If I Make Only One Contribution to TAG, This Is It....

[ic-racer]

Just some background If you had not been following the posts on my #124 clone and 100k amps in general.

My findings with my verbatim #124 replica were that it is very bright and does not sound good with a semi-hollow body humbucker guitar. Conversely it sounds killer with single coil guitars (Strat, Tele, ES-135).

Gill and others have well-documented tweaks to #124 to tame it and provide a very smooth tone with a semi-hollowbody guitar (there is an awesome example below).

So here is my 'discovery:' HAD also had a tweak for #124 to give it that smooth tone with a humbucker guitar. It's the resistor/cap network built into the effects jack. It is too much of a coincidence that the resistor/cap values chosen by HAD produce a very similar effect to the tweaks of Gill and others. I think those values were chosen with the 'patch-cord-jump' as a real sonic alternative for this amp. (Rather than any sonic benefit when using a Dumblator)

Sure, it has been mentioned many times before to try this, but the thing is it really works! There is really no need to stray from the exact #124 schematic to get all the good sounds!

Gill (uses 'post OD resistor-cap' network): http://ayanmusic.com/audio/HTP2.MP3

Mine (uses HAD's own resistor-cap network on the effects loop) : http://soundclick.com/share?songid=6575515

[ic-racer]

I drew this up to try and understand what is going on. Here is a visual comparison of Gill's and HAD's post OD circuits.

[skyboltone]

Woohoo! So that's one strat/dumble tone. I'm impressed. Scheme copied and duly noted. Thanks

Dan

[dogears]

How are the loop network ( a high pass RC network) and Gil's post OD treble bleed similar? They are opposites. One cuts highs and the other is a high end pre-emphasis. No relation between them. In addition, make sure you have the ratio feeding the 1M master before hitting the PI.

Although I guess cutting some lows, ala the RC network, may be smoothing things for you.

Clips are nice btw.

[ic-racer]

How are the loop network ( a high pass RC network) and Gil's post OD treble bleed similar? They are opposites. One cuts highs and the other is a high end pre-emphasis. No relation between them. In addition, make sure you have the ratio feeding the 1M master before hitting the PI.

Although I guess cutting some lows, ala the RC network, may be smoothing things for you.

Clips are nice btw.

It really floored me when I heard it. The sonic effect is not easy for me to quantify.
It sounds so good, making me think these are not haphazardly chosen values.

Forgot that master in the schems, but was just curious how two dissimilar circuits can have a similar sonic effect.

All the single coil guitars I tested sounded good with the patch cord out and sounded bad with the patch cord in.

All the double coil guitars I tested sounded good with the patch cord in and bad with the patch cord out.

Could be a coincidence, but I would like to believe it was made to work this way by HAD.

I'm still amazed by this. A week ago the amp was just some average sounding thing I cobbled together, easily eclipsed by my Super Twin project. Now that it is back to #124 values, and I think I know how it is to be used, I think it is a grail tone monster.

[ic-racer]

Here are the prior clips, arranged by guitar and patch cord presence for easier comparison:

Gibson Double Coil Semi with NO patch cord: http://soundclick.com/share?songid=6564969

Same guitar as above but WITH patch cord in effects loop: http://soundclick.com/share?songid=6575515

Telecaster with NO patch cord: http://soundclick.com/share?songid=6573528

[jaysg]

hmm...so to clarify, you're talking about the 220K||250pF on the Send Jack? Use a jumper and it's in -- which you prefer for your humbucker guitars. Are both clips done with the same pickup? W/O sounds like the bridge and W/ sounds like the neck. (They both sound great to me...just different)

[ic-racer]

hmm...so to clarify, you're talking about the 220K||250pF on the Send Jack? Use a jumper and it's in -- which you prefer for your humbucker guitars. Are both clips done with the same pickup? W/O sounds like the bridge and W/ sounds like the neck. (They both sound great to me...just different)

All correct. In terms of the tone, that bright one with the humbuckers would be OK if you were going for a bright blues tone with presence up and treble up, but as I recorded it, all tone controls were in the middle with bright off and these were the same settings for the other humbucker clip. Both with the bridge pickup.

