NAD: DVM Champlifier 5F1

[kidsmoke*]

Happy Birthday to me.

I won't go into detail, since most of you spent at least a few moments reading about, and coveting, this very same amp.

I've really been on a tone quest, and determined that I'm fine on guitars, I need to learn more about the tonal palette that amps provide. Like many of you I assume, I've spent an embarrassing amount of time reading and watching youtube demos on various things, bought a little here and there, and keep wanting.

So when Vood posted this little tweed beauty, representing a classic, benchmark tone, and of course, his workmanship, all in a small, and eminently maintainable package, I couldn't pass it up.

I'm not the least bit disappointed. With both humbuckers and singles, I'm finding a lot to love. Using the volume knobs on my guitars more than I ever have, and I'm THRILLED to say that my fear that this would simply not work well with buckers was baseless. It does break up early with them, and dimed (er....dozened) it does get a bit flubby on the bottom end with them, but hanging in around midway on the volume is fantastic, OR what I find I'm doing is having the amp volume at 4-5, and diming the guitar starts to drive it, or using the Klone (DVM's 1st generation centaur clone) gives it a great driven sound.

There isn't alot beyond that. No tone controls, or anything of the sort. It sounds and feels very honest. I feel as though I'm hearing the guitar, plane and simple, and as a student, I think this is a great place to hang out for a while, and not hide behind control knobs. It's up to me and my fingers, with maybe a dirt pedal here and there, to get the sounds I want.

Love it.

One possibility to addressing the "flub" at higher volumes, I've learned, is to substitute a solid state rectifier in place of the 5Y3GT tube. This supposedly "tightens" the bass, and was one fundamental change that Marshall implemented when adapting Fender circuits. Thoughts or comments on that?

the above referenced thread has lots of photos, so I'll simply reshare one for now, to refresh your memory.

And as always, DVM, as a vendor, has been peerless. Cheers, buddy.

Sellers photos....

[kidsmoke*]

Addendum...for those who can speak to the tube selection issues. I went NOS on these after arrival. Currently sporting a Westinghouse 12ax7 in the pre, RCA 6v6 (shorter than a modern JJ ?!) and a RCA 5Y3GT. All three, old relics from a local amp guy here in Chicago.

At low volumes, with the guitar volume rolled back, she's clean and quiet as can be. I'm impressed.

[duhvoodooman***]

One possibility to addressing the "flub" at higher volumes, I've learned, is to substitute a solid state rectifier in place of the 5Y3GT tube. This supposedly "tightens" the bass, and was one fundamental change that Marshall implemented when adapting Fender circuits. Thoughts or comments on that?

I would strongly advise against replacing the rectifier tube, for the following reasons:

1. First, it's an integral part of the sound and feel of the Tweed Champ circuit. I would expect that going to SS rectification might substantially change that. Now, that's not necessarily a bad thing, depending upon what you're looking to accomplish, but the amp wouldn't really be a Champ anymore.
2. Second, that's not a small change. There's a fair amount of work involved to make that conversion, though any reasonably competent amp tech would have no problem doing so. I would also be concerned about it significantly increasing the DC voltages within the circuit, so some changes in the stepping resistors would probably be needed.
3. Third, there are other ways to reduce bass in the circuit that are simpler and probably more effective than going to SS rectification. But....

....I think the bottom line is that you're not going to turn a Champ into a Marshall JMP. It's just not designed to be that. When Marshall started modifying Fender circuits, it was the Tweed Bassman that they went after, so you're talking about a much bigger, push-pull Class AB amp with several other important changes in the circuit, not to mention four 10" speakers. I would urge you to accept the Champ circuit for what it is--a simple and very toneful amp that excels with single-coil guitars, which is what it was designed to amplify (Fender didn't come out with a humbucker guitar until the early '70s). The changes that you would make to tighten the bass for humbuckers would almost certainly be to the detriment of the amp's performance with single coils.

I should also mention that I had already done one modification on the amp to tame the bass a bit, namely dropping the size of the cathode bypass cap on the first preamp stage quite substantially. Details are available here, if you want to read about this simple mod: http://buildyourownclone.com/board/v...297142#p297142

[kidsmoke*]

I understood the SS mod was simply a drop in alternate to the the 5Y3, a la....

http://tubedepot.com/ssr.html

But, having said all that...I'm not looking for a Marshall at all. This little tone monster is perfect, and as stated in the OP, learning how to use volume knobs and finger tips with a simple circuit is exactly what I wish for. IF it was a simple as a tube swap to tighten the bass, with no other changes, then that would be something to consider. My instructor is a vintage amp junkie, who states that his personal preference is for SS rectification for this reason. Caused me to explore a bit.

Appreciate the link. Your descriptions are actually pretty understandable, even for this midge.

[duhvoodooman***]

I understood the SS mod was simply a drop in alternate to the the 5Y3, a la....

http://tubedepot.com/ssr.html

A-ha! I totally forgot about those plug-in SS rectifiers. My bad. Yeah, for $10 it seems worth a try. I was thinking you were referring to removing/bypassing the rectifier tube and installing a 4-diode rectification array between the PT and the B+ rail. It does, however, still have the B+ voltage issue I mentioned; as noted in the description, "Please be advised that this replacement will increase overall B+ (plate voltage) by 10-20%." That shouldn't be an issue, since the Sovtek rectifiers run about 10% high on the B+ and nobody has reported any problems from that in the Champlifier.

That said, I'm not sure you'll get much benefit from it in the single-ended Champ circuit--because the output tube is always "on", rectifier tube sag isn't an issue. But for $10, why not give it a try?

[kidsmoke*]

Ran this through my 212 Peavey cab last night. HOLY CRAP! What fantastic sound. No need for any tube/SS rectifier swap consideration, or anything else for that matter. Would seldom have need for the expansive sound that was produced, but it was beautiful, and remained tight all the way to 12.

Problem with all that is now all I can think about is how amazing the Tweed Royal would sound.

[duhvoodooman***]

.....now all I can think about is how amazing the Tweed Royal would sound.

Beyond amazing. A Strat into the Tweed Royal in push/pull (Deluxe) mode with the Bright & Normal channels jumpered together, the tone knob around 2 oclock and volume "to taste" is TO DIE FOR!!