readings. Thanks to whoever may assist.

For Sale: A DIY JC-2 Preamp that was built years ago. Case is a Chinese jobbie that is actually pretty solid and professional looking. Sounds great and zero issues.

How about $150 + shipping or pick up in West Sub of Chicago?

I am wondering if there are any problems building a 2.5 way system with different upper and lower midbass drivers. Using the natural baffle step design by running both only at lower frequencies, but one of them being of a different type. This is an issue of necessity as I can't find any more of the Focal 6W 4254 drivers. However, I was thinking that many manufacturers probably design similar designs using an altered lower bass driver better designed for low bass. While I don't have that ability, I could use something like the Dayton Reference 7" midbass. Another option would be one of the 6.5" woofers with extreme amounts of xmax, such as the exodous EX-6.5 woofer. Let me know if you see any problems with this. I really like the sound of my Focal towers at the moment, but I can't deal with the ridiculously low efficiency. It has killed dynamics and max output too much.

Hello ,

I have a well preserved Sony PS-X65 but is defect.
So , motor don"t spin , light are on , 33 is present but don"t change speed , Locked is missing , no other function at all.
If I put a record on platter and move arm at the middle of the record , after pushing Power On button , the arm is moving back to suport.

What voltages I already checked and seems OK :
- from PS the + / - 31V are OK
- from IC101 the 5V and 11V are present and OK
- from IC 108 all voltages are according service manual (+ / -15V on pin 4 & 8 and 0V on others pins)
- from IC107 all voltages OK
- from MB8841-327 there is 5V on pin3
What voltages are not OK when Power is on:
- Q110 at B= 0,033V
- Q112 at B=0.2V
- Q111 at B=0.005V , C=3.56V , E=1.37V

Hope the MB8841-327 is Ok....
New electrolytics for main board are ordered for recap.
Can somebody explain me what is wrong here?
I attached mainboard and block diagram from service manual(schematic seems too big for upload but I will try somehow to shrink it).

Regards,
Bogdan

In a 3-way design, if the crossover point for midrange was selected around 200-2,500 Hz, what is the different between using 4 and 6 inches driver? As the frequency response of both drivers can be covered totally in that range. Thanks in advance

Hi all, I am new to this forum and so far it seems very interesting.

I often have to service Crown amplifiers and I wonder if anybody knows for sure what output devices are used.
I recently had a MA5000VZ and a MA3600VZ to fix.

Original devices for the 5000VZ were, according to the manual:
PNP 103285-1 and NPN 103286-1 but on one of the channels, I had also a set of PNP C8188-2 and NPN C8187-4

In the 3600VZ I have the same C8188-2 and C8187-4 pair.

Now I know these transistors are made by ONSEMI, I use regularly MJ21195-96 and MJ15022-23 that YORKVILLE SOUND uses in their amplifiers, and the crown transistors have the same pattern, and same batch number format.

Anybody can tell me what motorola (onsemi) device his hidden behind these strange numbers?

I searched the forum for more than an hour and there is a lot of speculation about using different types like the MJ21193-95 or the MJ15024-25, but nothing very conclusive 🙁

I have easy access (and cheap) to the MJ21195-96 and MJ15022-23 because of Yorkville, the transistors from crown are almost US$7 each... it hurts.

Another question:

I see from the datasheet that the MJ21195-96 have basically the same specs, except for a slightly higher gain and SOA, than the MJ15022-23, but one says uses the "perforated emitter technology" while the second are "powerbase"...
😕
Anybody can shed some light on this?

Thanks for reading me and sorry for the long post.

Hi,

In LTspice the LT1028 and LT1128 models don't have the compensation pin.

I remember seeing a schematic here with a LT1028 having that pin.
Does someone have the according model or does someone know where to find it?

Thanks
Gerd

Hello everyone,


I know this has been done to death, which is exactly why I'm unable to sift through the interwebs on this one. There is simply too much.


Here goes. I own an older Linn LP 12 with a Valhalla that I don't use very much. It has a Linn Troika MC. I had to replace the Valhalla a while back, but shelved the unit.


