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alpha10 output options

PostPosted: January 5th, 2020, 4:42 pm
by itsikhefez
I'm looking for a relay based volume control with flexible outputs and it looks like the alpha10 fits the bill.

The main purpose of the alpha10 will be to control volume for a DIY 300B amp (Tubelab SE).
The amp has enough gain in the input stage that typically a pot between the input jack and and input stage is sufficient for volume control.
The input impedance is 120K.

Besides the tube amp, I would like to toggle output to one of my vintage receivers (either to AUX input or "power amp in" jacks)

Regarding output options, is it possible to:
1) Configure a "passive" output such as the delta1 does not go through alpha20?
2) If yes, is it possible to toggle that via LCDuino or alternatively, have one output "passive" and another active through alpha20 to a different set of jacks?
3) Have a "fixed" output, i.e delta2 to bypass delta1?

Thanks for your help and for this project!

Re: alpha10 output options

PostPosted: January 5th, 2020, 6:07 pm
by amb
itsikhefez wrote:1) Configure a "passive" output such as the delta1 does not go through alpha20?

The α10 does not offer this option, at least not via the δ2’s switching scheme.

2) If yes, is it possible to toggle that via LCDuino or alternatively, have one output "passive" and another active through alpha20 to a different set of jacks?

You can hard-wire a pair of RCA jacks to just after the δ1 (before the α20s). This would be your passive output.

I don’t really recommend this though. The impedance after the attenuator is high-ish and the signal on this node should not travel over long cables outside the chassis. This is the whole point of having the α20 - to keep that run very short and act as a buffer with an ultra-low output impedance. The α20 is very transparent (having very low noise and distortion, and wide bandwidth), the signal doesn’t get degraded going through it.

3) Have a "fixed" output, i.e delta2 to bypass delta1?

This is also not in the α10’s design.

Re: alpha10 output options

PostPosted: January 6th, 2020, 3:18 pm
by itsikhefez
Thanks for your response.
Since I was considering running passive, is 1x gain reasonable to set on the alpha20?

Re: alpha10 output options

PostPosted: January 6th, 2020, 5:03 pm
by amb
itsikhefez wrote:Since I was considering running passive, is 1x gain reasonable to set on the alpha20?

Yes, if that provides enough voltage swing in your system.