50 watt Questions!

[motrock]

Hey guys, I am having a friend work on my 50watt Plexi clone. We are cleaning up a few things and upgrading some parts. First thing we are going to do is at a Bright Cap. There is no Bright Cap in my amp. If I wanted to turn the amp down and use a Les Paul for some other tones, it gets super dark. Don't know why there was not a Bright Cap originally put in it. I am going to assume that you guys have Bright Caps in your amps?

Second thing, we are going to install the new SoZo NextGen Caps. Right now there are; what I was told, Xeon or Xion? Can't remember the exact name of the caps. Gonna upgrade anyway. What do you guys think about that?

Now, here is the mystery for my friend and I. I took a look at 2 different 12 Series specs. There is a resistor leading to a preamp tube that we don't know what its purpose is. My friend had a couple of ideas. But we just don't know. Here is a pic of the resistor. What is it for?

http://i63.photobucket.com/albums/h147/ ... sistor.jpg" onclick="window.open(this.href);return false;

Anyway, just trying to wake this amp up.

[neikeel]

It is a series dropper to the input grid of the PI tube, not seen one before,may have been to prevent oscillation, ?

I use a bright cap on my builds, a 5000pF is stock on a 68 plexi lead amp but you may lose some of your lower volume cleans and gain some hiss, guess it depends on how loud you play and whether hiss bothers you.

Amp could do with a tidy up. You will find that mustards (and the new Sozos are supposed to be just like mustards) are a bit smoother than the polybox caps in there now.

Do you have more pics? What OT does it use?

[motrock]

It is a series dropper to the input grid of the PI tube, not seen one before,may have been to prevent oscillation, ?

I use a bright cap on my builds, a 5000pF is stock on a 68 plexi lead amp but you may lose some of your lower volume cleans and gain some hiss, guess it depends on how loud you play and whether hiss bothers you.

Amp could do with a tidy up. You will find that mustards (and the new Sozos are supposed to be just like mustards) are a bit smoother than the polybox caps in there now.

Do you have more pics? What OT does it use?

This amp is actually a Blankenship VariPlex. Or it used to be. Its been converted to Plexi Spec. The OT is a Mercury Magnetics and says Blankenship on it.

I will upload more pics later on today!

The hiss doesn't bother me. I just want that harmonic content that you hear in the classic VH stuff. I don't play clean with this amp anyway.

The other important part is that I want to be able to turn things down and retain highs. I have a WCR Les Paul, and would like to be able to play other things like AC/DC, early Scorpions, Zep, etc. As of right now; when I turn down Volume 1 to 6-7 on the dial, it gets dark and looses brightness. I want this thing to able to get more then just VH. Gotta have that bright cap!

My friend thats going to work on this thing will do some tweaking to get it just right.

[neikeel]

This amp is actually a Blankenship VariPlex. Or it used to be. Its been converted to Plexi Spec. The OT is a Mercury Magnetics and says Blankenship on it.
The hiss doesn't bother me. I just want that harmonic content that you hear in the classic VH stuff. I don't play clean with this amp anyway.
The other important part is that I want to be able to turn things down and retain highs. I have a WCR Les Paul, and would like to be able to play other things like AC/DC, early Scorpions, Zep, etc. As of right now; when I turn down Volume 1 to 6-7 on the dial, it gets dark and looses brightness. I want this thing to able to get more then just VH. Gotta have that bright cap!
My friend thats going to work on this thing will do some tweaking to get it just right.

The soldering is a bit 'splatty'' - maybe whoever did the modding? Personally I find the MM OT a bit stiff and that the Marstran in my 2 in 1 is pretty hard to beat (although I do hear good things about Classic Tone and ****** for different reasons). I guess you see how far you can get with tweaking before an OT swap .
Your friend may need to tweak; a 5000pF stock cap is beyond the value of a pure bright cap it is more of a 'bring the gain in earlier on the volume dial' cap. A 100pF gives a little extra something that no cap at all lacks. I find a 500pF cap a bit spiky but a 1000pF (like the MV amps) can work well depending on your overall set up.
Please let us know your results

[motrock]

Thanks man! Yeah, I have been considering the OT swap. That might be where some of my stiffness is coming from!

This thing will be like a new amp when I get done with it.

[rgorke]

I have heard pretty good VH tones with the Variplex. Maybe put it back to it "stock" configuration, if you know what that is.

