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In Reply to: RE: Schematic: A Lockin GU50 Push Pull Amplifier. posted by Spantou on October 04, 2020 at 18:34:14
I realize that this amp is assembled using several modules that are proprietary circuits, but I shall appreciate as much building information as could be made available.
Follow Ups:
Hi Spantou,Thank you for your compliments. I am indeed delighted with the sound of this amplifier.
As amplifier design gets better I guess then they all begin to sound more alike. This design manages to have a more low noise, bass control of solid state the imagining & depth of single Ended & the frequency response extension of push pull. So what's not to like then. Some listeners prefer the older more euphonic rounder & warmer sound of traditional Tube amplifiers. This is definitely in the more high resolution precision, accurate camp and not warm & cuddly.
There was never a set schematic just some ideas gleamed from other amplifier designs. I am sure that you will also make an amplifier your own by the build choices you take just as I did and the parts you already have in your personal parts bin. I could hand draw my final schematic for you if you wish but I think it more useful to show you what influenced me in my current design. I hope this helps.
This is my original inspiration schematic I am sure that you can see how I added K & K Audio front end to the IT and adapted this for use with the 6E6P driver stage at 200v/22ma. I used Kevin's Cascode CCS with a well-regulated -25volts underneath. Be careful with 6E6p/6E5p/6J11p/DA3 they will oscillate given a chance, grid & screen stoppers essential.
To be honest if I was starting again with a blank canvass for a new amplifier I would very strongly consider using Kevin's 6J49p push pull boards plus power supply, with a Lundahl LL1692a IT. (See Kevin's blog page and KT150 PP amp circuit for inspiration) This combination has the balanced driver stage topology I like, then add the output valves of your choice.(Gu50 inexpensive and good choice) It all depends on you construction choices, budget & if you want all PCB or you like point to point wiring. Then add the Van de Veen bias board and E Chokes.
I am sure you have already researched these modules and know what they do & there advantages, they are indeed a very potent combination. You could also do a D H T version but I guess you will struggle with the noise element.
The voltage regulator on the IT could be solid state or tube, there are many 6EM7/6GF7 based one tube regulators on the net or others tubes. Or perhaps one of Kevin's Shunt Regulators, Morgan Jones Statistical regulator looks very interesting also. However solid state regulators will add more solid state sound characteristics!
So many choices I guess that's what makes our hobby so interesting. Good Luck.
Stay well
Keep Sharing.
Tubelcain.
Edits: 10/06/20
Tubelcain,
Thanks very much! This is just what I had hoped for.
Happy listening,
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