I am looking at the Accuphase P-7100 and A-65 schematic and notice something of interest which I felt I wanted to ask about.
I have attached some pictures down bellow for your convenience. Looking at the attached picture with the schematic section of the P-7100 and A-65, I want you to look at the driver section of both schematics.
We are looking at positive voltage side only. I want you to pay attention to the constant current driver of the P-7100: Q28 2SC4793 driver to Q34 2SC5354 which is a power BJT. If you then look at the A-65,
here they cascade two 2SC4793 drivers. Since I don't have the P-7300 schematic, I had to use the available pictures to see if I could determine how many driver pairs the P-7300 use.
The P-7100 uses 1 driver pair + power BJT on the constant current section and 11 paralleled power BJT's.
The P-7300 uses 2 drive pairs and 10 paralleled power BJTs
The A-65 uses 2 drivers pairs and 10 paralleled power FET's
The A-70 uses 2 driver pairs and ...
The A-75 uses 2 driver pairs and ...
(1 driver pair consist of 1 pcs 2SC4793 (NPN) and 1 pcs 2SA1837 (PNP).
Amp release date:
A-65: 2009-2014
A-70: 2015-2019
A-75: 2019-
P-7100: 2006-2014
P-7300: 2015-
From my perspective, it looks like 2008/09 when the A-65 was released, that they did an overhaul or upgrade on the constant current section which was then used moving forward.
Wouldn't it be possible to adapt this newer 2 driver pairs on P-7100 and give it an upgrade ?
(If you want to see the whole schematic, you have to locate this on your own since sharing official schematics on diya.com that is not pre-approved is frowned upon)
I have attached some pictures down bellow for your convenience. Looking at the attached picture with the schematic section of the P-7100 and A-65, I want you to look at the driver section of both schematics.
We are looking at positive voltage side only. I want you to pay attention to the constant current driver of the P-7100: Q28 2SC4793 driver to Q34 2SC5354 which is a power BJT. If you then look at the A-65,
here they cascade two 2SC4793 drivers. Since I don't have the P-7300 schematic, I had to use the available pictures to see if I could determine how many driver pairs the P-7300 use.
The P-7100 uses 1 driver pair + power BJT on the constant current section and 11 paralleled power BJT's.
The P-7300 uses 2 drive pairs and 10 paralleled power BJTs
The A-65 uses 2 drivers pairs and 10 paralleled power FET's
The A-70 uses 2 driver pairs and ...
The A-75 uses 2 driver pairs and ...
(1 driver pair consist of 1 pcs 2SC4793 (NPN) and 1 pcs 2SA1837 (PNP).
Amp release date:
A-65: 2009-2014
A-70: 2015-2019
A-75: 2019-
P-7100: 2006-2014
P-7300: 2015-
From my perspective, it looks like 2008/09 when the A-65 was released, that they did an overhaul or upgrade on the constant current section which was then used moving forward.
Wouldn't it be possible to adapt this newer 2 driver pairs on P-7100 and give it an upgrade ?
(If you want to see the whole schematic, you have to locate this on your own since sharing official schematics on diya.com that is not pre-approved is frowned upon)
Attachments
Explain ?
The drivers have a transition frequency of 100MHz (2SC4793 NPN) and 70MHz (2SA1837 PNP). How can one amplifier be stable with such a cascade pair and the other not ? .. they use similar circuit architecture.
