I was visiting a friend who sent me home with a broken amplifier out of a pair of powered column speakers. It's an Acoustic Research Hi-Res Series AR1 and the Intertubes and the current website for the manufacturer haven't been forthcoming with a schematic. I can't even get a user manual to understand just what I'm dealing with (it's not as simple as line in and speaker out).

Initial complaint was, unit wouldn't power on. Internal 5A mains fuse was blown. Checked toroidal power transformer secondaries and they're all fine.

There are three boards; one is a power supply board but all it really does is rectify and filter the +-130V supply for the power amp board and route the other PT secondaries to the other two boards. There's a preamp board that gets an 18VAC secondary and the power amp board gets two other 18VAC secondaries that seem to be turned into +-15VDC or so on the power amp board. I think the power amp board is a biamp. The power amp board seems to have some sort of standby circuit on it. There are four pairs of TO-220-case transistors bolted to the metal back panel and then there are two pairs of big ol' honkers in what I think are TO-264 or TO-3P cases. I ohmed the big ones out in-circuit and discovered that one of the two NPNs, a Toshiba 2SC3281, had dropped the "semi" from "semiconductor" and was acting as a pair of jumpers.

I removed both the NPNs, established for certain which was the bad one, left it out, and soldered the good one back in. When I applied power, the mains fuse did not blow but what was weird was that the amp itself - not speakers; no speakers were connected - was making a very pointy-sounding 60Hz noise. I turned the variac down to supply about 50VAC, just enough to have the onset of the noise. I have tried but so far failed to determine what component(s) are vibrating to make the sound, but I got out the scope and saw nasty waveforms on the power transistors.

This leads me to suspect the +-18 power supply for the power amp board and sure enough, if I disconnect those PT secondaries the noise stops. But before I go any further I want to ask if the noise could have anything to do with running the amp with one of those two paralleled NPNs missing. I'm not giving the amp any audio input and as I said, no speakers are connected as of yet. I'd like to avoid making one purchase of a 2SC3281 just to turn around and order more parts separately.

Greetings,
I’m building my first electronics project, an Amp Camp Amp V1.6. I’m good with mechanical systems, but electrical systems and circuits are a whole new game to me.
I’ve joined looking for help on the build after a few hiccups. On initial power up and running first signal through the amp, it turned out I was missing the left channel. I found that I overcooked the front power switch and had a bad solder joint on one leg of the Q2 mosfet.
Now I fear I may have fixed it and immediately destroyed it.
Anyway, I’ll dig into that in the appropriate forum/page.

n/a

SEAS Excel W18E001 High Resolution 6.5" (Cape Town)

A pair of SEAS W18E001 mid/bass drivers from their highly regarded Excel range. They feature a high-resolution design and an advanced motor system, making them well-suited for high-performance loudspeaker applications.

These drivers are as-new, with original packaging.

Specifications:
✔️ 6.5" (18cm) Magnesium Cone
✔️ Low-distortion motor system
✔️ High-resolution performance
✔️ Recommended for high-performance loudspeakers

Condition: As-new, with original packaging. Briefly used as evaluation samples.
Price: R7000
Location: Cape Town
Shipping: Yes. At buyer's expense

Hi... Thought I'd ask first. My Lynx PCIe card outputs a stereo balanced signal of +20 dbu (pretty hot). I want to run this to a Topping headphone amp with RCA inputs. I bought these adapter cables from Amazon and I included its wiring diagram (see pics)

Is it safe to connect this or do I risk damaging something?

Thanks

I may be getting a Heathkit A9 in decent condition with no tubes and a replaced power transformer soon.

I looked at the schematic and given my experience with tube amps and recently discovering how easy it is to do fixed bias instead of cathode bias, I may do that as it will improve the bass response.

Now in order to do another mod which is to increase the B+ cap value the output transformer connects to so that the amp can handle the bass better (did that mod and the fixed bias mod to a Magnavox AMP-142 and the sound quality improved a good bit) I'd have to go with a solid state power supply unless I go with a higher voltage power transformer, however losing the 5U4 will reduce the heat the amp puts out.

I can either use a lower voltage power transformer (may be replacing it anyways depending on what was stuck in there in place of the original) and a solid state supply or I can use the same voltage and add a filter cap after the diodes and a choke between the first and second filter caps to drop the voltage some and provide better filtering which will also reduce the initial surge current of the larger filter cap.

How much B- voltage should I have on the 6L6 control grids and what idle cathode current should I run them at?

That said if I'm reading the schematic right, there's no cap across the 6L6 cathode resistor. So one benefit of fixed bias which is getting rid of that pesky cathode bypass cap will not be realized so do I really need to mod it for fixed bias?

Now I've tested amps before with no cathode bypass cap and if I remember correctly that wasn't always the best option far as audio quality goes. I forget exactly what problem I saw with an amp that had no cathode bypass cap on the push pull output tube cathode resistor, but I know there was some issue.

I do know that in order to limit the effect of Miller capacitance I will need to replace the 1 meg volume control with a 100k volume control and I'll up the value of other coupling caps in the amp to reduce the phase shift at 20Hz to near zero as that will also improve the sound quality plus eliminate any potential bass instability issues caused by the phase shift. My way of thinking is if the phase shift is not there, it cannot cause problems.

As I typically do, I'll restore this amp to stock before making those two major mods just to see how well the amp works. That way I have a good baseline of what to expect from the amp.

EDIT:

It looks like I can maybe connect the line level input straight to the volume control as the tuner input uses a 1meg series resistor that connects to a 18k ressitor which goes to ground. So it attenuates the signal pretty heavily then steps it back up with the 12AX7.

Now if I do that and it works I'll install a 1/4" switched jack so that the original amp inputs can still function as designed when nothing is plugged into the jack.

