ytsestef

Re: GSSL CRC Board from Expat Audio
« Reply #20 on: October 04, 2009, 08:48:36 AM »
(sigh)

You simply must not do this... It will explode.

The whole problem is about bringing AC into the GSSL board... then 'pumping' modulated DC current at 120Hz through the traces.

Therefore the ONLY solution is to move the rectification OFF board, and ONLY bring smooth DC into the GSSL.

Just build it properly.

Trust me.

Keith

I knew it was fishy, that's why I asked... Now I realized what it does. Is it OK if I leave the bridge rectifier on the gssl PSU as well??
Stefanos.


MrShhh

Re: GSSL CRC Board from Expat Audio
« Reply #21 on: October 04, 2009, 08:59:45 AM »
My quick and dirty version:



It got rid of every trace of hum that simply would not budge by trying anything else. It's an excellent mod and saved me hours of fruitless hum chasing.

I left the rectifier on board in place. It makes no difference.





ytsestef

Re: GSSL CRC Board from Expat Audio
« Reply #22 on: October 04, 2009, 09:09:54 AM »
can someone tell us part values? caps/resistors/bridge rect?
Stefanos.

MrShhh

Re: GSSL CRC Board from Expat Audio
« Reply #23 on: October 04, 2009, 09:17:33 AM »
6 * 1000uF (470uF was not enough)
4 * 10r resistors
1 * B380C1500R bridge rect

The B380C1500R is rated to 900v, 1.5a. 350v is more than enough. It was all I had lying around.

Edit: I meant to say also, I get a 2-4dB improvement in ripple reduction by using low ESR caps. There's quite a difference between Panasonic NHG and FC/FM caps.

« Last Edit: October 06, 2009, 05:24:52 AM by MrShhh »

Re: GSSL CRC Board from Expat Audio
« Reply #24 on: October 04, 2009, 09:40:18 AM »
Sure seems severely overdue for a re-design incorporating all the 'improvements'. 
+1
+1
+1
(can I vote more than once? I think they do in Florida...)  :P

The only shortcoming I can think of right now is that the pcb would grow in size beyond the conventional photoresist-pcb-compatible eurocard pcb size.
If the PSU were removed (since no one seems to use it) there'd be quite a bit of room.

ytsestef

Re: GSSL CRC Board from Expat Audio
« Reply #25 on: October 04, 2009, 09:44:58 AM »
6 * 1000uF (470uF was not enough)
4 * 10r resistors
1 * B380C1500R bridge rect

The B380C1500R is rated to 900v, 1.5a. 350v is more than enough. It was all I had lying around.


I have lots of spare 1.5A 50V. Will they do?
I also have only one piece of 2A 400V.

I prefer to use the 1.5A 50V if possible
Stefanos.

Re: GSSL CRC Board from Expat Audio
« Reply #26 on: October 04, 2009, 10:11:06 AM »
Quote
I have lots of spare 1.5A 50V. Will they do?
I would guessed you need at least 240V :)
« Last Edit: October 04, 2009, 10:16:15 AM by warpie »

Re: GSSL CRC Board from Expat Audio
« Reply #27 on: October 04, 2009, 10:15:39 AM »
SSLtech >> is this circuit suitable for other projects as well?
I would assume it is but just wanted to confirm.

I'm thinking of buying a few in the future to combine shipping costs for europe

jdbakker

Re: GSSL CRC Board from Expat Audio
« Reply #28 on: October 04, 2009, 10:20:29 AM »
I have lots of spare 1.5A 50V. Will they do?

Possibly. What is the (AC) output voltage of your transformer?

I would guessed you need at least 240V :)

Why? He's not trying to rectify the mains voltage.

JDB.
[and for a mains-connected rectifier the diode would have to be rated for more than peak mains voltage, ie sqrt(2) * 240V or 340V in the UK]

Kingston

Re: GSSL CRC Board from Expat Audio
« Reply #29 on: October 04, 2009, 10:31:58 AM »
I've been meaning to say this before,

if building a fresh GSSL clone, something like this standard deal works much better: http://www.geocities.com/m_natsume/files/MNATS_PSU.pdf

Save on parts and just skip the crappy 7815/7915 based original filtering completely. You can still leave the 12V regulators in. You'll get noise floor well below -100dBu, only depending on your PSU transformer placement anymore.

