Good day folks,
I have two different amplifiers with different output FETS and drivers but similar symptoms.

• Firstly i have a Soundigital 8k, older silver unit, uses IR2010 gate drivers and IRFGP4072 outputs, came in with burnt power supply.
• Secondly a Soudigital 3k, silver unit, uses IRS20957S and A2 outputs. came in with burnt output filter caps.

Both amplifiers, no shorts found , both were repaired. when powered up they both go into protect, when checked the HS outputs are shorted G-S, all other outputs test fine. After the rails are discharged, the HS output test open. i've replaced the drivers in both to no avail.

Anyone came across a similar problem?

https://www.azom.com/news.aspx?news...paign=3d_printing_newsletter_12_december_2022



dave

Im still pulling my hairs out trying to get some boards I purchased to give a clean signal out. Last night I had this thought maybe its in my approach.
Im feeding a signal say 1V 1Khz into the input and tracking it thru the circuit.
So far only one board has given me a clean output signal.

My questions.
1. Maybe my mistake i that Im not connecting anything on the output of these boards. Im confused. would putting a load on the output help stabilize the signal.
What kind of load should I put ?. A speaker ? A resistor ? A working amp ? I was using a speaker but then a friend told me you never put a speaker on the output of an opp amp. Or if you do it should be a tiny speaker say from a headphone. What if the design has already taken care of this i.e. it has a 100 ohms resistor on the output.
2. What contributes to the oscillations. Power supply op amps or poor component choices with the op amps.
How to I separate my quest i.e. power related noise vs circuit noise. One way I feel is to find a circuit where there are zero oscillations and use the power from there to drive the circuit that is acting up.
I found a nice circuit on a op-amp tester in Elektor.
In fact last few weeks have been going thru old elektor mags. Looking at their articles on filters, amps, speakers etc.
Found this link you guys may enjoy. Good articles on Frequency filters, op amp testers, various amp and pre amp designs. Some good OG articles by Self.
https://ia600804.us.archive.org/20/items/ElektorMagazine/

I would like to share with you the result of my new hybrid amplifier.

The my first version of this my amplifier was made in 2010 then i made some improvements.

The new version uses a very simple and cheap tube driver with 6Z51P or D3a that can deliver 40Vrms with a single tube.

The distortion is about 1.5% at 33Vrms so about 150W on 8ohm.

This project collects all the experiences made in these years then it born with all these characteristics:

• no global feedback design
• passive components without any compromise on any section
• only few parts on the signal path, only 3/4 active components
• very short signal path
• very low output impedance (near to 0.1ohm) for high damping factor (near to 80)
• very high output current, output devices able to manage 60A
• high output power to drive any loudspeakers including ESL, 140W on 8ohm and ?W on 4ohm
• very good slew-rate
• large frequency band, near to 1.5MHz for the IRF820 configuration
• high separation from power supply for all the sections
• power supply separated for each channel
• zero noise
• ultra low distortion in the current amplifier
• zero dc offset, dc servo loop
• no fuse on the signal path
• no relay on the output signal
• only a single vacuum tube for the voltage amplifier
• only one interstage capacitor on the signal path
• high input impedance 110Kohm
• high voltage gain able to be driven directly by any source
• voltage stage and driver stage working in pure class A operation
• high efficiency near to class AB
• compact chassie

Good day
I’m building 3 way system :
Hf- faital hf10ak+ sth100
Mid- radian 950 + k402 horn
And LF i can’t choose between AE TD15M and Faital 15pr400
There is faital dealer in my country, so i can buy pair of 15pr400 for 460 usd
AE is 750usd for pair + 300 usd shipping to Ukraine with tax
I can pay the difference between them but i need to know does it worth it?
Are AE woofers much better?
Thanks in advance and happy New Year!

I'm listing BD15 woofers for sale new in box and never used. these are made by Beyma in Spain. actually it's a customized model of Beyma 15Mi100 with a underhung coil and ND magnet and curvilinear cone
price is 700Euros/pair.

Hi

I've got an old Logitech "Z Cinema model: 980-000085) and despite the cheap looks it appears to be fully active system.
There´s separate amps for tweeters (AB?), mid/lows (TDA8920) and sub (TDA8922).

Its born with and USB-interface and I would like to convert it to analog inputs.

The central ADC is 4-channel and I'm pretty sure thats 2 channels for sub and 2 channels for satellites.
I have not traced all circuits, but there is a PCB-section that look a lot like an active cross-over implemented with opamps.
I'm hoping that all cross-overs are implemented in HW, -and that DSP-functionality can be bypassed completely...

I would say that based on HW this system must have some potential, but it would be VERY helpfull to have complete schematics.
I've tried all my normal goto-sites for schematics and service-manuals with no luck.

Any ideas?

Kind regards TroelsM

Hello, to make room for the Christmas tree I had to move the whole stereo rack, now I find the sideboard occupied by the TV with little space above
Could any of you give me some advice on some small class d or FDA amps that I can buffer over the Christmas period?
Thank you

Hi there,

I would like to know if there's anything out there that must have 7.1 or at least 5.1 minimum outputs and with 7.1\5.1 analog inputs that is class D and must be dirty cheap, don't need too much quality or too much power, just something OK as it's only mostly for gaming to connect to my PC soundcard analog outputs.

And I need it to have separate volume control per channel and crossover settings pear each pair of speakers (Front, Side, Rear and center separately).

I have a Receiver that does this all but it's way too big for my room, it's inside my wardrobe for years since I bought it and I don't need any of the TV and many other extra inputs\outputs that the receiver has...

ps: I don't even know what I'm looking for but never found such thing yet and like I said must be super cheap like around 100€ max even if I have to buy used and must be from EUROPE.

Thank You
guily

Some "leftover" audio boards found. Audio DAC, AKM4393/LME49720. New, premium passive parts, tested, works great, only needs transformer. S-PDIF input, audio outputs.

Price 30€, shipping ( registered with tracking..) 5€ for EU, 7€ other countries.

Regards, Davorin

Acoustic Reasarch tonearms. Made by Jelco, not sure which model, were used on Acoustic Research turntables like EB-101 and similar.

Purchased 10 years ago by some closed USA audio repair store. New, but not complete, without lift. ( Jelco JL-45 fits perfectly.) Otherwise totally functional, antiskate, wiring, mounting base..good bearings, all metal aluminum/bronze.

Have a few of them, god price for DIY, if someone is interested, send me a PM.

Regards

Yes Qts below 0.5 yields a start of roll off that is higher (given the same Fs) than higher Q which results in a higher -3dB frequency. But looking a response simulations the difference in -10dB points is not as great and I suspect that the -10dB point is really the more pertinent figure especially when room gain is taken into account. But on top of that many times the low Q drivers tend to have lower fs which further mitigates the issue. It may even be that the low Q slope more closely matches the slope of room gain in normal "leaky" rooms.

I may need to do a bit of experimentation. Have you guys found the bass extension of low Q sealed enclosures to be really lacking or not as bad as it looks? Thoughts?

Hello,

Need some help understanding what i do wrong here.

Long story short.
We have made some PCB for the 9028PRO chip. Works perfect and sounds good.
For 1.2V DVDD we use this: input 5V -> 1uF X7R-> ADP-151 1.2V -> 1uF X7R. This provide the 1.2V to chip and we have some 0,1uF around the legs of the chip.
ADP-151 can provide 200mA output current and input volt can be up to 5.25V and 9028PRO spec say 82mA at the DVDD. I have looked at DimDIm's post and I know that higher input kHz takes up to 200mA, But we only use 44.1kHz.
All fine up to here.

Anyway, we tried to put in a 9038PRO in the same PCB (AVCC is ok and can handle up to 600mA).
With the 9038PRO the ADP-151 can't provide to output 1.2V, We get something like 0,9V.
So our first ide was that for some reason 9038 need more then 200mA current for DVDD. In the spec it say something like 128mA.
But if we "break" the PCB circuit and lower the input volt to ADP-151 to around 3.7V (from 5V to 3.7V) it's working ok and we have 1.2V.

