• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

what double triode is less microphonic ?

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kevinkr

kevinkr

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inertial said:
Kevin, thanks for your comments

because I must drive this :
http://www.audiodesignguide.com/PowerFollower/index.html

As I said I am satisfied of my 6N6, but this do not mean that I do not must search to make even better! :D

I am curious about 6H30 e 6C45P.....................


I disagree about microphonics. I have 6922 sovtek ( not one but 8) and Mullard Ecc88 that have zero microphonicity. Rare but exist! :D
The bad of microphonicity is undervalutated IMHO, I have made experiments for years with vibrations so there is no possibility one can
make me change my idea :angel:

Cheers,
Paolo
Click to expand...

I'm not saying microphonics should be ignored, just that many useful types exhibit it to a degree, and that there are usually ways to deal with it if not extreme..

I wasn't talking about any specific brand, just type.. Yes I know the Sovtek 6922 is often good in this regard, I just didn't like its sound at all the last time I used a few. Mullards sound much better IMO, but I have run into microphonic examples of theirs.

IMO some of the least microphonic types are also the least pleasant to listen to.. Of the 6DJ8/6922/7308/ECC88/E88CC I have met there are just a very few that I actually like. Western European Mullard, Amperex, Mini-Watt, and Telefunken being amongst those number and now sufficiently expensive that I avoid them. I used to detest them all but now find if used with some thought give good results - I just like the 5687, 5842 and triode connected D3A so much better.. I seem to recollect the JJ '88 sounded pretty good, but was slightly microphonic.. oops...

Fivre made some really good stuff too, I'm wondering how good their ECC88 was..
 
45

45

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Joined 2008
inertial said:
thanks 45,

Unfortunately I need absolutely Rp = 1600 ohm or less :(

Paolo
Click to expand...


I don't think it will change a lot.

These are small power pentodes and have enough power to drive your solid-state follower.

You have just to choose one and figure out the best operative point in your circumstances.
If you want to stick to a simple SE driver, as a line of guide, you can get your 10 Vrms using a 10-12K anode resistive load and 250V voltage supply.

If you really want lower Zout, IMHO, you should better go for SRPP or mu-Follower drive stages.


Cheers,
45
 
45

45

Member
Joined 2008
kevinkr said:


IMO There is almost no such thing as a completely non-microphonic type, I have encountered microphonic examples of almost everything I have ever used. Some will be way better than others, but to toss an otherwise good tube because of microphonics is unfortunate. Shock mounting and isolating them from sources of excitation go a long way toward making this a minor problem. (There will still be some that are not usable in a phono stage, but anywhere else this should usually not be a major issue.) I use 26 dhts in my system and I have been told flatly that they are hopeless in this regard, and they aren't - and every sample I have is quite microphonic. (I have only a few I consider unusable.)
Click to expand...




;)
 
kevinkr

kevinkr

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inertial said:
Hi Kevin ,

I agree with you, zero microphonicity do not make automatically
good sound, otherwise transistors would be better of all! :D
things are complicated, this is the fact ( and our fun,no?)

Important imo is accumulate experiences and learn, always .
:)

Cheers,
Paolo
Click to expand...

Absolutely true, and I still find myself explaining the whole tube thing to my friends and acquaintances..

:D
 
I

inertial

Member
Joined 2004
45 said:


6BX7 has typical mu=10.

Cheers,
45
Click to expand...

Hi 45,
some precisations :

The fact is my audio chain have only two stages after the DAC,
the tube is the gain stage, the mosfet is the current gain.
In this minimalistic situation today I have a whole gain of about
10 times ( 20 dB) with cathode not bypassed and about 14 times with cathode bypassed ( 23 dB).
This is sufficent with my speakers ( true 87 dB/2,83v) but I can't go belowe 10 times :D

Cheers,
Paolo
 
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