Quoting a larger post will add a "Click to expand..." at the bottom, but when clicking on the Expand, for a larger post it would only show partial quotation which is often bewildering as it is not always apparent whether a larger post have been cut short.

If possible I would like to see a vertical scrollbar appearing on the right side of the quotation box when expanding a quotation, and why not on a non-expanded quotation as well.

Is this FFT analyzer still of any use? I can get one at a bargain price, although with blown inputs.
Perhaps a decent soundcard and a PC with FFT software is better. Opinions?

I have two of the following 3 cu ft sealed boxes.

https://www.parts-express.com/Knock...udio-15-Ultimax-Subwoofer-300-5024?quantity=1

I currently have a Cerwin Vega 15" woofer with cloth surround loaded in each cabinet.

While they work good and produce very clean sounding bass, they tend to run out of steam about 35Hz and using EQ to boost the output below 35Hz only makes them start to sound bad.

How well would this 15" driver work in those cabinets?

https://www.parts-express.com/DS18-...rbon-Fiber-Duat-Cap-4-Ohm-294-8072?quantity=1

Parts Express Staff Recommended Enclosure Volume
Sealed Volume 2.5ft³
Sealed F3 32Hz

If those won't work what subwoofer driver will?

The idea is to have an F3 of around 30Hz if not lower than that.

As per the title I'm after F3 PCBs.

Been out of the game a while and am sitting on the power JFETs.

It's time to build some stuff.

I'm UK based but if you'll post I'm interested.

Nick

I'd like to know what are the choices for a phase splitter on the input of a PP amp so it could be driven by a preamp with gain using RCA inputs. Amp in question is an EL84 in PPP triode, so 8 output tubes in all. Choices I can think of include....

• input transformer like 1:1+1 or 1:2+2
• solid state splitter
• valve concertina without the gain stage in front
• ??? something else

I'd like something simple and transparent that could be driven with a 26 DHT preamp in this case, but this is a universal application so feel free to talk around choices as much as you would like.

https://www.instagram.com/share/reel/_x8JicCLq

Interesting view into a Danley system upgrade of a studio
HRE-1s and tapped horns etc

it seems that i would need to parallel another pair of the bd140/139 transistors to drive 4 ohm load and i know that this circuit is completely pointless.

I just bought some vintage Heils (don't even have the ESS logo) and had previously built a cabinet with two RS225s in each wired in parallel. I was using Janszen electrostats on top but think the Heils have way more potential.

I am an audio nut but do not have a lot of crossover experience, only simple 1st and 2nd order types. One thing I did notice was how efficient the Heils were. They sounded really bright and think some attenuation L-pad will be required. I played them using a 40uh cap and some songs sounded harsh and somewhat hurt my ears, especially guitar distortion (Smashing Pumpkins). I have also seen threads about dampening the rear, I may try playing with that.

Many people say that Heils have no business being played below 1500hz or so, I am hoping perhaps my earlier versions can, and my existing RS225 crossover point will be ok as is, the inductor I bought for that was quite expensive.

Crossover design help would be greatly appreciated. All I would really know to do is use a crossover calculator and go from there. The Heils measure at 3.7 and 3.8 ohms.

I attached a few things:
•Schematic of the crossover I built for the RS225s, I believe I did a 2nd order Linkwitz-Riley and in looking at the values, and how the woofers measured in ohms, perhaps around 900-1000hz(?)
•REW sweep with the mic nearfield to one of the woofers (with my previously mentioned crossover) and then nearfield to the Heils (with no crossover but the sweep starting at 450hz).
•Pictures of the RS225 enclosures I built so you can visualize what I am trying to accomplish. I will most likely build a walnut block for them to sit on in the future.

Hello all,

I have a lovely Boonton Electronics 93A True RMS Voltmeter for sale

120dB range, Frequency response from DC to 20MHz, switchable response time, 115V or 230VAC switchable, mirrored scale, BNC input, tilting bail

Tested and working

Made in USA

Asking USD 139 but open to offers

Cheers, Ralph

Hello all,

I have a dead dbx 260 if anyone needs a donor for parts. It's a 220-240V 50-60Hz version. Powers up but doesn't boot, starts and displays the dbx logo before rebooting over and over. Dead!

USD80 plus shipping takes it

Cheers, Ralph

Hi everyone. Stupid question here. I have 4 Rcf LF15X401, can i use them for a 4th order bandpass? At the moment they are into a dual 15 horn reflex hybrid, maybe into a 4th order they sound better? Worse? Please help.

100 VA Toroidal from a Cyrus One Amplifier.
Outputs 23.5 VAC - 0 - 23.5 VAC

Asking €20,00

Hi All,

My name is David, I've been based in Prague for almost 10 years, and my journey with AUDIO started in high school.
Day by day I'm an IT Developer but occasionally I'm a DJ and also a consumer of good music and nice equipment.
I build my sound system from scratch just by learning from online and other members from different groups and forums.

Is there anything fundamentally better about a discrete r2r DAC as opposed to an IC?

Hello All. 30-year musician here, with a colored history related to amplification and electronic devices. I love to tinker with small engines and actually took an electronics course in community college long ago. I have enough solder burns to provide I've tried fix stuff.. sometimes I do it right. And learn more in the process than all the labs in a college setting.

I've owned 3 Fender Passport PA's in my life, and the only complaint was not quite enough power for the venue I played. But I always liked the portability and swoopy design. Unfortunately we plugged the 500 Pro into an extension chords at a backyard party, there was a loud pop and that was the end of that. As others of said, professional repair isn't cost effective in my area. A friendly mentor looked at it and said that he could go no further without a schematic. Others on this forum as well as a local (former Fender) tech says Fender wont even let the techs have the schematic. But I saw a thread here of someone who has one.
1) Are the schematics for all the models reasonably similar or do I need the 500 Pro schematic?
2) Anyone figured out a consistent approach to fixing the problem without successfully diagnosing it? (e.g. blinding replacing a bunch of transistors..?)
3) I have PD 250.. if some version of testing a working model against a non working model would help figure it out?

