RIAA phono preamp using single ECC83 - diyAudio
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Old 28th March 2003, 10:56 PM   #1
DJG is offline DJG
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Default RIAA phono preamp using single ECC83

Hello!

I just bought two ECC83 and now I'm looking for a schematic of a phono preamp for MC.
My humble demands are:
-I want to use one tube per channel.
-Oh, yeah and it mustn't contain an output transformer.
-It has to be for MC.
-It has to be RIAA, because it will be connected directly on an amp.

P.S.: It will be used on an Aleph5 or PPP using 2xEL84 per channel.

I really hope that someone has exactly what I'm looking for and will post schematic here.
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Old 28th March 2003, 11:10 PM   #2
SY is offline SY  United States
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If you're talking about low output MC, you're going to have one hell of a tough time getting the noise acceptably low with a 12AX7 and no transformer. And you'll have barely enough gain. And to get that gain, you'll have to have a very high output impedance.

That's an odd list of restrictions you posted. There are much better ways to skin that cat.
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Old 28th March 2003, 11:53 PM   #3
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Default Mision Impossible.

Hi,

Quote:
That's an odd list of restrictions you posted. There are much better ways to skin that cat.
Yup, unless perhaps that MC is at MM output level or close you can pretty much forget it.

For MC's you need I/V conversion, this can be done with tubes but it ain't easy.

Usually a step-up xformer is used or a (usually FET based) conversion is used to feed the MM level preamp.

How about it?
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Old 29th March 2003, 12:05 AM   #4
DJG is offline DJG
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It would be possible!
-But then I would need the transformer info also, if you have any!

So you say there isn't a way to amplify the signal from the MC with 1/2ECC83 and gain i with the other half of tube?
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Old 29th March 2003, 12:05 AM   #5
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Ditto SY and Frank. One tube/channel, and for MM you could use a modification of some of the classic NFB circuits like a 7C - Pooge or a PAS, but you'll still have insufficient SNR (I think even for decent MM) so you'll need an input transformer, and you'll have quite a high output impedance. The 12AX7 has a lot of gain, but isn't particularly quiet in itself. Having had a 7C, which was extensively modified over time, it's not that great sounding. I restored it and sold it.
You need to change your parameters to get a decent result, and in Eastern Europe, there are a ton of good tubes floating about like the 6C45 which would be a lot better.
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Old 29th March 2003, 12:09 AM   #6
EC8010 is offline EC8010  United Kingdom
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Default Your humble demands aren't humble!

RIAA equalisation and amplification is one of the hardest analogue problems to solve well. People spend years tackling this problem. How many records do you have? Any investment on electronics/arm/cartridge/turntable only makes sense in the context of the number of records. If you have lots, it makes sense to do the job properly. You cannot possibly do the job properly with a single ECC83 per channel. It may just be possible to squeeze the required gain but it will sound terrible.

On the positive side. What is the cartridge, and what level do you need at the output of the pre-amplifier?
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Old 29th March 2003, 12:22 AM   #7
DJG is offline DJG
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The cartidge is Dual ULM 45 S.
There is anothe option:
I could use 2xECC83 and 2xECC85. That is more prospective isn't it?

If I only have three ECC83 tubes I would go in for Paravinchini(I'm not sure if I wrote it right) preamp.
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Old 29th March 2003, 12:35 AM   #8
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Default Dual ULM 45 S

Hi,

Is that a MC cartridge?

Cheers,
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Old 29th March 2003, 12:38 AM   #9
EC8010 is offline EC8010  United Kingdom
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I'm not familiar with Dual ULM45s. Are you sure it's a moving coil? Sounds a lot like an Ortofon droop snoop to me. You really wouldn't want to let an ECC85 near audio. I've just had a quick look at the curves, and it will distort...

If your cartridge really is an MC, the 6C45 is an excellent valve for the front end.
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Old 29th March 2003, 12:40 AM   #10
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I think so. I'm quite sure it is. MC means christal and MM means magnet right? And MM cartidges are larger that MCs right? -Yeah, it's MC... Probably. I'm currently running it with NE5542.
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