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Silicon Chip ULD Mk3 amp - 0.0006% distortion
Silicon Chip ULD Mk3 amp - 0.0006% distortion
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Old 29th June 2011, 01:39 AM   #11
wahab is offline wahab  Algeria
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Originally Posted by jcx View Post
maybe they read and understand my posts on the issue - TMC is not "more stable"
Perhaps when computing according to a model with idealized components,
but so far , all the simulations i did showed that generaly TPC is less stable
with capacitive loads, for some logical reasons..
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Old 29th June 2011, 01:51 AM   #12
jcx is offline jcx  United States
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match the high frequency loop gain curves as properly measured around the output devices, "inside" the TMC network and the stability properties are going to be very similar - for well understood engineering reasons...

you may notice several others in the Cordell Book TMC discussion thread made good cases for the essential similarity of 2-pole, TMC

also http://www.diy-audio-engineering.org...php?topic=26.0 thread - but drawings, attachments not visible to non-members


the loop gain matching isn't done by simply rearranging the same valued compensation components between 2-pole, TMC

Last edited by jcx; 29th June 2011 at 02:08 AM.
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Old 29th June 2011, 03:26 AM   #13
VHF man is offline VHF man  Australia
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Originally Posted by jcx View Post
match the high frequency loop gain curves as properly measured around the output devices, "inside" the TMC network and the stability properties are going to be very similar - for well understood engineering reasons...


You mean: you don't get something for nothing.
If you raise the olg above 20kHz by 20dB you are going to compromise stability regardless of method.

I have modified a mk2 version of the amp and it uses mostly TMC but also a bit of CMC. With an extra 20dB of 20kHz OLG thd is obviously very much reduced.

I favour TMC over TPC based on comparisons between the +ve slew rate - as well as my ears that tell me TMC sounds better with this design.
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Old 29th June 2011, 07:47 AM   #14
dadod is offline dadod  Croatia
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Look also this thread:
http://www.diyaudio.com/forums/solid...-resolved.html
dado
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Old 29th June 2011, 09:29 AM   #15
ostripper is offline ostripper  United States
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Default No longer impressed.

Is this amp 6 ppm THD20 ? At what output ? 6ppm is not hard to achieve these days. But can it "hold" that @ 100v p-p 20Khz ? 4R , anyone ? . If it's not a triple , highly doubtful ....
It does look like a nice build. Sporting those T-traks and using a real Vbe + 2 of the internal diodes must make for near perfect thermal response. Still , it is what it is.
PS - I can now beat TMC ... without TMC ( 2 designs).
OS
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Last edited by ostripper; 29th June 2011 at 09:31 AM.
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Old 29th June 2011, 11:44 AM   #16
wahab is offline wahab  Algeria
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Quote:
Originally Posted by jcx View Post
match the high frequency loop gain curves as properly measured around the output devices, "inside" the TMC network and the stability properties are going to be very similar - for well understood engineering reasons...

the loop gain matching isn't done by simply rearranging the same valued compensation components between 2-pole, TMC
Agree, but then most of the TPC advantages will be lost.
Although the result is better than classic miller comp THD wise,
it s inferior to TMC when looking at both THD and stability.
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Old 29th June 2011, 11:52 AM   #17
VHF man is offline VHF man  Australia
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Quote:
Originally Posted by ostripper View Post
Is this amp 6 ppm THD20 ? At what output ? 6ppm is not hard to achieve these days. But can it "hold" that @ 100v p-p 20Khz ? 4R , anyone ? . If it's not a triple , highly doubtful ....
It does look like a nice build. Sporting those T-traks and using a real Vbe + 2 of the internal diodes must make for near perfect thermal response. Still , it is what it is.
PS - I can now beat TMC ... without TMC ( 2 designs).
OS

Rated power, 8 ohms, 1kHz.

THD does degrade to 20ppm at 10 kHz but the reason is (apparently) due to minor limitation in the layout of the speaker traces. There will eventually be a mk4 to address it but we'll need to wait. However, there's nothing to stop constructors from routing the speaker earth return close to the rail feeds, and locating the output inductor further away from the vas.
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Old 29th June 2011, 03:30 PM   #18
ostripper is offline ostripper  United States
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Yes , THD20 and sub 50ppm does suffer with layout considerations. Is this amp still a standard LIN topology w/a CCS VAS ?

OS
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Old 29th June 2011, 05:02 PM   #19
prairiemystic is offline prairiemystic  Canada
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I read the mk2 had some blowup issues attributed to the VAS Q8 not being current-limited, SC added a 22k resistor on the (grounded) collector to fix. Scary that this mod and a few others don't appear on the SC website. Hopefully addressed in the mk3.
Looking forward to my issue arriving, postal strike here sucks.
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Old 29th June 2011, 07:11 PM   #20
wahab is offline wahab  Algeria
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Originally Posted by prairiemystic View Post
I read the mk2 had some blowup issues attributed to the VAS Q8 not being current-limited, SC added a 22k resistor on the (grounded) collector to fix. Scary that this mod and a few others don't appear on the SC website. Hopefully addressed in the mk3.
Looking forward to my issue arriving, postal strike here sucks.
It had several non solved issues, dont know to what extent these
were solved in the current version..
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