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Volume control options for tube preamp

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#102
andyjevans said:
.... I don't think anyone makes them?
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They're available, the 100k Bourns 3549S-2AA-104/104A on Digikey for example. The sample blue Bourns in the parts bin are non-magnetic. basically variable tapped wire wound resistors.
It was an ear choice for me which should be revisited after so many years. Additional advantages are matching and reliability. Never had a scratchy sample. From a usability perspective some hate them. Without a vernier dial level indication is mostly by ear. Never found it an issue here. Current production vernier dials appear to be plastic and pretty low quality. Fortunately I have a stock of 60's metal units salvaged from an AM transmitter decommission. 🙂
 
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#105
euro21 said:
Mouser has in stock: https://eu.mouser.com/ProductDetail/Bourns/3549S-2AA-104-104A?qs=8E7K6uVrowcGxGElVSCOrQ==

I exclusively use carbon plastic pots for volume controller (if I use it at all): TKD, Noble, Alps "Black" (RK40).

BTW Mouser also sells Burns conductive plastic ones.
For example:
https://eu.mouser.com/ProductDetail/Bourns/91A1A-B24-D17L?qs=1v0N1zrvLE6QmUGoCSSrTA==
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Thanks - Mouser looks like the choice in the UK. So seriously considering this one, £41 inc and free delivery.
 
#106
andyjevans said:
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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Andy don't use volume software is known reduce bits so reduce information.
 
#107
merlin el mago said:
Andy don't use volume software is known reduce bits so reduce information.
Click to expand...
Yes, I'm aware of some of the views on this, but as I've said before there is deliberately only enough gain in my system to listen at peak comfort levels when the software volume setting is at max. So I'm usually at around 80% of max volume where I doubt that it makes much difference. Everything I listen to is on my Mac Pro - archived CDs, YT, Freeview TV channels, songwriting software like Garageband and so on. No other source. I really don't want to be continually adjusting a volume control on an amplifier a few feet away when I'm sitting at my computer. Sometimes the user interface comes before any theoretical perfectionism in the audio system which is also why I don't listen to vinyl anymore.
 
#108
I use volume controllers (pots, or TVC/AVC), but in practice the volume -almost- never changing, or the alteration is only few dB (overnight decreasing).
In my theory the rough volume settings would be fix (attenuator with good -but not especially pricey- resistors), and the "volume controller" would be few steps very good (if it's expensive, it's okay, because you don't need much) resistor or potmeter.
 
#109
euro21 said:
I use volume controllers (pots, or TVC/AVC), but in practice the volume -almost- never changing, or the alteration is only few dB (overnight decreasing).
In my theory the rough volume settings would be fix (attenuator with good -but not especially pricey- resistors), and the "volume controller" would be few steps very good (if it's expensive, it's okay, because you don't need much) resistor or potmeter.
Click to expand...
Same thing here. There is just single optimal loudness level for a given couch and speaker position in a given room. I only need volume control (a notch up or notch down) because CDs may have different levels. My 10-step autoformer control covers more volume adjustment than I need.
 
#110
andyjevans said:
Yes, I'm aware of some of the views on this, but as I've said before there is deliberately only enough gain in my system to listen at peak comfort levels when the software volume setting is at max. So I'm usually at around 80% of max volume where I doubt that it makes much difference. Everything I listen to is on my Mac Pro - archived CDs, YT, Freeview TV channels, songwriting software like Garageband and so on. No other source. I really don't want to be continually adjusting a volume control on an amplifier a few feet away when I'm sitting at my computer. Sometimes the user interface comes before any theoretical perfectionism in the audio system which is also why I don't listen to vinyl anymore.
Click to expand...
Mine AVC with Shallco is motorized, so can control at distance like TV
 
#111
There are lotts of options agreed. If you want plastic sound use a plastic pott. Better is a steeped attenuator in my experience but depends on type of resistors one uses. Cheap metal film will sound course and grainy compared to say the naked foil types.you get what you pay for or what you are looking for. Each has its benifits and draw backs. Eventually one has to make a choice and hand over the cash.
 
#114
Im using Khozmo
551D5ECA-21EF-4555-B657-AF7C5032AFCB.jpeg
 
#118
andyjevans said:
How does this work, being a chip? What's the input and output impedance?

I've seen a few Chinese boards with remote at decent prices, but wondering how easy it is just to use the DIP version on some stripboard without the remote option?
Click to expand...
Input loading is nominally 10KΩ but they recommend the source impedance
be less than 2K preferably under 600 Ω. That will require care with tubes but
is trivial with opamps. Output impedance is low and can drive a 600 Ω load.
Crosstalk is -130dB at 20KHz and gets better as frequency goes down. They
are very easily daisy chained for control so you can run 3 or 4 (I'm doing that
for 5.1 surround). I've been running these for 6 years and have never heard
any quirks of any kind including Full Scale noise with no 'incomplete mute'.

Channel tracking is nearly perfect and being 0.5dB/step you can implement
'balance' control by offsetting the control numbers. The step size is so fine that
I use 2 steps per change meaning I only have 1 dB resolution and then use that
volume number to drive the display which you'll want since there is no absolute
knob with a pointer. You can use a rotary encoder if you want a physical knob.

Those are the PROS so what are the CONS? The control registers have to be
loaded to work. You could do it with logic chips (= difficult and prone to errors)
or use a microcontroller like a PIC or Arduino (I use Arduino) which is cheap
and can do other housekeeping chores like remote IR receive, rotary encoder
input, input selection, fade up/down maybe control other chips as well. Once you
have the mandatory control processor, IR remote will increase the price less than
$1 for the IR receive module. In my case the IR remote is the same as the TV
meaning 1 remote for input selection, volume and channel selection just like TVs
of old. Use your imagination.

G²
 
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