Oooohhhh........ Just when I thought it was safe to start browsing the forum again. Bitten again.

Question for Nik. Or anyone else who knows.......

AFD was announced after the 'no kits' announcement. Yet there is pricing for Pack 1 and Pack 2. What are these if not the old packs 1 and 2, (i.e. 1 = all the parts w/o  trannies, 2 = all the parts incl  trannies, neither assembled) Packs 3 and 4 are for assembled chassis' with and w/o trannies.

Thanks Todd, no nothing in particular at the moment. I was going to build a BM100 but didn't make my mind up in time.

I too am glad Nik will be bringing out loads more amps, but I still think it was a bad decision to stop all kits. Most builders who do kits don't offer every amp as a kit and this would have been the best solution I feel. Nik could have offered one Fender tweed, one 18/36watter, one Plexi, one OTS, etc. That would have reduced his support overhead enormously.

My problem is access to parts. I don't have sufficient knowledge to know which resistors to use where, which type and wattage, which are good quality, which are prone to problems etc. Same with caps, trannies, etc etc. My interest in amps was fired by Niks kits, if they hadn't been available I would still have been saving up for a TR or a Matchless and playing an old Fender Pro Tube and hating it.

Still hoping NIk will bring em back.........

Sorry to say, but I'm not much interested in buying a prebuilt amp. I came here in the first instance because of the kits, built three, was looking forward to one maybe two more, but now its not to be.

With the death of the kits the builders/modders are all off to the Amp Garage.

Shame but I think Nik has made a big mistake.

Change the whole lot for a 5 pin XLR. Makes much more sense. I did it at build time on mine. However you can rewire the whole thing for just a stereo jack and it'll still work (the LED for the PAB is ON when PAB is OFF though) Just search through Pickmasters posts to find the wiring layout.

That is seriously bad news.

If you follow the wires from pins 1 and 6 of both v1 and v2 you will arrive at the coupling caps. If you turn left at the junction you arrive at the plate (or anode) load resistor and right the coupling cap 

They are used to block DC from getting through to the next gain stage or tone stack. The value of the coupling caps does have a bearing on the tone.

Can't recommend Merlin Blencowe's book highly enough.

http://www.amazon.co.uk/Designing-Valve-Preamps-Guitar-Bass/dp/0956154506

I've just retubed my 1987 with some Russian 6V6Gt's (these are very common and are about £10/$15a pair) out of necessity as the stock tubes were microphonic now I've moved the amp to a combo. Rebiased to 23.6mV, B+ on  mine is 408. Might be a little hot but it does sound very good indeed. Quite a bit more chime and of course they do break up a little earlier, still bloody loud though. Defintely a Marshall sound and not a lot different from EL34's but a nice change.

Combo 2x12. Back plate bolts now changed for black. Need to fit wheels its heavy!  Next job is a 2x12 extension cab.

I read the thread on ampgarage and spent a while trying to set mine, but without a scope found it frustrating. I did post some info here
http://ceriatoneforum.com/index.php?topic=3428.msg16597#msg16597
but I'm not sure I know what I'm doing to be honest

I know I need to achieve AC 0v on the PI, but so many of my tubes were way out even the one I bought as 'balanced'. Couple with that and the fact the trimmer made very little difference to the AC balance makes me think my meter is just too crap!.

SO my first question is, if I order another 'balanced' Sovtek LPS tube what do I need to ask for? Balanced gain? which is what I think I got or balanced transconductance? (If I knew what it was I'd be better informed when I go to the shop!)

Secondly how accurate does my meter have to be to achieve this 0v AC? +- 1mV? or better? Not sure if mine is good enough but I'd like to try it again.

Cheers guys.

When I built my K-ulator I also built this 3U rack housing to match the OTS.

I bet if you asked any cab maker would make you one, it's dead simple.

Doc, I know that one of the extra pots on the front fascia is the OD treble bleed mod, but whats the other one? PAB level?

Thanks

Before posting on that ampgarage thread and exposing my utter ignorance I thought I post here and see if I am even in the right ball park. Any help apreciated.

I set up to generate a 440Hz signal from (yes I know) a file played on my mobile phone (mylaptop wouldn't do signal out and in concurrently, I need my external sound module back from my son!) in at FX loop return. Presence to 0.  Speaker out to my Hotplate set to load and the line out of the Hotplate to my laptop running that software I mentioned in an earlier thread. Line level set to minimise distortion.  This gives me a nice spectrum analysis of the amp output. I am able to capture the spectrum and save it. So far so good.

So I got this Sovtek LPS, supposedly balanced. DC across pins 1 and 6 measures from 4.5 to -2.3. When I measure AC i get 3.1volts. The trimmer makes no effect on the AC balance, however the trimmer does make a difference to the waveform, the second harmonic being minimised at 4.5 volts DC( trimmer full anticlock)

Next I try a Harma, DC 21.7 to 14.5. AC nearly in balance at 0.3volts. Second harmonic the smallest of all the valves I test.

Various other JJ tubes give quite varying results but no nearer than 2.2 vAC. In all cases the second harmonic is lowest at trimmer set fully anticlockwise. I now wonder whether I need to change one of the resistors?

So I try by ear and it does seem the HArma has something the Sovtek doesn't but its minimal and I now am beginning to suspect I'm chasing shadows and I too am wishing I hadn't read the ampgarage thread. 

I suspect the Sovtek and now need to ask more questions at Hotrox about what they mean by balanced. It seems transconductance balance is whats required here but I'm not sure thats what I got. The Harma seems to be getting closer to AC balance but the voltages are way different from what I was lead to believe was correct (Nik says 6vDC, others 6-10) I also check the two 3.3k grid resistors and find 3.66 on V4 and 3.46 on V5. Way off spec, by 10% and 4% so I wonder if I need to change those at least to get them to match?

Where to go next? Any guidance  welcome, including 'stop bothering', and 'you're out of your depth' or 'take it to a tech' 

Sure does. Just about to make a combo for my Plexi50. Black, purple and blue tolex.