Thanks for the help,
EJ

Hi,

I'm working on a design for a mic preamp. The overall project is to build two different mic preamps, one with an input transformer and one using the THAT 1512 IC, mount them in the same rack enclosure with identical front panel controls and carry out blind tests between them. The aim is to see if people have a preference for either and indeed if they can tell the difference.

I've begun by working on the design for the transformer preamp. I would like it to

• Be as low noise as possible.
• Include phantom power, -20dB pad and phase reversal.
• Have a gain of 20dB to 64dB in 4dB steps (not including the pad.)
• Have an input impedance of approximately 2k.

The design at the moment has an 'impedance balanced' output which I believe is sufficient in a studio setting. I'm happy to be told otherwise!

The transformer is 1:6 so provides 15.6dB of gain and the op-amp provides the rest. The 75k resistor on the secondary should give an input impedance of 2.1k.

I would also like to include a clipping indicator (and possibly 'signal present') but haven't designed that yet. I'm a bit worried about being able to design it not to inject noise into the preamp.

I've attached a PDF of the current design. Any suggestions for changes and improvements are very welcome!

Thanks,
James

My last build was a closed subwoofer using a Dayton Audio Reference RSS265HF.

I like it a lot, but I want to test a setup where I combine the RSS265 with two 10" passive radiators to compare.

It seems like all subwoofers with this setup have a cube shape. Is this the optimal design, or is it used to make the subwoofer as small as possible?

I have found that the passive radiators should be installed on opposite sides of each other to cancel some resonances.


My first closed build




An idea I did play with for a ported setup - could skip the port and add a passive radiator on each side (adjust height..)

Hi all

I have had this tape deck for around 2 years and use it occasionally. Got it out recently. There was a burning smell and fusible resistor R544 had gone which connects to the motor that drives the take up reel and FF / RW. Replaced it and same thing happens again after a while - you can feel it getting warmer. R544 connects to 2 transistors X507 and X508 which I removed and tested - OK. Not sure where to go next.

Also, and bizarrely the right hand audio channel went as well. Not sure if directly connected. Tried to trace the signal path using service manual but struggling.

Any help would be appreciated as I want to rescue it.

Best Wishes

Hello Dyers, I`m looking for the best possible schematics for the above, I'm going to build a power amp in class A and I want to know, which PSU is considered the best, and why ? Thanks !

New guy here looking for advice, education, recommendations and community. I have a small collection of various components. My main system is Furman Elite 15 power conditioner, Isoacoustics zazen 1 tt platform, Technics SL 1500c, Hana ML cart, ProJect RS2 phono pre, Audiolab 6000cdt, Audiolab MDAC+, Placette active line stage, Mac 2100 amp, and JosephAudio RM25si Mk2 speakers. I also have a set of Acoustat Spectra 1100's, the only component bought new in 30 years. I'm looking for info on rebuilding or having rebuilt the Acoustat crossovers. Thanks.

I am a complete noob when it comes to DIY audio. Got a subwoofer with a broken plate amp. Instead of repairing the plate amp it looks like its cheaper and easier to build one with one of the class D amp boards from aliexpress.
Need some help with the same and that's how I am here..

I have always used JLPCB from Hong Kong for my PCB fabrication, as they offered excellent performance at an unbeatable price. Now, with the new tariffs and USPS suspending all Chinese shipments, what are our domestic alternatives that at least come close to JLPCB?

Where do you guys buy your LP12 parts? I need to start listening again (Ittok LVII, Valhalla) .

Hi, just looking to get some help and co tinue on an old thread about fixing the old rel t5 subwoofer. If you have one, could you come and help me out?

Hi, please, are toroidal inductors any good for building crossovers?
Like the ones in the link below.

5pcs Toroid Inductor 3A Winding Magnetic Inductance 22uH 33uH 47uH 100uH 220uH 330uH 470uH Inductor-in Inductors from Home Improvement on Aliexpress.com | Alibaba Group

Thank you

Hello hope everyone has a nice week-end !

I don't think one would want to load a cartridge with an electrolytic, but what do you recommend as the type or quality of film capacitor is best at this position? I would think quality matters here since that load is part of the "signal generator" circuitry, along with the load resistor.

Currently I use polystyrene, is that just overkill? Would a high quality polyprop work just as fine or the quality doesn't matter at all ? Although I didn't check I think teflon films are still in production, Solen maybe?

I'm guessing most current phono preamps use polyprops as the polystyrenes are basically extinct and a maker wouldn't use NOS stock on a new product.

Thanks for any insights.

-Joris

Hello everyone, I have been a keen follower for some time and quite often search for answers to the questions I can’t easily find elsewhere, here!
I particularly like vintage 70’s HiFi and have a growing collection which I must start to reduce as I am running out of shelf space!
Also recently embarked in creating my own self built amplifier and it has been both a great experience and a game changer for me, very decent hi-end sounds for bargain money and a little effort and learning.
Thanks for all your past help with the posts I have read.

After 6 years of mining, while doubting that this day would ever arrive, Pi opens for trading on a number of exchanges in less than 48 hours.
If you've mined in the past and forgotten about it, drop everything and KYC right now... IOU trading has the price @~ $75 currently.
Binance is not on the current list of exchanges, but it looks like they'll be listing Pi soon.