How can that be? Lower input gives ok output (1.2V), but 5V input only gives 0,9V output.

Sorry if the "story" is impossible to understand....

BR//

Daniel

I made some Salas L adapter circuits on placed them on a raspberry pi board outline for my music servers that run Moode Audio. I have made some new ones with a changed component footprint positioning to better suit the other boards in my stack, So the old ones are for sale if anyone is interested. I will list them as I swap out my old ones.
The 2 white connectors supply 5VDC. one has a ptc fuse on it. My Pi running Moode only drew about 500mA. If you were drawing more you might need a bigger heatsink. It was supplied by 9v dc by an old linear wall pack. It has a toggle switch on the 9v input for off and on.

Hi!

Is there any available processor that is similar to Jim Bongiorno's Trinaural?
https://www.sst.audio/new-products/trinaural-processor

I will set up 3 speakers but the source of sound is traditional L+R stereo. Mostly, I need Mono sound but also light fill-in of left and right stereo. Advice on how to get this?

thanks!

Question regarding the proper way to ground the Modulus-86 amplifier

What I have done so far. I very slightly enlarged one of the many holes in the anodised? steel floor of the chassis just next to the toroidal transformer which is mounted vertically. I then sanded the underside of the floor around the hole and inserted a brass bolt 25mm x 4.8mm through a brass washer and inserted it through the floor. I added some star washers and some brass nuts – similar to the diagram below. I then crimped and soldered a ring to the purple transformer shield wire and added it to the post. I then ran a green and yellow striped 17 AWG wire from the green J1 receptacle GND on the Power-86 to the brass post.. Now this is where I have been getting conflicting “advice”. Person A claims that this is all I need to do. But Person B claims that I should not use the brass post at all and that I should discard it and just run the purple transformer shield and the wire from the J1 receptacle GND wire directly to the GND pin on the rear of the fused ON-OFF switch. But when I look at the Design Documentation for the Power-86 at page 18 (for 230/240 V operation) it seems to me that I should be keep what I have done with the brass post and now run say a 17 AWG green and yellow striped wire from the brass post to the GND pin on the rear of the fused ON-OFF switch? See the Screen Grab of page 18 of the Power-86 documentation. Appreciate some advice please.

If you have some for sale, please contact, thx.

I'm currently building a LM3886 amp, which is great. But it's a bit old now, so I'm just curious what else people are playing with these days? Is it still a pretty reasonable amplifier solution, or what other chips/solutions are people messing with at home? Thanks!

Hey!

I am quite new to the speaker building community but I wanted to take on a challenge. I am looking to build a pair of cabinets similar to the old Altec Lansing 612 cabinets, they are going to be ported and I want them to use an 8 inch driver (or something within that ball park). The drivers are going to be powered by a TinySine TSA7500 Class D amplifier (or anything similar, I have been playing around with the idea of using TinySine TSA3118B(TWS/Apt-X) amplifiers to get true wireless stereo as well.

What I am now looking for is a full range (or maybe a coaxial) driver that is preferably 8 inch, but I could go down to 6.5 inch as well. I recently visited a store that was using the Seas T18RE/XFCTV2 and I really liked the sound of them but they are a bit out of my budget. I am mainly looking for something under $100/driver, but worst case scenario I could go up to $150/driver. It doesn't have to be the most high end speaker, but I would like a good bass and decent high end. Do you guys have any advice?

I currently have a subwoofer box mounted to the floor joist in my living room under the couch for the home theater system . This box has two twelves' , one sealed , one ported . I am thinking about getting better speakers and running them IB . My question concerns the living room / basement distances and the sound canceling possibilities..., the two are separated by a door equidistant from the proposed speaker location at 16ft , so 32ft total distance . I suppose what I'm asking is , if the wavelength at certain frequencies will cancel too much when the separating door is opened to allow heat from the downstairs stove to migrate to the upstairs .

I'm looking to buy a pair of F5T v2 gain stages. I have a chassis with the output boards and PS. Hit me up if you want to get rid of some. Prefer on DIYaudio boards.

As an education "in physically building a crossover" to myself I'm going to make crossovers for an existing pair of working speakers. I will outboard the crossover and might set it up to be bi-amped for no other reason than to do it.
What I need help on is identifying these inductors! I'm going to guess identifying them from photos might be asking a bit much... But figured worth a shot.
While I could simply reuse the inductors and build them into the crossovers I'm going to make i don't want to touch the existing crossovers so I can do comparisons afterwards.
The speakers are Wharfedale 512.2's circa 1990ish. 1"tweeter, 4.5" mid and a pair of 8"woofers, ported box.
Tweeter has 4.7mfd cap inline and the smallest inductor (not labeled laying on it's side) in parallel.
Mid has the resistor followed by 32mfd cap followed by inductor labeled "40" in series and then the 12mfd cap and inductor labeled "39" in parallel.
Woofers have the solid core inductor labeled "50" (I think that's what that number is???) And then both woofers in series.


Yep, sounds like a wacked idea I'm sure but it's just as a learning exercise...

Everhard.

Hi,

For Sale 4 drivers Magico 7" 4oHm, from Magico Q1 loudspeaker.

Magico Q1 - Acoustic Tuning

Magico Driver:

Voice Coil: 3" Former Titanium

Copper Sleeve

Underhung Magnet System

Xmax: 10mm

New.

Price: $8000 ($2000 per driver) + shipping.

Drivers location Israel.

Best regards,
Boris.

Can I replace 2n3773 with tip 35c without making any changes in the circuit board? Is 18-0-18 volt 5 amps transformer enough to power it? Please help.

I im stucked with this amp, the PS fets was burned i checked the square signal in Gates with a scope an was ok, 4.3 volts DC, anyway i changed the PS driving transistors

i got the same square wave sinchronized,*when one is high the other is low.

My problem begins when i installed fets with p75nf75, and they got hot quickly so i tried with irf3205 with same hot results, i installed all fets but with the overheating problems i installed one fet per bank steal with overheating problem i have to clamp the fets, i detected when the fets are installed i have no signal coming from the pins 11 and 14 from the sg3525.

i can not make the PS to work, the fets are clamped so i can make a measurements, the rectifiers tha goes to the output section are out of the board with no change

this is are the voltages coming from sg2525:

with out fets in board:

1. 0.03 v
2 5.12 v
3 0.01
4 0.25
5 2.07
6 6.02
7 2.05
8 4.82
9 5.53
10 0.02
11 4.41v
12 0.000
13 10.61
14 4.41
15 10.01
16 5.10 volts

4.42 volts in gates

with fets:

1. 0.02 v
2 5.08 v
3 0.01
4 0.25
5 2.07
6 6.02
7 2.05
8 from 0.5 -- 0.8 volts
9 5.22
10 from 0.07 -- 1.07 volts
11 0.02v
12 0.000
13 from6.7---10.61 volts
14 0.04
15 from 6.54 to 10.01 volts
16 5.10 volts

i suspect the toroid transformer can have some problems
i checked diodes and zeners driving transistrors ressistance gate reistances, i removed the diode bridge thath goes to both of the 15 volts regulators.
but im lost at ths moment i can not make the sg3525 give signal in pins 11 and 14 with the fets instaled, i checked to the lm393 involved with the protection circuit an all voltages seem fine, even when the amp starts remote to positive, the red led turn on for about two seconds then the blue led turns on and the red off, the blue led stays on but dimming constantly.

Hi there, I would like to build a variable (preferably) pad in order to get signal from a mixers rec out ( mixer master audio MM1210 only available output) to a wireless microphone input, whose receiver would be on a dslr camera nearby. In this scenario I have to also sum the 2 channels to one. I was thinking an l pad in order to achieve near -40db attenuation and 2 1k resistors on each channel to sum them up. Will this work? Any advice is very welcome.

No longer need.

