Amp tinkerers and people who aren't afraid of 700 volts or so in here....

Moderators: Slowy, Capt. Black

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BY sizzlingbadger
#809660
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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BY Slowy
#809664
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.

As I have said, without pedals, this amp only produces output stage distortion. And a glorious thing it is.
User avatar
BY Optical
#809721
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.
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BY AiRdAd
#809724
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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BY RectifiedAmps
#809731
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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BY jeremyb
#809738
AiRdAd 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!!! :-)


And sound nothing like the original :lol:
User avatar
BY Conway
#809745
RectifiedAmps wrote:Slowy has survived ca.60 years without being excessively modded or butchered, so he must be doing something right as is!

Pure luck. :wink:
User avatar
BY jvpp
#809813
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.


Just noting that the original amp does not have a Master Volume, only a Volume pot...

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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BY jvpp
#809815
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!


You are far too sensible! And yes, that is probably the best way since this is my first valve amp build.
User avatar
BY Slowy
#809855
Conway wrote:
RectifiedAmps wrote:Slowy has survived ca.60 years without being excessively modded or butchered, so he must be doing something right as is!

Pure luck. :wink:

Absolutely. I'm a lucky guy. :D
BY Jehu
#813630
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.
User avatar
BY jvpp
#813636
Jehu 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.


It sounded great at the Auckland gearfest, but probably a fair bit of nostalgia involved too :wink:

Here is the build thread, and you probably have already seen that and thought WTF :lol:
http://nzguitars.com/forum/viewtopic.php?f=41&t=35767
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