Grado ph-1 op amp

[tttubes]

Does any one out there know what op amp is used in the grado ph-1 phono stage.

Thanks

Jim

[planet10]

this may help

dave

[tttubes]

Originally Posted by planet10

this may help

dave

Dave thanks but I think it uses a different op amp but the #s are removed.

Jim

[mhconley]

And the schematic Dave posted is the RA-1 headphone amp, a completely different animal.

Martin

[planet10]

Originally Posted by mhconley

And the schematic Dave posted is the RA-1 headphone amp, a completely different animal.

Oops, i just grabbed the 1st thing that said Grado...

dave

[ahaja]

Njm4556a

[tttubes]

Originally Posted by ahaja

Njm4556a

Thanks that helps alot.

Jim

[uniuniunium]

Originally Posted by ahaja

Njm4556a

Wow. I'm amazed that the schematic I worked up several years ago is still floating around the web. I should say that the NJM4556A spec is largely a guess, based on the fact that they seemed to be using common parts between the PH and RA-1s. That schematic and my subsequent prototype were based on a series of photographs of the amp, but the markings on most of the parts were either smudged or obscured. The IC used on the PH-1 is most definitely a JRC/NJM part, but I couldn't swear that it is the 4556. I think I tested the prototype with a 4556, but I've always used BB OPA2134PAs in practice as they are widely considered to be a superior part.

Cheers,
-Lee

[raypalmer]

Has anyone built this? Is it's RIAA equalization verified?

[kevinkr]

Just to add to the confusion here is an alternative to consider:
http://www.national.com/ds/LM/LM4562.pdf

The LM4562 is both technically and sonically a great performer - should outperform the JRC part even if used in the Grado circuit.

Note that the data sheet shows a design using passive EQ and a couple of 4562 for stereo.

Interestingly enough it is also available in a metal can because in the Asian high end audio market metal canned op-amps are often preferred. (China in particular..) I have metal canned singles from this family that I have not yet tried.