Hello,
There are several pot threads, but I could not find answer to my question.
I have used quite a few potentiometer. First, about 15 years ago I build a ladder on a rotary switch. For long time I did not realize how good it is. Than I made a preamp with the alsp motorized blue. Was not bad, but replacing with the normal alps black was a significant improvement. Than I tried the old rotary switch and it was a significant improvement. Like a curtain got opened. I have tried R-2R with different relays with no success. Now, I am back to the rotary switch, but the preamp is 6072 based now, the amp is 2A3 PSE etc.
Now, I want to make a portable usb dac with volume control and Iwant to make it gooood. The best I can make. Can you recommend a small size volume pot? For this, even an alps blue would be big. I have an Amanero combo384 for input, did not decide the dac and than I need a volume pot and a discrete buffer. Or maybe first the buffer, depending on the dac (probably ad1865 after some conversion).
Thanks,
JG
There are several pot threads, but I could not find answer to my question.
I have used quite a few potentiometer. First, about 15 years ago I build a ladder on a rotary switch. For long time I did not realize how good it is. Than I made a preamp with the alsp motorized blue. Was not bad, but replacing with the normal alps black was a significant improvement. Than I tried the old rotary switch and it was a significant improvement. Like a curtain got opened. I have tried R-2R with different relays with no success. Now, I am back to the rotary switch, but the preamp is 6072 based now, the amp is 2A3 PSE etc.
Now, I want to make a portable usb dac with volume control and Iwant to make it gooood. The best I can make. Can you recommend a small size volume pot? For this, even an alps blue would be big. I have an Amanero combo384 for input, did not decide the dac and than I need a volume pot and a discrete buffer. Or maybe first the buffer, depending on the dac (probably ad1865 after some conversion).
Thanks,
JG
Is you DAC capable of properly driving the cable and a 10K vol pot?
If so then you don't need a Buffer at the DAC.
a 10K dual track vol pot in small sizes is available.
But it is a wiper on a conductive track and must attract the downsides of that style of vol pot.
If this vol pot is attached to your input with short traces/wires then you don't need a Buffer there either, provided the input impedance suits the max output impedance of the vol pot. 10k has a max output impedance of ~2k5.
Is there a reason for not using the existing sticky Thread for your passive vol pot?
http://www.diyaudio.com/forums/anal...iometer-passive-preamplifier.html#post3157081
If so then you don't need a Buffer at the DAC.
a 10K dual track vol pot in small sizes is available.
But it is a wiper on a conductive track and must attract the downsides of that style of vol pot.
If this vol pot is attached to your input with short traces/wires then you don't need a Buffer there either, provided the input impedance suits the max output impedance of the vol pot. 10k has a max output impedance of ~2k5.
Is there a reason for not using the existing sticky Thread for your passive vol pot?
http://www.diyaudio.com/forums/anal...iometer-passive-preamplifier.html#post3157081
Hello,
"Is there a reason for not using the existing sticky Thread for your passive vol pot?"
Yes, it is a complete different thing.
I do not like passive preamps at all and I do not speak about impedance matching. Either way that has to be correct, it is prerequisite. When I tested pots before, it was a tube riaa before and the preamp after with 6072. This time the pot value can be lower, not 100k, depending on the dac. On the 1856 I need a buffer before too, that is my favourite dac, but needs data conversion also, I might use Es90xx that does not need a buffer before.
Anyway, the question is about the pot itself. I found significant difference between potentiometers in the same circuit. For this, I can not use a rotary sw and need to find out what is the best of the small pots.
Thanks,
JG
"Is there a reason for not using the existing sticky Thread for your passive vol pot?"
Yes, it is a complete different thing.
I do not like passive preamps at all and I do not speak about impedance matching. Either way that has to be correct, it is prerequisite. When I tested pots before, it was a tube riaa before and the preamp after with 6072. This time the pot value can be lower, not 100k, depending on the dac. On the 1856 I need a buffer before too, that is my favourite dac, but needs data conversion also, I might use Es90xx that does not need a buffer before.
Anyway, the question is about the pot itself. I found significant difference between potentiometers in the same circuit. For this, I can not use a rotary sw and need to find out what is the best of the small pots.
Thanks,
JG
Hello,
Least effect on sound. What I found about potentiometers before, it reduced transparency, effected high freqs first. I want to avoid it as much as possible.
I ordered the alps and the bourns listed above, in 50K value and will try in the normal chain first.
Thanks,
JG
In the meantime, the impedance matching got easier. Unfortunately the AD1865 is not an option. I like it using the current output to a resistor at Lundahl transformer primary legs. The transformers will not fit this design either :-(
So, buffer before is not needed probably. I search for what DAC chip, but it is anothr thread.