Anyone have any experience with this kit?

https://meniscusaudio.com/product/continuum-ii-loudspeaker-kit/

Good morning and happy Monday, y'all! I hope everyone had an excellent Thanksgiving this year. 🙂

Before I get into it, I want to thank Victor Kung @ VKAudio for his assistance and patience in answering my questions, particularly about Capacitor upgrades. His knowledge is invaluable and he's a good guy to have in your corner when you need help. I also want to thank TubeDepot which is where I purchased my kits from. Honestly, if I'd have spotted Victor's store earlier, I probably would have purchased directly through him. However, I have no complaints whatsoever with my transaction as TubeDepot has always provided me with great products at fair prices.

With that done, I'll move on.

I've been an audiophile for more than 35 years. Music is the one thing I can depend on to get me through each day. It make a bad day turn good and make a good day even better.

Now, I'm not an audiophile in the "I own a set of Infinity IRS-V speakers powered by 3 Macintosh Amplifiers" sort of sense. I would love to be there, but that's a financial commitment I'm simply just not able to justify. However, I absolutely love how a quality sound system can bring out deep emotions, stir up memories of people and places, and transport you to another time. It has that much influence.

Until recently, I've always been a solid state kind of guy. Part of the reason is that the generation I grew up in was on the leading edge of Transistor technology with vacuum tube well on their way out the door. In fact, about the only thing you could buy with vacuum tubes in the '80s were guitar amps, and even those were rapidly declining in favor of the less expensive, sturdier solid state equipment. I do remember as a younger child, my parents and grandparent having old vacuum tube equipment, and I would spend many hours listing to records on this equipement. This probably set my mental bar for audio quality.

I guess that the other reason I was into solid state was that I was very big into car audio in the '80s and '90s, and there just isn't any place for vacuum tubes in car audio! I see there are companies that actually specialize in this kind of equipment, but that all seems a bit gimmicky. LOL

A couple years ago, I really started getting back into the idea of analog sound. I have always love vinyl and actually had an impressive collection until our house burned down in 2015 and we lost everything. Almost 40 years of collecting lost forever. Anyway, while I enjoy the analog nature of vinyl, it's always been through solid state amplification. Not that it was bad... In fact it's quite the opposite. It's just that I always did feel like something was lacking. Some level of depth or warmth that I remembered from my childhood that I just couldn't seem to reproduce. So decided to start looking around at what's available.

Vacuum tube audio equipment is clearly big business these days, with companies building preamps, amps, active crossovers, and other stuff that vary in range from hundreds to hundreds of thousands of dollars. The array is as dizzying as it is almost endless. Reviews leave you with more questions than answers, and almost anything with decent reviews will empty your wallet in short order. But the question at the end of the day is, "Is a $10,000 amplifier any better than a $1,000 one?" I'm sure that at the end of the day the answer would be, "Yes, the $10,000 amp is better." But the next question would logically be, "Is it $9,000 better?" In many cases the answer would be solidly, "No."

With this in mind, I started looking at many different amplifiers in the "under $5,000" range. There are a number of what I presume to be quality products on the market in this price range, but still couldn't make heads or tails of what was actually worth dropping my hard-earned cash on. Oddly enough, while researching different amplifiers, I came across a DarkVoice 336SE headphone amplifier in a pawn shop and scooped it up. Even before I plugged it in and turned it on, I was already looking at reviews, schematics, and upgrades to this unit. My first 20 hours into it, I had already order a variety of tubes so that I could start rolling as time permitted. I do realize that this little amp met with mixed reviews, but was mostly positive. I also discovered that there were some very easy improvements that could improve the quality and reduce the idle noise of the amp. I, personally, love this little amp. It brought back that sound I so vividly remember from my youth. The depth and presence that I felt I was missing was restored. Even with high quality digital recordings, there was a sonic improvement. That's was it. I'm now hooked on tube amplifiers!

I figured the best place to start would be at the bottom of the chain and slowly work my way up. After digging around for several months, I came across the TU-8200R Amp kit along with the TU-8500 Pre-Amp kit. I found it intriguing as it was a full-on, build-it-yourself sort of kit that came with everything. The reviews on it were outstanding, and the documentation on component upgrades was well defined and easy to follow. The only pitfall was that some of the upgrade components were no longer available, such as the AMTRANS components, but c'est la vie. The biggest improvements seemed to come from using Mundorf coupling caps and Lundahl transformers anyway, so that was what I opted with for the final build. Tube rolling will come later. Ordered through TubeDepot and then waited for the brown Santa to show up in his trusty delivery van.

I did my process a little backwards, starting with the pre-amp first as I was waiting for my Lundahl transformers to come from VKAudio. Out of the box, this thing is a solid work of engineering. The chassis was remarkably clean in design and fit together well. I may, at some point, disassemble and have the chassis powder coated a different color, but it's great as it is. The PCB is laid out very well, all the components were grouped in nice, organized baggies, and the instructions were very clear to understand. Now, I'm an electronics engineer by trade (digital, not analog), so following a schematic and PCB layout is a simple thing for me. Not to mention that I have a helluva soldering station. PCB assembly and soldering didn't take long, and within a couple hours I had the whole thing put together. Slapped in the J/J tubes, connected my Technics 1200 turntable to it, and hooked it up to an old Pioneer SX-980 with Kenwood KL-777A speakers and then let 'er rip.

I let the pre-amp run for about 2 hours just to let things settle in and then dropped Tom Petty on the platter. Even with the tubes barely even run, the difference was immediate. The sound was warmer with vocals that were more in the foreground. I played this album and then moved on to my next favorite, Pink Floyd - Wish You Were Here. Shine On You Crazy Diamond (Parts 1-5) is my quintessential sound system test. For me, this track reveals the soundstage and depth of a sound system, or even the capability of individual components, and let me tell you, the TU-8500 did not disappoint. I went with this setup for several days, and with each passing hour the pre-amp continued to provide subtle improvements in sonic and tonal quality. I now realized I needed to get the amplifier built!

Thanksgiving intervened and I had to do all that family stuff. While I always enjoy being with family, I was quietly preoccupied with wanting to put the amp together. Our office was closed for Black Friday so I headed in and began the process of assembling the amplifier in peace and quiet. Again, all the details were impeccable and assembly was completed in a matter of hours. I'm a bit of a perfectionist, and since the tubes are exposed in this unit, I spent a little extra time making sure that the tube sockets were level and even. Unfortunately, during my final assembly of all the PCB units, I forgot to solder the bridges on the bottom of the input/output board which left me a little perplexed when I fired up the amp and had no sound. A few muttered curse words and 45 minutes later, all was good.

I've always heard from people that 10 watts of power from a tube amp is like 50 watts of power from a solid state amp. I always took these comments with a large degree of skepticism since I've always argued that "Watts is watts." I guess that it's true that wattage is a pretty stable measure of audio output. But let me tell you right now... This little amplifier that only runs 8 watts per channel sounds better than my 100 watt per channel Onkyo receiver (in stereo mode) running through a set of B&W 603 S2 speakers! Of course, the Onkyo running in 7.1 will simply outmatch almost any 2 channel amplifier for range and soundstage, but in 2 channel mode I would take the little tube amp every time. There is no absolutely no hint of hiss or hum at idle with no input, even with headphones on. It is dead quiet until you feed the signal back into it and then it just fills the room.

I just couldn't believe the quality of the sound the TU-8200R produces at a pretty solid listening level. It's certainly loud enough that I can feel immersed in the music, and that even with the TU-8500 pre-amp on a flat 1x gain on the inputs. I haven't even turned it up to 3x yet, and from what I've read so far, the amplifier can certainly handle the higher input levels without becoming too distorted. I may give that a try tonight and see how well it handles. I expect it may pick up some signal noise, but I can't say until I give it a spin.

As an aside, the amplifier works great with a set of high quality, high impedence headphones. My Sennheiser HD-650, which works fantastic with my DarkVoice 336SE, sounds fantastic with the TU-8200R. Of course, you don't buy an amp like this just to plug in a set of headphones. It's just nice to know I'm not losing anything in sonic quality. My DarkVoice picks up stray interference with the volume turned up and no live signal coming in, but I think that has more to do with being pretty close to my monitors on my computer desk. I've moved it to another location and that noise disappeared. However, I do not get any noise with this combination of pre-amp and amp sitting in the same location, so the DarkVoice might need a little more input filtering. I did install the PS-3249 DAC module and that works just as I would expect. I don't expect to use it much, but it's there if I need it and it doesn't take away from anything when it's not plugged in.

