Hi everyone.
Owner of an early 90 (apparently 91) Revox B77 mk2 1/4 (4) track NShere. Recently serviced (electrolytics, pinch roller,motor bearings etc) and properly callibrated. All good, clean and perfectly working.
But i’m only using the machine for hybrid recording (just some passes of tracks for analog flavour), so i was thinking about converting it to 2 tracks. Since i don’t care about listening to 4 track tapes.

1) Am i correct to think that a 2 track normal speed machine is better for recording than a 4 track normal speed?
That mod seems pretty straightforward. Just swapping the headblocks, the oscillator pcbs and maybe changing few small things on the recording-reproduce pcbs. I can find cheap used headblocks and i can sell or swap mine. Mine is used in great condition so i expect to find one in similar condition as well.

2) Is the HS conversion so difficult? There are used hs capstans in good prices ( i can also sell mine or swap), but there is a debate about different placement on the b77 chassis (modification) or not (people say that it can be done on the same location on the chassis) , different motor (i could sell or swap if needed) or not (people say that thevsame motor works well, and it’s really confusing. Of course the speed pcb needs simple mods but that’s easy.
It’s hard to undersand what can be modded in a diy way, when most opinions come from “audiophile“ people (and ultra detailed techs) who don’t like “down and dirty” diy (i mean i wouldn’t mind a revox with extra heads as an echo - dub machine), and it’s hard to figure out what’s “snake oil” and what’s doable.
In my eyes normal revox machines are great workhorses and not precious collector’s items.

3) is there any advantage from changing the recording eq from nab to iec? Is it doable in an easy way (i’m based in europe- so my mains is 230v, 50hz- i read about a mod that mains frequency matters)?

Thanks in advance

I've had this for a couple of years but only used it in my garage system.
Out of interest I Googled it and was surprised to see the second hand value so I have decided to sell it.
There were several for sale @ £130 but before it goes on ebay, I'll offer it up here for £100 plus shipping.
It's in remarkable condition and the only thing that isn't original are the 3 input (function) lights. One of the bulbs had blown so I replaced all 3 with blue led's. They're a tad bright and I'm happy to change them for green ones if required but it really isn't a big deal.
It's a great sounding amp to be fair but I'll find something cheaper for the garage.
I'm in the North West UK.
Can post for around a tenner (UK).
Collection welcome and preferred.

Board just powered up once. It includes latests FemtoMck series 45.1584/49.1520 MHz XO clocks.
Asking 150€ + delivery from Spain
SOLD!

Good morning guys. Anyway I'm undecided between these two amplifiers to connect near a 1500w rms bass face sub. Reading on various other forums and with tests in hand, both deliver about 2000w rms in bridge at 4 ohms. The fact is that I'm a bit undecided on which one to buy. Maybe for stability I would be more oriented towards the ep2500 which would then be an ep4000... I think the ep2500 would maintain lower frequencies for longer than a class D. I saw a video in which the behringer nx3000 (which would then be an inuke3000) was disassembled and there are basically 4 capacitors, it seems strange to me that it maintains all that power.... What do you think? My subwoofer is ground zero gzrw 12x spl https://www.ground-zero-audio.com/en/produkt/gzrw-12xspl/

I bought my brother a restored pair of these amazing speakers. His local high-end guy convinced him to pair them with transistor amps because of their power requirements. However, his system now decidedly lacks fluidity and musicality and has a clinical, almost digital sound. When I fell in love with the 1+1s, I was driving them with an Audio Research D70. They sounded heavenly (at low levels). We only listen to classical and old jazz. Is there any tube amp that you can recommend with these?

Thank you, and happy holidays!

Form italy. I like pro audio amplifiers and speakers, I would like to write in this forum to talk and learn new things in the audio world!

Hi
I saw a GR video on upgrading some Revel Monitors and one of his hacks was to line the speaker with No Rez. I bought some Acousta Blue+ from Parts Express and lined my Revel M16 with it. Definitely made a difference to the extent that I had to stuff polyfill in the port. Too much bass. Not boomy just a little too deep for my bedroom setup.
Thoughts?

Mitch asked a question in another thread which I think is the most interesting debate in audio right now:

In a nutshell, if two loudspeakers measure the same, why do people have a subjective preference for direct radiators?

Here's some background on this question, from my own perspective:

Seventeen years ago, I worked for one of those failing dot com companies. We didn't have any business, so I would show up to work and study patents all day long. It was a way to kill time and appear to be busy. Just sit at my desk staring at a technical doc for eight hours that looked like engineering work. That's when I started learning about horns, Tom Danley's stuff, Keele's stuff, etc.

I've built a ton of speakers over the years, nearly all with a horn or waveguide, but there's a consistent problem with nearly every one:

They can sound great with great recordings, but with bad recordings they sound mono.

Here's an example of what I mean:



A few years back, I rented some Danley SH50s. They have a fairly flat frequency response and they're really well behaved in the phase domain.



My reference speakers are Vandersteen. They have a fairly flat frequency response and they're really well behaved in the phase domain.

The Danley speakers cost about 20X as much as the Vandersteens. You can find the latter on Craigslist for $300, easily.

On an excellent recording, the SH50s were breathtaking. For instance, you can turn the lights off and put on a track with a really great soundstage, and the SH50 is one of those speakers where the image is almost holographic. Where the center is so solid it sounds like you have a center channel, and you can almost get a sense of "front to back" depth. The dynamics are far beyond anything you would ever need in a home.

The Vandersteen can't reach those highs, the stage is never as well defined and the dynamic limits are nowhere near as high.

But here's the crazy part - on most recordings, the Vandersteen's image sounds bigger than the SH50.

This is particularly noticeable if you listen to crummy recordings. I basically listen to podcasts, EDM, some 80s music, and some punk rock. I don't listen to jazz, or orchestral, or classical.

