Just simmed it. If everythings seems OK, I will build it. Most of SMD's I ordered today afternoon.
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Egra, if you're interested in further modifying AX11 (including all of its numerous derivatives), take a look at Harman Kardon AVR series of amplifiers (AVR230, AVR7300, AVR7550HD, etc.) They are all using a slightly improved version of the old Sansui topology that was used as a basis for AX11.
I may have missed this, but what should the quiescent bias current on the FX8 be set at for optimal performance? Is higher better?
Thanks xrk! 120-170mA seems optimal., but shaan's new PeeCeeBee (V2) runs with much lower quiescent current. 30mA (or similar value) with excellent result. Nevertheless choosing such low bias current you can easily reach the positive tempco area of FEts, which seems to be suboptimal. Not to mention the increased high-order harmonic distortion. If I remember correctly G. Randy Slone is the only one who suggests such low quiescent current for LATFETs (without any explanation). So worth to try so low Iq. I am inclined to keep the LATFETs bias current (and temperature) relatively high, because these devices really like running warm. See Goldmund Telos and Mimesis amplifiers (OEM) or Lazy Cat's First One amp. He set the Iq somewhere between 200 and 300 mA per device.
Thank You mrmax063! The manual is a great opportunity to study the circuit and the PCB layout as well. The manual says: Transient Intermodulation Distortion (TIM) Unmeasurable. Wow!
A few weeks ago I heard a system in a party: PC->USB DAC->Pioneer A30->Wharfedale floor standing speakers. The system sounded excellent. BTW a bit too bright to my taste but surprisingly smooth and dynamic. Few days ago found out that Pioneer uses similar Pure Push-Pull VAS topology... 🙂
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I think Terry and Mr. Mile stated that it still sounds great with 70-75mA and runs cooler.
I don't hear any difference between 100mA and 70mA, nor do I see anything on the scope. Maybe if you push it loud enough you could hear some crossover distortion but I didn't hear any. My JBLs are very loud so I don't ever drive them to clipping.
Egra
add a series R to C6.
You can trim the R for best squarewave shape.
Try a 50k or 100k VR as a start.
Then replace with a fixed R value.
add a series R to C6.
You can trim the R for best squarewave shape.
Try a 50k or 100k VR as a start.
Then replace with a fixed R value.
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Pioneer's latest series of budget priced amps - A10, A20 - also use old Sansui topology (AU217, AU317) like AX11. As somebody already mentioned small overshoot on high frequency square wave probably won't be problem with real world speaker cables that are slightly inductive.
Thanks for the schematic. Is this a Pioneer or the Sansui, and which one? Looks like a nice design. I have never seen a bypass cap on one leg of the LTP before.
That looks real nice, would anyone happen to have a SPRINT or Gerber files for it (50mm x 50mm would be sweet).
It is simple enough for p-2-p on a perf board but would be so much cleaner on a custom PCB.
Thanks.