Plexi Master Volume Mod?
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STRATDELUXER97
Stratoblaster Tone Meister
Re: Plexi Master Volume Mod?
I use a phase inverter master volume mod on my 1987 73 50 watt head....You just substiute a double ganged 100k pot in place of 2 fixed resistor values...If you keep the pot on 10,the circuit is untouched...As you roll the pot towards 0 you add gain to the amp...The other mod is the way a JCM 800 is done,but that's done within the preamp and changes the Plexi style Marshall's clean tones....Another option is pedals in front of your amp(That's what I do) or an attenuator(Marshall PowerBrake,THD etc..) If you require the gain of a JCM 800 then you'll need to mod your 1987 in that direction....
John
I use a phase inverter master volume mod on my 1987 73 50 watt head....You just substiute a double ganged 100k pot in place of 2 fixed resistor values...If you keep the pot on 10,the circuit is untouched...As you roll the pot towards 0 you add gain to the amp...The other mod is the way a JCM 800 is done,but that's done within the preamp and changes the Plexi style Marshall's clean tones....Another option is pedals in front of your amp(That's what I do) or an attenuator(Marshall PowerBrake,THD etc..) If you require the gain of a JCM 800 then you'll need to mod your 1987 in that direction....
John
proxy
New member
Re: Plexi Master Volume Mod?
Well here is what I'm thinking...
I want to sell off my tsl122 and get a 50 watt amp. I'm sort of between a Marshall 1987 and a Fender Bassman. I'm shooting for mostly a Pearl Jam tone, which requires pretty good cleans (a little flavor on them tho) and some vintage/modern distortion.
Ideas?
Well here is what I'm thinking...
I want to sell off my tsl122 and get a 50 watt amp. I'm sort of between a Marshall 1987 and a Fender Bassman. I'm shooting for mostly a Pearl Jam tone, which requires pretty good cleans (a little flavor on them tho) and some vintage/modern distortion.
Ideas?
Vasshu the humanoid typhoon
Unseen
Re: Plexi Master Volume Mod?
Uh why mod it with a @£€€$mastervolume??
:burnout:
Uh why mod it with a @£€€$mastervolume??
:burnout:
L
Lewguitar
Guest
Re: Plexi Master Volume Mod?
Master volumes between the phase invertor and output stage don't really do much (IMO...) unless you also add a gain stage to the preamp. Then you'll have a JCM 800...
Also, when you turn that kind of master volume to "10" the circuit is still differant than if the master volume pot wasn't there in the first place. The reason is: If you use a 1 meg pot for the master volume, you've added a 1 meg grid load resistor to the circuit...or so I've been told.
Lew
Master volumes between the phase invertor and output stage don't really do much (IMO...) unless you also add a gain stage to the preamp. Then you'll have a JCM 800...
Also, when you turn that kind of master volume to "10" the circuit is still differant than if the master volume pot wasn't there in the first place. The reason is: If you use a 1 meg pot for the master volume, you've added a 1 meg grid load resistor to the circuit...or so I've been told.
Lew
STRATDELUXER97
Stratoblaster Tone Meister
Re: Plexi Master Volume Mod?
Lew....Mine isn't set up that way and truthfully I don't use the phase inverter master volume at all...That was already setup when Trace Allen sold me the amp..His amp actually....I don't notice the difference you talk about with the pot on 10? Mine replaces 2 220k grid load resistors(I think without schematic in hand) with a stacked 100k dual ganged pot...One of Ken Fischers ideas I think also? I usually run a pedal or more into the front of mine and I'm good to go...
John
Lewguitar said:
Lew....Mine isn't set up that way and truthfully I don't use the phase inverter master volume at all...That was already setup when Trace Allen sold me the amp..His amp actually....I don't notice the difference you talk about with the pot on 10? Mine replaces 2 220k grid load resistors(I think without schematic in hand) with a stacked 100k dual ganged pot...One of Ken Fischers ideas I think also? I usually run a pedal or more into the front of mine and I'm good to go...
John
STRATDELUXER97
Stratoblaster Tone Meister
Re: Plexi Master Volume Mod?
Lew...Here's the way my phase inverter master volume mod is setup...Right off the Obsolete Electronics Website....
"BIAS SPLITTER RESISTORS: This is where the bias (or C- for the old timers) is fed into the output circuit. These resistors are also the grid resistors for the output tubes and as such have an impact on the gain of the output stage. The "standard" value is 220K ohms, and you should not exceed this value. However, many players lower the value of this component in order to get more grind from the amp, or what is sometimes referred to as a "browner sound". It is also a popular place to install a master volume circuit"
Lew...Here's the way my phase inverter master volume mod is setup...Right off the Obsolete Electronics Website....
"BIAS SPLITTER RESISTORS: This is where the bias (or C- for the old timers) is fed into the output circuit. These resistors are also the grid resistors for the output tubes and as such have an impact on the gain of the output stage. The "standard" value is 220K ohms, and you should not exceed this value. However, many players lower the value of this component in order to get more grind from the amp, or what is sometimes referred to as a "browner sound". It is also a popular place to install a master volume circuit"
STRATDELUXER97
Stratoblaster Tone Meister
Re: Plexi Master Volume Mod?
