Converting TMB tone stack to High+Low in 5F6-A Circuit?

[ululufut]

I am fitting a Hoffman 5F6-A turret board into a 5E5-A chassis, which has no middle frequency control. I redesigned the attached Hoffman 5F6-A layout diagram to match the treble & bass knobs on a 5E5-A and am wondering if it looks like it did it right. Any thoughts?

Also, if I want to sacrifice the Presence knob to use as a PPIMV, can I just remove the wire between pin 3 of the Presence pot and the 27k resistor, select a substitute value for the 27k, and just take a parallel capacitor to ground, if I want to retain the presence effect at a fixed value, say at the equivalent to "5"?

[sluckey]

It's all messed up.

[ululufut]

That's what I was afraid of -> I was trying to incorporate this - attached

[ululufut]

I'm so depressed

[2deaf]

I'm so depressed

There's no "so depressed" in tube amp design.  Approach it like as though it is a challenge and you ain't backing down.

I was wondering where you got that tone stack.  It can easily be adapted to the 5F6-A turret board.  I have a couple of things to do and then I will draw you out a suggestion, if nobody else does in the meantime.

[ululufut]

Haha! - yeah I guess it's like crying in baseball. Thanks - I appreciate it!

[sluckey]

If the main objective is to just eliminate the mid control because the chassis you want to use is a 5E5A chassis that has no hole for a mid control, you could just simply replace the mid pot with a 6.8K resistor. Look at the AB763 circuit to see how to do this.

[2deaf]

Here is one suggestion.

[ululufut]

Sluckey - thanks; that's initially what I had in mind. I had the Hoffman AB763 single channel diagrams which foolishly mislead me regarding the fact the other AB763 channel has the High/Low eq.

2deaf - thanks very much for this! I think I'll try both of these and see what works best.

I really appreciate both of your insights!

[2deaf]

If you moved one wire and added two capacitors, I think your original layout would work.

[ululufut]

That's awesome! Thanks - I really, really appreciate it. I'll have to study this to make sure I know exactly how it works.

I finished a 5E3 on steroids for a friend few weeks ago and I just wasn't satisfied with it for what he said he was looking for; I figured that adding a LTP phase inverter might be part of the improved equation. Since I have an oversized tweed cabinet here, I realized I could squeeze a 5E5 chassis into it, and that the Hoffman 5F6A turret board would fit if I mounted the filter caps in a pan on the outside and was willing to ditch two of the four inputs. I at first had in mind - generally - what Sluckey was describing, but then I lost confidence in being able to get it right, and so I figured I'd try a color-by-numbers with Rob Robinette's version of the Bandaxall/James circuit, which I've been wanting to try anyway. It usually takes me two-to-three tries with incorporating anything besides component value swaps, however this time I'm trying to get the whole thing wired by next Friday, when I'm driving to St. Louis for an extended weekend of jamming/recording, so I was freaking out about getting it right the first time.

With this new amp I went with an Allen TP40 and TO40MT, which can now fit in the chassis; and with the hybrid Bassman-Pro/ Bandmaster hybrid circuit and some bells and whistles under the hood, it should be pretty nice. I picked up a Celestion Alnico Cream for it, so even if the amp sucks, it will look awesome from all angles.

Again, thanks so much - with this issue settled, I should easily be able to get it up and running by the weekend and jam out some early Pat Travers tunes just as nature intended.

[sluckey]

Maybe you can post some pics of this unique project.

[ululufut]

Will definitely do! I have to get it finished this week, so I should have it up and running at least by Wednesday - will post some pics and maybe a little video.

[ululufut]

While I indicated I'd be posting some images of this build this week, it turns out I needed to order a handful of extra parts, so it will be later next week after I return from a trip.

In the meantime, I'm working out bugs on the earlier chassis so I have a rig to take with me. I am having 60hz hum fits with it suddenly, however I have three days to work it out so it'll be fine.

FWIW I installed the Celestion Cream and, at least for the build I'm working on at the moment, I must say I prefer the tone with the ceramic driver I was using earlier. I may be selling the Cream if anyone is interested.

[davidwpack]

If it's a new Celestion you probably haven't got it broken in yet. They sound multitudes better after 50-100 hours. I've hated every new speaker I've ever bought for about 2 weeks.

[ululufut]

That's a good point - I bought it used, but it's virtually new. Nothing wrong with breaking it in and seeing how it sounds. Thanks!