My 'hunch' is that the much wider directivity of the Vandersteens is 'lighting up' the room in a way that the SH50s can't. Basically the Vandy's can't extract all the information in a really good recording the way that the SH50s can, but the Vandy's are also 'glossing over' the bad qualities of many recordings.

I've built a lot of Unity horns for my car, and ran into a similar issue:

There were some recordings that sounded bigger than the car itself, but there were also many recordings where it sounded like I had a mono speaker sitting in the center of my dash. It's like buying a 2160P HDTV, then realizing that a lot of your favorite movies were filmed with a potato.

What parameters should i be looking at when choosing a woofer that can take some eq abuse?

Hello Gentlemen,

I'm selling my fully functional Ian Canada Streaming stack, which was purchased directly from Ian. The entire setup is in excellent condition and will be shipped fully tracked with proper anti-static packing.

Asking Price: $400 (via PayPal)
This includes all items listed below, along with the licenses.

1. PurePi II: Product Link
2. FiFoPiMa V1.5: Product Link
3. TransportPi AES: Product Link
4. Monitor Pi: Product Link
5. Raspberry Pi 4 (8GB RAM): Pre-installed with GentooPlayer OS (lifetime subscription), including CLTO and Diretta licenses.
6. Acrylic Protection Cover
7. All Accessories needed for stacking.

Notes:

• Individual pictures of the items are posted for your reference.
• Product links are provided for details on each item.
• 18650 batteries are NOT included due to shipping restrictions.

Shipping Details:

• Open to ship anywhere in the world at actuals.
• I am okay to bear 50% of the shipping cost.

My Location: Bangalore (India)

If you're interested or have any questions, feel free to message me. Thanks for looking!!!

I'm in the planning stage of my first multi driver speaker build. I've only ever built subwoofers prior to this so I'm in uncharted waters. I'm wanting to build a pair of 3 way speakers to go with my latest subwoofer build. Its a T-Line , quarterwave (down to the centimeter) and modeled strong well up past 100 Hz so the down low is covered. The initial plan was a 3 way setup 8" woofer, 4" mid and horn tweeter. My question is where it comes to the mids. Is it better to just buy a midwoofer or would a full range driver work better? I'm just trying to make sure every end of the spectrum is covered and aaybe learn a thing or 2 so an explanation of why one or the other would be ideal would be very much appreciated. I'm of the mindset of do one thing, do it well so I question the "full range" would have the same quality sound as a dedicated midwoofer and a tweeter handling the highs. Or am I misunderstanding what full range actually means. Thanks for your time

I ordered a number of modification parts for the ACA Mini based on @ClaudeG and @xhitespirit suggestions and want to pass along the option for a "parts kit" as I bought parts in larger quantities. Since I bought in "bulk", the price is right ($15) as long as I can ship within the continental US for around $5 via USPS ground. The total cost should be around $20, but will require a PM inquiry to be sure of final cost based on shipping. The 3D printed feet have various colors options I can provide.

The kit will include:

• 2qty: Panasonic ECW-FD2W335J PP caps (3.3uF / 450V) as DC decoupling output caps bypasses
• 2qty: Nichicon UHW1E152MHD caps (1500uF / 25V) as PS bypasses
• 1qty: Murata 1433428C coil for additional SMPS filtering
• 4qty: Custom 3D printed chassis feet
• 1 qty: 3D printed Murata coil box
• 1qty: 1 meter 5.5x2.5 barrel connector extension power cord

I also have a bunch of PCBs for sale at super cheap prices if you want to combine the shipments.

Send me a PM with zip code for shipping estimate if you're interested including what color feet you'd like.

Hi,
I have had this Laritech module unused for some time as shown in the photo. It's practically new and I was wondering if it could be useful for powering an Opamp in a phono stage and if necessary if it needed appropriate filtering at the output. Thanks.

Hi all,

Recently completed a build. It's a dual opposed sealed enclosure with some budget drivers. I wanted to experience and measure a dual opposed system to get a better idea of the vibration cancellation and the suitability of the design in the context of living furniture that happens to hide a subwoofer in the future (tables, end tables, coffee tables, ottoman, etc as subs in addition).

Dual Opposed Acoustic Suspension Subwoofer
GRS 12SW4HE Drivers x 2 (Series, 8 ohm, drivers in same phase but physically oriented to face opposite)
Sealed 3.7 Ft^3 Gross | Sealed 2.6 Ft^3 Net Internal (15mm Pine Plywood) | 3.07 ft^3 Effective Stuffed Volume
Qtc 0.770 (Simulated) | Qtc 0.919 (Effective Actual, Derived from Measurements)
500w Power Handling





Login to view embedded media
Very best,

Hi All,
I am currently fixing a Rotel RA-930AX. It now seems to be working fine, apart from a slight crackle on the left channel which is evident only when i turn the balance dial to the left. I have cleaned this multiple times using Servisol 10, but the problem remains. I have read online that Deoxit may be better to use, as it removes the oxidation on the fader, as well as cleans. However, there is also some debate over which deoxit to use. Some videos say use D5, while others say F5. Any advice? Would switching from servisol to deoxit likely fix this issue, or do i need to get in there an take the potentiometer apart to clean it properly? Thanks!

From Finland. Interested in all forms of audio FIY, mainly speakers for studio and PA use.

I am trying to install a firewire PCIe card onto the Intel NUC5CPYH mini PC via an adapter connected to the M.2 slot (photo attached). I intend to use a firewire dac with this set up. This slot was previously used for a wifi card which was working ok. I understand that it is compatible with PCIe 1X standard.

The firewire card is Syba-pex30016 with TI XIO2213B chipset.

I have connected the card and provided external power into the power socket of the card.

The problem is that the NUC does not recognize the firewire card at all. In the bios setup of the NUC, it says nothing is populated in the M2 socket. Nothing show up in device manager of Windows 7.

The firewire card and the adapter are brand new.

I am wondering if anyone could give me some advice where to check for problem.

As per title I'm looking to buy LL1667 anode chokes for a project.
Am happy with both the (7) 10-15mA version; will choose driver accordingly.

