Between ZEN4 and ALEPH30

[Skorpio]

Having almost desided on ZEN4, but not liking the input buffer circuit (but prefering it to the low input impedance of pre-ZEN4 types)either the output capacitor...but in general liking the idea.....but also doubts about the active current sourse?

...until I saw the ALEP30 schematic.

Then the questions:

1) The ALEPH is a commercial design, is this the reason for multiple output devices and short-circuit protection?

2) No PSU regulator on ALEPH due to better input stage PSRR?

3) Can I build ALEPH Circuit with ZEN4 output stage (only 1 pair of output devices)?

4) Can I switch to passive CCS but adding a switch in series with C10? And can the switch be operated while amp is playing without problems?

5) Active CCS, does that mean that you can get more power to the load than the single ended class A normally says? A form of single ended A/B?

 

[Nelson Pass]

1) The ALEPH is a commercial design, is this the reason for multiple output devices and short-circuit protection?

2) No PSU regulator on ALEPH due to better input stage PSRR?

3) Can I build ALEPH Circuit with ZEN4 output stage (only 1 pair of output devices)?

4) Can I switch to passive CCS but adding a switch in series with C10? And can the switch be operated while amp is playing without problems?

5) Active CCS, does that mean that you can get more power to the load than the single ended class A normally says? A form of single ended A/B?

1) The Zen has no need of short protection, but the Aleph
negative stage could potentially draw too much current driving
a grounded output

2) Yes, but the Aleph benefits from CRC or CLC filtering

3) Yes, but it runs hotter for each device

4) Yes, but you are very likely to get a big thump when you
switch it during operation

5) Active CCS (the Aleph current source, specifically) allows
more output current, usually about double, and is intended
for Class A operation in a manner similar to an SRPP circuit.
It raises the efficiency of the amplifier to about 30% or so,
up from about 15% or so.

 

[Skorpio]

Thank you for theese answers, it is a unique situation to be able to puzzle with you DIY versions and then get support from the manufacturer!

During my preparing for my 'ALEPH30 Minor´ I have been digging in the schmatics and this has generated some follow up questions:

1) In the ALEPH3 (older version of A30?), the decoupling between the two 1.5k resistors are returned to output terminal. In the A30 it returns to the junction between the output MOS-FETs. Why the difference?

2) The A30 has a 10pF capacitor across the 10k feedback resistor. The A3 has a 10nF between GD of the output device. Why the difference?

3) The active CCS sence resistor is also different, 820R for A30 and 750R for A3. For equal output these resistors should be equal, or?

My guess is the the newer A30 has been optimized is some areas, and are therefore a better target for DIY?

4) Regarding PSRR on input, is the 392R resistor now the limit? If so could the input CCS be replaced with a 1K resistor? I don't think this will affect DC-stability?

5) Would you recomend parallel output devices as increased heatsink sizing? We are talking 1 set of outputs on largest sheatsink or 2 sets on smaller?

 

[Nelson Pass]

1) In the ALEPH3 (older version of A30?), the decoupling between the two 1.5k resistors are returned to output terminal. In the A30 it returns to the junction between the output MOS-FETs. Why the difference?

2) The A30 has a 10pF capacitor across the 10k feedback resistor. The A3 has a 10nF between GD of the output device. Why the difference?

3) The active CCS sence resistor is also different, 820R for A30 and 750R for A3. For equal output these resistors should be equal, or?

My guess is the the newer A30 has been optimized is some areas, and are therefore a better target for DIY?

4) Regarding PSRR on input, is the 392R resistor now the limit? If so could the input CCS be replaced with a 1K resistor? I don't think this will affect DC-stability?

5) Would you recomend parallel output devices as increased heatsink sizing? We are talking 1 set of outputs on largest sheatsink or 2 sets on smaller?

1) Arbitrary decision

2) see #1

3) each design uses a different resistor value for the same gain

4) 392R is chosen to match the input bias against the bias
needs of the output Mosfet. It does not particularly affect the
PSRR

5) each design has an optimal number of output devices,
depending on what characteristic you want to emphasize