First clips of the 3 channel amp

[Bob-I]

I'm not at all happy yet, but I thought I'd share. The Fender Clean channel sounds good, the ODS channel is a bit brittle and harsh, almost SS sounding. The Dumble clean channel basically sounds like the Fender so I didn't record it yet.

http://www.patmedia.net/bob-ingram/Dumble/ODS1.mp3

http://www.patmedia.net/bob-ingram/Dumble/Clean1.mp3

I have to figure out that hum, it's output section only as it doesn't change with preamp settings. I suspect heaters in the PI area. Also I get some oscillation at higher reverb settings.
'
Heading out on a week long business trip so tweaking will have to wait. Suggestions welcome.

[Normster]

The clean clip was just gorgeous! Nice touch on the playing as well.

The OD was kinda harsh. Of course, I have no doubt that you'll get that sorted out in short order. (Not running JJs in V2 and V3, are you?) Congrats on getting it up and running!!!

[Icetech]

Very nice bob:) im gonna be sending you my amp to finish:) right now my clean channel sounds like the OD should.. and the OD channel sounds WAY over the top in gain

[oldmacman]

Clean sounds great! Good playing as well.

OD sounds gained up a bit much - where do you have the input trim and the drive controls?

[pedro]

Hi Bob - good work, I know you'll get it fully sorted based on your guidance to me.

FWIW - when I'm thinking about and considering distorted tones I like to think in terms of "grain size" ( I claim that one, Scott ! ) to weigh up the OD characteristics.

At moment I'd describe the OD tones as having pretty large grain size and your objective being to reduce the size of the "grains" to smooth the peaks. Hope that makes some sense ? !

Really like the "warmth" of the clean channel so far - was that on fairly lowish volume Bob ? Theres a lovely "sheen" right at the top of the tone which is very promising I think.

On the OD channel - how was the presence when you recorded the clip, and what output TX ? - I found on my build so far that the output TX makes an enormous difference to the presence characteristic - one output TX very harsh, and one much smoother in the presence area. Dont claim to understand it, but know it to be so.

cheers
Pete C

[dogears]

Clips osund great Bob. I hear potential in the OD clip. A bit over the top as others suggested, but I heard some nice low end stuff too. :23-:24 sounded really great to me. It had that low end grain that is elusive. It has potential!

Email me with your OD section preamp values and I'll see if I can help.

[Bob-I]

Thx guys. Yes I agree it has potential.

Scott I'll get you those values later this week, I'm on a business trip for the next 3 days. That section you mentioned was using the neck PU. This clip was recorded using my Spirit Steinberger that I use as a test instrument. It's tiny so I leave it out, I can grab it quick to test amps. If you can read this....

http://www.patmedia.net/bob-ingram/Dumb ... ematic.jpg

You can get the values.

Pedro, interesting analogy, yes it's at very low volumes because my lazy kids were still sleeping at 1:00PM . I like that, grainyness is a good way to describe this. Yes, I need to get the grainyness finer.

Also, I plan to use NFB on CL2 but have not yet added the components.

Also, the bass control on the Dumble side is not very effective. I haven't used any of the additional switches yet, just the TMB ckt.

[dogears]

Bob,

Try raising the resistor, over the 100k trim before the OD, to a 180k or 220k. Try a 470pf grid bypass of the CL2 220k grid resistor. Raise the snubbers tp 390pf to 470pf.

Try lowering CL2 to a .02uf

OD1 should be a .01 and OD2 a .005 (.0047)

The OD2 plate is 150k and the cathode 2.2k

Only CL2 gets a lower value bypass cap. 4.7 on CL1, OD1 and OD2 I like 1.2uf to 1.5uf on CL2

100k over the OD drive pot and 150k over the OD level pot. Measure the pots. If they are slightly low, you can compensate by using a slightly larger resistor like a 110k or 160k.... The pots are linear taper. The schematics were deliberately wrong according to my inside source.