I would recommend this instead of "brute force" CRCRC tacked on stages even if upgrading an existing unit, since cost will be similar enough in both cases.


stereokillah

Re: GSSL CRC Board from Expat Audio
« Reply #30 on: October 04, 2009, 10:34:58 AM »
i've tried JLM psu nmats psu, and the winner is CRCRC,

it's just my care
if your neighbour is hunger .. don't give him fish, teach him how fishing ...

Kingston

Re: GSSL CRC Board from Expat Audio
« Reply #31 on: October 04, 2009, 10:37:11 AM »
sounds to me like you did something wrong with those other PSU's if you couldn't get better performance out of them than this CRCRC glue.

7815/7915 are simply not as good as LM317/LM337 based regulators.

[typo edit]
« Last Edit: October 04, 2009, 10:39:39 AM by Kingston »

Rochey

Re: GSSL CRC Board from Expat Audio
« Reply #32 on: October 04, 2009, 10:45:01 AM »
Holy smokes... I take one day out to go paintballing, and come back to this! :)

The new parts are up as placeholders. they exist, but things like user manuals etc aren't ready.

We also only have small batches of parts so far - just in case there were any problems.

Stay tuned, and please register on the shop (http://www.expataudio.com/expatshop).
There's a link there to "register for our mailing list" - put your email address there, and as I release different boards, I'll email the group.

Once everything is released, we'll put a posting in the white market.

/R
Expat Audio Home: http://www.expataudio.com

MartyMart

Re: GSSL CRC Board from Expat Audio
« Reply #33 on: October 04, 2009, 11:05:46 AM »
I must be either lucky or have decent mains here as I have not had any "hum" in my
2 x GSSL's  :-)
Seems like a very easy strip/vero build anyway IMO

MM.
"Success is the ability to go from one failure to another with no loss of enthusiasm"

Rochey

Re: GSSL CRC Board from Expat Audio
« Reply #34 on: October 04, 2009, 11:18:32 AM »
marty, yeah, this one's a real "utility" type board.  ;)
Expat Audio Home: http://www.expataudio.com

MrShhh

Re: GSSL CRC Board from Expat Audio
« Reply #35 on: October 04, 2009, 11:36:52 AM »
i've tried JLM psu nmats psu, and the winner is CRCRC,

it's just my care

Ditto.

I have a 317/337 psu + CRCRC network all on one board. I only use it if nothing else works (changing rectifier/diodes, regs, trafo position, cabling, grounding etc. etc, as well as trying 317/337 psu without CRCRC). It's not usually necessary, but sometimes there is no other choice.

ytsestef

Re: GSSL CRC Board from Expat Audio
« Reply #36 on: October 04, 2009, 12:27:46 PM »
I have lots of spare 1.5A 50V. Will they do?

Possibly. What is the (AC) output voltage of your transformer?

I would guessed you need at least 240V :)

Why? He's not trying to rectify the mains voltage.

JDB.
[and for a mains-connected rectifier the diode would have to be rated for more than peak mains voltage, ie sqrt(2) * 240V or 340V in the UK]

Thanks a lot everyone for your answers. My trafo output is 2x15V (as usual for gssl projects). Basically the 1.5A/50V bridge rectifier is the one that I used in the original GSSL psu, that's why I have many spare parts.
Stefanos.

Rochey

Re: GSSL CRC Board from Expat Audio
« Reply #37 on: October 04, 2009, 02:48:55 PM »


PS: I just had an idea while surfing expataudio.com. Has anyone tried using these sweet "3-pushbutton switches which control relays via microcontroller" pcbs to control turbo on/off  and  bypass?? (should be more tricky because it's not spst switch)

I bet THAT would be really cool looking

That should be easily possible using the following components from Expat Audio

3 Button Controller - http://www.expataudio.com/expatshop/index.php?act=viewProd&productId=6
3 Buttn Cntrl IC - http://www.expataudio.com/expatshop/index.php?act=viewProd&productId=8
Single Ended Relay Board = http://www.expataudio.com/expatshop/index.php?act=viewProd&productId=11

you should be able to control 3 different things with that board, in this case, I suggest
  • Oxford/Aarhus Mode
  • In - > Out Bypass (using the differential relay board)
  • External Sidechain Enable

Expat Audio Home: http://www.expataudio.com

SSLtech

Re: GSSL CRC Board from Expat Audio
« Reply #38 on: October 04, 2009, 03:24:50 PM »
0.5A or higher... 50V or higher... make sure it's the package type called 'WOG' (which is the button-type) and you're golden.

