Super simple linestage. [message #9136] |
Sun, 31 July 2005 17:35 |
Thrint
Messages: 43 Registered: May 2009
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Baron |
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For those who don't need any additional gain I ahve an idea. It is even all SS, though the development model is completely valve. One needs a high gm, low input capacitance device to act like a cathode follower. Some pentodes work quite well, but a pair of DN2540 mosfets rigged in cascode as in the Guinevere plate loads is even better. No set resistor is needed. Have this device ride on a goooood CCS. Again the Guinevere plate loads will do well, and this time we *WILL* build the complete thing. Set it to sink 10 mA. Attach the volum pot's wiper to the lower gate, and cap couple from its source( as in Guinevere ). Supply a +/- 60V set of rails and we're off...low output Z, wideband response, and no silly high voltage capacitors needed. For parts, a 120V CT power TX, two 10 Hy/100 mA chokes and two good capacitors are all that's required. Figure $100 max if you don't want a gold-plated box... regards, Douglas
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Re: Super simple linestage. [message #9139 is a reply to message #9138] |
Mon, 01 August 2005 18:11 |
Thrint
Messages: 43 Registered: May 2009
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Baron |
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I did not say that anybody wanted to build this unit. Or that there were no other ways to achieve the results. It is just another way of doing things. If you're sugesting a simple voltage divider pot, the pot and buffer I just laid out ought to run circles around it. Since I have a feeling that there is substantial prejudice against SS stuff, I thought to show a way it could be used to good effect. Always use the best design to solve the problem. Sometimes it might just be a SS one. FWIW, I don't recall anybody complaining about the performance Guenivere delivered. regards, Douglas The suggested PS of 60-0-60 would yeild ~50 volts at the L-C filters.
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Re: Super simple linestage. [message #9141 is a reply to message #9140] |
Tue, 02 August 2005 04:58 |
Thrint
Messages: 43 Registered: May 2009
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Baron |
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I built a similar circuit with tubes, and found it complex to implement. Lots of B+, lots of tubes.... I have most of the parts, and need a proper sized box. I will probably try a remote PS and see how that experiment goes. I have a bunch of photo flash caps salvaged from disposable cameras which have done well in audio circuits to try( they're small 330VDC/160 uF ). It is interesting enough, being completely SS to try IMO. There is a certain satisfaction to be gained in favourably comparing to something far more expensive and Off-the-Rack, no? regards, Douglas
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