Another brand anode choke or interstage laying around? Let me know.

Prefer in Europe.

I used to have a few of these, but am having trouble finding them online - may have to just make them.

It's a special 1/4" TRS to 1/4" TRS adapter, missing the insulator between the tip & ring, with the ring being slightly longer to make up the difference.

Purpose: allow a stereo headset to be plugged into either a mono or stereo audio source, with mono always going to both speakers.

They may have been made for something else, but that's what I used them for...

So I've found myself elbow deep in rebuilding this old arc vt60 amp for fun, and as an opportunity to learn more about tubes and how all this stuff works, so I appreciate commentary.

So this amp uses a single bias trimmer for each pair of output tubes. I would like to add individual adjustment, among other things. I've managed to find a few different ideas, and I'm hoping someone can set me on the right track.

1.) Duplicate the bias adjustment circuit, and break the connection between R15 and R16, eliminate R18, add two new 1r resistors between each cathode and ground. (Blue circles on schematic)

2.) Add some cathode adjustment, like they did in the vt65/clone amp, 5r6 with a 100r trimmer. (Orange circle on vt65 schematic)

3.) Order and play with something more esoteric, like an AB-Qi module.

What say you, wise experts?

Hello all.

Not that much discussion on STK components here, the general feel is that with the original designs out of production and stock for years, everyone avoids them if they can.

Is anyone keeping track of which models have reliable Chinese copies and what is pure junk ?

I ended up building my own copy for the STK8050, am currently working on a (complimentary) substitute for the STK2038B and have seen that there have been a couple of other projects on the STK voltage amplifier modules.

Which Sanyo (or Sanken) hybrid modules are really in need of a DIY project due to lack of existing reliable clones ?

This is a series of high performance balanced active volume controls with differential input, ground-sensing output (goodbye cross-channel ground loops!), and a choice of analog or digital volume controls (sample Arduino sketches for the latter are included):

• Dual linear pot (this post)
• WM8816/MAS6116 (post #2)
• PGA2310 (post #3)
• MUSES72320 (post #16)

All versions feature:

• Balanced differential input with excellent common mode rejection - works very well with single ended sources, too!
• Output stage that can be configured as balanced (best for downstream stages with differential input) or ground sensing / ground cancelling (best if followed by a single-ended input referenced to its local ground - the vast majority of audio power amps are configured this way).
• Compact (2.9x2.6in or 74x66mm) two layer PCB, all though hole parts (except WM8816/MAS6116 and MUSES72320, which only come in surface mount packages)
• Can be part of an integrated amplifier (great with LM3886 or similar chipamp based power stages); an output stage of a DAC to form a "digital preamp"; with an input selector, a high performance balanced line stage / minimalist analog preamp.

The schematic is based on Bruno Putzey's Purist Balanced Preamp (aka BPPBP) from his article "The G Word, or How to Get Your Audio off the Ground", originally published in Linear Audio Vol.5. PCB design also follows Mr. Putzeys' method.

Attached are the schematic and measurements for the analog pot version. My soundcard (E-MU 0204) is not good enough to measure the distortion of this thing at 0.0005% at 1kHz - please look at the baseline plots of the soundcard with its input connect directly to its output. Also, note the difference in PSRR between NE5532 and LM4562.

The last plot is one ground referenced channel of a stereo LM3886 amplifier (with one power transformer and one power supply shared by both channels and the line stage) driven by this line stage in its ground sensing configuration. I used my own LM3886 PCBs.

UPDATE: boards are available at HiFiOcean.com.

UPDATE2: a single-ended volume control based on DS1882 is added - it includes a Firstwatt B1-style JFET buffer and a low-noise regulated power supply, all on 1.1x1.1in (28x28mm) board.

UPDATE3: Sample Arduino sketches to control any of the above mentioned digital volume controls are now available on GitHub.

The total dynamic range of a THAT driver and receiver combo is over 21 bits, 20KHz bw, unweighted. They’re made for pro audio levels and systems. 128dB of DR is not reproducible in anything but a very special acoustic environment. However common mode noise down 75dB or so is.

You take your pick and apply technology that makes sense in the specific conditions.

IMO, bothering about THD below 0.01% is tilting at windmills because more than that is baked into all your recordings, and much, much more is added by your speakers. And it’s all masked by the music.

Hey everyone! I guess this is my first post but I have been lurking for a while now. Thanks for all the information that you all have shared over the years! The speaker building community never ceases to amaze me! I have been building car subwoofers for a few years and recently started to develop more "Pro" level subs and have even made a few for "clients" after they hear my own system that I rent out at shows. Seems to be going well so far and I would not have made it this far without the community! I have also been working on my own full range horn speakers and got into 3d printing and CNC manufacturing to make my semi unique ideas come to life!

I can share some pictures of my designs if you are interested and maybe you can tear them apart a bit!

I do have a few questions for you all but I guess they can wait. Mainly regarding some DIY amps that while simple enough, are above my IQ apparently. I'll make a new thread for that possibly after some more digging!

Thanks!

I'd like to buy one of the stereo amp PCBs that are on Amazon. I'd attach a sample but Amazon is crawling with examples, there are dozens of different offerings. The question is: Are any of them known to be at least "decent" in terms of quality?

I'm looking for a utility amp for the workshop and I'm thinking why not one of these modules? Ten or twenty Watts/ch is quite enough for me; but what's the trustworthy purchase? Thanks.

Hi!

I made three types of wiring diagrams possible only to the precious advice of Zen Mod

1) Aleph J ZEN - IRFP150 - 30W

2) Aleph J ZEN - IRFP240 - 30W

3) Aleph J ZEN - IRFP150 - 60W

They have the front end as their common denominator.
1) type 1 is a 30W and has the advantage of being able to avoid MATCHING with IRFP150 that is equal of 2 x IRFP240 inside .
2) type 2 and 3 use the same PCB layout for both 30W and 60W (only the power devices, PSU and heat sink obviously change for 60W), both 24V to 32V RAIL able to operate.
Many thanks to Zen Mod
Antonio

I am from China and I want to learn experience.
I also want to be everyone's friend.

