Thursday, July 2, 2015

Carr Rambler, weak tremolo!

Here is one of my favorite modern day amplifiers. A Carr Rambler.



They are inspired by the well sought after Fender Princeton Reverb but this company has some pretty different things going on. I admit I've never been a huge fan of the black and silver panel Fender amps, too icy for my taste. I prefer tweeds and old Marshall amps. But I always dig the sound of these amps, largely because they are cathode bias rather than fixed. What this means as an owner of one of these is you don't need to bias the amp, feel free to drop in whatever 6L6 tubes you want. No trip to the shop necessary. What it also means is the tone is ultimately much warmer. These have that lovely magic midrange I need from an amp.

They also use Solen polypropylene capacitors for the power supply:





 They are huge and you will never need to replace them. They have the added advantage of giving the amp a smoother tone overall. Electrolytic caps are the 2nd from the worst, tantalums are at the bottom. The fact that Carr went this far to make a boutique amp truly boutique is impressive. I myself like a mixture of high quality components and trashy components. These don't use anything special in the signal path, just good old Mallory 150 series caps. I like those myself.

Here is a shot of the chassis:



Truly hand wired. A lot of love goes into making these amps. They are shockingly quiet amps. I could barely tell it was on until I played some music through it.

This came in cause my customer thought the tremolo a bit weak. Yeah, I agree. When I get a Princeton with a weak tremolo I usually check the resistors and caps. If they are all good then I replace the 1 meg resistor feeding the intensity knob with a 470k or lower. Tricky part is to get it strong without too much "wump wump woof woof" sound coming through. This amp has a very similar circuit except that it has no resistor. It is indeed a bit weak. So I replaced the 100k load resistor with a 220k, that helped. Next I put a .22 cap in parallel with the .1 cap that is feeding the intensity knob. To tame the  "woof woof" stuff I put in a .022 cap from pin 6 (connected to 220k load resistor and feed cap) to ground.

Also replaced one crackly 12AX7 and replaced a weak reverb driver tube with a nice NOS 12AT7. I never use new 12AT7 tubes as a reverb driver. They can die fast and there are plenty of very high quality NOS ones around.

Thanks for reading today! Feel free to ask for more specifics if you have the same issues.

JB


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