Would this be too challenging ?

[Coastie99]

Hi guys.

I'm relatively new to the amp-building game, and definitely technically challenged.

Having said that, I'm meticulous and fussy, and have managed 5 builds, all of which I'm very happy with.

A friend has asked if I would attempt building for him a ( nominal ) 30W amp, switchable to a ( nominal ) 10W.

Naturally, I have questions, which I'd appreciate somebody answering for me.  Simply.   

Firstly, let us imagine that there is a Fender design that one might take as the basis.  Good for me, since there's likely a layout diagram available.

Would a switching function be a complex add-on ?

Is there a 6V6 Fender design that attains that ( nominal ) output ?

A 6L6 design ?

And, switching (!!) from Fender ........ is there an EL84-based amp out there that I might consider ?

Any advice would be hugely appreciated.

Thank you,

Gary.

[phsyconoodler]

"A friend has asked if I would attempt building for him a ( nominal ) 30W amp,"

  You can build any Fender or Marshall style amp and cathode bias it and add a low power switch.Three way power switch,lo,medium and high.
  and if you dig a little you can use variable voltage regulation and make it from 0 to whatever wattage you want.

 Fender Tweed Deluxe
 Fender Deluxe Reverb
 Fender Princeton Reverb
 Fender Tweed low powered twin
 Fender Super Reverb
 Marshall 18 watt
 Vox AC 30
 Vox AC 15
etc,etc,etc,..........
 

[HotBluePlates]

Does the low power setting need to be exactly like the high power version, but only less power? Or can you also have more distortion, more compression, etc?

In other words, the method of getting to less power may have artifacts. Knowing whether those are allowable could rule in/out a number of approaches.

[m3moser]

Not sure you can get 30 watts from a pair of 6V6 or EL84 tubes.  A pair of 6L6 tubes would easily get you to 30 watts, so if that's a requirement then start with those designs.

[Coastie99]

Wow, that was quick !

m3 ..... me either.  I did imagine a quad, but then I guess, we'd have too much oomph !!  Trouble is, my friend's not entirely clear what he wants.  He can

"hear" it, and the way he describes it, it's an EL84 sound,  But, he loves the dual 6V6 sound of my Silvertone ..... an entirely different animal.

psych .....  that's nice clear initial info.  Thank you.

hbp .....  not clear there.

Guys, thank you.  Just what I wanted initially.  I'll consult the friend and return in a while.

Gary.

[Coastie99]

Great, I have some further info from my friend.

He wants a two channel amp.

He wants 30-ish watts, switchable to 15-ish watts.

He wants EL84's.

Doesn't need tremelo / reverb.  Top boost OK.

Is this one of the Vox AC-30 variants ?   Where do I find a schemo / layout, please ?

[sluckey]

I bet he'd like this...

http://www.ceriatone.com/images/layoutPic/marshallLayout/36WNewCeriatone.jpg

[Coastie99]

So would I !!

Thank you most kindly.

[Coastie99]

BUT !

Isn't there always ?

We need a dual-channel design.

[FYL]

Well, the 36 is a two channel design. Add some glue if you want to add channel switching or use an ABY pedal.

[sluckey]

It is dual channel. It meets all your friends specs. Even better, Ceriatone is in your neck of the woods. Just buy kit, stir in a little solder, serve hot.

[Coastie99]

OK.  Please pardon my neophyte ignorance.

A further request from friend ......... could an output be built into this to allow foot-switching between channels ?

[phsyconoodler]

An ABY pedal is an external footswitch that will do that and no extra wiring needed.However,a relay and footswitch jack can be added but it's not paint-by-number to do that,it takes some skill.The ABY box is trouble-free and cheap.

[G._Hoffman]

OK.  Please pardon my neophyte ignorance.

A further request from friend ......... could an output be built into this to allow foot-switching between channels ?

There are a bunch of channel switching options HERE, but adding a relay or some similar channel switching is pretty easy.  I'm told the folks at Cieratone are very good about answering questions, and they could almost certainly help you figure something out as well.

Still, an AB or ABY box would be easier.


Gabriel

[Coastie99]

Thanks so much guys ....... we're back on track !

I'll follow up.

[Coastie99]

I haven't investigated the footswitch biz. yet, but otherwise we're moving along quite swimmingly.

I've no intention of buying this kit BTW, but building a replica from the layout.

Obviously, I'll need power and output transformers. My Fender-based 6V6's builds have been simple in this respect, but as a ( still ) novice builder, I'm at a pretty-near complete loss regarding trannie specs.

So, kind advisers, what do I need please ?  I am aware that I can spend a moderate amount on trannies, or a lot.  And, I know where to look for them.

[FYL]

Obviously, I'll need power and output transformers. My Fender-based 6V6's builds have been simple in this respect, but as a ( still ) novice builder, I'm at a pretty-near complete loss regarding trannie specs.