Hi. As discussed on the EL34 Baby Huey Amplifier thread, I'm starting a new GB for the amplifier PCB and separate supply, Mk2.

The AMP PCB is designed to install the tube from the back, version of this pcb is MK2 Rev 1.5-2, bottom, dated 14-07-2019, see schematic. The MK2 version has no power supplies built-in, you need the separate Power Supply PCB. As suggested I corrected R14/R15 to 1K/2W, the correct value for the EL34 tube.
You need One (1) AMP PCB per channel, Two (2) for a stereo amplifier.

The Separate Power Supply PCB is version MK2, Rev 1.5-1, dated 23-07-2019
You need one One (1) PSU for two channels...

Check the PCB images for dimensions.

Add your name to the list and send me a private email. Then I will contact you to get your full name, full shipping address and private email to reach you.
Once we have an idea how many members we have we can have an idea of the pcb price. Prices should be similar to previous GB...

We will see how it goes...Thanks
SB

March 19th, 2021 UPDATE
This GB is now CLOSED

March 20th, one kit still available, one buyer changed his mind...


July 12th, Will place a small pcb order this week for a few extra kits. Already sent email to the few that were interested so far. If interested let me know.


August 5th, Received second batch of PCB and already starting shipping. Still have a few extra kits, if interested let me know.
August 20th, Only one kit left, if interested let me know.

Finally ordered the output transformers for the amp, so I'll be able to test my own PCB. and received the power trnasformer as well.

Sept 9th, No more kit left, but I'm ordeirng a new batch with some other projects, so if interested let me know.
Sept 20th, received third batch of PCB and already starting shipping of two kits. if interested let me know.

Would appreciate your thoughts. Retiring in a couple of years time so am researching on speakers to keep myself busy. Lol

Thanks

Hello all,

First time poster, so please be kind and patient.

I've inherited a pair of Coral BX-200 speakers. They're going to be my first attempt at a refurb. However, one of the tweeters is blown, based on initial sound tests. Would anyone know where I could find a replacement? Or could I replace both tweeters with more modern ones?

Specs:

CORAL BX-200

Many thanks,

simao

DAYTON4 - BUGET SMALL 2 WAYS

ORIGINAL DESIGN BY DUANE BROWN

You can find his design including original enclosure size, crossover components and everything related on Mr Duane Brown page:

https://duanebrowndesigns.blogspot.com/2018/10/getting-your-feet-wet-in-diy-speakers.html?m=1

You can also find the several reviews and variations on this design on several forums...including good comments from really good speaker designers, and also for the Dayton Audio TCP115-4 4” woofer that is used on this 2 way speaker known by the bass it can produce.


The reasons to choose this design where easy:

*A small 2 way with flat response, details and clarity. There is plenty of images with the frequency response and such.
*Components where cheap…i´m in south america so shipping cost are also take in account.
*Few components crossover… i read/think too much about the changes that every electrical component/equipment adds to the sound, this is a series crossover, only 4 parts.
*Small size and Area to be fulfilled… Just a small living room.
*Good reviews for design and components… from designers on other forums and the drivers itself on youtube.
*They are been made as a gift for my Dad (73)…so he doesn't need to get a Beryllium tweeter either way (Even when he deserve it..i cannot afford it)
*Also for my to compare it with a full range MarkAudio speaker that i build on planet10 mFonken enclosure that i REALLY like as was my first diy speaker and i'm still impress on how a good FR driver with no crossover whatsoever sounds that good.

DRIVERS:
Woofer Dayton Audio TCP115-4 4”
Tweeter Dayton Audio ND16FA-6 5/8”

CROSSOVER:
3 OHM 10W RESISTOR
0.20mH 18 AWG COIL
8.0uF CAPACITOR
1.0uF CAPACITOR

ENCLOSURE

I do changes in the cabinet outside dimensions, trying to apply the theory on Direct Radiator Loudspeaker Enclosures by Olson Harry.. also to impress my Dad on what carpentry with cnc can do now days.. the internal dimension where the same that other builder used on Mr Duane design and call it the ¨Deluxe version¨ as he made it a litter bigger and change the crossover components to polypropylene versions on the capacitors. The original enclosure is 8” tall, 6”wide, and 8.5” deep.
The enclosure material is 18mm pine plywood, lining the internal walls with recycled denim, the material used on car trunks/carpets.

I think i don't have anything more to cover so here some pictures of the build process=


FLAT PACK..To call it in that way








The letters on the top are my dad´s name initial..in case you are wondering


Baffle -- recess cut for driver to be flush mount and release on back to let it flow





Binding post cut manually done, as the cnc guy ¨forgot¨to do it...not finished in this photo




Glued together - I'm missing a photo with the internal material--next time i post





Crossover assembly - testing - finished





and the Ufoken enclosure with Markaudio CHR-70.3 that i did as my first diy speaker that i want to compare against this 2way design



I will post more picture as i progress with the process.. hope this week is going to be complete already.
And by the way English is not my native/first lenguage in case it wasn't noticed

I'm looking for an amp or even crossover/dsp with bluetooth control for a subwoofer similar to SVS system. So convenient to dial in dsp from the mobile phone as you change seating positions and set preset eq.
Is there an amp or dsp that does this?

Thx

I was in the audio industry for quite a few years. I am both an audiophile who enjoys music on my modern gear, but love my vintage 1970s, 80,s gear even more. I have restored many amps, cassette decks, reel to reels, etc. and have lots of Teac along with other Japanese brands.

During the last few years I have been playing a little with KiCAD and have some drawings of more and less well known commercial designs, as well as designs from diyAudio and other forums. Many boards have been routed and a few have been produced. So far, some are being built, but only the Pioneer Superlinear has been tested by a friend of mine. Worked fine.

