i have a feeling people who are into modular synths music would get a pleasant kick out of this video, the visualization was quite nice. thanks for sharing
The ear is very sensitive to phase ..it’s how we locate the position of sound in the environment. Over the years I have concluded that the amps with the least phase shift across the audio frequency band have the best sound stage . It’s one of the few audiophile comments that really is important..Great work .
This is a good way of really comparing two signals for amplitude and phase difference! I am just now doing service on a receiver's audio section, and finding the dual control pots (among other components in the audio path) to not match as good as I would like to.. One channel is 2-3dB down compared to the other..
Thank you very much for the new upgraded video tech. The picture-in-picture worked great. Also, I stopped wearing my smart watch on the bench after I chased my tail for HOURS trying to find the source of interference :D
I just used my Windows PC with the NAK-100 software app for checking out a Pioneer SA-9800 II integrated amplifier preamp section. Normally this is used for checking out tape decks, but I found the different waveform generators handy including pink, and white noise which is displayed on a frequency spectrum plot. The left channel in the preamp works great, but the right channel is 2.5 db down in gain from the left. When I turn the tone switch to on, then the right channel drops -20 db, wow! Probably those pesky orange coupling caps on the tone board! The problem with using this for this application, is the limitation of the sound card which clips at 1.5 volts RMS input signal. Worked well for seeing the noise floor spectrum at -100 to -110 db however. You could see the noise spikes at 60 and 120 Hz. I was also able to measure THD all the way down to 0.009% which is about it's limit.
I just released my old ALPS volume pot as it didn't track each channel anymore. I bought a TKD CP2-601 to replace. I guess I've got the TKD with biggest mismatch in the lot cause at low level the left side is much louder. This project would be an easy build to see the results. A DMM would tell the same story at different voltages or tracking each channel on the scope, but where's the fun in that😊 -Thanks for sharing this project Tony👍
Note to new players --- the right side of Tony's breadboard is ⚡😲⚡! 😂I love how building up a power supply on the breadboard is nothing serious for you, I am sure the voltages you deal with professionally are an order(s) of magnitude greater. I built my first power supply from a Jameco kit early in my hobby. I was so terrified of testing it that I took it out to the garage and set up a switch ten feet away from it! 😆
Unless you are listening with headphones, your ears are going to be a different distance from left and right speakers anyway, so you will have a difference to your ears regardless of whether or not the two channels are perfectly aligned. That is the nuance of sound and what makes it great. Perfection in music sucks IMO. We might as well be computers receiving digital data.
Excellent. I love small, DIY, EE, Bench Tool Projects. Please sir, may we have some more? I vote yes, for part 2, please. As for the Diff Amp Circuit, would it be an improvement to move the amplitude attenuation from the output, U2B, all the way back to the inputs, J2 and J3. My thinking is based on audio mixing strategy... If the upstream amplification is attenuated, it can be over-driven by any prior downstream amplification. You know this well, of course. If placing the attenuation pot at the first of the input is not better, please explain why. Yes, the trimmers could be used for this purpose. A stereo pot might be easier to use, for amplitude attenuation, not nullification. Now that I see the nullification process, I guess the trimmers do this function. A question for everybody = Isn't the TL072/4 older technology? What might be a better modern op amp, for this purpose? Thanks.
That’s fantastic! could we integrate this with a Laser Doppler Velocimetry (LDV) system to monitor and compare the mechanical movement of the speaker’s voice coil against the signal at the input terminals? this would (probably) allow us to generate an error correction signal to adjust and optimize the (speaker’s) output?
Can you measure the total harmonic distortion (THD) of this Sansui CA-2000 preamp after having re-capped and repaired it? Is it better, worse or the same as new condition? and also the output impedance of the preamp?
I was matching transistors last evening. Case is I need some quite equally matching between NPN/PNP, not always that easy. It got me thinking if this simple device could be a way to spot differences between BJT devices in test?
Nah that belief system can be very entrenched and some will deny any proof. Not all but a majority that have already invested way too much money in products that do NOTHING.
