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Old 28th February 2006, 05:22 PM   #21
ilimzn is offline ilimzn  Croatia
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Old 28th February 2006, 05:23 PM   #22
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thanks, thats what i thought, just thought i better check first before i smoke anything..lol..
cheers,
Owen
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Old 28th February 2006, 05:29 PM   #23
anatech is offline anatech  Canada
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Hi Owen,
Set the pot to maximum resistance. Monitor for excessive current flow no matter what.

-Chris
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Old 28th February 2006, 06:31 PM   #24
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hey, i set the pot to maximum and monitored everything on power up.. it worked.. but same problem as before. i tried pluggint he mini disc player straight into the SS section and got pretty good quality sound out very quiet.. qith the tube section it sounds good at very low volumes and then as you turn the input level up it isnt happy...
Owen
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Old 28th February 2006, 06:38 PM   #25
anatech is offline anatech  Canada
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Hi Owen,
That's pretty much what I would expect. Have you tried the CCS version or just the resistor version?

-Chris
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Old 28th February 2006, 06:47 PM   #26
ilimzn is offline ilimzn  Croatia
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I know Chris is a fan of the CCS approach, but I would vote for the bootstrap approach first, then refine it further (if needed) with CCS.
The relatively low value resistors from input to rails make the job of your tube front end VERY difficult (it sees an impedance of about 5k, and it would be much happyer with at least 10 times that, or even 100 times).
You may want to just increase them like I mentioned in my reply above re bootstrapping, even without the actual bootstrap caps, it should make it possible to drive the SS stage to a slightly higher volume. If that turns out to be the case, then you are on the right track.
In theory, you could increase these resistors quite a bit but then you would have problems with redesigning the bias generator for that, so I think a bootstrap test would be a better idea than making the resistors too large.
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Old 28th February 2006, 06:52 PM   #27
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i have tried the resistor version useing the 2 x 12K resistors + and - with and without the bootstrap caps.. i used an output cap to get rid of the DC offset for testing purposes.. it was about twice as loud with the bootstrap caps in place.. I havent tried the CCS version yet though..
Many Thanks,
Owen
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Old 28th February 2006, 07:10 PM   #28
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just played a lil more. measured about 4V DC offset!!! and it went up to about 6V with volume at max!! dosnt sound right to me but im gunna wait and see what you guy's think..
Owen

Oh dear.. It's got to the point where ive had to bake more flapjacks and put my thinking hat on Flapjacks are brain food
Owen
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Old 28th February 2006, 08:04 PM   #29
anatech is offline anatech  Canada
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Hi ilimzn,
In this case, a CCS solved some problems for me in one easy to implement fashion. The LED's are pretty too. I'm always open to suggestions.

Anyway, I was looking for about 100K (my ground reference) and the CCS didn't load this down much further.

Owen,
How have you referenced your input to ground?

-Chris
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Old 28th February 2006, 08:09 PM   #30
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the input to the tube stage is tied to ground through a 720K resistor.. should i add a resistor on the input to the SS section too?
Owen
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