I reconnected it over the weekend. As the amplifier does not have a MC input, I use a Pro-Ject Phono box DS+ with amplification set to 60 dB. The amp is earthed.
Unfortunately, it hummed like a SOB. I started searching the 'net, and it appears to be a problem that's been around for decades. Funny, it hadn't bothered me when using direct amp connections (different amps). Or at least I think it didn't. Equally unfortunately, the solutions proposed in many many posts on various websites and forums sound like snake oil proffered by people who seem to lack a basic understanding of electricity.


So I opened it back up, and noticed a really funky earth/ground arrangement. The ground wire from the plug is connected to the metal cross brace where the Valhalla is mounted. OK. There's a thin black wire connecting the metal bearingplate to the brace. OK. The signal ground is run from the arm plug outside with the RCA's for connection to the phono pre-amp, which is also standard fare. But now, there is a small black wire with an eyelet - I assume is the arm ground - that is also connected to the chassis ground, which I find mightily strange. Especially since the arm is mounted on a wooden armboard and thus isolated from the metal frame. As soon as I disconneced this wire the hum all but disappeared. When I disconnected the signal ground from the phono pre-amp it became very quiet.

I am now contemplating extending the 'arm ground' to go outside with the signal ground and both connecting them o the pre-amp to there is equipotential on everything coming from the arm.


Your thoughts ? Thanks, Pete

Hi All

I'm looking for a DSPBoard with ADAT out (8-channels) to replace my MiniDSP, does it exist?

Best regards
Johan

Is Vishay Dale resistors become something you can't get anymore?
I have searched in several component shops but mostly are they not possible to get or if you can, you have to order them and wait many many weeks or month until they get made, other is no longer in production.


Second, are the right for me? I have read that some think thay make the sound clinical and is perfect for an step attenuator because there "no sound" but if you are looking fore something musically, they are not particular great.

Howdy folks,

Ive got a 95,000uF / 15V electrolytic cap that I suspect has gone off-value and I need to measure it. None of my meters can handle a value this large, so I need a technique. Heres what Ive got so far:

0.095F × 1000R = 95 seconds time constant.

I charge the cap to 15V, apply the resistor and start timing until the cap falls to 0.63 of Vo (9.45V), which takes around 90 sec. I take this to mean the cap is a bit down in value, but not bad - maybe 5% off?

But I dont think my procedure is right.. what are the correct numbers / calculations? Because when I charge this cap direct from a 15V supply (no resistor), it draws near zero surge current - and I'd expect quite a surge - like to the limit of the 1A supply.

Thanks.

power supply atx Jetek L480 measures 7volt violet wire and 5volt green wire, I have checked the feedback circuit to remove all the new replacement (photocall, diode zener, TL341, 3-pin lights, even resistors increase the value or decrease The value before and after the photometer and the corrective lamp of purple wire voltage still produce a voltage of about 7volt) but the output of purple wire is 7volt, the remaining wires are only 7volt purple wire, how to lower power The purple wire from 7volt to 5volt ? If any of you have this schematic, please share it with me, see the attached image.

Hi, this is an amplifier I designed a while ago in conjunction with a few members here on the forum. I finally got around to putting it on the PCB and it does not seem to work.

I used 8050, 8055, BD139, BD140, TIP41, TIP42 transistors and running +/- 20v into a 8 ohm speaker. It sounds very low output and very distorted but when I disconnect power there seems to be a volume boost.

I ran the sim at 2 ohms load (I think its more realistic for a speaker?) and found omitting the output transistors emitter resistors improved stability but did not help the sound quality when I modified the board.

Any thoughts?

power supply atx Jetek L480 measures 7volt violet wire and 5volt green wire, I have checked the feedback circuit to remove all the new replacement (photocall, diode zener, TL341, 3-pin lights, even resistors increase the value or decrease The value before and after the photometer and the corrective lamp of purple wire voltage still produce a voltage of about 7volt) but the output of purple wire is 7volt, the remaining wires are only 7volt purple wire, how to lower power The purple wire from 7volt to 5volt ? If any of you have this schematic, please share it with me, see the attached image.

