Finally finished 1st Dumble build

[andresound]

Before and after. Thank you to all who helped. Especially David Root and Martin Manning. 2nd Gen based on #40. Built in Lator and presence mod and a few other tweaks.

[10thTx]

How do you like the amp tone? Are you happy with it? Would you do anything different?

With respect, 10thtx

[andresound]

I love the cleans on this amp. The OD is not as good as my Express or Rocket. Very dependent on tubes. Takes pedals well (although I am not really a pedal guy). This a QUIET amp!! More than enough power for a loud drummer and I am running 5881's. I really dig the "retro" type look of the amp. All tubes are premium NOS. (telefunken, RFT, MULLARD etc..)

I am happy, but.... Still need to work on the OD.
The presence is very subtle, so might change cap value (running a 2uf with 1K pot and 100R). Otherwise,.. I will just put some band time on her and report in 6 months .

have to say, I am really digging this new hobby.

[David Root]

Looks good Andre!

Hard to say what the OD problem(s) might need to fix. What tube is in the OD position?

IME the most common problem is fizzy and/or harsh distortion. Parasitics often the cause. Fizzy can be as simple as lead dress in the OD area, maybe higher value snubbers, although IIRC yours is a 2nd gen, so no snubbers should be necessary, at least IME, on 2nd or 1st gen. Fizzy can be difficult to fix.

Being tube-dependent makes me think it could be gain related, or might improve with a tube that has less high end, is darker. The grid stoppers' values can make a difference too.
In extremis you could try disconnecting one cathode bypass cap. I've not done that but it would certainly cut gain, if that's the problem.

[10thTx]

I'll offer some mods to consider for the overdrive section. I use 5751's in my D-inspired builds and prefer that over 12AX7's.

With respect, 10thtx

[andresound]

Thanks for tips David.
I thought about removing a bypass cap. (1st or 2nd?)
The tube is an RFT.
You are correct, I have no snubbers. I tried 250p and that seemed to suck the life out of the sound. I would not say the OD is harsh, but , just not classy (best description I can find). I have a modified old TS10 to TS9/808 specs and it sounds far better as an OD. It's a pity, but I will get there.

[andresound]

10thTx,
Thank you for the info. I don't have a spare 5771 . I do however have lots of 12ax7's that probably sell for more than what I paid for the amp . I will try and play with plate resistors and bypass caps, as well as snubber's (one at a time). I also tried a little cap and resistor to ground (bleed off treble), but did not notice a huge difference.
Have thought off applying a HRM board to EQ the OD and reduce gain at the same time???? Seems like a pretty simple mod?? that way, I can roll off tops, increase bass/midrange at will... What do you guys think?

[David Root]

HRM was not designed for the 2nd gen circuit and may not work the way you might think it would.
I would try the simpler mods first.
I had not thought of a 5751 but that would be worth a try, as xtian shows. Doesn't have to be a gold pin triple mica blackplate Sylvania! They don't all cost huge $$$ especially used.
Don't shortcut with a 12AT7, yes they have similar gain but current draw is way higher and would screw up your plate voltages.

[andresound]

Thank you guys, will seek out a 5751

[bcmatt]

I have a few 5751s (new and old) that I've tried swapping into sensitive positions in my amps and I found that modern tung-sol 12ax7s tended to be less gain and quieter... sort of weird... but that may be another tube to try if looking in the 5751 area, but they aren't hitting the spot... or if you have any already.

[andresound]

Thanks guys,
I think I will start with removal of a bypass cap first, as David suggested. I tried over 20 NOS tubes in the OD last night, and not huge enough differences to warrant a fix.