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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
sunandmusic
27 posts
 
I prefer the direct connection with my Audio Note DAC 5. It feeds my Plinius SS power amplifier via a passive pre. The line stage in my DAC is basically the Audio Note M6 pre-amplifier line stage and power supply, so no point in doubling up gain. I think it comes down to output impedance (lower the better) and current delivery (not just 2v / 6v) but have enough drive for the next stage (power amp). Keep the interconnects really short, and use an analogue passive / pot or transformer passive.

A key for impedance mismatch is a tipped up balance (no real bass) and reduced dynamics. The rewards for getting it to work is less coloration and lower noise floor (especially if your pre-amp is tubed) and faster slew rates. And more 3D soundstage. If it sounds better with a pre-amp it may be the DAC is too bright already, or the impedance matching is off.
I am not sure it would work so well with an SS DAC and SS power amp though....
georgehifi's avatar
georgehifi
10,312 posts
 
A key for impedance mismatch is a tipped up balance (no real bass)
It’s more to do with the source, if it has an output coupling capacitor being too small (in uF), which yes raise the ouput impedance, when in conjunction with the input impedance of the passive. This forms high pass filter (a low frequency roll off) that can start too early and chop out some of the low bass.
But it’s a simple fix, replace the coupling cap in the source with 2 or 3 x the uF (microfard) and while at it a better quality one.
That's why I prefer sources with direct coupled outputs, no cap to worry about. BEST CAP IS NO CAP.

Cheers George
dragon_vibe
430 posts
 
No matter what the manufacture claims about their volume pot in the DAC I have nearly on all accounts found them to be utterly crap. From personal experience any DAC will sound better with a transparent Pre-Amp sitting between them.

Finding a Transparent musical pre-amp is not as easy as you may think. From all of the pre-amps iv owned i found the MP-1 Atma-Sphere Pre-amp to be the best for me. Dynamics improves by a large margin.

shadorne's avatar
Ag insider logo xs@2x
shadorne
7,467 posts
 
Benchmark make a DAC with built in pre-amp.
mitch2
3,910 posts
 
First, you need to make sure the VC does not result in throwing away bits.
Current best options include those by Empirical Audio and Metrum Acoustics that adjust the reference voltage and operate out of the signal chain.  To me these still retain similar drawbacks as using a really good passive pre, unless a buffer is added.
As dragon_vibe points out, a good, transparent preamp improves on a passive, DAC based, control (for most) by optimizing the signal going into the amplifier(s). In many/most cases, dynamics, tone and dimensionality are improved IME.
A good unity-gain buffer will do the same thing.  I recently auditioned Tortuga's tube buffer and when paired with a passive I have here, I found it to be quiet and very good sounding, particularly for the price.  Anybody running a passive pre should give it a try.  Empirical Audio offers their Final Drive transformer buffers, which would also be worth a try with any type of passive.
One transparent solution I can recommend highly is the SMc Audio VRE-1, a buffered preamp with your choice of 6dB-gain (through the Lundahl transformers) or optional unity-gain.  I use a unity-gain buffer version with a Shallco attenuator built using AN Tantalum resistors.
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