diyAudio (
-   Group Buys (
-   -   TO-3 SYMASYM (

Rudi_Ratlos 4th January 2013 03:50 PM

3 Attachment(s)
Gentlemen, find attached two images showing how to wire up a SYMASYM amplifier.

The 1st picture shows a typical stereo-configuration (same as I have built).
The 2nd picture shows a what I call "Dual-Mono" configuration (same as Junie did).

The Soft-Start PCB is only needed, if you go for the "Dual-Mono" configuration and the combined power
of the 2 transformers is rated at approx. 500VA.

Please keep these pictures in your mind, when you order PCBs.

Best regards - Rudi_Ratlos

P.S. I will of course open a new round of group-buy, if there is demand for it.

evette 4th January 2013 04:45 PM

Please put me down for 6 of each pcb. Thanks Evette

Grobalt 5th January 2013 07:10 PM

Will this new round be compatible with posting #626 ?

rephil 7th January 2013 12:34 PM

Hi Rudi_Ratlos,

If you offer also something else (like transistors NJW0281-NJW0302 ?), I am interested too. Let me know. Thank you.

As I have many TIP35C and TIP36C, I would like to know if somebody did try them as output transistors with the TO264-TO3 PBL SYMASYM using a 25V-0-25V transformer, and what is the result. Thank you.

Best regards.


brianco 8th January 2013 12:11 AM

Me too please Rudi!

Rudi_Ratlos 8th January 2013 01:14 PM

1 Attachment(s)
I will not provide you with anything else but the PCBs!
Matching the output transistors (NJW0 for example) is a time-consuming job, and I am currently very much engaged with my own projects
(see attached image).

But: the success of a SYMASYM does not rely on perfectly matched output transistors.
One of the SYMASYM's secrets is the very fast and direct feedback!
Give the SYMASYM a matched pair of differential input-transistors - that is it.

@GrobAlt: please read this thread:

Best regards - Rudi_Ratlos

brianco 8th January 2013 02:38 PM

Thanks for that seem busy!

jprco 14th January 2013 06:59 PM

Hi, Rudi. I used the extra SymaSym 5.3 boards to build the TO-3 version as shown in the early posts on this tread. Some lead bending and components soldered under the pcb but is works and sounds excellent (Bias at 13mV per 0.22R and +-35V). I was wondering if I can safely increase the rail voltage to +-40VDC as I have a spare 28-0-28 toroid with a 15-0-15 VAC as well for a preamp. Any problem?? Same bias adjustment. I put in 63V caps already.
I think I prefer the sound of this amp version to either the 5.3 or even the FC100 dare I say !!
I would also like to be include for 2 amp PCB in the next group buy please.
Thanks, Jean

evette 15th January 2013 04:16 AM

Hi JPRCO Sure you can increase the voltage to 40. Evette

Rudi_Ratlos 15th January 2013 08:10 AM


... but be aware of the breakdown voltage of the input differential transistor pair.
For example: VGDS of 2SK170 is −40 V! So: you will be "on the edge".

And yes: the TO3 version is the best sounding version of the SYMASYM in my ears as well, but cannot compete with the FC-100 in my ears.

Best regards - Rudi

All times are GMT. The time now is 07:19 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 17.65%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio