Found this site the other day.
http://mec-pickups.de/modules/news/NewsList.php?typ=NEWS&katID=1727
They will make stacked pots to your requirements. I was looking to be able to build the HRM tone stack into the front panel with no mods to the faceplate. Knobs would be a problem, it seems you can only get the knurled metal ones for this style of pot.

Not ready to pull the trigger yet on these as I cant justify another OTS at the moment. Not ruled out converting my OTS to HRM though, just to get some control over the OD channel tone.

Actually you can get a Plexi 50 chassis into a smaller box than Niks. The chassis is actually 471x 176mm so you could get a smaller shell made.  My box ended up about 550mm x 230mm.

That is one of the nicest tones I've heard from an OTS.

It was loud wasn't it!! I see your master was nearly at 2 o'clock.

Not directly applicable in this case but other drawbacks with the G# are no patch naming. Nice reverbs tho'

I reckon this should be in a FAQ page on Niks site. You have a 50-50 chance of getting it wrong and once you know its easy to fix.

Two out of three of my builds suffered that way.

yes. It won't work without a Kleinulator or similar.

Here's the mod I mentioned. It applies to the clean channel but there's no reason you couldn't mod it to work on the ratio pot.
http://ceriatoneforum.com/index.php?topic=740.msg5657#msg5657

Check out pickmasters boost mod.

Quite right, I'm more concerned about the OD channel being overly bright. It works well at very low gain levels with single coils, but put humbuckers through it witha bit more level and it becomes too harsh.

One thing I have done over the weekend , in addition to measureing the voltages was to up the resistor following the v2b coupling cap to 220k (I found an old list of mods the 'mondoslug' posted and this was one he did specifically to lower the treble on the od channel) This has helped, whether its enough I'm not sure yet.

I also found that my PI tube is quite out of balance so I need to try a few others to get that recommended difference of 6-10 volts between v3a plate and v3b plate

25uF 25v are quite common, lower values are very difficult to find. I need some 1,2.2, 4.7 uF 25 volt. If not then I will need some Poly film with quite high values. I found these
http://www.audiocap.co.uk/400v-polyprops-icel-phc-series-22-c.asp, anyone know if they're any good? They get a bit expensive in the higher values but that site has caps way more expensive than that!

Good to know the Cornell Dubilier are good. However a search of Mouser produces a quite baffling array of different types.

Mouser also have an annoying habit of displaying in their search results masses of items they don't have in stock, and look unlikely to stock anytime soon. Plus they have loads of caps I have no idea about and names I don't recognise.

Thanks Erwin. I was aware of those two. I can't find any 25volt electrolytics like Nik uses for the cathode bypass caps though . ( I actually need some for a DrZ EZG50 that I want to mod to lower the bass, it uses 25uF in that position)

SO would the Cornell DME range be as good as the Sprague PS? Most suppliers miss out the intermediate  values like 15nF,33nF etc from the SPrague range and I really don't know what else is acceptable quality wise. What I want to do is get at least 2 of every value that I'm likely to need so I can experiment.

I am about to do the same, but v1a is and should be different to v1b, likewise v2, and we can vary the PI with the trimmer so what did you set yours to? How does yours compare to the voltage chart that Nik uses?

How are you controlling your mains voltage? We get a considerable swing depending on time of day here and I would guess this is pretty much the case everywhere. I've been considering something like a Furman but the decent ones are expensive.

Hi guys, I need to pick your brains.  I need a good supplier for caps here in the EU.

I specifically need:-
Low voltage electrolytics for cathode bypass in the range 1-5uF OR
1-5uF poly (prop or ester) film caps for same application

I also want to get a good stock of signal path caps for modding ie Mallory or SpraguePS or similar. Most suppliers seem to keep a limited range of values or names I don't recognise. If you can recommend other brands that will do the business please chime in (and none of that £10 a cap audio snake oil stuff please )

My reasons for needing this, I have become acutely aware that I'm only using the clean channel of my OTS and pedals to get a drive tone simply because the OD channel is too harsh with the clean set how I like it. I need to do some work on signal path through v2. I have been reading Merlin Blencowe's book and think I now understand enough to go it alone and experiment. I might even convert it to HRM if I can't achieve what I want. I have noted all the mods that everyone has documented on here and I will work my way through those to see if they achieve whats needed. Until now I've just bought a few parts and done some minor mods, but I think I need a stock of parts so I can keep tweaking until its there.

I note that pickmaster mentioned a cut control mod on his recent OTS and I'd be interested to know a good way of doing that.

TIA

Aahhh, you're trying to fool us aren't you?? 

Thats not a valve its a bottle neck

Correct, now follow the schematic and you will see that the ac coupled signals from the PI have a connection from the bias supply, thereby giving an overall -ve dc voltage. The value of this negative dc voltage is what controls the flow of electrons in the tube. And note we are always setting the quiescent, ie NO AC signal, bias voltage.


Not quite. Both tubes are fed exactly the same signal but inverted. The way the valves are working is that as one valve is amplifying the +ve side of the signal, the other is being fed the negative side of the signal and is driven in to cutoff and produces no output, the classic push-pull output stage.

Even I, the valve electronics newbie know this is utter pants. The bias pot does not control the current directly, it controls the negative voltage (read the schematic and look how the bias supply is rectified) on the grid of BOTH output tubes. If you have the same B+ the same cathode voltages (which you do) and the same arrangements for grid and screen voltages then the bias voltage does affect BOTH tubes. And its purpose is to get the valve operating in the correct manner. Nik did not do anything different to any other amp designer, this is how variable, fixed bias octal tubes are setup. And yes you can set it to too high a quiescent current AND risk redplating if you so desired.

Mr Fabulous, you might well be a highly qualified electronics engineer, but you are obviously not familiar with the way valves operate. Please do some research before handing out misleading information that might harm a users amplifier.