# Interview with McCormick Analog



## jbealsmusic (Feb 12, 2014)

I don't know much about amp electronics, so I could have easily stayed for several hours and listened to him talk gear. Fascinating stuff!

[video=youtube;5kBDVaMTUps]https://www.youtube.com/watch?v=5kBDVaMTUps[/video]

I really liked the Fender reverb mod he goes over at around 21:45. I can't tell you how many people I know who have gone nuts looking for this kind of solution in a million other places.


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## nonreverb (Sep 19, 2006)

Interesting however, I don't know if that mod would be a great idea. The reverb transformer is essentially an output transformer. You can actually connect an speaker to it and presto! It becomes a 1 watt amplifier. Placing 470K across it is sorta like putting 470K across your output transformer....nothing may come of it due to the low wattage but I tend to err on the side of caution.



jbealsmusic said:


> I don't know much about amp electronics, so I could have easily stayed for several hours and listened to him talk gear. Fascinating stuff!
> 
> [video=youtube;5kBDVaMTUps]https://www.youtube.com/watch?v=5kBDVaMTUps[/video]
> 
> I really liked the Fender reverb mod he goes over at around 21:45. I can't tell you how many people I know who have gone nuts looking for this kind of solution in a million other places.


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## jbealsmusic (Feb 12, 2014)

nonreverb said:


> Interesting however, I don't know if that mod would be a great idea. The reverb transformer is essentially an output transformer. You can actually connect an speaker to it and presto! It becomes a 1 watt amplifier. Placing 470K across it is sorta like putting 470K across your output transformer....nothing may come of it due to the low wattage but I tend to err on the side of caution.


Since we talked about it, I looked it up and have seen that same mod published in a couple of tube amp repair/mod books. But, I don't know much about this stuff. What do you think could happen?


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## jb welder (Sep 14, 2010)

Like nonreverb said, the reverb drive section is a little tube power amp. The 12AT7 is the power tube, and the reverb drive transformer is the output transformer. The input of the reverb tank has an impedance of around 8 ohms, just like a speaker.
If you run a tube amp with no speaker, high voltage spikes can destroy the output transformer. In the case of this boost mod, you are disconnecting the little transformer from it's load and may damage it.
The boost is a clever idea, just poorly executed here. Fender used it in the later silverfaces that had pull boost knobs, but they did not disconnect the tank.
His little jumper has a series 470K in series between the 2 ends. It also should have a resistor between hot and ground, something around 8 ohms/2watts. This will act as a load resistor and keep the drive transformer safe. Then if the boost is no longer enough when set full, you could decrease the value of the 470K.
Alternatively, you could run a splitter off the "send" end of his mod cable, and have the input of the tank remain connected.

One more thing, it sounds like a cool idea, but we didn't really get to hear it 
The pull boost sound was not popular at all when Fender did it. Most people don't like the sound of it. But that's a matter of personal taste.

http://www.prowessamplifiers.com/schematics/fender/deluxe_reverb_boost_schem.pdf


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## toby2 (Dec 2, 2006)

There was a device back in the 70's called an Ice Cube ( they used to advertise in GP mag ) . It did a similar reverb overdrive thing . It sounded bad . I think Jeff Bober had this mod published in the first G Weber book .


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## jbealsmusic (Feb 12, 2014)

jb welder said:


> One more thing, it sounds like a cool idea, but we didn't really get to hear it
> The pull boost sound was not popular at all when Fender did it. Most people don't like the sound of it. But that's a matter of personal taste.


Sorry about that, the camera mic adds a lot of compression. I don't know how Fender's pull-boost sounded, but the resistor mod sounded great. When it was set at 2-4, it sounded like a decent loud but clean boost. Didn't muck up the tone at all to my ears. Any more and it started to dirty up a little too much for me.

All very cool info. Thanks guys!


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