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Old 1st March 2010, 01:36 AM   #1
tttubes is offline tttubes  United States
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Default Grado ph-1 op amp

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

Thanks

Jim
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Old 1st March 2010, 01:54 AM   #2
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this may help

dave
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Old 1st March 2010, 11:46 PM   #3
tttubes is offline tttubes  United States
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Originally Posted by planet10 View Post
this may help

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

Jim
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Old 5th March 2010, 11:44 PM   #4
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And the schematic Dave posted is the RA-1 headphone amp, a completely different animal.

Martin
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Old 5th March 2010, 11:55 PM   #5
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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
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Old 6th March 2010, 12:17 AM   #6
ahaja is offline ahaja  Poland
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Njm4556a
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Old 6th March 2010, 01:24 AM   #7
tttubes is offline tttubes  United States
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Njm4556a
Thanks that helps alot.

Jim
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Old 7th March 2010, 01:08 AM   #8
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Quote:
Originally Posted by ahaja View Post
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.

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-Lee
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Old 19th May 2011, 03:03 PM   #9
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Has anyone built this? Is it's RIAA equalization verified?
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Old 19th May 2011, 04:40 PM   #10
kevinkr is offline kevinkr  United States
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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.
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