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FDP Forum / Amp Mods, Repairs, and Projects / Deluxe/Bandmaster VM mods

swampyankee
Contributing Member
*******

olde New England

If you can't play good, play loud
Sep 16th, 2015 01:34 PM   Edit   Profile   Print Topic   Search Topic

Apparently, the Deluxe/Bandmaster VM series amps were not a big hit since they were discontinued after just a few years. But I'm a champion of lost causes so I bought a BMVM for band use. It sounds pretty darn good as is and we're all happy with it, but I'm always curious about what can be improved.
I went looking for possible mods and found a German company, Tonehunter, that claims to have a "real vintage" mod that they advertise for 149 euros. One of the things they claim to do is to take the harsh highs out, which I'd be interested in, since the gain channel can get a bit peaky when pushed.

I'm not keen on sending my amp overseas for modifications, but I'd be curious to know what they do, and if anyone else has done mods to this amp to improve it or alter it in a good way?

Tonehunter

Steve Dallman
Contributing Member
********

Merrill, Wisconsin

Age is just a number...mine is big
Sep 17th, 2015 02:37 PM   Edit   Profile   Print Topic   Search Topic

Much of the circuitry in this amp is solid state Op amp. There is one tube in the preamp, surrounded by op amps.

The op amps are reasonable TL072. One could go with a more modern, hi fi type op amp. The tube is only in the drive channel and is a Sovtek 12AX7WA, which is a rather non descript, lower gain tube.

A different tube may help. There are a lot of little things that could be done...tone stack tweaks, roll off some treble in the op amp stages for the drive channel, different op amps. Something as simple as trying a darker tube may be all you might need. A JJ would be darker. Sovtek's can be bright and harsh.

Another 100pF cap soldered over C86 might help. One over R156 might help as well.

Without the amp it's hard to say. I usually play and listen to an amp and then decide what is too much, what might be wrong, what it's not doing that I wish it to do, etc. I haven't played or worked on this particular amp.

I changed a lot of op amps in SS amps. Changing 1458's or 4558's with bifets usually brings an amp to life. The bifets I used were the TL072's in your amp. These days there are better op amps, but how much improvement if any, who knows until you try.

It may even be that going to non-bifets in the op amps of the drive channel would tame the harsh highs.

What speakers do you use? V30's mute highs a bit and sound great with distortion, but stray from classic Fender for cleans.

Perhaps that 149 might be better spent on speakers and/or a tube. The Sovtek WA should be OK for the PI.

BUT try a 12AT7 for the PI. It will lower the impedance there and add headroom and more of a blackface feel.

A JJ 12AX7 and any 12AT7 would be worth trying.

Schematics

swampyankee
Contributing Member
*******

olde New England

If you can't play good, play loud
Sep 18th, 2015 11:39 AM   Edit   Profile   Print Topic   Search Topic

Interesting stuff Steve, thanx!

To be honest, I haven't explored the technical details of this amp yet. Just plugged and played so far. As far as I know, the tubes and circuitry are all stock. The cabinet is equipped with a pair of Celestion G12P-80's.

I'm not even sure I need to do anything to the amp since I'm still dialing it in and it sounds really nice in the band mix. I'll need a couple of real-world gigs to see how it performs at stage volumes, etc. But as you say, just a simple tube swap could be all it takes to make a difference. There's also a bias control and I read somewhere that running the amp a bit cooler would mellow it out too.

Steve Dallman
Contributing Member
********

Merrill, Wisconsin

Age is just a number...mine is big
Sep 18th, 2015 03:45 PM   Edit   Profile   Print Topic   Search Topic

To my ears, biasing cold increases crossover notch distortion and sounds awful...cold and harsh with no "balls."

Fender used to ship their tube amps biased cold...DRRI, HRD, Blues Deluxe, etc.

Even with the stock Sovtek 5881's, rugged tubes, but unremarkable in tone, the tone would improve greatly by biasing them warmer.

If the speakers are new(ish) they will break in over time, and mellow some as the low end opens up.

That speaker gets reviews of being great for chimey cleans, and harsh distortion. My experience with Celestions is limited, but I have a couple V30's and a few Greenbacks, as well as a 4 ohm 8" in my SF Champ. When I had my Mesa Dual Rectifier, the distortion sounded best with the V30's. In a Fender, I thought they were awful...sucked the Fender right out. I built an EL84 amp into Greenbacks, and voiced it to my ear. Into any other speakers, it doesn't sound as good.

swampyankee
Contributing Member
*******

olde New England

If you can't play good, play loud
Sep 19th, 2015 03:35 PM   Edit   Profile   Print Topic   Search Topic

I bought the cabinet from GCs used inventory so i dont know how broken in the speakers are. As far as I can tell, the VM series was discontinued in 2013 so I have to assume they've had some use. I definitely bought the amp for its classic blackface chime, so the Celestions are prbly as good a choice as any. Although Im breaking in a Warehouse G12c in my SCXD that is suppose to replicate a nice BF sound. If it works out i could try a pair of those down the line. Meanwhile, Some tube swapping sounds like a fairly cheap and easy mod.

(This message was last edited by swampyankee at 05:37 PM, Sep 19th, 2015)

FDP Forum / Amp Mods, Repairs, and Projects / Deluxe/Bandmaster VM mods




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