Overall, this has been an absolutely fantastic kit build. It's a pretty easy go, provided you have a resonable level of skill with soldering. The rest is just following instructions. I did take the amp apart and installed the original transformers just for a quick listen, and the sound did have a little bit of dryness to it. I can't quite explain it, but it felt like some of the low frequencies were a little muddled and washed out which took away from some of the depth of the soundstage. I can't say for highs since I have tinnitus (too many years of concerts and loud car audio) and can't hear anything above about 12,000 Hz, but the range I can hear still seemed to be pretty clear and sharp.

Tube equipment is clearly the way I need to go in the future. I got my feet wet and I'm now ready to jump in. Just for grins, I've already ordered and received the TU-8550 pre-amp and will soon order the TU-8900 amplifier. I'm ejoying the building of these kits and have been absolutely floored by the sound quality of both the pre-amp and amplifier. I mean, for the price you just can beat it. And with the ability to swap power tubes in the TU-8200 between the 6L6, KT88, EL34, 6550, and possibly even the KT90 (I don't know if KT120 would work), all with auto biasing, it makes tube rolling a fun (albeit potentially expensive) adventure. But if you're going to tube roll, then this is a great way to start out.

Again, many thanks to Victor Kung, TubeDepot, and also to Elekit and the infamous Mr. Fujita. Excellent work by everyone in bringing this exceptional product to market and making it affordable to the average hobbyist. It provides entry level access to quality tube audio equipment as well as a platform in which to build a solid foundation of understanding how tube audio equipment works. Well done!!!

TL;DR

I bought the Elekit TU-8200R amp and TU-8500 pre-amp kits along with Lundahl transformers and Mundorf caps for the amp. I assembled them and they are *******' AWESOME! Do yourself a favor and get these for yourselves. You can't beat the quality, especially for the price.

Hi,

I have picked up recently a vintage Farnell LT30-01 dual bench power supply from a well known auction site.
It has two fully independent channels capable of delivering 30V at 1A max.

I tested it today and I think one channel is not behaving correctly (maybe usable but I do not think it is ok).

I want to use current limiting facility.
I set both channels to CV (the switch underneath).
I set up first the desired voltage to say 5V. Then I set up the current limit. I connect 10Ohm to the output. and set the meter to show the current.
I expect to get 0.5A which I do. Then I adjust the current limit downwards until the measured current starts to drop. This is my limit setting.
I verify the operation by replacing 10Ohm load with a smaller one. The meter shows still 0.5A but the voltage drops accordingly to Ohm's law.
This is what I call proper operation.

The other channel: I set up the voltage, connect my 10Ohm resitor and proceed with the current limit setting. With this channel I can set the current limit to any value between 0-1A and the PS seems to increase the voltage if I exceed 0.5A which I do not like very much.
Of course I can still set up the current limit to 0.5A (and verify that the voltage is still 5V) and I can test the limiter by trying a lower value resistor - which seems to work ie t keeps the desired current but the voltage drops.

Still, somehow I do not like the idea that if I accidentally turn the current limit pot my voltage will increase too.

Is the unit faulty?

It is not my policy to take the advantage of the seller/force him to pay return postage etc using fleabay buyer protection scheme. BUT I also do not wish to pay for a unit advertised as working and then spend time fixing it...
I'd rather be soldering amplifiers in this time.

A well known speaker on radio and TV in Argentina and South America, went some hours ago in

She was present in a program in ATC (Chanel 7 TV) in 1980 when the picture tube suddlenly forgot gray scales ans colors appeared

Hi All,

New to the forum. I Need to find 4 replacement drivers for the model in the header. Does anyone know anyone that may have 4 Vifa P13WG-00-08 speaker laying around? If you in Canada, thats even better.

Your help is appreciated.

Hi there,
I saw a couple of vintage Coral speakers for sale. They look in good shape in the picture, except that the center caps, which are supposed to look like polished silver, have a dull look for most of the surface, except for the rim. See pic.

Shall I be concerned about the sound quality? Aesthetics are secondary.
Shall I be concerned about further degradation? E.g. is the silver coating detaching and will it eventually flake off?
Is there some kind of service to restore the caps to their original sheen or replace them for a reasonable price?

Thank you.

Ex demo set of desktop satellites and woofer panel. Box, manual ,black with dark cherry trim. Pretty much flawless condition. Shipping weight 41 LBs from 48212 USA . $1100 OBO

I found a Threshold FET 9 preamp at a recycling center (!!!), no power supply. It's in fantastic shape and I have hooked it to a friends power supply and it works. Threshold power supplies are few and far between and not cheap. I would like to build my own. I could backwards engineer the original, or if anyone has a schematic for the original or if there are any plans floating around for an upgraded power supply, that might be a good way to go. It's 18 volts DC but I'm not sure of the amps or wattage required at the output as I can't find much on either unit. The power supply does have a sticker that notes input power select of 120 vac or 240 vac with a max drain of 10 watts. The fuse for 120 vac use is .5 amp, slow blow or 1/4 amp slow blow for 240 vac use.

Any suggestions would be appreciated.

Thanks,

Eric M.

Hello friends! Thank you for allowing me to continue being part of the forum. On this occasion I have in my hands an amplifier of the brand Mtx model 81000d in which I received an irf540 in the output stage, of course it was blown up. The problem is that it does not generate audio. LEDS 399 and 463 turn on, but there is a current consumption of more than 4 amps and the fet that is attached to the board is very hot, I have a sawtooth gate pulse, but I understand that it is normal, at least Turn on the amplifier my supply voltage goes from 12v to 9v, I checked the fet that is on the board and it reads well, tomorrow I will lower it and get the HCPL3120, in the same way I measured them and they seem to be fine but I will try to get them, thank you your help and patience... regards

I've read lots of information that says that once you roughly pass a 300VA transformer, that you should include a soft start in your amplifier. My question is this - is it really needed when you're on 230V like in Europe? Most of the working examples show really large in-rush currents, but they are almost always on 115V AC. If 300VA+ is roughly the point for 115AC when it's needed, wouldn't it be more like 600VA for 230VA? Sorry if it's a remedial question, but since the current is half at 230V AC, it seems like a soft start wouldn't be needed at the same threshold.

Hello,

I would like to experiment with a Power JFET build using the Zen 9.

https://www.passdiy.com/project/amplifiers/zen-variations-9

I'm looking to build it using Lovoltech LU1014D but want to use a current production part.

Can anyone suggest current SiC production parts?

Poking round I found these:

UJ4C075060K3S (N-OFF)​

https://www.mouser.ca/ProductDetail/UnitedSiC/UJ4C075060K3S?qs=hd1VzrDQEGjVfGB6b9i7uA==

UJ3N065080K3S (N-ON)​

https://www.mouser.ca/ProductDetail/UnitedSiC/UJ3N065080K3S?qs=byeeYqUIh0OYOU7Cis0jMg==

Which Power JFET is preferred N-ON o N-OFF?

https://www.akm.com/eu/en/about-us/news/2022/20220420-ak4499ex/

It looks like we will be getting a new "DAC system", consisting of two chips, one doing the DSP & ΔΣ modulation and one being the actual DAC, much like the previously announced pair of AK4191 & AK4498.

So the DSP & ΔΣ modulation will be performed by the previously announced (but never really seen by the general public) AK4191, and the DAC will be done by the new part AK4499EX (which looks like a 2-channel version of the AK4499 with the digital components removed).





So AKM is slowly making a comeback..

I am starting this new thread with the hope fellow forum members will benefit from the work already done, and possibly can help me with the work still ahead.

I too am working on the Ikea Symfonisk hack, mostly because we are already heavily invested into the Sonos system for casual listening.

In my office,I used to have a Sonos Connect:AMP to drive two homebrew bookshelf speakers, but I got curious after reading about the Symfonisk hack. So I bought one, opened it up and hooked it up to the drivers directly and this sounded way more detailed to me. So I bought a second one and from thereon, the project got stuck.

