G&W 2006TX PreAmp upgrade • Rice Inside •

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#42
Ok here I'm back with some other point to upgrade : caps!
It seems already that some MKP printed on PCB with a huge room around are fitted with smaller Philips MKC. It seems less nice for audio.
These are the blue squares beside the MKT.
An externally hosted image should be here but it was not working when we last tested it.

It seems that the PCB is ready for bigger caps!

Any advice? I've read that MKP is the only one in audio path... do you think my MKC are in audio path and deserve to be replace by MKP?
Are these ones OK and wich value as it jumps from 1.5µF to 10µF?
http://www.riviera-acoustics.com/catalog/default.php?cPath=50


Thanks for havin' a look here 😉
 
#43
Not sure what MKP and MKT are. Is one polyester and the other polypropylene?

I changed some 1uF/63v polyester (green box cap) for 1uF polypropylene (LCR brand from Maplin) in my preamp. These are used for DC blocking. The sound did improve. Well worth doing if they're "only" polyester and in the signal path.

Simon
 
#44
ehehehehe, I think Tsinghua university G&W has made some amazing amps out there, and their performance / price ratio is really high. glad someone in this forum take notice of this brand and write an review on it, great pic too, keep up the great work!
 
#49
CEKPETHO


There are a lot of "interesting" Russian military surplus capacitors, including PIO, Teflon, as well as more common mylar, and poly)

Sometimes the seller's description gives no indication of the cap's specifications other than simply capacitance and working voltage.

I've been doing a bit of research, (this is still a work in progress) and attempting to figure out this mysterious
"Sekret Kommie Kaps Kode" and I have some preliminary results:

(Note, some of the letter suffixes use Cyrillic letters, I can't print them here, I'll use the English equivalent for now)

K15-4 Ceramic HV "doorknobs"
K15-5 Ceramic HV Disc

K31 Silver Mica "kidney bean" style cap

K40P-2B Paper in Oil, 5% tol.
K40U-9V Paper In Oil , Silver body, 10% tol.

K41-1A PIO, High Voltage "Pulse" caps

K42U-2 PIO, green painted body (K75 are better)

K50 Aluminum Electrrolytic

K71-7V Polystyrol "High Tolerance" 1% or 2% tol.

K72P-6 Teflon Dielectric 5% tol. (see example below)

K73-14 PETP High Voltage
K73-15 PETP / Dry Mylar
K73-16 PETP / Dry mylar
K73P-4 "tub " style AC capacitors (may be paper or mylar, still TBD)

K74 HV caps

K75-10 PIO, Green body (these are the prime quality PIO)
K75-15 PIO, High Voltage "tub"
K75-17 PIO High Voltage "tub"
K75-24 PIO Green body tubular (see example below)
K75-28 PIO High Voltage "tub"

BMT-2 Paper In Oil

FGT High Voltage Teflon Dielectric, Ceramic body (almost beer can size)

KBG PIO (no, this isn't the KGB, they're a different entity altogether)

KBI HV "doorknob" RF / Transmitting cap

KSO Silver-Mica "precision" caps

MBG Paper-Aluminum "tub" AC caps

The letters OTK are initials for "Otdiel Technicheskovo Kontrolya" or Bureau of Technical Control
which indicates that special mil-spec or industrial testing standards are applied. In other words, "Top Shelf"

CEKPETHO

Oh, yeah, this means "Secret" in Russian, and in Cyrillic-looking letters
Click to expand...
 
#53
The Classic is really lacking bass, I kept the G&W and sold to a friend the Classic for the price I've bought it brand new, 250€! Anyway, it's a very good amp, very dynamic and detailled in mids/highs, just no bass! Excellent for acoustics or voices.
The G&W in fact is very imprssive in bass, I'll try to mod it to make it better 😉
 
#58
muka said:
Please note that the NE5532 is not used as a pre-amp in GW2006. It is used in the power regulator to provide feedback to the regulator IC. No need to change the NE5532.
Click to expand...


Thanks for info, yes the PSU is like what's have been said before.
It's almost like this one:
http://www.diyaudio.com/forums/showthread.php?postid=1202138#post1202138

But I have questions:
•1• Is there no gain at all in upgrading this opamp? I mean I have already in hands LM4562 and AD8599, why I may set back the NE or fit the AD? There should be a spec that's better for the PSU purpose, no?
•2• The caps before the regs, 2200µF/35V Nichicon VR are not bypassed like in the drawing shown before, I've added 100nF X7R under the 2200µF. Is it right? I've seen and done this in all my PSU design before, e.g. my CDP. Is it OK?
•3• In this design, is it still usefull to load the regs using a resistor?
•4• The 7815 and 7915... are from diffrent manufacturers, the 7815 from ON, the 7915 form National... may I fit the same brand/serie? If yes, wich one?
•5• The big output caps are Slimic, but I feel uncomfortable with the look they have, any mean to check if they're fake? At least they were badly handled and are from an old stock. If needed I'll change them.
•6• The Slimic 470µF are bypassed by 150nF MKT. What are these small yellow plastic cans? Is this good?
•7• Is this will deserve low noise regulator boards, e.g. SCal Regs or AudioCom or TentLabs stuff?

This deserves many answers, thanks for having a look 😉
Matthieu
 
#59
Well, no aswer but I've still worked on...

Today I've upgraded my amp aslo, making things... worst :'(
First a AD8599 does not work anymore : big noises in speakers, AD becomes hot as hell... LM4562 works fine. Strange.
I've loaded the pre-amp regulators with 1K as I've been told, changed MKC Philips for russian K75-24 PIOs, bypassed pre-regulators Nichicon VR 2200µF with 100nF X7R.
After all this the sound has lost bass, have more details but is harsh. Loud as before is now too loud :'(
Maybe the PIOs should be burned in for dozens of hours...
I'll have a new hear at this next weekend.

I still wonder if loading the regulators is good as opamp monitors the 15V...
 
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