Hi,

I have acary SLA 70 amp. the 5AR$ arcs a lot. I was told that the problems was due to the large fliter cap (1100uf). Some said that this can be solved with a CL90 thermistor? Where should I put it?

Thanks.
Manner

I have written some pcbcad software.
I am getting some customers having error messages when they try to run "schematic definitions"
The favour is downloading the software and running "schematic definitions" from the launcher screen.
Sometimes there is an error could you tell me what the error message is ?
The software works fine on my PC's.
Just leave security code blank.
http://murtonpikesystems.co.uk.servepreview.net/pcbcad51demo.html

Just curious, but has anyone every tried building Class A amps with logic level mosfets? I am assuming that a lower Vgs threshold means potentially lower rail voltage and hence less waste heat for same AC music output...
I may be spouting drivel....?

so the L25 board from eBay got delivered and I compared the item picture to what I received.



some components were different styles (no issue), the four large electros are 220uF instead of 150uF (probably not big issue?) but the biggest thing is the missing heat sinks on two of the smaller transistors.



in the original pictures the mini-heatsinks seem to be attached simply with white compound & the faces om the transistors on my board seem to have been sanded to form a rough surface.

so I am sure these are be required for proper operation without letting any smoke escape...

I have found self-adhesive ones: H0600 Mini PLCC Chip Adhesive Backed Heatsink - 10 x 10 x 10mm - Altronics

do these seem OK to use?

also - I am mounting on a bigger heatsink, should I reuse the soft transistor pads that came with it - or get new ones? also can I add some PC CPU paste to each one to improve the thermal transfer?

Hello at all! I'm going to complete my first headphone amp. The schematics report a 10kohm log potentiometer. I would install a ALPS RH2702. This value seem to be too expensive compared to 50K. Can I mount the 50K version? Maybe it up the volume too late?

Hello all:

I've embarked on my first serious mission of constructing a SE tube amplifier and I'm running into a few dilemmas. With time and deliberation I could probably figure them out, but being stuck inside with little to do, my ambition's getting a bit feverish.

My configuration that I'm attempting to use is a 6550 at 300V driven by an E88CC in an ultra low-gain setup at 80V (I planned everything out so that the 6550s would be driven to full power by around a volt of input at the preamp stage). The output transformer that I've planned on using is the GXSE10-2.5K.

The PT transformer that I've been looking at is the Edcor XPWR221, but I'm worried about using it for a few reasons:

1. The 250-0-250 rating of the 221 is close to what I need for the 6550, but I need to use a resistive voltage divider to bring it down closer to 300. I also decided to use another resistive voltage divider on the B+ line to load the E88CC. Both of these voltage dividers run between the B+ line and ground. The way I'm doing this scares me a bit, as I am not sure if the voltage divider lines will load the power transformer too much or even if my methodology is sound in the first place. Would I simply use high-rating resistors to prevent excessive current, or is there a better way to step the voltage down that I'm not aware of?

2. I've planned for this to be an easy college amplifier to go with a pair of R-51Ms, which means I'd be running current through two channels. Does that mean that I'd have to cut channel current down to at most 65 mA (as the 221 is rated for 130 mA)?

For the 6550 I've set the bias to -15 V, and according to my load lines the max current draw is ((B+) - bias) / (transformer resistance) = (285/2500) = 114 mA. Now the load lines say that the quiescent plate current is roughly 130 mA. For the E88CCs (running at 80V with roughly 5000 ohm load), the max plate current is about 15 mA. Adding those together brings 129 mA, which is very close to the power transformer's max current rating. Factor in the voltage dividers and the second channel and we're talking way over 130 mA (...right?). Meaning the transformer will probably die.

Given that I'm doing all of the math right (I am not trained to do this, just a high school senior that's bored and that's read all the safety precautions), I'm going to need a pretty meaty transformer, or I'm going to have to change a lot of things about this amp. Now, maniacs, what can you tell me?

As I ponder different feedback methods, another one has popped up. I have not searched so if this has been covered, my apologies.

