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Old 9th July 2011, 06:06 PM   #511
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completed my BERSIH2.0 based on 6N2P and 6P1P.. Sounds too clean (Bersih means clean in local dialect)...now to start playing with distortion and overdrive... so far total cost of is around 70USD.
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Old 9th July 2011, 06:29 PM   #512
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Sounds on different levels of gain. Almost the same loudness, different timbres. Is it good, or too much compression?

YouTube - ‪World Champion guitar amp project -- sounds on different levels of gain‬‏
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Old 9th July 2011, 06:33 PM   #513
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Quote:
Originally Posted by costis_n View Post
Can you please explain the power supply and output stage, it it too strange looking for my feeble mind... Pretty please?
Preamp and screen grid are powered from a network that supplies more of voltage on low signals, less voltage on high signals. It increases tone dynamics decreasing SPL dynamic.
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Old 9th July 2011, 06:50 PM   #514
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Quote:
Originally Posted by Wavebourn View Post
If you wired ground as drawn on your picture it have to oscillate.
Which wiring? First and second stage B+? They actually have an RC stage between them.

Ground is star connection with common point where B+ enters from HP supply.
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Old 9th July 2011, 07:10 PM   #515
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Quote:
Originally Posted by TheGimp View Post
Which wiring? First and second stage B+? They actually have an RC stage between them.

Ground is star connection with common point where B+ enters from HP supply.
What about input and output jacks?
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Old 9th July 2011, 07:46 PM   #516
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Input jack is grounded at the capacitor bank where power comes in.

Output tied to star as well.

All of signal path is single end grounded RG-174/U shielded cable.
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Old 9th July 2011, 07:48 PM   #517
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Quote:
Originally Posted by TheGimp View Post
Input jack is grounded at the capacitor bank where power comes in.

Output tied to star as well.

All of signal path is single end grounded RG-174/U shielded cable.
Are they both isolated from chassis, or form a loop through it?

By the way, I recorded sound on high pitch strings, to show compression of my amp:

http://www.youtube.com/watch?v=pRF05L9btYM
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Old 9th July 2011, 08:17 PM   #518
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No chassis. This is on a tube-lab type breadboard.

Since there is no global feedback, I've tried removing the ground to the output and letting it float. No change in the oscillation.

I also considered the possibility of feedback between the triode and pentode in the 6GH8A which were stages 1 and 3 which were in phase, so I changed the position of the triodes so that it is 6GH8A Pentode input driving tonestack, 6GH8A Triode second gain stage after tonestack, 6F4P triode 3rd gain stage, other 6F4P triode as Concertina, then the two output 6F4P Pentodes.

The oscillation breaks out at the peak of the signal and is only seen now on the 3rd gain stage through output.

I switched to a 400Hz test tone.
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Old 9th July 2011, 08:21 PM   #519
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At 30 and 31 seconds it sounds like your amp is note switching briefly.

Nice.
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Old 9th July 2011, 08:22 PM   #520
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Did you try 10k grid stopper for the output tube?
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