tone control range on a #124 build

[wjdunham]

I took my 124 style amp over to a friends house to let him try it out and compare it to a few of his other amps (Mesa Lone Star being his favorite). He has played a few Fuchs and a Two Rock, although he didn't have any in the house at the time. Anyway, his overall comments were that the amp sounded pretty close to what he thought a D style amp should sound like with the EQ controls set pretty much straight up, but that the tone controls, especially the treble and mid, didn't really do much. With his other amps, if the treble is turned off there is a pretty drastic high frequency rolloff, not the case with my amp. The amp is straight skyliner with all the values shown in the 124 schematic, my cap on the mid switch measures about 330pf so it's a bit bigger than the 300 shown. .01 midcap and 250K mid and treb pots, linear taper. Is this typical, or is it a sign that something else might be off? What might I check/change?

He also thought the amp could have been a bit brighter overall, I have a 15pF bright cap on the master, so I could go up a bit there, but with the controls not having much effect he thought that might be an issue if one wanted to tame it down a bit by rolling off the treble control.
Thanks for any suggestions.
Bill

[dogears]

First off, the mid control should be an audio. In my experience, a 250K linear is way too fast and touchy. The .01 midcap does make it harder to hear the mid control effect, buit it is still clearly evident. Since Fuchs uses a .047 on much of his line, the comparison to that amp can't be made.

The treble control is already a subtle control.

But, check your wiring none the less.

Nothing wrong with upping the birght cap on the master. Try 22pf first, then 33pf, and even 47pf. If you use the loop, then I would go at least 47pf.

[dobbhill]

How large is the tail resistor between the bass pot and ground? It can affect the tone control range.
D

[Wayne]

If your friend is used to a Lonestar, I can understand why he might say that another amp's tone controls aren't effective. The one thing I took away from my limited experience with a friend's Lonestar was that the EQ was very touchy. So much so that I don't think I could find the same sound twice. Small rotations of the pots made massive changes.

I haven't looked at the circuit to see what they're doing differently, but IMO it's too much of a good thing. It might be interesting to figure out what's different and use a similar stack in something of my own, but with less range of adjustment.

W

[bluesfendermanblues]

If your friend is used to a Lonestar, I can understand why he might say that another amp's tone controls aren't effective. The one thing I took away from my limited experience with a friend's Lonestar was that the EQ was very touchy. So much so that I don't think I could find the same sound twice. Small rotations of the pots made massive changes.

I haven't looked at the circuit to see what they're doing differently, but IMO it's too much of a good thing. It might be interesting to figure out what's different and use a similar stack in something of my own, but with less range of adjustment.

W

Really wierd that the tone controls should be that touchy - its just an ordinary fender blackface tone circuit....but, off course in comparison the skyliner has a lot more midrange. I alway think of the skyliner as three different flavours of midrange.

[marcos]

I absolutely agree with Dogears, the mid pot should be audio taper,both
250 K and 100 K values work well.The 10 nF mid cap limits the midrange dip,
so you can also try bigger values.I have had good success with 22 nF and
33 nF, the latter quite Fenderish (with a 150 K slope resistor), the former not quite as fat as the Skyliner.The larger the value, the brighter the overall sound, unless the mid control is full up.However, the treble pot
should be effective with all variations

[Structo]

I also have never felt that the TMB did much on my amp as well.
Seems like very subtle changes.
Although when I model it in the Tone Stack Calculator it looks like it should alter the tone quite a bit.

I do notice on the modeler that the controls don't seem to be able to add much above 50% but can take away quite a lot below 50%.

[JD0x0]

I also have never felt that the TMB did much on my amp as well.
Seems like very subtle changes.
Although when I model it in the Tone Stack Calculator it looks like it should alter the tone quite a bit.

I do notice on the modeler that the controls don't seem to be able to add much above 50% but can take away quite a lot below 50%.

The tone varries more when you have less midrange. Try scooping out all the mids you'll see the bass and treble have a much larger range than if the mids were all the way up.

Since the lonestar is a blackface tonestack it has a very scooped midrange making the other controls more effective. while ODS amps usually have higher mid pots.

If you lower the mids you can make the treble go from very thin and bright to super muddy and dark.


Edit: you shouldnt need very effective tone controls on a D-style amp. HAD tuned them for the users. the tone controls are just there to fine tune.

You also have the mid boost, brightswitch, and rock/jazz to tune the amp for different guitars. If that isnt enough control for you you're not using your fingers right.

[wjdunham]

Just got back from my 120 mile bicycle ride, a little more than I was planning (!) While I'm a bit cross-eyed, it's great to see all the info. waiting... I need to double check the taper on the mid pot, I'll change that to an audio taper. This amp has a built in loop. I tried a 33pf bright cap, definitely made a big difference, I hear a lot more of the string and pick artifacts. I'll try a few more larger values and see how I like them. While on the subject of the loop, I don't have the 220K/500pf network shown in the 124 schematic in front of the input to the CF, should I try that? What should I expect to hear?

My friend's comment on the tone controls was really more of a comparison to the lone star, not that he wasn't getting a tone that he liked out of mine. Makes sense if the lone star controls are really sensitive. I realize these amps were dialed for a particular guitar/player, but I think the concern was there wasn't enough range to set up the amp for a particular room, especially if the room was very bright. I haven't had that experience with it so far though.

I played with a few different mid caps early on, mostly switching between .01 and .02, to be honest I really can't hear much of a difference. I'll try again and see what effect it has on the tone controls.
Thanks again for all the suggestions. Once I recover and have some time to experiment I'll report back.
Bill

[Structo]

I noticed quite a difference when I switched over to the Skyline stack.
I left the 250KL on the panel but I didn't care for the .05uf mid cap and switched back to .01uf mid cap.

I think I have a 47pf on my master. That did help with the liveliness or presence of the amp. (not to be confused with the presence pot) of the amp.

As for the 220K/ 250pf network on the loop jacks.
Since I have the Ironsounds FX loop on my amp I initially installed a 100K resistor on end of the .02uf grid cap of the PI.
That really seemed to bring more Dumble out of my amp so I am going to experiment with larger values as well as bypassing it.