I think it is time to start new thread.
Maybe someone want to clone great Nakamichi PA7?
I do. I have service manual but I have to scan.
Maybe someone want to clone great Nakamichi PA7?
I do. I have service manual but I have to scan.
New amp
Bra
Bring it on, scan it and publish it, we are all anxious to see new amplifiers, enough of those beaten ones in other threads.
Thanks
Bra
Bring it on, scan it and publish it, we are all anxious to see new amplifiers, enough of those beaten ones in other threads.
Thanks
Schematics
Amplifier (one channel) 362k TIFF
Power Supply 156k TIFF
Unfortunately I only have a rather poor quality copy of the service manual, so some of the text is not readable.
Amplifier (one channel) 362k TIFF
Power Supply 156k TIFF
Unfortunately I only have a rather poor quality copy of the service manual, so some of the text is not readable.
Thanks oPossum,
That's the beast. There is still the mod PCB for the current limiter we need to find.
If the text were more clear .... Can you scan the main PCB to give others an idea of the size? 14 outputs per channel doesn't seem to convey the idea like a picture.
-Chris
That's the beast. There is still the mod PCB for the current limiter we need to find.
If the text were more clear .... Can you scan the main PCB to give others an idea of the size? 14 outputs per channel doesn't seem to convey the idea like a picture.
-Chris
You know, I'd like to have some input from N P on this. Maybe not his design, but it's his concept. Nelson may have some cool ideas.
-Chris
-Chris
This design has a characteristically poor HF PSRR so you will be listening to PS artefacts so best to eliminate those half wave Class AB ones in the most inelegant way possible - by wasting power running such a monster in Class A.
This type of dinosaur will be the first to go in the dawning of the new era of energy efficiency. RIP.
Cheers,
greg
This type of dinosaur will be the first to go in the dawning of the new era of energy efficiency. RIP.
Cheers,
greg
Hi Greg,
Have you had a chance to hear or test these amps? Just curious.
What you say might be true, but they sound very smooth. The front end looks well isolated from the supplies. No worse than many others and better than some.
The outputs were run warm because they are not in the feedback loop and needed to be run in a more linear part of their curves - Stassis you know. I can think of a few other amps that ran at least as warm as a normal A/B with everything in the feedback loop.
True, they are not as efficient as most other amps, I'll give you that.
-Chris
Have you had a chance to hear or test these amps? Just curious.
What you say might be true, but they sound very smooth. The front end looks well isolated from the supplies. No worse than many others and better than some.
The outputs were run warm because they are not in the feedback loop and needed to be run in a more linear part of their curves - Stassis you know. I can think of a few other amps that ran at least as warm as a normal A/B with everything in the feedback loop.
True, they are not as efficient as most other amps, I'll give you that.
-Chris
Hi anatech,
It uses a typical (albeit cascoded) diff'l input followed by a high gain Vas and miller comp which kills HF PSRR so it needs clean supplies to sound any good. Class A does that (and linearises the outputs). There are far more elegant ways of achieving the ends without resorting to Class A.
I don't see any surprises here - nothing to hunt one down to audition. It should sound smooth - I guess because it faces none of the hard challenges but sidesteps them with Class A.
This is Sooo characteristic of the monster amps that solve nothing really well and can be easily blown away with a sweet little low bias Class AB 1/10th the size.
I guess what really irks me about such products is that they perpetuate the myth that this is necessary to achieve audio nirvana when all it really does is salve small appendage syndrome or a need for excess, neither of which I believe in.
Cheers,
It uses a typical (albeit cascoded) diff'l input followed by a high gain Vas and miller comp which kills HF PSRR so it needs clean supplies to sound any good. Class A does that (and linearises the outputs). There are far more elegant ways of achieving the ends without resorting to Class A.
I don't see any surprises here - nothing to hunt one down to audition. It should sound smooth - I guess because it faces none of the hard challenges but sidesteps them with Class A.
This is Sooo characteristic of the monster amps that solve nothing really well and can be easily blown away with a sweet little low bias Class AB 1/10th the size.
I guess what really irks me about such products is that they perpetuate the myth that this is necessary to achieve audio nirvana when all it really does is salve small appendage syndrome or a need for excess, neither of which I believe in.
Cheers,
Hi Bra,
Are all these parts available in your country? Why would you choose such a dinosaur to copy when it can easily be seen off by inspired Class AB design, a handful of BC546/556 and some everyday output MOSFETs.
It's Kitsch value??
Cheers,
Greg
Are all these parts available in your country? Why would you choose such a dinosaur to copy when it can easily be seen off by inspired Class AB design, a handful of BC546/556 and some everyday output MOSFETs.
It's Kitsch value??
Cheers,
Greg
I want to use parts from onsemi (samples) if it is possible. It is AB design - idling current is only 40 mA per one transistor.
Personally i would love to see the entire service manual (I know someone with a pa7).
Any chance of getting a scan of the whole thing ?.
Will give you my email addy if you like.
This friends PA7 responded very nicley to me replacing al power supply wiring with heaveir gauge.
Any chance of getting a scan of the whole thing ?.
Will give you my email addy if you like.
This friends PA7 responded very nicley to me replacing al power supply wiring with heaveir gauge.
just want to make clear:
is there no global negative feedback fo the said amp?
or is it already the one that is through a trimmer res. from the pre-driver with vbe multiplier
stages?
rgds,
hienrich
is there no global negative feedback fo the said amp?
or is it already the one that is through a trimmer res. from the pre-driver with vbe multiplier
stages?
rgds,
hienrich
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