Choke for a 40-50 watt Fender type build

[pjd3]

Hi,
For a single channel VibroVerb I'm in the process of building, the schematic calls out for a classic tone 40-18003 4H, 90mA choke (125C1A).

Allen amps has a choke that is also stated as replacement for 125C1A but is 3H, 100 ohms. Allen states this choke as good for all of Fenders higher watt 6L6GC types amp (Bassman, Vibroverb, Twin, Super etc..) So I have to imagine that although the specs are somewhat different they are meant to do what they are supposed to do in those design of amps. My amp I'm building is a single channel Vibroverb but, wanted to check in to make sure it will do.

Since I'm getting the Allen Output transformer TO35MT I thought I would order their 3H 100ohm choke while I'm there, as long as it is an approptiate choke for this build.

Thanks!

Phil

[chief mushroom cloud]

DCR for the Classic Tone is stated to be 105ohms, per there datasheet, you say the Allen is 100ohms. That's within 5%. Is your Vibroverb for a MIL/Aerospace client?

[pjd3]

Thanks for stopping by chief muchroom cloud.

I was 95% sure they would be interplaceable with each other, and it was more the curiosity of inductance - one is 3H other is 4H. I haven't had much practical experience with inductance in a circuit as I have with resistance and capacitance so unfortunately, I don't hold much confidence in my "Henry's intuition", I'm in no place to make any assumptions so, safer to ask!

Thank you,

Phil

[chief mushroom cloud]

yea, I've played the choke swapping game too many times.....I've found that it takes much more than a couple Henrys to hear or feel any difference, especially when they are WAY overrated for their position in typical Fender circuits. All the amps I have are now all HT-C-L-C-Plate config (much like Gibson Atlas or Vox AC15), so it's a different ball game.
In fact, I am in the middle of a 35W Fender-ish build myself. But using Gibson Atlas PI and power amp stage...and power supply. Using Marshall 5H choke from Classictone....So it's a Fenson....er...a Gibner.
Having a custom 5k OT made using 5E7 OT platform.

[pjd3]

Hey I appreciate hearing the comment, from someone whos tried and experienced it.

Good luck on that amp build, sounds like you have a little "sonic vision" on something there. For my first buildl trying to keep it fairly simple and hoping to get more creative over the years. Did that with pedals.

I'm trying to build a 35-40 watt amp, very clean and lotsa headroom, good for pedals. I build and use alot of those "Tube-to-FET" conversion pedals from Runoffgroove and they seem to like a very clean channel to work well. Otherwise, they can get harsh quickly. Being in local classic rock bands of 4 decades forces me to need lots of different amp type responces. Plus, I'm planning on a nice reverb pedal at the end of the chain, definately gonna need clean for that.

thanks!
Phil

[aguynamedben]

Hey Phil I’m doing the same thing as you, for my first build ever.

Rob Robinette Blackvibe. No reverb or tremolo, but 35W 6L6. I’m also looking at using the Allen transformers.

Question: what are the chances I can get this into a blackface Princeton chassis? I think I will have to order a custom chassis to be made, but that seems do-able. I think I’ll also need to use a 1x12 tall Princeton combo cabinet like this one: https://www.facebook.com/matherampcabin ... 26/?type=3

Am I crazy? Did you just use a AB763 Pro chassis like Rob recommends?

I need to size/space it all out myself, but wanted to get an early sense if this was just a crazy idea.

-Ben

[M Fowler]

For most of my Fender 6l6GC amps I use Mojo777 choke

3.5H
100mA
100R

Mark

[Stevem]

Where the choke is placed power supply wise. ( before the first filter node or before the screen node) in a amp with a Pentode or Tetrode tubed output stage has far more of a effect then even 5 Henry change in spec once the amp gets played loud enough to start to drag down the power supply a good amount!

[pjd3]

Hi Agun

A Princeton reverb chassis will be fine as long as you have a method to enlarge the openings for the transformers. I used a Bassman power transformer from Mojotone and the bell on that is considerably bigger than the one on a Princeton power transformer. I enlarged my PT hole with dremel and hacksaw. It was a little "hacky" but, I made it fit. If you have room under the chassis you could find some creative way to mount a bigger transformer higher off the chassis if you don't mind the transformer bell not protruding too much into the chassis hole. I wanted my power transformer to protrude into the chassis, just a personal thing so I went through the trouble of enlarging the hole.

I believe I used a Classictone output transformer, one that is generally used for say, a Pro reverb - 40-50 watts - 4K primary

I did the 6L6 blackvibe as well and I use it frequently to gig. Its performing well for me. I wanted a nice big clean pedal platform for moderate volumes and thats exactly what I got. I did however add a "mid-raw" for thickening the sound when I used certain pedals. This is a great feature that can really fill out the sound of say, a Marshally pedal or Voxish pedal. I don't want too much of a Fender scoop when using pedals like that. I believe I just added in a 25K linear pot to the standard mid resistor that is there.

My biggest concern was noise due to the smaller chassis and therefore more densely populated components. The amp is quiet as can be. And as you can imagine, I was encouraged to be very prudent about the ground scheme - stick to classic grounding - power things to power ground and preamp things to preamp ground (the input jack).

Have fun! I did and it was a great project!
Phil PJD3