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The Stax SRM-001 mod thread - Page 27

post #391 of 401
7/20/11 at 8:02pm
Thread Starter 

1642 draws 1.8mA, while the 8599 in SFC is much higher than that (therefore requiring shorting the resistors in the SFC, otherwise voltages at chip will be too low). I'd say install the 1642 first, see what kind of voltage you are getting at the supply pins. If the supply voltage is too low, parallel something to the resistors until the proper voltage is present at the supply pins ( +/-10~12v ). 

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post #392 of 401
7/20/11 at 11:05pm
Quote:
Originally Posted by Archwn View Post

I have discussed with him and I might try this soon. So the amp's roll off then not the phone's? Wikiphonia said the other way round. confused.gif


The SFC++ sounds very similar to the SR-003 with an SRM-1 Mk2 Pro or an eXStatA amp, and it's definitely not as rolled off as the stock SR-001 Mk2 (or Mk1 which was worse).  It's kinda like a Baby O2, not bright and not dark, and not rolled off.  I don't recall exactly what caps audiocats used, but I seem to recall it was a combination of blackgates and auricaps.  The opamp I think was an AD8599 or something like that.  I'd have to look way back in this thread.

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post #393 of 401
7/20/11 at 11:17pm

^AD8599 it is.

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post #394 of 401
7/22/11 at 1:56pm
Quote:
Originally Posted by AudioCats View Post

1642 draws 1.8mA, while the 8599 in SFC is much higher than that (therefore requiring shorting the resistors in the SFC, otherwise voltages at chip will be too low). I'd say install the 1642 first, see what kind of voltage you are getting at the supply pins. If the supply voltage is too low, parallel something to the resistors until the proper voltage is present at the supply pins ( +/-10~12v ). 



Thanks Audiocats

 

Sorry for noob question but, to be clear in my mind:

- I would parallel separate resistors across both R34 & R35 to reduce the voltage (if required), but what would I do with R33 - leave it as is or short it out?

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post #395 of 401
7/22/11 at 7:40pm
Thread Starter 

hmm, I forgot about the R33. try reduce it to the same degree as you will on R34/35  (parallel the same value).

 

when something is paralleled to the resistors, the final resistance is lower, so the voltage drop across it will be lowered, raising the available voltage at the chip's supply pin.

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post #396 of 401
9/30/11 at 2:17pm

Hi AudioCats

At last I have solved the problem of my Stax sr-001 MKII; I sent it to Joynetcafe (Japan) and Stax changed the Earspeakers unit under warranty. Now, it sounds good but I want to modify it as SuperFatCat ( I have put the PCB in a new case, so there aren’t problems of space); however, I’ve some questions:

  1. AD 8599; how can I mount it on the PCB? Do I need an adaptor? And the directions of the Pins? What is that yellow cap in the photo (post four)?

N.B. I use four UltraFire 2400 mA 3,7V  as external power supply

 

2) “add four fast electrolytics directly from the opamps’ VCC/Vdd pins to the round” (post 48). Are they necessary? Have you a photo of the mod?

3) “H) Add a good electrolytic cap between ground and DC input + (after the switch)”. Its value?

4) C1: What between BC MKP 0,12uF 63V and Epcos 0,15uF 630V? Or another better brand?

5) C6-C7: What between BC MKP 0,01uF 630V and Relcap 0,01uF 600V? Or another better brand?

6) Resistors. May I change them? Or can I leave the original resistors?

7) C13-14-15-16. How can I replace them?

8) I think to use Elna Silmic II instead of Black Gate for the other caps. What do you think?

9) Q15. Really Do I need an heatsink?

Thank you very much

Best Regards

Leandro

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post #397 of 401
10/1/11 at 12:39pm
Thread Starter 
Quote:
Originally Posted by ecodoppler View Post

  1. AD 8599; how can I mount it on the PCB? Do I need an adaptor? And the directions of the Pins? What is that yellow cap in the photo (post four)?

N.B. I use four UltraFire 2400 mA 3,7V  as external power supply

 

2) “add four fast electrolytics directly from the opamps’ VCC/Vdd pins to the round” (post 48). Are they necessary? Have you a photo of the mod?

3) “H) Add a good electrolytic cap between ground and DC input + (after the switch)”. Its value?

4) C1: What between BC MKP 0,12uF 63V and Epcos 0,15uF 630V? Or another better brand?

5) C6-C7: What between BC MKP 0,01uF 630V and Relcap 0,01uF 600V? Or another better brand?

6) Resistors. May I change them? Or can I leave the original resistors?

7) C13-14-15-16. How can I replace them?

8) I think to use Elna Silmic II instead of Black Gate for the other caps. What do you think?

9) Q15. Really Do I need an heatsink?

1) there are already traces and pads on the board for dual opamp. The 001 might be originally designed with soic dual opamp in mind, then somehow changed to the dip straight 8 pin opamps. there are dot marks on the board showing orientation.

 

2) cap quality affects the sound quite a bit.

 

3) This one is not super critical, the sound difference is mostly in bass impact, you can skip it if there is no room. 470uf/6.3V will work. The speed is more important than the capacitance.

 

4) C1 is the input by-pass, any polyprop will work, as loong as it fits.

 

5) C6 is the hi-voltage rail reservoir, use the largest value (that still fits). C6/C7: use boutique, as fancy as possible, but very few of them will fit, so the BC and soniccap might be your only choices.

 

6)leave the resistors along, not enough sonic gain.

 

7) there is no upgrade for C13/14/15/16.

 

8) silmic will work, but not as good a blackgates. But BGNX is pretty much unavailable, so...

 

9) USE A  HEAT SINK on Q15! or it can get cooked.

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post #398 of 401
10/16/11 at 2:07pm

AudioCats

thank you for your reply. What do you think about the use of Ampohm Paper in Oil Aluminium Foil 0,01 uF 630v in C7-C8? I don't have problem of space, given that I'll put the amplifier in a new case.

Thank you

Regards

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post #399 of 401
11/21/11 at 2:00pm

Hi

I have modified the Stax SRM 001 as follows:

C1>>> Solen MKP-FC

C2, C27 and C28>>> Elna Silmic II

C3>>> Elna Silmic II

C17 and C18>>>Nichicon Muse

Elna Silmic II 470uF 50 V between DC input and ground

C7 and C8>> Amphon PF-XAL-AL 0,01 uF 630V

I left the original NJM062L opamps for the moment.

The sound is simply astonishing: more, more detail and trasparency without lose the touch of warm of the original amplifier. Obviuously, the new caps need break-in but even so the sound is great.

I use twisted pair Teflon/99,99% pure Silves IC. AudioCats, do you believe I have to make quad-braid Teflon/Silver IC?

 

DSCF3481.JPGThank youDSCF3477.JPG

 

 

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post #400 of 401
3/18/12 at 2:09am

Can someone help me finding - BC components, MKP420 series, 0.011uF/630v?

I have installed Panasonics on C7, C8, but the sound is not bright enough for my taste.

Digikey is selling minimum quantity of 1000pcs !!

 

Thank you in advance!

Kiril

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post #401 of 401
5/20/12 at 6:57pm

Incredible info here! Thanks for this thread!  Mine will arrive soon so looks like I need to do some reading


Edited by nick n - 5/21/12 at 4:16am
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