Building a mini Super Lead with 4 x EF80

[Yoda]

Hello everybody,

I’m in the early planning stages of building a mini Marshall 1959SLP clone for myself.

I recently built a 20-watt JCM 800 clone with octal preamp tubes and it was way too loud and had too much gain for me. So now I want to try a Marshall Super Lead utilizing 4 x EF80 power tubes.

I’m thinking of using Rob Robinette’s Bassman Micro power amp as a template, simply doubling it. The Hammond 125B he recommends for 2 x EF80s is setup for 22.5k impedance, but if I use 4 x EF80s I can rewire this for 11.6k instead. There’s also the slightly larger 125C if that’s a better OT (8 watts vs 5 watts for the 125B). Any reason this shouldn’t work?

Also, on the EZ81 rectifier would a single one be sufficient for this or would dual EZ81s be better (like the early dual rectifier Bassmans)?

Thanks in advance for any help.

[Stevem]

Four EF80s can consume 60 ma, that EZ81 can output anywhere from 100 to 160 ma depending on the input voltage to it.

In short even with running 4 output tubes and a few preamp tubes the EZ81 will work.

Going for 8 to 10 watts of output from a 5 watt OT is not good!

[joeboo88]

Here is a great example, which I built from the schematic provided by Randalp3000
I love the amp and play it all the time. He or me didn’t use ef80 we used 6aq5 s which are like a 6v6 but with 7 pins

https://ampgarage.com/forum/viewtopic.php?t=29456

[Yoda]

Cool, 1 x EZ81 it is then.

I recently became familiar with the 6AQ5 tube from working on a couple small Epiphone and Gibson combos. I thought it was a very good sounding tube and I’m definitely interested in building something with these in the future but for this project they have more power than I want.

This one is going to be a mini Plexi I can wind up all the way at home including the power section for some EVH tones. I mean even a crappy Marshall JMP model on my Vox Valvetronix amp with a boost in front gets me closer to the EVH sound than anything else I have in my stable of amps so it’s time to just build my own version of the famous Marshall 4-holer. I thought the JCM 800 would be ‘it’ for me but I think it just wasn’t what I was looking for. I was naive to think boosting the low input on a JCM 800 would get me into Plexi tones.

[Phil_S]

The 6AQ5 is identical to 6V6, just a smaller bottle and 7-pin base. If 20W was too loud, I don't think a pair of 6AQ5 will give the result you seek.

See if you can find a pair of EL95. I got mine on eBay for very little money. I think they'd be a good candidate to mate to a Marshall pre-amp circuit.

Many years ago, I had a PT and OT that were low power. I finally settled on a pair of these as a viable path and built an amp. I recall that I liked the result, but haven't fired it up in years. I'm attaching schematic and voltage chart. The amp was based on a 5F2a and that's not what you say you want. The documentation will show you the power supply and that may be worth something to you. It's my recollection that the OT was ~9K, which I derived from a low voltage test of the turns ratio.

Good luck!

[Phil_S]

For some reason, the voltage chart didn't post.

[Yoda]

I have a bunch of NOS EF80s on hand and I’ve built several of single-ended EF80 amps based off Rob Robinette’s design with great results.

Like 6AQ5s, the EF80s are still very affordable for NOS tubes.

I don’t know what it is about the Marshall 2204 circuit but when I built mine with 6V6s it was as loud as a 50 watt amp. No amp with 2 x 6V6 should be that loud!