john himself told me that they only made 1,000 pairs ("of HP-1000's"), and that it took them three years to sell all of them. however, john has also been noted as saying that the hpa-1 is "basically the same" as the ra-1

Is this true? Has anyone opened up the HPA-1? And are there schematics for the HPA-1? Danke

I could have sworn that I saw the inside of one once, and they were very different than those of the RA-1. I could be wrong, though.

The basic circuit is essentially the same. The HPA-1 has much better build quality, with slightly better parts (caps, resistors, etc.). Whereas the RA-1 has some grain, the HPA-1 is dead smooth. There are of course better options IMO.

I had a real RA-1, nice match with the HF-1. Tamed some of the high end.

So no big changes in the circuit that leads us to believe one amp was tuned for John Grado's and one for Joe's?