+1

I wouldnt convert a Non-HRM to a HRM, just because the OD may seem a litttle darker than the Clean. Try different tubes in position V2, before you perform any mods. E.g. a Electro Harmonic 12AX7 tend to be a bright tube, so you could try that.

I wouldnt worry too much about the first two alterations (treble cap and slope resistor values), unless the amp sounds really wierd. The 47p on the master volume pot - depending on the amps overall tone - could seems a bit on the high side. I have settled on 15p istead.

However, the most important tool isyour ears, so before heating up the soldering irion, LISTEN carefully to the amp and how it behaves with your guitar and gear, both at home and in a band/gig situation. Spend a a couple of month playing the amp, before deciding to change anything.

There was a guy at this forum, "jzucker" - and I don't mean to put him down -  but he bought/build an overtone amp and only played it for something like 2weeks, after which he decided that the amp should be modified. And he  began modifying the amp intensively and posting a lot about his mods. After a couple of month he gave in and sold the amp. This behavior (and not the person, 'jzucker') seems a little odd, because an overtone amp (or any decent Dumble clone amp) can be made to sound just as good as any original dumble amp. All you need is using your ears and a little patience

To tweak a particular amp, you don't get great results simply by following other peoples schematics.... no matter what you decide to change in the amp, the component values that wok with one amp, will not produce a similar result in the next amp. They all sound a little different due the a number of small differences in components. transformers, the construction (e.g. the length of wires), the particular tubes in the (pre)amp used AND the speakers AND instrument used with the amp. So trust your own ears and don't rely too much on what other people have used in their amps.

looks like good quality cloth wire. I've heard it is prefered because of it warm and fluffy sound.

Hi - just wann chip in regarding Kevin's cabs. I've build a 2x12 cab, pine top, bottom and sides plus 4mm front and back baffles. The trick is to only mount the cab with one speaker unit and leave the other 'speaker hole' empty. This cab works like a giant acoustic guitar and sounds absoultely amazing. So I can highly recommend Kevins designs. 

I was not reffering to you.....

That's a good decision..... more people should probably buy finsihed amps.

Some of the questions on this forum indicate, that not all people have the knowledge needed for high voltage amps, in which case its pretty stupid to mess with such amps.

Which is why you need to check your bias   : .............. Have you done that
Get your bias down to 30-35 mV

If this doesnt help you have an error in your amp, somewhere  

My master goes to 3 o'clock before overdrive - with a strat and volume on 6½ !!

Great, have you ordered a kit of a completed amp?

The answer to all you questions is that it doesnt really matter, since the overtone is and amp that makes its sound in the preamp.

Your questions are more relevant for a non-mastervolume amp, that get its from the powertubes.

Any good set of power tubes will do ;-)

ok, thanks

In clean mode? 

My OTS (with single coils, volume on 6½, rock on etc) mine doesnt get dirty until 7!! on master vol.
Check the biasing of the output tubes. Yours must be skyhigh like 50mv or so  . Get it down to 30mV and your amp will be clrean 

Any news on the delay settings on this clip??

Check the wiring on this pic