I put this amp together this weekend based off Normster's 16x8x2 layout basic D'lite amp I think.
Do not look to close it was engineered, holes drilled as I was building.
This is a custom rjguitar aluminum Princeton chassis. I decided to go with Mojo's Heyboer Marshall tranny set so I can see if I want to go with EL34's. I prefer 6L6 but well see when I get to tweaking.
I can see why you guys love these Dumble type amps. I probably should have increased the main filter caps to 100uf and can at some time. Played it through my bench cab 1-12 so tomorrow I'll try the 412.
Mark
Edited my poor English
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Last edited by M Fowler on Mon Apr 11, 2011 3:21 pm, edited 1 time in total.
Thanks, these Dumbles are not easy to build with all this wiring and cap/resistor choices out there.
In Normster's layout attached is that 22m/.047/22m on V1 for bass emphasis?
I am also working on which snubbers to use, right now I used 250pf mica because I didn't have 270pf ceramic. Also, reading more on the OD trimmer and where to set that.
Mark
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When (if) I ever get this mini HRM/86 Special finished, then that is my next build - a Normster-style 6V6 - I've got a 17" x 8" x 2.5" chassis ready and waiting.
It must have taken me one weekend to drill and cut the chassis for the 86 alone
The cab? Probably 24 working hours. I might need to speed up a little
I have not started on the cabinet yet, that will slow me down a lot especially trying to do my own tolexing for the first time.
As far as the amp it looked like the picture below on Friday night. You can see I had a head start with the faceplate drilled, IEC, and fuseholder done. I was trying to figure out space requirements in this picture.
Fun project though.
Mark
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What about the presence circuit? Did you follow the Dumble correct circuit? Or the original Dlite with the messed up (IMO) pot hookup?
If you are using 6L6 tubes, I'd make sure to do the Dumble style presence and NFB.
It looks like you connected the ground bus to the presence pot. This is a mistake. Disconnect it and hook up the 390ohm and cap to ground leaving the pot ungrounded. Much much better IMO and correct.
Looks good Mark.
Scott is right, the D'lite presence wiring is wrong.
The .05uf cap and 22M resistors is a local feedback loop on V1b.
A lot of us put a toggle switch on that. Run the switch from ground to the grid side of the cap between the cap and resistor.
Without the LNFB the tone is a bit more raw, unfocused.
Set the OD trimmer to 25-30K, wiper to ground with the OD switch on.
It's a matter of preference.
The higher you set it the more saturated the OD is.
On the V2 snubber caps, the higher you make those the more top end is carved off. Kind of a subtle thing but between 250pf and 330pf is where most go with that.
But, #183 has 25pf snubbers, so go figure although that is an EL34 amp.
The other thing to play with is the bypass caps, usually all 5uf.\
10uf and above can make it a bit muddy or bass heavy.
Another area to play with is the GNFB (presence) resistor.
The 4K7 is usually used with four 6L6 so you can go higher with that with two power tubes.
Like a 6K2 or 8K2, some even like 10K there.
Also the cap, 1uf- 2.2uf
Another question is there a BOM anywhere on the forum for this amp, the only reason i ask is it's a little tough to read some of the coupling and tone caps values.
Taylor, oh yeah this amp has been fired up since Sunday and I am having fun playing around.
Once the honeymoon is over I have to take care of the issues Scott and Tom were talking about. So make sure you note how the presence pot should be wired up when looking at the D'lite and Normster layouts.
Mark
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M Fowler wrote:Thanks, these Dumbles are not easy to build with all this wiring and cap/resistor choices out there.
In Normster's layout attached is that 22m/.047/22m on V1 for bass emphasis?
I am also working on which snubbers to use, right now I used 250pf mica because I didn't have 270pf ceramic. Also, reading more on the OD trimmer and where to set that.
