Hi,
Does anyone know where I can find the DrP calculator/spreadsheet developed by 'Voltsecond' ?.
Thanks.

All,

I'm in the process of restoring a 20+ years old subwoofer which was sold to me for a few bucks as 'doesn't work, sound is very low'.
After testing the two speakers, the power supply and measuring the amplifier board components, I came to the conclusion that power supply caps are leaking / to be replaced and that one differential input stage transistor is fried.
See input stage schema below which I simulated with ZTX851 and ZTX951. It was initially built with 2SC2389 and 2SA1038. I have one 2SC2389 fried, the rest is measuring ok.
I'm planning to replace the 2 2SC2389 at minimum and wondering if I should or not replace the 2 2SA1038 as well to have the 2 pairs from equivalent series.
Any advice would be welcome 🙂

Enjoy day !
Jean-Francois

Not sure if this belongs in this forum or the instrument one, here goes.

I am building a self contained electric acoustic u-bass, basically I bought a u-bass from:

Kielder Bass ukulele by Buzzards Field Ukuleles

and I want to put the amp and speaker in the body of the bass, powered by a battery, for a mini self contained bass. Amp, driver and battery as follows:

TPA3116D2 Subwoofer Digital Power Amplifier 100W AMP Board Audio Module UK | eBay

Buying a SB Acoustics SB13PFC25-4 woofer? | SoundImports - SoundImports

Power Bank XT-16000Q3 with 24V Output from XTPower

So now I need to design an enclosure that fits inside the body of the bass, and gives me the necessary response. I would like to do a vented enclosure, but it may be too big. How do I go about calculating the volumes, port size, etc.? Will I be able to get good response down to FS of 44Hz in a sealed enclosure?

Any advice is appreciated.

I have been reading a lot about and slowly falling in love with the open baffle concept. I bought an Executive BT kit last year but with a new baby never found the time to put it together.

I was thinking about repurposing the batteries + amp + CX120-8s combined with 1 GW-215/4 in some kind of origami briefcase setup to listen to outside. I want to keep it light and compact so it would kind of fold in on itself for storage but then open up relatively wide for some soundstage. I would store it indoors so weather issues are no problem I think. Has anyone done anything like this?

One specific question I have is with the baffle thickness for the sub. Obviously a thicker baffle would be ideal but they are heavy. Could I get away with say 3/8" plywood with reinforcements? What material would have the best combo of low weight and strength? I guess another question is whether it would be worth getting more efficient full range drivers to get more battery life. Just curious what other people's experiences have been.

Hi everybody,
thank you for showing attention to this thread 🙂
Does such preamplifier exist ?
I`m not guy who know a lot in electronics department and this why asking for help me out.
I would like to have preamp "signal" multiplayer ,if that description makes same seance...🤔
Situation is like this ...mono signal ( separate left and right channels) out of DAC ( Fostex HP-A4 , 2 Vrms) and in to preamp "signal" multiplayer where I can multiplayer to two identical signals out at the same value of 2 Vrms. Off course ,quality is priority. I should look like this:

I bought mcintosh c20 preamp as is
Both channel sounds okay just little crackling noise when I turning the volume potentiometer
I cleaned the entire unit with contact cleaner and
I sprayed deoxit on each volumes and switches.
I dried three days.

Now, one channel is working perfect but
another channel has buzzing noise.

When I turn the main volume potentiometer to louder, the buzzing noise become louder.
Also crackling noise time to time.
When I turn the main volume potentiometer to very silent, I cannot hear the noise.

I switched inputs and nothing changed.

What could be the issue? is it potentiometer? or something else?
If it's not volume potentiometer, shouldn't be buzzing noise same level regardless of turning the volume?

I am comparing WinISD simulation for port tuning with UniBox.
If I use "theoretical" response the results are the same but if I use FRD file for Dayton DC300 in UniBox, the difference is huge.
I have made screenshots for port tunig in 138 l cabinet (4.87 cubic ft) with port diameter 7.50 cm. There is obvious that different
Fb should be used for the best results (the lowest F3). So which tuning should I use or consider to be better?
The "real" one with frd file seems more realistic but it´s a surprise that 12" woofer will get F3 only at about 33 Hz.
I do not have possibility to measure the speaker response in cabinet.

Theoretical response - port length 9,95 cm



FRD simulation - port length 4,85 cm

Is C18 a 22uf ?
I’m rebuilding this driverboard since there were a few caps missing along with transistors

Seas 10” A26RE4 8ohm pair
I will sell at 30% of new price.
One woofer was gently tested for four hours. The other was packed up and looked at, and then put back in the box. Still has protective plastic knobs to protect the rubber surround, which would orherwise be deformed as it protrudes.
I ended up using the W26FX002.

Collection during May 2022 in both Oslo, Norway or Montreal, Canada, or sent anywhere.
Payment: Paypal is fine, also bank transfer.

Any suggestions?
Looking for a diy (kit, groupbuy, pcb) etc. "ultra" low distortion, low noise balanced linestage?
Would prefer "small footprint" ie. some smd parts.
BTW: I have the dcg3 which I like very much but it is not balanced.

Hey guys, not sure where in the forum (if anywhere) I should post this.

Basically, bought a bass guitar amp dirt cheap because one day it worked, next day it quit they said. Had hoped a simple issue like a bad solder joint, but instead looks like the coil started to unravel inside and the wire eventually broke.

Managed to get the old coil out and the cone/spider are undamaged and still in place. Coil a bit deformed. I was able to get some measurements and about to make a paper mockup to ensure I have the correct diameter. Problem I'm having though is finding a match.

Seems like a 36mm or 36.5mm coil. 34mm tall. Where I am really having trouble is with the wire coil width itself. Everything online is between 12-14mm, and this thing is only 7mm.

So... first obvious question is, what would happen with a new coil if the winding width is 5-7mm too wide?

Does anyone know where a new one can be made without sending it in?

Should I attempt to make one? 32AWG wire isn't too pricey for a roll, though the roll is much larger than I need. Aluminum wise, I was thinking of a Coke can.

