The Valorous Amp - A modest aggregation of pass inspired ideas - Page 2

kasey197 · 28th February 2013, 12:59 AM

Just a small update on things. Thanks to the suggestions on-list and off-list, I've removed C1, C3 and C4. Yes, the dreaded 'bypass' caps are gone (well for the moment).
The input fet (M4) has had a 1k resistor added in line with the gate, and I've increased the gate stoppers for the Jfets to 470R for now. I kept the -ve rails as far away from the outputs as I could and the amp is now very stable. Square wave testing is also clean with the larger stoppers. HF performance is not yet optimal (you can see some small rolloff on the leading edges).

Overall I'm pretty amazed how well such a simple circuit does - with the basic config proven, I'll go ahead and do a PCB for further work to take place... if anyone with PCB experience wants to take a stab that would be most welcome else its a transparency sheet, layout tape and marker pens for me (dates me a bit i know!)....

kasey197 · 28th February 2013, 02:13 AM

30v pk-pk square wave at 1khz ... any comments other than the HF rolloff ?

Nelson Pass · 28th February 2013, 02:16 AM

Maybe you want to trim your scope probes.

destroyer X · 05:29 AM

Thank you.

Carlos

kasey197 · 5th March 2013, 07:30 AM

Carlos, wish my BJ skills could accommodate hahaha maybe some day

)

5th March 2013, 05:24 AM	#14
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	I like it...if was BJTs i would give a try Thank you. Carlos __________________ Audiophoolery; http://www.youtube.com/watch?v=m7ERMu825m4; Dx Super Etching; http://www.youtube.com/watch?v=WED3Bvmxepk Last edited by destroyer X; 5th March 2013 at 05:29 AM.

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28th February 2013, 12:59 AM	#11
kasey197 The Dastardly Dad of Three diyAudio Member Join Date: Sep 2009	Just a small update on things. Thanks to the suggestions on-list and off-list, I've removed C1, C3 and C4. Yes, the dreaded 'bypass' caps are gone (well for the moment). The input fet (M4) has had a 1k resistor added in line with the gate, and I've increased the gate stoppers for the Jfets to 470R for now. I kept the -ve rails as far away from the outputs as I could and the amp is now very stable. Square wave testing is also clean with the larger stoppers. HF performance is not yet optimal (you can see some small rolloff on the leading edges). Overall I'm pretty amazed how well such a simple circuit does - with the basic config proven, I'll go ahead and do a PCB for further work to take place... if anyone with PCB experience wants to take a stab that would be most welcome else its a transparency sheet, layout tape and marker pens for me (dates me a bit i know!)....

28th February 2013, 02:16 AM	#13
Nelson Pass The one and only Join Date: Mar 2001	Maybe you want to trim your scope probes.

5th March 2013, 07:30 AM	#15
kasey197 The Dastardly Dad of Three diyAudio Member Join Date: Sep 2009	Carlos, wish my BJ skills could accommodate hahaha maybe some day )