But not before I got a friend to design a 3D printable enclosures to mount the Symfonisk board on the back of the speaker:

(It's a real pity the forum engine ignores the orientation property)

We even added the Sonos signature button panel:


It's got that 3D chique finish, but it's on the back, so nobody sees is. I have to lookup the .STL files and I will post them here later.
As is well known, the Symfonisk is a bi-amp system, driving the tweeter and woofer with separate Class-D amplifiers. The cross-over filter is probably digital, since Sonos offers a feature they call Trueplay, allowing to tune a speaker for the room it is place in. It's sold as a feature, but it's probably a work-around for the bug of using sh*tty drivers in a tiny box.

Now I wonder if this feature can also be used to compensate for a different set of drivers. To do that right, the digital cross-over filter must not only be able to adjust the levels on both sides, but also the cross-over frequency.

And this is where the project is stuck now: I want to measure the cross-over properties, but I lack the experience. I own a Rohde & Schwarz UPL audio analyzer and I have a Sonos Connect I can use to inject the UPL's signal into the Sonos system. There will be delay, so sweeping will not be possible, but it can also use white noise, so that will be the next-best thing.

Is there anybody here who can help me set up this measurement?

I accidentally short - circuited tweeter amp on my Fusion amp. I read that is probably blown fuse which is regarding to Hypex "user non-replacable". And that is exactly how it looks. Nowhere on board I cannot to find something resembling fuse.
Ana experience or should I just ship it to Holland?
Thanks in advance!

Does anyone know the turns ratio on the voltage supply transformer 120volts bin what is the outs voltage ?

I have had my Ferrograph F307 Mk2 from new having purchased it as a student in 1975. So I'm rather fond of it!!
It has developed a fault - the mains fuse blows on power up and a local vintage amps repair firm has confirmed what I thought - the main transformer has failed somewhere deep in the windings.
Replacements are not available so I am looking at a possible rewind. The schematics (attached) indicate an output voltage between A and B of 70V but do not confirm what it is between X and Y. Am I right to think that it's the same? between X and Y. Am I right to think that it's the same?

I have previously built amplifiers dissipating over 32W of heat using porous ceramic heatsinks.
https://www.diyaudio.com/community/...and-heatsinks-using-ceramic-heatsinks.380763/

I wanted to rebuild my Ovation SX 15W per channel class-A amplifier which dissipates 120W as heat. The original SX build used an off the shelf case which was large and heavy so I designed a new one using the technique I previously used in my “headinclouds” KGSShv Carbon ES headphone amplifiers dissipating about 32W. The cases are all 3mm sheet aluminium alloy and the heatsinks are porous ceramic with adhesive pads. The SX rebuild adds two ripple eaters, volume and balance controls and headphone feed while being smaller and lighter.
I allowed 3W dissipation for each Amec Thermasol FCH505010T, so 22 dissipate 66W per channel for a reasonable temperature rise. They are simply stuck on to aluminium plates holding the power transistors and forming part of the case. Of course the heatsinks are now internal so the case needs a good updraught to allow the heat to escape. In practice the temperature rise is similar to the original large aluminium finned amplifiers. The area near to the power transistors runs at around 50°C and the outer heatsinks 44°C.
The case is 375W x 320D x 170H (inc. feet) [14.75 x 12.6 x 6.75in]

I accidentally hit the spam button for a forum. How can I reverse that?

Hi.
I've built a pair of Icepower 200asc amps, and am using these in a biamplified system, with a DAC feeding an active crossover (RCA unbalanced outputl
The 200asc has a balanced input. Since I already have a pair of suitable transformers from another project (Jensen JT11-P1), I'm hoping to utilize these to converth the unbalanced input for use with the balanced amp (FYI, I am not interested in an active solution, nor passively tying one of the 3 pins to ground).
BTW, there are a Red and Brown lead going into the transformer and Black,White, Yellow and Orange leads coming out. I do not see any labels for them).

I see in the manufacturer's diagram (attached) that they show an RC network (13k/620pf) across the output leads attached to pins #2 and #3 (which is also tied to pin 1/screen, input shield).

Q:: Are all these connections and Res/Cap components shown in the diagram necessary and correct for my application?

I have seen other diagrams online that differ greatly, but noticed that Jensen refers to this one as "Best", which I interpret as only one way.

Thanks for any guidance in this effort.

Hi,
my name is Alfred Rosenkraenzer, I worked 36 years as a design engineer, mainly on analog and digital signal designs.
Now I am on early retirement.
I designed two differential current probes to measure the current in a shunt resistor with a scope. These are pretty helpful if you like to measure eg the current in the emitter resistors of an audio power amplifier, or at switching power supplies.
There are two articles about them in ELEKTOR:
https://www.elektormagazine.com/magazine/elektor-201609/39807
https://www.elektormagazine.com/magazine/elektor-159/59112

Attached are some screen shots from the emitter resistor of an amp.
On SCR01 the yellow trace is the output of the amp at 8 Ohm, purple the upper emitter current.
Note the difference in bias current between SCR02 and SCR03. Look at the end and the start of the half sine.

If someone is interested I can send you more info.
I still have some blank boards which I can sell.

Best regards
Alfred

hello,

I have an amp that uses series parallel heater wiring for the el34's
the left to power tubes were one wired lot and the right side were the other wired pair (please see original schematic below)

to save cost for a quad set of tubes I opted to run the amp at half power on only the two center tubes V10, V11 by wiring the heaters as a series/parallel pair, rebiasing and running the output impedance at half. this has worked fine.

I am going to pass the amp on now so I am thinking to wire V9, V12 heaters as a pair so the new owner can purchase a quad set of el34's and run the amp at full power should they choose.

My question is in the design are the V9,V10 and the V11,V12 heaters wired together for the correct voltage because the are situated close to each other to make wire routing easier and saves on wiring ....

Or is it a design rule effecting noise and interference that heater wiring in series parallel arrangement has to be at each end of the output transformer (in quad pp designs)?

please note: I am only inquiring in regards to the heater wiring arrangement,

...........to simplfy can V9,V12 be run as one heater series/parallel pair and V10,V11 be run as the other heater pair (with re wiring of course) without causing poor effects or problems?


thankyou

Hi friends
I am still struggling to understand the math behind ladder attenuators. I once thought it would be easy, but nope, not really. (Not if following/listeningn to the masters at least).
So I have this cool ladder attenuator calculation sheet from Elma, but it's too cool for me: Why are there those "Ladder (no load)" and "Ladder (with load)" options?

Haven't ever seen anything like that although I've looked at I'd say most of the products available...
I believe Master Salas already explained it (here), but I'm completely overwhelmed.
What Load-impedance should I go with, and — why?
(excel calcsheet included as zip-file)

Thank you

Cases and heatsinks are a problem for DIY builds.

I made quite a few amplifiers with thick machined front panels, heavy finned heatsinks and aluminium cases. Such parts need machining and tapping.

I devised a way of making cases, which eliminated these problems and made for easier case design, lower costs and quicker builds.

Cases

Made from sheet aluminium alloy of preferably 3mm so only single sheet of material needed.

Depending on the facilities you have available these can be made manually. I get the parts laser cut by a company which will also supply the material. Alloy 5251 lasers and anodises well. The case parts need holes to be countersunk where necessary and are then taken for surface finishing, (bead blasting and anodising in my case).

I then take the front panels to be screen printed with the graphics I provide. The assembly is with corner posts and angle brackets cut and drilled, and bolted together. I only drill and tap corner posts to attach base and top panels. The case is basically a box with a front panel on to cover the front of the box.

Heatsinks

I became aware of porous ceramic heatsinks and realised that these small, light self-adhesive items would solve problems. I bought a few and tested to see if they did what was claimed. A single 50mm square of 10mm thick could dissipate 5-10W stuck on sheet aluminium. To make heatsinks you only have to bolt the semiconductors directly to the 3mm plates and place the ceramic heatsinks as needed.