A .001uf cap across the bass pot will smooth the grain out. Try the Skyliner stack. I like to add a switch to go from .047 to .01 midcaps. 150k slope helps. Ditch the 70s stack IMO.

Measure some 330pf trb caps and choose one that is under 330pf. I like 315pf or so... It is noticeable.

Don't worry about the CL2 local feedback. With the Skyliner stack, the amps sound great with none! Try it.....

Let me know how it goes!

[dobbhill]

I was looking at the schematic and saw that your midrange control on the Dumble preamp was wired wrong.
D

[Bob-I]

I was looking at the schematic and saw that your midrange control on the Dumble preamp was wired wrong.
D

Yes, I noticed that too. I'll fix it as soon as I get home from this trip. Thx.

[Bob-I]

... It is noticeable.

But I ain't got dogears.... you notice things others never would.

I trust you though, you got my Crumble sounding like a million bucks.

Don't worry about the CL2 local feedback. With the Skyliner stack, the amps sound great with none! Try it.....

Really? I really like the NFB on my other amp. I'll try it both ways.

Thx Scott, I'll let you know.

[llemtt]

Bob

given the schematic your amp sound exactly as expected

you run all the preamp through the 3.3Meg/10p of the reverb mixer which give the characteristic bright Fender sound so:

Fender channel sounds "Fender" -> this is ok

Dumble clean sounds almost "Fender" -> this is nok you loose typical D clean fatness, it's another Fender pre only slightly different

Dumble od has lot of presence -> not the typical D sound but if you like it..

If you want all three preamp through reverb you should at least switch the 10p cap in and out between F and D, a better solution would be to implement a dedicated reverb circuit for the D preamps.

Teo

[glasman]

you run all the preamp through the 3.3Meg/10p of the reverb mixer which give the characteristic bright Fender sound so:

Fender channel sounds "Fender" -> this is ok

Dumble clean sounds almost "Fender" -> this is nok you loose typical D clean fatness, it's another Fender pre only slightly different

Dumble od has lot of presence -> not the typical D sound but if you like it..

If you want all three preamp through reverb you should at least switch the 10p cap in and out between F and D, a better solution would be to implement a dedicated reverb circuit for the D preamps.

Teo

Another idea would be to mix the reverb and dry signals right at the input to the PI. Lower the 3.3M to somewhere between 100K to 470K and add a 470K series resistor on the output of the reverb recovery amp to the PI. This will lessen the effect on the "D" tone and still give a very usable reverb.

Gary

[Bob-I]

you run all the preamp through the 3.3Meg/10p of the reverb mixer which give the characteristic bright Fender sound so:

Fender channel sounds "Fender" -> this is ok

Dumble clean sounds almost "Fender" -> this is nok you loose typical D clean fatness, it's another Fender pre only slightly different

Dumble od has lot of presence -> not the typical D sound but if you like it..

If you want all three preamp through reverb you should at least switch the 10p cap in and out between F and D, a better solution would be to implement a dedicated reverb circuit for the D preamps.

Teo

Another idea would be to mix the reverb and dry signals right at the input to the PI. Lower the 3.3M to somewhere between 100K to 470K and add a 470K series resistor on the output of the reverb recovery amp to the PI. This will lessen the effect on the "D" tone and still give a very usable reverb.

Gary

Hmmm.... so if I understand you right, I'd move the dry line from the input of that last gain stage to the PI input right after the PI input cap. I'd also make the adjustments you mention to the resistors and add the series resistor, I'd assume AFTER the PI coupling cap, is that right?

Thx.

[glasman]

Hmmm.... so if I understand you right, I'd move the dry line from the input of that last gain stage to the PI input right after the PI input cap. I'd also make the adjustments you mention to the resistors and add the series resistor, I'd assume AFTER the PI coupling cap, is that right?

Thx.

You want them to SUM BEFORE the PI input cap. With respect to ground there is -50 to -60 volts on the PI grids.

Take a look at this... same idea. Yours should sound better.



The summing point goes into the PI input cap. With the 12AT7 drive and two stages of recovery you have should make a great sounding reverb.

Gary