Hi,

Does somebody know what a double diamond buffer means.
They don't use a volume potmeter but I think they change the current of the balanced input pair.
Does somebody experiment with this kins of variable gain circuitry.
A friend of mine bought this amplifier and it sounds great.
I'm going to try to build something like this and see how it works and sounds.

Rob

Fun with op amps. I present, the "Bug". Stacking is nothing new but these stacked ne5532 op amps are playing very nicely with each other. Will have a vid with proper audio examples this week.
Login to view embedded media

I have for sale a

IAN CANADA I2S to PCM Conversion Board.​

It has all ufl pads soldered and tested.
I am asking 75 euros.
Registered shipping included in europe.

Hi, I've been tinkering with this subwoofer for over a month, and I can't get it to sound right.

I have desoldered about half of the components of the boards and I can not detect what is happening....

It is a Kenwood SW-505D subwoofer. It sounds very distorted, you have to select near full the volume to make it sound something low like a trapped fly...prf prf prf prf prf prf prf

I'm just an amateur without much knowledge, but I think I put my heart into it. I think, that the failure is in this board... any help will be appreciated, thank you!


The voltages on the HIP4080 are:
P1: 11.63v
P2: 12,14v
P3: 0,34v
P4: 0,011v
P5: (not soldered on board) variable around 0,520v with the volume at 0 and around (oscillating) 4,80v at max
P6: 6,21v
P7: 9,27v
P8: 5,18v
P9: 5,18v
P10: 11,64v
P11: 0,028v
P12: 0,028v
P13: 11,26v
P14: 0,011v
P15: 12,14v
P16: 12,14v
P17: 0,011v
P18: 0,39v
P19: 0,009v
P20: 0,010v

IC3
P1: 9,90v
P2: 6,57v
P3: 6,59v
P4: 0v
P5: 5,814v
P6: 5.814v
P7: 6,051v
P8: 12,13v

IC2
P1: 6,059v
P2: 6,059v
P3: 6,055v
P4: 0v
P5: 6,059v
P6: 6,059v
P7: 6,21v
P8: 12,13v

IC1
P1: 0v
P2: 0v
P3: 0v
P4: 0v
P5: 6,103v
P6: 6,059v
P7: 5,161v
P8: 12,13v

This sale is for Jos Vaneijndhoven attenuator which was sold as a diy kit and later went commercial. It's a relay based attenuator with input selector, both which can be remotely controlled. The manual can be found here.
Because I wanted to be sure that both channels measured absolutely the same, I've ordered 10 additional RN60 Dale resistors of each value (120 total) in order to match exactly the values with my Fluke meter so I'd have identical channel volume. I'm offering these resistors too with the attenuator (most of them are there, about 110 RN60 resistors). I also added a small transformer to power the circuit.
It's of course in full working order.

I'm also offering a chassis for this, as it was used for a small project now cancelled. It's a diy but it's very decent looking. I replaced the used bottom with a new one, so it is like new with the exception of front and rear plates. The rear is been cut for neutrik rca sockets, rca and power. Because of it's weight I'm giving the option to buy the attenuator seperately.

Edit: Attenuator SOLD only chassis left wondering what it's fate will be.

Hello, I noticed I no longer have a signature. Regards.

I've found 24 x Toshiba 2sk170 BL when I tidied my workshop, there is a mixture of straight and kinked legged.

£30 posted in the UK anywhere else add £6

I recently got this Jolida JD-302b. I briefly auditioned it and fell in love with it. Seemed like a great deal at $450. I've only recently begun auditioning tube amps and need help identifying the mods on it. It clearly defers from the schematic that I've found. I'm reluctant to take it back to baseline as it sounds sweet to me. I think it goes toe to toe with the MC-240 and the Dynaco St-35 that a friend brought over. I dig it. I'd like to know if it's going to eat tubes or is potentially dangerous. Any help for a newb would be greatly appreciated.

Well, I’m new here. Grew up on HiFi with my dad playing records. I’m 54 now and I got back into HiFi during quarantine Covid time. In the last 5 years I’ve been buying selling tweaking gear. Here to learn! Cheers!

Hello Everyone,
I have an Adcom GFA 585 that has an issue with DC offset when shut down. I am aware of the capacitor issues and recapped both input boards after sonic cleaning both boards multiple times after following the instructions from several threads on this site. My issue is a little different than the other threads though and I was hoping someone could help me methodically figure out where the problem lies.

On startup, the right channel behaves as it should and settles around +/- 5mv dc offset. The left channel starts a little higher, maybe 200mv and then settles to vary around +/ - 10mv which isn't bad either. However, when I turn it off, offset can jump to between 6-20v positive dc on the left side. The output of IC101 when running is about -1v which seems pretty good, but when power is cut, it jumps to -10 to -11v like it is trying to balance the DC but doesn't have enough juice.

Based on how it runs pretty well, it doesn't seem like it is input transistor or IC101 related, so it makes it difficult to pin down the issue when turned off. How would you go about narrowing down where the issue is?

Amp design is borrowed from an old D Self design with newer transistors which are currently available from DigiKey.
QSPICE simulations Sine Wave and Square Wave are good but not Bode. I'ts unstable. After much failed 'twerkulation' to move poles and zeros, I've chosen to seek suggestions from those with more experience. Suggestions welcomed.

At sometime in the past, I read that certain axial film capacitors degenerated over time. If I remember correctly, the end caps of said capacitors were identified by colour. Unfortunately I cannot remember what that colour was.

I have some crossovers from Electrovoice which each contain three axial film capacitors - 2uF, 12uF and 21uF. I suspect they were constructed circa 1970. As mentioned in the thread title, their end caps are red in colour. Should these concern me?

As far as I can tell the variable resistors in the crossovers do function but how they affect the sound seems quite subtle to me.

