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looking to improve my 50 watt
Posted: Sun Dec 27, 2009 9:34 pm
by johnnymenudo
Guys - I build a 50 watt metro amp kit last year to lead specs. I installed a lar-mar PPIMV. I have been using he amp with a variety of guitars - mostly humbucking pickups. Marshall 1960A classic cab with a combination of celestion 35 watters and weber stan spec speakers. I have come to the conclusion that the amp is harsh sounding and I am not happy with the lack of bass response.
If I crank the amp wide open and dime the PPIMV (essentially removing it), I can get a reasonable (but still slighty harsh) sound. Here are my settings: channels jumpered, vol I on 9-10, vol II on 6-7, treble on 8, mid and bass at 10, presence 0. The problem is, I cannot play at those volumes. I am starting to think attenuator possibly in conjunction with the PPIMV. I have tried the amp cleaner and lower volume with overdrive pedals and I just find myself saying why do I have a Marshall if I am going to do this. The tubes are the kit tubes, JJ - wonder if changing to NOS preamp tubes would help.
Any ideas or experiences?
Re: looking to improve my 50 watt
Posted: Mon Dec 28, 2009 4:59 am
by Roe
my 50w is neither harsh nor lacking in bass response. this sounds somewhat strange. however, I have to admit that I don't care for JJs (but it seems unlikely that they lead both to harshness and weak bass response)
Re: looking to improve my 50 watt
Posted: Mon Dec 28, 2009 3:43 pm
by johnnymenudo
I am using two G12M Celestion greenbacks and two weber "stan spec" speakers
http://forum.metroamp.com/viewtopic.php?t=9694" onclick="window.open(this.href);return false; in a 4 X 12 slant marshall cabinet.
Re: looking to improve my 50 watt
Posted: Mon Dec 28, 2009 3:55 pm
by Coot Boy
If the amp has a bright cap, I'd try removing it and see how you like that. Also back off the bass knob to less than half, diming the bass knob only serves to muddy the waters in Marshall circuits I reckon, I don't go past 10 o'clock usually but anyway, try removing the bright cap, let us know what value it is, if it's a .0047uf or 5000p you could try 100p but see how you like it removed first. After that you could try swapping out the .002uf cap on V1b for a .022uf if it does indeed have the .0022.
Re: looking to improve my 50 watt
Posted: Mon Dec 28, 2009 5:04 pm
by johnnymenudo
Coot Boy wrote:If the amp has a bright cap, I'd try removing it and see how you like that. Also back off the bass knob to less than half, diming the bass knob only serves to muddy the waters in Marshall circuits I reckon, I don't go past 10 o'clock usually but anyway, try removing the bright cap, let us know what value it is, if it's a .0047uf or 5000p you could try 100p but see how you like it removed first. After that you could try swapping out the .002uf cap on V1b for a .022uf if it does indeed have the .0022.
Already changed out the bright cap to 100p - I could try lifting it and see what it does. What changes does swapping to a .022 on V1b give?
Re: looking to improve my 50 watt
Posted: Mon Dec 28, 2009 5:08 pm
by Coot Boy
It will take out some of the bite for lack of a better tone word, you could be hearing it as harshness.
Re: looking to improve my 50 watt
Posted: Tue Dec 29, 2009 3:01 am
by jcs
Are you certain all of your speakers are in phase and correct polarity (all pushing forward)?
Part of the reason i run my 71 Marshall Smallbox 50 with a variac set at about 108 wall volts is it reduces volume a bit and is warmer and smoother when you rebias to 60-70%.
How hot is your bias/current draw on those EL34s?
Re: looking to improve my 50 watt
Posted: Tue Dec 29, 2009 5:33 am
by flemingmras
jcs wrote:Are you certain all of your speakers are in phase and correct polarity (all pushing forward)?
Part of the reason i run my 71 Marshall Smallbox 50 with a variac set at about 108 wall volts is it reduces volume a bit and is warmer and smoother when you rebias to 60-70%.
How hot is your bias/current draw on those EL34s?
Going with a lower voltage transformer will do the same thing and be safer on your heaters. Variacs have no place on an amp except for slow powering up an amp on the bench.
Re: looking to improve my 50 watt
Posted: Tue Dec 29, 2009 6:02 am
by jcs
Thanks for your opinion but i have 20+ vintage amps so i dont have time to mess around with anything but a variac and have had ZERO problems in 15 years of using a variac set to 105-110.
90% of my stuff never leaves the house and heater issues have never been an issue as most of the time i run around 110 wall volts except for my 71 Marshall and my 1950s amps its a bit lower.
The heater problems are normally with much use at below 100 wall volts and usually wear on preamp tubes most of my amps dont see many hours as i am mainly a hobbyist.
I dont go down to 90 wall volts or whatever Eddie Van Halen did, 105 is the limit.
Re: looking to improve my 50 watt
Posted: Tue Dec 29, 2009 7:18 am
by flemingmras
jcs wrote:Thanks for your opinion but i have 20+ vintage amps so i dont have time to mess around with anything but a variac and have had ZERO problems in 15 years of using a variac set to 105-110.
90% of my stuff never leaves the house and heater issues have never been an issue as most of the time i run around 110 wall volts except for my 71 Marshall and my 1950s amps its a bit lower.
The heater problems are normally with much use at below 100 wall volts and usually wear on preamp tubes most of my amps dont see many hours as i am mainly a hobbyist.
I dont go down to 90 wall volts or whatever Eddie Van Halen did, 105 is the limit.
Well vintage amps are one thing. Their turns ratios were made for a 110VAC wall voltage. However, a lot of guys will get the impression that it's OK to do this on amps with modern day transformers that have turns ratios designed for modern day wall voltage of 120VAC.
Then there's the guitarists that are the "if there's a knob there, that means it should be turned otherwise why would their be a knob there" types. And you know where that leads.
Maybe I should change my statement to "Variacs have no place but on the bench unless you fully and truly know what you're doing" because technically, in electronics ANYTHING can be done, but there's certain people you wouldn't share that info with because there's just some things you shouldn't do unless you know full and well what you're doing. Not saying that YOU don't, but anyone can be reading our posts at anytime which is why I'm very careful with what I tell people in regards to things I do with my rig. Certain people will read it and interpret it as "Well if he's doing it then it must be OK for me to do it too" when their amp/gear/power situation may differ from yours.
Re: looking to improve my 50 watt
Posted: Tue Dec 29, 2009 10:18 am
by 908ssp
As long as you turn the voltage down Variacs are not a problem but I don't think they are a solution for the OP's question.
I say change your speakers. Yes that is going to cost and your budget speakers may be the reason for your problem. Reissue greenbacks are way brighter and harsher than pre-rolas and I don't think Stan Specs stand up to comparison with Scumbacks.
Re: looking to improve my 50 watt
Posted: Tue Dec 29, 2009 5:04 pm
by jcs
flemingmras, i agree with you and understand your concern, however keep in mind wall volts are known to constantly rise above 120.
125-126 range is very common at times and this is dangerous to older amps especially those that are already biased at 70% at 120 volts, which is why i tell folks to NOT bias at 70%,especially older amps.
This is one of the main reasons i use a variac.
Re: looking to improve my 50 watt
Posted: Wed Jul 06, 2022 8:30 pm
by uiovbged332