Feel free to provide feed back, etc. (BTW, this will be built as a head with the trannys and tubes facing UP.) A few deviations from the typical Dumble layout:
1. Mains/Standby switches moved to the front.
2. Bias test points added and bias pot moved to the back panel
3. Mid switch changed to Treble shift (per Dogears recommendation)
Trannys are 100W Marshall PT and 80W Fender Twin OPT from Weber. If these trannys are crap, let me know and I'll throw up on ebay and get good ones.
A few suggestions that diviate from the Dumble layout, but worked great for me. Take 'em or leave 'em, just suggestions.
Put the HRM right on the main board, check my layout for the other mods to make this work, like moving the cathodes. It keeps the leads shorter and removes potential instability.
Use a switched stereo jack for the foot switch. Run the relay wires to the non-switched side of the jack, then the switched side to the front panel switches. Plugging in the footswitch automatically disables the front panel switches.
Luthierwnc wrote:I think the Send bright cap might be a little too generous.
I agree, but Norm used that on his 6V6 amp and liked it. Maybe some of his HF hearing is gone . I'm using 120pF and thinking about lowering that, it's pretty drastic.
BTW, I've updated the .jpg and .vsd with corrections. I'll put the final version in the files section after I've completed the build. (Just want to make sure it works before someone else tries it. )
I put the HRM on a piggy-back board just in case I hate it. It'll make it much easier to convert back to an '80s amp that way. I'm such a coward. I actually have another layout for a twin conversion that has the HRM on the board. I'll send you a link.
I can't help with voltages yet. (Haven't built it.) As for the 270pF on the send, that's just what was on the schematic. I'll adjust to taste once I've heard it. I do like it on my 6V6 bright switch, but usually just when playing clean on the neck pickup. It adds an almost accoustic quality to the recorded tone.
BTW, I've updated the .jpg and .vsd with corrections. I'll put the final version in the files section after I've completed the build. (Just want to make sure it works before someone else tries it. )
Thx... looks good at first glance. I'll spend some more time later.
I put the HRM on a piggy-back board just in case I hate it. It'll make it much easier to convert back to an '80s amp that way. I'm such a coward. I actually have another layout for a twin conversion that has the HRM on the board. I'll send you a link.
It is VERY different. Still Dumble but a completley different feel to it. Yoyu also have to adjust the cathode caps. Basically you drive the bass in CL1, CL2 and OD1 with 5uF caps, then drop some of it off on OD2.
I do like it on my 6V6 bright switch, but usually just when playing clean on the neck pickup. It adds an almost accoustic quality to the recorded tone.
I justs bought an ON-OFF-ON switch for my Princeton transplant. I'll use 120pF and 270pF for 2 different bright settings. I find the 270pF too much for a Strat but nice the a Les Paul neck PU.
Once again, nice drawing Norm.... cain't wait to hear the amp.
Thanks for the advice. I'll update the cathode bypass value. (With so much talk about 10uF, I guess I forgot that the HRM is a different animal.)
Tommy, YES the Hybrid-A and the HRM we're discussing are quite different. It gives me a whole new level of respect for Gary and his Glaswerks amps with their switchable voicing.
1255]http://bad-domain/97HRM/97_ODS_HRM_Loop.JPG[/img]
. I'm using 120pF and thinking about lowering that, it's pretty drastic.
)
I actually have another layout for a twin conversion that has the HRM on the board. I'll send you a link.