Thing is, it's a stock speaker from a Fender Rumble 75... it's generic made in China and not great to bein with. If I can fix it for $25, great... otherwise I'd rather just wait for a used 12" bass speaker to pop up for sale. That said, it's currently dead so, may as well learn and have fun with it. 😀

hi everyone
comes to me a jl audio hd 600/4 playing only 3 channels. someone previosly test it and take apart the output mosfet on the bad channel.

if i install new mosfet the red/green protect lights on and dont work any channel. try with the good mosfets from another channel same thing.

irs2011 driver replaced. i have the same voltages in the bad channel like one working channel. if i play 60hz tone i see it on gates of bad channel and the signal is equal on another good channel.

i have 5 vdc on the bad channel all time. the amp has the same resistance from output to gnd on all channels. good output inductors. no bad traces.

if i install the mosfets the red/green protect lights on but if i take apart the 0.47uf blue cap the amps turns green and plays good 3 channels. the bad chanel has 5 vdc, plays but the speaker cone go all the way.

Anyone with a similar problem?

double checked caps, resistors and diodes on the irs2011 area

Curious how this sounds, message me if you have one for sale

Sometimes I want to display an online image from elsewhere on the web in a post, e.g. http://www.blah...blah.jpg. It seems the only option with the current software is to download the image and then upload it to the post. Is there a way to display a web image directly?

Hi there...
I need some advice or tech support...what is so good on Garrard 301 turntable mechanisms? Even very old pieces of this type of turntable's have high prices on market. Will be possible to recreate some of design details in homebrew turntable? ....

Digital audio is the factual high fidelity and true musical king. Vinyl sounds like the sun faded old lady version. Somewhat nice but lacks the really strong, muscular and bouncy pepp in the step. Lacks the really high and the really low. Lacks the powerfully, juicy but still clean and pure total control.

But vinyl crackes really really nicely like stone age camp fire did more than 5000 years ago🤗🔥


Ok this sounds evil. But we know that is true. Or.

You got a very very tired stereo setup that really finds sonic benefits of the true vinyl compression and dirty camp fire crackeling. 😇

So, there, someone finally said it like it really is🤘🙂

I build a simple measurement-mic with a Panasonic WM-61A (or copy ?) from ebay.

It works, but I have no way of knowing whether it has a flat freq-response.

So, airflow/wind is white noise and if averaged over (long enough time) it should measure flat right?
Maybe a low-noise 12V fan and some ducting could provide a wind-source?

Sounds too simple, but whats the flaw?

Kind regards TroelsM

Just for interest,

OTL guitar amp..LMAO.

OTL-Gitarren-Amp - YouTube

I put it here because it may be of interest tube related.

Someone asked can't remember who what an OTL guitar amp would sound like...

I guess it will get moved to the Instruments forum...I think it would interest some here!

Its only for interest they can be made..

Regards
M. Gregg

I'm sorry for the terrible title.

I build a PE Executive box and while I like the bass and overall response the narrow soundstage sucks. I want to repurpose and supplement its components to make 2 separate powered speakers that act as the L/R channels of a stereo signal. The simplest and cheapest thing to do would just be to make separate speakers and wire them from one amp.... but what's the fun in that? I know you can pair multiple BT speakers off the same signal so I am just looking for an amp board that would let me do the same with custom speakers.

Hi all,
Can anyone supply pictures of actual griplet wire through mod, I have 2 x 104's however one has developed a known griplet related issue, and I'm a little nervous regards doing the through wire repair !!!!

Robert

something from the past which one might wish to try using cardboard to hear its effects





Also, consider trying a JBL style aperture. The long axis goes vertical.

I have a

miniDSP 2x4HD
MiniDSP nanoDigi + 4 FiiO D03K stereo DACs

for loudspeaker prototyping. Light use only and want to simplify cable mess.

Wanna do some DIY. What’s a suitable amp board for a couple of 2” compression drivers with big horns? 16ohm 112dB of sensitivity, 200w max. 500-20khz. I mainly look for a low noise floor in combination with low THD and high SNR. I will probably run a max 1 watt through these so power isn’t the biggest challenge, but a headroom would be good I guess.

Any suggestion? Budget around $200 for board and Psu.

Hello

I'm considering the Odyssey Performance AGM battery but it's $100 more than the Duralast Platinum AGM battery. What are your thoughts?

is there anyone can help me? Many thanks.

Hello everyone,

Sorry long post!

I have been given a Nakamichi AV-8 receiver (saved from landfill)..

Good news is that it fires up (yay) and works through headphones (double yay) but there is not output to the speakers. There is no obvious component damage to the output stage. The display, switching logic and the output stage cooling fans fans are working. There's a clunk from one (or more) of the speaker protection relays when the unit is powered down and also if the A and B speakers are pushed on / off.

Bad new is that it's a nightmare to work on and I haven't managed to track down a service manual for it yet (although I do have a AV-10 service manual which I may be able to get by with). The output stage is arranged as a 'removable' rectangular box. There is no removable service panel beneath the main board which unfortunately I think is the location of my problems.

After an hour I had the entire unit stripped down (only way to get the main board out to inspect underneath) and observe a pair of DC rectified circuits which lead off to the protection circuit (and other things). There has been a fair amount of heat in this area (tell tale browning) and the dry joints beneath were glaringly obvious.

The challenge for me is that the entire device has to be fully reassembled again before it can be tested. After de/resoldering the area and reassembling the whole unit, good news id it's no worse, not so good is that it's no better.

I'm grateful for the AV-10 manual I have downloaded from Hi-Fi Engine but would feel more comfortable with a copy of the AV-8 manual if I can get hold of one.

Any suggestions appreciated (it's off the bench at the moment)

Ciao Blake

Hi all,
As the title suggests I would like to connect a ceramic cartridge to a standard line level input on a modern solid state amp. I do not need RIAA equalization. On the thread https://www.diyaudio.com/community/threads/ceramic-pickup-preamp-schematic-needed.175822/ I found a circuit (attached) but I thought that I would touch base to see if this circuit is still valid. Also if anyone could tell me what that mystery component is.
Thanks

I have finally fully glued up three MDF subwoofer cabs of the DIYsoundgroup variety. I still need to flush-trim the overhangs and sand, but then it will be time to apply a finish. I think the best and easiest option for me would be a roll-on textured coat. I don't have any experience with using this kind of product, so I am seeking input. Also regarding the color. Some are black or white only, and some you can tint AFAIK. Is it worth getting a tintable variety so that I can choose the ultimate color and shade, or is that just making things more complicated and asking for trouble? What products and techniques do you recommend?

