new 50 watt build?

rockgod212 · Post by **rockgod212** » Wed Mar 18, 2015 6:55 pm

thanx, I didn't really know the tubes were used though, tricky lanquage I guess.

rockgod212 · Post by **rockgod212** » Thu Mar 19, 2015 5:41 pm

ok slight problem, low inputs don't work, cold solder joint perhaps. ok my thoughts on the rr mod- not sure if i like it or not, then i tried the xtra 100k for the voltage divider with the 470k part of circuit, much better- going to try 150k and 220k to tweak it up a bit, but the 100k worked well enough to tame the blocking distortion. wonder if anyone tried adding a treble peaker to this circuit, might try that as well. i did add a normal master vol to the amp to tame it as i crank crank a plexi ampwhere I live right now, but I gotta work the bugs out and still add the ppimv.

neikeel · Post by **neikeel** » Thu Mar 19, 2015 5:57 pm

rockgod212 wrote:ok slight problem, low inputs don't work, cold solder joint perhaps. ok my thoughts on the rr mod- not sure if i like it or not, then i tried the xtra 100k for the voltage divider with the 470k part of circuit, much better- going to try 150k and 220k to tweak it up a bit, but the 100k worked well enough to tame the blocking distortion. wonder if anyone tried adding a treble peaker to this circuit, might try that as well. i did add a normal master vol to the amp to tame it as i crank crank a plexi ampwhere I live right now, but I gotta work the bugs out and still add the ppimv.

I tried the RR but did not really like it (maybe a 2k7/0.68 and 820R/0.68 cascade might work better?

rockgod212 · Post by **rockgod212** » Thu Mar 19, 2015 6:59 pm

yeah I don't think I like it very much, so I think im just going to rip that out and try some other things, as I really built it to be a tone hub for pedals and stuff like that.

right now im trying to figure out why my vol. one (brite channel) low inputs aren't working, I get nothing out of it, tried reflowing solder, still nothing. somethings not right, I wonder if it has to do with this rr mod on a switch? back to the drawing board.

I might just re wire this thing to a stock plexi and see if it works from there. I thought I tried the low inputs before I did the mod, but I guess I didn't.

rockgod212 · Post by **rockgod212** » Thu Mar 19, 2015 7:08 pm

yeah I don't like the rr mod thing, so im going to rip that out, go back to stock and get the inputs working right, then im going to try to set up 2 lead channels ala bray style. I think that would work better for what im after.

rockgod212 · Post by **rockgod212** » Sun Mar 22, 2015 7:22 pm

I got the inputs wired up correctly, i followed a bad layout. 1 wire was in the wrong spot. im changing th enormal channel to 820/1u or 1.5u with a 470p in the mixer to brighten it up some, im going with a dual lead type spec. the 250uf of the normal channel will be on a switch for when I want it. ordered some 760p lemco's and a 1500p mallard ceramic rod type cap for a brite cap, lets see if I like that better than the 4n7 lemco brite cap, im not changing the lemco until I get the ppimv installed and I get the variac going.

yep, I bought me a variac, cant wait for that to get here, im just going to lower it bit by bit to find the sweet spot.

rockgod212 · Post by **rockgod212** » Sun Mar 22, 2015 7:27 pm

yeah I used them, I think they sound great so far, im still tweaking the amp though. im using g12-80's right now though, next thing to get is some greenbacks, so the amp feels a bit stiff still. might try to mix the some speakers later down the road.

anybody only use 1 half of the 50u mains cap? how's the feel if so? might try it.

Tone Slinger wrote:Did you use Classic Tone transformers ? If so, I'm interested in your opinion of them. I got a CT PT(Thanks Shannon ), but am a little hesatant about what I choose for the OT. I've heard VERY mixed opinions about CT transformers.

rockgod212 · Post by **rockgod212** » Mon Mar 23, 2015 10:41 pm

i got the ppimv wired in and it sounds fantastic, no fizzy's once so ever. I got some microphonic pre tubes, so im waiting on my nos 6n4 china pre's to come, and im waiting on the variac and a vintage 80's mxr 6 band, cant wait to try these with the amp. im saving my penny's for some greenbacks now.

rockgod212 · Post by **rockgod212** » Mon Mar 30, 2015 5:56 pm

I just got my variac. started with 436vdc@123vac, now im running 400vdc@115vac biased @42mV. sounds fantastic. gonna go a bit lower, im thinking 110vac will be it. I don't think I i will be able to drop below that. I dropped 36vdc on the plates just by dropping AC 8volts.

so how low should I go?

danman · Post by **danman** » Mon Mar 30, 2015 9:13 pm

The guys over in the "Van Helen builders" subforum have taken there amps down below 90 volts to help achieve the brown sound. If I variac down I usually like to keep an eye on the heater filament voltages and try not to run them below 6 volts or so.

rockgod212 · Post by **rockgod212** » Mon Mar 30, 2015 10:00 pm

yeah I read a lot of that so far, right now my heaters are still at 3.1vac. the thing im worried about is?

if I go down to 90vac, im afraid my plate voltage would be something like 250vdc or some crazy number like that. like I said I dropped 36vdc with just 8vac drop, so heres a calculation if I keep dropping 8vac at a time and my plates drop 36vdc for every 8vac step down:

400vdc@115vac
364vdc@107vac
328vdc@99vac
292vdc@91vac

is that really safe to run a 50watter like that? how low have people taken 50watt amps down too?

Lbrown3743 · Post by **Lbrown3743** » Tue Mar 31, 2015 1:04 am

I’ve run mine down to around 60 and lower. I don’t know what the plate voltages were but the amp still played fine. I’m not an expert but I hear the term "red plating" a lot when it comes to this subject and I’ve never had it happen. Unless you were talking about a vintage 50 watt Marshall or had NOS Sylvania tubes installed I wouldn’t worry about it. Maybe after a thousand or so hours at low voltage tubes may or may not get ruined then a new set for a 50 watt is not too much money. Again I’m not an expert and this all in my opinion.

danman · Post by **danman** » Tue Mar 31, 2015 7:36 pm

You won't hurt the amp by running the voltages lower. You could take it down to where the amp stopped functioning if you like but it most likely would not sound to pleasant. The only real issue is the lower heater voltages causing damage to the tube's cathode at some point. I'm not sure of the exact number at which the tube life would be shortened by the lower heater voltages but I do remember reading that running the filaments to far below or above their recommended voltage will shorten the life.

rockgod212 · Post by **rockgod212** » Tue Mar 31, 2015 9:50 pm

ok thanx guys. I will take it lower soon.

rockgod212 · Post by **rockgod212** » Tue Jun 16, 2015 5:31 pm

wow oh wow, I just paired this build with a hellatone g12h-30 and a celestion v-type. this combo when pushed by my mxr zw od pedal is the tone ive been searching for all these years. it just sounds awesome.

waiting for my lopaline 2x12 cab to come, as this cab will be home for these speakers.

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