The speaker system in which I installed them is a 3 way using EV 12" woofer, EV MR10 horn midrange and EV T35 tweeter. I cannot say that I am thrilled with how the system sounds. My perception is they are overly bright and adjusting the tweeter and midrange variable resistors produces a perceptible but negligable change.

The thought occured that perhaps those film capacitors are out of spec under load. The readings I obtained from a DMM with the capacitors out of circuit were within tolerance so I left them in place.

Since they are 55 or so years old, are they due (or past due) for replacement?

Hi,

I am working on a Classe CAV-180. I wanted to ask this question to Classe' Tech support but they seem to be out of business.

I got this amplifier as dead. I found that the slow start 10 ohm 50watt power resistor was the problem. I temporarily replaced this with a 15 ohm resistor and the amplifier starts up and sounds great! There is a short beep noise for say a 100ms when first pressing the power button. I am not sure this will clear-up when I put in the proper resistor.

The main question here is: on page 11 of the service manual (attached) they describe several updates. I don't know what issues these updates apply to and if I should do them?

This one is troubling me.
"4. On board B2E2X (5 PCBs), make sure that Q1 and Q2 are part number 2SK79 and 2SK216. They should be mounted on a small aluminium block, which is mounted to the chassis (see following pics). If they are printed as ECX10N20 and ECX10P20, replace them, using the following guide."

It seems the ECX10N20 and ECX10P20 are very good parts so why would they want these changed?

Thanks, Gary

Some time ago, I decided to build Tony Gee's Calpamos speaker, so I ordered a set of crossovers and started gathering the remaining parts. Since there doesn't seem to be much documented about these speakers here on DIY Audio, I thought I'd share my build.

Just within the last few weeks, I started cutting wood to make the boxes. The first challenge that I ran into is that 2x2 wood stock recently became a bit of a challenge to find. My local building supply store still had some stock of 2x4s at pre-pandemic pricing, so I grabbed a few and split them down the center.

It was a bit of a trick to make sure that everything remained square as I glued up each square and put them together to make a 3D box. More than one of my straight and true 2x4 boards decided to warp and twist a bit after being split down the middle. It took a bit of extra time checking and dry-fitting everything with my T-square before adding glue.

I also bought some caster wheels and made a 2' by 4' dolly so I could move these around the garage a bit more easily. After I built the frames, I realized that I didn't stop frequently enough to make images of my progress.

Hello there!

This is yet another amplifier noise thread 🙂 I guess you have seen plenty of them here and I beg your pardon to just be the next one you see...

I have been given an old Technics (National Panasonic) SU-3600 in nice state (except for some scratches and two missing knobs, but I can excuse this as it is a barn find and was for free)

I cleaned the beast and double checked everything after putting some new thermal grease and setting bias and IQ, and when I first powered it and listened some tracks I fell in love with it as it has much more depth than my other amplifiers

After further listening to it, I noticed that there is a background noise which is very distinctively composed of two components, a humming one and a hissing one... I guess the humming one would be some 150Hz and the hissing one would be some random noise, maybe thermal

One thing to note is that some of the noise is highly attenuated when I reach the middle of the master volume setting, so it seems that it is somehow related to the preamplifier rather than the power supply itself

As this is a somehow unobtainable amplifier at the moment I would like to make as little change as possible to it and get advice from other people before starting to replace all capacitors and co... they all seem fine and the sweet spot in the volume control makes me think that they may not be to blame

I'm suspecting the area around TR107 and TR207 to blame, maybe some resistors that would have gone out of range...

EDIT: to be noted that IQ and bias took quite some time to stabilize before I was able to get the specified values... trimmers have been lightly cleaned with kontact60 on a cottonstick

I attached the schematic for support, would some more experienced guys be willing to help?

This is a really nice amplifier, quite rare, which is a barn find, so it has become a duty for me to restore it to a hum-free state 🙂

Thanks in advance!

Have 2 Arylic streamer dacs and will throw in rack for it if you want. These little guys are feature rich and sound great for multi room setup. I’ve got them plugged into a multi channel amp. Inside it’s linkplay chip so it works with WiiM app and even groups with WiiM devices. All three plus rack $125

Is anyone familiar with the "TPA6132 Differential-Balanced Stereo Headphone Amplifier Board Single End Output" manufactured by Huanya?
It appears a lot on eBay. The link is: https://www.ebay.com/itm/264669105325?_trksid=p4375194.c101949.m162918
On the underside of the PCB it reads "+6 db: R1 R3" What on earth am I supposed to do? Butcher the board?

This happened with Both F5m and just now with F6. adjusting bias gently
then the Bias just runs away and blows the mains fuse, and with my F6
one Mosfet,

I'd like to see how close (far) a design using simulated data is (design without measurement) to one with actual data. The problem is, I have seen the actual data and don't think I could design a crossover with the simulated data without at least subconsciously accounting for some of the differences that I have seen.

For anyone interested, help me simulate a crossover using the attached simulated data. This a a two-way with a 6-1/2 paper cone woofer and a 1" silk dome tweeter. The data incorporates the diffraction model for the baffle, but is on each driver's axis. So, you will need to use minimum phase data, set the woofer at -165mm y-offset and something like -18mm z-offset. [Tweeter data is .frd and merged woofer data is .txt] Traced tweeter impedance and simulated in-box woofer impedance are also in the zip file.

Which one is good in sound quality and loudness. xy-p15w or tpa3110

For sale Automatic Electric Europe (AE Holland) 5K to 6 Ohm single ended potted pair output transformers.
Good for the following tubes like 833, GU48, 2XGM70,…etc.
Primary (Anode) current: 300mA, Primary DC resistance:110,7 Ohm, Primary inductance: 19.8 Henry.
10-30,000Hz.
Each opt 13,4kg.
Size: 15cmx17cmx15cm
Slightly used by me, in very good condition.
AE 4:1 Interstages are also available.

