Thanks for the vid Michael. I've been looking for a good solution to replace pots in vintage gear and this looks like it would work. I think the 1.5MHz oscillation may be induced from external but who knows without thorough testing. Things I don't like - the free wheeling rotary encoder doesn't have feedback as how the volume is set. On power up, does it remember it's last setting or does it default to a preset volume? I think I may pick one of these up for further testing. Thanks again!
well there is a great little project where the encoder is connected with a BLDC motor and there are "limitless" options on how to configure it. :) I never saw it in real life but a great little piece I must say: ruclips.net/video/ip641WmY4pA/видео.html
A device like this should have a clip indicator of some sort. But after seeing the test you did? I have to wonder if many people would just regard it as a tube micro phonics or something of that sort of banter about the device you tested in their signal chain. Who knows.? I'm wondering if they the same sort of chip set in some of the android head units on the market? Its long overdue I get my self an O scope of high caliber and start doing my own testing. And some proper test gear. Thanks again for the wonderful insightful video Mr Beeny!
Just a thought: If there's an opamp in there - it's probably inadequate supply decoupling. The right caps need to be placed right on the IC pins to a very local 0VDC. A small cap (15pF) across NFB might also get it under control - or not! All the best, Beamer.
12:05 He says "no gain". Doesn't that mean no OpAmp? I do see 4:16 one 8 legged IC right in the center of the board though. Hmmm...... It's curious. Now I want to see a relay volume control analyzed. 🔈🔉🔊
Nice video thanks for sharing. For e-commerce/commercial digital volume control, sometimes it is not optimized for DIYer's like the Rotary encoder in your video not sure if the dB/ step attenuation is 1 dB/ 0.5 dB , it should have been nice to have option on selecting attenuation like 2~4 dB/step or re-program it If you love DIY, the best is to make your own DIY digital volume control, cheers everyone!
On my 35-years old receiver driving a pair of 35-year old B&W bookshelf speaker, the potentiometer developed a bad contact, although all the electrolytic capacitors are OK. That is the reason why no one wants to use a potentiometer any more. Any way at first, I mistakenly thought the tweeter of the 35-year old B&W went bad, because the symptom of bad-contact potentiometer appeared only in the tweeter frequencies. A few months ago, you mentioned a bad contact of a stock 32 volt power supply gave you a hiss noise from your TPA 3255. I myself have two TPA3255-based amps with the well-known volume chip from Japan. Remote volume control is another important benefit. Rather similarly, I too realized the fact that the bad-contact in an old potentiometer yields a high-frequency noise mostly in the tweeter especially when the sound-desibel rises. Have a nice day. PS: I am not able to replace the potentiometer, because all other front-panel control knobs are attached to the board so tightly together. So, I am going to throw away the receiver soon. Interestingly, when I use an external DAC with a volume control, I can now set the potentiometer at high volume levels which I have never used for so many years. Then, the receiver works perfectly OK at that potentiometer setting.
Overshooting / ringing indicates a non-flat response in the very high frequency range - I would try that sweep test again but this time go way up to 300-400Khz. The ringing looks like its occurring at a very high frequency. The other thing is, you will never have a 20Khz square wave in your audio signal -20Khz square wave will contain harmonics extending into the many hundreds of Khz Whereas at audio the maximum frequency will be a 22Khz sine. I think it will be fine in reality but at the most it may need a tiny value capacitor (pF) across a negative feedback loop - assuming there's some op amps in there somewhere. Good channel thanks (I am in NZ and also build amps)
A couple of things: 1) The THD % is nor great at low signal levels 2) The 8 pin SOP chip on the knob board determine how the knob turns relate to volume. I could be relatively easy to replace/reprogram it, but like you, I have health issues, so past easy stuff is out of reach for me now. Just for your info, although you likely already know from the data sheet, that SOP-8 converts the knob turns into I2C command for the PT2259.
Hi Steven, It's been a while since I last played with this module. The biggest issue I found was its quite low input level overload. Also the fact it has no gain only attenuation, means you need a preamp stage after it. The balance between the input and output is quite difficult to get right without more circuity. Preferably a buffer on the input and a preamp on the output. It's in the bin of other poor and not working to well stuff. Sorry to hear you also have poor health. I know exactly how you feel. I hate not being well, it's a bit of a wide band attenuator. lol
Ears are not that sensitive to level changes. Even a balance control, when in the centre position can be out by a couple of dB. The least amount of extra bits added is better.