Now I wonder if someone is interrested in a KiCAD Kick start (I know I would, when I started) by exploring my KiCAD project folders? You may download everything or just a little. Use it, misuse it, alter it.... no copyrights on my part.

What I don't know is if there is a time limit or download limit to these Dropbox links. Anyway, we'll find out.

If the interrest is there, I will post the link.

A few samples of produced PCBs:




Cheers!

🙂 morten

Today, an unusual fix (for hifi aficionados like we are), a Fischer Price 820 toy record player.

Someone brought it to me, not working. Not producing any sound from the speaker, more precisely. This machine can work both with 4 C 1.5V batteries and with a 6V DC external power (+ inside). That’s the reason why he took it to me. He had tried to power it with an external PSU, but not knowing its voltage nor the polarity of the plug. Therefore, it has produced a plop and smoke when he lifted the arm up.

The motor works, the platter turns when you lift the arm (like it should), but that’s all I know.

First, 5 screws to open the plastic case. We can see a small PCB, two contact relays, the (small) motor, and that’s nearly all you get inside. Which is enough. Everything else is plastic, rather good quality one. A robust toy.



On the component side of the dirty PCB, I see immediately the 220µF/10 capacitor which has blown up (center of the photo below). Easy. That size, only got a 470µF/16, it will do. Reflowing some solder joints, little bit of PCB cleaning, resoldering all wires. Give a try, not working. Ah.



It’s more complicated than I thought. Got to investigate a little bit more. I like it, kind of too simple if there's no sweat at all...

First, try the speaker on its own. It works. Then going backwards, I injected a 100 mV 10 kHz sinus signal on the PCB points corresponding to the red and black wires coming from the piezo pickup and I could hear some sound coming from the speaker. So at least I knew that the amplifier part of the circuit was OK.
So the problem was probably with the wires from the pickup to the PCB themselves. And it’s the tricky part, because to access to the pickup wires is rather uneasy, to say the least.

I had to unsolder the two wires on the PCB to let some room to get the arm out, then take it out (circlips, platic parts and so). This step is rather uncomplicated. Next one is more challenging. Once I had the arm apart, obliged to cut delicately between the superior and inferior plastic parts of the arm with a cutter to separate them and access to the pickup connections themselves (no screws, sorry). Continuity was OK through each wire, but. But of the 2 contacts of the pickup itself to one of the wire, no continuity.

There is a small metal contact linked to the wire that is supposed to make contact with the pickup.



One of them was not bent enough to be able to touch the pickup contact. I bent it more with a very small plier, and then, there was continuity again. I tested roughly with my finger gently brushing the tip, and I could hear a sound from the speaker. OK, I like that better.

After I cleaned all the moving parts in the arm and greased them lightly, I glued the inferior and superior parts of the arm, reinstalled the whole thing back, and had a try with a record. Everything was right, nearly good sound. Tuning of the 45rpm and 33 rpm speeds with the two dedicated trimmers, general cleaning, screws back.

video Fischer Price 820 (YouTube)

That’s it.

That post helped me a lot : fisher-price-816-record-player-repair

Thought this was interesting if not entirely practical.

https://hackaday.com/2025/01/05/perfecting-20-minute-pcbs-with-laser/

Hi All,

How do you measure bust decay? what are the best practices?

I am using a measurement mic and the REW Spectrogram tab set to burst decay.

I am measuring indoors. (probably a red flag)

I have tried measuring at 50cm, the burst decay is full of noise from room reflections,
I have tried measuring at 5mm from dust cap, there are no resonances visible (I'm pretty sure the enclosure has some resonance)
I have tried measuring at 5mm from the side panel, room reflections dominate the signal and no resonances are visible through the noise.

Do I need an anechoic chamber or an NFS to do this? or is there a clever way of doing it indoors? I have also considered buying one of those portable power station things and taking the measurements in a park, away from all reflective surfaces. The last option doesn't sound very fun, especially as I am trying to compare 4 enclosures using the same drivers so I will be pulling speakers apart in a park...

Thanks in advance for your help,

Another attempt at an amp module for me project, just wanted some suggestions or feedback on it. The bottom half of the board is a ground plane.

Hi there all,
Call me old & rusty [true] but I've only just become aware of Sziklai pair transistor arrangements.
I am hoping that with this Thread I can read and learn more about them.
Any/all info. would be great.

Hey my name is Dane - i have been reading several threads in the past. Just repaired my Burson HA-160D with the help of this forum and will be posting my solution in the concernin thread...

Best
Dane

The KSA1015 is end of life. this transistor was used in repair and updates for some vintage receivers. I could not find a substitute for it. Does anyone know a good sub ???

FS original UDP-203 Linear upgrade power supply, 115V Version, assembled and tested, bought directly from https://www.oppomod.com/

Replace the original Oppo switching power supply, to eliminate all the HF noise induced by the Switching supply, for better audio and image quality. Easy to install, just remove the original supply pcb, screw in and connect the new supply, piece of cake...

Still sell for 360U$, see https://www.oppomod.com/

Asking 200U$ + shipping + Paypal 3.5%

Hi please bare with me I'm dyslexic & adhd but keen to learn thank you

For Sale a set EL34 Baby Huey Amp and PSU MK2 PCB Rev 1.51
Pm .. SOLD

I'd like an amp rig that's based on swappable circuit modules that you can "roll" like tubes. DIY First Watt circuits are an obvious choice for this concept as there are so many circuits to choose from. Other circuits will be great too, JLH, etc. If I create formfactor for this will Papa disavow?

Server rack or maybe Eurorack with pins would be a general concept. For example, a 1U chassis with active cooling, universal PSU and swappable amp/preamp circuits.

