Explendid amplifier designed by Michael Bittner, our MikeB

[PMA]

There is no thermal runaway. I checked it. Biased the amp at 1A, 360 mA, 200mA, .... down to 6 mA. Finally I choosed 150mA, for distortion reason. It is quite high-biased class AB now.

The only care must be taken for stability. Lowered Cf solves it, Michael recommends 10pF for Toshibas, I recommend 3.3pF for high stability margin. Let's get in the middle, some 6.8pF.

 

[MikeB]

Let's get in the middle, some 6.8pF.

😀

I simply had no smaller cap than 10pF, it just already did the job and i wanted to listen !

ilimzn, there is no runaway, i have quite small heatsinks and amp cooled down easily after turning down the volume.

Mike

 

[dx.master]

PMA und MikeB,

I simply had no smaller cap than 10pF, it just already did the job and i wanted to listen !

ilimzn, there is no runaway, i have quite small heatsinks and amp cooled down easily after turning down the volume.

Mike

Please show use some new Pictures of your amps.

My PCB are not ready until now and i miss the MJL3281A ONS, it will arrive at 03.12.2005 from Reichelt in Germany.

Today i will finish an old Elektro Project Mini-Crescendo, i bought the 2SJ50/2SK135 Mosfet und some C's and R's somtimes ago over Ebay.

 

[sajti]

There is no thermal runaway. I checked it. Biased the amp at 1A, 360 mA, 200mA, .... down to 6 mA. Finally I choosed 150mA, for distortion reason. It is quite high-biased class AB now.

It not necessary thermal runaway, just some delay in the compensation. My experience, that not easy to make perfectly compensated bias system. In my version I use two transistor bias system. It easy to adjust, just add/remove some pads between the heatsink and one of the sensor.
The double transistor version has lower internal impedance too.

sajti

 

[destroyer X]

My Mother Board was damaged...i was "out of the air", now new mother board and things

running well again.

Yes Pavel, those musics are very nice.... that period of time, we had the best....Bossa Nova......

Corcovado
Copacabana

I miss my home town...there are moments that i feel the need to jump over a fast Motorcicle an open the throttle all the way up!...but airplane is faster.hehe

Michael, will be ugly, but you can put 2 capacitors in series to test.

As i can see, everybody happy....ahahahahha!...i am too!

Amplifier "Warranteed"....and now with Pavel Macura, experienced Enginner signature!

hehe..... life is beautifull...isnt'it guys?

regards,

Carlos

 

[MikeB]

Hmm, this silence... 😕 ... ... Ah, all busy listening symasym... 😀

harhar,
Mike

 

[destroyer X]

If Symassym was a grenade!...hehe...it has pin now!

Your capacitors replace the pin into the "grenade".

hehe


Goooooooood!


Carlos

 

[PMA]

Hello guys,

not a silence, but hard work! 😀

I am preparing a long review, I was listening many hours, and now added some spectral measurements.

Preliminary info - I can say that the amplifier is very good. Michael, you only might like to strenghten power return PCB traces from those 1000uF capacitors, if you planned to make a final PCB.

 

[MikeB]

Hi Pavel, yes, these traces are the weakness of actual layout, should be easy to solve with a doublesided version ?

I am really impatient about reading your evaluation !

Mike

 

[still4given]

OK, you guys have sucked me in. Now I'm waiting with anticipation as well.

I've got a new thread to follow.

Thanks, Terry

 

[MikeB]

Hi Terry, you're welcome !

Mike

 

[PMA]

Hi all,

here is my symasym review:

http://web.telecom.cz/macura/review.htm

 

[anatech]

Hi Pavel,
A very good review of this amp. You have contributed much time and work to this project. It looks like an excellent kit to offer.

I'm dying to get mine together. Now I am more excited.

Thanks, Chris

 

[PMA]

Chris,

it has been a pleasure for me to participate in this project.

Pavel

 

[MikeB]

Hi Pavel !

Thanks for the great review and the effort to evaluate the symasym ! 🙂
It was very interesting to read, and is very clearly structured.
Pavel, it was a pleasure working with you !

But what is a "harpsichord" ?

Mike

 

[PMA]

Harpsichord is a clavecin or clavinet, preceder of piano, with "string" sound, volume of tone cannot be controlled by player.

 

[MikeB]

Ah, this one, i was not familiar with that name !

Mike

 

[destroyer X]

Hey Mike!...want some sausage to the party

Because you heart will feel good...evaluation will be wonderfull, and you will be very happy.

Sausage toasted...hummm, das ist zier gut!...Ich liebe dich

Aufwiederlehsen.

regards,

Carlos

 

[jam]

Carlos,

Just for you............a diy project..............

http://visualrecipes.com/recipe-details/recipe_id/55/Spicy-Sausage-and-Bacon-with-Curry-Couscous/

Regards,
Jam 😀

 

[dtrif]

Everything seems ok with symasym

Changed 22pF to 10 pF today (I had no smaller caps handy, at least two with the same value). I listened to it, but not for long. Everything seems ok now.😉
Pavel very good review of symasym. And nice work in total.