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Tube DIY Asylum: E-Linear W6m resurrection by PakProtector

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E-Linear W6m resurrection

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hey-Hey!!!,
I just got an interesting little experiment done. I just got my Heathkit W6m paired up. I tried the circuit out on my original mule amps, a pair of Dynaco Mk.III's. The E-Linear circuit takes a LTP built with pentodes and instead of decoupling its B+ node, the plate loads are supplied from the screen taps of their corresponding power tube.

The LTP got its tail done with a Supertex MOSFET cascode on a custom circuit board and uses Renata Li cells for extra bias voltage. I ran 6AC7 pentodes. Very nice combination of plate resistance and transconductance. Their screens are powered through a dropping R and bypassed to the common cathode node.

The PS is done with some of Jim McShane's components he offers for Citation II service. I added a Hammond 159T and left the filter as a simple Pi filter. All the power is fed to the CT of the output TX.

The OPT is the very nice 16431 Peerless that came with the amps. It is ~2k8:8R and has its taps at 40%. Usually the E-Linear amps sound best with that connection done at 20-25% with a custom wound OPT. There seems to be a sore lack of winders who offer winds with more than a pair of taps, let alone ability to specify where to put them. The vintage stuff just has to be taken as it is; custom is for the vintage stuff that works well enough stock to be worthy of a second look.

In any case the amp delivered. This is the best sounding original chassis amp I've heard yet including the Citation II( now a paperweight ). Pretty damn fine for a compact AB1( formerly 2 )design.

Running a pair of Type II KT90's, and GE 6134's I couldn't be happier. Drive is balanced XLR by Neutrik. There were a lot of silly little details to work out. Switched to IEC connector for the AC, dropped the screwey FB scheme originally designed for the amp and fit some 5-way's in. Got a whole lot better handle on idle current with some current shunts and tip jacks in combination with a lot more adjustment range for bias voltage.

The schematic draft was originally done for 6AU6's and a ST.70 and it is in pdf form, so if you want to see it, just ask.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.


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Topic - E-Linear W6m resurrection - PakProtector 15:11:22 10/17/08 ( 6)