Simpelstark+ ODNF amplifier boards GB

[akimmet]

I am interested in building another power amplifier to drive some Magnepan 3.7i planer speakers. The Simplestark AX2 looks like an interesting design with just enough power to do the job. However; I would like to know if there is a known good source for the input jfets. If not, are there any possible substitutes? I do have some LSK170/LSJ74 and 2n5457/2n5460 if either of those types can be adapted.

 

[jwilhelm]

I've still got a couple sets of input fets for these amps in stock.

 

[akimmet]

I just gotten a Hafler 9505 up and running, so I no longer have an immediate need for another power amplifier. However; the design dose look worthy of trying out. Hopefully the AX3 will be finalized before then.

 

[akimmet]

It looks like virtualzeroaudio and vzaudio sites have been down for a couple of days now. Hopefully it will be back soon.

 

[jwilhelm]

I think Valery may have forgotten to renew the domain for the website. I'm waiting for him to come out of seclusion again to find out what's going on.

 

[vzaichenko]

Hello guys, sorry - my fault. In fact, it was not the domain, but "DNS hosting" - the one that links our domain names with the website.

Got it fixed, the site is going to be available soon.

Cheers,
Valery

 

[vzaichenko]

Yep, just checked - it's up and running again

 

[jwilhelm]

We're back! Good to see you're still managing to avoid the plague!

 

[vzaichenko]

Sorry it took some time to understand the real cause of the issue

 

[daanve]

Actually I am waiting for Simpelstark AX3 which is in design phase for almost a year.
Seems time to look elsewhere.

 

[jwilhelm]

The AX3 is actually finally back on my test bench waiting to be torture tested over the weekend. Things are slow going due to Covid here right now.

 

[daanve]

Covid allows me to do much work at home ... actually more than sans Covid.

 

[Dibya]

What is the overall slew rate of the amp?

 

[vzaichenko]

Around 50 V/uS - pretty close for both AX2 and AX3 versions.
The measured values are 53V/uS for AX2 and 50V/uS for AX3.

 

[Dibya]

@vzaichenko does ODNF have effect on slew rate of an amp?

Thanks for reply

 

[vzaichenko]

@vzaichenko does ODNF have effect on slew rate of an amp?

Thanks for reply

To some extent. AX2 with ODNF off shows 45V/uS - it's fast enough "as-is".

During the last year, I have learned how to design "no global loop" amplifiers with an overall slew rate above 100V/uS (the slew rate of a front-end standalone is 1800-2000V/uS), however, it's somewhat an overkill from a practical point of view. There are many other qualities, forming a good amplifier in combination. One of the undervalued ones - the phase shift throughout the audio frequency range.

AX2 is still my favorite amplifier in the home system.
I've got no AX3 prototype available though. Jeff has got one in his lab.

 

[Dibya]

Thanks for reply for all my doubt.

 

[andrewlebon]

Simplestark

Pcbs just arrived.

warm regards
Andrew