Jansen 4/TWELVE SPECIAL
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- sizzlingbadger
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Re: Jansen 4/TWELVE SPECIAL
I can't see that single stage input overdriving the PI much (especially as it has to drive the tone stack first) so the master volume probably isn't going to be much use in this amp. I would say most of the drive tones will come from the interaction of the PI with the output tubes, the master volume will screw with that too.
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Re: Jansen 4/TWELVE SPECIAL
As I have said, without pedals, this amp only produces output stage distortion. And a glorious thing it is.sizzlingbadger wrote:I can't see that single stage input overdriving the PI much (especially as it has to drive the tone stack first) so the master volume probably isn't going to be much use in this amp. I would say most of the drive tones will come from the interaction of the PI with the output tubes, the master volume will screw with that too.
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Re: Jansen 4/TWELVE SPECIAL
How do you know it's output stage distortion? And do you mean the power tubes, or just everything after the MV?
I'm just curious.. the MV sits after the first gain stage and tone stack, there is one more gain stage and the cathodyne PI (which is also sort of a gain stage) after that which will both start to clip at higher MV settings.
The PPIMV might be interesting as it will allow the second gain stage and PI to clip before the power tubes. But you could go full retard and install an L-pad into it which would be cool - basically a built in attenuation. Potential problem with those things is they are configured to match a particular speaker impedance.
I'm just curious.. the MV sits after the first gain stage and tone stack, there is one more gain stage and the cathodyne PI (which is also sort of a gain stage) after that which will both start to clip at higher MV settings.
The PPIMV might be interesting as it will allow the second gain stage and PI to clip before the power tubes. But you could go full retard and install an L-pad into it which would be cool - basically a built in attenuation. Potential problem with those things is they are configured to match a particular speaker impedance.
- AiRdAd
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Re: Jansen 4/TWELVE SPECIAL
I'm getting the feeling that by the time this amp is finished, it's going to have 'strymon' levels of complexity and sophistication!!!
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- RectifiedAmps
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Re: Jansen 4/TWELVE SPECIAL
Why not just build the amp as per the original, see how it sounds, then make any adjustments to personal taste? Provided you allow for space considerations for pots for PPIMVs, L-pads, VVRs, etc, etc, you can always add things in later and you may just decide you don't need them. Slowy's amp has survived ca.50 years without being excessively modded or butchered, so the circuit must be doing something right as it is!
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Re: Jansen 4/TWELVE SPECIAL
And sound nothing like the originalAiRdAd wrote:I'm getting the feeling that by the time this amp is finished, it's going to have 'strymon' levels of complexity and sophistication!!!
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- Conway
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Re: Jansen 4/TWELVE SPECIAL
Pure luck.RectifiedAmps wrote:Slowy has survived ca.60 years without being excessively modded or butchered, so he must be doing something right as is!
- Jay
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Re: Jansen 4/TWELVE SPECIAL
Just noting that the original amp does not have a Master Volume, only a Volume pot...Optical wrote:How do you know it's output stage distortion? And do you mean the power tubes, or just everything after the MV?
I'm just curious.. the MV sits after the first gain stage and tone stack, there is one more gain stage and the cathodyne PI (which is also sort of a gain stage) after that which will both start to clip at higher MV settings.
The PPIMV might be interesting as it will allow the second gain stage and PI to clip before the power tubes. But you could go full retard and install an L-pad into it which would be cool - basically a built in attenuation. Potential problem with those things is they are configured to match a particular speaker impedance.
Not sure if PPIMV stands for Post or Pre phase Master Volume in your reference?
I could just leave the gang pot in and remove the two 1.8 MOhm resistors. When the gang pot is at full 250KOhm it basically represents the original circuit. If the MV sounds shit between less than full and zero, then just remove the pot and put the two resistors back in.
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Re: Jansen 4/TWELVE SPECIAL
You are far too sensible! And yes, that is probably the best way since this is my first valve amp build.RectifiedAmps wrote:Why not just build the amp as per the original, see how it sounds, then make any adjustments to personal taste? Provided you allow for space considerations for pots for PPIMVs, L-pads, VVRs, etc, etc, you can always add things in later and you may just decide you don't need them. Slowy's amp has survived ca.50 years without being excessively modded or butchered, so the circuit must be doing something right as it is!
When faced with quality, I recognise it every time.
- Slowy
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Re: Jansen 4/TWELVE SPECIAL
Absolutely. I'm a lucky guy.Conway wrote:Pure luck.RectifiedAmps wrote:Slowy has survived ca.60 years without being excessively modded or butchered, so he must be doing something right as is!
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.
- Jay
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Re: Jansen 4/TWELVE SPECIAL
It sounded great at the Auckland gearfest, but probably a fair bit of nostalgia involved tooJehu wrote:Wow, what a cool project... I can't wait to see how this turns out. I haven't heard one of these amps, but it sounds like they're pretty awesome.
Here is the build thread, and you probably have already seen that and thought WTF
viewtopic.php?f=41&t=35767
When faced with quality, I recognise it every time.