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

[RJ Guitars]

I started the tweaking process tonight. I decided to tweak one thing at a time and see if I could hear the differences.

I read a few threads on tweaking and kept seeing Dogears suggestion to go to a 6.2K Feedback resistor. So I decided to give it a shot.

Either the difference was big and/or I'm growing more fond of my ODS... In general I think this tweak took a bunch of the mud out of the OD channel and made no apparent difference in the clean channel.

With a Stratocaster it gave me a lot options in the OD channel. I could actually get a pretty good selection from a subtle chunky rhythm all the way up to glowing power chords. Not really edgy and crunchy, but good stuff. The clean channel sounded basically the same as before.

With the Les Paul I had to work harder to get any sonic variety when I played chords. With the Drive cranked it was kinda sassy and I could hear a lot of harmonics that I generally don't hear in my playing. But, still maybe a bit flat in tone character compared to the Strat. With the treble turned down or on the neck pickup and the drive cranked it was fairly smooth, possibly still a bit too compressed, but way better than anything I had achieved up to this point. I didn't think the clean tone was as big and sweet as it was with the Stratocaster but I did find that there are a bunch of options in setting the tone and found several that were good... probably still a bit flatter tone that the Strat.

I may already be near the tone limits of speakers, playing, and tubes. I'm playing through an old closed back cabinet with 2 Carvin "British Series" speakers. The tubes are old Sylvania 6L6GC's and three vintage whatever I had on the bench 12AX7's. I have a set of three NOS MUllard 12AX7's that I've been holding for this project... might be time for them now.

I have to order some resistors before I can doctor the voltages... I was going to try to get 325 on the PI tube (V3)... is that the ideal value?

I'd like to get a little more feedback and lively tone with the Les Paul. I'm looking for that sound that's in my head when you guys mention "bloom"...

Any suggestions for my next tweak?

Thanks,

rj

[Bob-I]

I started the tweaking process tonight. I decided to tweak one thing at a time and see if I could hear the differences.

I read a few threads on tweaking and kept seeing Dogears suggestion to go to a 6.2K Feedback resistor. So I decided to give it a shot.

Either the difference was big and/or I'm growing more fond of my ODS... In general I think this tweak took a bunch of the mud out of the OD channel and made no apparent difference in the clean channel.

Norm suggested that I put in a trim pot and adjust to taste. Using that I was able to adjust, mark, adjust, mark and return to previous settings. It really works well.

I may already be near the tone limits of speakers, playing, and tubes. I'm playing through an old closed back cabinet with 2 Carvin "British Series" speakers. The tubes are old Sylvania 6L6GC's and three vintage whatever I had on the bench 12AX7's. I have a set of three NOS MUllard 12AX7's that I've been holding for this project... might be time for them now.

I tried those speakers and was less than happy. The cleans were fine, but the OD was a tad difficult to get a decent tone from.

I'd try speakers next.

[LooseChange]

For now, just remove the back of the speaker cab. That will help.

[Structo]

Norm suggested that I put in a trim pot and adjust to taste. Using that I was able to adjust, mark, adjust, mark and return to previous settings. It really works well.

Hmm, that's a good idea, I think I'm going to try that.

[greiswig]

Norm suggested that I put in a trim pot and adjust to taste. Using that I was able to adjust, mark, adjust, mark and return to previous settings. It really works well.

How substantially different is this from merely adjusting the presence pot? And why is the FB resistor on the Bluesmaster circuit so much larger to begin with? While I'm at it, did Adam have a navel?

[ampdork]

And why is the FB resistor on the Bluesmaster circuit so much larger to begin with?

Larger in size or value?
I have always had a theory about why that resistor is always physically larger but until the practical experience bears out something I ought to clam up about it before looking foolish.

George I have an HRM built and am working on the 100W version now. Perhaps a session soon is in order? Drop me an email or PM.

As for did Adam. I was under the impression that he preferred Golden Delicious or Grannie Smiths....So as you can see your comparing apples and oranges.

Ba-doom-tssssh....

[greiswig]

And why is the FB resistor on the Bluesmaster circuit so much larger to begin with?

Larger in size or value?
I have always had a theory about why that resistor is always physically larger but until the practical experience bears out something I ought to clam up about it before looking foolish.

George I have an HRM built and am working on the 100W version now. Perhaps a session soon is in order? Drop me an email or PM.

As for did Adam. I was under the impression that he preferred Golden Delicious or Grannie Smiths....So as you can see your comparing apples and oranges.

Ba-doom-tssssh....

We're both bananas.

Anyway, no, I meant higher in value, not size. IIRC, the Bluesmaster has a 100k resistor, versus the other which is less than a 10th of that. The pot, cap, and resistor across the presence pot change as well.

[Bob-I]

Norm suggested that I put in a trim pot and adjust to taste. Using that I was able to adjust, mark, adjust, mark and return to previous settings. It really works well.

How substantially different is this from merely adjusting the presence pot?

The presence pot adjusts how much HF is sent to ground instead of fed back. The pot in the NFB position adjusts the amount of - feedback. Completely different thing.

And why is the FB resistor on the Bluesmaster circuit so much larger to begin with?

NFB is a ratio between the NFB resistor and the tail resistor. You'll have to look at both resistors to know tha amount of feedback. I believe the BM has a much larger tail resistor.

While I'm at it, did Adam have a navel?

No.

[greiswig]

Norm suggested that I put in a trim pot and adjust to taste. Using that I was able to adjust, mark, adjust, mark and return to previous settings. It really works well.

How substantially different is this from merely adjusting the presence pot?

The presence pot adjusts how much HF is sent to ground instead of fed back. The pot in the NFB position adjusts the amount of - feedback. Completely different thing.

And why is the FB resistor on the Bluesmaster circuit so much larger to begin with?

NFB is a ratio between the NFB resistor and the tail resistor. You'll have to look at both resistors to know tha amount of feedback. I believe the BM has a much larger tail resistor.

While I'm at it, did Adam have a navel?

No.

Thanks, Bob. The differences between the presence pot and that resistance value make sense. As for the ratio of FBr to tail resistor...I'm still puzzled. If I understand which is the tail resistor, it is 24k on a stock D'Lite, and only 9k on the Bluesmaster. So if it were a ratio, wouldn't the FBr go down on the Bluesmaster?

[dobbhill]

G:

Randall covers that stuff in detail.

http://www.aikenamps.com/

Advanced technical article on designing for global feedback.

HTH,
D

[Bob-I]

Thanks, Bob. The differences between the presence pot and that resistance value make sense. As for the ratio of FBr to tail resistor...I'm still puzzled. If I understand which is the tail resistor, it is 24k on a stock D'Lite, and only 9k on the Bluesmaster. So if it were a ratio, wouldn't the FBr go down on the Bluesmaster?

No, you're looking at the wrong resistor. That's the cathode resistor, Rk not the tail resistor Rt. Rt is the 390R that goes from the connection of Rk and Rg1 and Rg2.

[greiswig]

Thanks, Bob! I looked up "long-tailed pair" and everyone talked about it, but I couldn't find one place where they said which of the resistors represented the tail.

As usual, I'm learning...

[Structo]

You have probably gone over your circuits and reflowed things but this solder joint caught my eye.
What size screen resistors are you using on the output?

Like I said, disreguard if you have addressed it.

[Structo]

This is the way I have my presence circuit wired.
Is this correct?

[odourboy]

That's okay, but I prefer this: