Marsha HBE/HB with SAT/FAT/C45 50 watt

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eljodon

eljodon

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Hi Dave, I purchased my 50 watt Marsha HBE/BE from a store on Ebay and the serial is #00024. Is it possible to upgrade the amp to 100 watts? I also changed the tubes to SED EL 34 and I own a bias meter and I do all the bias adjustments to all my amps and when I checked tha bias it was reading 62 ma! So I lowered it to 42/39 because thet's the lowest it will go. So it appears that the amp might need to be modified to get the bias reading to 32ma. Thanks
 
eljodon":ydkxbf3b said:
Hi Dave, I purchased my 50 watt Marsha HBE/BE from a store on Ebay and the serial is #00024. Is it possible to upgrade the amp to 100 watts? I also changed the tubes to SED EL 34 and I own a bias meter and I do all the bias adjustments to all my amps and when I checked tha bias it was reading 62 ma! So I lowered it to 42/39 because thet's the lowest it will go. So it appears that the amp might need to be modified to get the bias reading to 32ma. Thanks
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Did it bias correctly with the old tubes?
 
I didn't try it with the old tubes(Groove Tubes EL34LS), thanks for your quick reply
 
Reason I asked is you might just have a really hot set of tubes. If not, the bias resistor can easily be swapped out. It's a 10 cent part.

As far as the 50/100 upgrade, I doubt it would be worth the cost. It's major surgery.
 
Could be the bias circuit was charged to bias the other tubes. Email me a picture of the inside near the bias circuit. Also it could be updated to 100 watt cost would be 300.00 to do it. Email racksystems@yahoo.com
 
OK, thanks Dave, I'll send you a picture. Is a good thing that you used a 100 watt Plexi chassis when you built the amp because it already has the holes for the 2 outer tubes! I love the sound of the 50 watter, but I need more headroom because the amp sounds a bit spongy when I crank passed 5. It might also make up for the spl lost when the SAT switch is engaged. What I love about this amp besides it's killer sound, is very quiet compared to other high gain amps! When I use my Furman PQ 3 parametric eq in the front end of the Marsha and the results are devastating! I'm tempted to have Dave mod my Metro 50 watt with just the BE mod and a switch to disengage switch for a stock sound, but it needs improvement. I has Mercury Magnetics transformers whicg I'm not crazy about! I have an old Sound City Concord amp with a Pardtrige transformer. I wonder if is possible to use it on my Metro Plexi.
 
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