RoPieee & power amps

Hi. Sorry I’m not sure if this is a RoPieee matter - but I thought I’d start by asking here :slight_smile:

My setup is: RPi 3B+ running RoPieee 290, JustBoom DAC Hat, RCA output to McIntosh MC275 tube power amp. Roon Core is on a separate Win 10 dedicated box.

Sound quality is very good indeed - but volume is limited (pretty quiet). Setup in Roon is for Device Volume - which I’m controlling through the Roon app on my phone.

So, is there any way to increase the output / gain from the RPi / JB Hat please?

TIA

Rob

Not familiar with the McIntosh, but I think you are missing a pre-amp stage and you’re not going to get a signal from the the RPi that can drive the power amp.

Thanks @Martin_Webster I strongly suspect you’re right!! I thought I’d ask the group though in case the RPi / JB DAC has holding back a little. The fewer components in the signal path I can use generally the better - but looks like pre-amp needed…

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Might be cheaper to get a new DAC with a preamp section.

Probably up the SQ, also.

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Thanks @xxx. I’ll take a look.

I think it has to do with the impedance matching of your DAC and your power amp.

I use Ropieee on a RPi 3B+ with a HifiBerry DAC+ Pro XLR HAT going (via XLR) drectly to two monoblock Hypex NC400 power amps.

I have more volume available than I can listen to without hurting my ears, the Hypex amps get very loud indeed. When playing at any level, quiet or normal listening levels or loudly, signal quality is excellent (my subjective take). I have no preamp.

XLR has one great advantage over RCA: its 4V instead of (normally) 2V for single-ended (RCA). And that ofcourse also translates into volume as well.

Oh, I should add though that I also used the RPi and Ropieee with the same Hypex amps using my iFi iDAC 2 (connected to the RPi via USB.) The iDAC 2 has RCA out – and I had no issue also blasting the volume at any level.

So… DAC --direct–> Amplifier via RCA or XLR can work just fine. I really do think its an impedance matching issue in your case, if you can get decent volume out of your Mcintosh.

Thx @CRo. Very useful feedback.

Your monoblocks appear to be 400 watts class D. My mc275 is 75w stereo class A. This is obviously a big difference!! I’ve got both xlr and RCA inputs on the amp but this is a slight red herring in that I’m probably going to relocate my RPi to my office with a new Creek Evolution 100A amp. The Creek has xlr and RCA inputs too but much greater power. It also has a direct option to the power amp stage that I’ll try to compare with going via the preamp section first.

Hi Rob,

it shouldn’t matter if the amp is 75W or 400W. You use maybe 5W at normal listening levels. Transients in the music, yes they will need more. Your 75W tube amp should do just fine with most reasonable speakers at normal listening levels.

What you’re saying is, they are really quiet when playing directly from your DAC even with the volume turned up, and that sounds like your DACs output impedance and your tube amp’s input impedance are not matched. In that case, you bet, a preamp will help. A preamp or a buffer will correct that miss-match.

Variables:
DAC output impedance
Amp input impedance
Amp power rating at what speaker impedance (4ohm? 8ohm?)
Speaker impedance (which varies at different frquencies, so the range is good to know)
Speaker sensitivity

Brilliant info thx!

I’m off to investigate the impedance specs now…