:):) excellent input. sometimes i watch 'their' videos as entertainment, is it wrong of me? if you guys think you're ready (you're not), i can post a youtube link w/ something truly spectacular. i watched these guys in germany measuring the voltage between the rca connectors (ground side) of a receiver and a cd player in an attempt to demonstrate "coupling between the primary and secondary of the transformers", the cd player wasn't grounded... it still makes me smile thinking about it. (among other things they produce/sell "air insulated" cables, yes that's right)
@@davidlong1786 but did you know they have 'directional audio cables'? :) these folks are amazingly funny, i need to find a video quick, to me it's like standup comedy.. own private version of physics, theory, everything..
Just a question, shouldnt the offset null adjustment have series resistors on each input to allow it to work more as a potential divider? Otherwise if the inout source is low impedence, you will just be applying more or less load to the input without actually altering the amplitude (I would have thought) OK I kept watching :-)
I was thinking of white or pink noise myself, but wouldn't it be difficult to have two independent random generators in phase? Would have to be a single mono generator, but not sure if it could be done another way.
You folks are getting ahead of me! I still have to assemble the pink noise generator board. It might show up in the next part, if I have time to finish it.
To protect from DC offset and to limit the max current into the 50k load of the input pot. The cap value was chosen to allow full bandwidth at the signal levels that I will be applying to the input.
I had some TL084's in stock, but when using the proto board, it was easier to space the two TL072's out for component placement. I'm not that good at laying out those proto boards. Some folks are artists at doing that :) but not me :(
i have a feeling people who are into modular synths music would get a pleasant kick out of this video, the visualization was quite nice.
thanks for sharing
Love the fact that it goes to 11 !
Did you notice the numbering on the three knobs ;)
The ear is very sensitive to phase ..it’s how we locate the position of sound in the environment. Over the years I have concluded that the amps with the least phase shift across the audio frequency band have the best sound stage . It’s one of the few audiophile comments that really is important..Great work .
This is a good way of really comparing two signals for amplitude and phase difference! I am just now doing service on a receiver's audio section, and finding the dual control pots (among other components in the audio path) to not match as good as I would like to.. One channel is 2-3dB down compared to the other..
Thank you very much for the new upgraded video tech. The picture-in-picture worked great. Also, I stopped wearing my smart watch on the bench after I chased my tail for HOURS trying to find the source of interference :D
Second part please! I really appreciate your process and the way you think of things! Nothing beats measurable data! Thanks Tony!
I just used my Windows PC with the NAK-100 software app for checking out a Pioneer SA-9800 II integrated amplifier preamp section.
Normally this is used for checking out tape decks, but I found the different waveform generators handy including pink, and white noise which is displayed on a frequency spectrum plot. The left channel in the preamp works great, but the right channel is 2.5 db down in gain from the left. When I turn the tone switch to on, then the right channel drops -20 db, wow! Probably those pesky orange coupling caps on the tone board!
The problem with using this for this application, is the limitation of the sound card which clips at 1.5 volts RMS input signal. Worked well for seeing the noise floor spectrum at -100 to -110 db however. You could see the noise spikes at 60 and 120 Hz. I was also able to measure THD all the way down to 0.009% which is about it's limit.
I just released my old ALPS volume pot as it didn't track each channel anymore. I bought a TKD CP2-601 to replace. I guess I've got the TKD with biggest mismatch in the lot cause at low level the left side is much louder. This project would be an easy build to see the results. A DMM would tell the same story at different voltages or tracking each channel on the scope, but where's the fun in that😊
-Thanks for sharing this project Tony👍
Great video as always Tony. Look forward to see how you use this in future restorations.
Note to new players --- the right side of Tony's breadboard is ⚡😲⚡! 😂I love how building up a power supply on the breadboard is nothing serious for you, I am sure the voltages you deal with professionally are an order(s) of magnitude greater. I built my first power supply from a Jameco kit early in my hobby. I was so terrified of testing it that I took it out to the garage and set up a switch ten feet away from it! 😆
Great idea Tony. This be used to check center accuracy of a balance control.
Unless you are listening with headphones, your ears are going to be a different distance from left and right speakers anyway, so you will have a difference to your ears regardless of whether or not the two channels are perfectly aligned. That is the nuance of sound and what makes it great. Perfection in music sucks IMO. We might as well be computers receiving digital data.
Tony I love your informative videos. You can compare it to the second preamp if you wish. I love everything you do. Thank you.
