Passive preamp to try? balanced

[brucew268]

Does anyone have a passive preamp with balanced inputs/outputs that I might borrow to try? Like Khozmo or an alternate?

The toroid on my Classe preamp has failed and it will be 2-3 months before my source could consider replacing it. I know that my Classe amp should handle passives well, so thought I'd have a look at passives, and consider that as a possible permanent option...

But my amp really prefers a balance input and I prefer the RFI rejection of balanced cables, so I'd like to try one with balanced inputs and outputs.

I know Khozmo offers a balanced passive, but haven't seen one from Tisbury. I don't know if anyone has put together a StereoCoffee as balanced. Others?

I'm probably not looking at Tortuga and preamps in that cost bracket.

[RothwellAudio]

...I know that my Classe amp should handle passives well, so thought I'd have a look at passives...

But my amp really prefers a balance input and I prefer the RFI rejection of balanced cables, so I'd like to try one with balanced inputs and outputs.


I don't know the exact model your power amp is and Classe seem to have a lot on their website but most seem to have a voltage gain of 29dB. That's a bit on the low side for a passive pre-amp so be prepared to use it with the volume control quite high. The input impedance seems to be 50k (single-ended) or 100k (balanced) which is ok for a passive.

RFI rejection actually isn't particularly good with electronically balanced inputs so I wouldn't be swayed in favour of balanced for that reason.
Also, I'm not a fan LDR volume controls whether in a passive configuration or an active one.
I'd suggest that Tisburys are so cheap that it's worth getting one to try out anyway. I'm not really convinced there's much advantage to be gain from a balanced alternative.

[Arkless Electronics]

I don't know the exact model your power amp is and Classe seem to have a lot on their website but most seem to have a voltage gain of 29dB. That's a bit on the low side for a passive pre-amp so be prepared to use it with the volume control quite high. The input impedance seems to be 50k (single-ended) or 100k (balanced) which is ok for a passive.

RFI rejection actually isn't particularly good with electronically balanced inputs so I wouldn't be swayed in favour of balanced for that reason.
Also, I'm not a fan LDR volume controls whether in a passive configuration or an active one.
I'd suggest that Tisburys are so cheap that it's worth getting one to try out anyway. I'm not really convinced there's much advantage to be gain from a balanced alternative.

+1

[brucew268]

My volume put tends to sit around 25% on the dial, and when I bypass the preamp and use the internal volume control from JRMC, 50% volume is plenty. Through various comparisons overs the years, I've found that it sounds better using Balanced in my setup. So I could perhaps test using a single ended preamp, but not sure I'd buy without the balanced option.

[RMutt]

I have an Spl Volume 2 you could try. I'ts not completely passive but it does have balanced inputs and outputs. It's fairly minimalist, no remote and only the one set of inputs, but I found it to be very clear sounding. I only changed it for the convenience of more inputs etc. If I'm honest I think, rather frustratingly, the SPL probably sounds better than the one I replaced it with. Have a look at it online.

[brucew268]

It's worth a go. Let's chat by PM.

[danilo]

Even with 50k amp impedance (100k being the ideal), A 10k or 25k Pot (your choice) and connecting in /out wires, will be All the passive circuitry required.
In the very least.. a 5 minutes to build tester... to base future decisions upon.
If the result proves lifeless/flat sounding then a Passdiy.com B1 buffer kit ~40$ will correct the issue.. and meet all expectations.
IMO Balanced.. outside of a Studio/commercial setup is pointless.

[brucew268]

My results were not lifeless of flat sounding with my initial test of a stepped attenuator passive, though I'm not sure I found an improvement in any area over my active preamp or my DAC-direct-to Amp. Soundstage had less depth but still good width. The presentation of the details and textures was nice with a slight bit of HF spotlighting, but the mids did not have as much body or solidity to them, slightly thin. The sound did not feel as integrated across the frequency spectrum as my existing alternates. This could be down to the silver wiring, or the impedance of 10k rather than 50k, or the passive with neither buffer circuit nor TVC, not sure. More auditioning of other passives required.

I am curious how someone would describe the effects of a buffer circuit as in the B1 kit above in a bit more detail.

[danilo]

Read Nelson's own eloquent explanation here ?? (also a pdf download button if you wish to save it)
https://www.passdiy.com/project/preamplifiers/b1-buffer-preamp

[brucew268]

Oh, I hadn't read "Side E" of the article when I was there last. Thank you for pointing me back that article.

[brucew268]

Even with 50k amp impedance (100k being the ideal), A 10k or 25k Pot (your choice) and connecting in /out wires, will be All the passive circuitry required.
In the very least.. a 5 minutes to build tester... to base future decisions upon.
If the result proves lifeless/flat sounding then a Passdiy.com B1 buffer kit ~40$ will correct the issue.. and meet all expectations.
IMO Balanced.. outside of a Studio/commercial setup is pointless.

Danilo's post got me checking into N.Pass preamp designs, and I built a simple pre-amplifier from an Alps Blue Velvet pot and a B1r2 buffer.Pretty amazing! I'll say something about it under Strokes of Genius.