VSSA Circlotron

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UltimateX86

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Joined 2004
circlotron.audio
CFA Circlotron

HI

I tried to simulate a VSSA CIRCLOTRON but i have no gain ...

Must I add a follower after VAS ?

corrected schematic : it works
VSSA_CIRCLO.png


https://sites.google.com/site/opampbasedamp/CircloVSSA.asc

Could you help me ?

Thanks
 
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Joe Berry

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Joined 2001
Paid Member
Hi UltimateX86,

I can't run your simulation right now but I think it will work in principle. I'd suggest checking all DC operating points with no signal to be sure they're where they belong.

Also, V2-V3 can be 24V or less, and the PNPs can be small signal devices idling at 5-10 mA. These changes are optional but may reduce build cost somewhat.
 
BYRTT

BYRTT

Member
Joined 2009
As jerluwoo point out added two caps to schematic. I'm not sharp in construction but noticed the VSSA originals didn't swing or make gain if this cap missed. The VSSA originals used 470-2200uF/6,3V and some even bypassed the elco with 10uF MKT. The more value for the elco the lower the -3dB highpass in LF region, and more linear group delay down there.

EDIT if this will do and you build it, beware that this cap influence the sound quality as it were sitting as a coupling cap in hot signal, therefor if seeking high quality sound performance pick caps value/bypassing/quality/cost as scenario prefered.
 

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ballpencil

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Joined 2013
Rather than having a huge 2200uF resistor, i'd prefer replacing the CCS with resistor. A CCS on a common emittor is unusual.. Any voltage swing on the base will just be consumed by the CCS, leaving no voltage swing on the cathode.

Attached is my version on your amp. This would be an expensive amp on the power supply side, especially if stereo.

edit: RC is 2 kohm
 

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banat

Member
Joined 2009
ballpencil said:
Rather than having a huge 2200uF resistor, i'd prefer replacing the CCS with resistor. A CCS on a common emittor is unusual.. Any voltage swing on the base will just be consumed by the CCS, leaving no voltage swing on the cathode.

Attached is my version on your amp. This would be an expensive amp on the power supply side, especially if stereo.

edit: RC is 2 kohm
Click to expand...

Hi Ballpencil !

Just a thought that OPS both ground reference resistors (R13&R17=1K) are way to high in value , think that anything between 47R and 100R will be better choice .

Best Regards !
 
U

UltimateX86

Member
Joined 2004
circlotron.audio
ballpencil said:
Rather than having a huge 2200uF resistor, i'd prefer replacing the CCS with resistor. A CCS on a common emittor is unusual.. Any voltage swing on the base will just be consumed by the CCS, leaving no voltage swing on the cathode.

Attached is my version on your amp. This would be an expensive amp on the power supply side, especially if stereo.

edit: RC is 2 kohm
Click to expand...


I found 4A bias :eek::eek: and lower gain
 
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ballpencil

Member
Joined 2013
Attached..

You may need to play with the values a bit.. FFT profile is not as good as your CCS version.

Ah yes.. bias was too high. I got 100mA bias once but the sinewave output was skewed. As i said, you need to play with the values.
 

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