Im just starting a build around a Purifi 1ET400A Eval1 as an integrated with a passive 10k shunt stepped attenuator preamp. Confirmed with Purifi directly that this is ok when using the input board in high gain mode.
My source is a Chord Qutest DAC (output impedance 0.025 ohms, unbalanced rca). Ive done this before with an amplifier with an unbalanced input and was really pleased with the results, but im a bit stuck on how best to handle the balance stepped attenuator with the unbalanced source.
Do I run my unbalanced input into a 2 pole stepped attenuator, and then wire that to the balanced input combining the earth and cold signal.
Or take the unbalanced input into a 4 pole attenuator and then to the Purifi.
The former is cheaper using a 2-pole attenuator but feel there are nuances here that I don't yet understand. Help appreciated.
My source is a Chord Qutest DAC (output impedance 0.025 ohms, unbalanced rca). Ive done this before with an amplifier with an unbalanced input and was really pleased with the results, but im a bit stuck on how best to handle the balance stepped attenuator with the unbalanced source.
Do I run my unbalanced input into a 2 pole stepped attenuator, and then wire that to the balanced input combining the earth and cold signal.
Or take the unbalanced input into a 4 pole attenuator and then to the Purifi.
The former is cheaper using a 2-pole attenuator but feel there are nuances here that I don't yet understand. Help appreciated.
Verify with Purifi, but there should be no problem connecting an unbalanced source to its balanced input.
With an unbalanced source, only an unbalanced attenuator is needed.
Of course, you could build an unbal/bal converter, but you may not notice any improvement,
even though technically there would be some (noise and CMR).
With an unbalanced source, only an unbalanced attenuator is needed.
Of course, you could build an unbal/bal converter, but you may not notice any improvement,
even though technically there would be some (noise and CMR).
The Qutest doesn't provide volume control unfortunately (the Hugo 2 and TT2 do) but I do input into the Qutest from a PC running Lyrion Media server where I can software attenuate. Just feel a good quality stepped attenuator would be better and give less risk to full volume accidents!.
I suppose i could sell the qutest and get a DAC with balanced output and volume control.
I suppose i could sell the qutest and get a DAC with balanced output and volume control.
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I'll double check with them. Had assumed you could generally do that as you could always just plug in an rca to xlr converter. But definitely worth checking. An unbalanced attenuator would certainly be cheaper.
The more I think about it changing the DAC is going to be easiest. No need to buy a two or four pole attenuator and you only need a simple enclosure with power on.
Just as an option... You could replace the 0-ohm resistors (0dB gain setting) with something like 500-1000 ohm resistors (tune the values to ensure there's no danger to your speakers in the event of an accidental "full blast" scenario). Just keep J14 and J15 "open", i.e. remove all shunts.
