• 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.

HQ-DHT (All tube DHT amli) 26-45-2A3

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Here's a slightly clearer version. The grid stoppers should probably be less than 1K. Note there are two 156C Hammond plate chokes in series, wired out of phase. Both the 10 ohm cathode resistor and the negative side of the filament supply on the 26 go to ground. This is filament bias, for those unfamiliar with it. It needs a very clean supply, hence the choke input which is 280mH. The Lundahl LL1692A can be swapped for the much cheaper Hammond 126C with very good results. This makes the amp good value to build. The O-netics OPTs are level 1, and are strongly recommended over other alternatives. Again, good value. All the 47uF caps should be polypropylene, not electrolytics - motor run caps are a good value option.

Andy

Hi Andy,
Perhaps, adding a second cap after each resistor on B+ rail would help to have the resistors isolated from the coils.
 
Hi Edy, Good to hear that the 26 Filament Regulator kits work well - thanks for letting us know!

The dc - dc filament heater for 45 and 300B will be quiet, but it will give no barrier to high-frequency noise from the mains. Also, the dc - dc output will have a cheap electrolytic inside.... and since the 45 filament is also the cathode, the music signal will be forced into the electrolytic by the filament dc voltage - and your amp will be improved when you use all of your regulator kits.

Many other good dc solutions can be greatly improved for Sound Quality, even if you have no hum!

www.audiofaidate.org • View topic - water babies: un line driver DHT e xover passivo


Hi coleman, i have replace filament supply 45 with your filament regulator kit. and for 300B used 5VAC. i get good result and no hum.
i feel more natural.

i have some problem when i used IT hashimoto A107 for 26 to 45. i can't get low tone better. (IT A105 for 45 to 300B).
now i no used IT for 26-45 replace with R-C. better than used.
 
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