Hi all,

Is anybody using the FNIRSI 1013D 2CH Oscilloscope? It's a sub-$200, so the price is OK. I'll be using it mainly for t-shooting and measuring audio tube gear, so 100Mhz is plenty. Other than that any input on pros/cons would be greatly appreciated!

thx much!
/DL

Hello,

For sale is new, unused Burr Brown PCM63-K DAC board.

Proven configuration; CS8412, SM5813, 2x PCM63-K on digital side, 2x AD797, 2x OPA177 on analog. SPDIF input, dual mono audio SE output. Analog audio is PCB routed dual mono, so ideally it can use two power supplies (2x15V DC) for audio plus..one for digital. Of course simpler power supply can also be used.

Board is new, only assembled and tested. Works flawless and IMHO sounds just like good PCM63 DAC should. Dimensions are 16 x 10, 5 cm. Quality double sided PCB with separated ground planes. I can also drop in 2-3 empty PCBs for matching power supplies.

Board is laying in a drawer waiting for housing for too long, so if anyone is interested,

Price would be 200€ plus shipping. PayPal (friends&family) preferred.

Regards, Davorin

Recently, I wanted to build some compact and battery-operated headphone amp (Just for fun!!!)

Then I browse thru this website: TCAAS - The Class-A Amplifier Site and saw JLH1969 class A schematic and realized that I hadn't build any OTL amp yet.

I've been building some decent design amps and those topologies all utilize dual-rail power and dual battery operate amp is problematic (don't like the virtual ground design)

thus I saw many scale-down versions of JLH1969 class A amp (This is the one particularly good for low voltage operating JLH 1969 battery amp) and simulated it.

It's turned out very well!



Thus I went to the local electronics store bought some goodies and start build on the perf board

Also found a small case and rechargeable Li-ion 9V battery for the amp


It sounds pretty good with my DT990 pro 250 Ohm headphones!

Although I have finished this project I've some questions want to ask.

1. I know the output capacitor in OTL amp is to block circuit DC from the headphones but I still measured some 10-15 mV only at the left channel. This makes tiny noise at the left channel that sounds like scratching ear. I've swapped many output cap and didn't fix them. Never occurs at right ch tho.


2. I use MJE340 as my output stage device and quiescent current is set at nearly 70 mA. MJE340 works at about 300 mW.
I saw the datasheet said the Thermal Resistance(Junction−to−Case) is about 6.25 C/W. Should I use the heatsink?

Hello I'm Kirk 61yrs young. I live in small town just out side of Louisville KY. I'm a diy'er for just about everything. I stubbled on to this forum researching a noise problem I'm having in a circuit.
Thanks for letting me join.
Kirk

Hello all

I have a couple of latest revision V4 through-hole boards left for Marc Jonson's Simple, no-math transformer snubber using Quasimodo - anyone in the EU wants/needs, I can offer for 8€. Shipping within the EU would be 4€. For tracking add 3.65€

Hello,

I need some additional jumper for my Sofia tube tester but I cn't find the pn; I know that the old ones are marked RS but the research was bad.
Someone can help?
The RS can't help me because they don't accept the photo!
In attach the photo of the panel

Thanks

Walter

Looking at a new project.

Has anyone built or heard the Humble Homenade Hifi “The Monitor” and would be willing to post opinions?

This is a small floorstander with 10deg slope baffle. Drivers are Audio Technology 18H midwoofer with Seas SP21 passive radiator in a 17L cabinet, tweeter is a Hiquphon OW2. It is provided with three crossovers so would be interested in the differences.

And as a long shot, how would this compare to the 20L sealed version of the Zaph ZRT?

https://www.humblehomemadehifi.com/download/Humble Homemade Hifi_The Monitor.pdf

Thanks in advance for the comments.

I have been watching and reading all about DIY speakers and I am very interested in building my own desktop monitors. I have never buildt any speakers before and I am reading many different opinions about what methods, designs, crossovers, etc to use for a speaker design. I am getting a little overwhelmed by the many design options and drivers.

I am currently looking into building dome shaped speakers, using the ikea bamboo bowls as a bevel and 3D printing the backside (see attached image for inspiration). I will probably choose to build closed back speakers as this will probably be easier to design. Besides audio quality, I am also looking for a unique speaker design as I find box shaped speaker designs boring and uninteristing. I want someone to walk into my room and immediatly look and want to listen to my beautiful low cost DIY speakers.

My desk is placed in a very small (2m wide) student room with a low ceiling due to a bed being above my desk. I have cheap accoustic panels on sections of my walls to help with the interference, but I think my room is highly sensitive to this issue. I have a second hand KEF sub woofer in my current setup, with 4 KEF HTS 5001 satellites for my surround and use a Onkyo TX-SR393 receiver. I however want to upgrade the front 2 speakers as I want to be able to enjoy the full fidelity of my vynil collection. I listen to a variety of music genres like alternative rock (Radiohead), Electronic (Royksopp, Daftpunk), and rock (AC/DC, Nirvana), but I also enjoy listening to dj sets from the hard techno to trance scenes.

I am a complete beginner when it comes to speaker building, maybe its wiser if I build a kit or fully guided DIY project before designing my own speakers. I am open to hearing suggestions and other peoples expereinces or builds.

Hello!
I don't know if there is a more accurate word for explaining this "tsik tsik" noise from the turntables. If there is one, let me know. Until then I will say noise for this known to everyone I guess little noise coming from the turntables.

At first I thought it came from the friction of the needle with the vinyl, which creates static electricity. But then, after several conversations, I realized that there can be many factors that can cause it.
Certainly one more can be the bad quality of the record or a poorly maintained record. But, in my case it definitely has to do with the turntable itself. I say this because on records where noise can be heard strongly on my Technics SL D-2 it is not noticeable at all or at least at the same level as on one of the other turntables I have. Also another reason I think it has to do with my turntable and not the amp is that I have connected it to almost all of my amps.

