Latest Thread Images

REVIEW: Audio-GD Roc
Apr 11, 2010 at 7:16 AM Post #168 of 322
Quote:

Originally Posted by russell-w /img/forum/go_quote.gif
I just placed an order as well. It appears he is giving a 5% discount as the quote is for $950. The impatient waiting begins.


beerchug.gif
 
Apr 11, 2010 at 9:12 AM Post #169 of 322
Can you smeeeellll what the ROC is cookin'?????!?!!?


I ordered mine the other day, I will post my impressions once it comes in using Beyer dt880 600 ohms.

Can some of you post your pics of your roc setup with headphones?

Would love to see em.
 
Apr 11, 2010 at 6:43 PM Post #172 of 322
Not exactly on topic, but here goes:

Can I connect the ROC via the ACSS to my DAC-19 DSP ?

I've been considering either C2 or Roc as companion for DAC-19 (via ACSS), but I'm not sure if ROC can be connected that way.

If ACSS does not apply as interface between DAC19 and Roc, are there any real benefits to be had compared to C2 via ACSS ?
 
Apr 12, 2010 at 1:15 AM Post #173 of 322
Quote:

Originally Posted by audiofil /img/forum/go_quote.gif
Can I connect the ROC via the ACSS to my DAC-19 DSP ?

I've been considering either C2 or Roc as companion for DAC-19 (via ACSS), but I'm not sure if ROC can be connected that way.

If ACSS does not apply as interface between DAC19 and Roc, are there any real benefits to be had compared to C2 via ACSS ?


You can, but you will have just 2 out of 4 Roc's channels "working". Just single ended and no balanced headphone/preamp output.

Why?

In input stage of A-GD's ACSS (CAST) balanced preamps/headamps (Roc being one of them) voltage signal inputs (RCA and XLR) are first cloned to inverted signals (RCA) or "fixed" to completely symmetric inverted signals (XLR) and this symmetric balanced voltage signals are converted to symmetric balanced current signals. No matter the voltage input - RCA or XLR, after input stage you have symmetrical balanced current signal entering the ACSS/CAST gain stage (the fancy black boxes that read "BPM-7110 V2.0" in Roc's case).

ACSS (current) inputs on the other hand do not go through input stage - they go directly to gain stage - which is quite an advantage: ACSS current signals bypass amp's input stage and DAC's output stage (where DAC's native current signal is converted to "standard" voltage signal to make A-GD's DACs "compatible" with rest of the audio world).

And there also lies the problem: Roc is expecting balanced (true, using 3 wires) ACSS input to enter it's gain stage, while DAC-19 has single ended ("person", using 2 wires) ACSS output. In such configuration Roc would not give balanced output at all - two channels would "work" and two inverted channels would be "idle". Voltage inputs would give expected balanced current signal to gain stage, but there is no way to clone "person" ACSS current signal before gain stage - you had to have balanced ACSS source for that (allegedly, Krell CAST balanced source would work too
wink.gif
).

So, if DAC-19 is your source, with ACSS connection Roc has no benefits over C2.
 
Apr 12, 2010 at 8:58 AM Post #174 of 322
Is ROCK worth of buying if I would use it with XLR input only (with ballanced headphones)?
I have Mytek DAC with XLR out and I'm looking for balanced amp.
Heaving read this and other threads concerning ROC I'm not sure if there is point to buy this amp if you are not going to use it with DAC with ACSS.
For ROC are there any benefits of using XLR instead of RCA?
 
Apr 12, 2010 at 11:56 AM Post #175 of 322
Quote:

Originally Posted by FauDrei /img/forum/go_quote.gif
You can, but you will have just 2 out of 4 Roc's channels "working". Just single ended and no balanced headphone/preamp output.
................................................

So, if DAC-19 is your source, with ACSS connection Roc has no benefits over C2.


Thank you very much FauDrei, excellent explanation!
This takes care of the ACSS connection.

Now this leaves me two possibilities:
1. DAC19 (in SE mode) -->> ROC -->> balanced K701
2. DAC19 (ACSS mode) -->> C2 (ACSS input) -->> K701 (normal, unbalanced)

Would no.1 still be superior to no.2 ?
If so I'll buy the ROC and may take into consideration a future upgrade to a balanced ACSS DAC for it (like REF5).
But this cannot happen soon (a year, maybe more), nor am I pleased about outputting at least another grand over what I already own.

PS: And I love the DAC-19 DSP very much
smily_headphones1.gif
 
Apr 12, 2010 at 12:09 PM Post #176 of 322
Quote:

Originally Posted by mirh /img/forum/go_quote.gif
Is ROCK worth of buying if I would use it with XLR input only (with ballanced headphones)?
I have Mytek DAC with XLR out and I'm looking for balanced amp.
Heaving read this and other threads concerning ROC I'm not sure if there is point to buy this amp if you are not going to use it with DAC with ACSS.
For ROC are there any benefits of using XLR instead of RCA?


XLR input to balanced headphones makes full use of the Roc, so yes.
 
Apr 12, 2010 at 2:37 PM Post #178 of 322
Quote:

Originally Posted by mirh /img/forum/go_quote.gif
Is ROCK worth of buying if I would use it with XLR input only (with ballanced headphones)?
...
For ROC are there any benefits of using XLR instead of RCA?


Yes and yes.

The inputs "preference" goes like this: 1. ACSS, 2. XLR, 3. RCA; ACSS having highest s/n ratio and being most transparent and not much affected by interconnects quality; XLR having slightly lower s/n and more dependent on interconnects quality; RCA having "lowest" s/n and most affected by interconnects quality.

According to this explanation it would be logical to aim for ACSS connection. Take note though - the "worst" s/n ratio of Roc's (RCA) input is 116dB. Not many sources can match that s/n and, practically, on all inputs Roc is quiet as much as the connected source. Also Roc's input stage in it's cloning/proofing and V/I conversion of XLR and RCA inputs slightly increases signal dynamics (compared to direct ACSS input) so those voltage inputs may seem more vivid and be perceived as "better" than the "best" ACSS input. Finally, all those differences between inputs may be perceived only in very resolving systems (excellent source, excellent headphones) and in great majority of cases the input differences would be negligible and go unnoticed. It can safely be said that, no matter the input, you will be listening to your source and not Roc's inputs.
Quote:

Originally Posted by audiofil /img/forum/go_quote.gif
Now this leaves me two possibilities:
1. DAC19 (in SE mode) -->> ROC -->> balanced K701
2. DAC19 (ACSS mode) -->> C2 (ACSS input) -->> K701 (normal, unbalanced)

Would no.1 still be superior to no.2 ?


My vote goes for 1.

K701 balanced are much better than normal K701 (have you seen the frequency graph that visibly demonstrates those differences?), while ACSS input is just marginally better than RCA. So, IMO, 1. is superior to 2., no contest.

Quote:

Originally Posted by mirh /img/forum/go_quote.gif
Is Audio-gd ACSS the same concept as "Constant current drive" by this producer (QES Labs):

Balanced Headphone Amplifier Amp Studio Reference for professional use - QES Labs


"Constant current drive" is somewhat vaguely explained on QES site so I can't deduct anything from information given there.

I'd say though, tha ACSS would primary be "constant voltage drive": there is constant voltage between components and current changes are modulating the signal, as opposed to "normal" drive between components where the current is, more or less, constant and voltage swings represent the signal.

Might be wrong, in any case not enough information from QES.
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 2 (members: 0, guests: 2)
Back
Top