GUSTARD DAC-R26 Balanced Decoder R2R+1Bit Dual Native Decoding Music Bridge
May 29, 2023 at 7:50 AM Post #6,301 of 8,833
I've come back to opamp controversy with May envy!
It's only a couple of days till June so things should settle.

So here's the detail, so there is no doubt that the R26 does utilise pairs of op-amps in the audio path, the ladder DAC's use these, one per ladder (dual version L&R channel) TI OP1678!
The audio output paths use a pair of TI 01642A but these are in series, which is probably a dual stage process doubling up on the op-amps, as used on many DACs (TDA1541A)

But why is the ladder DAC stage using a dual op-amp?
Because ladder has two outputs and two traces come out of the opamp chip. Refer to yellow and orange arrows on my first post on the subject. It require two opamps. Differential output is created at some stage from this pair.

Regarding OPA1642 (on the main board), it is also audiophile quality dual opamp which support my opinion that low pass active filter is made of a pair of these opamps. Second-order (or higher) LP filter will make measurements looking nice. Not really needed for NOS DAC. Will have detrimental effect on harmonic coherence.
 
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May 29, 2023 at 5:10 PM Post #6,304 of 8,833
Or a Seasonic Prime Fanless TX-700 :wink:


image_2023-05-29_231201398.png
 
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May 30, 2023 at 2:36 AM Post #6,305 of 8,833
Audiophile myth #666: All SMPSs are inferior to linear power supplies.
I had a Allo Volt D+ digital stereo amp which I handed to my daughter for her main system, tried it with a good LPS but it sounded much better with a SMPS.....
 
Jun 1, 2023 at 3:26 AM Post #6,307 of 8,833
No posts in two days?

FINALLY! They started listening :headphones:....and not talking here....Good Job! :laughing: :thumbsup:
 
Jun 1, 2023 at 3:42 AM Post #6,308 of 8,833
Jun 1, 2023 at 4:23 AM Post #6,309 of 8,833
No posts in two days?

FINALLY! They started listening :headphones:....and not talking here....Good Job! :laughing: :thumbsup:
Still all holding the breath...

In meantime we learnt that:
- use opamps become unimportant.
- use SMPS become unimportant too, it can be be even beneficial (while off-topic, as Gustard do not use).

The other thread (in which the first time I presented relevant photos) ended prematurely after the OP had admitted of trusting the reviewer and some unnamed Gustard engineer more than others and was not being interested in a secondary opinion. Opinion? It was an evidence.

Now is a time to:
- admit that honesty of the brand become unimportant, only sound is important, while I can contest it, as there are better sounding DACs in this price range.
- blame a messenger. Didn't happen yet? Oh, yes, in a deleted post (made in error) and couple pages earlier when handling of DSD was disputed.

Sorry @m-i-c-k-e-y, I couldn't resist.
 
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Jun 1, 2023 at 8:16 AM Post #6,310 of 8,833
Progress Report Leo Bodnar clock inside R26 - full shield around PCB

I did add another piece of aluminium tape directly under the LB clock chip before trying the full wrap, seemed to tidy the sound further. (see first pic)

I made up the full sleeve shield using 0.5mm card with aluminium tape adhered to one side and wrapped around edges. This was Lidl beer six pack packaging, no expense spared, seriously though, it's good quality strong board with a printed side which enables the tape to be peeled off if you make a mistake).
Size of shield was 84.5x51mm x2 top and bottom, 15x84.5mm x2 sides.
LB machined end plates were used as templates before getting a scalpel out to cut the holes, and the card was trimmed to size after cutting all the apertures to 16x 51mm before wrapping with aluminium tape. I used the same principle of construction as the LB PCB Ali extrusion and relied on the clamping nuts on the BNCs and antenna to secure the ends. This way the PCB is completely wrapped in shielding and reasonably easily slid out once one end is released by unscrewing the nut/s.

Just so we are clear, the reason I have to make a new shield from scratch, the LB supplied sleeve in extruded aluminium is just too tall to get into the R26. (Available height in the area above the clocks' motherboard connection is just 19mm not 23mm - LB finished product)

On first listen there wasn't a huge difference, this may be because I'd already applied direct shielding cup on top of the LB clock chip and then below as well as the damping pad adhered onto the clock chip and that's given the lion share of any perceivable improvement. These mods was left in place under the full wrap.

If anything I'd say the sound was slightly more solid.

I have to give it a few days listen now to do the mod justice and listen to the usual suspects.....

On a footnote, I don't think mentioned, I did try a very good audio LPS on the LB, one from an Avondale Preamp which I had to use a buck convertor to ramp down the DC output to 7.5v from 18v, which isn't ideal, but sure enough with a more audio refined power supply, (Les W uses many tricks of his trade to gain better sound) there was more solidity to the sound, you were more drawn into what was being presented, it was subtle but you hear the difference when the ZeroZone is put back in. However, these Avondale LPS's aren't available off the shelf, if they were they would be pricey. I would still say that the LB is not that fussy over power unlike other components can be.
I just wanted to hear the difference that a really well designed audio LPS can make.

I might try a SMPS!
 

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Jun 1, 2023 at 9:32 AM Post #6,311 of 8,833
Hello,
I just updated the display firmware. The font is now bigger and the LED option has been added. So it's successfully installed....
However, the loudness dial does not work anymore and is now constantly on "fixed". Remote neither dial on the device works.
I always used it on "fixed" before, - the loudness is also not the same.

Any suggestions? I'm just coming back from a friend with a Windows PC.

If that helps: I first installed the display firmware and then re-installed gustarender 1.42 again, since I experienced massive dropouts using Roon.
My last try to send the device to Gustard.....IF THEY WOULD ANSWER MY EMAILS.

Thanks a lot....I wish I could think about clocks....
 
Jun 1, 2023 at 9:48 AM Post #6,312 of 8,833
Hello,
I just updated the display firmware. The font is now bigger and the LED option has been added. So it's successfully installed....
However, the loudness dial does not work anymore and is now constantly on "fixed". Remote neither dial on the device works.
I always used it on "fixed" before, - the loudness is also not the same.

Any suggestions? I'm just coming back from a friend with a Windows PC.

If that helps: I first installed the display firmware and then re-installed gustarender 1.42 again, since I experienced massive dropouts using Roon.
My last try to send the device to Gustard.....IF THEY WOULD ANSWER MY EMAILS.

Thanks a lot....I wish I could think about clocks....
Have you confirmed that your Dsd direct as well as your NOS setting is off?
 
Jun 1, 2023 at 3:13 PM Post #6,315 of 8,833
Was this the time you were randomly circling components on the R26 ladder and calling them the “multibit Dsd ladder” ? Those were good times.
At least now your batting .500 by correctly identifying those opamps! 🤣
Yip, it was fun. You didn't bring anything from your knowledge, only quoting what Gustard had to say. It was based on unlimited trust to the brand. Now we know you can't trust them anymore, do you?
:)
 

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