So the first thing I want to check is if the ground (GND) is working. How could I check for proper grounding?
OR where do you believe I have to focus my research to find out why is it so noisy?

Thank you in advance for your answers and for your help.

-gio-

Hi there, I have a question for the speaker makers/designers.
I'm renovating our lounge room and planning on building a large wall unit to house the television, stereo and bookshelves.
I would like to incorporate a couple of cavities in the unit for some custom speaker cabinets. I'm thinking that I might make the spaces large enough to allow me to experiment with different speaker cabinet sizes. But overall, the speakers will look like they're part of the bookshelf.

I'm thinking of experimenting with a pair of full range drivers in ported boxes, or maybe a two way set up.

I know there are issues with placing speakers close to the walls/corners of a room, and ultimately it's best to play around with placement. But we also want the unit to look like one piece of furniture.

I've made a basic rendering of what we're thinking of achieving below. Can anyone impart any advice if they have tried something like this before? Is this the worst idea in the world? Or are there ways to get a half decent result from something like this?

(For reference, this is a very large room, 8m x 5m with a 3m ceiling height. Speakers will be driven by a NAD C320 amp).

Many thanks

Sale:
GU43B - 10 pcs. for $70
GU-50 - 100 pcs. for $5
GU-81M - 50 pcs. for $40

various magnets for many purposes

Selling magnets
price for all together


1-4 photos cobalt magnets
5-6 photos neodymium magnets
7-8 photos ferrite round magnets


I ask 25 USD for everything + shipping.

Payment via Paypal (+5% commission)

Hi all,
I bought a the BUD amplifier's PCB and I have noticed that the cathode resistor of the power tube (EL84) is 68Ω. This is resistor R18 in the schematic.
This looks way too low to me. I would use something between 330Ω to 680Ω (470Ωmaybe). This value will pull a current of 45mA through the resistor which is a lot.
It looks that they are applying ≈180V to the anode/plate and ≈160V to the grid2/screen.
What do you guys think, is this a mistake or do they really use this value? Such a large current will shorten the valve's lifetime, I guess. I would use 20mA instead.
Kind regards,
Pedro

This is the link for the build manual.
https://s3.amazonaws.com/tubedepot-...iles/BUD_Manual_-_Working_Copy.pdf?1583168310

Hi all,

Please, could someone help me with CCS in the cathode of a tube?
I want to use the ring of two type, but I'm a beginner in CCS designs. Could anyone advise me on resistor values and transistors?

Thank you

Here I put my skin on the market.

Project is in the development stage.

The objective of this project is to build a SPL dense compact solution for low crest factor music, I.E.: heavy bass.
All that reggae, bassy chill, full on PSY, techno, tekkno and other heavy stuff, in which long bass line happen to play for long loong minutes.

How do I do that?
Well, speakers are not built for this mostly at all, so some compromises must be taken into account. No free lunch, kids!
Basically, anything seriously compact in PA can only be ported or bandpass. Not much way around it, if same (good) bandwidth is to be achieved.
The issue of ported designs is, that they have significant cone excursion minimum in "most used" part of the bass band, and that reduces speaker coil cooling. On top of that, exactly at that frequency, most power goes into the speaker coil. So if full power goes to the speaker at that point on freqency scale, it is basically a toast within short minutes, sometimes sooner.

How come it wasn´t problem till now?
It was. Either the speaker burned, or heavily compressed, or strong limiting kicked in, kicking the output down by 6 or even 10db in some cases of even high end commercial products.
For "normal" content, it is not such big problem and this limiting kicked in rather gently and for short period of time. For heavy music, it would hinder the long term performance quite a bit.

What we gain: safety, low power compression and SPL compression, full bass, SPL density for box size, just 3dB limiter safety setting instead of 9-10dB. Low frequency mode giving fair SPL down to 25Hz.
What we lose: Maximum possible/peak SPL reached by about 3dB lower than conventional design. Also little of the Price/performance ratio.

How we do that properly?
In order to lower the thermal load on the speaker in compact design, it needs to operate in such a mode and way, that the impedance minimum and cone excursion minimum is avoided. In exact words, put the port tuning frequency outside the crossover pass band (lower). That will solve the issue. But of course, it will create another one. Otherwise this would not be novel approach at all. In this scenario, the speaker cone is forced to do most of the work most of the time. That means, it has to move a lot.
Most PA speakers "to date" are not built for that, so most speakers except the well chosen high end simply cannot do that. Those speakers will run out of linear excursion capabilities.

Objective in detail:
Box volume: Max ~210l / 7.4cu.ft brutto, ~92l / 3,25cu.ft net depending on the speaker.
Weight: ~34kg / 75lbs. Easy single person operation.
Frequency range: 40-80Hz flat, 35-110Hz -6dB.
SPL: 121dB/W/m+ according to Hornresp in halfspace.
This design could be made smaller, but A) for serious compromise B) If planned upgradability is dropped. More on that later.
Low power compression, low port compression.
In this case, tuning frequency will be 29Hz.

Basic sketch:



It is not my first rodeo with such design, and with RCF LF21N551 and barely with B&C 21DS115 it worked. Yet I sadly sold these, so it´s time to move little forward.
The wood used for outer walls is 15mm/0,59in baltich birch, speaker mount wall 18mm/0,71in the port, braces and back wall possibly 15mm/0,6in poplar birch.
The port is flow and "horn" optimized to squeeze little bit more performance out of the design than regular. Certain corners will be ground and smoothed some more. Thinking even about printing the port front-side into something more resembling of L-port. 🙂

Driver needs:
As mentioned, high displacement volume. We are talking here 20-21mm of one way stroke to fully exploit the design. Either IPAL class drivers or something like that in future. Actually, I am kind of counting on that the technology will catch up with the design. We are almost there. Also 5,3" to 6" coil for more "oomph" in 35-40Hz region would help. But we are doing it now, so we use what we have...