Hi everyone I’m trying to fix this mixer. The output is heavily distorted from the main output but ok on monitor….any ideas please?
also have old schematics and no service manual. Help!

Well. I have been thinkin… Near field sub bass?

First of all. Wiew this from the chill and cool old and true hifidude Paul:

Login to view embedded media

Well, now. I have built several high end car audio systems. Fully active DSP, multiple subs. And Thats Truely True Near Field 🙂👍

Here is my opinion on near field in home audio and subs: you do not want them, you do not need them, in all the lovely powerfullness they could and absolutely will bring:

If.

If you have got a stereo/surround system that is top notch matched, and have got large enough, fullrange and Powerful enough left and right speakers: Then. Near field subs is simply only the next best thing… To get that muscular, powerful, controlled, juicy bass. The true sub bass, and bass, We all really want and really needs😘



Dont ya think? 😎
What do you think, am totally wrong?

No, i am not wrong🙂


Edit: Enjoy🤗 The absolute king of the movie soundtracks. Hans Zimmer:

Login to view embedded media

Hi guys, can anyone advice on a source (kitset OK) for an adjustable with a working out voltage of around 40 to 40 V, Prefer dual supply but can of course use 2 single's.

Bought this one from F/Bay, which was no good

https://www.ebay.com/itm/2534773923...+gy4VJXZfyk0LVeh5iBAfqyK7qs=|tkp:BFBMqsDW845g

As it will only adjust to 38V, supplier claims that manufacturer changed design & did not advice suppliers!!

Cheers

I'm still looking for the "best" cabinet for my 12-280 8W woofer from Thomann (as described in this thread: https://www.diyaudio.com/community/...as-with-12-280-8-w.383285/page-2#post-6949739).

I sort of had dismissed tapped horns because of size, but a Tham12 comes in pretty close to my size-limit, so curiosity got the best of me and I started drawing/simulating a looot of TH-cabinets with actual internal volume up tp 75Liter. - some pretty efficient options in that range, BUT the boring downside is that I can make a HR-sim that gives almost exactly the same response for a 6th order parallel bandpass (within the same cabinet volume). I´m assuming that a TH would win if cabinet-size was not a constraint, but it is.

So, the question for this thread is: assuming that a 6th order parallel bandpass (HR: BP6P) and a TH are the same volume (60-80Liter in this case) AND have approx. the same FR and diaphragm displacement, which is better? Cooling must be better in a TH, but construction is also more complicated and heavier due to the internal path.
Looking at impulse responses for both systems, I cannot see which is better.
Use-case is indoor, small, party-setup. Lower knee (-3dB) can as high as 50Hz). must work up to 150Hz. Power around 200-300W

Kind regards TroelsM

Just a couple of little ones:

In my account, it says the following:



The time has been populated twice.

------------------------

In the donations section: (https://www.diyaudio.com/community/account/upgrades/):



While killing (offing) ads still makes sense, I am guessing there should be a 'turn' there somewhere

I mean my PVC fishing dinghy. It's a pinhole. In the old days we just put on a 2" round patch. Sometimes it was self adhering like a bike patch but I think I like to use a patch with liquid for more secure chemical bonding. I am familiar with surface prep but I am wondering if there is a new and improved patching method or do I just buy a vinyl repair kit? I don't own a PVC welding gun.
Any help is welcome. TIA

Good Day Gents!
I am a proud owner of a Mercedes Benz PRE MERGER AMG SEC Coupe. While maintaining the classic interior appointments, I decided to install the following components. A Nakamichi MB 100 with the separate DAC / Pre amplifier, Audiocontrol Epicenter, Audiocontrol 3.1 signal processor, Nakamichi DB 50 dual amplifier balancer, Nakamichi PA 304 4 channel amplifier for the front and rear satellite transducers, and a Nakamichi PA 302 2 channel amplifier ( bridged ) with a JL Audio 10 inch low frequency transducer. Here is where I would like to receive your input. The 24 Bit High Definition DAC Pre amplifier has an output selector with the option of using a 1 volt, 2 volt, and 5 volts, along with an Acoustic Response Compensator with Lower Midrange optional settings of 100, 120, 140, 160 Hz @ -10db, -5db, and 0 db.
The Upper Midrange settings are at 1.0k, 1.2k, 1.4K, and 1.6k with -5db, -2.5db, and 0db. It has dual front and rear outputs. To get the optimum output from the preamplifier, do you recommend that I incorporate Y Adaptors on the front and rear outputs into the input of the Audiocontrol Epicenter, and the output from the Epicenter to the input of the Audiocontrol 3.1 in which has front, rear, and sub outputs?
I am interested in receiving your input on this matter.

Hello, I'm looking for schematic for phoenix gold M100.
I have one for recap and owner ask me to remove all the crossover circuit to have a direct amp.

Another question, big resistors for + - 15v are 5w or 7w?

Thank you.

Are there any particular things I should make use of?

My old receiver packed up a few months ago.
No biggie as it pushed me further along the DIY route I was intending to go anyway.
I don't think I would get a lot even if I repaired it.

I am eyeing the case. I can get quite a lot in there.
Plus a few fittings.
There is a lovely big heatsink that I am sure will come in handy, plus a smaller one that might be helpful for my Salas L-Adapter.
A chunky looking transformer that I know nothing about.
Is there anything else that I should be particularly looking to salvage?

I was thinking I might stick the fascia and whatever else I don't want on ebay.

I have a decent PC audio interface (Echo Layla 3G); two channels have built-in microphone preamplifiers with switchable +48V phantom power.

The preamps have not generally been used until recently when I noticed a problem:

• a hiss or soft white noise, about 24dB quieter than speech
• when input is really loud, it cuts abruptly out

I'm relatively novice when it comes to electronics (I'm a computer programmer) but I enjoy these opportunities to learn, and this audio interface is worth maintaining.

