How do you increase headroom in a 50w JMP?

[sdn25]

I have a 50 watt jmp with about 440v HT and was wondering if I can raise it anyhow to get more headroom? I’m sorta tryna get the 50 to sound more like a 100w.

If there are other ways of increasing headroom as well please do tell.

 

[playloud]

Easiest thing would be lower gain preamp tubes. ECC81/82 are drop-in replacement for ECC83 that will make a noticeable difference in V1 (ECC82/12AU7 for the lowest gain). Some people also like these tubes in the phase-inverter position (V3). Certain power tubes will also make a difference (true 6CA7s should have marginally more headroom, for example).

There are obviously more dramatic things you can do, from changing the preamp circuit to replacing the PT for a higher B+. I'd rather let the amp be though, and enjoy it for what it is.

 

[Pete Farrington]

What exactly do you mean by headroom? eg describe what you want without using the H word

 

[Gene Ballzz]

I always thought "headroom" was the space between my lap and the mixing console?

Just Grinnin'
Gene

 

[sdn25]

What exactly do you mean by headroom? eg describe what you want without using the H word

Right, a 50w is generally associated with smoother compression with less pick attack due to the lower power and a 100 with agressive pick attack and punch. My goal is to make the 50 watt sound more like the 100 watt.

 

[Dogs of Doom]

what power tubes are you running?

switch to KT-88

(you will probably have to do some mod's to the bias section)

 

[sdn25]

what power tubes are you running?

switch to KT-88

(you will probably have to do some mod's to the bias section)

Current production EL34s

 

[Gene Ballzz]

Such is the nature of the main difference between the 100 wat and 50 watt models! Surprisingly, the SV20 is closer to the 100 watt than the 50 watt, in that regard! Within its volume range, of course. If you want use a distortion box, you can use a 50 or 100 watt. If you want your amp to BE the distortion box, get a 50 watt! They both occupy their own cherished territory in great rock music!
Just Sayin'
Gene

 

[sdn25]

Such is the nature of the main difference between the 100 wat and 50 watt models! Surprisingly, the SV20 is closer to the 100 watt than the 50 watt, in that regard! Within its volume range, of course. If you want use a distortion box, you can use a 50 or 100 watt. If you want your amp to BE the distortion box, get a 50 watt! They both occupy their own cherished territory in great rock music!
Just Sayin'
Gene

I get that, but my goal is to make the 50 sound more like the 100. Maybe circuit changes, tube changes only to an extent though, I can't afford to buy a new PT OT etc lol. I understand there is only so much you can do where beyond id need to get a 100w but I wanna try out the limited options that are left.

 

[Crikey]

I have a 50 watt jmp with about 440v HT and was wondering if I can raise it anyhow to get more headroom? I’m sorta tryna get the 50 to sound more like a 100w.

If there are other ways of increasing headroom as well please do tell.

What would more headroom sound like to you? Just wondering
Maybe try eq for a “ clean boost”?
Not sure f increasing head room beyond 50 is capable, but have been wrong before.

 

[sdn25]

What would more headroom sound like to you? Just wondering
Maybe try eq for a “ clean boost”?
Not sure f increasing head room beyond 50 is capable, but have been wrong before.

It would sound tighter, more punchy and aggressive with more pick attack. Im not looking for more gain. I run the amp cranked into an attenuator hence why I am looking for the higher headroom since gain is plenty. I just want more pick attack and low end tightness.

 

[Browneyesound]

You could try increasing the filtering.

 

[Gene Ballzz]

It would sound tighter, more punchy and aggressive with more pick attack. Im not looking for more gain. I run the amp cranked into an attenuator hence why I am looking for the higher headroom since gain is plenty. I just want more pick attack and low end tightness.

Ahhh, the plot thickens! What attenuator are you using? They are CERTAINLY NOT all created equal! Most passive, resistive units are absolute junk and tone/headroom/response killlers!
Just Askin'?
Gene

 

[Crikey]

It would sound tighter, more punchy and aggressive with more pick attack. Im not looking for more gain. I run the amp cranked into an attenuator hence why I am looking for the higher headroom since gain is plenty. I just want more pick attack and low end tightness.

Sounds like you just described a 2203 or a 4100 with eq in loop, without the attenuator
Imo

 

[sdn25]

Ahhh, the plot thickens! What attenuator are you using? They are CERTAINLY NOT all created equal! Most passive, resistive units are absolute junk and tone/headroom/response killlers!
Just Askin'?
Gene

Suhr reactive load

 

[sdn25]

You could try increasing the filtering.

I currently have 50+50 on the mains and screens and 32+32 on the pre amp. You suggest I increase it further from here ? If so, which ones and what values.

 

[sdn25]

if my current HT is 440v with a 320-0-325 wind PT, how much would it change to if the PT were to have a 345-0-345v wind?

 

[V-man]

I’ll play. Aside from KT88s (which made my JCM Superbass near-unbreakable regarding headroom), and higher headroom speakers like G-12 K100s, what you might want to do is slave the amp.

Is there any (appreciable) difference between a 2203/4 in the preamp section? If not (and I think not), the most successful approach should be a load box with a line out to a power amp of a proper wattage to better approximate the headroom. Another trick that could work (and I am personally against ALL MV JMP mods, but whatever) is to install a loop and run the send line to the return of another 100w FX loop-equipped amp. I believe that will bypass the power section of the JMP and the preamp section of the other amp completely.

 

[neikeel]

Simple - use it unattenuated with a pair of KT88s. There are absolutely no circumstances where you will need more clean head room
The whole point of an attenuator is to get into the crunch distortion zone.
For KT88s swap the 220k grid leaks for 100k and change the 220k bias dropper to 150k and you may need to alter the bias pot stop resistor.
Very easy. You do not need to increase the filtering
Just unhook the attenuator!

 

[sdn25]

Simple - use it unattenuated with a pair of KT88s. There are absolutely no circumstances where you will need more clean head room
The whole point of an attenuator is to get into the crunch distortion zone.
For KT88s swap the 220k grid leaks for 100k and change the 220k bias dropper to 150k and you may need to alter the bias pot stop resistor.
Very easy. You do not need to increase the filtering
Just unhook the attenuator!

Understood. I also think you didn't get what I meant, basically I use the attenuator so that I can run the amp full tilt, I tend to aim for the evh sound, when cranked the power section gets muddy whereas a 100watter stays punchy which is a result of higher headroom(do correct me if im wrong here because its what I've been told). I feel the kt88s may be too clean, I was thinking something like the kt77 is more like what I need. I like the power section being overdriven but in a 50w with el34s its too muddy whereas the kt77s are allegedly a good middle ground. Do the KT77s need any circuit changes to be installed?