In order to fairly utilize the box, we need over 1,8l of displacement (one way) and optimum would be 2.5l. Meaning, 3dB more to reach all box limits as port flow, distortion figures for speaker stroke in such volume, doppler distortion limit almost.... That´s where this enclosure options end. And that is 21mm of excursion for 18".
The new RCF LN19S450 would qualify, but not in the current box dimensions. This is just a prototype, some changes to allow for 19" driver could be made.
I have already ordered that, but the story is unfortunate - Released in March 2024, odrered in December 2024 delivery NOT confirmed by may 2025. I just can´t. You know what I would have to say about RCF...

Drivers that qualify:
Generally these with displacement volume of 1,8l and more, and Bl²Re over 200:
That is, for example 18Sound 18NTLW5000 4Ohm version
LaVoce SAN184.50
All the IPALish drivers.

Drivers that do not qualify for feasibility reasons, but would work:
All similar drivers like B&C 18DS100/18DS115.
18SW115/4, RCF LF18X451.
Given the displacement limits, it would be just too expensive and not SPL dense anymore, or efficiency would be lower (more heating).

Why I gave the LaVoce pass: Remains to be tested, but Lavoce bass drivers allow for very large linear stroke. The SAN184.50 is marked as 15,5mm Xmax. If it is anything like 21" series, then it WILL work admirably till 16mm on regular basis. That gives it 1,95l of displacement volume. B&C on the other hand, has Xvar of 14mm, which is a bit of a stretch in my book, because suspension compliance dropping below 50% is at about 12,5mm That gives us 1,51l of displacement volume at 30% price hike. And so as much as I love the LOVELY 18DS115 it is rather out of the list. Not feasible. Would work, but at 1,5-2dB loss or more audible distortion. I am certain it WOULD stretch to these displacements, but possibly at too high distortion figure. Sad story so to speak.

Well, what if you pulled it all out of your a$$?
That´s where the reality comes in. Sims incoming, Prototype build will be done possibly by the end of this week, measurements next.
I also plan to make YT video about me rambling on audio topics and SAN184.50 review.

Suggestions, questions, opposition, all is welcome!

Germanium diodes
for high-quality playback equipment
used for biasing in transistor and tube products
also for power rectifiers
for example, d302 is often used for amplifiers on gm70
for anode circuits or a kenotron + two half-waves on these diodes
these diodes are old years of production of the 60s-70s
N - NEW
U - used

1) d7a-d7zh 1602 20$ us for all
2) d302 d304 d305 20$ us for all
3) d303 20$ us for all

or all diodes at once for 50$ us
+ shipping.

Payment via Paypal (+5% commission)

Hello all,

After noticing a very high temperature on my REGA mira 2000 (not possible to keep my hand on the lower casing after few hours), I started to check the idling current of the power amp stage.
It was a good check, because one channel was totally out of range (more than 50mV at power on). So I set both at 7,5mV (like it is described in this thread).

Since the idling current have been re-set, the amplifier is not hot at all. After few hours, it became barely warm (nothing compared to what was before!).
I think I fixed the issue.

This could have been the end of the story, but I had the chance to have during few days a thermal camera and I started to check the internal temperature of the amplifier.
The surprise was to see that the 4x power transistors stay cold, but some components are becoming very hot rapidly.
A little resistor (like 1/4w) is rising instantly up to 80°C. It is R88 named that you can see on the picture.
I am wondering if this is normal or not.
The resistor looks different from the other. It is a second hand amplifier that I bought in 2018.

Just to add that I never faced any "sound" issues with this amplifier. And it works few hours per day since 2018...

Any thought? Could be a normal behaviour of the amplifier ?

Thanks for reading !

Long time audiophile, tweeker, speaker builder, club system designer/installer. Here to learn and share.
Vladimir

I like electrostats, and joined this forum so I can make better electrostats, and electrostatic amplifiers, and energizers. I own Estatron LLC.

Have 4 of these excelent tweeters. They are lightly used in a dipool system and in excelent condition, both cosmetically and technicaly. Asking 195 euro each.

A friend left me this amp to look at was imported from the US and someone connected to our mains without a step down transformer.
The primary on the power transformer is open circuit, my question is what damage if any is likely on this unit?
There appears to be a number of semiconductors, IC's etc on this amp, its not a pure valve only amp.
Dont want to open a whole can of worms if I go ahead and order a new power transformer, but the cost of this amp its probably worth repairing, just want to know what Im in for.
What do most people find from experience in these situations?

I need some help purchasing from the Netherlands and possibly sending the small package to US. Please send me a direct message if you can help. Thanks.

I have a Marantz CD6007 that will play commercially manufactured CD's but will play CD-Rs only about 10% of the time. I have read that CD-Rs are only about 40% reflective as commercial CD's. These CD-Rs play 100% of the time in my $40 Sony DVD player. From what I have read, I need to turn up the intensity of the laser a little bit, so it can read a CD-R. The laser has this number on it "EP-C101". Several videos show a Pot on the laser for this adjustment, but I don't see one on this laser. Some videos suggest that the Pot might be on the circuit board that the ribbon cable to the laser is attached. Don't see a pot on this board either. Can someone advise me how to adjust the laser on this CD player?

When I turn on it is a big pop in the loudspeakers.
After this there is only silence.
The LEDs are lighting and the power on button works.
Everything works except for the complete silence.