This involves routing the darker 'normal' channel through the reverb/trem circuit, and putting both channels in phase for easier jumpering/blending.
Since hearing about the 68 custom deluxe I'd been toying with getting this mod done for a while, and as my amp was going in for a service anyway and is well out of warranty (second hand, and dates back to before they put the digital circuit trem in there - more on that later), I figured it was worth a try. I could have just had the bright cap clipped, but I wanted to compare the two and have the option of blending, using an A/B switch etc.
I'm extremely happy with the result - at volume 3-4 with pedals it sounds amazing now, especially for higher gain - just the right balance of warmth and clarity. I'd definitely say that running through the vib/verb circuit has brightened the normal channel very slightly, which I'm pleased with as previously I thought the two channels were a bit "too much/not enough" on that score.
At very low volumes (i.e. late night home practice) I still use the vib channel with OD pedals or for very bright stratty cleans, so it's good to have kept that option.
I've not gotten round to blending/jumpering yet as I was having too much fun with the normal channel!
As it's an older reissue with the opto trem and the attendant loud ticking noise, I also had the mod done to reduce the tick (adding some kind of cap or resistor to one side of the "bug" - can't remember the exact details). I'm happy to say this was also a success! Ticking now barely perceptible.
I left the tonestack and negative feedback circuit alone rather than copy the 68, figured this is something I could get done another time if I really wanted. Given how good it sounds now I very much doubt I'll bother.
hoping this is of interest to any 65DRRI owners also considering the mods. Goes without saying that I took it to a trusted tech to get the work done!
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If I ever decide I can't handle the noise on my '68 I could always flog it, buy an out of warranty '65 and mod away!
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I've manage to tame it by putting lower gain valves in the Reverb and Trem stages of the amp - it's certainly much more usable now. Not ideal though.
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It still puzzles me why they didn't put a bright switch on the reissue in the first place - the originals had them for a few years and it makes the amp so much easier to use.
Rift Amplification
Brackley, Northamptonshire
www.riftamps.co.uk
That would be a construction error re the reverb tank. I've seen this a few times.
The tremolo ticking can almost always be cured by altering the lead dress around the tremolo oscillator valve; if the wires on the anodes of this valve are too close to the phase inverter then noise can be coupled into the power amp.
The phase inverted input impedance is very high, a few M ohm, so it doesn't take much capacitance to couple noise into the power amp.
I'm very pleased with it - if I were to sum up in a couple of words my impressions after a few weeks of use, I'd say 'clear' and 'balanced'.
I'd read some reviews that the CRex could be dark sounding, but actually found it to have better overall definition than the stock C12K, albeit without the upper-mid spike the Jensen seemed to have which I found a bit harsh at higher volumes. The CRex certainly doesn't make the amp sound less 'fendery' to my ears.
The CRex has also unexpectedly improved the amp's low volume response, whereas the Jensen tended to muffle things until it had some volume behind it.
The CRex definitely complements the wiring mods I described earlier in the thread, and as a further bonus it's shaved nearly 2lbs off the amp weight!