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Old 26th September 2012, 07:34 PM   #1
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Default What would you change in this schematic? (PP amp)

hi, I ''like'' the sound of my monoblocks but would like to know if there are obvious flaws, so I can make them sound even better. I have got them for a good deal and never bothered fixing them, now is the time. It looks like the builder put what he had in hand, so while the design is relatively fine, I think that the values are maybe off. I am not experienced enough to know what should I change, so I ask.

EDIT: I would like to know what are the critical caps and resistors. I need to change those. The builder used quite bad components. I'm not enough experienced to determine which caps and resistors are the most important in here, would like someone to help me...

I attached the schematic.

thanks
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File Type: doc Mono Amp Tube final.doc (56.0 KB, 268 views)

Last edited by murphythecat8; 13th October 2012 at 07:51 PM.
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Old 26th September 2012, 08:37 PM   #2
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I would use the second triode inside first twin triode as a CCS for the LTP, and bettering the balance. Or also as a CCS for the plate of the first unit, but prefer the first idea.
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Old 27th September 2012, 04:31 AM   #3
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hum pot if your dead set on tube rectification and that small power supply filter. you need a protection scheme for the B+ circut to protect your output trannies....either hi voltage fuses or 1 ohm resisters, fuses being my preference.
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Old 27th September 2012, 08:59 AM   #4
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Something wrong in the schematic?
It looks like the "virtual center tap" of the 6,3V heater should be elevated to +60V according to the schematic. The way it is shown, it looks like it is referenced to ground level by the two 1k/20W resistors.
Normally you would make a voltage divider with two resistors from B+ to ground. The lower resistor is bypassed by a cap (that would be the 220F cap in your schematic).
Maybe I am not getting something here.

Best,
Martin
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Old 27th September 2012, 09:57 AM   #5
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Quote:
Originally Posted by bayermar View Post
Something wrong in the schematic?
It looks like the "virtual center tap" of the 6,3V heater should be elevated to +60V according to the schematic. The way it is shown, it looks like it is referenced to ground level by the two 1k/20W resistors.
Normally you would make a voltage divider with two resistors from B+ to ground. The lower resistor is bypassed by a cap (that would be the 220F cap in your schematic).
Maybe I am not getting something here.

Best,
Martin
The 60v is developed across the 1k 10W resistors (60mA through each). the schematic looks correct in that area.
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Old 27th September 2012, 10:48 AM   #6
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Aah, DHT.
Sorry, did not see that one.
Thank for clearing that up for me.
I'm a bit slow today...

Martin
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Old 27th September 2012, 08:47 PM   #7
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Originally Posted by speakerfritz View Post
hum pot if your dead set on tube rectification and that small power supply filter. you need a protection scheme for the B+ circut to protect your output trannies....either hi voltage fuses or 1 ohm resisters, fuses being my preference.
ok will do thanks.

anything else wrong here?
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Old 28th September 2012, 04:52 PM   #8
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Originally Posted by Osvaldo de Banfield View Post
I would use the second triode inside first twin triode as a CCS for the LTP, and bettering the balance. Or also as a CCS for the plate of the first unit, but prefer the first idea.
hi, I need to ask, why would you do this?
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Old 13th October 2012, 07:46 PM   #9
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Originally Posted by payitforwardeddie View Post
LISTEN, HAPPY WITH SOUND? LEAVE IT ALONE, THEN.
no, not totally happy.

Could anyone point me to what are the most critical caps and resistors. I'm not good enough to be sure about that....

I want to at least upgrade the critcal components, because I have a couple of bad resistors that do not belong in a hifi amp...
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Old 13th October 2012, 08:00 PM   #10
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Originally Posted by murphythecat8 View Post
no, not totally happy.

Could anyone point me to what are the most critical caps and resistors. I'm not good enough to be sure about that....

I want to at least upgrade the critcal components, because I have a couple of bad resistors that do not belong in a hifi amp...

Parts quality only results in subtle improvements. It's not a "major makeover" kind of thing. Maybe it's the sound of the circuit you're not happy with? What don't you like about the sound of the amp as it is now?

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