For those who looking for something like this

For sale, Borbely Borbely Phono PCB EB-804/419, and All-FET Low Noise Regs EB-707/418, The phono is a two sections, MC front end, and then MM section, all similar using the now well known K170/J74 front end JFET, AD820 Hi-end op-amp for servo, all vishay resistors, Wima cap, etc. A great phono section,

and as for supply the all discrete All-FET Low Noise Regs EB-707/418, with as for final the famous K2013/J313!

Two pcb comes fully assembled and tested, bought them some years ago from an other member.

Asking 175U$ for the phono section and 100U$ for the All-FET regulators + shipping and 3.5% Paypal fee

Just with the cost of the pair of K2013/J313 is it a very low price!

You just need a power supply and enclosure for a killer phono section.

Kit comes with all the docs, schematics, Borbely articles, detailled BOM, etc...

Need to been able to get this working

my modest contribution to this forum...😉

Mauro Penasa

Hello everyone. First a little background on me. I’ve been into audio since I was a kid. From playing guitar with my grandpa to getting my first boombox to modifying audio in my first vehicle. This lead me to a career in car audio a job that I loved and then lead to me doing live sound. I now run production for bands and DJs and am here hoping to learn more. Mostly in the PA realm but other things as well.

Hello everyone.

I'm very new to DIY audio/electronics, and here to learn from this community. My first project is the Amp Camp Amp, and after that I'd like to build a headphone amp.

Hi all. My background is mainly in software and audio recording/production, but I started my career in electronics and have always like circuit design and anything related to audio especially with guitar amps since I used to also be an avid guitar player. While troubleshooting an issue with my guitar amp recently, I came across this forum and not only are there a vast array of topics on this forum, I was very happy to see that it is a helpful community also and looks like there are many members willing to share and help each other out.



-Brandon

New member here. Thanks for the add. I'm also new to diy audio repairs and audio gear collecting. I'm currently listening to mostly vinyl on my SL 1600, running it through a NAD 1240 preamp into a Sansui 5000A. I'm still figuring out the speaker situation. I currently run Sansui SP-3000's on A, pioneer cs-66a's on B, and am rotating some Bose 6.2 or Minimus 7's on C. I picked up a pair of Pioneer cs-05's that weren't great. I'm redoing them with all new drivers and some refinishing of the wood, because I think they look cool, but I'm skeptical that they'll sound great.
Anyway, I appreciate the admission to the group.

I was given a Peavey XRD 680S powered mixer and one SWR Big Ben passive subwoofer (19" 8 ohm). Planning to give them to a friend who's got a couple keyboards & a drum/bass machine. Just for his own basement amusement, not gigging. I have some noob questions about setting this up, as I'm just a guitar dude.
Since the instruments all have L&R line outs, I'd send each side of each instrument to its own mixer channel panned all the way left or right. There are 8 channels. Is that how it's done?
We don't have a pair of monitors. Would it be ok to plug the mixer's 'tape outs' into a hifi 'tape in'? It'll be a raw peaky signal and I'm wondering if we need to run it thru a limiter.
For the Big Ben, my plan would be to run it off the mixer's main speaker outs and use the mixer's graphic EQ as a low-pass. But, to sum the left & right power amp signals, is it safe to use a Y adapter? And since I'm looking for 8 ohms, would I use one output per side, or do I have to sum all 4 power outputs? The mixer has 4 quarter-inch speaker outs (2L & 2R) labeled: "105W/8 ohms, 150W/4 ohms, 30V RMS min amplifier load, 4 Ohms each channel". Here's a pic of the most heavy duty 1/4" Y adapter I can put together.
And please let me know if I missed any other major issues. Thank you!

May I ask for help? And I really hope someone can help me. I have a bluetooth module (QCC5125).
First I programmed it to rename and set equalizer, it worked. Then I tried a second time, maybe I had the wrong program or whatever, and now my Bluetooth module can't be read on the cellphone, but it can still be read USB Port on the computer. Does anyone here have a dump file for this Bluetooth module?

After looking at a bunch of soft start circuits I decided to design one according to my beliefs as to what is the best way to do it. It may be completely different from your beliefs but there it is.

I wanted a separate power supply for the soft start circuit so it could be used to turn the amp on and off and the powering up of the amps large transformer would not interact with the circuit. The transformer has a dual primary so it can be used for 115 and 230 VAC. There is a surge suppressor, R1, across the transformer input as well as a small high voltage capacitor to filter out RFI on the line from coming into the amp. The power supply always draws a few milliamps, it powers a multicolor LED that emits red with the amp in standby.

The on/off switch only switches 15 volts DC at very low current so you don’t need a switch that can handle large AC current in-rushes. When switched on, the DC power is sent through a regulator for consistent voltage and time of circuit operation. Relay K1, a small current relay, pulls in and turns on a triac, AC current flows through a couple thermistors in series to limit in-rush current, two 5 Ohm parts for 115 volts to limit the current to no more than 12 amps, or two 10 Ohm parts for 230 volts also limiting to 12 amps. There is a current limiting resistor, R2, at the triac gate and a RC network,R3/C2, over the triac for some protection of the triac.

The circuit uses a voltage comparator, U2, to delay turn on of a relay, K2, which bypasses the thermistors, I do not like to have a current limiter staying in the circuit or the heat they generate inside the amp. The voltage comparator has a voltage divider, R8/R9, to set the voltage at 10v as the reference voltage on the positive input. That voltage is compared to the negative input which has an adjustable resistor, R7, which limits the current charging the capacitor, C6, and the rate of charge therefore voltage ramps up quickly, a couple seconds to more than 10 seconds, for the delay. When the voltage on the negative input matches the positive input, the output is turned on. There is a diode, D4, across R7 to give a quick discharge path for C6 so the circuit can reactivate quickly, as in the case of a temporary power loss. R2 limits the current through the comparator which drives the gate of a small MOSFET through a gate resistor, R11. The MOSFET pulls current through a large relay K2 to bypass the thermistors and another small relay, K3, which changes the LED from red to blue to show status ON. There is a Zener diode, D5 and a small capacitor,C7, at the gate of the MOSFET to protect and stabilize it, probably not needed but cheap insurance.


