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Vintage threads from the first ten years

Re: Dumble

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6/29/1999 3:14 PM

Got mine runnin' yesterday. The amp distorts (overdrive not engaged) on about 3. Overdrive sounds really nice and creamy. Built mine into a homeless "68 Super Reverb chassis (basket case/ not restorable). Used the normal channel with the reverb return/mix tube as the OD. The other channel is a plexi/Bassman type. Mix the two through 220k resistors ala BF Fender. No deep switch. Found the brite switch too much, changed cap to a 180pf. May try a different treble cap, also. Did anyone try the "accent" setup? Haven't got to it yet. Thought I might share my experiences, and would welcome any comments....Dave

6/29/1999 5:05 PM
Jim S.	What's the "'accent' setup"? I don't see an "Accent" switch anywhere on the schematic.

6/29/1999 5:37 PM
jason	Jim, Do you have the 8 page zip file of dumble schematics from Steve Aholas site? It's on one of those. It's basically a cap of the NFB loop, looks kinda like a preset presence. jason

7/2/1999 7:35 PM
Dave	Has anyone played with the bright & treble cap values? Having a time with the top end balance.... Also, anyone tried the accent cap? Could someone give me ideas on how to make it a variable presence control? Thanks for sharing.....D

7/2/1999 10:20 PM
BWilliamson	On my clone I never did put in the bright switch--didn't find the need. I also went with a 250pF treble cap after backing it down a couple of notches, mine was very brite. I also added a presence control. If I remember correctly I just added a 10K pot with a .1uF to ground instead of the switch. Works good enough for me for know. Just look at an older Fender schem. bw

7/2/1999 10:25 PM

I used a 12AT7 in the driver stage of mine. I found the clean channel to start distorting real early also with a AX7. The 12AT7 really lets get up into the 5 or 6 range before going into a sweet Bassman type vibe.

I put some stuff up on my page, mainly some conlusions and observations about Dumbles I could find. And some of my project notes.

http://members.xoom.com/BoxerAmps/

enjoy, I really quite impressed with mine.

bw

7/4/1999 2:33 AM

I built the preamp into a Princeton that was previously modded by a so called amp guru, it sounded like sh**. The "Princetone" mod cost me 2 bills. Anyway, I now know enough about electronics to get me through the Dumble schematic and I have to say it sounds really good. The preamp as previosly stated stays very clean when dimed. I put a MV before the output section which is is pretty much a Deluxe and I can't here any distortion with preamp on 10 and MV on 1. When I bring up the MV the thing gets loud and breaks up the OP section nicely. I have to crank the preamp volume as well as the distortion pot to get heavy distortion which also sounds really good.I'll probably eliminate the preamp volume. I want to thank everyone for the posts regarding this amp. Now, time to start scalvaging for trannys for the output section.

Regards, Stan

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