Help in choosing a potentiometer as a "Passive preamplifier"

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ginetto61

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Joined 2009
Chris Daly said:
As can a line level source, where power amp input sensitivity sensibly matches.
Click to expand...
if the line leve source is connected to an active preamp you will not have another cable between the pot and the input stage ... just a very short wire
I understand that some line preamps even buffer the input signals arriving at the RCAs to provide a stronger signal to the pot
 
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Chris Daly

Member
Joined 2004
ginetto61 said:
if the line leve source is connected to an active preamp you will not have another cable between the pot and the input stage ... just a very short wire
I understand that some line preamps even buffer the input signals arriving at the RCAs to provide a stronger signal to the pot
Click to expand...
With line level sources you just need attenuation in between to adjust volume level then connecting to a sensibly sensitive power amplifier - a phono input can be a standalone line level source as well. No added buffer is needed, when attenuation is done properly.
 
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hifiamps

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Joined 2016
Agree with DNic. I have a PGA2310 from Nobsound. It was made by BRZHIFI and Nobsound branded. Bought it from Nobsound because they had a US warehouse. Not passive, but excellent sound quality. Neutral, no discernable tonality. Check the specs of the PGA2310. It can drive 600 ohm loads. The unit has a remote control. I never could get the Bluetooth to work for me (asked for a PIN), but I would never use it anyway.

ginetto61, that one is passive and uses relays to switch SMD resistors. BRZHIFI Vol-2 . No experience with this one.

I have used the Allo 24-Step Ladder-Type Attenuator and the DACT style previously mentioned, but only 21 or 24 steps no remote control and passive.
 
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Chris Daly

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Joined 2004
hifiamps said:
Agree with DNic. I have a PGA2310 from Nobsound. It was made by BRZHIFI and Nobsound branded. Bought it from Nobsound because they had a US warehouse. Not passive, but excellent sound quality. Neutral, no discernable tonality. Check the specs of the PGA2310. It can drive 600 ohm loads. The unit has a remote control. I never could get the Bluetooth to work for me (asked for a PIN), but I would never use it anyway.

ginetto61, that one is passive and uses relays to switch SMD resistors. BRZHIFI Vol-2 . No experience with this one.

I have used the Allo 24-Step Ladder-Type Attenuator and the DACT style previously mentioned, but only 21 or 24 steps no remote control and passive.
Click to expand...
Your nearly there, on the positive side gaining valuable experience, with what not to use.
 
tiefbassuebertr

tiefbassuebertr

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Joined 2005
tiefbassuebertragung.de
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ginetto61

Member
Joined 2009
tiefbassuebertr said:
check out this threads:
1) Line up resp. overview both from potentiometers and rotary switches for use as stepped attenuator
https://www.diyaudio.com/community/...kd-and-vishay-and-more-whats-your-fav.153841/
2) passive pre amplifier - overview commercial products: post #9 under
https://www.diyaudio.com/community/threads/passive-preamp.98810/
if there are dead URL's check out by web-archive
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hi thank you for the very kind and valuable information
i can report a very rude test i did
i had a 20klog stepped series attenuator using holco resistors laying around
i put it in a little box with rca ins and outs
i placed it before my preamp with the preamp volume at max
the difference between the original sound and the sound using the stepped attenuator as a volume control was astonishing
at the point that when I see a preamp with a normal pot i am disturbed
even with that very rudimental set up the difference in clarity resolution and soundstage was shocking
 
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Chris Daly

Member
Joined 2004
ginetto61 said:
hi thank you for the very kind and valuable information
i can report a very rude test i did
i had a 20klog stepped series attenuator using holco resistors laying around
i put it in a little box with rca ins and outs
i placed it before my preamp with the preamp volume at max
the difference between the original sound and the sound using the stepped attenuator as a volume control was astonishing
at the point that when I see a preamp with a normal pot i am disturbed
even with that very rudimental set up the difference in clarity resolution and soundstage was shocking
Click to expand...
Many businesses have built upon the difference between normal pots and stepped attenuators. Yes it's a difference , but the problems of a voltage divider steers those willing to try, to find much better solutions, which many ( myself included ) have.

What pots cannot do is to make the shunt resistance variable to suit the music choice. They also have no way of controlling lowest volume without loading the source impedance with the shunt element. The answer is a separate circuit to make the series resistance extremely high at lowest volume, to then restore with mimic of our expectations of volume control. There is then no adverse loading on the source which enables, far better audio still.

You can still use a potentiometer to control the volume of such a circuit, and the potentiometer whilst not passing audio signal, is fully relevant to its operation.
 
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ginetto61

Member
Joined 2009
Chris Daly said:
Many businesses have built upon the difference between normal pots and stepped attenuators. Yes it's a difference , but the problems of a voltage divider steers those willing to try, to find much better solutions, which many ( myself included ) have.

What pots cannot do is to make the shunt resistance variable to suit the music choice. They also have no way of controlling lowest volume without loading the source impedance with the shunt element. The answer is a separate circuit to make the series resistance extremely high at lowest volume, to then restore with mimic of our expectations of volume control. There is then no adverse loading on the source which enables, far better audio still.

You can still use a potentiometer to control the volume of such a circuit, and the potentiometer whilst not passing audio signal, is fully relevant to its operation.
Click to expand...
I think that one problem with pots could be the quality of contact between the wiper and the resistive trace
The resistive trace is on a plastic film that is flexible
Much better a ceramic substrate that does not warp like in cermet pots
 
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Chris Daly

Member
Joined 2004
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ginetto61 said:
I think that one problem with pots could be the quality of contact between the wiper and the resistive trace
The resistive trace is on a plastic film that is flexible
Much better a ceramic substrate that does not warp like in cermet pots
Click to expand...
Certainly is a problem, however there is no problem using a pot in a coupled circuit away from the audio signal.
 
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Lampie519

Lampie519

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Joined 2006
Funny that 80 years ago they knew how to make attenuators and now they don’t..,,
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