Aided by a schematic, I think I've isolated the problem to a specific part of the circuit. I'm a little out of my depth here and would be grateful for a santity check and advice what to do next! Thanks for your time.

I've attached some (hopefully helpful) diagrams and photos which I'm going to refer to.

What I've found

If I connect a capacitor from (A) to ground then noise goes away. I tried things like a 0.47uF 50V. The result is the speech sounds crystal clear.

The same can't be said for point (B), doing so has no audible effect.

So my novice conclusion is that CA54 (1000pF) is actually faulty and a break in the circuit -- and that noise from the ground and +/- 12V supplies enters IN- of the amplifier (UA3). How wrong am I? 🙂

Interestingly I can replicate exactly the same results on the corresponding capacitor in the second preamp on the board.

So... I think I need to replace CA54 with some capacitor, and probably CA52 as well just for consistency? (and repeat for the second preamp)

Do I need to order an exact replacement (film or ceramic?), or is it sane to use any matched pair of capacitors? Specifically, I already have a bag of these 0.47uF 50V electrolytic capacitors handy, and not a lot else.

How I got there

I'll tell you my logic because I can easily be wrong. I'm using a phantom powered mic (Behringer B1). I started with knowledge the hiss is happening on both preamps, which means:

1. on shared circuitry (most likely)
2. both preamps failed for the same reason (less likely, but in the end seems to be the case)

So I started looking at the shared circuitry, which is the the +48V, +12V and -12V supplies, and the multimeter shows them all correct.

I noted that CA42 (on the diagram) is actually not present. But since the +48V already has lots of capacitors (including 63V 47uF connecting it to ground) I conclude that's why it was omitted.

One difference is the notation. The PSU schematic uses 'jill' whereas the audio one uses 'jack' for ground. Both are from the same publication. I suspect this is an important difference; what does it mean?

Since the shared circuitry checked out, I experimented with adding a capacitor across CA50 or CA55, with no affect on the noise. And the noise still goes up and down with the trim control (VRA2:A). Conclusion: it's the audio input to the UA9 that is noisy.

I tried placing a larger capacitor (probably 0.47uF) across CA51; the noise was reduced in volume slightly, but it sounded more like I'd just low-pass filtered everything including the speech. Conclusion: CA51 is working.

I swapped out CA53 and CA47 with identical ones. No effect. Conclusion: CA53 and CA47 are working.

With it switched off, I put a multimeter between (A) and ground and once it 'settled' got 1.5K. Repeated the test with (B) with the same results. Conclusion: RA62 and RA57 are in good health.

That took me to the capacitors, When I get different effects for (A) and (B) as stated above.

Your advice appreciated!
Many thanks.

Free: Jens Rasmussen/Bob Ellis Active Filter Four v. 1.0 (2006) kit. For loudspeakers.
Contains Manual + 5 boards + plastic bag with parts (whatever came in the kit).

I must have bought it with a project in mind but it didn't happen.

Free but you must pay shipping from NJ (probably around 12oz total). Will fit in a USPS priority box for instance.

Afternoon all.

I'm looking for a little help concerning the crossovers in my Polk Audio S55 speakers. I recently purchased replacement caps and resistors and would like to point-to-point wire the crossover with the new parts. (The board has some damage.) However, I don't feel comfortable reverse-engineering the crossover schematic for fear of doing it incorrectly. I know some very basic concepts but not enough to look at the crossover and know what goes where.

As I said, I have the parts and Polk-made crossovers, I just need the proper design. I enjoy learning so if anyone could help me out and work through this I would be much appreciated. I'm also more than willing to compensate anyone for their time and effort.

Thanks all and I look forward to hearing from the community!

I had to repair a total of about 10 units from that company . 8 of them i did on my own 2 of them had weird troubles so i asked the help of the company in schematics and fault finding .

You will not believe how nice and friendly people picked up the phone on the other side willing to help from any aspect even willing to talk about the problem over the phone and often in cases where the model was quite old to remember by hart .

Nice people , very helpful and if i am allowed to say the Balanced Audio is the definition of what we say a service minded company .

Thank you all and my special thanks to Mr Victor Khomenko who looked in my case personally.

Kind regards
sakis

Our audio shop has closed due to retirement and I would like to share our mod for the ADCOM GFA-555II power amplifier. I hope that this will help some of you who would like a little better sound quality but the mod will improve clarity first and foremost.

Bought a fake one from ebay, need a genuine pcm1704, thanks.

Hi there all


I have a REL Stadium mkI here ... previous owner removed the frequency select switches and threw them away. I need a schematic to retrofit a new pair. I need assistance with the section where the capacitors for the cutoff frequency gets selected. What pins are common to the selected poles etc.

Thanks in advance!

In the plan, the port is placed at rear panel.
l would like the pot to be in front to give more flexibility in placement.
l will use the alternative vent placed at the bottom of the front panel because it looks móre tidy.
Is there any other adjustments necessary before l send the plan to a carpenter?
Thanks you for input

Hi all. I diy’d 4 speaker boxes before but currently living in Hong Kong, it is near impossible to do it at home.
I stumbled upon IWISTAO speaker cabinets on Alixpress. Many look impressive at first sight but I wonder how they were designed and for which speaker. However they also offer the official Fostex enclosure for the FE126E for a nice price, which I could conceivably use with the current FE126NV.
I wonder if anyone has experience with this brand and ideally with this box. I can imagine that the Frugelhorn is better but this is much more realistic for me.
Link:
IWISTAO Customized Labyrinth Back Loaded Plus Bass Reflex Hybrid Speaker Enclosure FOSTEX Official Drawing Full Range FE126En
https://a.aliexpress.com/_mK0U9rm

I replaced this board in my X1 with a new members' purple board.

This board comes as pictured.

$25USD plus real shipping cost from New Zealand.

thanks

We have 2 advanced PCB manufacturing bases in Jiangsu and Jiangxi, and 1 PCB assembly factory in Shenzhen.

Visit PCBONLINE at https://www.pcbonline.com/.

Our advanced PCBs include HDI PCBs, high-frequency PCBs, ceramic PCBs, flexible PCBs, rigid-flex PCBs, and aluminum PCBs. We offer free DFM (design for manufacturing), DFT (design for test), DFX (design for excellence).

