Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by StrummersOfThunder »

Moist feelings ?

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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by StrummersOfThunder »

Its a really cool build Jay
Moar gain tho ?
Does it have tremolo?
I might be keen if your making some. Pretty groovy stuff. Well done

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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Slowy »

bender wrote: Tue Feb 23, 2021 8:59 pm

I have! I loved it. But it was skull crushingly loud. Also, less cloneable.
I've since learned how to tame it. I now use it for everything from lounge room jams to the biggest gigs I play.
"I would stop worrying about it and ride."
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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by StrummersOfThunder »

Slowy wrote: Wed Feb 24, 2021 8:11 am
bender wrote: Tue Feb 23, 2021 8:59 pm

I have! I loved it. But it was skull crushingly loud. Also, less cloneable.
I've since learned how to tame it. I now use it for everything from lounge room jams to the biggest gigs I play.
What is this swiss army amp you speak off ?

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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Slowy »

StrummersOfThunder wrote: Wed Feb 24, 2021 8:32 am
Slowy wrote: Wed Feb 24, 2021 8:11 am
bender wrote: Tue Feb 23, 2021 8:59 pm

I have! I loved it. But it was skull crushingly loud. Also, less cloneable.
I've since learned how to tame it. I now use it for everything from lounge room jams to the biggest gigs I play.
What is this swiss army amp you speak off ?
Designed and built by Bill Warriner in Tauranga. To the best of my understanding, a pre-amp based on the AC15. Power section selectable between two 6L6 which gives Fenderish character and two 6DZ7 which makes it very snappy and AC30ish.

It's put together like an Abrams battle tank and completely silent. When I contaced Bill, his first question was, " Has it given you any trouble?'"
When I said no, he replied, "That's good. I built it to last."

It loves pedals which is something I find very useful and by itself has a clarity that lets individual guitars show their voices. Since it arrived, I have never felt the need for another amp.
"I would stop worrying about it and ride."
Sizzilingbadger.

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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Jay »

StrummersOfThunder wrote: Wed Feb 24, 2021 7:07 am Its a really cool build Jay
Moar gain tho ?
Does it have tremolo?
I might be keen if your making some. Pretty groovy stuff. Well done
No tremolo sadly, would need another valve for that. The 6/Twenty does have a tremolo and is a fine beast too. No intention to clone that latter though.
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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Anvil Amps Alan »

6DZ7 ( 2x EL84 in the same bottle) a rare beast! I have some with projects in mind.
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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Optical »

How did you end up configuring that extra gain stage? I recall you had a few options on where to insert it.
Easy to add a solid state trem in there if you really wanted one..

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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Slowy »

Anvil Amps Alan wrote: Thu Feb 25, 2021 7:24 am 6DZ7 ( 2x EL84 in the same bottle) a rare beast! I have some with projects in mind.
Exactly. Plug in 2 bottles and get the sound of 4 EL84s.
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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Jay »

Optical wrote: Thu Feb 25, 2021 2:10 pm How did you end up configuring that extra gain stage? I recall you had a few options on where to insert it.
Easy to add a solid state trem in there if you really wanted one..
Sorry, missed your post.

I used the spare triode as an input gain stage and played around with values for the bias cap, the coupling cap to the next triode and the anode resistance.
Settled for 10uF/1K5 for bias, 0.1uF for coupling and 168K for anode resistor.

For the latter I had 220K initially but with the 12AX7 that was too much distortion. Going down to 168K and a 12AY7 tamed it.

Edit -forgot to mention that I also added a bias cap to the third triode (just before the PI) to get a little more gain.

What do you suggest for a solid state tremolo? Any schematics at hand?
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Re: Building a Jansen 4/TWELVE SPECIAL copy (COMPLETE)

Post by Optical »

There are two parts to any tremelo - the control voltage generator and a muting device. Easiest way to implement a muting device is an LDR with a low on-resistance - put that across a signal path somewhere in the signal chain and send a varying control voltage to it to vary the muting effect it has. I'd start by testing some LDRs in the circuit with a manually fed voltage to see where it has the best effect, then you could build the control voltage section to suit.

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