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Old 14th October 2010, 12:38 AM   #1
cjcc67 is offline cjcc67  Australia
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Default Hi Performance Pre amp

Greeting fellow DIYers.
After recently acquiring a LOMC cartridge i am using a battery powered head amp before my SRPP preamp .Thanks to Salas for his assistance. The current preamp is the Elektor project from the early 90's.
I thought it might be time to upgrade. I have seen Allen Wrights designs which look quite good. Are there any other high performance designs i should be considering.
I am looking to build both the phono and linestage into a single enclosure.
I am starting with a blank sheet although it would be nice to recycle the HV ( currently 350 & 310V) regulated power supplies from my existing project. The voltage can be lowered but not increased.
I look forward to your suggestions
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Old 14th October 2010, 01:50 AM   #2
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I really dig the aikido


Aikido Amplifier Revisited


But I'm not qualified to make a suggestion past my ears.
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Old 14th October 2010, 11:15 PM   #3
cjcc67 is offline cjcc67  Australia
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Thanks 807
Did i post this question in the wrong forum?
I can see the bench riaa is possible for the phono but will not have enough gain
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Old 15th October 2010, 01:12 AM   #4
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Allen Wright's hybrid cascode allows the use of a LOMC, without a SUT or "head" amp. AW has worked extensively with the 6922. However, that's not the only type that works in a hybrid cascode, with "sand" "downstairs" and a tube "upstairs". The 6GK5, a type I'm impressed by, is an excellent candidate too.

If you truly like your SS head amp, a tweaked version of RCA's "classic" passively equalized design should do nicely. The RCA circuit offers roughly 45 dB. of gain. I've uploaded the tweaked RCA schematic for your consideration.
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File Type: jpg Full Tweaked RCA Phono Stage.jpg (45.4 KB, 650 views)
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Old 5th November 2010, 06:53 AM   #5
cjcc67 is offline cjcc67  Australia
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Thanks Eli. Allens RTP3C looks good if not a little complex. It's on my shortlist along with the current akido/steve bench in another thread. I like the concept of the differential mode of the RTP3 as i'm considering to mate it with the KK 300BPP(P).
Has anybody built the RTP 3 or the KK 300b monos ?
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Old 5th November 2010, 02:36 PM   #6
Alex M is offline Alex M  United Kingdom
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Quote:
Originally Posted by cjcc67 View Post
Thanks Eli. Allens RTP3C looks good if not a little complex. It's on my shortlist along with the current akido/steve bench in another thread. I like the concept of the differential mode of the RTP3 as i'm considering to mate it with the KK 300BPP(P).
Has anybody built the RTP 3 or the KK 300b monos ?
I have a DIY RTP3 which I built from scratch.

I'm not sure what you mean by "KK 300b monos", but I have built Kevin Kennedy's push-pull 300B monoblocks, if that's any use to you...

Alex
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Old 5th November 2010, 10:30 PM   #7
cjcc67 is offline cjcc67  Australia
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Alex I saw your website. That's where I learnt about the monos. Your efforts have inspired me. Did you have a wiring diagram you used in addition to the schematic from the website?
Craig
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Old 6th November 2010, 04:05 PM   #8
Alex M is offline Alex M  United Kingdom
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Hi Craig,

I would definitely recommend the push-pull 300B amp - it sounds great, it has worked flawlessly (apart from a couple of minor problems due to faulty valves) and its differential operation matches my RTP3 well. The only issue with this combination is gain - the RTP3 has a minimum line stage gain of about 10 (3dB), while the 300B amp has a differential gain of 26dB, which is on the borderline of being too high for my 90dB speakers.

No, the layout was entirely my own design, although I did take Kevin's advice to rotate the output transformers to reduce hum. If you decide to build this amp, I would be happy to give you a rough layout plan and a photo or two if that helps.

Alex
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Old 6th November 2010, 05:00 PM   #9
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Originally Posted by Alex M View Post
No, the layout was entirely my own design, although I did take Kevin's advice to rotate the output transformers to reduce hum. If you decide to build this amp, I would be happy to give you a rough layout plan and a photo or two if that helps.
Alex
Hi, Do you mind posting (or e-mailing me) your layout plan? I am especially interested in the correct orientation of the transformers. Are you using the Citation 2 outputs? I have been planning on building this amp for a long time. I think I would use a CF as the driver though as it would have more strength to drive the 300B's.
Thanks again, Daniel
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Old 11th December 2010, 05:17 PM   #10
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, Do you mind posting (or e-mailing me) your layout plan?
Unless you prefer to keep your design confidential, -this can be understood-, I assume that many people on this forum might be interested by working on a preamp able to surpass the AR SP-11...

If you accept to share your knowledge and skematics, we would be happy !
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