Mr Beeny, does it matter it won't pass a square wave?? I don't listen to square waves.. Do you?? Even most high quality opamps don't pass a hf square wave perfectly???
It matters a lot. If the square wave is not SQUARE it tells you a great deal about the speed or rise time of the chip. That translates into fast attack and wide dynamics. An amplifier with a good square wave tends to sound better than one with a poor looking wave. No, I don't listen to square waves but look at the wave form of music, no nice smooth sine waves, all peaks, fast rise times. Spikes etc So really a square wave does make sense until someone comes up with a better tool.
@@MichaelBeeny Isn't speed and rise time only applicable if they are inadequate inside the audio bandwidth? If an opamp can't properly slew a 10V 100Khz signal but does fine 20 to 20Khz, isn't that good enough?
@@brannonmcevers1854 I'm still going to do some more tests on these, I will be in the lounge listening in the next few days to see if it adds noise or colour and what it's like to use it in the real world.
Hello Michael First, thank you for your many good videos, especially the ones about amplifiers I always watch. But also, I don't like your endings! Your name and a date make me think you died that day, but luckily you didn't. Perhaps a picture of your rabit and a Copyright Michael Beeny, New Zealand and the date would be better. And now after all the fatter; Have you tried the "DAC T Type SMD Stepped Attenuator 21 step volume control 50k Potentiometer HIFI", which are on e.g. eBay for 16.5 US$? I have just ordered one to try if it lasts better than the Alps that's in my PC amplifier, but it keeps falling out in one channel (this happens for both channels). The step potentiometer has gold plated contacts, maybe that's better? But there are only 20 volume levels, is that enough? Greetings Michael, from Denmark, EU
Like most things these days, I'm not sure all Alps pots are real, as the price varies considerably. I've been quite lucky so far with no issues. Saying that, I find even the very small green ones can be very good with a nice feel to them. I've often looked at switched pots with interest. Looking at reviews from customers, they get mixed reviews. Some people love them others talk of wrong value resistors, poor switches. I'm not a lover of switched pots myself. The first step can be off putting, depends on if the really follow a log law. As to how many steps?? The more the better, I guess. In fact, a completly variable rotation is best!! A NORMAL pot. Do you know, no one has EVER made any comments ever about my video skills (or lack of) The opening titles often take longer to make than editing the complete video. I never know how to end it either. That's how I ended up with what I have. I was originally going to put the little copyright squiggle but not available in my list of characters, hence it ended up with my name and date. I even got thar wrong a few weeks ago! Very few people watch to the END anyway! As to being dead, I often wake up and find I'm surprised I'm not yet dead. Maybe some others will come up with a good idea? Thanks for writing, let us know what you think when the pot arrives.
@@MichaelBeeny I got the pot this Friday, I even got two pots for the price of one! I haven’t mounted the pot yet, but the feeling is good, and I will say very good. 20 small clicks, I can feel them, no sound, and no additional force is used. It rotates freely, but I feel the clicks. I gave the stereo pots 9 Volts at the two 50K lanes and measured the difference between the two outtakes. It was practical zero milli volts at all levels, so det balance must be very good. I will write when I have mounted the one pot I ordered.
Dear Michael, try this please WONDOM AA-AB41148 I use it with my TPA 3255 the same that you have. The potentiometer that I recommend , is "from other planet" comparing with this that you tested
Further to my reply of last year. I am considering getting one of these to test and hopefully use. Anything further you can add will be most appreciated. Mike
Thanks for the vid Michael. I've been looking for a good solution to replace pots in vintage gear and this looks like it would work. I think the 1.5MHz oscillation may be induced from external but who knows without thorough testing.
Things I don't like - the free wheeling rotary encoder doesn't have feedback as how the volume is set. On power up, does it remember it's last setting or does it default to a preset volume?
I think I may pick one of these up for further testing. Thanks again!
well there is a great little project where the encoder is connected with a BLDC motor and there are "limitless" options on how to configure it. :) I never saw it in real life but a great little piece I must say:
ruclips.net/video/ip641WmY4pA/видео.html
I will do more tests soon to answer all the question I have received on this.
