V1-4 in a Jansen '6twenty'?

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MogwaiBoy
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V1-4 in a Jansen '6twenty'?

Post by MogwaiBoy »

Hello all :)

I have aquired a 1966 Jansen 6twenty head and wow, LOVE it.

Was wondering if any techies on the forum could advise me on the preamp valve config pretty please... It has 2 x new Sovtek 5881s powertubes - I'm not sure if that's as per original (stock) but I love 5881s so all cool.

However, the preamp valves have me slightly confused. There was a bit of hum at first and I tapped the front panel and heard almost reverb style wooshing - so I figured it must have been a microphonic tube. I replaced V1 and V2 and problem seems to be solved, but the V2 I pulled out was a 12AT7 which has confused me. I thought it should be 3 x 12AX7 + 12AU7 phase inverter.. or am I mistaken?

Old Motorola in V1 all good I guess. But I put a Tungsol reissue 12AX7 in V2 and now I'm worried about the "Tungsol in cathode follower stage = goodbye Tungsol" issue. I don't even know if V2 is a cathode following stage.

So my questions are...
- Should V2 be a 12AT7? (maybe for the tremolo or something?)
- Is there a 'cathode follower' stage in this amp, and if so, where? Would it be safe to use a Tungsol 12AX7 in this amp?

Cheers :)

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Re: V1-4 in a Jansen '6twenty'?

Post by AiRdAd »

I've got one. I'll check tonight and get back to you.
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Re: V1-4 in a Jansen '6twenty'?

Post by MogwaiBoy »

Rad, thanks Danny! If you could lemme know what the V1-4 tube types are please, that'd be a good start :) Thanks again.

I may have to bother Ryan or Mr Gilmore with the cathode follower question.

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Re: V1-4 in a Jansen '6twenty'?

Post by AmpShop »

There's always exceptions with these amps, as there were a few oddball variants, but generally:

V1: 12AX7 Ch1 preamp
V2: 12AX7 Ch2 preamp
V3: 12AX7 trem oscillator and cathode follower
V4: 12AX7 (or 12AU7) driver and phase splitter
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Re: V1-4 in a Jansen '6twenty'?

Post by MogwaiBoy »

Thank you so much for the info, Ryan! This one doesn't have the Gain Adjustment on the back panel if that's any further indication of which variety it is exactly. But great, cheers, should be all go to use the TungSol in V2 then - adds to the Voxy chime of the second channel for sure. Amazing sound out of this thing - it's very much everything I wished the Bassman50 was.

Thanks again :D

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Re: V1-4 in a Jansen '6twenty'?

Post by AmpShop »

Not a problem :)
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Re: V1-4 in a Jansen '6twenty'?

Post by AiRdAd »

i'm no help sorry - I checked the amp, and all the writing has worn off the tubes :-(
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