Easiest to go with the attenuator or some great pedals....If you do a JCM 800 preamp type master volume mod,you will kill your Plexi/Fender like clean tone,plus you will give up the ability to daisy chain the different tones of each of the 4 inputs...You also give up two of the 4 inputs for the master volume mod...Buy a JCM 800 if you need that tone,but in my opinion the Plexi Marshall sound "IS" "The Marshall Sound" Hands down! The JCM 800 was and still is a great bright grinding 80s tone,but it wasn't known for it's very lacking,low output,and lifeless clean input...With the Plexi and the right combination of things and no mods,you can have it all... :wink:
John
Easiest to go with the attenuator or some great pedals....If you do a JCM 800 preamp type master volume mod,you will kill your Plexi/Fender like clean tone,plus you will give up the ability to daisy chain the different tones of each of the 4 inputs...You also give up two of the 4 inputs for the master volume mod...Buy a JCM 800 if you need that tone,but in my opinion the Plexi Marshall sound "IS" "The Marshall Sound" Hands down! The JCM 800 was and still is a great bright grinding 80s tone,but it wasn't known for it's very lacking,low output,and lifeless clean input...With the Plexi and the right combination of things and no mods,you can have it all... :wink:
John
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Hellion
New member
Re: Plexi Master Volume Mod?
That's what I want to know. Those amps were designed to do one thing and that's to be loud. If you put in a Master Volume, you lose that power amp saturation that you get at high volume. If you need a Master Volume, buy an amp that has one on it.
Rid said:
That's what I want to know. Those amps were designed to do one thing and that's to be loud. If you put in a Master Volume, you lose that power amp saturation that you get at high volume. If you need a Master Volume, buy an amp that has one on it.
proxy
New member
Re: Plexi Master Volume Mod?
Well I don't really want to be over the top loud with it, I play at smaller venues and in a basement with a band. I'm basically trying to see what my options are since the master volume mod seems to be a common mod that I feel that I would be capable of doing as well as cheaper then an attenuator.
Well I don't really want to be over the top loud with it, I play at smaller venues and in a basement with a band. I'm basically trying to see what my options are since the master volume mod seems to be a common mod that I feel that I would be capable of doing as well as cheaper then an attenuator.
Pandemonium
New member
Re: Plexi Master Volume Mod?
Attenuator.
Attenuator.
STRATDELUXER97
Stratoblaster Tone Meister
Re: Plexi Master Volume Mod?
Proxy...Here's my opinion on the difference between preamp distortion and power amp(tube) distortion...The preamp distortion is great for getting gain at low volume levels,but that type of distortion is buzzier and not natural sounding like the power tube distortion you hear when an amp is cranked up really loud...The cranked up Marshall power tube distortion tone is rich in harmonics,with a nice tube compression,also your notes seam to effortlessly fly from your guitar and out of your amp with singing authority...Listen to old Clapton/Cream,Allman Brothers,AC/DC etc...where you basically hear output tube distortion that is generated by high volume levels..This output distortion also gives rise to overall low end,midrange,and highend levels(Munson Curve) The JCM 800 is great also but you still have to crank er up to get that roar and cutting tone that we all love about a Marshall...
Again...Either a good attenuator or some pedals would get you there.... :wink:
John
proxy said:
Proxy...Here's my opinion on the difference between preamp distortion and power amp(tube) distortion...The preamp distortion is great for getting gain at low volume levels,but that type of distortion is buzzier and not natural sounding like the power tube distortion you hear when an amp is cranked up really loud...The cranked up Marshall power tube distortion tone is rich in harmonics,with a nice tube compression,also your notes seam to effortlessly fly from your guitar and out of your amp with singing authority...Listen to old Clapton/Cream,Allman Brothers,AC/DC etc...where you basically hear output tube distortion that is generated by high volume levels..This output distortion also gives rise to overall low end,midrange,and highend levels(Munson Curve) The JCM 800 is great also but you still have to crank er up to get that roar and cutting tone that we all love about a Marshall...
Again...Either a good attenuator or some pedals would get you there.... :wink:
John
proxy
New member
Re: Plexi Master Volume Mod?
I really want that power amp distortion, but I'm trying to figure out how I can get both plexi cleans and distortion out of one plexi. A pedal is basically solid state premp gain, but those ts9's seem to do it for people, so maybe in the not so distant future I'll send one out your way.
Just trying to weigh my options and you've been very helpful.
Thanks, I'm gonna prolly go pedals and preserve the plexi clean since at the moment I can't afford a two amp rig. Also attenuator money can go to a nice cab.STRATDELUXER97 said:
I really want that power amp distortion, but I'm trying to figure out how I can get both plexi cleans and distortion out of one plexi. A pedal is basically solid state premp gain, but those ts9's seem to do it for people, so maybe in the not so distant future I'll send one out your way.
Just trying to weigh my options and you've been very helpful.
Vasshu the humanoid typhoon
Unseen
Re: Plexi Master Volume Mod?
Plus the 1987 actually sounds good a normal volumes with a good pedal, and then you can crank it in studiowork and get that real Marshall sound.
Just link the two channels.
Plus the 1987 actually sounds good a normal volumes with a good pedal, and then you can crank it in studiowork and get that real Marshall sound.
Just link the two channels.