The 3-button controller can be made to do more or less ANYTHING. You can choose from a menu of functions, such as sidechain high-pass/flat, external sidechain, compression on/off, hardwire bypass, turbo mode on/off (Oxford/Aarhus), or pretty much anything else which you can think of. You can even fit more than one board, and have more than three buttons, if you REALLY want to go crazy!  ;D

On the subject of CRC-versus off-board regulation, I've got Lukas's (most excellent, by the way!) GSSL on my test bench at the moment, right next to my test mule. The Expat test mule is actually returning slightly better numbers than Lukas's unit, although the comparison isn't QUITE 'apples-to-apples' since Lukas's unit uses pre-trimmed VCAs, and there are a couple of other things such as different capacitor and IC choices... Also, his unit draws more current due to the number of LEDs being driven, (albeit from a separately-regulated supply...)

But being in the (fairly unique) position that I can make side-by-side measurements, I can indeed confirm that the CRC-equipped GSSL produces BETTER noise-floor results than the externally-regulated version. -Don't ask me to explain it; I don't know the answer just yet, but there's about an 8dB difference in favour of the CRC in this (admittedly NON-scientific) comparison. I can post a video of the two side-by-side if anyone really wishes.

To date I've probably built about five GSSLs, including the 'Ultimate', and in addition I've trouble-shot some build problems for others (BR -Gil, Michael Pritchard -where's he been lately by the way?, and several others) as well as rescued one abandoned build, and currently taken over custodianship of Lukas's monster build... I've had varying degrees of hum problems on most of them, and in the end I've tried the following solutions:

*Adding lots of 'rail-stiffening' smoothing capacitance all over the board... Don't bother, the problem is a current-flow related modulation, which no amount of 'bolting on' of capacitance will ever solve.
*Trace cutting in various locations, with accompanying re-wiring of the ground path
*Several grounding approaches and case ground locations
*Externally regulated supply

So far the only one of the above which has worked reliably is the externally regulated supply... but then I tried the CRC and got a similar improvement, for MUCH less 'bother'. It meant the builder can still use the same tried-and-tested board, ripple is -absolutely- gone, and I personally cannot detect ANY residual hum with the CRC.

I'll double-check the test with the CRC in the expat test-mule on Monday, and compare it to Lukas' externally-regulated super-GSSL, but I recall the CRC-equipped version being quieter, for whatever reason.

Suffice to say, my continuing investigations into the GSSL as a platform (I love these things!!!) means that I'm ALWAYS looking for ways to improve them. So far I've looked into several OTHER ways to improve them which haven't panned out, and the only things which I've ever 'brought to people's attention are the things which work... and work WELL.

The bypass wiring reconfiguration to reduce distortion in bypass is one example of how I'm STILL looking for ways to improve the sound of these things. (If you haven't done this yet, TRY IT... it's free, and it's demonstrably cleaner in bypass), as well as the ultimate/turbo and VU meter GR driver developments.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Kingston

Re: GSSL CRC Board from Expat Audio
« Reply #39 on: October 04, 2009, 04:32:19 PM »
Keith,

I don't know how you're measuring the noise floor there, but a pretty standard LM317/LM337 externally regulated version here has such a low noise the PSU no longer has any effect on the board performance. I can only measure the noise floor of the chips anymore, and actually, I'm not absolutely sure how much of the noise floor is from the AD converter (looking at RMAA images). Ideal really.

And yes, the original GSSL board has some issues with modulation of the rails (ground?). Doesn't seems like there's any other good solutions than just feed very clean DC for the board in the first place. The layout renders the design incapable of removing this crud on-board by itself and just sends it forward to the chips.
« Last Edit: October 04, 2009, 04:34:40 PM by Kingston »


 

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