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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Best input DHT tube?

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26 tentlabs lownoise filament supply on the left with the potted 12V transformer and tentlabs AD1 filament supply on the right ( 4V) the big 90watt 10ohms are note showed in my pictures they are on the front ..

thanks for your words Andy, this amp is born because of you :)
 
This is really up my street. I've been experimenting with different DHT small tubes for 3 years in 300b SETs. In terms of input tubes I found I liked in approximately this order:

26 - my preferred option for tone and overall magic
10Y - capable of great clarity and dynamics, but I missed the 26
01A - very good, but not as magical as 26 or clear as 10Y
30sp (VT67) - surprisingly good, less microphonic than 30
46 - usually a driver tube, but very neutral with good tone
1G6G/GT - surprisingly good but very microphonic, so needs special mounting

I currently use a cheap solution - two Hammond 156C chokes of 150H, in series making 300H.

Not that it matters Andy, but wouldn't two identiacal chokes in series be four times the inductance? (N-squared?) Not to nit-pick on you, but I just need to check on my own knowledge - that it isn't all wrong.

I have some 1G6Gs, think I might try them. How about 3A5s? I bought a bunch to use in guitar pedals, but my ignorent me didn't think about how microphonic DHTs must be, so I have them in a box waiting for a reason to be.
 
Two chokes in series are double the inductance and half the capacitance, so good news with the 156C.

1G6G is a misprint - should be 1G4G. The round plate GT version is also nice. These are quite microphonic. The 3a5 is less microphonic, and it's easy to find two or three rubber O-rings to slip over the bottle to dampen it further.

Andy
 
for the tentlabs filament , i have ordered the low noise model for the 26 and it is given for 1 amp max so after two hours of listening i have one side off with the temperature auto shutoff .. the side in fault has a 20cm cable to the tubes so i change his place and now have 10cm after the module and it seems ok ....... at this time! :)
 
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