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Old 1st January 2012, 04:24 PM   #3441
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Quote:
Originally Posted by PreSapian View Post
sorry siva, the info's become to diverse for me to follow. could you outline the difference between rev c and e for those who have been away like me?
The differences are solely in the compensation and stability components, and can be fitted on Rev C V1.2, 1.3 and 1.4 boards.

For Rev C:
C10=22pF
C32=150pF
C34=10pF
R42=47R (can be omitted, i.e. shorted)

For Rev E:
C10=27pF..33pF (higher is less stable) 2% Silver Mica (preferred)
C32 =150pF..330pF (higher is more stable) FKP2 (preferred)
C34=47pF..100pF (higher is more stable) 2-5% Silver Mica (preferred)
R42=0

With 27/330/100, the sonic impressions of Rev E are:
1) Immersive, palpable, forward soundstage
2) Taut, tight, percussive mid-bass definition and dynamics
3) Slightly edgier upper mids

Simulation indicates slightly higher THD20 (~6 dB) for Rev E over Rev C, but mostly H2 (i.e. warmer sonics). Edgier upper-mids of Rev E can be tamed with the LF01 Class-A hybrid/discrete opamp module, without loss of other sonic benefits.
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Old 1st January 2012, 05:18 PM   #3442
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edgier upper mid could be contributed by the material choice of silver micas. I certainly found them bright when i had them swapped in place of c10/32 (original rev C value) though again, with a sharper imaging and more athletic transients.

was any alternative caps tried for c10/34 in rev E specification?
i could actually order some copper wirewound types as seen here վ *Ĥ 100pF 125V OFC 7x15 -Ա
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Old 1st January 2012, 05:25 PM   #3443
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While the alternate compensation works, is stable and (maybe) sounds better it must be taken in account also that some of Mauro's goals had when he designed RevC are gone:

  • higher measured distortion
  • Rev C dumping factor linearization after 10Khz is no more effective
  • high frequency response is more rolled-off
Particularly C34 should be kept as low as possible, 100pF in practice nulls C10's positive feedback, I discourage the use of such value.

Going, step by step, from 100pF to 68pf, 47pF and 33pF you can actually ear bass firmness increasing with 47pF the value with better overall balance.

I consider that compensantion only a very instructive experiment and I don't encourage its use unless willing to experiment.

I'm still evaluating it and I've not yet decided if I'll include it as an alternate compensation for my Fremen Edition.

In fact omitting C5, grounding LM3886 to PGND and replacing LM318's PS bass, refinement and soundstage are vastly improved without impact on Mauro's goals.
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Old 2nd January 2012, 10:59 AM   #3444
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I just removed C17,18,19,20 and replaced C7 with a 0.1uF X2 cap, with the original C13 that came with the TP kit bypassed, the sound just continues to amaze me. I wonder whether new power supply for LM318 is necessary, but amazing things just never stop popping up.
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Old 2nd January 2012, 11:26 AM   #3445
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Quote:
Originally Posted by soongsc View Post
I just removed C17,18,19,20 and replaced C7 with a 0.1uF X2 cap
...
the sound just continues to amaze me.
Didn't told you to remove those bypases?

For C7 I've had best results with film/foil 10nF caps (FKP2 and even better FKS2)

Quote:
Originally Posted by soongsc View Post
I wonder whether new power supply for LM318 is necessary, but amazing things just never stop popping up.
I've listened with the plain PS for three years, it's not 'necessary' but, trust me, the new one it's a big step up

I'm pretty sure that a plain RevC populated with the Ultimate BOM would beat ANY other chipamp (apart My_Evo, obviously... )
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Old 2nd January 2012, 12:18 PM   #3446
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Well, right now I'm putting one channel against the other each trying to beat the other. When your other board becomes available, it will be these against the new one. I think there is potential to be among the best of amps in this wattage category. Just needs some work to get there.
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Last edited by soongsc; 2nd January 2012 at 12:36 PM.
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Old 3rd January 2012, 01:05 PM   #3447
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C4 changed to a 0.68uF X2 cap I had on hand,...
Sorry, typo. It's 0.068uF.
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Old 3rd January 2012, 01:14 PM   #3448
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Quote:
Originally Posted by soongsc View Post
Well, right now I'm putting one channel against the other each trying to beat the other. When your other board becomes available, it will be these against the new one. I think there is potential to be among the best of amps in this wattage category. Just needs some work to get there.
hehe welcome to the club, soongsc. your journey sounds exactly like the one i took many months ago. wait till you get some blackgates in there, then you'll realize how accurate your statement was
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Old 3rd January 2012, 01:51 PM   #3449
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Are BlackGates supposed to be the ultimate solution?
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Old 3rd January 2012, 02:36 PM   #3450
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Are BlackGates supposed to be the ultimate solution?
They give good results at C9, C6 and C11. I've left space for BlackGates at C1 and C2 also in V1.4, but haven't got around to trying them there. I have a few BG Fs coming in from Pocoyo in Indonesia to try out at C1 and C2 - we'll see how it goes, but I expect that it will extinguish that last bit of sibilance and edginess that's there in Rev E without the LF01.
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