Babelfish F8

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#384
I was comparing the XA252 to the Babefish F8 tonight and noticed I had hum in both speakers when I put my ear to the driver. So just for fun I thought I would try what MEPER did and bypass the GBR, guess what, this amp is now the quietest amp in my collection. Of course your milage may very but it worked for me.

The 2 amps definitely have their own sound. To me the F8 sounds more focused and a bit softer in the treble, images slighty better than the XA252. Both amps tested with Iron Pre and Miro's ad1862 dac.
 

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#386
Zen Mod said:
now, there's a trick; Herr Schade never had intention as we are having now - using his name and tricks to mimic triode with non-triode-like part ........ his tricks were made for bettering entire circuit, in most cases much better than simply changing parts in no-nfb circuit and hoping for best; I mean, guy was a Scholar and Engineer, for start :clown:

as a matter of fact, any sort of feedback is in general changing transfer function of entire circuit in a way that it can easily resembles having triode in circ, even if there is not one

so ............ call it as you like, but I confess that my predetermined and twisted mind first acted thinking - wtf is now with making triode more triode ...... using Schade feedback on SIT part

anyhow, if you like it, go for it!
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The 'interesting part' is that I was en route to make FB on my choke loaded. I cannot get that stable with this driver hanging on the choke and further the same way: up till now the driver is very overdriven. I'll forget that idea. I'll go for a common drain (the 2SK182-common source is nice very warm on a horn for dinner but did not eat Maggies for breakfast).
I will never go so far as to say that the driver I made for the 2SJ28 VFET MU-build has a Schade feedback (dass ist schade, nicht).

But as to use a compound single stage feedback in a MU-follower, yes that gave a surprising good effect on paper.
Indeed, the feedback in two cascoded mosfets (for example the RA7 preamp) is something different from this; an original type of this feedback of a SRPP with screen feedback on bottom pentode is known to me, perhaps this is an old Philips design:
tempImageM01upR.gif
 
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#398
Thanks for the comments.

Big thanks to Zen Mod, for the design, Mark Johnson for the Amy Alice SMPS filter boards and Cap mx circuit and member birdbox for the great wiring diagram using twin SMPS with 4 filter boards for dual +/- supplies.
 
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#400
^ Don't celebrate too much yet. I'll be using donuts. Probably even two of them. I bet they will have fancy little matching 3D printed seats made up especially for the pair. I just am on hold for a very special package to arrive from a far away place :rofl:
 
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