new amp project

[paradox]

It appears I have a chassis from ebay on the way (a vibro champ chassis from risson's shed), and its time to start figuring out what
to do with it. I had one crazy idea - to use the front end of the 18watt design (just one channel) and then put that into
the power amp of a single ended 6v6 (like the champ) The chassis has cut-outs for six pots but I can always go with a
custom front panel and use just the number I need. I guess I could go full 18watt, but I rather keep the watts real low
and go single ended - I guess I could do single ended EL84, but I haven't seen that in many designs. I was also thinking of
working a master volume (gasp!) into the design - just looking for inputs from the amp builders here.. I know its weird - marshall
in a fender package, but its just the direction I want to go - low watt - marshall like - 10" speaker - tube 10 i guess - any ideas???

 

[marty1776]

You can go to 18watt.com and check out the downloads page to see some projects. All these are ~18W output but some good ideas for you, like a minimalist, single channel 18w. Also check out AX84.com and the projects there. Some good ideas can come from both and the forum at AX84 is very helpful.

 

[CharlieB]

I like to think in terms of hardware....

You've got two small tube socket holes, to big ones, another hole where the cap is that can be used for a tube (if you carefully place components inside), and five control holes up front.... two input jacks, a pilot lite hole, and an on/off switch hole.

Now go fill 'em with stuff!

 

[TNT]

The 5E3 Forum also has some nice project schematics that you can check out also.

 

[paradox]

ya right cb, there's only 5 pot locations - I was thinking six... I have seen some adapters to go from octal sized holes to 9 pin sockets also!

 

[Spunky]

WTF....

There is a 5E3 forum....Gadxooks Man I must be sleeping.. .Thanks TNT! ;D

 

[TNT]

It's a doozy too Spunky. Everything about amps (especially Fender) but the heat sink!

 

[marty1776]

The heat sink! HA!

 

[Kepa]

The layout for 5E3 amp you can find from http://www.hoffmanamps.com/images/5e3.gif
It's easy to mod a little bit and use blackface preamp circuit...
If you gonna built a single channel version you have one preamp tube half to use either for simple tremolo or extra gain stage... :)

 

[CharlieB]

I found a lot of the charm of the 5E3 was the interactive volume controls, and their effect on tone... aw man, don't single channel one!

I DID go for an adjustable grid bias rather than cathode bias... mostly because modern transformers run the 6V6s harder, and you really cant quite put them into Class-A PP on a Deluxe Reverb PT's rating. Ya gotta lower the voltage to do that.

 

[paradox]

well here it is so far - I've come up with a wiring diagram, made the board and made a brass plate for it - I had plenty of brass sheet left over from the last project so I thought I'd use one for the grounds.  The front end is all from the 18watt design, but I'm going single ended.
Here's the plan:

Gain stage->vol->gain stage->cathode follower->TMB tone stack->gain stage->MV->Single ended EL84

It might be one gain stage too many, but I made room for a divider on the board or I can just take it out, but I can't deal with the idea of having an
unused triode in there!!

I'm going to try an adapter plate from weber to mount the EL84 socket in the 6V6 sized hole.  I'm also leaning towards using a Hammond transformer for
the EL84, this is really because I can't find another one that is a 4K/8ohm single ended tpe. Once its together I going to mount the chassis in a champ cab
I already have with a 8" celestion spkr.  (That is if it works worth a damn, since I was trying to come up with a sort of unique design, we will just have to see, this is
half the fun!!!).  Was also thinking about using a SS rectifier, but I'm back on the 5y3 plan for now.  I may need to use the zener trick cb showed us to pull down the B+ for the EL84, and I still need to figure out what size cathode resistor, looking at the new gibson GA5 amps, they use a B+ of 312v with a 270ohm cathode resistor, so I may start out somewhere in that balpark.
Not much more gonna happen for a while til I get some parts on order.

 

[JmOS]

[quote author=paradox link=topic=4982.msg64917#msg64917 date=1131165524]
... - low watt - marshall like - 10" speaker - tube 10 i guess - any ideas???
[/quote]

I love tube 10 in my little Laney but I'm also sure Vintage 10 is better.

I never heard it, but Tube 10 is a cheap line in Celestion speakers like GT's.
I would also consider Jensen Q 10.

 

[gotdabluz]

http://www.tonetubby.com/speaker.htm

these are not cheap, but they are among the best sounding speakers I have ever heard

 

[marty1776]

do you have a PT yet? I'm starting to imagine starting to think about a 5E3, can't go too fast or wife will kill me. I guess you're not interested in putting in another hole for an EL84 valve?

 

[CharlieB]

works for me... that is the classic layout for say.. a bassman

 

[marty1776]

Anybody have a set of Greenlee punches? I've looked at them but do fine with my dremel, it takes a while but saves some serious bread$$$$$$.

 

[gotdabluz]

[quote author=marty1776 link=topic=4982.msg66509#msg66509 date=1132253125]
Anybody have a set of Greenlee punches?  I've looked at them but do fine with my dremel, it takes a while but saves some serious bread$$$$$$.
[/quote]

yeah . . . but you could always use 'em on you next project . . . c'mon you know you can't build just one!
. . . did you try flea-bay?

 

[paradox]

marty - if I went with the SS recto I could put in two el84's, but then I'm getting into a louder amp - this one is for the lower volume situation(s) - that's why I'm thinking of going back to the 8" spkr as well - (besides I have an 8" celestion already!!) I've got a few good loud amps, but the champs, 6 or 8 watts and small skr, can be used without disruption in the house!! The champ I have now gets the most play in the house, but it seems I can get by with just one!!!

I have a PT from a Princeton that I may use, but I also have one thats meant for a bridge rectifier - I'm still deciding between tube/ss rect..

cb, bassman?? wonder how this will work for the 8" - only one way to find out!! also - I've been using the phenolic tube sockets on projects, but I'm taking a tip from your work and trying the ceramic ones this time, the ones I've gotten before (phenolic), have just seemed, well cheap!!

 

[marty1776]

I use all ceramics. I get them from Hoffman I think. Cheap, with mounting brackets and shields, wire retainers are extra but just a few quarters.

 

[CharlieB]

www.tubesandmore.com for good sockets

The Bassman circuit was better for guitar than bass. It basically used the same order of layout as you're suggesting, which ought to be a killer amp.