Edit; a link to these was omitted, http://www.amecuk.co.uk/ Element14 has them in many countries.

https://www.newark.com/c/cooling-thermal-management/heat-sinks?brand=amec-thermasol

They are not expensive, and with a range of sizes you can arrange heatsinks of different shapes. I was concerned that they might unstick but the opposite has been true, they are hard to remove.

They are not pretty and can be easily chipped so I contain them inside the case and organise slots above and below to act as a chimney to allow convection. This works well and they do not run hot. The porous ceramic devices are very effective.

I have found that this method is much easier to procure and build. The amplifiers built this way can be smaller and lighter. These techniques can be adapted to any case whether needing heatsinks or not.
I should say that these heatsinks are small and they don't weigh much but that each amplifier on either side of the case dissipates about 14.5W and the heatsinks are only warm. (Edit; Further explanation a few posts below)

I am looking for a pair of 12" Peerless XLS or XXLS Woofers.
Peerless Part # 830500 or 830844

Paypal for payment

Is Trends Audio still in business ? I tried to order a TA-10.2P tripath amp but my shopping cart kept going through a loop ?

thanks

I have 7 Behringer DEQ 2496 units in continuous usage in 3 different systems. They conveniently allow me to do a wide range of adjustments I need to do, including parametric EQ, graphic EQ, bass limiting, level adjusting, level monitoring, and RTA. And all with midi controllable setting memories. They are useful in multiway as well as (my kind of) multichannel systems.

Around 2013 I discovered I could even use them to replace the Behringer DCX crossovers I was then using. By aligning two "low pass" filters in the parametric section, you can get an LR24 lowpass response, and likewise for the highpass response. This enabled me to use full digital I/O because the DEQ have full digital I/O whereas the DCX only has digital input. Then I can use the DAC's of my choice (so long as DAC latency is corrected for each way and each supported sampling rate...).

I started with one unit in 2005, added the second one in 2008, and on and on. But by 2010 the first one failed, and for me they seem to have lasted 5-10+ years (some of the latest new ones I bought are still going fine, and I've improved the ventilation with higher spacers, and they seem to have improved the parts quality a bit since 2005).

I never fixed any, I just bought new ones like candy as the old ones failed. I saved them in a big pile for "later when I have time to fix them."

I think the time has come to start trying to fix them. They are unavailable new and the used ones (I have sadly learned) may be nearly "used up" if they work at all. I got exactly one year's use out of the last one I bought on ebay for $200.

The latest one (a year after purchase on ebay) has now died with the "flashing screen" problem. When the unit boots up you never get the copyright screen or anything just a flashing screen. Something like half of the ones in my dead pile died with that problem. Others may have the "blank but lit screen" problem, or the "dead as a doornail" problem. I suspect most or all of these problems are power supply related.

Sadly there is no schematic and no service manual. I have found a multipage schematic of some kind but I haven't seen the power supply on it.

I am going to be taking one apart today or soon to see what I can figure out.

To prevent me from soiling the GB thread GB for Baby Huey PCB I'll be posting assorted pics here regarding my build.

The rounding of the board and the thickness makes for a very nice looking board.

Stop. Don't turn up the volume and beware of concerts. Loud music can damage your ears. So I can only listen at low volume to be safe?

Hi folks. Quick question about DHT filaments. I designed a build to incorporate two switches, one to fire up the filaments, and the other to pass the B+. To my chagrin, I just discovered after turning b+ off, I'd forgotten to turn the filament switch off last evening. Unfortunately, I'm talking vintage 45 globes. Duh. :-( As a general proposition, how much damage have I done? (The amp sounds fine right now.)

So we all know it's going to bite us in the a$$. What are your suggesstions; no..your 'secrets' to overthrowing this madman.

I've had it up to....'here'. 😳

Good morning to the group,

I’m a newer builder and reached another challenge there perhaps someone can share some of their expertise. My latest project is the First Watt F6. I built it and now am in the final stages of biasing the channels. With (2) meters clipped the source resistors and(2) others connected on the speaker outputs, I thought I was golden because I kept watching my heat sink temps were as I ran the bias up and we’re just nicely warm, never hot at 47*C. As I continued to raise the bias, finally stopping at 565/575mv and offset set @ +\- 1-2mv. Everything seemed nice and stable. So after a few different days of monitoring the bias and offset remaining fairly stable. I connected some test speakers, there’s no hum or noise so I played some music. It sounded good. It’s when I went to take my test equipment off I noticed the plastic on my test leads on both channels Source Resistors was literally melted. Shame on me for not noticing sooner and not checking the mosfets sooner. I just assumed if the heatsink is cool, so is what is attached to it. I got my infrared and started shooting temps on the mosfets. THEY ARE HOT, very hot @ 69*C. I immediately backed down the bias on both channels to around 350mv. After some time i checked temps again and they are still super at at almost the same temp 68/69C. Even the hold down washers are extremely hot. I never noticed this on the F5T or Aleph J amps and I will check those this weekend. I checked to be sure my screws were tight and they are. It almost seems like I’m not transferring the heat from the mosfets to the heatsinks. Is that Possible? I guess I should ask, do I have an issue to address?

Greets & thanks to the community, been through a lot of threads that have proven quite helpful.

Hoping I could get input on whether this board layout is functional/optimal, first timer here.

Power comes in via a DC-DC converter on J4 that's mounted to a seperate board.

My biggest concerns are whether the set pin layout is ok, the datasheet suggests a guard ring & I'm not fully sure I've accomplished that here. That and there aren't any great examples of a parallel 3094 layout, so just horked ideas from the 4x 3045 design on AD's website.


I might have to break the whole thing out into a seperate sub-assembly so that I can follow the exact layout of the eval boards? This area is all the space that's available on the mainboard. Are there any designs floating around the forum that would be good examples of a parallel 3094 layout?

Cheers & much appreciate all help and suggestions

Just curious if folks actually go through the hassle of measuring and pairing resistors, capacitors, and transistors used in signal paths in order to help keep everything internally balanced when assembling kits. Since many of the preconfigured kits such as Elekit tend to use 5% tolerance resistors, I was not very surprised to see large swings in resistance between the individual components. There are obviously some locations where a slight variance wouldn't be critical, like for the power supply. However, it seems that anything directly in the signal path could exhibit a balance issue if the passives had enough accumulated variance.

With OCD in full swing, when building my TU-8200, TU-8500, and most recently my TU-8550, I did take the time to value match as many pairs as possible. I don't know how much it really helped, but to my ears I don't notice any balance issues.

Anyway, just wondering if anyone else did this.

I have 6 of the 10M45S in TO-220 package if anyone would like to purchase them off me for $4 each + shipping. Please PM if interested.

I just wanted to share my successful build using the 6HJ5 wired as a triode. These tubes are cheap and rugged, and oh yeah they sound great. The driver is a 6N7 with both triodes in parallel.

I have a SS Slewmonster and Mullard 5-20 monoblocks so this amp is my "colored" sound amp. It has that warmth of a 300b amp. I highly recommend people to go ahead and not be afraid to use this tube for audio. I know George has used them in Pete's big red board but I wanted to share the success of it wired as a triode.

-bird

There have been some attempts lately to make dipole tweeters work up to high frequencies with constant directivity. How high can we go, if the tweeter housing is already almost as small as its radiating area?

I would like to demonstrate the issues involved with an idealized 1 inch circular tweeter. I am using some Boxsim simulations to show things detached from specific driver peculiarities like FR and dome breakup modes.

Let’s start with the mathematical dipole model – first for a dipole distance of 2,5 cm to keep things within 20 kHz:



This is equivalent to this Linkwitz figure.

A 1’’ tweeter would have a physical diameter of at least 2,5 cm. This would lead to a dipole distance of 1,25 cm. As a 2-point source this would sim like this:



Of course a tweeter is no 2-point source. Let’s first move to a dipole point source on a 25x25 mm square baffle (Boxsim can’t do circular baffles).



We can see that the dipole peaks are slightly lower in frequency because a 25x25 mm baffle is more like a 28 mm disc than 25 mm. More important by far is the change in directivity that is introduced by the baffle. The dipole 8 gets sort of slimmer.

