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Any comments on DAC going direct to power amplifier or to pre-ampliifer?

My local retailer HIGHLY RECOMMENDS the use of a pre-amplifier.  Bricasti believes that going direct to a power amplifier sounds better.  And, I also know that everyone had a "different opinion" about going direct or using a pre-amplifier.  

I am running my Bricast1 M1 SE DAC direct to my Hypex NCore NC400 Bridged Mono Block class D power amplifiers (no pre-amplifier) and like the sound quality very much.   

For me, the sound is more natural and clearer by going direct to a power amplifier. Of course, I think the M1 SE DAC has special “custom" circuits in the analog section to make it sound so good. I returned home and listened to my system.  It sounds terrific and I continue to enjoy and recommend the Bricasti M1 SE DAC.

Please note that we removed the R141 (circuit) from my Hypex NCore NC400 bridged mono blocks, thus lowering amplifier gain by 14 dB, requiring 14 dB higher M1 volume setting for same playback level.  Bricasti says the goal is to have the M1 CLOSE to 0db front panel attenuation.  If you reduce the volume on the M1 SE DAC, you cause more bit reduction meaning you lose sound quality.   We discussed this modification with Hypex and they approved the removal of the R141 circuit.  They suggested we be very careful removing the 4 R141 chips (for my 4 NC400 amplifiers) to avoid board damage.  

I noticed that many of the newer DAC’s (even the new Ayre QX-5 Twenty DAC and many others) have volume controls meaning their DAC/Pre-amplifiers are designed to go direct to a power amplifier (as an option, of course).  

What are your experiences of going direct to a power amplifier or using a pre-amplifier?  Have you compared going direct vs. going to a pre-amplfier and noticed any sound quality differences?  Have you gotten different results from using different DAC's and amplifiers?   Your comments are appreciated.  Thanks.





hgeifman
hgeifman OP
2,243 posts
 
Okay.  I changed my mind about having my DAC going direct to my power amp. The volume control in most DAC's (including my DAC) is indeed implemented in the digital domain and, therefore, when adjusted down, bits are lost AND so is the sound quality. This is a fact of digital volume controls. In other words, reducing a DAC's volume causes bits to be dropped resulting in reduced sound quality.

As an experiment, I discovered that my 2nd DAC sounded better than my first DAC both going direct to my power amplifier. My assumption is DAC #1 was dropping more digital bits then DAC #2 causing the sound quality differences. Based on this experiment, I am now considering using a pre-amp.

I also continue to believe that everyone has a different opinion on going either direct to a power amplifier or using a pre-amplifier. I believe these differences are because we all hear differently and different equipment sounds different in different conditions. Some DAC's may drop bits in different increments (I do not know). 

I plan on adding a preamp/DAC to my audio system shortly.  
georgehifi's avatar
georgehifi
10,312 posts
 
As Wadia and Mark Levinson say with their dacs/cdp players with digital domain volume controls.
Is that they must be used in the top 25% of their range to get the best sound from them, that is why they put adjustable output links inside in the analogue stage to give different gains, so then the digital volume control can be use in it’s top 25% range. Bricasti do this also with their M1, it’s done different but the end result is the same.

If you can’t do this with your dac or cdp, then the next best is to do it with a passive volume control after the dac, set it, so that then you can use (the digital volume control) in the top 25% of it’s range.

No need to buy an expensive preamp, because you’ve already proved your dac has more than enough gain, too much in fact because you can’t use the digital VC in the top of it’s range.

Cheers George

mitch2
4,022 posts
 
Something about going DAC-direct, or using a passive volume control behind the DAC is simply not satisfying to me in the long term.  I have had good quality resistor-passive volume controls, transformer/autoformer passive controls, and even the highly regarded Metrum Adagio DAC that changes volume by adjusting the reference voltage so no bits are lost.   All of these approaches resulted in a clear, natural sound without bloat but, for me, having an active (unity gain) buffer or a low gain preamp in front of the amplifiers, restored the punch, dynamics, and full-sounding tone I hear from live music.  In my system, a high quality unity gain buffer/preamp is the ticket.  However, I recently auditioned the Tortuga  tube  preamp buffer that does pretty much the same thing, at not quite the same level, but for a lot less money.  
georgehifi's avatar
georgehifi
10,312 posts
 
  • My local retailer HIGHLY RECOMMENDS the use of a pre-amplifier.

  • Couldn't be that he wants to sell you a preamp?

  • Your Bricasti’s output buffer stage is as good if not better than most active preamps, especially tube preamps.

  • Did you calibrate the analogue gain so that digital VC is used in the last 25% of it max output?
Bricasti instructions to set the analog max output level:
  • The next stage, at the analog out of the converter for the gain and filter sections there is a fully differential analog design with fast high slew rate analog operational amps. This is followed by 2 transistor designed output buffer sections, balanced and unbalanced, each separately buffered and isolated. The balanced output level as shipped is set with a fixed resistor at +13.5 dbm. For custom level matching, an internal the jumper on the board can be moved to engage a precision adjustable potentiometer. This adjustment is set from the rear panel screw near the XLR connector. When the potentiometer feature is engaged the level is adjustable from +8 to +23 dbm and can be referenced to a fraction of a db to match any setup. This level is set as a default +16 dbm at the factory so when the jumper is engaged this will be the new level. Please contact us for detailed instructions on how to change and set these levels. The unbalanced is set to normal hi fi levels of 2V RMS (+8dbm) by precision resistor values on the board.
Cheers George
shadorne's avatar
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shadorne
7,477 posts
 
Benchmark DAC are designed to drive power amps and many models handle a small number of inputs in order to provide limited pre-amp capability for 4 inputs (no phono).
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