A device like this should have a clip indicator of some sort. But after seeing the test you did?
I have to wonder if many people would just regard it as a tube micro phonics or something of that sort of banter about the device you tested in their signal chain. Who knows.?
I'm wondering if they the same sort of chip set in some of the android head units on the market?
Its long overdue I get my self an O scope of high caliber and start doing my own testing. And some proper test gear.
Thanks again for the wonderful insightful video Mr Beeny!
Just a thought: If there's an opamp in there - it's probably inadequate supply decoupling. The right caps need to be placed right on the IC pins to a very local 0VDC. A small cap (15pF) across NFB might also get it under control - or not! All the best, Beamer.
12:05 He says "no gain". Doesn't that mean no OpAmp? I do see 4:16 one 8 legged IC right in the center of the board though. Hmmm...... It's curious.
Now I want to see a relay volume control analyzed. 🔈🔉🔊
Nice video thanks for sharing. For e-commerce/commercial digital volume control, sometimes it is not optimized for DIYer's like the Rotary encoder in your video not sure if the dB/ step attenuation is 1 dB/ 0.5 dB , it should have been nice to have option on selecting attenuation like 2~4 dB/step or re-program it If you love DIY, the best is to make your own DIY digital volume control, cheers everyone!
On my 35-years old receiver driving a pair of 35-year old B&W bookshelf speaker, the potentiometer developed a bad contact, although all the electrolytic capacitors are OK.
That is the reason why no one wants to use a potentiometer any more.
Any way at first, I mistakenly thought the tweeter of the 35-year old B&W went bad, because the symptom of bad-contact potentiometer appeared only in the tweeter frequencies.
A few months ago, you mentioned a bad contact of a stock 32 volt power supply gave you a hiss noise from your TPA 3255. I myself have two TPA3255-based amps with
the well-known volume chip from Japan. Remote volume control is another important benefit.
Rather similarly, I too realized the fact that the bad-contact in an old potentiometer yields a high-frequency noise mostly in the tweeter especially when the sound-desibel rises.
Have a nice day.
PS: I am not able to replace the potentiometer, because all other front-panel control knobs are
attached to the board so tightly together. So, I am going to throw away the receiver soon.
Interestingly, when I use an external DAC with a volume control, I can now set the potentiometer at high volume levels which I have never used
for so many years. Then, the receiver works perfectly OK at that potentiometer setting.
Overshooting / ringing indicates a non-flat response in the very high frequency range - I would try that sweep test again but this time go way up to 300-400Khz. The ringing looks like its occurring at a very high frequency. The other thing is, you will never have a 20Khz square wave in your audio signal -20Khz square wave will contain harmonics extending into the many hundreds of Khz Whereas at audio the maximum frequency will be a 22Khz sine. I think it will be fine in reality but at the most it may need a tiny value capacitor (pF) across a negative feedback loop - assuming there's some op amps in there somewhere. Good channel thanks (I am in NZ and also build amps)
A couple of things: 1) The THD % is nor great at low signal levels 2) The 8 pin SOP chip on the knob board determine how the knob turns relate to volume.
I could be relatively easy to replace/reprogram it, but like you, I have health issues, so past easy stuff is out of reach for me now.
Just for your info, although you likely already know from the data sheet, that SOP-8 converts the knob turns into I2C command for the PT2259.
good vid, hope your well
Hi Steven,
It's been a while since I last played with this module. The biggest issue I found was its quite low input level overload. Also the fact it has no gain only attenuation, means you need a preamp stage after it. The balance between the input and output is quite difficult to get right without more circuity. Preferably a buffer on the input and a preamp on the output. It's in the bin of other poor and not working to well stuff.
Sorry to hear you also have poor health. I know exactly how you feel. I hate not being well, it's a bit of a wide band attenuator. lol
Thanks again for the information. 😊😊😊🎉🎉🎉 par the rabbit.❤❤❤
i think i will stick to rotary pots maybe duel concetric or even add a ballance control
Ears are not that sensitive to level changes. Even a balance control, when in the centre position can be out by a couple of dB. The least amount of extra bits added is better.
