Audio Research SP3a

mr2racer58 · 15th June 2010, 01:46 AM

Hey everyone! Does anyone have any information on mods for the SP3a preamp?

jackinnj · 15th June 2010, 02:57 AM

If you're not careful, it'll become an SP-8.

mr2racer58 · 7th July 2010, 11:39 PM

I spoke with Calvin at AR and he told me he couldn't sell me the new power supply I wanted. Only the complete upgrade done by them. On another thread you said you had some caps for an AR power amp. What about the caps for the SP3a?

planet10 · 8th July 2010, 01:06 AM

I built an SP3a clone in the mid 70s (sold them too). Very nice chassis. The best mod would be to strip it and start over....

It is a classic thou.

mpbarneyamps: audioresearchsp-3preamp
http://www.curcioaudio.com/SP-3%20Mo...umentation.pdf
ARCDB - SP-3

dave

kevinkr · 8th July 2010, 01:16 AM

Quote:

Originally Posted by planet10

I built an SP3a clone in the mid 70s (sold them too). Very nice chassis. The best mod would be to strip it and start over....

<snip>

dave

I too made that mistake in the late 1980s..

FWIW I agree with Dave, probably pass this along to a collector and build yourself an Aikido, one of mine, or anything else you fancy..

The design and its performance really leaves a lot to be desired by today's standards. And I'm NOT trying to be mean.. I was very disappointed.

jackinnj · 8th July 2010, 01:21 AM

Second the notion of passing it along to a collector -- they fetch quite a nice price.

I built one from scratch when TAA printed the schematic sometime in the late 1970's -- the Delco pass transistors cost more than a few NYC subway tokens back then!

mr2racer58 · 8th July 2010, 01:43 AM

I'm not really an expert at electronics. (I'm actually a car mechanic.) I just finished rebuilding my old Dynaco Mark VI's. I mean yesterday was the first time I could listen to both amplifiers. I simply can't afford to give AR $1300 to upgrade the preamp. I did replace the coupling caps with Solen polypropylene ones. That seemed to help. I'm also told that the slight harshness in the upper midrange lower high frequencies is caused by the nickle plated RCA jacks. Does that sound plausible? I've ordered gold plated ones.

I looked at the Aikido. Do you really think it would be better to start from scratch? In that case what I would like is a really sweet sounding tube preamp kit. With an input for my CD player and a phono preamp. An on/off switch and a volume control and nothing else. Is there such a kit? At a reasonable cost?

planet10 · 8th July 2010, 01:55 AM

I have little doubt even an RCA phono (as modded by Eli) followed by a 12B4 (or an ECC88 CC DC coupled to CF -- you'll find that buried in the SP3A) would smoke the SP3A.

How good it can be comes down to power supply execution and how well matched you can get the EQ in the RIAA.

And there are lots of other great choices.

dave

mr2racer58 · 8th July 2010, 02:06 AM

I know ECC88 is a tube. But, ...CC DC coupled to CF? (Betraying my ignorance?)

planet10 · 8th July 2010, 02:22 AM

Common Cathode DC coupled to Cathode Follower.

Here. Snipped from the SP3A schema... be better with a CCS (constant current source) on the bottom of the CF.

(ECC88 = 6DJ8)

dave

15th June 2010, 01:46 AM	#1
mr2racer58 diyAudio Member Join Date: Jan 2010	Audio Research SP3a Hey everyone! Does anyone have any information on mods for the SP3a preamp?

8th July 2010, 01:06 AM	#4
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	I built an SP3a clone in the mid 70s (sold them too). Very nice chassis. The best mod would be to strip it and start over.... It is a classic thou. mpbarneyamps: audioresearchsp-3preamp http://www.curcioaudio.com/SP-3%20Mo...umentation.pdf ARCDB - SP-3 dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

8th July 2010, 01:55 AM	#8
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	I have little doubt even an RCA phono (as modded by Eli) followed by a 12B4 (or an ECC88 CC DC coupled to CF -- you'll find that buried in the SP3A) would smoke the SP3A. How good it can be comes down to power supply execution and how well matched you can get the EQ in the RIAA. And there are lots of other great choices. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

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15th June 2010, 02:57 AM	#2
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	If you're not careful, it'll become an SP-8.

7th July 2010, 11:39 PM	#3
mr2racer58 diyAudio Member Join Date: Jan 2010	I spoke with Calvin at AR and he told me he couldn't sell me the new power supply I wanted. Only the complete upgrade done by them. On another thread you said you had some caps for an AR power amp. What about the caps for the SP3a?

8th July 2010, 01:21 AM	#6
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Second the notion of passing it along to a collector -- they fetch quite a nice price. I built one from scratch when TAA printed the schematic sometime in the late 1970's -- the Delco pass transistors cost more than a few NYC subway tokens back then!

8th July 2010, 01:43 AM	#7
mr2racer58 diyAudio Member Join Date: Jan 2010	I'm not really an expert at electronics. (I'm actually a car mechanic.) I just finished rebuilding my old Dynaco Mark VI's. I mean yesterday was the first time I could listen to both amplifiers. I simply can't afford to give AR $1300 to upgrade the preamp. I did replace the coupling caps with Solen polypropylene ones. That seemed to help. I'm also told that the slight harshness in the upper midrange lower high frequencies is caused by the nickle plated RCA jacks. Does that sound plausible? I've ordered gold plated ones. I looked at the Aikido. Do you really think it would be better to start from scratch? In that case what I would like is a really sweet sounding tube preamp kit. With an input for my CD player and a phono preamp. An on/off switch and a volume control and nothing else. Is there such a kit? At a reasonable cost?

8th July 2010, 02:06 AM	#9
mr2racer58 diyAudio Member Join Date: Jan 2010	I know ECC88 is a tube. But, ...CC DC coupled to CF? (Betraying my ignorance?)

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