New 2550 build (Page 2 of 2)

Yo don't need to check it every evening! I can't tell you if it's too hot or not. It depends on you B+ voltage. This can be measured at the standby switch. Then do a simple ohms law maths and you got your bis value for a given tube!

Cheers!

I own an original 2553,

As wonderfull as the amp is, there are still imho some design fallabilities which can be easily upgraded for a better sounding amp, especially on a clone hence it has no collectors value and therefore has no need to stay excactly original. The clones which I have listened on youtube were too gritty and trebly when compared with my original jub, even with the compression present of the cheapo audio equipment and Youtube.

A couple of changes which I like,

Put 2n2 capacitors in parralel across the diodes, this rounds of some of the harsh clipping that the diodes produce and will make the distortion of the diodes more 'tube' like, with a rounder wavelenght instead of a cubic wave length. Great to give the jub a more smoother and bluesier voicing like Joe. Maybe not so suitable if you wish to have a gritty Hard Rock Jub.

Removal of the bright cap, I believe the 470p one, especially at lower volumes the amp will benefit from it.

Removal of the 47p cap on V1 (if present), like the later circuit.

A second master volume PPIMV is easily installed with 5 dollars in parts, preferrably the Larmar, though I like it merely to roll of some volume, and not to use it for bedroom levels. This will give unpleasant fuzzy PI distortion. Plus in a High Gain amp the actual working will be of less benefit then a simpler circuit like a plexi. Therefore it is important to play with the normal master volume and the PPIMV.

Greetings,

Nope, it's a Post Phase Inverter Master Volume, so it works for the clean as well as the Lead channel. You could make the PPIMV switchable perhaps. 'On' for rhythm and 'off' for lead boost.

I use it to crank the normal volume to around 7/8 which is my preferred setting, I do not like the normal mastervolume any higher. But with the PPIMV still keep the volume as it would be on the audible range of 5 without PPIMV. My PPIMV dialed in at around 6/7, so a slight back off in volume. Lower then 5 and the sound becomes to fuzzy and bassy, hence it is important to play with normal and PPIMV on basically any high gain amp. I also switched the Caps in the PI for 0.1uf's. It gives a nice round sound, but if you stick with the normal .022U, you should be able to back the PPIMV even further beyond 5, with the 0.1u it becomes to fuzzy

I didn't apply the common mod to switch from rhythm channel to lead channel instead of clean channel to lead because I see the Jub as a one trick pony, I dial in my tone and work with the guitar instead of pushing the switches too much. The difference between the lead and rythm channel can be easily dialed in with the volume and tonecontrols on the guitar.

88 Jubes are in Europe much less collectable, but the circuit is the latest and best sounding. So Tone wise you're suited. Mine was an early 87 within the 600 range. Nice and Early, but also inferiour circuit, I converted it to later specs, and did a few extra mods that can easily be reversed.