Fender M80 Overdrive Channel

[loudthud]

Did you mean increase C13 and C14?

Yes, my bad.

The channel is still pretty bright and what are your thoughts on lowering C7 to say 250 pf?

What ever sounds good to you!

[JSpina911]

Yes, my bad.



What ever sounds good to you!

So tonight I used a capacitor substitution box around a few places on the pcb.

I found that increasing C4 beefs the lows and low mids nicely and I Like .0047 there..

As far as C7 and C10 I don't hear any tonal (pf) changes while switching different caps across the pcb standoffs..

Something tells me I needed to tweak C8 and C9 also..The .47 caps since we changed to 10k at those resistors.

I wonder if the substitution box and leads has it's own pf readings and that makes the changes within the circuit un-noticible?

I haven't messed with the two caps across the Contour control yet but I will...

If I could get the presence control to where I can hear it,I'd be golden leaving the OD as is...It's 100% better.

Reminds me still of a TS circuit being pushed into a clean amp..Has some compression to the tone,yet cleans up nicely on the guitar volume..Nice!

[JSpina911]

A special thank you to everyone that gave me help on my Fender M80...Looks and sounds absolutely great...I have never owned a white amp and I think they look cool.

I re-tolexed this one in white and did some stuff to it...

[iamjared]

Sorry for reviving this dead topic, and forgive me if I'm way off... but I've got an M80 head in the attic that I never use for anything. I don't play 80's metal. But after looking at the schematic I got to thinking. If I took out the LEDs altogether, and replaced them with a jumper, I'd just have feedback loop symmetrical clipping, right? If I did that along with the tone shaping changes here, I think that might give a less shrill tone & also a lighter OD on the gain side. I guess there's no point, I could just put a TS in front of one of my other amps... but I can always use more projects for the hell of it.

[Cobraclutch]

I'm going to resurrect it again!!

Have had this amp for 20 years.
I was into metal and what not when I first got it, so it was usable, as that's what it is made for.
Then I used it on clean in front of a digital processor for awhile.
Then didn't touch it for 10 years.

Always thought it was a bit of a piece of crap.

But dug it out on the weekend and it is way better than what some give credit for.
Subtleness is often lost on youth!
I probably never had the gain below 7!

It's funny, I had a Digitech GNX4 on it, which was probably 3 times the price of the amp at the time, and although you can get an amazing range of accurate sounding mimic tones with that, I was surprised when I dusted that off how little I liked it.
Saturated as hell!
Back then I thought the GNX was 'the shit' and the amp was literally 'shit'.
Just listening the other day, the amp is much closer to a tube sound than the GNX.
To my ears anyway.


The clean is great, and with the gain on like 1, you can actually get a half decent broken blues tone, which is what I'm after.

Interested in doing these mods, just wondering if old mate who did them is still around?
Want to know what kind of specific success he had.

I could just put a cheap TS mini in front of it, but even then don't know what it would sound like.
I too would just like to do it for fun.

Was probably the first real amp i ever owned.
Got it at the pawn shop cheap in about 2001, would like to keep her going.

Mine was a slightly later model in black shag
Not mine pictured, but same same, minus a missing knob.

[glebert]

I had an M-80 chorus head. I really liked the reverb on that one. The clean channel was nice.

This is what the output waveform looked like on the drive channel. If you worked in the contour you could get the middle of the square wave to dip!

[Cobraclutch]

The contour is the only pot that seems mostly broke on mine, I will have to pull it out and see if I can clean it up.

It appears to just be used to scoop the mids, right?
So I just put it on zero, as I need me them blues mids.

[Ericjj99]

Hi, I'm working on the Fender M80 1x12 amp, which I've had for several years alongside other amps. This amp has a good clean channel, but the overdrive isn't very impressive, so I've been implementing some modifications. I found many of these tips on the forum.

So far, I've made the following modifications:

• Resistors: R15 and R17 (10k), R18 (690k).
• Capacitors: C4 (0.047µF), C10 (330pF).
• Op-amp: Swapped TL072CP for a JRC4558D.
• LEDs and diodes:
  • LED L1 (red), L2 (two green LEDs in series).
  • Diodes: D1 (no change), D2 (diode + red LED in series).

All components have been installed with specific holders to allow easy swapping and testing for the most suitable setup. Observations:

• The LEDs and diodes require multiple changes to find the optimal configuration.
• Increasing the value of R18 significantly impacts the sound.
• Capacitors C4 and C10, particularly C4, noticeably alter the tone.
• Replacing the op-amp with one similar to that used in a Tube Screamer has made the distortion smoother.

After 1st update.
The OD channel is much better now, I think. There have been so many changes, and some other improvements are in the planning stage. This process involves quite a lot of testing, and it's also helpful to try different guitar setups.


Next Steps:
I plan to replace R16 and R18 with potentiometers and add tone control components once the new parts arrive.


Thanks for tips!