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Volume control options for tube preamp

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#83
In my monoblocs I use linear 50k multi turn potmeters after hearing them at a friend's house, and they sounded very good. With conventional linear pot's it's nearly impossible to adjust volume but with these multiturn pots it's easy. Absolutely scratch free and no sound degeneration as far as I can hear.
 
#84
KeesB said:
In my monoblocs I use linear 50k multi turn potmeters after hearing them at a friend's house, and they sounded very good. With conventional linear pot's it's nearly impossible to adjust volume but with these multiturn pots it's easy. Absolutely scratch free and no sound degeneration as far as I can hear.
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Different! These are the small mono Bourns type trimmers or what? Usually adjusted with a small screwdriver. How does that work for stereo and conventional use?

Or the larger Vishay types where you can put a knob on them?

https://www.rapidonline.com/vishay-534b1503jc-50k-2w-multi-turn-wire-wound-potentiometer-65-1060
 
#87
KeesB said:
In my monoblocs I use linear 50k multi turn potmeters after hearing them at a friend's house, and they sounded very good. With conventional linear pot's it's nearly impossible to adjust volume but with these multiturn pots it's easy. Absolutely scratch free and no sound degeneration as far as I can hear.
Click to expand...
IMG_20211022_070242.jpg


Bournes 10 turn pots in my preamp. Previous version was a switched attenuator.
 
#91
jaddie said:
Every single recording you're playing has been run through dozens of "volume controls", some analog, some digital, some with VCAs
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Not in modern plants, certainly not in any of the studios I've built in the last decade. Analogue sources hit an ADC and remain in the data domain until the final DAC. Level changes are 'calculated' in software. The chain is so simple, reliable, efficient and cost effective it would be genuinely surprising if, other than a few oddball niche applications - for example PS Audio's curious choice to wash all their DSD recordings through the kind of Studer consoles I literally gave away in the 2000s - most recordings ever see analogue volume controls.
Re: volume controls, I became satisfied with linear 10-turn pots long ago. In systems with typical gain structures most of the use is within the first two turns.
 
#93
woodturner-fran said:
Most solutions seem to either use matched LDRs (a pain to match) or use processor control, which then often is used for relay input control as well as both kinda go together.
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Just came across this thread, thought I'd put in my two cents worth -- I designed a PIC-controlled LDR volume control years ago and was astonished by the sound, I loved it. I guess it was my introduction to second harmonic tube-like sound. Started to market it and found that I didn't enjoy doing that so stopped.

Someone who was in a position to actually measure the performance found that the channels tracked within 0.2db of each other and to a true log curve (as I recall, the calibration routine used more than twenty points on the curve). And, yes, I used a relay-controlled input selector and it was all controlled by an IR remote and rotary encoder with OLED display to manage it all.

The attached image is of the LDR controller board, everything else was on separate boards.
 

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#94
I've used log plastic ones, 13 and 23 steps pots and now the multiturn pots which to my own surprise sound best. The cost? Aliexpress shop 91119 1008 store - multiturn potm euro 1,57 (50k, 100k) shipping euro 1,09. There are about 6 other shops with comparable prices. Why not order both the plastic ones and the multi turn types so you can decide for yourself which are best.
 
#96
Looking back on this thread, how would wirewound pots work in the input to a tube stage? I imagine that from the nature of wirewounds, they will be linear so will require a fake log resistor. For a 100K linear pot, the fake log resistor should be around 22K from what I read (= 18K), though some say 47K works alright (=32K). 32K would be preferable for an input stage. Wirewounds are also available in dual gang, which is useful.

So what would the advantages and disadvantages be? Could be inductive, but would this be an issue in practice with a dual gang pot? Would the sound quality potentially be better in a length of wire?
 
#100
I'm sure that a multi-turn pot is going to sound good and measure well. But that's not the use I have in mind. I don't use a pot myself - all in software.

This is to make a preamp for somebody else. So must be user friendly - dual gang in other words. I'd certainly consider a dual gang multi-turn pot, but I don't think anyone makes them?

So any opinions on a dual gang 100K wirewound with added resistor for fake log taper?
 
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