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Old 31st December 2010, 01:08 AM   #1
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Default can a cathode follower drive a tone stack and an effects loop?

Hey there,
is it possible to have a cathode follower driving a tone stack, driving an effects loop aswell? connect a mono jack for the loop send from the cathode, then make a MOSFET/JFET recovery stage then go to the tone stack? or go from the treble pot to the effects send and then a recovery stage? basically i dont have room in the chasis for another valve so i need to keep it as small as possible.
Thanks for any help in advance
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Old 31st December 2010, 04:17 AM   #2
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What amp? I would drive it from the cathode follower and return it into the tone stack using the LND150N3-G. You pop it in just the same as you would with a 12AX7, same cathode and plate values. 500v device, not bad sounding from accounts but not something you want to blast away with a lot of signal level. Mildly distorted it is said to sound OK. Better at supplying gain.


FET Preamp with LND150 Operates on Tube B+, part 1

AX84.com - The Cooperative Tube Guitar Amp Project
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Old 31st December 2010, 11:47 AM   #3
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no amp in particular, its just an amp ive been building with 3 gain stages and a cathode follower, i then wanted to add an effects loop aswell but theres not much room for another tube to be added, but thank you very much!
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Old 31st December 2010, 02:36 PM   #4
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In that case how about reconfiguring the cathode follower stage as an return and use a IRF820 as the cathode follower. They are more easy to get.

IRF820 cathode follower - Google Search
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Old 2nd January 2011, 02:40 PM   #5
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hmm i might try this, though ive found a schematic very similar to what ive built, its a laney LC15 except im not using it as a push pull amp and the HT on the preamp is 250v for the whole pre amp. cathode cap values are 1uF but the attenuation between stages is about the same.

http://www.freeinfosociety.com/elect.../laneylc15.pdf

i was wondering if i should copy the op amp effects loop, but im not sure what kind of swing ive got,
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Old 2nd January 2011, 02:41 PM   #6
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are there any higher voltage op amps that would work?
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Old 2nd January 2011, 06:02 PM   #7
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Quote:
Originally Posted by razorrick1293 View Post
Hey there,
is it possible to have a cathode follower driving a tone stack, driving an effects loop aswell? connect a mono jack for the loop send from the cathode, then make a MOSFET/JFET recovery stage then go to the tone stack?
Yes. Better than introducing a bunch of SS devices anyways.
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Old 2nd January 2011, 09:46 PM   #8
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Quote:
Originally Posted by SemperFi View Post
Yes. Better than introducing a bunch of SS devices anyways.
so going by that schematic, i can just put a jack straight from the top of that 100k resistor, then another one after it with a recovery stage?
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Old 3rd January 2011, 12:38 PM   #9
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Yes, AC coupled and attenuated with a resistor voltage divider. Gain at that node, when all is maxed, is 14000! Perhaps a loop out can be out of V1b's cathode since the signal level here is probably more usable. Even here tho you want a resistor in series, like 47kohm, to protect from a short.
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Old 3rd January 2011, 02:15 PM   #10
Structo is offline Structo  United States
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I have built a couple Dumble clone amplifiers and one of his designs is a tube buffered effects loop that mates very well to his amps, many feel it is required equipment for the Overdrive Special style amp.
It uses a plated loaded input amp then a cathode follower output.
Really works well.

Originally it uses a small 135v power transformer that mounted on the outside of a single 1U rack enclosure.

I had trouble locating that transformer so I used a PT for a Fender Reverb unit.

The original uses a voltage doubler to get the required voltage where the FX loop I built with the Reverb PT uses a bridge rectifier.

This unit is inserted between the last stage and phase inverter.

Click the image to open in full size.

Click the image to open in full size.

I tried a solid state FX loop before this one and it clipped the signal when the amp was up loud.

The neat thing about this loop is you can use the ouput pot as an overall master volume and you can create a pretty nice tone at bedroom levels, or crank it up to gig volume.
__________________
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Keep that smoke in the amp!

Last edited by Structo; 3rd January 2011 at 02:20 PM.
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