Accuphase clone

[bra]

It is time to klone another great amplifier. I think Accuphase has many fantastic amps but it is very few schematics available. And for me best is this one from Chinese site:

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[lgreen]

Not again!

Which one is this and what are the specs?

[Luke]

is this really the accuphase schematic, any one know what model?

[john-china]

i can confirm this is not real accuphase schematic. it is modified by some chinese from accuphase prototype in public manual.

[PhaseLockLoopy]

The front end is typical of their symmetry in design and the they do send the feedback through an opamp, which when I tried that it does correct some non-linearties but at the cost of noise.

Here's Accu's E210 for comparison

[h_a]

Various classic Accuphase schematics are available at Jan's site

Welcome to Audio Circuit Denmark

The accuphases are pretty complicated and a clone would certainly need a prototype and tweaking for modern parts.

Have fun, Hannes

[bra]

These old schematic are not interesting for me, I would like to build clone of P350, P370, P450, P550, P650 or P700. They are based on same topology and are "quite simple". But where to find real schematic? Maybe this chinese schematic is get from real amplifier?

[tiefbassuebertr]

Originally Posted by PhaseLockLoopy

The front end is typical of their symmetry in design and the they do send the feedback through an opamp, which when I tried that it does correct some non-linearties but at the cost of noise.
Here's Accu's E210 for comparison

Check out the URLs by post #11 and #16 about
MJ Magazine (formerly Musen to Jikken) - Yearly Index from 1924 - 2009 wanted
concerning feedback through an opamp
For the aim of diy I would not choice the Accuphase topology and no other mirror symmetry circuit topology, because particulary by this topology the demand for high coincidence between the positive and negative half is very high. Because I haven't conditions like a circlotron (CSPP), the residual differences are too large, because NPN and PNP devices only in the schematics itself have a nice symmetrc behaviour.
Much more better results without horrible selection of transistors of the voltage gain stages you will get with Lavardin's topology or with that one from Renardson (MJR-Amp)
http://peufeu.free.fr/audio/memory/m...-complete.html
http://www.angelfire.com/ab3/mjramp/amp8.html

[godfrey]

Originally Posted by bra

Maybe this chinese schematic is get from real amplifier?

Maybe, maybe not...
The circuit in your first post has nothing to ensure high frequency stability. That does not look good.

[Bonsai]

"The front end is typical of their symmetry in design and the they do send the feedback through an opamp, which when I tried that it does correct some non-linearties but at the cost of noise."
No, the op amp is to servo out any DC offset. R14//R15 set the main amp gain.

This is a current feedback topology amplifer ('CFA') -Accuphase like CFA because of they generally have less phase distortion and wider bandwidths than VFA amps. They use CFA in their line preamp stages as well.

The first circuit has a few idiosyncracies - I'd avoid it - clearly whoever is trting to copy the Accuphase has pretensions of being an audio amp designer but seem to have wandered off the track a bit. The second one looks more like an Accuphase. I like their products and they are very well engineered - great sounding and looking stuff.