100W Ultimate Fidelity Amplifier

[still4given]

I wake up and still no one has completed and tested the FH11 yet? I was able to build a pair of VSSA's last night and tested one. The VSSA, although has the name "very simple" is not as simple as the FH9

You're a hero

 

[keantoken]

It's nice macho thing going on here.

 

[still4given]

 

[xrk971]

About the only way to get my daily soldering fix is to trade sleep for builds

 

[andrewlebon]

Hello

Hello
greetings just did a quick test on FX11 hard hitting bass nice mid and
and treble dc rails 52 volt +/- many thanks to sonal for his wonderfull
pcb desigining and apex audio
warm regards
Andrew

 

[apexaudio]

Hello
greetings just did a quick test on FX11 hard hitting bass nice mid and
and treble dc rails 52 volt +/- many thanks to sonal for his wonderfull
pcb desigining and apex audio
warm regards
Andrew

Nice work.
Regards

 

[xrk971]

It's alive!

Nice work Andrewlebon!

Thanks for your quick work on this. Have you been able to do a max power stress test on a dummy load?

 

[andrewlebon]

Hello
greetings in this version of sonals pcb MJE 350 pin outs have to be changed
see MJE350 on pcb otherwise no mistakes on pcb
warm regards
Andrew

 

[andrewlebon]

Hello xrk971
greetings played it at loud levels everything is super clear tomorrow i
will do some more testing and keep you informed
warm regards
Andrew

 

[xrk971]

Hello
greetings in this version of sonals pcb MJE 350 pin outs have to be changed
see MJE350 on pcb otherwise no mistakes on pcb
warm regards
Andrew

Good catch - I missed the fact MJE350 is ECB when switch made from MPSA92 (EBC). That would not have worked at all

 

[andrewlebon]

Can 1381/3503 work in place of MJE340/350 i like the sound of KSC1381/3503

warm regards
Andrew FX9 sound is softer

 

[xrk971]

I just ran sim with proper model for 1381/3503 and it works fine. I plan on using those as I like their sonic signature too. VHEX+ amp uses them to drive 2 pairs of IRFPs also.

 

[still4given]

Singing. Only testes with +-44V so far. Sounds fine through test speakers. I would like to have a trimmer for offset adjust. Hfe matched LTP and have 4mV on one channel and 20mv of the other. Not really an issue but still there. There also some turn-on noise. Will have to investigate that.

Edit: I used SMD for most of the small caps.

 

[xrk971]

Nice work Terry!

The SMT for small caps is a good idea. I have been pretty lucky with offset in the 1-3mV range when I match BC546C's spot on. Maybe 5551's are harder to get stable for matched Hfe?

You seem to have plenty of room for local heatsink on MJE250 - does it get warm?

 

[still4given]

I don't have any more time today to do testing. I only ran it for a few minutes and only at +-44V so I can't say if the little heatsink is necessary.

I could probably play around with different transistors and get the offset lower but a trimmer wound eliminate the issue. If I were serious about this amp that is what I would add. When I have the time I will hook up a bigger PSU and run it through my scope and test for clipping and square wave response. I'll check the heat of the small heatsink at that time.

Blessings, Terry

 

[apexaudio]

Singing. Only testes with +-44V so far. Sounds fine through test speakers. I would like to have a trimmer for offset adjust. Hfe matched LTP and have 4mV on one channel and 20mv of the other. Not really an issue but still there. There also some turn-on noise. Will have to investigate that.

Edit: I used SMD for most of the small caps.

Nice work, use 100R trimmer instead two 47R resistors (R16. R17) for offset adjust.
Regards

 

[donovas]

hi, i built FH9 from the pcb posted while back.

1k bias resistor.

how do i adjust the bias with this?... thanks.


oh and fh9 sounds verry nice, btw. smooth and warm unlike what i expected coming from vssa. similar level of performance none the less!

 

[still4given]

Nice work, use 100R trimmer instead two 47R resistors (R16. R17) for offset adjust.
Regards

Like this?

 

[apexaudio]

Like this?

Yes

 

[xrk971]

hi, i built FH9 from the pcb posted while back.

1k bias resistor.

how do i adjust the bias with this?... thanks.


oh and fh9 sounds verry nice, btw. smooth and warm unlike what i expected coming from vssa. similar level of performance none the less!

Pictures please. What supply voltage are you running?