One example of our PCBs/PCBAs is below.



Our email is info@pcbonline.com.

You can send your Gerber or IPC-2581 and quantity to get a fast quote. We have a cooperation with FedEx, and you can expect a low shipping price.

A buddy called me and going to throw a reception at his place. He has a pair of 12" DJ speakers/amp but they don't have much bass.
I have a well preserved pair of woofers that were popular back in 2008, NHT's 10"s. I looked around for some specs, didn't find enough data to run it in WinIsd, but found threads that recommended 2 - 3 cubic foot sealed boxes. I have a hefty plate amp to drive them, all I need is a box size for, primarily for sound reinforcement and some kick.
I was thinking a simple box, 19"w x 24"t x 19"D, [both woofers mounted top and bottom]. Tempted to add a middle brace, so there are two cells, maybe just make two single boxes.

Any recommendations?




Thank you for any suggestions.

Greetings all,
I'm new to the forum and this is my initial post.

I acquired a power amp from a Wurlitzer Sideman with the intent of scavenging the parts to build a guitar amp. The amp itself has one 12ax7 preamp tube and a pair of EL84s in push-pull (I'm assuming). I didn't find any diodes and there was an empty octal tube socket that I'm guessing was for the rectifier. From what I've found on the web, the Sideman was manufactured from 1959-1965. My intent for scavenging these parts was to build an AC-15 type amp. After spending much time, I've been unable to find a schematic for this unit. It's a Wurlitzer 501510 power amp.

After pulling the transformers, sorting out the continuity of the windings, and passing voltage through them to identify the ratios, I have come up with the following diagrams and measurements for the PT and OT (see attached). Note the voltages I've measured represent an unloaded circuit.

The numeric codes stamped into both transformers are indicated on the diagrams. I wasn't able to find any information on these using the code numbers. I also wasn't able to find any equivalent modern construction transformers to compare to (at least for the PT).

My questions to the forum are the following:
For the PT:
1) What's the deal with a 136V B+ secondary and how is it possible to power two EL84s and a 12ax7? I measured that multiple times and got the same result. That voltage doesn't seem to be particularly useful in a tube amp.
2) What purpose does a 34V secondary serve? Would this be used for a rectifier filament?

For the OT:
1) For two EL84's in push-pull, the secondary output represents 12 ohms. 12 ohms? From what I could find, the Sideman had a 4ohm speaker. Something doesn't add up. I ran 10 v ac into the secondary an measured 260 v in the primary (130 CT). I calculated a winding ratio of 26.

If you have any insight into these transformers and their specs as measured, your input would be greatly appreciated. I'm hoping I didn't acquire some old doorstops.

In addition, I found this part (see attached pics) inserted into one of the octal sockets. Any idea what its purpose is?

Thanks in advance.

Hi all,
I need help identifying the carbon comp resistor and it power rating. Thank You!

With the AD converter and AES/EBU or at least S/PDIF output. Preferably in Europe.

Hi,

I have an opportunity to purchase some more speaker drivers, this has been on the backburner for a more than a year now but finally the time has come.

I have finally completed my first sub as well which is just great! My retail bought tower speakers sound cleaner now that they don't have to cover the whole spectrum! So, the lowest octaves are taken care of which is why I am reconsidering my original plan.

Original plan: 3 way tower speaker (1" tweeter, 4" mid-range , 7" mid-woofer)

New plan: 2 way bookshelf (1" tweeter and 5" mid-range) or

Reason being simpler and much cheaper and smaller final speaker as well. What are the possible implications of such a decision? Is my reasoning sound? Room size is about 2500 cu ft.

Many thanks!

what is the best driver for wbin box?
I would like as low as possible.
the parameters can I be these?
qts = 027
mms = max 150gr
bl = min 24
xmax =? it's important?
power = min 900W?
fs?
thank you

A Large LTspice Folder from Bordodynov. Half way down this page are links to the models. You can grab the whole folder or cherry pick the ones you want.
There are also a bunch of extra example circuits.

Components Library and Circuits - LTwiki-Wiki for LTspice

Please dont ask how to install, thats easy enuogh to find, search Diyaudio, in that wiki or on youtube.

Hello everyone I ask you who have more knowledge than me to help me solve an enigma.
Is the emitter follower really 100% negative feedback?

I bring you some writings of an ex audio designer translated, where he questions the negative feedback of an emitter follower, I would really like to understand where the truth lies.

"The RADIOTRON DESIGNER'S HANDBOOK (by the famous RCA - radio corporation of america - FOURTH EDITION by LANGFORD and SMITH - 1952 - the foundation of electronics and also of a lot of hi-fi of our times, 1482 pages) at page 317, chap. 7.2 titled the following sentence talking about the "cathode follower" of a triode:
"As a result of 100% negative voltage feedback inherent in cathode follower, both the distortion and the output impedance may be very low".
I personally add that the same sentence could be applied also to a transistor in EMITTER FOLLOWER.

But is this REALLY true? This is written and handed down, all right, but to me personally a long time ago, a spontaneous question arose:
QUESTION: If the transistor does NOT amplify in voltage (but only in current,) does it mean that it's 100% negative feedback in VOLTAGE?
Nice question

Emitter follower properties:
1 - high input resistance
2 - low output resistance
3 - high current gain
4 - POSITIVE voltage gain, but less than unity

We should think about the fact that a transistor is a CURRENT AMPLIFIER (by nature of the device), and not a VOLTAGE AMPLIFIER, so, if it amplifies in CURRENT (as of its nature, in the simplest circuit that exists), can it be blamed not to amplify also in voltage? but this could be taken as pure philosophy ....
Maybe this could be valid for a tube or mosfet that are voltage-driven devices (but even there it may not be true), then I have drawn the equivalent circuit of the transistor in emitter follower and I have noticed that NEGATIVE FEEDBACK DOES NOT EXIST, neither in current nor in voltage and we will see later why.