I use stepped attenuator with hand matched resistors
Did you try the square vawe oscillation with some kind of fake resistive and/or inductive load?
The load was just a 4.7K standard resistor, with the scope connected across it.
Mr Beeny, does it matter it won't pass a square wave?? I don't listen to square waves.. Do you??
Even most high quality opamps don't pass a hf square wave perfectly???
It matters a lot. If the square wave is not SQUARE it tells you a great deal about the speed or rise time of the chip. That translates into fast attack and wide dynamics. An amplifier with a good square wave tends to sound better than one with a poor looking wave. No, I don't listen to square waves but look at the wave form of music, no nice smooth sine waves, all peaks, fast rise times. Spikes etc So really a square wave does make sense until someone comes up with a better tool.
@@MichaelBeeny Isn't speed and rise time only applicable if they are inadequate inside the audio bandwidth? If an opamp can't properly slew a 10V 100Khz signal but does fine 20 to 20Khz, isn't that good enough?
@@MichaelBeeny Also, thank you for the reply
@@brannonmcevers1854 I'm still going to do some more tests on these, I will be in the lounge listening in the next few days to see if it adds noise or colour and what it's like to use it in the real world.
@@MichaelBeeny Happy listening!
Hello Michael
First, thank you for your many good videos, especially the ones about amplifiers I always watch.
But also, I don't like your endings! Your name and a date make me think you died that day, but luckily you didn't.
Perhaps a picture of your rabit and a Copyright Michael Beeny, New Zealand and the date would be better.
And now after all the fatter;
Have you tried the "DAC T Type SMD Stepped Attenuator 21 step volume control 50k Potentiometer HIFI", which are on e.g. eBay for 16.5 US$?
I have just ordered one to try if it lasts better than the Alps that's in my PC amplifier, but it keeps falling out in one channel (this happens for both channels).
The step potentiometer has gold plated contacts, maybe that's better? But there are only 20 volume levels, is that enough?
Greetings Michael, from Denmark, EU
Like most things these days, I'm not sure all Alps pots are real, as the price varies considerably. I've been quite lucky so far with no issues. Saying that, I find even the very small green ones can be very good with a nice feel to them.
I've often looked at switched pots with interest. Looking at reviews from customers, they get mixed reviews. Some people love them others talk of wrong value resistors, poor switches. I'm not a lover of switched pots myself. The first step can be off putting, depends on if the really follow a log law. As to how many steps?? The more the better, I guess. In fact, a completly variable rotation is best!! A NORMAL pot.
Do you know, no one has EVER made any comments ever about my video skills (or lack of) The opening titles often take longer to make than editing the complete video. I never know how to end it either. That's how I ended up with what I have. I was originally going to put the little copyright squiggle but not available in my list of characters, hence it ended up with my name and date. I even got thar wrong a few weeks ago! Very few people watch to the END anyway! As to being dead, I often wake up and find I'm surprised I'm not yet dead. Maybe some others will come up with a good idea?
Thanks for writing, let us know what you think when the pot arrives.
@@MichaelBeeny I got the pot this Friday, I even got two pots for the price of one!
I haven’t mounted the pot yet, but the feeling is good, and I will say very good. 20 small clicks, I can feel them, no sound, and no additional force is used. It rotates freely, but I feel the clicks.
I gave the stereo pots 9 Volts at the two 50K lanes and measured the difference between the two outtakes. It was practical zero milli volts at all levels, so det balance must be very good.
I will write when I have mounted the one pot I ordered.
@@michaellundsrensen2292 Sounds good Michael, I look forward to the final results.
Next... One with a remote control
If I win the lottery. I've already got a remote control, it's called my wife lol
maybe it's your probes sre ringing.
My ears were ringing yesterday after high level testing for a number of hours. I think my probes are OK however.
chines design is always bad bad bad, sure bad😂
Dear Michael, try this please
WONDOM AA-AB41148
I use it with my TPA 3255 the same that you have.
The potentiometer that I recommend , is "from other planet" comparing with this that you tested
Does look good but a lot of circuitry just to change the volume. I think I will stick with a conventional volume pot.
Further to my reply of last year. I am considering getting one of these to test and hopefully use. Anything further you can add will be most appreciated.
Mike