Since a real tweeter is not a point source on a baffle, we make the cone/dome/foil as wide as the baffle. Note that our model is working as a dipole membrane in a housing with no depth now. Any real world tweeter would have to be larger:



Note how the dipole 8 gets even slimmer than before and how the dipole peaks move to even lower frequencies. Strangely the 60 deg peak is at a lower frequency than the on-axis peak. Same for 30 deg. How come? The next diagram shows why by overlaying the last two diagrams:



The wider source starts to beam – lower in frequency at wider angles. From a certain frequency up the directivity of the tweeter is no longer controlled by the dipole function but by the tweeter diameter. The next diagram shows this relationship at the first dipole peak:



A monopole tweeter would have a main beam to the front of almost the same contour as the figure 8 of the dipole. This would be true for any driver whose radiating area is as large as its baffle – regardless of size. Any attempt to manipulate the radiation at the sides of the baffle is quite fruitless for frequencies above the first dipole peak – they don’t show up any longer at the sides.

The only cure is to move the first dipole peak up by making the tweeter smaller. Above the first dipole peak all compact drivers will move from the (constant) directivity of the dipole 8 to the frequency dependent directivity of a beaming driver.

That’s how I see it. 🙄

I have been using this schematic for years with great satisfaction.
Now I also need to adjust the current while continuing to use LM317.
Is it possible?
Thanks

Hi All!

this is the first day im using REW.
From the youtube tutorial I've seen, people say it doesnt matter if you put you mic at you sub position, or at the MLP. But I'm getting 2 very different SPL reading.
Can someone explain this to me?

Purple line: subwoofer at its 'OEM' position and Umik-1 at the MLP. noise is set to 75db with the rew generator with pink noise before taking the reading.
Red line: Subwoofer on couch, mic at the subwoofer 'OEM' position. Didn't change anything else except the position of the 2.

Those line are averages from 3 reading for each position. I was doing the exercice because I want to DIY a subwoofer, and I wanted to know if the spot I want to position it will be a good spot. Started measure the "OEM' spot and the MLP to see if they were the same....

So, should I move the sub around and keep the mic at the MLP, or should I keep the subwoofer at the MLP and move the mic around or the reading?

Thanks!

Amp has a few issues with it .

First off the power supply fets are burnt .

The amp has 47 ohm gate resistors for the power supply fets .

The fets are marked CS50N

Anyone know what fets I can replace these with ?

Hi Folks,

Various people have asked about this so here is something I wrote for the maxon AU web site. It is by no means an exhaustive list, although the suggested model families are a good choice there are many variations within those families, primarily nominal voltage, which as explained below can prove critical in the selection process. Also $AUD one off prices are given in the pdf..they are for comparison only. Call maxon for an exact quote as the exchange rate varies. I do not claim to be the foremost expert on this topic, I respect others, such as Mark Kelly for one, have done much work on this.

Maxon Brushed motors for Hi-Fi turntables

Much has been written about this subject and I appreciate that others have gone into considerable detail. The purpose of this document is to put together suggested motor choices available from maxon in one place, and give an idea of the relative pricing. Note these are guide prices only as for example, the exchange rate fluctuates. Also note, we have ‘cherry picked’ some likely motors here, but this list is in no way exclusive. Other motors in these series and other series may be suitable. If you are not sure please call maxon.

Before we start we should outline the basic requirements

1) Sufficient power, ie speed x torque
2) Low noise, electrical and mechanical
3) Minimal torque ripple
4) Reasonable cost

For most people, particularly novices, a brushed motor is a good choice. The control electronics are comparatively simple and as they can be linear, low noise and the cost is lower. The wiring is also simpler, just two wires to the motor. The drive system is inherently smooth and quiet as long as we are aware of some basic points.

Motor Selection

For a retrofit situation we often have little control over the mechanics, the motor speed is much as determined by the original design. In the case of TT’s employing synchronous type motors this may be quite low, much less than 1000 rpm.

This requirement is usually at odds with the brushed motors available, which tend to be high revving when run at their design voltage, typically 4000 to 6000rpm.

Fortunately the solution is at hand. By using a large diameter motor (which provides good torque, and more power than is ever likely to be required) we can under run it from a lower voltage than its nominal design voltage. This will reduce the speed whilst torque remains purely proportional to the supply current. From a datasheet perspective this means selecting motors with a low rpm/volt speed constant, line 13 in the maxon data sheet tables.

Taking the A-max 26 110191 as an example, a nominal 48V motor, this has a speed constant of 127 rpm/V. So we can see that in a typical turntable application (~600rpm) the supply voltage will be only approximately 4-5V. This is perfectly fine as long as the motor has sufficient torque. From the datasheet the motor makes 15mNm torque at max current.

As the turntable belt drive multiplies the torque by 20X approximately this is quite substantial. We could go into more details as regards start up times if we know the moments of inertia, frictions etc etc, but unless we are designing for broadcasting applications this is probably not required here. In most real world situations belt slip will limit the torque in any case.

So we need to look at some large diameter brushed motors, large in this context is ~>25mm diameter, with low volt/rpm..

What else is important? We want the lowest noise, mechanical and electrical. This means minimal brush noise and low torque ripple. So the choice is now towards precious metal brushes (PMBs), for minimal drag, noise and best efficiency, a long life capacitor (CLL) module to prevent brush sparking and as many poles as possible for smooth torque delivery.

Some suggestions, in order of cost, lowest first.

A-max 26 series

A-max 26 7W 13 pole 110191 an old favourite and still a good choice

RE-max 29 series

RE-max 29 9W 13 pole 226779 (bit more power has extended shaft)
RE-max 29 15W 13 pole 226761 (more power for heavier platters, faster start etc)

The RE-max 29 and A-max 26 support both DC tacho (as a special) and encoder options.

RE 25 series

RE 25 10W 11 pole 118748 (with extended shaft, more power smaller size, tacho option)
Can have DC Tacho 118909 factory fitted for closed loop control

The RE 25 comes with the option of a factory fitted DC Tacho 118909, and so if required a true ‘closed loop’ control can be closed around the motor and the speed controller. It is also the most powerful motor for its diameter, which may help in some conversions, although it is also the longest. See table for approximate dimensions.

Speed control.

The LSC 30/2 4Q linear controller 250521 could be used for TTs. It supports I x R mode. This technique provides motor speed control by a form of feed forward. A brushed motor can be modelled as a source of voltage (the back EMF) in series with a resistance (the winding and brush resistance) . The voltage is proportion to the motor speed and opposes the supply voltage. The current is proportional to the motor torque. As motor torque and current increases, and the motor slows, the current increase is measured and used to estimate an increase in motor supply voltage in an attempt to stabilise the speed.

As there is no true feedback control, the accuracy of this arrangement is limited. The advantage is that no feedback device is required, so simple, low cost, and there is no NFB loop to stabilise.

The more accurate option is to use a motor with the Tacho option. Coupled with the LSC30/2 or other DC servo amplifier this would give absolute control of the motor speed. However be warned the combination of a high mass turntable, compliant drive belt system and low motor inertia will make the loop more difficult or impossible to compensate.

Further hints and tips

Check the drawing of the motors carefully in the datasheet to get the exact dimensions; those above are a guide only.

Be careful not to damage the motor when fitting the drive pulley. In particular the shaft of the motor must not be subject to excessive axial loads which might damage the bearings. If press fitting chose a motor with an extended ‘through’ shaft, then the press can be applied carefully directly to the shaft.

Never press on the motor body to press fit a pulley.

Details of all motors are on our web site:
www.maxonmotor.com.au

LOCATED 44405--- BEST OFFER TAKES IT ALL- Everything works....Over $2200 in drivers and $500 in XO parts... XO parts some have booger soldier as i dont have a removal tool. A couple woofers kids poked dust cap- yeah I know it makes no difference- but I wanted to be up front. Theres also 3 more XO "sets" has 3 more 2.o air coils 20uf caps 3ohm 7.5ohm resistors 1.8uf 4.7uf caps and 0.9/1.0 air coils. they are in cabs- hot glued in. I can include the cabs which are 3.

