EL844 Amp Based on 5f6a?

[tubeswell]

2 x EL84s or 2 x 6V6s in push-pull will both run okay on anything from 5k to 10k with anything between 6k6 and 8k5 being 'optimal'.

A 5E3 tweed deluxe is a great little amp. You build one of those and between that and the 5F6A, it'll most likely be all the amps you'd need (until you need to build a tweed super, a tweed pro, a tweed bandmaster and a tweed tremolux or two, and then start on the browns and the blackfaces that is)

[The New Steve H]

I'm going to stick with the 5f6a concept. One of the things I love about it is the nice volume control, and it's my understanding that you can kiss that goodbye with a 5E3.

[The New Steve H]

I can see I don't understand the relationship between output transformers and power transformers. Something new to study.

I see Mercury Magnetics makes a Bassman OT (FO50BM-4/8) with an 8K impedance for EL84s, but they charge a fortune. It would add a hundred bucks to the project. The Classictone I put in my existing clone sounds tremendous.

Is there any reason I can't use the Tweed Deluxe PT with this Mercury Magnetics OT? I guess it would be worth the extra cash to get exactly what I want, with 4 + 8-ohm capability.

[tubeswell]

If you want to run 2 x EL84s in PP a tweed deluxe PT will be fine provided the PT has enough heater juice. (760mA per EL84 and 300mA per 12A-7, plus a bit more for the lamp (if you want a 6V lamp of the heater winding). (And of course depending on the rectifier you want to go with). a 325-0-325 HT will run EL84s a bit on the high side, but if you include series limiting resistance between each side of the HT winding and the rectifier, you should be able to keep the EL84s to about the 320V ballpark

[The New Steve H]

I kind of like 125V neon lights. They go out of the way by the power stuff, so it's one more thing I can shove away from the tubes.

I guess it would have been intelligent of me to find out what kind of voltages EL84s and EL844s like.

Now I'm reading that you can stick JJ or Tung Sol 6v6 tubes in a plain old Bassman at 450 volts, to get an output of something like 20 watts. Geez...if that's true, maybe this project is pointless and I should do something else. It sounds like I might be spending $400 to get pretty much the same result I would get with a $29 tube swap.

[diagrammatiks]

ya you'd have to rebias the 6v6s but there are 6v6s that can take up to 450.

you'd have an impedance mismatch though on the ot so you'd have to go...I think with an 16ohm speaker where you would have used an 8ohm speaker.

that being said...what are you really trying to accomplish with this other project?

just a lower powered amp?

[The New Steve H]

Thought it would be fun to be able to crank the amp a little more in a small room, for practice.

I have to admit, though, as it is, the amp is fine for practice. It's kind of shocking how good it sounds at low volume. And I love the 12ay7.

I need a new project, regardless. Maybe I'll just go ahead and do it.

[azatplayer]

Having built a few 30 watt and 15-18 wattrs, i would say definitely go with a VVR on your 2xel84 amp, cos they aint a lot less volume than a 30 watter.
I built a kinda half powered Z wreck and its plenty loud, but the VVR tames it well.
That first post describes the Mz jr pretty well, fender circuit with 84's. Very loud amp.. i would err on the lower voltage side, the maz, my bros ac15cc and some others run 370V plates, making for LOUD!

[10thTx]

I realize you stated you wanted to keep a 12AY7 in V1. However, IF you were willing to reconsider wiring that for a 5879 pentode ......... you could build this amp which is VERY versatile and has both nice cleans and nice overdrive.

Geezer designed and built this. He is a great player and the amp has excellent tone!

I think this is the same amp preamp & LTPI etc..... but into 6AQ5 tubes instead of EL84's? Soundbit:

http://soundcloud.com/dageezer/snatch-i ... blues-demo

http://www.el34world.com/Forum/index.php?topic=10999.0

http://www.el34world.com/Forum/index.php?topic=6176.0

with respect, 10thtx

[martin manning]

Sounds great! That looks like an excellent option.

[The New Steve H]

I can tell you the one thing I've learned from this experience. I will probably never be able to make myself buy another factory amp. There are so many good options for homemade amps, and you can make so many improvements, it seems like it's stupid to give up and go to Guitar Center.

It's just like learning to brew beer or make pizza. I know I'm slumming whenever I buy a six-pack or a slice, no matter who made it.

[Zippy]

I took a look at Trainwreck Rocket documents. Doesn't look too much like a Bassman.

Really? A Rocket with an octal output section (6V6, 6L6, KT66, etc.) looks more similar to a tweed Bassman than different to me. Very similar topology - gain stages up front > cathode follower > tone stack > PI.

Call it however you like: Go with a Rocket and 6V6s or a Bassman with 6V6s - a couple tweaks will make them the same (assuming the same iron).

[The New Steve H]

I know so little about amps, if the circuit isn't facially similar to a Bassman, I won't be able to see the similarities. I can tell the Mini-Bassman is related, but with the Rocket, it's not obvious.

I am still a little unsure as to which amp I should build next, but it just occurred to me that maybe I should build an effect instead. A HERZOG! I have the schematic already. It's a Champ rigged up so you can plug it into another amp.

I know you can buy a pedal that does the same thing, but dang, who do I know who has a REAL Herzog? NOBODY! This would be a ton of fun, and the effect is very cool.

[The New Steve H]

I have given up waiting for my guitarist buddies to get it together RE new amps, so I want to resume this project. I am putting together a BOM.

Here's what I want to do: Little-Wing-type amp, but EL84 outputs instead of 6BM8. Tubeswell helpfully pointed out that I would need a lot of heater current. It adds up to about 2.1 amps. I found a Fender-style PT that has 5V for the rectifier, with 660V on the primary. It's a big transformer for this project, but I don't know of any reason why that would cause a problem.

Specs: http://www.classictone.net/40-18066.pdf

Here is the matching OT: http://www.classictone.net/40-18038.pdf

The schematic has a choke on the power supply, but all it says is "choke," so I don't know what to use. I don't know how to match chokes to power supplies.

Classictone matches the transformers with this choke: http://www.classictone.net/40-18040.pdf

The specs say 4H, 50 mA, which is confusing to me. I must misunderstand the current spec, because surely you can't run an amp on 50 mA.

Anyway, help would be appreciated. I'm off to figure out what other changes different tubes will require.

Original schematic jpg uploaded to save time.

[10thTx]

I found a Fender-style PT that has 5V for the rectifier, with 660V on the primary

If that is 330-0-330 PT then you are going to likely have a problem.

I don't think you want the EL84's at 363 volts which is what you'd get with a 5Y3 (approximately).

That will definitely exceed the EL84 plate limit.

Most 18watt type trannies will have something closer to 250-0250 thru
300-0-300 range PT.

With respect, 10thtx