At #48 and #49 there is some discussion about power tube grid stoppers.
"
The screen grid stoppers in the tu-8200 may be a bit low in value according to the widely reccommended value of 300 ohms for triode and 1k - or more - for UL use"
In TU 8200 R version which resistors are these "grid stoppers"? (I am trying to find the humming anomaly some of my 807 tube in Triode mode. Anomaly is like a humming, but penode and UL is perfect with these tubes)
"
The screen grid stoppers in the tu-8200 may be a bit low in value according to the widely reccommended value of 300 ohms for triode and 1k - or more - for UL use"
In TU 8200 R version which resistors are these "grid stoppers"? (I am trying to find the humming anomaly some of my 807 tube in Triode mode. Anomaly is like a humming, but penode and UL is perfect with these tubes)
I am not especially fluent in reading schematics, but trying to help myself with that:
http://www.valvewizard.co.uk/gridstopper.html
and looking on schematics of TU8200R I suppose, grid stoppers can be R23 and R24 for triode setup and PTC1/PTC2 for ultralinear mode... But it needs confirmation from somebody, who will know - not guess, like me...
http://www.valvewizard.co.uk/gridstopper.html
and looking on schematics of TU8200R I suppose, grid stoppers can be R23 and R24 for triode setup and PTC1/PTC2 for ultralinear mode... But it needs confirmation from somebody, who will know - not guess, like me...
Hello Sir_Gorg!
Well, not only the appearance of your Elekits is inspiring, but I started on the thread we were talking about, the screen grid stoppers.
In the position of R23/R24, instead of the factory 1k Ohm resistor, I tried 1.8K Ohms (this was at home, also in the form of a Z-Foil) and for the first test with 807 tubes that used to buzz in Triode (but sounded brilliant in the other modes) now after almost half an hour there is no hum in Triode mode. I'll have to knock myself out if that's really the solution to this freaky anomaly. So far, I haven't tried it with my other tubes that buzzed in a similar way (I will try it sometime in the future anyway), but now I'm happy that this pair works flawlessly for now.
Well, not only the appearance of your Elekits is inspiring, but I started on the thread we were talking about, the screen grid stoppers.
In the position of R23/R24, instead of the factory 1k Ohm resistor, I tried 1.8K Ohms (this was at home, also in the form of a Z-Foil) and for the first test with 807 tubes that used to buzz in Triode (but sounded brilliant in the other modes) now after almost half an hour there is no hum in Triode mode. I'll have to knock myself out if that's really the solution to this freaky anomaly. So far, I haven't tried it with my other tubes that buzzed in a similar way (I will try it sometime in the future anyway), but now I'm happy that this pair works flawlessly for now.
Thank you to the users who have provided me with the spreadsheet from Ferenc.
I have a further question - I am wanting to replace Capacitors C3, C4 with the MCap Supreme SilverGold.Oil 0,10 µF (not sure I can post links?)
These are rated at a much higher 1000vdc. Mundorf do not publish the ESR of these caps from what I can see. While I know it should be safe, I have read that electrolytic caps can have a decreased capacitance when so far below the rated voltage.
Am I setting myself up for any potential issues (other than placement) by making such a change?
I have a further question - I am wanting to replace Capacitors C3, C4 with the MCap Supreme SilverGold.Oil 0,10 µF (not sure I can post links?)
These are rated at a much higher 1000vdc. Mundorf do not publish the ESR of these caps from what I can see. While I know it should be safe, I have read that electrolytic caps can have a decreased capacitance when so far below the rated voltage.
Am I setting myself up for any potential issues (other than placement) by making such a change?
I would like to add to my above thought about the less sensitivity of the Tu-8200 regarding the coupling capacitors: I have already tried Russian PIOs, Wima, Kemet SMR, Panasonic and who knows what else in the c3-c4 and c9-c10 positions.
Not only the types, but also the different capacities represented themselves. And yes, I know, according to the manual, 0.1uF or larger you need, at the same time, the best acoustic result for me so far (I like it best) is c9-c10 0.25uF K73-16, while c3-c4 gives 0.047uF (Jupiter Comet this time) . The latter is obviously of low value, but the sound I get is very "lively".
Not only the types, but also the different capacities represented themselves. And yes, I know, according to the manual, 0.1uF or larger you need, at the same time, the best acoustic result for me so far (I like it best) is c9-c10 0.25uF K73-16, while c3-c4 gives 0.047uF (Jupiter Comet this time) . The latter is obviously of low value, but the sound I get is very "lively".
I have made a set as adviced by hificollective (V Cap ODAM and Mundorf MCap ZN). I am very glad of the overall sound.This is a sort of "report back with findings" after having made all Ferenc's alterations, as well as adding the Lundahl OPTs. I've spent a few months with it and an assortment of tubes, settled for now on RCA cleartop 12au7 driving Tung-So, EL34B. Even more than E80CC and 6LCGC combos, this is close to perfection for me. Even at low volume the delicacy and defintion, imaging and tonality are superb! This is in comparison with quite an assortment of amps in my listening space.
Thanks to Elekit and Ferenc for this audio gift.
Cam
Thanks to Elekit and Ferenc for this audio gift.
Cam