CCS-MOD for Stax SRM-600
Aug 31, 2020 at 1:39 PM Thread Starter Post #1 of 14

jsts

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My photoreport about creation and installation of CCS-MOD board for SRM-600. The board has an original design to use the existing mounts on the main (mother) amplifier board.

I would like to once again say my most heartfelt thanks to Dr. Kevin Gilmore, Mr. J. Lin, Mr. Mjölnir aka spritzer and all people who inspired with their experience and passion.



First, I read the forum for a long time and make sketches in the graphic editor:

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Then I studied P-CAD 2006 SP2 at the basic level and arranged the board:

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At the same time, I prepared a brief statement of work and buy the necessary details:

- board color and mask - blue
- number of layers - two (top and bottom)
- that on the layers:
.top layer - silk, pads (handmade soldering)
.bottom layer - electric tracks
- copper
- metallized soldering holes
- B+ power track = 350V = width 4mm
- pin tracks YEL, GRN, WHT, RED = width 2mm
- other tracks = width 1mm
- using Hefring Slab font for symbols and text
- because the board is irregularly shaped, need a small rounding of all corners, both external and internal
- board components
.Q1M-Q4M - IXCP10M90S TO-220-3 - Current and Power Monitors and Controllers 900V 1-100mA - https://mouser.com/ProductDetail/747-IXCP10M90S
.Q5M-Q8M - DN2540N3-G - MOSFET 400V 25Ohm - https://mouser.com/ProductDetail/689-DN2540N3-G
.H01M-H04M - RAD-DY-KY/3 - Radiators - https://www.tme.eu/en/details/rad-dy-ky_3/radiators/stonecold/
.TVR5M-TVR8M - 3329H-1-201LF - Adjustable Resistors - 1/4INRND 200 OHM through hole 10% 0.5WATTS - https://mouser.com/ProductDetail/652-3329H-1-201LF
.100, 250, 1K - CMF60100R00BHEB70 - Metal film resistors - https://mouser.com/ProductDetail/71-CMF60100R00BHEB70
.B+, YEL, GRN, WHT, RED - pairing contacts with the main board
- resistors are mounted vertically on the board to save space
- 2mm (8 pcs.) metalized holes are required for fixing radiators
- holes for natural convection of radiators (5mm) 16 pcs.
- fixing screw holes (5mm) 3 pcs.
- Screws and washers M3 for transistors - black!
- Thermo-Insulators for transistors - black! - Bergquist SP1200-0.009-00-1212 https://mouser.com/ProductDetail/Bergquist-Company/SP1200-0009-00-1212?qs=N2Tevpb%2BvobHrB52MpExug==
- Screwed spacer sleeve (Refinement required!) M3; 25mm; Ext.thread: M3; brass 215X25 DREMEC https://www.tme.eu/en/details/tfm-m3x25_dr215/metal-spacers/dremec/215x25/ 3 pcs.


I give the board to manufacturing. The result:

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Perfect. Soldering the parts:

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Aug 31, 2020 at 1:44 PM Post #2 of 14

jsts

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Good. First fitting and Installing the board:

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Aug 31, 2020 at 1:48 PM Post #3 of 14

jsts

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Mission accomplished :) Temperature on heatsinks about 63C - that OK.

DSC03736.JPG


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Sep 2, 2020 at 1:07 AM Post #4 of 14

Mach3

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That is bloody marvellous. I still can't understand why Stax can't release the amp like this from the factory.
 
Sep 2, 2020 at 3:42 AM Post #5 of 14

padam

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That is bloody marvellous. I still can't understand why Stax can't release the amp like this from the factory.
Pretty simple, they are probably running out of CCS parts and HV transistors. The three new amps they came up with (SRM-T8000, SRM-700T, SRM-700S) all switched to current production parts or tubes where they have a big enough stock for mass production (in case of ECC99 tubes, they have acquired enough stock to produce 600 pieces)

I wouldn't expect them to "max out" a cheaper amp, but for that price the SRM-T8000 should have been better to justify its cost.
 
Sep 3, 2020 at 6:26 AM Post #7 of 14

KDS315

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Superb work! Congratulations, excellently executed! Hats up to your style, even mentioning the inventors - that's rare these days....
 
Nov 28, 2020 at 11:12 PM Post #8 of 14

dpaws

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Beautiful work indeed and my compliments for an amp that's as beautiful inside as it is outside.

I understand that the SRM600 Ltd used different tubes, but is the same CCS modification applicable to the Ltd version too with the same acoustic improvements to be had? If so, does the same board work maybe with different component values? Many thanks
 
Nov 29, 2020 at 5:39 AM Post #9 of 14

KDS315

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The SRM600 LTD used ECC99 tubes made by JJ Electronic, Slovakia (ex "Tesla") "for the first time" as STAX mentioned in their ad announcing the SRM-600 Ltd. So the CCS mod fits perfectly. I have a SRM-T1 (CCS/ECC99) mod with "Gold" ECC99 tubes from JJ which sounds excellent with them!
 
Nov 29, 2020 at 4:55 PM Post #11 of 14

KDS315

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Bass is dry and fast, no complains from my side (listening with Lambda Nova Signature), better than before the mod. CCS mod leads to a sound a bit closer to Transistors, yet has the way better sounding "clipping" sound for loud impulses....if that helps you
 
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Dec 1, 2020 at 3:18 PM Post #13 of 14

jsts

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In short, yes, the same CCS modification applicable to the SRM-600 too with the same (or a little better) acoustic improvements.

For a more detailed study you will find it useful to refer to the article "Improving the Stax SRM-T1 Electrostatic Headphone Amplifier" by James Lin in audioxpress.com Magazine (July 2017)

and

Prof-X Audio Blog http://blog.prof-x.de/2019/01/26/stax-vacuum-tube-driver-teil-3-output-stage-mod/ (in German)


Briefly: ccs-mod on SRM-600 - improvements are heard clearly. Trebles became more detailed, medium are the same, bass became are more dense and textured.
 
Dec 1, 2020 at 3:22 PM Post #14 of 14

dpaws

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In short, yes, the same CCS modification applicable to the SRM-600 too with the same (or a little better) acoustic improvements.

Briefly: ccs-mod on SRM-600 - improvements are heard clearly. Trebles became more detailed, medium are the same, bass became are more dense and textured.

You're very kind, and thank you for the links :thumbsup:
 

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