Single channel ac15 build with quest for power

[Jenkumfactory]

Hello! Long time lurker but first time poster here. Firstly i have to say I'm very impressed with the amount of knowleadge and educational will residing here!

As the title implies, I've been planning to execute a build of an AC15 style amp but with only the ef86 'normal' channel. It's really a pretty close 'clone' of the ceriatone creme brulee (in turn a 15w clone of matchless c30 ch2) I have in mind. But i would like to do it 'on my own terms' so to speak. Custom casing in an old radio, sparing no expense and so forth. And I cant find any exact breakdown of that cercuit...

Where I feel at a loss right now is regarding power supply and surrounding calculations. The main, and wide, question is what the removal of the TB channel will imply. And if/how one could use a 'standard' AC15 PT in the design?
That would certainly help a lot when scouring for transformers..

My quick logical breakdown would say that the inactive channel in a standard AC amp wont pass any voltage or current, and thus removing it completely shouldn't really have any non-neglectable impact on anything.
But I'm not very wise in this topic yet, especially in regards to analysing current.

Any help or interest in the project is ofc. appreciated!
Has anyone here got experience with a similar design? Or tips on comparable amplifiers I can look into?

Cheers

[sluckey]

This may be of interest to you. If you don't want the Marshall channel then simply ground the lower PI input cap.

     http://sluckeyamps.com/dual_lite/dual_lite.htm

[Jenkumfactory]

This may be of interest to you. If you don't want the Marshall channel then simply ground the lower PI input cap.

Sweet! That material will definitely help with setting up the layout and wiring! And grounding the input cap to/from the second channel was exactly what i wanted to hear. I take it i was correct in assuming that no modifications will be needed in the power supply.

That design is indeed very close to what I'm scetching on. And here comes the amp rant!
The additions i'm planning are:
*High/Low input impedance toggle.
*Tone control bypass pot.
*Potentially a Bass control too! Got this idea from a fairly obscure amp called Dirty Teen by Faustone. Can't quite get my head around it yet but it would be nice to be able to really clean up low end into the PI and use the tone control more for tone shaping..
Side note, I much prefer the chime-inducing post PI cut to, for example, the Faustone treble control. And I'm fascinated by the old fender deluxe that used a post power amp cut! I think that could increase the chime factor even further. A very scary thing to put your hands in however.... that cap will blow your, and your neighbours, heads clean of
*Master vol
*Potentially a power regulator a'la London or something like it. That will be a future obstacle to tackle.. i have some ideas for a foot-switchable "solo boost".
*Probably a choke (since i plan to use this for touring and will need all the help i can get in reducing hum from weird power grids. I hope I'm not making an ass of myself in thinking that would help.)

And all of it boxed in an antique radio enclosure!

Aim for the stars and break your legs falling is the motto here.
Will definitively return for more questions and will post updates when if ever I get this thing going!
Wish me luck!

[sluckey]

Sounds like you don't know what you want. But it's gonna be housed in an old radio cabinet and it will be used for touring? You need a reality check!   

[Jenkumfactory]

Sounds like you don't know what you want. But it's gonna be housed in an old radio cabinet and it will be used for touring? You need a reality check!   

Haha that might be true. But hell if I'm not going to go for it. I've been gigging with vintage amps and guitars for at least 10 years and i have not one single time had a piece break down on me on the road. So i think it's about time i start pushing my luck, no need to agree with me.

But i have to say i disagree with not knowing what i want. I want to build a sexy old dank rank mind blower machine. Not to much to ask for! And there are good reasons to have 4 differently positioned level controls, i promise :D one before and after every gain stage. Of course I'm going to build it in a proper chassis first. I dont se how a hollowed out radio would be that much different from any old plywood amp enclosure.  But please educate me.

And thanks for making me want to prove you wrong ;)

[tubenit]

Please post an exact schematic and layout of the amp you would like to build.

With respect, Tubenit

[MORE_Guitar_Solos]

Personally with touring gear, I've found the fewer knobs the better, ymmv.

[Jenkumfactory]

Please post an exact schematic and layout of the amp you would like to build.

With respect, Tubenit

I was planning in it as soon as I have it more or less ready. Tried to design it in LTspice but couldn't find any accurate ways of modelling the EF86 or OT+load so i haven't been able to confirm component values. But since I've started this thread now i can produce a alpha sketch so people can shred it :)

[sluckey]

In your first post you said "I've been planning to execute a build of an AC15 style amp but with only the ef86 'normal' channel." But
your description in your lengthy post was not even close to a single channel AC15. That's why I said what I did.

[Jenkumfactory]

In your first post you said "I've been planning to execute a build of an AC15 style amp but with only the ef86 'normal' channel." But
your description in your lengthy post was not even close to a single channel AC15. That's why I said what I did.

Ok! I was thinking there was i high probability i didn't really catch what you were going for there.
Let's call it a derivative of the AC15 normal channel then :) And I'm ofc not going to include all those features i listed all at once. That's more of a list of possibilities I've considered. In reality it's probably going to end up looking very close to the ceriatone creme brulee, but with an added potentiometer to adjust the amount of signal passing through the 'tone circuit'.

The one other thing i really want to include however, is some sort of power control so i can retain a nice power-tube compression at rhythm level and still be able to kick up the volume for leads without smashing the sound (and hardware).

I'll get working on a sketch now!

For the interested or bored i will go on with my speculations:
 I have designed a motorised knob turner device (inspired by Neil Young) that in effect is servo motor you attach to a potentiometer and control via a footswitch. So the morgan or london power voltage reduction designs could really lend themselves nicely to this purpose. The workings of these are completely unknown to me however..
I dont know if there might be a better and more integrated solution out there and all tips are welcome! I've looked into attenuators but not even the uber expensive ones seem to do it right really.
A pentode/triode switch seems popular but i find the effect too extreme..
A really basic idea I once balled around was to have a variable resistor "between the push and pull sides", post power tubes. Working sort of like the cut control but for the full frequency spectrum. I wonder what artifacts that would leave in the sound and have no idea if a varesistor of that calibre even exists in any practical way.. I've only just finished my first year of engineering studies and my only knowleadge of amps comes from playing and reading so my reasoning and ideas are simple.
It really feels like the master volume, to me, is an inherent issue in guitar amps that no one has been able to solve once and for all. I would love to be wrong in this.

[Jenkumfactory]

I feel compelled to update this. In my quest for transformers i found a person selling a 1x12 DC30 clone with west labs iron, TAD tubes, and a blue dog speaker, built by a renowned Swedish builder. For 850€ it was about what i was expecting to pay for this build so i couldn't decline😄 And now i can delay getting a proper oscilloscope too 😅
Will probably start this, or a similar project, up again during a future break in my studies but will keep to building pedals in the meantime. Thanks for the support!

Oh and I finally stumbled upon this piece of kit called 'tone king iron man II mini' which is exactly what I've been looking for with footswitchanble attenuation, can't believe it hadn't shown up before in my search..

I'll stick around in the shadows.
Cheers!