New ODS Build - Sounding WAY Better!... Little help please?

[RJ Guitars]

RJ,

Check your presence circuit. The D'Lite layout is wrong. Make sure your presence circuit is wired the same as Dumble did it. Do not take the third lug of the presence pot to ground. Only ground the cap and tail resistor. Also, use the 4.7K feedback resistor.

My advice stands. Do not use modified schematics unless you are cloning a specific amp. The D'Lite values are based on Norm's preferences for a 22 watt 6V6 amp, with certain transformers. That is not what you are building.

You should baseling to known good Dumble values and tweak from there.

The miswired presence will make the amp a whole bunch more raw.....

Dogears thanks for the note... you've got my attention with your ability to squeeze tone out of these things. I'll be attending to your suggestions and getting the voltages on the mark ASAP.

From my picture below you can see that I have the presence to ground on the third lug. Changing that as you suggested will be my next tweak and I'll check that resistor value too.

As I've changed a couple things it's now up to decent sounding clean and O.K. in OD... but still off the mark a bit overall.

I've got to go back to work (my day job) now but tonight I'll make the presence wiring changes and see what is up.

I can now get the volume and trimmer turned up pretty high before the squeal sets in and the OD tone has potential for being satisfactory.

I've got to go back and check that OPT wiring and carefully go over the OD circuit... something is just a bit off yet and that squeal is trying to tell me something??

thanks for the help... keep sending the suggestions.

rj

[dogears]

You're welcome....

Now cut the buss from the presence pot and report back!

[Funkalicousgroove]

Why is your tail resistor from the bass pot wired to the top of the drive pot?

your presence circuit looks like there is nothing wired to the wiper?

I would Imagine that at least a portion of your problem lies in your lead dress, you should consider re-routing your OT leads, or drilling another hole closer to the Jack, I also see alot of bare leads that could easily short to ground(your bright switch for one).

[ampdork]

The presence leads as well as the middle lugs of both the OD ratio and OD level should be routed under the power supply board and under the main board to their respective places.
You have a heck of a lot of wires crossing each other upfront and the lack of shielding on the OD level.
I would shield the OD level, run the leads appropriately. I would also take the OT secondaries and get them down against the chassis. These could be coupling with the OD level or some other sensitive area up there.

If these pics were taken since the OT lead swap then they are now correct. If not go back.

The amp will indeed work with the OPT leads reversed just not very nicely.
I repaired a kit built Ruby that had this problem. It would be fine until getting cranked then it would freak out. On clean settings you could feel there was something amiss but it would not howl or squeal until getting pretty gained out.

The above suggestion are meant to be taken with a grain of salt but indeed if I were you these are the place I would focus on. In fact I would do all of the suggestions made in this thread get the lead dress as clean as possible and I would bet you'd find joy with it. Of course you might also be able to fiddle with a chopstick and wiggle a wire away from another and get it stable. For me I always find it easiest to get the lead dress as close as possible to stock and then listen to see if there are issues.
Trouble is that without a really clean lead dress you could be chasing the problem for days and then end up rewiring it anyway.... If you have one wire coupling to two others and no scope you could be driven insane trying to chopstick it away.

I'd also look at your grounds. Make sure they are read low at the solder joint or better at the components lead. Also make sure they are all in the proper places, though this is not as likely as much of an issue as the lead dress.

Hope my post isn't coming off as judgmental towards your work. That is certainly not my intent. I have just spent many hours bashing my brains out on circuits and have learned the very hard way that without a good lead dress chasing down a trouble can be a huge PITA and 9 out of 10 times it was the lead dress in fact causing the trouble for me.

[Funkalicousgroove]

Scratch my comment on the Presence wiper, I see the yellow tantalum cap, but you definitely want to get rid of that ground!

[ampdork]

Funk da man. That 10K R is most certainly not going to allow you to find joy.
I do think he has a cap wired to the wiper of the presence pot, it is hard to see in the pic though. That said I cannot see if it is actually soldered.

I'd guess the front end was perhaps the last task on this amp and the excitement perhaps got the best of our OP? I know I have been diligent in the past until the end steps where I was getting anxious to hear and play an amp.
Friday Cadillacs disease??

[Funkalicousgroove]

oh, I've screwed up alot worse than that!!

[odourboy]

Why is your tail resistor from the bass pot wired to the top of the drive pot?

Heh heh heh.. now I imagine that's gonna make her squeel like a peeg in OD.

[RJ Guitars]

Why is your tail resistor from the bass pot wired to the top of the drive pot?

Good question... and also the main reason why this thing was squealing...

My old eyes made me see something that wasn't there... the drawing is fine but I saw something and never thought about it again. I read your note and had to look at the drawing three times until I finally snapped... Take a look at the drawing and see if you can make your eyes see an optical illusion of that resistor wire jumping over to the drive pot. I made up my mind and never looked at it twice... Thank You Funk!!!

