Favorite op-amps for RIAA preamp? - Page 4

andyjevans · 18th June 2008, 01:07 AM

Seems like several of you had good projects going. What results did you get with the new National preamps, and can you share circuit ideas?>>

You got me going now. I have built the circuit on page 12 of the LT1115 datasheet.

Can I improve on this circuit using the National preamps referred to e.g. the LME49710 which is described as "near to perfect"...

Andy Evans

leadbelly · 18th June 2008, 01:24 AM

IME a cheap FET input opamp will beat these pricey National chips because it loads the cartridge much less, which is a big deal with my Grado.

andyjevans · 18th June 2008, 01:28 AM

I should say that I use a Audio Tehnica OC7 moving coil cartridge, so in my case I'm optimising for MC.

I guess the Grado is MM?

leadbelly · 18th June 2008, 01:53 AM

Quote:

Originally posted by andyjevans
I guess the Grado is MM?

Yes

KBK · 20th August 2008, 06:03 AM

I just rebuilt a Bluenote brand phono box for someone.
It sounded so good..that the owner of that unit gave me his Chord balanced phono pre, in return.

it is full of OPA27 opamps.

OPA627? Sounds about right.....

KBK · 20th August 2008, 06:09 AM

Quote:

Originally posted by Conrad Hoffman
Ok, fixed some grounding issues and reduced the hum a bit. What I really need to do is ditch my power supply and build something with a toroid, or just go battery power. Never thought it would matter, but at this level it does. Going through an inverse RIAA box, the THD+N is about 0.007% @ 1khz. My guess is it's mostly N, not THD. Spent most of the afternoon listening to LPs, and the sound is still very pleasing. I re-recorded (digital) some tracks that I had also done with the old preamp, and compared them. The differences are real, mostly the improvement in the high end- more shimmer and musical, than HF noise, but it's subtle. Still have to pull the board out and change the caps.

A slightly rude sounding question: Are you using at least polystyrene bypass caps, right at the pins, on the OPA627? It makes a quite notable difference.

I'm thinking my current work will need something like this Johnson noise analyzer. (I thought Johnson noise was something that happened when.....nevermind)

Do folks feel this is a workable device?

Edit: Ok. will investigate the national chips.

vaughst · 9th November 2008, 12:27 AM

Hi all

I am using a modified Rotel RQ970 as HiFi World mods from the 90's. The design used AD743, now unobtainable in the UK i have tried both AD 797 and LT1028, with reasonable results.

I am using a DL160, hi output MC, shoud I consider this to be a MM or MC from the standpoint of Op Amp selection?
THanks

mlloyd1 · 9th November 2008, 12:49 AM

i'd also recommend at least trying the AD743 as a front end for a mm riaa preamp.
maybe can buy direct from AD? i thought they were still making this part ...

i just got some OPA827 and OPA211 which I've heard good things about. i would consider the OPA827 for the front end of a mm riaa preamp.

personally, i also like the opa627, but they are expensive and probably too old for some people's taste ...
:-)

mlloyd1

18th June 2008, 01:24 AM	#32
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	IME a cheap FET input opamp will beat these pricey National chips because it loads the cartridge much less, which is a big deal with my Grado. __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

20th August 2008, 06:03 AM	#35
KBK diyAudio Member Join Date: Dec 2003 Location: The Wilds Of Canada	I just rebuilt a Bluenote brand phono box for someone. It sounded so good..that the owner of that unit gave me his Chord balanced phono pre, in return. it is full of OPA27 opamps. OPA627? Sounds about right..... __________________ "Never forget that only dead fish swim with the stream." -- Malcolm Muggeridge. "Truth cannot be brought down, rather the individual must make the effort to ascend to it." -- Jiddu Krishnamurti

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18th June 2008, 01:07 AM	#31
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	Seems like several of you had good projects going. What results did you get with the new National preamps, and can you share circuit ideas?>> You got me going now. I have built the circuit on page 12 of the LT1115 datasheet. Can I improve on this circuit using the National preamps referred to e.g. the LME49710 which is described as "near to perfect"... Andy Evans

18th June 2008, 01:28 AM	#33
andyjevans diyAudio Member Join Date: Sep 2003 Location: London	I should say that I use a Audio Tehnica OC7 moving coil cartridge, so in my case I'm optimising for MC. I guess the Grado is MM?

9th November 2008, 12:27 AM	#37
vaughst diyAudio Member Join Date: Dec 2001 Location: Oxfordshire UK	Hi all I am using a modified Rotel RQ970 as HiFi World mods from the 90's. The design used AD743, now unobtainable in the UK i have tried both AD 797 and LT1028, with reasonable results. I am using a DL160, hi output MC, shoud I consider this to be a MM or MC from the standpoint of Op Amp selection? THanks

9th November 2008, 12:49 AM	#38
mlloyd1 diyAudio Member Join Date: Feb 2001 Location: illinois	i'd also recommend at least trying the AD743 as a front end for a mm riaa preamp. maybe can buy direct from AD? i thought they were still making this part ... i just got some OPA827 and OPA211 which I've heard good things about. i would consider the OPA827 for the front end of a mm riaa preamp. personally, i also like the opa627, but they are expensive and probably too old for some people's taste ... :-) mlloyd1

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