i expect some music to hear

Guys, anyone had white noise issues with this board? I use the same board as in this vid, but when the volume is 50% to 100% the output gets white noise proportionally increasing with the volume control. Shorting the inputs does nothing. Power is a transformer with 2 separate windings 15V. Tried to change the opamp - no results, still that noise.

You have inspired me to get out of retirement and get back to my projects that I have left behind 20 years. I love how you work a step at a time. It's easy to absorb. I'm an electrical engineer and what you have shown has taught me more than the theory I've had crammed down my throat. My nickname for you is JTSpice because your approach is much better than the LTSpice techs I've seen. Please take care of yourself. You have left us with many homework assignments to work on.

Hello and thank you. You can clearly hear the difference between the 2 speakers despite the limitations of the internet. I prefer the new one, very clearly.

John I want to say thank you for making this video and the amplifier pop on sounds video you made convinced me to get the TDA7498e. I found it normally around 10USD, but with some deal hunting and waiting I got it down to about 5USD making it my cheapest amplifier purchase to date. Currently testing it with a 19V 45w laptop charger with great results and its way better than any of my other Class D amp boards. It has some slight differences to the one you have. Biggest one is that it has a green PCB. Other differences include a different style screw terminal that's smaller, pin header gain control instead of switches, no included nylon standoffs, and reversed RCA inputs (Red on Left and White on Right). The reversed color RCA inputs tripped me up, but its ok since just a simple cable swap fixes that. Its pretty quiet with no audio playing, no pop sounds on power on, and best of all it doesn't have the auto mute after being silent for a while that a lot of TPA3116 boards have that can make the first second or two after playing something again to be only silence which I find particularly annoying especially for video. Thanks again.

Very nice. It would be cool to mention the reason that the amp gain ends up being close to the ratio of emitter and collector resistors. Also, maybe worth mentioning that the emitter resistor can be bypassed to hack the gain.

This is great. I wish you had done it with a simulator so we could actually see it working though... I guess that is an exercise left for the viewers. :)

Anyone know the song name used here: 3:35 thanks!

Elliott has a power supply PCG for this pre-amp: P05 Revision D (It's samller than the pre-amp PCB) Thanks for thr video. Waiting for the final configuration.

Hi, John. Just found your channel this morning. Nice video, subscribed. I've been in pro audio since 1977. Engineering for live sound, recording, servicing, custom design and construction. Now I'm an old fart, and I service vintage HiFi gear. Peavey was always a budget brand, but in the late 1970's and early 80's they did try to improve their better gear and their image. The venerable CS800 and CS400 amps were outstandingly reliable, and were affordable as well. But by the time the late 80's came around, although they were building more and more impressive products, certain economies were allowed to creep into their designs in order to meet desired price points, and the problems you describe with the output stage design is typical of this. This amp should have had twice as many output transistors, and should have not relied so heavily on the fan to keep it cool. And yes, ideally, the output transistors should have been socketed. Audio pros did not "respect" Peavey for the simple reason that it was inexpensive. Americans are raised to believe that expensive equals better - though that is not always true.

I bought one of these from amazon based on these youtube reviews. Didnt work right out of the box. Garbage, don't waste your time.

The volume pot seems to be a linear one, if we consider John's comments of it increasing volume rapidly just in the last rotation third. A log pot should be better. Pity the PS is just 48v/5A instead of 48v/10A. What is the measurement system John is using?

Rod´s projects are simple and the best circuits.

John is the 120va transformer enough for 60w rms output. I'm using an alluminium transformer

Hi can i use this on a branded bluetooth speaker which its board died and run the speakers directly from it ? Thanks

I foundmymanx on a bridge four years ago i am a lucky person i love hervheaps

Could you offer any advice for an output transformer for 2 12k5 12v low voltage tubes in push pull? I also use 12u7 tubes for preamp and phase splitter.

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thank you for this great content! I've learned so much! Your Preamp Sounds Fantastic! Do you mind if I use it and put an OPA2134 at the output with Unity Gain? I Love way it sounds as-is.

