1U Preamp Projects

[Mattallica]

I have a few preamp ideas that I would like to develop and eventually build. I am hoping you guys will help me realize these.
Basic premise is that they be similar to MTS format. That is, two channels/voicings in a 1U space. Complete with separate controls for each.
Generally the first channel will have lower gain structure than the second channel, so there is a standard clean/dirty selection.
I'd like for them to be used as stand alone preamps or be incorporated into a rack system. I think having a switchable fx loop which can do double duty as a boost is useful feature.

Note that although the schematics show the Antek transformer, I plan to use the TubeTown Engl E520 toroidal replacement as it is a more comfortable fit.
I've left it in because I think the standby/tap switch (ala Music Man) is neat.

I started with an EF86 design, so the schematics going forward will be based off of this schematic.
I had a leftover triode, so I thought I would use that for the fx loop recovery. I may need to pinch this back depending on the design.
I've had a bash at the fx loop and output stages. I couldn't find anything definitive as far as schematics go.

I will be appreciative of any feedback and help on the schematics. I'm a rookie and don't have full confidence in what is drawn. I have just cut and pasted to the best of my ability.
I would like to save myself from as much frustration and tears as possible etc.

[Mattallica]

Here is the EF86 design.

First channel is Matchless style.
Second channel is Blackstar style with the example Merlin small signal pentode values.

I am uncertain about the pots for the mid control.
I've seen different values used in these positions for bridged T circuits, so I thought i'd make them variable.
I am unsure if the "sweep" actually sweeps, same for the "notch". I'm not sure if these are the best descriptors.
Should I shunt the mid control down the line, after the cathode follower?

[Mattallica]

Here is a Vox inspired design.

First channel is normal/boosted (ala Brian May)/V15 style.
Second channel is topboost/Naylor, Naked (ala Billy Howerdel).