Must be picked up unless you have the means to send boxs/packing with return label im not paying sipping out of my pocket if that happens Venmo or something else. I don't use Paypal

Hi, I have recently built a Elekit 8600 300 tube amp and looking for a new kit for the new year. I would like to build an integrated amp, phono preamp or horn speaker. Price less than $1200. Any recommendations?

Hello, i received a alpine pdx m6 sub amp.. Repaired the filter caps, because broken. Nothing more. Amp powers up, 1,08Amps idle.
Oscilation at output perfekt. Traced input signal from input preamp board to mainboard, also perfect... Must be something between drive ic and mainboard. Expect a broken resistor.
Cant find something. Anyone has a diagram, or had this failure before?

Hi All,

The published specs are 60db so it doesn’t surprise me I’m still in the ballpark.

The analog source is a 1kHz sine wave from a DAC with one RCA plugged into the Aux input opposite of the channel being tested for crosstalk.

I used my DMM to measure AC voltage at the the amp speaker terminals, without speakers.
Measurements are as follows: 170mV vs 0.5mV. Crosstalk is 20*Log(V1/V2) = 50db. It’s a few db worse crosstalk from left to right. I’ve been able to double check my measurements using the amp headphone output connected to the input jack on my Mac, recording that input on Audacity and then running a FFT analysis. The 50 db crosstalk is consistent and gets worse as frequency increases, as expected.

Is the most likely cause capacitive coupling via the L/R channel wires (marked in red) that go from the Input board to the volume control and back? These wires, 3 per channel, converge to a 6 wire conductor with shielding, and a drain wire that is connected to ground. The cable length is about 2 feet. The signal then goes through the mute relay to a pair of wires (marked in yellow) that connect to the left and right Amp sections. I think the sequence is Input to Volume to Pre Out to Mute relay to Amp In. Running in Passive preamp mode. I’ve attached photos with and without the markings. See pages 2,8, and 9 of the attached schematics for reference.

I’m wondering if there is a way to improve the crosstalk? One idea is using a Cat7 ethernet cable which has shielded pairs, outer shielding and a drain wire. Or just running separate wires which would take more space. Or is there a lot more that is causing the crossover? And is troubleshooting 50db really worth the trouble? I should add one motivator to replace those wires is a bigger voltage spike (barely audible) in the right channel when changing inputs. Any help is appreciated. If anything, learning more about crosstalk sources would be great.

I am looking for some 1" sleeve nuts to make a flexi rack,but I cannot find any larger than 1/4". Does anyone know whare I can buy larger sizes?

Hi all, I am teaching myself soldering and how to fix my own amplifiers. I bought a pair of these QSC RMX 1450 VERY used off of facebook marketplace knowing the right channel in both did not work. (suspecting something someone did with bridging at some point in time). I knew these were rough, but they seemed like a good project to start learning on for the price.

When I bought the amps, the fuse for the right channel would blow instantly when powered on (12A) I tested the bridge rectifiers and they were failing so i replaced all 4 (2x on each amp) with the closest I could find to the original rectifier GBPC2502W-ND https://www.digikey.com/en/products...2?s=N4IgTCBcDaIOICEAKBhMBWADGA6gWgDkAREAXQF8g

After I replaced those, the fuse would still blow. then I tested the Bipolar Transistors (8 per amp channel, 16 total per amp) a few of them were failing the test on the bad channels, so I order 16 of them (I did not replace the other 16 on the good channels). 757-2SC5200-O(Q) https://www.mouser.com/ProductDetail/Toshiba/2SC5200-OQ?qs=EEns8I54Y6BCHV7Kwts0vw==&countryCode=US&currencyCode=USD

Success! I can turn the amp on and it no longer blows the fuse! however, after hooking a speaker up to the right channel I got a really loud humming noise coming out of it and then a cap started sizzling and the top popped off before I got the amp unplugged. I let the amp set for a couple days then just unsoldered the 4 caps off of the bad channel and am a little defeated, but again its a learning project and my first time doing something like this.

The question(s) Are:
1. what produces that humming sound I heard?
2. should I go ahead and replace ALL of the caps? (total of 16 caps between both channels on each amp)
3. if so is there anything else I should replace aswell?
4. should the 2 good channels have there 8 Bipolar Transistors replaced too?
5. what caps should I go with and why? I know theres got to be better ones out there since these were made.

Cap Specs: 100V, 3300uf, Nichicon, 25mm x 50mm. the new ones cannot be more than 25mm wide, but could be taller if need be.

I saw this post and thought it was interesting that I could go bigger https://www.diyaudio.com/community/threads/bulging-capacitors-on-qsc-mx1500.367169/post-6513907

Thank you for helping a beginner!

I did a search but didn't find the answer to these questions...
Is it OK to stack identical 10VA toroids to save space?
And can the radiated magnetic flux be reduced by wiring them out of phase...and is it safe to do so? Or will it negatively affect their performance?

Mike

Hi,
request help - I am learning hornresp to design a TL for Tectonic TEBM65C20F-8 driver. My question is although the power level looks flat, the driver position is very close to the vent, it that ok or am I doing something wrong? Please find attached few screenshots from hornresp. Thanks for your help.

After building a set of LM3886 amps based on the Linkwitz circuit (which I really like!), I figured I would try an amp using the LM4780 based on the same circuit layout. Since I haven't used this chip before, I figured I would ask:

1) If anyone has used the Linkwitz circuit ( http://www.linkwitzlab.com/images/graphics/3886amp.gif ) using the LM4780 as two LM3886's. I know other amps (Brian and Peter's come to the front of my mind) use this chip in a similar manner, but I was specifically interested to see if anyone has used the Linkwitz topology. It should be fine, but there is no since in re-inventing the wheel if there is someone who has already found out any issues. (Searching the forum didn’t show much, but I figured someone has to have done this!!!)

And 2) Attached is a proposed PCB that fell together rather nicely, but I figured I would run it past more experienced designers first. Particularly, I am concerned about the V+ section coming from the input pin header to C+ and the input signal traces running along the top right edge of the board. If anyone has any comments either way as to whether my concerns are justified, or if I am in good shape, I would appreciate the feedback. Any suggestions or comments about the rest of the board are welcomed as well!

Thanks!
David


As a side note, I started off trying to make this a single sided PCB. That idea got trashed rather quickly, but I was wondering if anyone has used a single sided LM4780 PCB?

Hi,

I joined this forum because I am trying to restore an old Pioneer car CD player, and am unable to source lasers for a unit that old. I have been working on it off and on for a couple years, and have all portions working except the CD portion of the unit. I would like to find a way to insert audio from a bluetooth device and try to have the CD portion work close to original capacity (I don't expect full functionality). I found a post on here where some users talk about using a similar chipset to what I have and am looking for information on how to accomplish this restoration. I have collected as much manuals and datasheets on the cd player, mechanisms, and chips as I believe is available at this time.

Here is the forum post I found: https://www.diyaudio.com/community/threads/cxd1125q-and-cxd1135q-spdif-output-mod.317359/
It doesn't mention doing what I am wanting to do, just that some other people have a better idea of how these old cd players work.

Is there a section on here that would be appropriate to start a build thread on this project? Are there also some other posts I should read before starting such a project?

Hope to learn from your expertise!

Looking for single, used , very good testing new production WE300B tube. One of the matched pair I have lost the vacuum and became a collectible display ...

It doesn't have to be pretty since the orphan I have is not pretty either, but it has to work. I'm in US but have family in EU so if you are not keen on sending abroad that's alright. I know Brits are already convinced that stuff is being delivered by teleportation and any other method is going to destroy their valuable possessions and it's best that perspective buyer will show up with cash and flowers and chocolate for thier spouses but that's not happening ,sorry🙂

Hi guys

I'm not sure about magnetic parts... like screws, washers, standoffs etc.
are they to be avoided in the circumference of components 'n circuits (like, fasten rectifiers, Mos-/J-fets etc., or even PCBs)?

many thanks!