So far, the circuit has been very reliable in a couple power amps with 2400VA and 4000VA toroid transformers with .78 farads to 1.2 farads of storage caps. In small part quantities the soft start board costs around $34 USD.
Attached is the Schematic, BOM and Gerbers. Enjoy.

FS Upgrade DAC kit for the Oppo UDP-203 Player, This kit includes a new Audio Dac board -2 CH version, specifically designed to replaced the original Oppo Audio Dac section with ES9038 DAC, with new Firmware.Includes the PCB, custom firmware controller and all the parts, schematics, detailled BOM, etc.

This project was developed by one of the forum member, and the PCB/controller/Dac was sold some years ago. This kit is complete, and 100% compatible with the Oppo, just assemble, and replace the original DAC board.

These mods are still offered by: https://www.oppomod.com/, cost near 1K$...

NOTE: this is the 2CH version of this upgrade, meaning your Oppo player will have only 2Ch audio outputs after the upgrade!

See also my Oppo 203 Power supply upgrade board, all assembled and tested. original cost 280U$ (357$CAN once shipped to me...)

Asking 200U$ + shipping + Paypal 3.5% (Original price was 500U$!)

Hello everyone, i'm from Indonesia.

Hello everyone,
I need a bit of advice. I have the opportunity to buy a NAD 521, which was revised and got an "audio modification" in 2015. The seller asks for €75, with p&p I will end up at around €85 (roughly $90). Its unclear what this "audio modification" means, the seller does not know. I attached a picture from the PCB. The Display looks rather dim on the pictures the seller provided.
Is it worth it? Ist the price okay? The device itself looks very clean and without any damage. I know there are quite some versions of the 521 around, with the plain 521 being the oldest. Should I look for a 521 BEE, which will be around €200 in my area?
I am looking for an affordable, good looking "vintage" CD Player with robust mechanics which can be upgraded with better components. The motivation to do this is more to learn a bit and just for the fun of modding. I do not expect to create something real high-end.
Cheers, Robert

Hello!

Maybe someone can help.
I have Pioneer N-50 and the unit is not booting up,the power button led only blinking,display not working and another leds not working.

Please help!!!

I'd rather build than buy. I'm currently working on an SP-14 preamp from Vacuum Tube Audio and a Gainclone. After those are finished my signal path will be entirely home built other than the SL1200 (which is not without mods). I'm looking forward to seeing what everyone else is working on.

Here's a dual mono Emerald phono preamp from RJM audio that I recently built. The chassis were old serial KVM switches with some figured maple to add some flare.

Hi, what could the problem be with this circuit?



The previous stage has output coupling capacitor.
When I insert the mixer, the volume gets really low.
The mix pot in mid position should be ~unity gain, not atenuation.

I am looking for assembly errors at the physical pcb and cannot find anything by now 🙁.

Hello all,

I'm Kalle from Germany; event technician and building bass cabinets since the early 90s or so...
Bought AJhorn last year and am now mostly using Hornresp instead ;-)

Thanks to this forum and others I built two 15"-tapped horns last year which work very good. Next project are some 18" br/TL-horn-hybrid speakers.

Greetings!

Kalle

Hello, recently looking into all sort of battery power supply solutions

for starting out and getting some kind of reference to go from i wanna build something similar to this one: https://www.aliexpress.us/item/1005005947064087.html for 5V output

consisting of these parts:
https://de.aliexpress.com/item/1005005965787184.html (outputting 5V)
https://de.aliexpress.com/item/1005006246781194.html
https://de.aliexpress.com/item/1005007103958671.html
https://de.aliexpress.com/item/1005005727166588.html
4x Molicel P26A 18650 Cells in 2S2P configuration
2 Switches (like the LHY power supply), one for charging one for load

gathering mainly from google or youtube this should work out just fine 🙂

Hi guys. I have a pair of Townshend Glastonbury speakers from the 1980s. They have been in regular use with no problems.
Well I accidentally nudged one of them and it fell over on its side onto a wooden floor.

The ribbon tweeter still works but the midrange doesn't. I believe it is a Jordan J125 or J150. What should I be looking for? I have the crossover and the driver unscrewed but can't see any dislodged wires. The crossover board seems intact.

What should I be looking for?
Thanks, Stephen

I have a ANK DAC 4.1, which uses a CS814=>AD1865 implementation.
The cheap USB input board failed, so I was planning to replace it with the XMOS based I2SoverUSB board.

But I also thought.. since I am at it, why not replacing the whole DAC board with a XMOS => AD1862 implementation.
The new design would use dedicated separated supplies for the digital and analog sections, and the outputs of the DAC chips would be directly connected to the I/V transformers that drive the original tube output stage, as per original audio note design.

Long story short.. anyone who has experience playing with the AD1865 and AD1862 would suggest one over the other?

Thanks,
Marco

Looking for an Alps RK 50 Quad deck 100 K volume Pot.

Anyone maybe have one

Thank you

Greetings, friends. Today I was hoping to spark a brief discussion on proper heater wiring. This idea came from an Instagram poster known as Amptech74 who repairs guitars and tube amps and probably seen more violently explosive tube behavior than most of us in Hi-Fi land, with the notable exception of @Tubelab_com.

Anyway, here's the idea: don't use the Center Tap that's hardwired into the power transformer. When a power tube fails, the plate voltage is going to find the easiest path to ground. If the plate arcs to the cathode, it still has to go the cathode resistor to get home, but if it arcs to the heater, it only has to fight the resistance of the copper wire. If that voltage happens to pass thru the power transformer, well, there's gonna be damage. But if you are using an artificial center tap, the HV can only cook those 2 resistors, saving your expensive iron.

