Symasym - Roender Style

[MikeB]

2sk170 are not very commonly available here, so what can you recommend me to use in ROENDES schematics (As I think this is the most advanced amp schematic available for diy Thermaltrak use...)

Regards,
Markus

It shouldn't be a problem to use 2n5551 or bc550c or mpsa18 instead of sk170 (beware of different pinouts!) But you should add ~22-33ohm emitter resistors to compensate for increased gain.

Mike

 

[weissi]

thats what I'm doing now to get z-transform equations into my head

 

[roender]

After some scoped measurements I came to conclusion that outputs of voltage regulators must be decoupled to ground with 0.1uF.
The 10kh square wave 30V output is just perfect, sr=27V/us

 

[-_nando-_]

27v/us is just great !

 

[MikeB]

27v/us is just great !

 

[-_nando-_]

Isn't that Slew Rate?

 

[MikeB]

Yes it is, but not a terrific number... A number where symasym was not really outstanding. But, just a number...

Mike

 

[-_nando-_]

Original Symasym is 20v/s, also great. I think that numbers above 15v/us are good, because of the opamps that I know, like an OPA134 series are 20v/us, and this is a "premium" opamp, others have much less slew rate, this is my "reference".

 

[roender]

The compensation method used in symasym (lag) is the limiting factor of SR. Anything over 25V/us for 100W amp is more than enough

 

[thanh]

Hi All !
News is very intersting.!

roender! How is current through Q19 and Q20? and power disspation ? I intent to use 220ohms for R6 but I afraid that 2N5551 will be destroyed. I used a bigger value, 330ohms but perhaps oscillation appears. I must use a capacitor accross C-B Q19 Q20.

 

[roender]

The CFP drivers Q19/20 loaded with 220ohm has Iq 2.5mA. No power dissipation problem here.
The 70-75mA total drivers current will make this stage work in pure class A at any output power. The CFP has no high order harmonics in this case.
Lag VAS compensation has the same function as a BC capacitor connected at Q19/20

 

[thanh]

Thanks roender! Orcad said that the current is 4mA, p~ 4x35V=140mW . Perhaps I will try to do in real circuit

 

[Khron]

Greetings...

Mr Roender, i've sent you an email through diyaudio a few days ago, i hope you've received it...

 

[Triodas]

PCB Layout

Hello Roender, have you some PCB layout finished?
Can you attach it. I like your design very much and would like to assemble it. Thanks.

 

[atiq19]

Symasym Roender Style Updated Schematic

Roender,

Can you please direct me to a final revision of your symasym?

I found quite a few but couldn't decide which one is most wanted!

Cheers.

Atiq

 

[sparkle]

Roender,
congratulations.... will you publish the boards for this nice amplifier...??

regards
sunny

 

[gmphadte]

I doubt, but I hope I am wrong.

Gajanan Phadte

 

[roender]

This amp is dead in my point of view. It sound like symasym ...
I have another amp on my test desk, a single stage amplifier, which is a class over symasym. I'll promise you that this one will be a public project.

 

[sparkle]

it is a shame - since it is a nice idea of using those output transistors......also i like the rest of the schematic

can You at least start the thread for that new amp You have on the test board so that i can find it when it is on the forum....or maybe the name for the amp that will appear in the thread name or something....
single stage - wow!
this will be interesting
any hints?

 

[roender]

It will be named RMI-FC100 and will have folded cascode "VAS" and the same output stage as symasym-roender style but with more output devices