I found plenty of posts talking about Gil's OD entrance mod. I definitely found the values but the configuration of the 2 components are not clear to me. Here are the values:
ayan wrote: ↑Sat Jul 05, 2008 10:22 pm
For what it's worth, "my" mod is .0047uF (4.7 nF) // 4.7Meg. I don't use it in the amp(s) with 100K plate loads, but I did use it in the amps with 220K/150K plate loads. If you play a Strat and or a "phat" humbucker guitar, like a 335, you will probably like it or some variation of it. If not, don't worry about it.
...
Cheers,
Gil
So I know the values of the resister and cap. I know that they go after the relay right at the entrance to the OD circuit. Does "//" mean "in parallel"? I thought that symbol was "||". Or, another post implied that the cap is in series and the resister goes to ground.
Here's another post by Gil that helps clear things up:
ayan wrote: ↑Tue Aug 11, 2009 5:57 pm
What I did -- and never in an amp with 100K plate load resistors -- is put a .0047uF (so, 4.7nF, NOT 47) in PARALLEL with a 4.7 Meg resistor before the 220K pre OD trimmer (100K).
Cheers,
Gil
I take it back. I played with the chassis open, using an aligator clip to jumper over the 4n7||4m7. I confirmed my component values. I cannot hear any change in tone at all. Did I do it correctly? Maybe I should try Marshall values (470p||470k)?
IMG_4100.jpg
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I build and repair tube amps. http://amps.monkeymatic.com
Yes! The 470p||470k peaker did the trick! I love this. Really cleared out the mud and congestion. I built this amp in 2017, and tried half a dozen times to tune the OD to my liking. Glad to finally make progress!
I build and repair tube amps. http://amps.monkeymatic.com
Glad to know that you had good results. I went to Frye's today to buy these parts and they did not have them so I will be ordering from Mouser. I will also order the Marshall values that worked for you. I've found that Gil's suggestions tend to work well for my ears so I'm encouraged that this worked on your 183.
Another 183 issue that I am trying to tweak is that based on the amp's tone control settings, I sometimes get a little overdrive fiz with a strat. I've seen posts that mentioned another of Gil's mods for that:
Treble Cut mod: 0.002uF cap with 250k trimmer after 180k resistor going to OD Volume (Ratio).
Since it is a treble cut, I'm assuming that the cap and trimmer are in series going to ground. I also plan to try this out. Unlike the mod that you just tried, this one does not require any circuitry in the amp to be soldered or unsoldered when trying it out.
xtian wrote: ↑Fri Jul 10, 2020 4:08 am
Yes! The 470p||470k peaker did the trick! I love this. Really cleared out the mud and congestion. I built this amp in 2017, and tried half a dozen times to tune the OD to my liking. Glad to finally make progress!
xtian wrote: ↑Fri Jul 10, 2020 4:08 am
Yes! The 470p||470k peaker did the trick! I love this. Really cleared out the mud and congestion. I built this amp in 2017, and tried half a dozen times to tune the OD to my liking. Glad to finally make progress!
Now you have a HRM entrance
I already installed, then removed an HRM stack! Maybe now, with the peaker in place, the HRM would sound better...
I build and repair tube amps. http://amps.monkeymatic.com
talbany wrote: ↑Sat Jul 11, 2020 3:55 am
I will send him a quick text maybe he can comment further..
Tony
Yes you did, Tony. I don't have much to add that hasn't already been said about this. As far as the "bass reducer" network, the intent was to shave off some of the bass - duh! The effect was kind of subtle, but noticeable. I used it back in the day when I favored the "classic" tone stack over the Skyliner. My whole approach back then was to keep the overall sound of the amp more focused. I eventually ditched the classic and went with the Skyliner tone stack and took out the mod. I think over time I relearned to use to use the tone controls to get what I wanted. I'll note that, to me, the "Marshall style" network is similar in that it uses a resistor in parallel with a cap. However, I consider the Marshall thing to be a treble enhancer, as opposed to a bass reducer.
As for the treble bleed, I used that too, and eventually got rid of it as well. This was a more involved thing because the treble bleed also kills some of the good stuff while killing brightness on the lead channel. Things that helped being able to successfully get rid of it were: proper orientation of coupling caps (paramount) and... use of selected components (resistors and caps) throughout the preamp. This is also paramount, but a much deeper rabbit hole. I'll yield the floor to my dear friends Tony and Jelle, without whom I would have not been able to pull this off. I wrote threads when I gutted and rebuilt my two amps with new parts and you can find them here. It was a lot of work, maybe even harder than building an amp from scratch, but totally worth it to me.
Thanks Gil.
Over the past several months I may have been reading your posts in the wrong order.
I have been manipulating the tone controls on my both my strat and amp to finesse the OD tone using suggestions from you with good results.
I am able to get both clean and OD sounds/tone that I love. The problem is, I set up the amp and guitar for clean tones that I love but when I switch in OD I find that I need to back down the treble on the guitar a bit as well as adjust tone controls on the amp. Not the end of the world but there's nothing wrong with trying to make something better.
When I came across your old entrance and treble cut mods I was hoping that I was on to something that might require less tweaking when I switch to OD mode.
Just to be clear, my issues are only with a strat. Not so much with a tele or 335.
