Can we run through the common options for volume control on a tube preamp giving pros and cons?
Examples:
What are you using, how did you make that choice, and how do you like it?
Examples:
- log volume control
- fake log using linear taper with a resistor, and best resistor values
- stepped attenuators of different constructions including shunt types
- TVC and autoformer
- other types
What are you using, how did you make that choice, and how do you like it?
Others will give info like the Zout of a pot at centre vs near the edges etc.
I can tell you I've used cheap pots, RK27 Alpha pots, and stepped attenuater that was Ladder type using 8 relays.
There were not enough steps for me, and I prefer the RK27. The cheap pots are ok, but the lowest part of the volume setting ramp up faster t han RK27, and usually the left and right tapers aren't aligned which means the left channel will make sound before the right at the lowest settings. The 10 o'clocl setting on the RK27 is like 8 o'clock on the cheap one (Bournes).
You can get RK27 for 25$ from Mouser, but 8$ from GD Parts or LCSC...
If I knew more about how to control modern microcircuitry, I'd design one using PGA2310.
EDIT: Maybe I don't have to know... https://www.audiophonics.fr/en/prea...dule-pga2310-with-rotary-encoder-p-13416.html
I can tell you I've used cheap pots, RK27 Alpha pots, and stepped attenuater that was Ladder type using 8 relays.
There were not enough steps for me, and I prefer the RK27. The cheap pots are ok, but the lowest part of the volume setting ramp up faster t han RK27, and usually the left and right tapers aren't aligned which means the left channel will make sound before the right at the lowest settings. The 10 o'clocl setting on the RK27 is like 8 o'clock on the cheap one (Bournes).
You can get RK27 for 25$ from Mouser, but 8$ from GD Parts or LCSC...
If I knew more about how to control modern microcircuitry, I'd design one using PGA2310.
EDIT: Maybe I don't have to know... https://www.audiophonics.fr/en/prea...dule-pga2310-with-rotary-encoder-p-13416.html
A TVC that can handle the full-scale output has a major advantage over the other input attenuation approaches in preserving SNR by attenuating both signal and noise, while decreasing the output impedance.
We use a stepped attenuator with 6 relays arranged in a binary fashion, 6 attenuators with 1, 2, 4, 8, 16 and 32dB attenuation, this gives 1 dB resolution with 64 steps. Much better channel balance than any pot.
Do you know that ALPS only promise 3dB balance for the RK27 or even as much as 5dB at low settings?, with standard 1% resistors in a stepped attenuator you easily get better than 0.2dB balance
Do you know that ALPS only promise 3dB balance for the RK27 or even as much as 5dB at low settings?, with standard 1% resistors in a stepped attenuator you easily get better than 0.2dB balance
IMHO:
Motto: all roads lead to Rome.
p.s. I used TVC, AVC, Noble, TKD, RK40, stepped attenuator, and many potentiometers.
- TVC (only if you have low impedance source). BTW I don't listen SQ waves. 🙂 ;
- AVC (only if you have low impedance source);
- Plastic conductor potentiometers ( Noble, TKD 25xx, ALPS RK40 Black Beauty etc.);
- Good stepping attenuators (for example shunt types);
- Ladder stepping attenuators;
- Series stepping attenuators;
- Simple potentiometers (like ALPS Blue).
Motto: all roads lead to Rome.
p.s. I used TVC, AVC, Noble, TKD, RK40, stepped attenuator, and many potentiometers.
They might, but I've never used one that was perceivably off. They are much better than any bog standard one you'll find at Digi-key anyway 🙂
The problem with a stepped attenuator is the steps. 64 steps of 1db? No thanks. 1024 steps at 0.1db? Maybe.
TVC is transformer based volume control...
AVC is usually short for Automatic Volume Control but I doubt that's the context here.
AVC is usually short for Automatic Volume Control but I doubt that's the context here.
So, nobody likes the digitally controlled ananlog volume control chips?
TI has several, as do others. Yes, they take some control, but they do nail the audio specs and tracking, plus give you the option of any number of pre-set levels.
https://www.ti.com/audio-ic/amplifiers/volume-control-ics/products.html
TI has several, as do others. Yes, they take some control, but they do nail the audio specs and tracking, plus give you the option of any number of pre-set levels.
https://www.ti.com/audio-ic/amplifiers/volume-control-ics/products.html
I've been looking for a simple good quality stereo 100K log taper, or even linear which I could make into a fake log taper, for sale in the UK. Very poor choice. I couldn't find any of the conductive plastic ones you mention. The Alps Blue is available but I was expecting more choice than that. Maybe I'll have to look at European suppliers. Any suggestions?
TKD is conductive plastic.
I usually use CP-2511.
https://www.hificollective.co.uk/catalog/tkd-potentiometers.html
This thread made me look for attenuators with more steps. I found this one and I've ordered one up to check it out. From the looks of it, it should be 1024 steps I think... 10 relays per channel.
https://www.aliexpress.com/item/4000480828404.html?spm=a2g0o.order_list.0.0.21ef1802lAkeNJ
https://www.aliexpress.com/item/4000480828404.html?spm=a2g0o.order_list.0.0.21ef1802lAkeNJ