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Valve upgrade T.A.C. 34MK

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panterauffe

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Joined 2014
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#1
An externally hosted image should be here but it was not working when we last tested it.


Hi all. My first post on this forum. Been lurking around reading a lot and I'm amazed at all the knowledge on here 🙂

So anyways, bought my very first tube amp and I'm totally hooked! Coupled it with a Heed phono pre fed by a Rega P25 with a Benz MC high output.
Also feeding it with Wimp HIFI through a Sonos via a DAC magic for casual listening.

Now for my questions;
I'd like to try some upgrades in the power tubes in exchange for the generic Chinese EL34S, and I've been reading a lot of good about the Genalex kt77 Gold Lion. Also I'd like to try the 6CA7s from Electro Harmonix for a supposedly fatter sound.

Now I wonder, will I have to change anything on the amp or does the term self biased mean it will automatically adjust itself (fat chance, right!?) to the new valves, which I believe draw a lot more current than the original valves?

If so, is it hard to do? Or something I could learn to do myself and in that case what kind of instrumentation would i require?

I know I can probably go to my dealer but I'd so like to be able to swap and try in the comfort of my listening chair.

All input is welcome on this for me totally new world of sound.

Anyways, fun to be here and all the best
 
#2
panterauffe said:
Now I wonder, will I have to change anything on the amp or does the term self biased mean it will automatically adjust itself
(fat chance, right!?) to the new valves, which I believe draw a lot more current than the original valves?
Click to expand...

If the amp is self biased, there is a large output tube cathode resistor that generates the bias voltage, and this tends to compensate for variations in tubes.
The KT77-EL34-6CA7 types are all electrically similar and will work in the same socket. Some of their filaments draw more current than others, if I recall.
 
#3
If (as is almost certainly the case) self bias simply means RC networks in the O/P tube cathode circuitry, you are in a "plug and play" situation. 🙂

Yes, the "reissue" Gold Lion KT77 is a fine tube. Communicate with a RELIABLE vendor to ensure that the tubes you receive are appropriate to your situation. It's all too easy to get tubes whose cathode current makes them a poor mate for your equipment.
 
#5
Just talked to the agent for Vincent and T.A.C. and he thought that I'd have problems tube rolling with this model since it would need to be recalibrated compared to the T.A.C. 35, which is "auto biased".
What's the difference between self biased and auto biased?
And Jeff, are you suggesting an exchange of the preamp tubes as well?
Thanks for you replies so far
 
#7
If You want change to tubes with more current, You can note if Your PS /rectifier, and also, important, chock, OT will keep more current?/ is suitable for increasing the current. Also more current, probably, leads to increasing the humm, because Uhumm=Rps X I /I that will increase/. in Instead 6N3P You can use 5670, that is best in that series.
 
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#11
Autobias is with cathode resistor, that lift U cathode compared to first grid.
Self bias is the same.
Fixed bias is powering the first grid with minus U from separated U DC. /Cathode connected to ground/.
 
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#20
If you are still looking at valves for the power side, I recommend Winged Cs as being an excellent all-rouder. I've tried the EH 6CA7 but they lack midrange qualty for my tastes. I've going to try some GE JAN 5670 in the second system preamp (used in conjunction with a tpa3116 power amp).
 
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