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Vintage threads from the first ten years

less bass mod...

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7/5/2004 7:28 PM
nathan hiltz	less bass mod... Can someone let me know precisely which capacitors to change to get a less bass from my 5e3 (i play humbuckers and it gets a little out of hand...) If someone could tell where they are on the layout that would be great! Nathan

7/6/2004 4:51 AM
Chris - CMW amps	Hi Nathan The most common "defart" mod : - change all 0.1 coupling-caps to 0.047s - change the cathodebypass-caps on V1 and V2 from 22u to 4u7 Another "trick" is to use a 5V4 rectifier ( or 5V4-style Weber coppercap ) for a bit more tightness at higher volumes , you gotto check the biasing 'cause the plate-voltages do slightly raise . Hope this helps , keep on rockin' ! Chris

7/6/2004 6:45 AM
Tedd	I changed all the coupling caps to 0.022 for the same reason (Les Pauls). I found anything smaller than that was too much for me. I have not tried the bypass caps and will likely leave mine as is. I also added a voltage divider 33K/33K going into the second gain stage. It gave a smoother tone for high output pickups but I am going to try using a lower voltage drop ratio next time I open up. Tedd

7/6/2004 11:04 AM
Bruce /Mission Amps	In your 33k/33k mod, is one of the 33K resistors grounded and in parallel to ground with the 1M pots? Or is it 33K in series with the signal path then the other 33K grounding the grid of the first triode of the 12AX7? When I see someone write about a voltage divider I always assume one has to be grounded. Bruce

7/7/2004 6:38 AM

The second case, one in series and the other grounded. It was a late night mod that I know now is a poor solution.

I ended up removing the mod as it was making my volume knob ineffective for my strat. I put that there not thinking of how it would effect the volume control. it cuts out the effectiveness of the last half of pot travel, obvious after thinking about it. I also tried the 500K volume pot wiper to ground mod mentioned in another thread but I did not notice a change in gain. I am going to leave it stock and use my guitar volume knobs for humbucker/P-90 guitars. After playing a few of my guitars, I relinquish that this amp (preamp) works best for Fender type guitars. I think I need a tele.

After looking up schematics of other tweed amps, it looks like the Tweed Pro 5E5 was essentially the same circuit as the 5E3 using 6L6 tubes. The voltages that I get from my circuit are pretty close to those on the schematic.

I am learning the hard way, but that is the bast way for me.

Tedd

7/7/2004 11:21 AM

Bruce /Mission Amps

OK! I guess I don't need to tell you the consequences of doing that! ha ha...
Yup these were bult for Fender guitars.
The resistor to ground on the wiper mod is not really to change the gain (actually signal level, not gain) so much as it is to force the volume pots into a radical audio taper.

Just for fun, try this...
install a 470k resistor in parallel with a .001uF poly cap, from the common point of the volume controls... in front of the first grid of the 12AX7, same as where your series 33K was.
Then move over to the second 12AX7 triode and instead of a 1M on the grid make it a 330K to 470K.
For experimentaion, you can just temp solder a 680K to 1M resistor across the existing 1M.
Bruce

7/7/2004 3:08 PM
clint b	Bruce, I did the first part of the mod to my tweedy. It made a wonderful improvement to my amp. I haven't heard of changing the 1m resistor to 330k or 470k... What does that part of the mod do/sound like? Thanks, Clint

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