Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on September 24, 2017, 11:31:12 am
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I am going to be building a couple of 50 watt Marshall style amps with some MM transformer sets, chassis and head cabinets I have in stock to sell to local players. I'd like these amps to have classic Marshall EL34 tone with some type of footswitch controllable lead boost. I know Doug has a Plexi with a hotswitch option but I'm sort of leaning towards a 2204 model with MV or something with a few bells and whistles and maybe even a tube effects loop. Also maybe a half power switch if I don't sell them with an attenuator like the layout attached. Any suggestions for a killer player's amp?
All feedback appreciated,
Barry
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What about power scaling instead of an outboard solution? It might make for a more versatile amp overall?
Jim
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I'm open to that if the tone is not to dramatically affected. As a matter of fact, I think I have a London Power SV-1 kit in the shop somewhere
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if you want mid-to-high gain marshall tone, I can't say enough good things about the SEL design from AX84
http://www.ax84.com/static/sel/AX84_SEL_101004.pdf (http://www.ax84.com/static/sel/AX84_SEL_101004.pdf)
if you really need 50W, you can bolt the pre-amp to standard PP PA. I run an el34 in mine for around 11W and played clubs with 100 folks, no mic, and only run MV at 75% or so. The SE version will also give you power tube distortion and nice compression without blowing your head off.
as for lead boost, my vote would be to add foot-switchable second MV. simple, flexible. anything less than a second MV will provide limited control as to how much boost you want. you might also consider bypassing the tone stack by lifting the ground at the same time as when you boost for extra tonal thickness for leads.
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Denny,
I may have to build one of those for my studio. I've got a bunch of KT88s in stock
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I built the SEL several years ago and, IMO, it is one heck of an amp. Mine was set up with external bias and we tried EL84s, 6V6s, 6L6s, EL34 and the KT 88. I favored the 6V6 but the guy that plays it really likes the 6L6. With the two gain controls and the master volume control it is very versatile . Note:The KT88 is really loud when matched with a high efficient speaker.
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.. some type of footswitch controllable lead boost.
maybe even a tube effects loop.
I own the MESA amp that this snip is from and this arrangement of stacked pots after the FX loop works very well for a controllable lead boost that is simple to implement and will not effect the tone.
Just make the path "to sw circuit" a relay switchable path to ground and you're done.
So, right there you've got the FX loop and SOLO in one - proven winner.
I have also built this where the whole loop is switchable, independent of the Master/Solo
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Thanks Silvergun. That's very interesting. From which Mesa amp is that snippet taken?
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I'm also curious about which amp that's from. Interesting that the boost sits between two pre-amp stages so would think that the boosted signal would overdrive that next stage and change the color of the tone along with the boost? I tried that same approach with the MV after the last stage but in my case it's in parallel with the tone stack and also provides grid leak for the single-ended power tube, so adding more resistance to the lower leg would only boost another 10% or so once the MV ran past noon.
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MESA Single Rectifier RECTOVERB Solo 50
http://el34world.com/charts/Schematics/files/mesa_boogie/boogie_solo50_rectoverb.pdf (http://el34world.com/charts/Schematics/files/mesa_boogie/boogie_solo50_rectoverb.pdf)
dennyg, it sits right after the FX loop and right before the PI
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RECTOVERB Solo 50
for those wanting to learn schematics, study this, or the Nomad, warning, your brain will hurt
back to regular programing.....
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I use a relay actuated RAW circuit with a 22k pot and bright cap as a boost for my London Power Fender mod. The boost is variable and adds bite without too much fizz. The 2204 is already rich with mids--not sure how this would sound but it is very easy to implement. ..Jim
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Thanks jim