In our general avoidance of pentodes, we may be missing a better way to introduce feedback through the "other" linear element. The Supressor Grid as used in a true pentode like an EL34. G3 was used for AVC in the past as an easier and more linear way to introduce compression than using other methods. Supressor grid modulation was used in some AM transmitters. It has been mentioned that the screen grid is less than linear for introducing feedback.

I have seen an EF86 used with G3 RC connected to an audio amp for supressor grid modulation.

Could this be used as a linear way to use the UL feedback tap? This grid may use RC coupling instead of a direct UL connection. Could some other feedback loop be used to better advantage than the more commonly seen ones? Plate to g3 without the need for a high gm driver or input transformer as in plate to g1? Voltage feedback from a pot across the output transformer primary, giving a variable % feedback?

I have not thought these through, just tossing out suggestions. The more knowledgable and experienced of you think way faster than I do.

I’m looking for a pair of TW29BN and a pair of MW16PNW-4. Let me know if you have either.

Hi,
I've just finished putting an E834 clone bought off the bay together.

Powered it up for the first time tonight with a single "sacrificial" (noisy as hell) tube in it to see what would happen.

Now the filament voltage is a bit high, and I need to adjust it. What surprised me more is that when I flip the switch, the tube light up like a lightbulb before dimming down to a more normal orange glow.

I am guessing this is due to the lack of a soft start, but is this normal, and if so, is it going to be detrimental to the life of the tubes I'm going to put in it ?

Thanks a lot

Sebastien

I have a CR1020 and when I first turn it on and rotate the volume knob the speakers produce a loud cracking noise as I rotate it, as if the pot is dirty. After several attempts at spray cleaning the pot the noise is still there, and I discovered it only does it for a minute or so after I turn the unit on. If I turn the unit on and wait about a minute, then rotate the knob, there is little to no noise at all. Is this an indication of something else, such as caps or resistors in need of replacement? I only ask because the noise is almost non existent if I wait before rotating the knob, thinking something is warming up or charging up in that period.
Thank You in advance for any information that leads to a possible solution.

I have two Sumo Polaris I amplifiers. Is it possible to mono bridge these amplifiers? They will be powering Magnepan LRS speakers. I am new to this and I don't really have any idea nor can I find information on this topic. Thanks!

Hi all,

I took a gamble on this rare V-FET beauty recently and I'm very happy I did! IMO it's beautiful looking and it sounds absolutely superb.

It was sold with the caution that a tech believed at least 2 of the 4 NEC 2SK70A's were blown and it's missing the serving tray handles so as such I got it for cheap; I figured worst case is I could re-purpose it for spare parts. Turns out all of the O/P's are fine and a tech in Japan had already recapped it excluding the mains.

Anyone have experience with this amp? I've searched and haven't found much of anything as far as the SM and Sch goes.

There've been many discussions over the years about large CD speakers, but there hasn't been much about how to integrate them into surround sound setups.

My case is one that would likely be similar to many others,

The LR channels are 12" woofer + 12" waveguide (SEOS in this case).

I have numerous matching satellite speakers with 4" woofer, 3/4" tweeters. Tweeters have little waveguides.

I also have multiple matching drivers that can be used to make a center channel. 5 1/4" , 4" , 3" , 1" tweeter , 3/4" tweeter. All from the same line as the satellites.

In my case it would be 7 channels. L C R, two rear surrounds, and two width channels (left wide, right wide)

How do CD waveguide speakers interact in a surround sound environment?

Is a non-CD center channel going backwards? Should one make a CD center? I only have space under the TV, so something like a SEOS with 5 1/4" woofers on each side?

Most receivers have room correction these days. In my case Audyssey. This should likely match the levels since there's such a difference in sensitivity. I'm not sure if it brings down the LR, boosts the others, or both.

Thoughts?

So here's an interesting old circuit Page 52.

https://www.americanradiohistory.com/Archive-Radio-News/Radio-News-Specials/Radio-&-Television-Hi-Fi-Annual-1956.pdf

Why would you put OB2 volt regulators on the grids of the 300Bs ?
Never seen that before. Seems out of place. The article mentions they're for protection.

