Wow 😮 The magnitude of understanding & analysis is astonishing.

I like the Rivera era Princeton! I find this very interesting.

Having one of these mid-eighties concerts, I'm very interested to follow this series to it's end, thanks for posting this. As one of many who gave up on the distortion channel, my curiosity is piqued!

Definitely following this series!! I have a red knob solid state fender Princeton Chorus I believe is heavily Rivera influenced in the overdrive circuit. So even though it’s solid state, I believe I will be able to piggyback on your observations and make parallel conclusions on the architecture. There is a beast lurking in this amp, but it needs to be coaxed out with proper fixes the circuit. Sadly, it’s a circuit board construction, so I might be limited in the changes I can make.

I think with any of these oddball amps, it's good to remember that they're a product of their time, & would have been trying to cop whatever was current. Not to say it's good or bad or terrible, but it does help me wrap my head around "what were they thinking?"

I just got one and looking to get mine done exactly redone like this with a Dumble add. You still do these rebuilds or mods?

From my limited experience the Dumble clean channel using a volume and master volume is sloppy. The gain of the whole amp is set via the first volume control which generally has to be set pretty high to work, the master volume is purely there to lower the volume of that channel. If setting the overall level was independent of the clean volume control then smaller bright caps could be used and there would be no need for a master volume.

I wish I could get someone to do this for my PRii.

I have the TR II - wish I could bring it to you!

At about 2:20, are those small black four-lead things dual capacitors or opto-isolators? For the tremolo, or?? Also, only 4 mfd of filtering to the preamp stage is something you might see in some Valco or Magnatone amps.

Could you put the dumble MV after the switching so it's active in both modes allowing a harder driven clean tone?

@PsionicAudio

3 жыл бұрын

I could, but the MV is much more crucial to balance the dirty to the cleans.

@nickbenjamin6527

3 жыл бұрын

@@PsionicAudio sorry, I meant the Dumble channel clean mode so the MV works on that as well as the full dirt but not the Fender clean channel. Then you can switch between clean Fender and pushed clean Dumble or full dirty Dumble rather than having two similarly clean but slightly different voiced channels if you're using the clean Dumble.

@PsionicAudio

3 жыл бұрын

@@nickbenjamin6527 ah. Not a bad idea. As long as the owner remembers to turn the MV down before pulling out the Drive knob... Otherwise pants might need changing. Thanks.

@PsionicAudio

3 жыл бұрын

Not sure if adding the necessary switching is feasible with the existing board/layout. But I'll take a look.

@nickbenjamin6527

3 жыл бұрын

@@PsionicAudio I thought it could just go in between the two switches? Sorry, I explained my idea rather unclearly! Would only be any point doing this if you could get any appreciable level of crunch out of the second stage in the Dumble channel with the volume before it turned up I guess...thanks for some very interesting videos!!

Just out of curiosity, I’m wondering why you are keeping the details of the mods to this amp secret. I realise that releasing your mods denies you of further work modifying other amps, but surely there are so few of these amps about now that it wouldn’t mean much of a loss of income? By comparison you released mods to modern Vox AC-30’s which would have cost you income as they were relatively new.

@PsionicAudio

3 жыл бұрын

I released the most basic of mods to the AC30CC. Not the full range of things I actually do on them. On this circuit, it's not because people will be rushing out to get Concert IIs to mod, but because I don't want to publish a schematic and have people try to build it and then flood my inbox with "Hey, I have a buzz - what causes that?" etc. I get a lot of that and there are only so many hours in the day. I will point out things of interest in the final circuit.

Fender has always struggled making a decent distortion Channel. They should give up and just stay in their Lane.