Need advice on building an amp with tons of clean headroom

[xtian]

Wow, TB, thank you! And I curse you for not posting this a few days ago, before I worked out a similar layout for the simplified Brownface!

[Zero4]

This is something of an aside, and nothing against any of the afore mentioned circuits. IMHO, Some circuits do produce nice clean tones very well, but some don't feel that great to play and they don't produce familiar tones that many seek( without directly saying so. ) Sometimes these qualities are overlooked.

The classic Fender blackface AB763 circuit is a natural for anyone seeking a classic clean tone that sounds familiar, feels great to play and takes pedals well.

A no reverb, no tremolo, single channel AB763 is an easy build and a great choice for high headroom work. On my personal amps, I also prefer to keep the voltages high, like that of a super reverb on the preamp and power amp.

On the attached layout/schematic, SLukey's AB763 lite is a great choice for this circuit. With good planning and parts selection it's also easy to package all this in a very small chassis.

That's definitely an option we were looking at. (actually the likely scenario)

That schematic does not specify tube types. I'm guessing it's assumed I would know what they are supposed to be... Let me give it a shot - 12ax7, 12at7, 6l6?

[martin manning]

That schematic does not specify tube types. I'm guessing it's assumed I would know what they are supposed to be... Let me give it a shot - 12ax7, 12at7, 6l6?

...but scroll down- the layout does.

[Phil_S]

This is something of an aside, and nothing against any of the afore mentioned circuits. IMHO, Some circuits do produce nice clean tones very well, but some don't feel that great to play and they don't produce familiar tones that many seek( without directly saying so. ) Sometimes these qualities are overlooked.

The classic Fender blackface AB763 circuit is a natural for anyone seeking a classic clean tone that sounds familiar, feels great to play and takes pedals well.

A no reverb, no tremolo, single channel AB763 is an easy build and a great choice for high headroom work....

Agreed, there is a tendency to overlook the familiar and obvious. There are many good reasons to build a tested design that produces tone that people know and like.

[Zero4]

That schematic does not specify tube types. I'm guessing it's assumed I would know what they are supposed to be... Let me give it a shot - 12ax7, 12at7, 6l6?

...but scroll down- the layout does.

Hahaha.... I feel like a moron now. Didn't realize I was looking at a multi-page PDF file.

Well since you spoon-fed me a layout and everything, I guess that's what I'll have to build. Very nicely put together. Thanks!

EDIT: Just realized it's 6V6 not 6L6. So I should be OK with the lower power?

[martin manning]

If more than 20W or so is needed, the same basic AB763 circuit with 6L6's (and the bigger power supply to drive them) is a Vibrolux.

[Firestorm]

If more than 20W or so is needed, the same basic AB763 circuit with 6L6's (and the bigger power supply to drive them) is a Vibrolux.

Or 6550. (I usually wind up with KT88s for clean). 6L6s get dirty if you push them. Different power supply requirements. 6550s do not like too much grid resistance (grid loads and grid stoppers).

Not to be reiterative, but the reason the AB763 is clean is it has no mids. Turn the typical TMB stack up full and it's almost dead flat. This worked for Fender because single coils tend to be middy. If you want to boost mids, you have to go James (or active). Your client might not actually like that, tho, because it's not what we're used to hearing. The illusion of mid control might be enough.

[topbrent]

This is another good one. Powerful amp in a very small space. Your basic AB763 Normal channel. SS rectifier. Dumble style mid-boost for flavor

Allen Amps used to offer these cool little single channel, simple amps as a kit, but no longer has them available. There was a 5F2V brownface vibrolux normal channel, a 5F20 20w blackface deluxe normal and a 5F40 40w blackface bassman/vibrolux normal.

I configured mine for a cleaner tone than the original Allen layout, so I marked the changes on the layout and renamed it AB763 Small Chassis Layout.

[topbrent]

Another cool small space AB763-oid. The Luker Tiger.

Clever packaging of the circuit.

[topbrent]

S2 amps built this cool little Custom Deluxe AB763 into a Princeton Reverb sized chassis. He spec'd it with a passive loop that can be omitted if not wanted. Super clean build.

[Zero4]

Very nice! Thanks for all the info!

[rogb]

Can I also chip in with the good old AB763?
I just weighed my combo, 38 pounds with a G12-65, 18"w and 20" tall Baltic birch ply - 15mm side and 18mm top and bottom.

I built it into a 17"x8"x2.5" chassis I had for a Dlite build.
I used some RN65s after getting too much hiss with carbon comps.
Also used a fair few Orange Drops instead of Mustard types.
I "flew" the power board inside - no external caps.
Each channel has a mid control added with "stock" settings marked.
Passive loop added so I can plug in my Dlator and effects for some reverb/delay if I feel like it.

The normal channel has had some Dumble values added and PAB, LNFB(switched), Deep. Also NFB lift.

Vibrato channel has vibrato lift switch, a common mod for more gain.

The shared cathodes in the AB763 have been separated.

All Mercury iron, with 200mA available I could run 6L6, but I am happy with JJ 6V6.

Switchable recto - diode and 5U4GB for 445v and 420v.

LarMar PPIMV is also very useful for overall control.

I built a little ABY and vibrato box so I have 2 usable channels. Also always handy to have a 2nd channel if a friend wants to plug in for a jam etc.

I couldn't be happier with this amp.
With diodes and 6L6 plus the right speaker, I am sure you could stay clean and really loud.

I have a 1x12 open back extension cab with a C Rex and it sounds incredible sat under the combo. A LOT more bass!

[Zero4]

I'm off and running with the AB763 build according to the schematic and layout posted earlier.

I'm going to give it a shot with the 6V6's as designed. I have a sneaky suspicion that will be enough. If it isn't, I will modify as necessary to run 6L6's. (cross that bridge if we come to it)



I don't understand the terms "I "flew" the power board inside - no external caps." Please elaborate/photo/or link so I can understand?

[rogb]

The board sits above the end part of the main board on higher standoffs, like a flying bridge on a boat, as there is not much space in a 17" 2 channel build

[Zero4]

Ahh, I get it. Clever.

I won't have space issues with the layout I'm using. We're really trimming the fat here and just doing the one clean channel.