Current Negative Feedback

The condition for NEGATIVE FEEDBACK is:
- The decrease of the maximum amplification obtainable from the circuit itself (that is less than that which can be obtained in the use of the same device without the application of nf)

If the OUTPUT is on the EMITTER leg, (and with no load on the collector), by definition the transistor amplifies ONLY IN CURRENT (MAXIMUM CURRENT as we will see) and the resistor RE is used ONLY to LIMIT the amount of the OUTPUT current, otherwise the transistor may burst.
Not putting the RE, the transistor ALWAYS AMPLIFIES ONLY IN CURRENT and its AMPLIFICATION is of the same ENTITY as WHEN the RESISTANCE is there. So emitter resistance is not able to change things. The amplification factor of the stage, DOES NOT CHANGE AT ALL.

The current amplification factor of a transistor is called BETA (also called hfe) which has a precise value like 11, 26, 54, 77, or 126 or 12000.
This parameter says that if at the input of the transistor I put 1mAh of current (direct or alternating), in the case of an EMITTER FOLLOWER, at the output I can get back a quantity of current BETA times bigger.
Where does the transistor get it from? From the power supply.

If the transistor amplifies 100 (i.e. its BETA or hfe is = 100), sucking current from the DC supply, at least, we can have on the collector circuit a current 100 times bigger, i.e.: 100mAh.
But the output of this current, in this case, is taken from the emitter circuit, and there the BASE current (the input one) ends up too, so what we will get in the example is a nice 101 mAh output. MAXIMUM AMPLIFICATION in CURRENT. Actually already a bit more, we have also recovered the base current supplied by the external signal.

We have these 101 milliampere even if we remove the RE, and they can be measured with an ammeter (see FIG.1). Now the first result is to see that on the EMITTER Node, the two currents add up and do not subtract. If they subtracted there would already be something to think about, maybe a negative feedback: that is something tends to remove instead of adding. This can also be verified in the equivalent circuit for alternating signals, shown below (in FIG. 3 and 4).

So we can state that the RE CANNOT control the output current on the emitter leg. This means local current negative feedback = ZERO, up to the limit of its operation (saturation or burnout of the device or LIMITATION due to the series resistance at the input).

Voltage Negative Feedback

Remember that due to the MILLER effect, the resistance seen from the input is NOT anymore only the base resistance (hie) plus the emitter one (ex: if RE= 470 ohm, that is 1000+ 470=1470 ohm), but instead to "hie" (1000 ohm) is added a resistance of 470 ohm (RE), multiplied by the BETA (100). The TOTAL input resistance of the transistor ONLY will be = 1000 + 470 x 100 = 48.000 ohm. In the game, is lost in practice, part of the voltage signal that arrives at the input (BASE), in the case of the example about one 48th.

If we have lost part of the input signal, can we think of the effect of a voltage feedback? And if so, how much is it worth?
If the value of the input voltage is 1 volt and 0,98 volt come out of the emitter (we have lost let's say one 50th, or about 2% - the base current in this case would be 1 Volt/48.000 ohm), the amount of the negative feedback, if this is the case, how much is it? we will see in a moment.
(Moreover I am wondering: the same thing is done by a "miserable" POTENTIOMETER (lose voltage on the way) on two resistors in partition, isn't it...?)

Anyway If we lost half of the signal (0.5 volts) we would have lost 6 dB (and we could talk about 6 dB of feedback), if we lose only 0.3 volts, we have a loss of about 3 dB, if we lose 2% of VOLT the attenuation would be 0.175 dB.
If it were really negative feedback we would be at almost unlistenable levels, since around ZERO db of feedback is SYNONYM OF TOTAL ABSENCE OF negative voltage feedback.

A little consideration also about linearity and output impedance of the BJT follower.

The output resistance is not equal to RE, but for a transistor it is normally lower even without the use of feedback and much lower than for voltage-driven devices (FET and TRIODES). This also means LESS influence due to the external load that is in parallel with RE.
The linearity of a BJT follower is normally very high, because the linear zone and the active zone are practically coincident, which is not the case for voltage-driven devices that have respectively the active zone after a few volts (FET) or tens of volts (TRIODES)."

Every thought is appreciated, thank you.

I'm trying to repair a C-J preamp damaged by ESD. I cannot identify one of the damaged JFETs marked "CAL JF 1182B" ("CAL" I believe is Calogic.) The device is paired with a CAL J177 which is a Calogic P-channel FET - so the device in question is the complementary N-channel device. But I cannot find any reference to this device online, although the J177 is readily available.

I'd appreciate any help.

Thanks
Kofi

Good Evening All,

Has anybody got any original pattern ZTX653 from Ferranti days i.e before they became ZETEX and then Diodes Inc? Only looking fro around 10 pieces. I'm UK based.

Regards

Richard

My sincere apologies in advance to those who will find the appallingly sloppy and incorrect usage of the term "phase plug" to be irritating. I am with you in spirit, but the flesh compels me.

I have often wondered about phase plugs and what is the optimal shape, how do you design one? Manufacturers seem to see no need to go beyond the generic bullet shape. I suspect it is the base of the phase plug that matters more than the tip. I mention my thoughts on phase plugs in another thread:

keantoken said:

I suspect there is something to the opening angle of the crevice between the phase plug and cone, but a bulbous phase plug becomes obstructive and the "horn" this creates points away from the listener.

The point on the tip of the phase plug helps the wavefront separate from the tip rather than form a standing wave node like on dustcaps with a large radius. Sort of like Fostex drivers with pointed dustcaps although according to them it seems to be more about vibrations of the dustcap itself than it's affect on the wavefront. A dustcap below it's breakup modes behaves more like a plane radiator with beaming whereas a phase plug or pointed dustcap produces less of a planar wave.

For similar reasons a phase plug should probably be longer than it is wide, to minimize circumferential standing waves.

That said, phase plug geometry seems to be fairly forgiving and the effect of these details might be tiny compared to the ragged response you can expect in affordable fullrange drivers. Perhaps that is why I have never seen a detailed discussion on phase plugs.

I suppose a conical dustcap could be configured like a Walsh driver with the taper matching the speed of sound in the cap to the speed of sound radially outward, but I don't know if the radiation pattern would be an advantage.

Click to expand...

An alternate take on phase plugs was done by Decware which experimented with a resonant cavity in the phase plug

https://www.decware.com/paper46.htm
If I am allowed a personal opinion I don't really want a resonator built into my speaker, It's all we can do just to stop the cone from flapping around. But, I would eagerly listen to this speaker and see for myself if I had the opportunity.