So. Waddya think?

w

Hello. I am actually an old member of diyAudio but I stopped pursuing this passion for > 10 years and I am not able to recover my old account here. I am a EE nearing retirement age. Most of my career has been spent working on Naval aircraft engine controls with focus on software and electro-mechanical systems. My circuit design knowledge is circa 1985. I was also a dedicated speaker builder for close to 20 years but also stopped that when family and job started taking most of my time. I am getting back into this hobby with plans to recap/revive an Apt Holman One amplifier and some Soundstream D100 and D200 car amplifiers. Hopefully, I will have some knowledge to contribute as I get more involved.

Wrong forum, but just ideas.

Hey everyone. I do live sound production and provide sound for both DJs and bands in many different indoor and outdoor venues. Anywhere from 100-1000 people.

I’m looking for a PA that can accommodate these shows with good results.

I’ve used some of the upper end of the prosumer market in the past and although had decent performance was not quite able to hang at larger events.

I’ve had Yamaha DZR 12s and had them hitting limit at larger shows. I also had one of them die during a show and ended up having to send it in for repair of a blown transformer on the board. A friend of mine also has owned dzr 10 speakers for monitors and has had to send them both in for repair of similar issues. Great warranty but need better reliability than this.

So what’s considered the next step from here? Something over a the DZR SRX series that can push a bit harder and not cost triple the price?

Is it possible to get better than this without spending that much more or does the price just go up significantly after this point?

I’m open to powered or passive options whatever will get the job done best.

Thanks for reading and I appreciate all of your input.

Several times I have seen Scott and others recommend certain optional improvements or tweaks for speaker enclosures, one of which applies most commonly to back horns with shallow driver chambers. The idea is to move the rear surface of the driver chamber backwards (making the chamber deeper) but then displace the extra volume with many blocks of various lengths of wood, randomly, so that the rear chamber wall becomes “bumpy” but the chamber volume remains the same as the specified chamber volume.

For the life of me I cannot recall what this is commonly referred to as, and I am therefore having difficulty finding the method to accomplish this accurately. I would obviously begin by calculating the volume of the standard driver chamber (as designed). Easy enough. What is the simplest method to achieve the desired result?

Dear DIYers,
I need your help with my SF Cremona Auditor.
One of the Woofers is broken and I am struggling to find a replacement.
I search in the web but nothing show up.
Maybe someone have a spare or can identify a proper substitute?

Thanks in advance...
Enrico

Hi . I have a sharp md-xv300 . Original transformer is dead . I replaced a transformer all voltage needs is same except that original transformer has a separate 30v for running filament screen . I have extra pins with 12v and also 25-0-25v that used to run amplifier chip. Screen works with both on 12v i have very load noise and low light screen and on 25v screen brightness is ok but it has also noise but lower . I'll be thankful if there is a solution to solve or reduce noise . Thanks 🙏

A few months ago, I came across a beautiful set of Geloso G-227A tube amplifiers and felt inspired to breathe new life into these rare gems. After a careful restoration, I’d say they’ve come back to their full glory!

I’ve restored them with precision—replacing old capacitors and resistors, adding modern RCA connectors, and upgrading to contemporary speaker terminals. Their vintage casings remain beautifully intact, with just a touch of wear that gives them that authentic retro vibe.

Result is a dynamic and detailed sound thanks to fine-tuned gain stages and high-quality transformers. Powered by brand-new RFT EL34 tubes, they offer a great listening experience.

There is a switch that bypasses all the controls and you can use them as power amps. If in another position, you can use them with their original inputs.

Price is 1100€. We can negotiate and I do accept some trades. Location Croatia.

Regards

Introducing the New Ultra Low Noise Hybrid Power Supply: 2 Channels, 3-15V, 3A per channel.

More details @ www.dxpwr.com

we look forward to discussing the features, applications, and advantages of this power supply.

Hello ladies and gents.




Music and linear power supply has been always a good match . The main problems of LPS is extremely inflated pricing and no data.



You see not all LPSes are equal . Just using a transformer will not automatically give you a better PSU. Worst is that most of manufacturers include no testing . no data that can help chose one.


We mean to change that.




First we started with the transformer . There are many types of transformer , some are worst than others (noise coupling , electromagnetic interference)

We chose one of the best transformers for noise ,r-core



The transformer has a dual output (galvanically isolated ) so you can power multiple devices (RPI + dac , Katana , etc) and we used independent (of course since they are isolated) filtering on each rail. First a capacitance bank (massive) to reduce the 50/60Hz noise , then a active filter , fallowed by an LDO to keep voltage stable . Since LDOs have poor transient and impedance , we used a last active filter (with good transient) and then capacitance but most importantly , super capacitors on the output . So all power comes in fact from supercaps..So yes , transients and impedance of the LPS is..good.


Of course , Shanti includes AC line filter and AC is earthed to casing.



A few words on what we achieved . Measuring noise (in real word scenario) we see about 80nV (0.08uV of noise from 0-20Khz at the floor of our AP machine. This is comparable to batteries from our internal testing .


As explained , Shanti is not only shining because of the ultra low differential noise, but also because of incredible low impedance / deep reservoir of electrons at the output of the PSU ( thx you soundcheck for your suggestions )



At last ... pricing . We are working very hard to make this LPS the lowest priced on the market . All components are on the way , it will take a few weeks to start accepting orders. Questions and comments are welcomed

Hello there,

I get that you use a TO3 insulating pad under a TO3 device so you don't short it out to a heat sink if it is mounted on top of one, but what insulators do you use around the leads/bolts passing through the heat sink?

What type of fasteners are commonly used?

What would be a a good "broad" insulator to use between the board the the heatsink?

Here is an example of what I am talking about,

Thank you,

David.

I ordered too many AD1862N‎ from Digikey so I am selling a few of them

$80/2 chips
$155/4 chips
$300/8 chips

I am currently working on speaker build. Midrange will have enclosure behind it. This is the baffle.Tweeter will be mounted in waveguide on open baffle.I was planning to do round over but as its single 3/4 baltic ply i don't i can do large radius. I was thinking of gluing large quarter round trim instead.Would that work well?