nuvistor MC step up

[reinhard]

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

 

[SY]

Difficult to find, expensive, and really microphonic. Oh, yeah, and not super quiet.

A better choice is something like a 417A.

 

[Geek]

Try four paralleled (8 sections) 12AX7WB's

 

[jlsem]

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

 

[reinhard]

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?

 

[reinhard]

cascaded

Hello,

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

Reinhard

 

[jlsem]

Two stages; the 8056 has a mu of 11 but can be operated very linearly with 12-24 vdc on the plate.

John

 

[analog_sa]

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.

 

[fdegrove]

Hi,

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,

 

[SY]

As a rule, voltage noise runs about 2.5/g_m. It takes a lot of 12AX7 sections to equal a proper high transconductance triode.

 

[EC8010]

I'm told someone used 6HS5! Mu = 300, gm = 65mA/V. You need >400V on the anode before it wakes up. Oh, and it's a power valve with a duodecar base and 1.5A heater (6.3V, though).

6C45 is probably the best bet...

 

[Geek]

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

Yeah! That's the one I meant

(read it in a TubeCAD article)

 

[SY]

I'm told someone used 6HS5! Mu = 300, gm = 65mA/V. You need >400V on the anode before it wakes up. Oh, and it's a power valve with a duodecar base and 1.5A heater (6.3V, though).

I've got a vision of a 6528A-based head amp. Cascode, of course, just because of the low mu.

It is not a pretty vision.

 

[fdegrove]

Hi,

I've got a vision of a 6528A-based head amp.

Yeah SY....
Go head and promote the 6528A.....

Then complain when it's become absolutely unobtainable....or worse: only Chinese ones....Yikes.

It's not as if you'd need them, right??


Cheers,

 

[reinhard]

mc step up

Hello,

everytzhing is interesting to me,

can anyone post schematics of analog stage and if possible powersupply.

Reinhard

 

[rfbrw]

Re: mc step up

Hello,

everytzhing is interesting to me,

can anyone post schematics of analog stage and if possible powersupply.

Reinhard

If you haven't already got it, the Counterpoint SA2 MC head-amp and psu schematic is on the Altavista Audio website.

 

[GRollins]

I owned a Conrad Johnson HV1-A at one point and can say that it sounded just marvelous. However, I can also confirm that it was microphonic as hell. Off the top of my head, I can't recall which tube they were using. The circuit was a simple grounded cathode as I recall. I drew it out before letting the unit go, but have no idea where the schematic got to--this was years ago, and I've moved a couple of times in addition to the usual number of other things that disarrange notes. If I get time, I'll try and scratch it up, but it'll be a day or two...or three.
Just beware of the microphony. They had the circuit board mounted on an "elastomer" suspension, meaning that they looped rubber bands through holes in the corners of the board and laced them around standoffs mounted an inch or two away. Still rang like a bell (lovely tinkling noise) if you rapped the chassis with your knuckle. Don't say you weren't warned.

Grey

 

[reinhard]

Thanx

Thank you rfbwr for the tip with Altavistaaudio, will have a close look.

Thank you Grey for searching, hope you can find it.

Have a happy weekend,

Reinhard

soldering irons warm?

 

[planet10]

An externally hosted image should be here but it was not working when we last tested it.

this is a well regarded phono that works with MC... you can use a triode on the bottom of the cascode, but it isn't as quiet. (just ignore the line stage bit)

(from Vacuum State web site)

If you just want to step up the signal for an existing you could probably adapt the 1st stage, but it might make sense to do the whole thing.

dave

 

[fdegrove]

Strictly Tubes...almost.

Hi,

you can use a triode on the bottom of the cascode, but it isn't as quiet.

Maybe not but I can't help but wonder what this circuit would sound like with a really high gm tube such as the 6C45-P replacing the frontend....

With a Req 100R it has all the potential to come close to the 2SK170BL as far as noise goes, besides tube noise is far less obtrusive to my ears_if at all audible_ than semi-conductor noise.

Then of course there's always MC HAMMER if you're looking for an add-on headamp.
It's dead quiet, can take just about any MC, uses ordinary parts, looks deceptively simple and does not have the word "microphony" in its vocabulary....
All it needs to shine are two pairs of tightly selected 6922s, two matched low noise CCSs and you're done.

Cheers,