Nice grass, John. You should diversify into lawn care tips. 😊. The amp discussion is great, too.

👍👍👍👍👍

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John, I would be glad to share my KiCad files. However, YT will not let viewers post links (or even talk about them,) unless the channel's author grants the viewer some sort of "trusted viewer status." If you can arrange that, I'll set up the link. Let me know what you would like for me to do. Thanks.

Hi, John. Please tell me what type of capacitor you actually used for the 47pF input cap, across the LM386's two input pins, pins 2 and 3. I watched the video, again, to catch this detail. I thought that you had commented on it, but, if so, I did not catch it, this time. Around 14+ minutes, there is a quick glimpse of the component. It sort of looks like a yellow ceramic, but I am just not sure. Teachable Moment = In addition to telling me what you actually used, please comment on what would be the best type of cap to use for this application and why so. Also, what might be substituted, in a pinch... Such as, maybe what appears to be a common ceramic is actually a Tantalum? This is very much the audio signal, so I was expecting some type of a film cap. I checked at Mouser on 47pF film caps and they only seem to be available in really high voltages. I have a nice 47pF/1KVDC-250VAC/Polypropylene/AC and Pulse Film cap on hand. And, I that you taught me that, if the cap voltage rating greatly exceeds the signals voltage, the cap will not form up correctly and the rated capacitance will not be achieved? Thanks, again... I have learned so much from you!

I try to thermally shock the semiconductors to see if I can force a permanent failure with freeze spray and the tip of a soldering iron.

I've had stuff like that where I carefully reassembled the unit while I was running audio through it to find a problem. Or you could just reflow all your soldering connections.

After four years, this is still one of my favorite projects! I have just reworked the board files and ordered another round of boards. Thank you, John, for having shared this great little circuit!

Great review. I appreciate how you are being as objective as possible with what you were given. You got a new sub. Thanks for taking the time to bring this to us.

I have the same power supply.

Maybe the problem wasn´t with the board to begin with, but with the wiring: you have the relatively long high-impedance input wires close to the output wires. That can cause enough coupling for the amplifier to start oscillating at a high (supersonic) frequencies, which may not be immediately evident until you connect an oscilloscope to the outputs. In fact, the amplifier may now still be oscillating even though it seems fixed. If that is the case, using shielded wires may improve things.

That's how I fix things!

I've had this puzzling intermittent problem with an HF transmitter PA stage. Turned out to be dry soldered joints.

Hey sometime ago you said you would do a video on how to make these acrylic boxes. But it's still not out yet. Are you still planning to make that video?

Sounds like a voltage controlled oscillator on a modular synthesizer. Maybe the wiring was capacitavely coupling with something, and the wire moved when you took the amp out of the box?

This is one of those times when cold spray and a heat gun is utilized find intermittent problems.

I had a case where while tracing the problem on the board there was a resistance between two traces. There was no components or problem with the multimeter. The board was also universal like they sell it on the internet. Tested another board in the same spot, but no problems. So I think that maybe the board is bad or condensation from over time made some component to go crazy.

Damn Gremlins! Another good one John.

I think it just doesn't like you... I'd take it personal.

Where it works when you take it out of the box……….but when you put it back in three times later……

Fun video

You reformed the caps. By using it for a while.

Your amplifier was probably just pissed off that you threw it in the junk box for five years...

I met the guy that made Sound Senders once. He was working out of a warehouse next to where a friend of mine worked. So that's how I was introduced to him. My buddy knew him and wanted me to meet this interesting fellow he knew. He was quite a card.

I think it's the perf board. I built a reverse RIAA circuit for testing phono stages on perf board using surface mount components. It worked fine the first day or two then it stopped working after that. I suspect the perf board was too thin and flexible to be reliable

Technically speaking, it had a fart stuck crossways.

Oh, i had something like that: i altered a circuit assamled the device doesn't work, disassemle works - wtf. okay while powered on slowly close the case to see why it is doing that - nothing. Still works, never figured out what was the fault.

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You've got the magic touch!

I would think that screwing down the board presses a bridge link against another contact.