I would like to make the shunt with the potentiometer and resistor in parallel (24K ohm resistor) like Andy did with his mod.1. If the attached diagram is correct I should jumper pins 2 and 3 of the Alps and ground them and then put the 12k ohm resistor in series at the signal input on pin 1 and take the output from pin 1. I'm not clear where I should connect the parallel shunt resistor (24k): to terminals 2 and 3 or 1 and 3?
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My current setup is a mix of software and stepped shunt. I think both degrade the sound, but it's more convenient to adjust the volume in software. I can't remember how many positions it's got 20+, but I know I could manage with far less positions. The chinese do a cheap blue 2 & 4 pole stepper with 20+ positions, some come bare, others as a kit, or preassembled. They also do a lime/yellow stepper which I found to be rather stiff in comparison. Anyway on a tight budget I'd suggest the 4 pole blue and just use a small group of the positions with your favourite resistors and do the rest in software. I do wish motorised steppers were more affordable.
If you have at hand any kind of invering amplifier, you can use as volume control with linear pots. Simply ground noninverting input, tie one side of pot to general input, other to general output and amp output, and wiper to inverting input.
You may add small fixed resistors at each end to limit maximum attenuation and or minimum as desired.
You may add small fixed resistors at each end to limit maximum attenuation and or minimum as desired.
Why not an AVC from Intact Audio? The price went up, but it could still be a better bet in the long run. I beleive the one with fewer steps (14?) run about $300/pair. Also some TVCs available, but more expensive and more steps.
What i would really like is a relayed switch to make my AVC operable with a remote or music player (volumio, etc).
Edit: I didn’t realize this thread started quite a while ago…
What i would really like is a relayed switch to make my AVC operable with a remote or music player (volumio, etc).
Edit: I didn’t realize this thread started quite a while ago…
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An advantage of digital or partly digital volume control over any fully analogue volume control is that it solves the intersample overshoot issue.
Many digital recordings have their largest samples normalized to 0 dBFS, meaning that the interpolated/reconstructed waveform has to exceed 0 dBFS. Most DACs have no headroom at all for this, so they hard clip on these music recordings. Digitally attenuating the signal by a few decibels solves that.
Careful that you don't impose too stiff a load on the tube preamp, which will distort when loaded too much.
Marcel, how much would you go down in the digital domain (minimum) to avoid most clipping?
Between 1 dB and 3.5 dB. 1 dB suffices for most recordings, but some require a bit more. The Benchmark Medis website has (or at least had the last time I looked) some interesting information on it - they produce DACs that have headroom by design and therefore haven't got this issue.
I wanted to compare a stepped attenuator with an Alps pot but only had a 5 or 6 position switch. So I just noted the positions of the pot I used most often and just created the steps to be the same.
The sound is clearer with the switch and I am happy with the settings I have.
Just a cheap way of playing.
The sound is clearer with the switch and I am happy with the settings I have.
Just a cheap way of playing.
IMO the only high quality Alps potentiometer is the (old, rare and expensive) RK40 Black series.
Others (like RK27 Blue) are good, but not better, than other mediocre potentiometers.
Digital volume control:
I set my DAC -3dB as initial parameter ... and NEVER use again digital volume control. 😉
Any -builds with good resistors- stepped attenuator or good potentiometer better, than -average- digital volume controls.
Others (like RK27 Blue) are good, but not better, than other mediocre potentiometers.
Digital volume control:
I set my DAC -3dB as initial parameter ... and NEVER use again digital volume control. 😉
Any -builds with good resistors- stepped attenuator or good potentiometer better, than -average- digital volume controls.
Me too...
.
Hi Andy
.
This is the Load resistor. With Req of the generator forms an attenuation.
It is not only the attenuation of voltage level but rather att. of "energy".
It will result a very audible compressor-limiter effect.
If the -db level of att. is higher the effect is more present.
that will be if the Load resistor is lower values...
.
That is why the pots in general are weak points...
because of that other types of att. present
like multi secondary taps transformers, chokes with taps for att.
and so.
.
Even the input Rg on the grid could be replaced with high inductance L to avoid resistive damping loss
.
Why don't You employ step-down transformer? The source should be not so high impedance so the xfrm is not complicated
and shouldn't be so expensive?
Why don't I employ a step-down transformer? Because it will colour the sound to some extent, so better left out if there are other solutions. I go with simple and cheap unless I have to spend money on something I can't do without like a good OPT. My volume control is in software - I just use a shunt volume control for preamps I make for friends. I have some extremely good vintage resistors and I use a 100K Omeg plastic pot. Sounds pretty good and is dirt cheap, like peanuts.
Than OK
but with that solution You will make Your very good tube system (26, EL12n...) - sound cheap.
The quality of the resistors are irrelevant...
You will not have "coloration" with a transformer properly choosen in respect to the source and terminated after the measurements...
.
What is the output p-p voltage level of the source and impedance?
What is the value of -Ug in the preamp?
but with that solution You will make Your very good tube system (26, EL12n...) - sound cheap.
The quality of the resistors are irrelevant...
You will not have "coloration" with a transformer properly choosen in respect to the source and terminated after the measurements...
.
What is the output p-p voltage level of the source and impedance?
What is the value of -Ug in the preamp?
My experience is that the potentiometer colors sound the most, the shunt potentiometer less and the AVC the least. Borrow AVC from someone to hear and everything will be clear.
"My experience is that the potentiometer colors sound the most, the shunt potentiometer less and the AVC the least. Borrow AVC from someone to hear and everything will be clear."
Yes, I'm sure that's correct. But this isn't for me - I don't use a preamp at all. It's for making one or two preamps for friends, so I don't want to throw money at that. I just need "good enough". I'm well aware that I could throw money at a preamp in all kinds of ways, but that would be for others who use preamps and want to do that! Good AVCs aren't cheap. Neither are good stepped attenuators.
Yes, I'm sure that's correct. But this isn't for me - I don't use a preamp at all. It's for making one or two preamps for friends, so I don't want to throw money at that. I just need "good enough". I'm well aware that I could throw money at a preamp in all kinds of ways, but that would be for others who use preamps and want to do that! Good AVCs aren't cheap. Neither are good stepped attenuators.
Hi Andy have you seen the blog by Pedja Rogic on volume pot, perhaps that's a cheap & good way.
Go audialonline & search.
Cheers
Go audialonline & search.
Cheers