Fender Frontman 15R mods

[Renegadrian]

just two easy mods and it's more usable.
r12 10k cures the volume bump.
r22 has to be lowered I now have a 120k. still too much gain when maxed but hey i's better than before...
Still I'm not satisfied with the sound...I hoped it could give out something more 'true' not sterile sounding.
Any hints?!

[Mark Hammer]

That's a job for Stabilant 22.

I've never tried products like that.  Any success stories with pots?

The person who initially recommended it to me did so primarily for pots.  He runs a busy (and occasionally award-winning) studio, and uses 2" tape for master recordings and has a mixing desk with 6" faders.  So he needs absolutely crackle-free pots.  The stuff used to be marketed to audiophiles under the brand name "Tweak".  The assumption was that you'd use it on your RCA jacks and such, but as the corporate appnotes pages shows, it has much wider application than that ( http://www.stabilant.com/NoteList.html#appnotes )

At the time (15 years ago) a local retailer had a bin of 1/2ml "sampler" vials for 50 cents a pop, so I snapped up a bunch, and am glad I did.  I'm down to my last two, now.  The stuff is bloody expensive, but works like divine intervention.

Imagine a paved road.  Fresh asphalt is dead quiet to drive on, because your tires make perfect contact with the surface at all times.  Flash forward a couple of years, and the road will be noisier because of all the stuff/gravel on top.  Sweep all that stuff away,and the noise will be lower but there will still be noise because cleaning the surface does nothing about the pits that have been created.  Stabilant acts as a contact enhancer, rather than cleaner, because it fills in those pits in the resistive strip, recreating continuous contact between wiper and resistive strip.  Ideally one uses it with contact cleaner in complementary fashion, after having shpritzed in contact cleaner, and allowing the pot to dry.  The cleaner may remove oxidation from the wiper, and sweep away any residue on surface of the resistive strip, but does nothing about the imperfections/pits in the strip created by rubbing the wiper against it.  Stabilant remains viscous for the life of the product, be it pot, switch, edge-connector, conductive contact (e.g., TV remotes), but because it does not dry, you can't build up coats/layers.  Within those limits, however, it's a pretty impressive product.

I've brought all sorts of stuff "back to life" with it, and successfully quieted plenty of pots.  If I have a microSD that doesn't seem to be behaving reliably, I wipe a bit on the contacts, and I'm back in business.  And because its viscosity doesn't go away, I'm surprised that no manufacturers take steps to pre-treat high-use pots with the stuff.  The vials/containers come with plastic applicators.  I find for a typical 12mm Alpha pot, you're looking at 2-3 sesame-seed-sized droplets to cover the entire surface of the resistive strip.  It can be diluted down to a 6:1 ratio with isopropyl alchohol, and can be purchased prediluted or full strength.

What is a complete mystery to me is why it doesn't conduct "sideways".  If I've smeared it over the entire surface of the resistive strip, and it behaves like a liquid solder joint between the wiper and resistive strip, how come it doesn't conduct along the resistive strip from one end to the other? 

In any event, back to the thread, already in progress....

The network formed by R16-18/C9-10 is largely identical to the midscoop filter found on countless fuzzes, intended to provide "doom" sounds with big bottom and sizzling top in the overdrive channel.  The "big bottom" leaves something to be desired, and the sizzling top just adds stridency, rather than character.  The value of C10 should probably be lowered a bit to raise the corner frequency of the bass side and make it a little more vocal-sounding, and there should probably be a fixed resistance in series with C9 to reduce the shrillness. I'll suggest .022 for C10 and 2k2 for the added resistor.

[Steben]

Hey guys. Just found a 15R for 15 bucks. I thought it was a good price even for the hardware alone.
How did this work out? Is the amp dead or used as fire wood?
Very keen in using those volume and gain control mods.

The drive circuit does sound harshly edged. But I have my own thoughts about that.
In the 15R it's very harsh IMHO mostly because of the speaker and cabinet.
Yet a FM 212 has the same clipping and does retain some of the harshness.
But it is not only harshly edged. It is budget shaped.

What we forget perhaps is the fact stompbox circuits are not used as always on effect that often. An amp is. Especially a small amp with no remote switching.
--((At this point I dream of a simple small SS one channel amp that has great tone. Designed, measured, emulating the good stuff. Completely non existent except for the quilter stuff))--
This means every one trick pony element popping up in the drive section makes the image of a bad tone.
We use stompboxes with much harder clipping than that every day. No one complains. It is not the diode choice.
Seriously, taking out the drive circuit and making it into a dirt pedal might just work much better.

How many dial back the volume for a clean tone an a rat? Are you satisfied? Well, a rat is not an amp you say? Exactly.
Simple "opamp and diode clippers" usually have a fixed treble cut and usually this relates to the gain setting. Yet with any higher gain setting the clean character of a backed down input gets muffled. Solving this would render any SS circuit much better.
A fuzz face solves this with lousy input impedance which eventually gives great dynamic tone range. Alas with some compromise in signal/noise ratio at lowest guitar volumes.

The network formed by R16-18/C9-10 is largely identical to the midscoop filter found on countless fuzzes, intended to provide "doom" sounds with big bottom and sizzling top in the overdrive channel.  The "big bottom" leaves something to be desired, and the sizzling top just adds stridency, rather than character.  The value of C10 should probably be lowered a bit to raise the corner frequency of the bass side and make it a little more vocal-sounding, and there should probably be a fixed resistance in series with C9 to reduce the shrillness. I'll suggest .022 for C10 and 2k2 for the added resistor.

Mid cut or bass boost before drive is found a bit in de BD-2 as well. It's far from the classic approach. The opposite of a treble booster.
I ran a TB in front of the 15R and it sounded so much more fun. The BJT non linear violence kills the low harmonic opamp sterility as well of course.
But I do wonder: why did they put that EQ section in front of the clipping? For modders to have pins in the board for experimenting?
No speaker upgrade can fix this issue.

C11 is not "that" bad, it gives 3.3kHz corner freq at full gain. But you might want that even lower. Especially on a 8" speaker. And let's not forget: that's on full gain. Lower gain settings are more than enough here. Perhaps raising both C11 and R19 values might be better. Am I getting old or is it common sense by experience that brings me to advice lower gain on amps? More gain is easy: use a pedal, booster or EQ's as "channel". My max gain standard these days is a peavey bandit clean channel maxxed out on the t dynamics. No shredding there.
This small amps seem to be designed for super high gain because that's what those palm muting power chord youngsters want that buy these starter amps.

To me, it is an ideal platform to experiment with SS circuits and try external speakers.

r22 has to be lowered I now have a 120k. still too much gain when maxed but hey i's better than before...

I'ld lower the gain in the stage before as well. Needs less change in the clipping stage.
Still, one might need change to 120k anyway. Thing is, there is interference with the effectiveness of the 220k soft clipping resistor. The lower R22 gets, the less pronounced the "early" soft clippers are.
This might need lowering as well to ... 120k perhaps. Tons of possibilities. I think of asymmetry.

Here a first step:

[Steben]

Only opened the back and put a TB in front. No mods.
Treble on amp on 1. So what one hears is some non linear addition by the booster, PRE-mid boost and amp distortion followed by treble cut
15 bucks (without the booster). Now on to getting that INside...