choke and preamp tone

[swt]

sorry 'bout this silly question...i have just finished the amp for a friend. It's a dumble hybrid A non HRM, with added dumbleator/tut loop, ( thanks guys ). I've used the same components/brand/tubes and voltages as the one i have in my own amp. But the preamp is really middy. it lacks the complexity of the other pre. I have a choke+100ohms resistor in series in the rich one, and a 470ohms resistor in the lifeless one. Can this be the cause?. Or should i look somewhere else?. Thanks for your guide...

[dogears]

That's not it. The tone will be a little different, but I wouldn't call it lifeless!

Do you have the same loop in both?

What preamp tubes?

What size CL2 bypass cap?

[Bob-I]

That's not it. The tone will be a little different, but I wouldn't call it lifeless!

Not at all, in fact the amps where I use a resistor instead of a choke have more harmonic content.

Do you have the same loop in both?

What preamp tubes?

What size CL2 bypass cap?

Can you verify the components? Something is different for sure and it's not the resistor.

[swt]

some facts: i'm using the same power amp for the two preamps, so i can really hear the difference. i'm using the same components out of the bag, EH12AX7 tubes, and trying to reach same voltages. Only differences: resistor instead of choke, 10k metal film instead of carbon, in the dumbleator cathode follower in the lifeless amp. That's it...tone is really lifeless, too middy, no rich harmonics or bass, tried to swap tubes, but with minimal change in tone. Also metal films on ps chain...can this affect tone?. Thanks a lot!

[Luthierwnc]

I'm with the other guys. My first build has a choke/resistor option and I prefer the resistor. The power supply resistors shouldn't contribute that much either. The audiophile rap on MF is that they are too brittle which is the opposite of your mud.

So you know you aren't alone, I often piggyback two amps so I can test different parts of the circuit against "known good" versions on the other. Make a pair of jumper leads out of coax so you can ground the shield. Mine have the little hooks that press out to keep the contact area small.

How does it sound with the D-lator unused?

Skip

[dogears]

I use a 390ohm choke replacement resistor fwiw....

[Darkbluemurder]

How does it sound with the D-lator unused?

Skip

+1. With these problems the only way to go is to isolate and eliminate.

Is the clean tone lifeless, too?

BTW I had a bad sounding Marshall which sounded middy no matter which circuit I tried in and no matter what guitar was used with the amp. Turned out to be a wiring mistake on my part. When I replaced the OT I twisted all of the primary wires. This is wrong. Only the wires going to the power tube plates should be twisted but NOT the wire going to the B+. When I separated this wire the middy sound was gone and it sounds like a Marshall again. Different guitars produce distinctly different sounds now.
So you should make sure that the B+ wire is not twisted with the other OT primaries.

[tictac]

Take a look at the "Robben Ford" Switch post. You can put a standby switch in there that allows you to switch between either the choke or the 470 ohm resistor.

The choke (mine is w/out a 100 ohm in series) is a more agressive sound especially in overdrive mode. But now you have the option of switching to either mode of operation making it a tonal choice rather than good vs bad.

TT

[swt]

i wanted to go from ground on...so i'm only testing clean pre, and going from dumbleator send to the return input on the other amp. both pre are tested that way. today i'm going to try soldering the exact parts...by the way...the leads are all twisted ...i'll try that trick...i didn't know 'bout that...

[Darkbluemurder]

...by the way...the leads are all twisted ...i'll try that trick...i didn't know 'bout that...

Me neither until a generous fellow at the Metroamp forum pointed me to it.

[swt]

one chassis is aluminum, the other, steel... can this be changing the sound??

[Easy]

SWT: Just want to let you know I've had this happen to me. Built two amps for friends. Sounded GREAT. Built the same amp for me and ... eeyewww! middie, crappie sound. replaced every single part, most sections of wire, pots, trannies. Still ugly. Different chassis, although it's still steel (as the other two also were). I'm watching the responses of the kindly gurus here with great expectation.

[Darkbluemurder]

one chassis is aluminum, the other, steel... can this be changing the sound??

Yes, it can change the sound but not as much as you described. All my amps have steel chasses and - apart from the miswired Marshall - sound fine. I have never had the opportunity to try an aluminum chassis.

Check whether any of the grid wires (i.e. any wire that is after a coupling cap) runs in parallel with a plate wire, a high voltage wire or an OT wire.

Good luck!

[llemtt]

bad tube socket?

bad wiring cable?

teo