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items: 4-transistor linestage
items: Re: 4-transistor linestage
items: and an option

4-transistor linestage
type: item
description: OK, back to the MOSFET cascode buffer. Some nice cascode properties: very low input capacitance. THe lower device is screened by the upper, and it ( globally ) is acting as a buffer/source follower. Instead of rigging the lower gate to the current set resistor( as in a CCS ), it is the input from the volume control. Current is regulated by a full-circuit CCS on a negative rail. +/- 25 volts should be adequate. 5-10 uF of coupling cap, and at low voltage. Always wandered what a good L-C filter in a SS amp's power supply would do. Of course, we'll need two of them for the bi-polar rails. Of course, we'll do rectification with vacuum diodes, preferably IDH cathodes, like 6AX4's. The trouble is that my sleeve of DN2540N5 MOSFET's dissappeared in my move....:( along with my coffee can full of salvaged photo flash caps from disposable cameras. regards, Douglas
creator: Thrint
date: 2005-08-17T23:54:22-00:00

Re: 4-transistor linestage
type: item
description: I'd love to build one. As for the MOSFETs and caps, did your wife help you "pack?"
creator: colinhester
date: 2005-08-18T00:12:44-00:00

Re: 4-transistor linestage
type: item
description: Man T; you hop around more than a flea on a griddle. Whats with this SS stuff now; are you trying to experiment or is this something you heard that had a great sound? I admitt, I am baffled. People have to have reasons for why they do stuff.
creator: Manualblock
date: 2005-08-18T18:52:34-00:00

Re: 4-transistor linestage
type: item
description: The SS plate load sounds good. A few have asked me about unity gain linestages. Some of my friends have TX linestages. I think the buffer is a critical part of the job. Sooooo, how simple can it get? The cascode is a complication, but it gets around the variable capacitance induced by varying D-S voltage, and G-D voltage. Partially, it is an experiment to take something which is not 'supposed' to sound good and demonstrate the conventional wisdom isn't so wise afterall. Like PP Pentodes, no? regards, Douglas
creator: Thrint
date: 2005-08-19T23:38:36-00:00

Re: 4-transistor linestage
type: item
description: Boy that is some can of worms you are opening there. But I am not the right guy to discuss this; I still think the Dyna ST 70's sound pretty good. My favorite amp sound so far is the Fisher 50AZ and the Threshold Class A transistor amps.
creator: Manualblock
date: 2005-08-20T18:42:14-00:00

and an option
type: item
description: Hey-Hey!!!, I am exploring a 1:1 bifilar output TX for this beastie. It will also serve to bias it. No second CCS required. Intact audio is the likely winder of these OPTx's. Bit of a research project I think. Requires a better filter for the negative rail( and a lot smaller voltage too). regards, Douglas
creator: Thrint
date: 2005-08-22T21:45:15-00:00