Carlos - nice to see you again!
Chris - I use USB SB Live! 24 bit external, in 16bit/96kHz mode. It is more about tuning the setup, optimal input/output levels and SW.
For all Toshiba 2SC5200/2SA1943 users: please visit my symasym evaluation page at
http://web.telecom.cz/macura/symasym.html
to see component value modifications for these transistors. These values assure no oscillations, nice step response and measurements shown.
Chris - I use USB SB Live! 24 bit external, in 16bit/96kHz mode. It is more about tuning the setup, optimal input/output levels and SW.
For all Toshiba 2SC5200/2SA1943 users: please visit my symasym evaluation page at
http://web.telecom.cz/macura/symasym.html
to see component value modifications for these transistors. These values assure no oscillations, nice step response and measurements shown.
Excellent results Pavel!
Now I have this strange feeling that I´ll have to make a second set of boards.
I just found that a local distributor has those Toshibas á 2.15€.
Pavel, weekend is coming over, after all this measuring you should take few Becherovkas sit back and listen😉
Now I have this strange feeling that I´ll have to make a second set of boards.
I just found that a local distributor has those Toshibas á 2.15€.
Pavel, weekend is coming over, after all this measuring you should take few Becherovkas sit back and listen😉
Good work Pavel, I can't see the time to try your values.
I see that except that famous 22pF you have changed 330pF to 220pF and you have BC547C at the input These changes, have to do with stability or something else? Are they mandatory?
We are waiting for your subjective acoustic evaluation.🙂
I see that except that famous 22pF you have changed 330pF to 220pF and you have BC547C at the input These changes, have to do with stability or something else? Are they mandatory?
We are waiting for your subjective acoustic evaluation.🙂
Re: Excellent, excellent work, Herr Bittner !
Harummph, I resemble that remark. 🙂 So who's gonna make some boards available to help us etching challenged folks who will otherwise continue making spider habitats? I'm in for a couple.
Sheldon
PMA said:
Harummph, I resemble that remark. 🙂 So who's gonna make some boards available to help us etching challenged folks who will otherwise continue making spider habitats? I'm in for a couple.
Sheldon
Re: Re: Excellent, excellent work, Herr Bittner !
I'd like to second this request. I've enjoyed watching this thread (except for a couple of exchanges) and would like to commend all the contibutors for their efforts.
Sheldon said:
I'd like to second this request. I've enjoyed watching this thread (except for a couple of exchanges) and would like to commend all the contibutors for their efforts.
Hmm, i think if we start a groupbuy, i should go doublesided as the PCBs would be made industrial anyway. I would keep the basic arrangement as it is proven and only improve some known problems. (Power grounding)
What do you think ?
Mike
What do you think ?
Mike
dtrif said:
Dimitris,
only that famous 22pF must be necessarily decreased to 3.3pF.
330pF to 220pF just for better feeling and less VAS load, you overlooked 0R22 changed to 0R15 (5W), for a little bit better linearity and better efficiency of output stage (I have large heatsink 😉)
Yes, I hope in weekend listening tests.
MikeB said:
I agree, I also use double sidded, the upper layer not by wire jumpers, but traces wider and holes with bigger drill diameter for these jumpers.
Double sided have a great advantage - soldering is much easier and eventual repair (desoldering) will not destroy the PCB.
You should prepare the PCB for production.
Maybe think about diode/resistor rail protection (against elcap explosion)
I made some more THD measurements, now into 4 Ohms. I can say that the amp performs best in the class A. In class AB it works better for higher bias. If you have large heatsinks (and no oscillations 😉), Iq about 170 mA seems to be nice for me. I checked by my brutal FM testing method, when spectrum on amps input covers the whole audio band. But do not want to bother anymore, now is the time for listening tests.
Hello all,
I have completed the 2nd symasym channel on the heatsink. The behaviour has been absolutely same as for the 1st channel. So I reduced the famous Cf etc. etc. and now is the time to assemble the Fischer box, make internal PSU and signal wiring and start to listen.
(I'll tell you a small secret - Michael has his first results with Toshibas! 😉 )
Pavel
I have completed the 2nd symasym channel on the heatsink. The behaviour has been absolutely same as for the 1st channel. So I reduced the famous Cf etc. etc. and now is the time to assemble the Fischer box, make internal PSU and signal wiring and start to listen.
(I'll tell you a small secret - Michael has his first results with Toshibas! 😉 )
Pavel
jarkaa said:
Or you can get them for less than half that price if you buy at least ten each from Profusion.
www.profusionplc.com
No charge for freight, and AFAIK they get them directly from Toshiba so you don't risk getting fakes.
Hi !
Yesterday i replaced the MJLs by the Toshibas, and as expected symasym oscillated...
Because of lack of suitable caps, i only reduced the cfb from 22pf to 10pf, but oscillation has gone !
First listening showed slightly improved sound, a bit more natural/softer and balanced, not much, but enough to recognize. Now, i don't know if it is the Toshibas or the changed cap ?
At least the Toshibas are good sounding devices, but have less thermal stability than the MJLs, but not problematic. I can recommend them !
Dimitris, changing that cap will make your amps definitely sing again !
To the others, try to get "O"-grade Toshibas, these are the high beta ones, but typically you have no way to find out when ordering... 🙁
more later,
Mike
Yesterday i replaced the MJLs by the Toshibas, and as expected symasym oscillated...
Because of lack of suitable caps, i only reduced the cfb from 22pf to 10pf, but oscillation has gone !
First listening showed slightly improved sound, a bit more natural/softer and balanced, not much, but enough to recognize. Now, i don't know if it is the Toshibas or the changed cap ?
At least the Toshibas are good sounding devices, but have less thermal stability than the MJLs, but not problematic. I can recommend them !
Dimitris, changing that cap will make your amps definitely sing again !
To the others, try to get "O"-grade Toshibas, these are the high beta ones, but typically you have no way to find out when ordering... 🙁
more later,
Mike
Michael,
probably lower Cob of Toshibas together with reduced C(feedback) ?
I am impatient to listen! /this afternoon/ 😉
Pavel
probably lower Cob of Toshibas together with reduced C(feedback) ?
I am impatient to listen! /this afternoon/ 😉
Pavel
jarkaa said:
That would be the next step ! Sadly my PCB starts to degrade, peeling of pads...
I have the feeling that the MJLs and Toshibas are very different, but can't tell yet which is "better". At least the Toshibas are cheaper.
PMA said:
I'm sure you will love it !
Mike
Bocka, i always observed more stable vbe for onsemi's compared to others. That's why i do not use onsemis for vbe multiplier... 😀
This seems to be a discipline where onsemi really rocks.
With the MJLs i was not even able to measure the bias variations, with the Toshibas bias increased with heating up ~30%.
Spoerle is a not a shop for normal buyers, only for companys. AFAIK...
Mike
This seems to be a discipline where onsemi really rocks.
With the MJLs i was not even able to measure the bias variations, with the Toshibas bias increased with heating up ~30%.
Spoerle is a not a shop for normal buyers, only for companys. AFAIK...
Mike
jarkaa said:
Jarno, if you have some time left, you could try out, i had verified stability with 10pF for the MJLs, it's a simple change !
(I have to pull out the Toshibas again for this listeningtest)
Mike