But your picture doesn't seem to be the same as the one on the Ceriatone site:

http://www.ceriatone.com/images/layoutPic/HeyWhat/HeyWhat103.jpg

From the Ceriatone layout image it seems to have seperate heater secondaries for preamp and poweramp, and only the poweramp one has a centre tap? Maybe this could reduce preamp hum?

I have a pre-built DR103, but haven't inspected the heater circuit. I might do it just to see if it really has dual heater secondaries.

Good luck with your build!

This is my new HeyWhat 103. Chassis was built at Ceriatone, pine cabinet built by me (only missing rubber feet, and possibly rear plate). Only 2xEL34 installed when the pictures were taken.

http://picasaweb.google.com/torquil/CeriatoneHeyWhat103#

Initially I was considering getting a kit from Ceriatone, but after seeing pictures of the chassis internals, I knew there was no way I could compete with that kind of build quality...

Nik kindly modded it for bass guitar which worked out great (increased coupling caps). I then modded the Bright channel to include the unused half of V2 to get a bit more preamp gain. But not like a high gain amp. Worked out beautifully after some adjustments.

Normal channel is great for bass guitar, into at 1x15+2x8 front vented bass cabinet. Also great for clean guitar into a 1x12 oversized open-back cabinet.

The "Bright" channel (which is no longer a particularly bright channel) now provides more (and different) preamp gain than you would get on the stock model.

Considering adding a rear plate on the cabinet. Since it is quite heavy because of those big transformers (19kg) I opted for holes in the sides for carrying, instead of a handle on top.

Very, very good!!!

Actually, on the Hiwatt circuit I have in my HeyWhat, I think it is possible to include separate master volumes without influencing the tone coming from the preamp much. That way you have more possibilities with the amp. The difference would be that when an original Hiwatt circuit is cranked, the two channels are combined just before an overdriven preamp tube. If I mod mine, the two signals would be combined before the next preamp triode, which is after the tone stack, and the signal is therefore a bit weaker there. Also, that tube is differently configured. So there could be some noticeable difference. I would like to try it some time.

I assumed many Master volume amps are designed around both preamp and poweramp distortion/tone, not just preamp. Also, I would expect that many non master volume amps were not designed to distort at all, since there are many electrified musical genres where distortion is not considered to be good.

I expect a fantastic tone from my HeyWhat, completely independent of what the original Hiwatt tone is. Actually, I got this model because it is a fantastic bass amp at the same time (with some small mods).

Attenuator is a good idea. That way you can also have output transformer distortion. I think the tone of preamp distortion can vary a lot, depending on how much careful though has gone into the design. If you don't design for a great preamp distortion tone, it will not be there in the amp.

Good point about the wattages. I have a couple of smaller guitar amps which fit your scheme. I can use my HeyWhat 103 with two power tubes pulled for clean (or no tubes pulled), together with my Mesa Express 5:25 for dirty. It is about half the wattage. Or my 10-20W (dep. on which tube I use in it) DIY AX84 SEL amp for dirty. And the top of the cake (as we say in Norway): I can have all four tubes in the HeyWhat, and use it as a bass amp!

Yes, I'm thinking of rewiring a bit inside my HeyWhat, so that the Master only works on the "Bright" channel. Since I use the other one for clean sounds, its "Master" volume could be at maximum all the time. The downside is that the noise from the "Normal" channel would be there no matter how low I turn the input volume. Also, It is necessary to mess with the circuit topology to do this.

- Torquil

I read a very interesting article written by Hartley Peavey. His claim was that the "power tube distortion" many seek is not just power tube distortion. It is also distortion created in the output transformer. So if you accept this, you would need to switch between e.g. two/four power tubes and at the same time switch between two different output transformers when going from clean to distorted, and vice versa.

He discussed an interesting effect occuring in the OT, called a dynamic bandpass filter. As the magnetic field approaches saturation, a bandpass effect occurs. This bandpass effect depends on the amplitude of the signal going in to the OT. He claimed that this effect together with the power tubes distorting at the same time, was the ultimate tube amp power sectio distortion.

The article ed with the Peavey's TransTube tech, but most of it is interesting stuff about tube amps:
http://www.peavey.com/support/technotes/hartley/chapter_3.pdf

It would be hard to get this dynamic bandpass effect in the OT, as well as getting a loud clean sound from the same amp, unless two different sized OT's are used...

I have just received a modded Ceriatone HeyWhat 103 from Nik, to use as a bass head. He increased the coupling caps from 22nF til 47nF, and on the bright channel from 1nF til 22nF. This was specifically because I wanted to use it for both bass and ordinary guitar.

Magnificent bass tone I must say! I use it through an old 1x15+2x8 Peavey bass cabinet with front vents. I play a six-string, and it handles the B-string nicely, at least at the volumes I have tried it at (moderate, not rock stage levels).

Actually, I have modded the Bright channel into a general three gain stage guitar channel capable of a moderate amount of preamp distortion. The stock one leaves halv of V2 unused. I included it in the Bright channel.

So the Normal channel is for bass or clean guitar, and the "Bright" channel is an OD channel for guitar.

The guitar tone is great on both channels, both  for signle-coils and humbuckers. In this case I play it through an oversized 1x12 open back cabinet (custo mcabinet inspired by a Mesa Boogie model).

For me, 100W is enough for bass, and actually I wish people would play a little less loud (lost of ear damage among musicians....). I know most disagree with this :-)