So, kind advisers, what do I need please ?  I am aware that I can spend a moderate amount on trannies, or a lot.  And, I know where to look for them.

If you go for a 36, you need to juice 4 x EL84 @ 800 mA ea. plus 3 x 12AX7 @ 300 mA => 4.1 A

PT : 290 - 0 - 290 V @ 200 mA or more, 6.3 V @ 4.0 A, 5 V @ 2 or 3 A depending on the recto you want to use.
OT : primary app. 4 K, secondaries depending on the speakers you intend to use.

[Coastie99]

Thank you FYL.

Concise and to the point.  Or ......... easy for a dummy to understand !

[Coastie99]

Almost have the green light from friend.  Here's the clincher ...........

Dirty !  Gotta have dirty !!

Will this do dirty real good ?

Found our OT ............. http://www.torresengineering.com/ham50watoutt.html

[FYL]

Dirty !  Gotta have dirty !!
Will this do dirty real good ?

Depends on what you mean by dirty. A 36 will go up to nice hard disto, but not up to überdisto modern metal-style.

Found our OT .............

Not the best option IMO. Try a 1750V if you want to stay with Hammond. Doug's 018343 would work very nicely.

[RicharD]

>He wants a two channel amp.

He wants 30-ish watts, switchable to 15-ish watts.

He wants EL84's.

Doesn't need tremelo / reverb.  Top boost OK.

Dirty !  Gotta have dirty !!

You just described the Matchless DC30.  Absolutely a great amp.
http://www.el34world.com/charts/Schematics/files/matchless/matchless_dc30_old.pdf

Ceriatone makes a kit.
http://www.ceriatone.com/productSubPages/Muchle$$DC30/Muchle$$DC30.htm

[Coastie99]

Dirty !  Gotta have dirty !!
Will this do dirty real good ?

Depends on what you mean by dirty. A 36 will go up to nice hard disto, but not up to überdisto modern metal-style.

Found our OT .............

Not the best option IMO. Try a 1750V if you want to stay with Hammond. Doug's 018343 would work very nicely.

We're old geezers FYL ........ metal ain't spoken here.  

Thanks for the OT advise.  There's no burning desire for a Hammond OT ....... I'd rather buy from Doug.


{EDIT-- untangled quotes -- PRR}

[Coastie99]

Well, things have moved right along, and I have some components on the way from Doug to begin building a Ceriatone 36W.

http://www.ceriatone.com/images/layoutPic/marshallLayout/36WNewCeriatone.jpg

Mostly clear to me, but for a question regarding the rectifier. I'm "seeing" a diode connecting P7 (NC) and P6 (the plate) and the same at P5 and P4.  Surely not !!

[FYL]

The diodes are in series between the HV winding and the GZ34, with a shunting HV cap. The diodes protect the valve, the GZ34 still brings some sag/compression. You may omit them if you wish, with suitable rewiring of course - HV straight to plates at pins 4 and 6.

[Coastie99]

So, I was right.  Good heavens !!

Thanks FYL.  Is there a compelling reason for their removal ?

[FYL]

They aren't required in a 36 but offer a degree of protection. Silicon is cheap, PT's and valves are expensive.

[Coastie99]

Not too hard to see the logic in that !

Do you consider this "good practice" in a 5Y3 - rectified amp. ?

[FYL]

Ditto: the diodes aren't required but add some protection.

Here's what Ceriatone does in their 5E3 clone:

[Coastie99]

Thanks FYL.

I'm mighty obliged to you.

Gary.

[Coastie99]

Bit embarrassed to be asking this question, but here goes.

I can see that I need two SPST switches for power on / off and standby.

But, what do I need for the half-power switch ?  I'm in uncharted waters here.   There will be no 16 ohm facility on this amp., so no feedback switch.  OK ?

[sluckey]

DPDT

[Coastie99]

On - off - on ?

On - none - on ?

[sluckey]

Just a standard ON/ON DPDT

[FYL]

I can see that I need two SPST switches for power on / off and standby.

I'd use a DPST for on/off in order to switch live and neutral. Just a precaution.

But, what do I need for the half-power switch ?

Looks like a standard DPDT. Two switchable inputs, one output x2.

There will be no 16 ohm facility on this amp., so no feedback switch.  OK ?

Nope, the feedback switch allows you to choose between two levels of NFB, giving a looser or tighter sound depending on it's position. It uses the 16-ohm tap, that's all. If the OT you're going to use has no 16-ohm tap ou'll have to scale component values accordingly: using the 8-ohm tap will reduce NFB levels if you don't.

[Coastie99]

OK.

DPST for power on / off

SPST for standby

DPDT for 1/2 power. 2 position. On - none - on.

I believe that I will retain the 16 ohm facility to keep things easy !!

Many thanks, yet again.

[Coastie99]

Doggone !

Since I'm retaining the 16 ohm outlet, what switch do we have there please ?

[sluckey]

same as all others