A very different take on phase plugs is given by Mark McKenzie in one of his patents. This is very interesting to me as it demonstrates application of acoustic theory to the design of a phase plug for woofers. I'm not sure of the boundary layer acoustics he speaks of, although it resembles the discussion on the Decware plug.

https://patents.google.com/patent/US20070297638A1/en?inventor=Mark+McKenzie&page=1
Mark makes some interesting comments on phase plugs when he first mentions his patent US20070297638A1:

MarkMcK said:

Simple answer is no. Also, I feel that explanations of the why and how of phase plugs is inadequate. I touch on this problem briefly in my AudioXpress article on modifying the TB W3-881S (not to be confused with its replacement, the 881SD) transducer. I go into more detail in my second patent application I filed last year. This patent application is not scheduled for publication until December of this year.

The plugs I am now designing based upon this new theory are looking completely different from anything that exists now.

Now, for me, here is the most important point of my reply. The major sound problems with the Fostex 126/127 are not caused by the dome dust cap. Nor can these problems be corrected by any plug replacement of the dust cap. Replacing the dust cap with some type of plug will make the 126/127 sound slightly different, it will not be better.

Best wishes on your quest for better sound,

Mark

Click to expand...

How do we find the optimal geometry of a woofer phase plug? Is the optimal shape round or pointed, or neither? Are straight sides ideal? Facets? Flat ended? Should it be bulbous or should be it conical in shape? Or are we all fools for not having McKenzie's top hat shaped phase plugs?

Hello. Just joined today. I am new to audio electronics and electronics, in general. My adcom had some white fluid leaking from the output transistors. In wanting to clean the thermal paste, I saw that I’d have to take things apart to gain access and thought I may as well test things.
Are there any digital LCR or other meters which test the capacitance of the large, high voltage, high uf rated caps?
I was looking for some vintage test gear, but it is difficult to find. Tried getting help elsewhere and they just said not to bother. They don’t seem to be fans of this amp. I have had the GFA 555’s for 27 years and find them to be excellent sounding amplifiers.
Any help would be appreciated. Thank you.

Hi

I have 3 big electrolytic caps 220uF for the power supply of my tube amp and I would like to add some foil capacitors in parallel. How do I determine what capacitance is ideal?

The guy that sold me the amplifier and built it (I think) recommended me to do that by using 0.1-0.47uF capacitors. But how do I determine what exact value? Does it even matter?

I would very much like to avoid testing that, because it just would be a lot of work to desolder and resolder everytime,.

It's a single ended heaphone amplifier.

Hi guys, I'm actually planning on building my first speaker, and on the electronic site I use to command the electronics componants I found a bommer (22-200Hz) which seems quite nice and is cheap (I have a low budget ^^). I was wondering if you could help me get informations on this boomer because appart from another link I haven't found anything else about it.

First link :
https://www.gotronic.fr/art-boomer-polypro-wd8-130-31530.htm
Second link :
https://www.e44.com/audio/haut-parl...e-polypropylene-130mm-50w-89db-WRB130SQS.html

Thank you !
Axel

I have a Rotel Integrated Amp, RA-985BX. I bought it new in 1996 or so and thought it could use a freshening up. I found the schematic and identified several smaller value -- 4.7uf, 10uf -- electrolytics. I thought I would replace them with Wima 5mm film caps. Before ordering replacements, I took the covers off. I also wanted to check the ESR on the filter caps in case I needed to order those as well. I figured since I had the covers off, I would preview the project to make sure all of the smaller electros were accessible. Lo and behold they all measure fine with low ESR readings and they are Rubycon Black Gates, which I guess Rotel used at the time as stock.

Thus, I am looking for opinions -- should I swap the BlackGates for Wimas, or leave things alone?

Thanks

Hello everyone. What is the name of this type of amplifier? Received good parameters in the simulator. Please critique.

Looking for suitable replacement FETs to match to replace this double j-fet package? It's a differential pair for my phono mm card in a Sansui AU-X11. Not having any luck?
2N5247 was listed as a good sub, but it's long gone now too?

I am trying to locate the root cause of the buzzing audio sound I am getting when the volume is turned up fairly high with no signal. I have replaced 3 3900 Uf filter caps on the PS board but that did not resolve the issue. Has anyone ran across this? Does anyone have schematics?

Thanks in advance.

I'm working on a portable amp project and am wondering about the feasibility of using a dc voltage multiplier so that I might reduce the size (and cost) of the battery pack.

The most recent amp I've built is a class D unit using the TPA3110D2 from TI. On other portable stereo applications, I've used pretty large battery packs (i.e. 12 NiMH cells to generate 14.4v) But for this next project I'd like to go a bit smaller.

The TPA3110D2 can be powered by as little as 8V (and as much as 26V).

What I'd like to try would be a 3 cell (3.6V) or 4 cell (4.8V) pack, so that the battery could be recharged from a USB port.

The problem here is getting the voltage up to the minimum 8 volts required by the amp chip. Also, if I recall correctly, the chip drew around 0.5 amps when set to a normal listening volume. What's the simplest solution? Just browsing around digikey revealed several dc-dc step-up converters and charge pumps, etc. The only problem was that they were all rated for very low current application (i.e. tens to a few hundred milliamps).

I realize that using a smaller pack and multiplying the voltage will result in limited usable time per charge, but it seems like it might be worth a shot. The 12 cell NiMH packs are great for battery-life, but they're a little big and expensive.

Thanks!
-Chad

I purchased this oscilloscope about 2 years ago and have used it occasionally. I think I turned it on twice in the last 6 months. Time to clear out my stuff.
Comes with 2 original probes and power cord.
Works as new.
I have the original packing materials.
I'm not sure if I have a print manual.
https://www.keysight.com/us/en/assets/7018-05520/data-sheets/5992-1965.pdf

SOLD

Hi,
as I move back to Germany in the beginning of February, I want to sell my DAC, as it otherwise would sit 3-4 months in custom waiting for clearance:

Schiit Yggrasil, silver
Multibit DAC with Closed-Form Filter,
Analog 2 Boards, Gen5 USB, (Newest Version)
EU plug, 220-240V (50/60Hz)

I bought the DAC in May 2018, and it came with 5 years of warranty, so more than 3 years are left.
The DAC is in like new condition.
You can have a listen to it in Sao Paulo.

