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Old 30th September 2004, 07:00 AM   #1
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Default nuvistor MC step up

Hello tubies,

can anyone help with information on nuvistor MC step up amplifier. As I know Conrad Johnson has made such things in the past. What about noise? Is the nuvistor a good part for that application?

Reinhard
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Old 30th September 2004, 11:37 AM   #2
SY is offline SY  United States
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Difficult to find, expensive, and really microphonic. Oh, yeah, and not super quiet.

A better choice is something like a 417A.
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Old 30th September 2004, 12:39 PM   #3
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Try four paralleled (8 sections) 12AX7WB's
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Old 30th September 2004, 01:22 PM   #4
jlsem is offline jlsem  United States
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A pair of cascaded 8056 nuvistors with battery B+ can provide a very quiet MC phono pre-amp. Has anyone ever tried battery coupling? I've always thought this tube is a good candidate.

John
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Old 30th September 2004, 01:23 PM   #5
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Default 8 paralled section of 12 AX 7

Hello,

think that is what Aesthetix is doing. Is that really low noise or should I go for 6C45 or 437?

Reinhard

What can I do with my 40/40 pcs. of 2C51/2C52?
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Old 30th September 2004, 01:26 PM   #6
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Default cascaded

Hello,

what do you mean with cascaded? SRPP, u-follower, cascode
or two stages?

Reinhard
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Old 30th September 2004, 01:31 PM   #7
jlsem is offline jlsem  United States
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Two stages; the 8056 has a mu of 11 but can be operated very linearly with 12-24 vdc on the plate.

John
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Old 30th September 2004, 01:36 PM   #8
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Quote:
Is that really low noise or should I go for 6C45 or 437?
Don't know about the noise but a 6S45 will absolutely kill paralleled 12AX7 soundwise. IN any case the noise will be very dependent upon PS noise.
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Old 30th September 2004, 01:45 PM   #9
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Hi,

Quote:
Don't know about the noise but a 6S45 will absolutely kill paralleled 12AX7 soundwise.
If the datasheet is anything to go by req is ~100R which is extremely low.

If the curves are linear at Vg0 you can ground the cathode and couple the tube straight to the cartridge, one less cap in the signal path.

Otherwise it's an amazingly good tube for low level signal applications. Certainly one to consider for anything phono.

// 12AX7s is about the last thing you'd do for an MC stage IMHO.

Another candidate is the 6DJ8 which is what I used prior to the availability of the USSR special tubes.

Cheers,
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Old 30th September 2004, 01:48 PM   #10
SY is offline SY  United States
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As a rule, voltage noise runs about 2.5/gm. It takes a lot of 12AX7 sections to equal a proper high transconductance triode.
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