I'll will try to make a clip where I plug and unplug the 220k/250pf loop as I am playing.

[rfgordon]

ic-racer,
I am deeply indebted to you--I popped the 250pF/220k combo into my amp at the entrance to the PI cap...and...SHAZAAM!!! It released the CrocoDLite's inner Dumble! Most excellent, dude.

Again, thanks for the tip.

[Structo]

ic-racer,
I am deeply indebted to you--I popped the 250pF/220k combo into my amp at the entrance to the PI cap...and...SHAZAAM!!! It released the CrocoDLite's inner Dumble! Most excellent, dude.

Again, thanks for the tip.

Could you explain a little more how you implemented this?

[rfgordon]

No problem to explain.

In my amp I have installed, post Master, the IronSounds loop card, so the ouput of the loop card goes to the PI input capacitor.

I soldered the cap (actually two: 150pF + 200pF ceramics) across a 220k cf resistor. I un-soldered the shielded input to the PI, put one end of the new R/C into that eyelet, the other into another eyelet, and put the wire into this second eyelet. So the signal comes from the loop card >> thru the 250pF/220k part >> into the PI entrance.

Because I use the IronSounds loop, I don't have switching jacks to put it on, so it just precedes the PI entrance cap.

I wouldn't have believed such a simple mod could have such a profound impact on the amp's personality, but it did. After installing this, I found that if I adjusted the OD entrance trimmer, there was a nice sweet spot where the Dumble squeaky attack was best--it was, actually, at a higher setting than I'd been using.

So anyway, I'm much happier with the amp now. It goes out with me Saturday to play a gig at, of all things, a bachelorette party!!

[brownnote]

Hey Tom, on your D'Lite build with passive FX loop it's a really simple addition.
You solder the 220K/270pf R/C from the 'tip' of the PRE/SEND jack to the 'switched' lug of the PWR/IN jack.

http://brownnote.net/shared/images/loop/loop3.jpg

[greiswig]

Okay, I give...I tried it because I had the amp open anyway, and even made it so I could short across it (temporarily), but I couldn't hear much of a difference between when it was engaged or not so I took it out. Maybe a little bit tighter bass.

What is this supposed to actually do?

[ic-racer]

What is this supposed to actually do?

This explanation is somewhat a stretch of the imagination, but here goes:

It is like "Smooth and Slim" for the ODS 124

I have never heard a "Smooth and Slim" but after reading about it's effects on the Mesa Mk I's flabby bass notes, I thought I heard a similar effect on the 124; the tone seemed smoother and slimmer.

Maybe a better way to look at it is that if you amp has a bright, coarse distortion, the 250pf/220k will smooth it out. If you already tweaked your amp to get a smooth distortion, the extra 250pf/220k may sound bad. My single coil guitars do not sound good with it. The Telecaster in this clip ( http://soundclick.com/share?songid=6584689 ) was recorded WITHOUT the 250pf/220k. To me the 250/220 sounds best with double coil guitars, but I'm still experimenting with it.

[greiswig]

Thanks, ic-racer. I've got a Smooth & Slim, as I used to use Boogies. The effect that unit had (from my recollection) was not so much on the brightness but on the lows. An ancillary effect was that cutting off some of the low end also made the amp distort less at the same settings.

On V1 I have 100k/150k plate resistors with 4.7uF/1uF bypass caps. On V2, I'm using the higher plate resistors with 5uF caps. I got those bypass cap values by ear, and they are what get me a lack of mud while still having the jumper across the bass pot (i.e. no bass mod).

I suspect that part of the reason I didn't hear anything was that I'm already cutting off a lot of the lows that the 250pF/220k R/C pair is supposed to do. But I'm surprised you hear a difference in the brightness.