I recently just finished a headphone amp. It is a clone of the El Estudiante from wtfamps.com.

I have tracked down a noise issue that is preventing me from calling this amplifier done.

When I touch the volume pot (ALPS 100KAX2 100K Ohm Audio Taper Stereo from PartsExpress), there is a lot of noise or hum on the output.

At first, I suspected the circuit was not earthed to the chassis properly, because the noise got louder when I touched the metal of the chassis. I spent a lot of time ensuring that the chassis connection is not the problem. After much trouble shooting, I know for sure the culprit is the volume pot.

If I remove the volume pot from the front panel, the chassis is no longer reactive to my touch. However, all I need to do is touch the metal shaft or front of the pot, and the hum get loud.

I checked for continuity between the ground pins on the pot and the shaft and there is none. If I run a jumper from the metal on the pot to the star ground in my amp, the noise goes away and the circuit is dead quiet.


How can I remedy this? There's no easy way to ground the metal on the pot, solder won't stick. Are these pots supposed to be internally grounded?

I converted one of my old 150WRMS irfp240/9240 amps to have a depletion mode mosfet front end in the LTP.

I started with a 2SK170 front end but my rails were +/-45VDC which stopped that. So i had to search around and found some Microchip depletion mode mosfets at RS Components which work up to 300VDC.
Luckily, I checked pin out and Micrchip mosfets are opposite way around to 2SK170's so have to rotate them 180 degree's on my pcb which was made for 2SK170's.
Got my pcb's made at JLCPCB. Built up the first one and powered it up.
It was terribly distorted. So I set output DC offset to zero.
I then turned up bias to give about 10mA and the previously distorted sound transformed into a great sounding little amp.
The voices are very clear and I can hear what the words are in songs I couldnt previously.
So been a good project and very happy with it.

Everytime the bias reach 10mv, the bias raise itself, it jump to 20 or 30mv right away.
View attachment Simetries Folded Cascode New Com amp.pdf

Recently I've been the benificiary of a number of friends "lost" speakers. In the past three months I have received (in various states of disrepair) :

a pair of WW Scott Pro-100's (w/ the 15" woofers and the selectable crossover - wicked cool compression tweets)
a pair of EPI 100's
a pair of Kilpsch KG2's
and
a pair of original 1975 Bose 901C's (complete with packing boxes and manuals as well as the active equalizer)

And I'm on the threshold of being the new home of a pair of original one-owner Klipsch Heresy 2's

What the heck do I do?

That's a pile of restoration work on speaks I really want to hear! However, that'll put my own DIY work on hold for... well, forever?

I suppose it'd be neat as hell to to restore all these old soldiers but then that'd be what I do. Period.

What do I do?

Carry on my own design work or pause to make these legendary thingies go again???????

If I don't who will?

Regards,
Tom

Hi,
so I have some questions that I hope someone can help me with, or just possibly point me in the right direction to find them.
I have ordered 2 DSP units from 3e-Audio for a future 3-way speaker setup, but have some concerns how to implement them in the best way for my use.

1) I have two sources for audio, TV (optic), PC (anything possible except Bluetooth), so my first question is regarding input choices, is there any easy/good ones that is simple to connect to these 2 boards simultaneously?
I'm not sure if source select is even possible on the DSP units, so might need that anyhow.

2) Volume control, there is a board for each of these modules, but is there an easy way to control both simultaneously? Perhaps something to some other DSP unit will work for this... 😕

As it is right now, I've got an amplifier that I can separate the pre-amp and amp on the back, so all is not lost if it's hard to implement. I also bought a (generic) DAC recently that I could use to get the optic output from the TV in to this older amp (RCA output), if I need to use it for source and volume control.

3) I have not decided yet on amplifiers for my project, is there something I should look for or avoid? My concerns are that this DSP has balanced outputs, and if the output is strong enough to drive amplifiers that don't have op-amps.

Sorry for my lack of knowledge, I'm not afraid to do some research of my own, but it's hard when you don't know exactly where to start looking. 🙂

Oh, and anything more precise than soldering cables is out of the question as my hands shake pretty bad.