10Y, 26, 27 and 45: relative microphonics - diyAudio
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Old 1st June 2006, 04:45 AM   #1
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Default 10Y, 26, 27 and 45: relative microphonics

I want to build a preamp using one of the above tubes. The 45 I’ve heard is highly microphonic:

Are any of the others lower/ low in microphonics?

Thanks
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Old 1st June 2006, 06:03 AM   #2
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Rick
The 45 is midly microphonic. Not much
10y is not microphonice maybe slightly.
27 is microphonic
26 is the momma of microphonic.

I used all so the power tubes in my exprience is midly only.
With microphonics just have a subchasis with plastic pcb standoff supporting it and you should be fine


REgards
NIcholas
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Old 1st June 2006, 06:22 AM   #3
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If I understand you correctly, you used them in power amps, which would not fully reveal their microphonics, vs in a preamp - where microphonics are multiplied “100” times”.

However the technique could help, would it help enough in a preamp?
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Old 1st June 2006, 06:26 AM   #4
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Default other tubes

I'd also consider the 12B4A & 12BH7A

Cheers
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Old 1st June 2006, 06:26 AM   #5
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I used all in preamp.
What i meant that i tried the power tubes in preamp segment and i find them not at all microphonic
SOrry was a rush response

My 26 and 27 are both balloon. UX226 and UX227. THe 227 i have is mesh.

Before this technique i could talk to my 26 and ith will respond thru the speakers. Also what happens the sound has a rush and echo feeling due to the mechanical feedback applied to the 26 as the sound is hitting the glass like a microphone.
Don't worry about 45 or 10y this are not that hard to get right

Cheers
nIcholas
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Old 1st June 2006, 06:32 AM   #6
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If you are considering dht don't waste time with the idht brothers. They are far inferior to the dht brothers unless you do not have the time to troubleshoot and debug the microphonic and hum part of the dht
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Old 1st June 2006, 07:10 AM   #7
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Thanks Nicholas!

So (newbie here) the dht are only the 45 and 10y; while the 26, 27 and 12B4A are idht – so if you think you can debug the microphonic and hum, go either 45 and 10y??

Cheers
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Old 1st June 2006, 07:16 AM   #8
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Rick
Apologies if i confuse you
26,45,10y are dht

27,37,57,76 are old skool dht

the rest 9 pins and 7 pins

If possible avoid the 9 and 7 pins
Go for either 26 or 27. 45 and 10y not worth the effort. But you gain bragging right. 10y get the thrioated fillament like vt25 or 801a. this has very sparkling highs but no enough bass energy and mids. vt25a like western e's ceramic base is good balance but can't come close to the 26.
26 is a pain in the **** to make it work. 27 is not to far away in sound but easy to work with. Not popular as the voltage is 2.5volts. It sounds better than 37,57 or 76 because the fillament current is 1.8a. 26 sounds better than 01a because fillament current is bigger. Moral of the story is to go for high fillament dht as they sound more fuller

Cheers
nIcholas
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Old 1st June 2006, 10:06 AM   #9
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Hi Nicholas

You are *very helpful * : )

Here is a 27 circuit described as “If you don't have to drive long cables (>50cm), this is the way to go” http://www.dhtrob.com/schemas/afbeeldingen/vv227lun.gif

As the preamp is to use in a very high gain (horn) system, I might well use DC Filament per TentLabs Supply http://www.tentlabs.com/ProductEntit...terSupply.html

Can you suggest a simpler/ better 27 preamp circuit?

Thanks kindly
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Old 1st June 2006, 11:01 AM   #10
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Default FYI

The 27 is not directly heated.
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