If you have other suggestion to small potentiometer, let me know please. It would be good to do the test once.
Thanks,
JG
So, buffer before is not needed probably. I search for what DAC chip, but it is anothr thread.
If you have other suggestion to small potentiometer, let me know please. It would be good to do the test once.
Thanks,
JG
If the DAC needs an added Buffer stage, then that Buffer goes in the DAC.
If the vol pot needs a Buffer stage, then that Buffer goes on the output of the vol pot. This added Buffer makes your passive vol pot into an active one.
But why did you order 50k vol pots?
10k has 20% of the output impedance of a 50k and thus tolerates 500% of the parasitic capacitances to reach the same treble cut that you mentioned as previously being one of your problems.
If the vol pot needs a Buffer stage, then that Buffer goes on the output of the vol pot. This added Buffer makes your passive vol pot into an active one.
But why did you order 50k vol pots?
10k has 20% of the output impedance of a 50k and thus tolerates 500% of the parasitic capacitances to reach the same treble cut that you mentioned as previously being one of your problems.
For test. 100k would be the most correct and the current volume control is even more than that. The RIAA can handle 50k, but can not handle 20 or 10k.
I will buy a lower resistance value pot once I find out which one to use. I hope the sound character will be similar in both circuit.
Thanks!
Regards,
JG
The vol pot is two functions.
It acts as a Receiver for the Source.
The Source has to drive the interconnect cable and the Receiver.
This is where the vol pot impedance and the first cable length is important.
The second function is as a Source.
The vol pot Source sends signals to the next Receiver stage.
The output impedance varies a lot depending on the pot rotation. It varies from zero ohms to ~25% of it's track resistance. This higher impedance has to drive the second interconnect and the receiver impedance.
The first when as a Receiver suits a higher vol pot impedance.
The second as a Source suits a lower vol pot impedance.
Then comes the compromise:
option 1. adopt a medium impedance vol pot that works as both Source and Receiver.
option2. adopt a very low impedance vol pot and add a Buffer to the Source that feeds it.
option3. adopt a very high impedance vol pot and add a Buffer to the vol pot output.
option4. fit two Buffers, one to the first Source (or sources if any can't drive the cables) and a second at the vol pot output to drive the output cables and the next stage's input impedance.
It acts as a Receiver for the Source.
The Source has to drive the interconnect cable and the Receiver.
This is where the vol pot impedance and the first cable length is important.
The second function is as a Source.
The vol pot Source sends signals to the next Receiver stage.
The output impedance varies a lot depending on the pot rotation. It varies from zero ohms to ~25% of it's track resistance. This higher impedance has to drive the second interconnect and the receiver impedance.
The first when as a Receiver suits a higher vol pot impedance.
The second as a Source suits a lower vol pot impedance.
Then comes the compromise:
option 1. adopt a medium impedance vol pot that works as both Source and Receiver.
option2. adopt a very low impedance vol pot and add a Buffer to the Source that feeds it.
option3. adopt a very high impedance vol pot and add a Buffer to the vol pot output.
option4. fit two Buffers, one to the first Source (or sources if any can't drive the cables) and a second at the vol pot output to drive the output cables and the next stage's input impedance.
Last edited:
Best Small Size one-deck Stereo-Potentiometer for Volume Control
Stereo potentiometers usually manufactured as two deck (dual unit) version like e. g. this:
RK271 Series - Basic information
But there are sometimes to find single-unit resp. one-deck potentiometers like the WHO172 series under
CHANGZHOU WUJIN SPIKE POTENTIOMETER FACTORY
An good known example is the NAIT (REV.1) - the used potentiometer for volume control looks like the "WHO172-2P6L" from the previous mentioned URL - go to
http://1.bp.blogspot.com/_72VgihSgEs0/TMqxVJIUeRI/AAAAAAAAAJc/AXVK7X5rrCI/s1600/IMG_2739.JPG
I am looking for a high quality version in this kind and with same space requirements.
Who can provide the right advice for such a potentiometer ?
Thank you very much in advance.
Stereo potentiometers usually manufactured as two deck (dual unit) version like e. g. this:
RK271 Series - Basic information
But there are sometimes to find single-unit resp. one-deck potentiometers like the WHO172 series under
CHANGZHOU WUJIN SPIKE POTENTIOMETER FACTORY
An good known example is the NAIT (REV.1) - the used potentiometer for volume control looks like the "WHO172-2P6L" from the previous mentioned URL - go to
http://1.bp.blogspot.com/_72VgihSgEs0/TMqxVJIUeRI/AAAAAAAAAJc/AXVK7X5rrCI/s1600/IMG_2739.JPG
I am looking for a high quality version in this kind and with same space requirements.
Who can provide the right advice for such a potentiometer ?
Thank you very much in advance.
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