Excellent. I love small, DIY, EE, Bench Tool Projects. Please sir, may we have some more? I vote yes, for part 2, please. As for the Diff Amp Circuit, would it be an improvement to move the amplitude attenuation from the output, U2B, all the way back to the inputs, J2 and J3. My thinking is based on audio mixing strategy... If the upstream amplification is attenuated, it can be over-driven by any prior downstream amplification. You know this well, of course. If placing the attenuation pot at the first of the input is not better, please explain why. Yes, the trimmers could be used for this purpose. A stereo pot might be easier to use, for amplitude attenuation, not nullification. Now that I see the nullification process, I guess the trimmers do this function. A question for everybody = Isn't the TL072/4 older technology? What might be a better modern op amp, for this purpose? Thanks.
Yep like a OPA1656.
I agree. More diy test equipment! Can never have too much of that
yes,please compare the preamps.
That’s fantastic! could we integrate this with a Laser Doppler Velocimetry (LDV) system to monitor and compare the mechanical movement of the speaker’s voice coil against the signal at the input terminals? this would (probably) allow us to generate an error correction signal to adjust and optimize the (speaker’s) output?
Thats what I do at home.
Can't wait for part 2!!
Excellent !
Great video !....cheers.
came out great anyway
Mr Don, your restorations are beautiful. How do you paint the chassis and make it look like you removed the tube sockets?
could you use some comparitor IC's and LED's to make a 'nulling indicator' ?
Thats a good idea make it more compact :)
Can you measure the total harmonic distortion (THD) of this Sansui CA-2000 preamp after having re-capped and repaired it? Is it better, worse or the same as new condition? and also the output impedance of the preamp?
As always instructive and informative. Would love gerber file to help with pcb to make my own differential amplifier :-)
I was matching transistors last evening. Case is I need some quite equally matching between NPN/PNP, not always that easy. It got me thinking if this simple device could be a way to spot differences between BJT devices in test?
You'd be better off using a curve tracer for that.
You could make some people who believe in cable sonics very upset with that device :P
Nah that belief system can be very entrenched and some will deny any proof. Not all but a majority that have already invested way too much money in products that do NOTHING.
:):) excellent input.
sometimes i watch 'their' videos as entertainment, is it wrong of me?
if you guys think you're ready (you're not), i can post a youtube link w/ something truly spectacular.
i watched these guys in germany measuring the voltage between the rca connectors (ground side) of a receiver and a cd player in an attempt to demonstrate "coupling between the primary and secondary of the transformers", the cd player wasn't grounded... it still makes me smile thinking about it.
(among other things they produce/sell "air insulated" cables, yes that's right)
@@davidlong1786 but did you know they have 'directional audio cables'? :)
these folks are amazingly funny, i need to find a video quick, to me it's like standup comedy.. own private version of physics, theory, everything..
@@davidlong1786 Bravo Sir !
If you redid the resistors in the tone control circuit with 1% metal film ones that difference would be even smaller.
Just a question, shouldnt the offset null adjustment have series resistors on each input to allow it to work more as a potential divider? Otherwise if the inout source is low impedence, you will just be applying more or less load to the input without actually altering the amplitude (I would have thought) OK I kept watching :-)
Would it be useful to feed white noise into the pre-amp and compare the differences between channels or comparison between input and output ?
I was thinking of white or pink noise myself, but wouldn't it be difficult to have two independent random generators in phase? Would have to be a single mono generator, but not sure if it could be done another way.
You folks are getting ahead of me! I still have to assemble the pink noise generator board. It might show up in the next part, if I have time to finish it.
If you're creating a difference signal, those input capacitors will affect lower frequencies. Why not direct-couple the inputs?
To protect from DC offset and to limit the max current into the 50k load of the input pot. The cap value was chosen to allow full bandwidth at the signal levels that I will be applying to the input.
couldn't you have used a TL074 instead of 2 TL072 op amps?
Maby TL072 were in his stock😉 Same here... But a single TL074 should do
I had some TL084's in stock, but when using the proto board, it was easier to space the two TL072's out for component placement. I'm not that good at laying out those proto boards. Some folks are artists at doing that :) but not me :(
@@xraytonyb I have run into that same situation myself and did the same thing for that same reason
You did not try to zero after applying tone change, to see if we are dealing with amplitude or phase difference. Pretty st id.
I did. I'm pretty sure I showed it in the video. I also don't think it's very helpful to end your comment that way.
Pretty standard idea?
Good one! Would be interested in seeing the comparison done between the two amps.