As the DAC is in very good condition, has >3 years of warranty, I would like to have 2400€ for it.
Cheers Matthias

This has been floating around my computer for a while and I'm just not sure it's an Apex design. As you can see, the schematic is missing information and a couple of connection points. There's also a couple of pcb's that do roughly match up with the schematic, but are different from each other. Anyway, was hoping someone might know the information on this circuit. Thanks.

I change plan of using this https://www.hypex.nl/product/fusionamp-fa251/155

to this https://www.sweetwater.com/store/detail/XLS1002--crown-xls-1002-power-amplifier/reviews and this
https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd

Advice welcome.

I have one sub, with plans to grow it to 4. The mini will have me covered. and I read it will go to 10 hz.

I have a feeling the amp crossover directly to subwoofer won't be enough. Some boost is necessary.

The pairing looks capable and its budget conscious to me. These days most welcome.


I want to built build one simple micro cube (sealed) every couple weeks until totaling four. A pair of 1002 xls should easily power them, the minidsp will filter just whats needed. I feel like playing with 8 inch minis because I already had one nice one to start with. A single start up 15" jbl experiment will be later down the road. If subwoofer play stays in action. I had intentions to build a two channel that simple and sounds good. Now it could use some bass. It still sounds great, the novelty soon wears off. Theres that plus I tested a sub with the system, it sold me on the whole idea in an instant.

Digital Voltage readout is not working, digging deeper I came across a few random BJTs testing bad in circuit, I’ve tried looking them up online but can not find out which these are, each pair of PNP & NPN is marked “D9D” and “B9D”

any help identifying these or links to a source that can help me identify these and others would be very much appreciated.

Ty 🖖🏼

Glassware ACF-2, fully populated except for output coupling caps. Currently configured for 6.3 Volt heaters (6922, 6fq7, etc) with 6.3 VAC heater input. Includes User Guide and various extra resistors for R2, R4, R5 and R7. Asking $60 plus shipping to US and Canada.

I'm building an M2X amp. I need a pair of speaker posts, but searching for "speaker post", "speaker terminal", "speaker jack" on mouser, digikey, and don audio, isn't giving me anything useful.

The ones in the amp camp amp would be fine, see step 4
https://guides.diyaudio.com/Guide/Amp+Camp+Amp+V1.6+Build+Guide/5?lang=en#s132

if someone has a brand that they think is better, I'm all ears.

Downsizing our home. Designing open baffle speakers for a smallish 13 ’x 14’ room. Considering the Lii Silver 10s or TB W8-1772s. Anyone compared these in an OB? I know their Qts is a bit low, but they’ll be augmented by OB 12” powered servo subs mounted on the same baffle. They'll be powered by a (1.5 - 2 watt) 45 SET amp.

Both the Lii Silver 10s & TB W8-1772s have good reputations, but different strengths & weaknesses. I’ve not heard either or been able to locate any direct comparisons on the net. Can anyone shed some light on these 2 in an open baffle with a flea amp? Thanks.

There is demand for Aluminum knob .
many countries dont have it online or offline

So i have created a metalknob with diy method .

-no laathe or solid Aluminum needed
-just metal scissor and dremel
some super glue,putty ,silver powder

process is easy to understand from pics

An alu- L shaped braket was cut for outer and top sheet of Aluminum

paper based lower former is made with glue.

make the metal surface rough.
glue top plate
then glue peripheri with caution
lastly you make 2holes for end fixof periphery plate.

use resin or strong super glue .
All will be done with small gap at the edge.
fillthe cap with putty+silvepowder or paint.

let it dry.
final look will be solid metal
--
now we need tomake it heavy
we can use cement fill half and use a epoxyputty to make shaft hole.
i will give more detail on how to do shaft hole in next posts.

(it is for people in need ...whoever can buy online they can skip this)

I have a hd750.1 with and few outputs shorted and the power supply torrid raised off the board. In a few of these I have found that the torrid had broken completely off repaied them and the amplifier worked. This one has a open or burnt resistor directly behind the torrid R592 I need the value of this resistor it's defaced so I can not make it out.

I am considering upgrading op amps in my lm 502 dac. However the dac has two selectabel outputs: transistor and tube. Does any one know if the op amps are in the commen path of the two outputs ore only the transistor output?

Jason, Gianluca & Co.:

What is the height of a baseplate for a Dissipante chassis? I am planning on building a Wolverine amplifier in a 3U 400mm Dissipante chassis and will use a baseplate (edges down, flat surface on top). The Wolverine uses a variant of the UMS hole pattern (which HiFi2000 will be asked drill into the heatsinks) and I would like to verify that the distance between the top of the baseplate and the center of the lowest drill holes in the UMS hole pattern is large enough to fit the Wolverine's power transistors (it appears a minimum distance of about 7mm is required when insulators are taken into consideration).

Regards,
Scott

I've been renovating a Quad 405 for a couple of days. Recapped it, installed a OPA604's, changed the D1 and D2 diodes and lowered sensitivity. Installed the boards and did some initial test, everything looked fine. DC offset sat at -0.8 mV and the other board at 1.6 mV. I let it sit idling for an hour yesterday evening. Plugged it in today and let it idle for a while, again DC offset looked fine on both channels. Moved the unit to test with a pair of speakers, but before that I thought I'd measure DC offset a final time. Plugged the multimeter to the left channel, set it at mV and turned the amplifier on. The DMM immediately went OL, and I heard a pop from the amplifier. Turned it off, removed the hood and smoke was coming out from it. Was sure I had managed to short circuit it with the DMM, but I had not it turns out. R22, D5, Tr4, Tr5 and Tr3 have all gone up in smoke. R35 looks cooked too, Any ideas what would cause this? I've checked my soldering more than once, no solder bridges, no cold solder joints. Everything is installed with the right polarity. I feel really bummed out about this to be honest. The board number is 12368 ISS 9. EDIT: I see now when inspecting the board that R35 has a cold solder joint, would that cause these components to go up in smoke?