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Old 22nd October 2021, 08:48 PM   #191
vkung is offline vkung  Canada
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I want to make sure to all of you

TU-8900 is designed based on 12AU7 and 12BH7 only.
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Old 23rd October 2021, 10:40 PM   #192
havnjero is offline havnjero  Norway
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I have an upgraded 8600s but boy would I love to use a 2a3! sigh.
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Old 24th October 2021, 10:10 AM   #193
Whitigir is offline Whitigir
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Thanks for the clarification Victor!
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Old 24th October 2021, 09:53 PM   #194
paczeltf is offline paczeltf  Hungary
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ELEKIT TU-8900 2A3/300B
Quote:
Originally Posted by SandorS View Post
Any experience guys with pre tubes 12BH7(A) in this amp?
In case, with E80cc? I use latter in my TU-8200 (after changes required) and turned it into a very different amp vs. with 12au7 / ecc82 in. Upgrades by paczeltf. (...)
Thanks
The E80CC has about 50% higher gain than the 12AU7 or the 12BH7A. It should not be an issue in non-feedback mode, but the cathode feedback resistors need to be set to a lower value in the first stage when global NFB is in use.
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Old 25th October 2021, 01:43 AM   #195
Whitigir is offline Whitigir
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So when Non NFB is engaged, the E80CC is good to be used ?
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Old 25th October 2021, 03:30 AM   #196
vkung is offline vkung  Canada
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Location: Vancouver BC Canada
Any ideas for kit modification are welcome
But I want a responsible thread..

New diyers might follow your recommendation, but do not understand the rationale for the modifications.

I welcome your valuable contribution and support...
however:
-Please modify at your own risk.
-Please be specific when describing modifications.
-This is to prevent potential damage to your amp kit and of others...


I agree with Russ Sadd
This is what he posted few years ago

The E80CC is equivalent to an American 6085. This isn't, however, a 12AU7 /
ECC82. We're talking about a small double-triode, but one with very
different properties (i.e. mu of 37 instead of 17, using 6mA plate current
on average instead of 11ma). In conventional R-C stages, it may be possible
to directly substitute the two without anything going drastically wrong, but
you'll probably end up with more gain than you need and a good bit of extra
distortion. An E80CC won't be able to give the same 'kick' as an ECC82 when
used as a driver - it'll be putting out less power and with a higher anode
impedance.

My advice is always to take an eBay "substitution" with more than a pinch of
salt. I've seen too many 12E1 sweep tubes sold as "KT88 equivalents", not to
mention Mullard ECC32s sold as "premium 6SN7s"! This kind of sale is
guaranteed to (1) make the seller a lot of money and (2) gives the buyer a
good chance of burning out the valves along with his or her amplifier.

Thankfully, this "equivalence" is relatively harmless, and may only result
in decreased performance.

Best regards,

Russ Sadd
Birmingham, UK
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Old 25th October 2021, 03:52 AM   #197
vkung is offline vkung  Canada
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Join Date: May 2005
Location: Vancouver BC Canada
This is the reply from Mr Fujita..
Regarding your question,
Basically e80CC cannot be used for TU-8900 because the μ of the tube
is a lot different from the tubes we specify for TU-8900.
If we used E80CC, there is a possibility of oscillation.
So please refrain from using e80cc for TU-8900.

***

Also,
Mr.Fujita says that if non-NFB setting, it is OK to use e80cc,
but in that setting the gain will be too high, so the volume control will not function properly..
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Old 25th October 2021, 06:39 AM   #198
thejt is offline thejt
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Is anyone able to comment on the performance with 300B tubes compared to the 8600S?
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Old 25th October 2021, 10:19 AM   #199
Whitigir is offline Whitigir
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Thank you very much Victor!
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Old 25th October 2021, 08:45 PM   #200
SandorS is offline SandorS  Hungary
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Thank you, and others for inputs! Appreciated.
I miss the skills to even think in details here or calculate the values of cathode feedback resistors, would I use e80cc. At my own risk of course..

I'm also much interested in try comparing TU-8900 and TU-8200 in triode mode that I use.

My thoughts: I guess triode mode for a tetrode like 6l6gc is less linear than a real triode's as 300b or 2a3 are. Is it much off? Don't know.

Then, does one (me) really need the higher watts TU-8900 can actually give, higher than the estimated 1 watt or less I really use with TU-8200 (triode mode)? Don't turn volume knob to a third of what it allows (TU-8200); that gets loud enough on my loudspeaker (not a very efficient one but provides 94 dB on paper, AudioNote AZ3 Hemp). It's actually too loud for a 24 m2 room. True though, over this level the TU-8200 starts to distort quite a lot, to my ears (triode mode).
The OPTs there could be bigger, still I could live with them for 2 years now.

Then, how does 12b7* perform as compared to e80cc? Latter is just fantastic (generally speaking). I have no experience with 12b7* at all, nor any reports how it sounds in TU-8900. Any experience with 12b7 and particularly vs. 12au7 in TU-8900 would be great to hear about.


Thanks

Quote:
Originally Posted by paczeltf View Post
The E80CC has about 50% higher gain than the 12AU7 or the 12BH7A. It should not be an issue in non-feedback mode, but the cathode feedback resistors need to be set to a lower value in the first stage when global NFB is in use.

Last edited by SandorS; 25th October 2021 at 08:48 PM.
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