Moved the Bass pot tail resistor wire to ground - Immediate and immense improvement.

Here is a great lesson in the dangers of following the layout drawing without cross checking the schematic...

I also clipped the presence ground wire... it was a subtle difference but audible.

Now I can get down to the real tweaking... thank you all very much.

Hope my post isn't coming off as judgmental towards your work. That is certainly not my intent. I have just spent many hours bashing my brains out on circuits and have learned the very hard way that without a good lead dress chasing down a trouble can be a huge PITA and 9 out of 10 times it was the lead dress in fact causing the trouble for me.

Ampdork and everybody else... I can't say thanks enough... this forum is awesome... I could have kept everything to myself and spent the next three weeks trying to see my various mistakes... I don't feel judged at all... in fact relieved and only slightly red faced that I needed a fresh set of eyes on it.

I left a lot of wires long and untrimmed expecting to go back and tidy it all up. I just can't bring myself to clip the ultra-linear leads on the OPT or the extra speaker output leads.... Maybe have to do it anyway. I can take my time in the tweaking and cleanup now that I have it functional. It's actually surprisingly quiet now that the squeal is gone.

It still doesn't sound awesome, but I didn't really expect it to yet. At least I think it will be enjoyable to dial it in now that everything is functional...

Thank you AmpGarage Forum..

rj

[Structo]

That diagram is incorrect for the presence control.
Check one of the Dumble schematics for the right way.

[Funkalicousgroove]

Don't be afraid to wire those UL taps, sometimes they sound really cool that way.

['67_Plexi]

Just a few pieces of advice that you can take or leave.

When you've placed the last wire on an amp. Walk away, leave it for at least 2 hours, or even better leave it overnight. Don't be tempted to jump right in, you will likely create yourself hours and hours of trouble shooting without a clear mind. Plus, this is most likely time you will make a mistake that could mean a nasty shock. Excitement breeds complacency.

When you come back to the amp, you will have a clear mind. Now is the time to check everything against the drawing etc. Don't rush, it will save you a ton of time.

The next biggest mistake done by a most people is just tubing the amp up and firing her up. Do the first start-up logically, again it's safer and will save you a ton of time. Work from the power supply backwards. Start it up without any tubes and make sure no fuses blow, that you have HT voltages at all the B+ points, you have a decent range on the bias circuit, your relay circuits and auxiliary DC supply all work.
Once all this is good, insert the power tubes on their own with a bias meter if needed. Power the amp up and get the bias point somewhere near. You will need to readjust it later after all the preamp tubes have been inserted. But for now you just need to get her going. Next insert the PI tube. Be ready for a loud squeel if the primaries are wired arse ways about. Check the plate voltages on the PI tube. Keep working forward through the amp like this. It makes life so much easier and is logical.

One more hint. When the presence control squeels, it's never normally the presence circuit at fault. It acts like a detector for any instabilities in the earlier preamp stages. Lead dress is the No1 culprit. However, to avoid any possibility of presence circuit issues and to generally lower the noise floor of the amp use speaker jacks that isolate the chassis from the jack ground (eg.Cliff jacks). The heaviest currents in the amp flow through the OT secondary ground cable. Attach this directly to the ground lug of the Cliff jack, but not to the chassis at this point. This keeps the heavy speaker currents completely off the chassis. Now attach a 22 gauge wire from the speaker jack ground lug and ground it the same point the prescence circuit is grounded. Only the very light feedback circuit currents will flow from ground via this wire.

Hope this helps.

Kind Regards,
Alan Phillips.

[brownnote]

hey now...there's more than one way to skin a cat.

[RJ Guitars]

Don't be afraid to wire those UL taps, sometimes they sound really cool that way.

Oh Yeah... do you think it would add some potential smoothness, sustain, anything else good (instant Rockstar tone maybe)? Smooth singing sustain is a direction I would love to visit. Has anyone done an ultra-linear OPT on an ODS build? I'd be quite curious and I still have those leads plenty long enough to wire it up...

Also I'm curious if this is typical -- In my first 30 minutes of playing the ODS, on the OD channel when I get a get a fun lead tone then hit a chord it's just kinda muddy and ugly. I haven't done anything to really tweak the tone yet, but I'm thinking that power chords in OD shouldn't be a stretch... do i need to twist some knobs then give it time or start tweaking?

rj

[Funkalicousgroove]

It's hard to say what UL will do in your particular application, but most of the UL guitar amps that are deemed as "Crappy sounding" (fenders for one) are crappy because of other issues, and not by virtue of being UL.

Try turning your gain trigger to somewhere between 30K and 60K to ground, that may help with the "Mud".

these are not necessarily a crunchy chord chugging kinda amp like a marshall, but you should be able to get some level of articulation out of it-