Treble reduction on OD channel

[Fischerman]

If the amp is too bright and requires such radical treble bleeding, I'd be looking elsewhere for some issue.

Agreed...but after you've looked everywhere you can think of...twice...and you've tried a lot of the 'suggested' tweeks to no avail (some of which made the amp sound worse)...you tend to just go with what works.

[heisthl]

His first post says non-HRM.

[Fischerman]

Yes...that's why I made sure to say mine is HRM...so there was no chance for confusion.

[dogears]

My nonHRM amps are not as bright as my HRM. I do have a treble bleed on them. .001 into 500K trimmer set to about 350K.

I have either 270pf or 330pf snubbers. Always use shielded coax on the OD pots.

Also, make sure your presence control is wired correctly. On many of the layouts, guys are wiring it up with the incorrect Dlite layout. You must not take the presence pot to ground. That puts a parallel load on the tail resistor and reduces NFB. It could make the amp harsh. Do it the schematic way (or look at Dumble pics and do it that way)

Keep plate voltages low. 190V or so on V1 and 200v or so on V2.

Try a 180K feeding the OD ratio pot.

With the above setup, my amps are not bright or harsh at all. All 4 non HRM versions. Different trannies in all of them.

I do run the Skyline stack in them all and none have 100K plates.

[Pete]

Scott, you do use the 1265 speaker most of the time (recently) as well, yes?
In my experience, that helps to make the higher frequencies sound better too. Hope this isn't considered OT for this thread I just often wonder what speaker folks are using when tweeking.
Also, my experiences RE highs in OD are similar to what Scott stated above.

[BobW]

Good point Pete, and as Scott and many others have stated in the past, If you aren't using a good quality speaker such as the Heritage 1265, then your circuit tweaks are trying to compensate for a lower quality speaker response.

Start with the baseline of the HAD design, then go from there. I don't want to tell you how many hours I spent tweaking on my first build when all that was needed was a 1265 speaker, then minor circuit changes.

[greiswig]

I'm using a Celestion G12-65 which has been pretty well broken in.

[Buschman]

Also, make sure your presence control is wired correctly. On many of the layouts, guys are wiring it up with the incorrect Dlite layout. You must not take the presence pot to ground. That puts a parallel load on the tail resistor and reduces NFB. It could make the amp harsh. Do it the schematic way (or look at Dumble pics and do it that way)

This got me scratching my head. My OD has always seemed a bit harsh on my D'LIte. My OD is not bright, just raspy. It was very speaker sensitive. The only schematics which did not show the presence pot to ground were the Hybrid A & the Bassman to Hybrid RevA. Now I haven't printed out schems in a couple of months but the ODA101 & non HRM both showed the pot to ground.

I rewired to the correct way & I think it is what I was missing. I haven't tried a strat yet but I will. It is smoother & I like the way the presence pot works now. Geeze these things are sensitive! I am using a 5k pot -didn't have a 2k. Is this changing anything?
Thanks Gentlemen!!

[dogears]

If you look at the ODS101 schematics, the pot is to ground through the presence cap only!! You must not take the pot to ground directly.

Also, make sure your presence control is wired correctly. On many of the layouts, guys are wiring it up with the incorrect Dlite layout. You must not take the presence pot to ground. That puts a parallel load on the tail resistor and reduces NFB. It could make the amp harsh. Do it the schematic way (or look at Dumble pics and do it that way)

This got me scratching my head. My OD has always seemed a bit harsh on my D'LIte. My OD is not bright, just raspy. It was very speaker sensitive. The only schematics which did not show the presence pot to ground were the Hybrid A & the Bassman to Hybrid RevA. Now I haven't printed out schems in a couple of months but the ODA101 & non HRM both showed the pot to ground.

I rewired to the correct way & I think it is what I was missing. I haven't tried a strat yet but I will. It is smoother & I like the way the presence pot works now. Geeze these things are sensitive! I am using a 5k pot -didn't have a 2k. Is this changing anything?
Thanks Gentlemen!!

[Structo]

Then I hope I rewired mine right.
I ran the 1 uf cap from leg 1 to the buss and the 390 ohm resistor from

leg 3 to the buss.

Legs 1 and 2 jumpered and the NFB wire on leg 3.

Is that right?

[heisthl]

A little non conventional way to do it but effectively the same.

[Structo]

Isn't that the way this schematic from #124 shows?

[Pete]

Then I hope I rewired mine right.
I ran the 1 uf cap from leg 1 to the buss and the 390 ohm resistor from

leg 3 to the buss.

Legs 1 and 2 jumpered and the NFB wire on leg 3.

Is that right?

"effectively the same" (circuit is correct), I think the (typical) Dumble way is that the parts (cap & resistor) are on the board though.

[Structo]

How about "electrically the same"?

[Pete]

How about "electrically the same"?

Yes, sorry, thought that was said. Anyway, that's what I meant circuit is correct = electrically the same.