Neil's advice is, as always, spot on. For the VH stuff, I have a mixture of mustards and the chicklet caps. I found the mustards a bit too smooth for VH for bypass caps. But in other locations, they are perfect.

My understanding (and could be incorrect) is that the new Next Gen Sozo caps are not like mustards at all. They are for more high gain applications. There existing caps are the mustard-esque. But I'll let people who actually know something about that chime in.

[motrock]

I have heard pretty good VH tones with the Variplex. Maybe put it back to it "stock" configuration, if you know what that is.

Neil's advice is, as always, spot on. For the VH stuff, I have a mixture of mustards and the chicklet caps. I found the mustards a bit too smooth for VH for bypass caps. But in other locations, they are perfect.

My understanding (and could be incorrect) is that the new Next Gen Sozo caps are not like mustards at all. They are for more high gain applications. There existing caps are the mustard-esque. But I'll let people who actually know something about that chime in.

Really? Thats the first time I have heard someone talk about nextgen Sozo not like the mustards. I have some coming for my 2203 project. Hopefully they sound good for it! George would know, since he has tried them out!

I don't know; maybe all I need is the bright cap.

An OT swap seems more likely also. Might just leave the caps alone. Except; there is this big black cap that is still unidentified. The writing is under the damn thing and only way to find out is by yankin it. Its supposed to be the .68uF. My other amp was a cap that looked just like it; and it could be a 330uF. Which would kill what I want with the mids!

[rgorke]

I have heard pretty good VH tones with the Variplex. Maybe put it back to it "stock" configuration, if you know what that is.

Neil's advice is, as always, spot on. For the VH stuff, I have a mixture of mustards and the chicklet caps. I found the mustards a bit too smooth for VH for bypass caps. But in other locations, they are perfect.

My understanding (and could be incorrect) is that the new Next Gen Sozo caps are not like mustards at all. They are for more high gain applications. There existing caps are the mustard-esque. But I'll let people who actually know something about that chime in.

Really? Thats the first time I have heard someone talk about nextgen Sozo not like the mustards. I have some coming for my 2203 project. Hopefully they sound good for it! George would know, since he has tried them out!

I don't know; maybe all I need is the bright cap.

An OT swap seems more likely also. Might just leave the caps alone. Except; there is this big black cap that is still unidentified. The writing is under the damn thing and only way to find out is by yankin it. Its supposed to be the .68uF. My other amp was a cap that looked just like it; and it could be a 330uF. Which would kill what I want with the mids!

I probably misunderstood the high gain application. To me, high gain does not necessarily mean smooth but May.be that is why they are they are so good.

[motrock]

Well, I there are 2 things that my friend suggested to do; according to Friedmans Specs on this thread:

http://forum.metroamp.com/viewtopic.php ... &start=870" onclick="window.open(this.href);return false;

100k NFB resistor at 4 ohm tap
560pf lemco treble cap

I am going to start there and then see where I end up. That may absolutely nail it.

Then there is this issue of the big black cap.

http://i63.photobucket.com/albums/h147/ ... Board1.jpg" onclick="window.open(this.href);return false;

Not sure if its a 330uF or 68uF. 330uF would kill the mids. 68uF; according to the 68 12000 schematic I have, is what needs to be there!

[jnew]

I use 50 watters pretty much exclusively. Even my 100 watter only uses two tubes and screams VH all day. And I have 100K in the NFB loop. (just works wonderfully for my set up) I would not go so far as to say the 330uF across the 820 ohm on V2, kills the mids. (yep, I use that too) It adds lows giving full bodied warmth and maybe a scooping effect but I highly doubt you will miss the mids. Keep us posted.

[motrock]

I use 50 watters pretty much exclusively. Even my 100 watter only uses two tubes and screams VH all day. And I have 100K in the NFB loop. (just works wonderfully for my set up) I would not go so far as to say the 330uF across the 820 ohm on V2, kills the mids. (yep, I use that too) It adds lows giving full bodied warmth and maybe a scooping effect but I highly doubt you will miss the mids. Keep us posted.

Cool man! I think 50watters are awesome; especially with a variac down to 90volts. Its still loud; but I don't use attenuation often.

You know, I was wondering that with the 330uF. And yeah, the 100k in the NFB loop is something this amp does not have; or a bright cap. Those 2 things will liven the amp up.

What kind of caps are you using in your 50watters? What do you like?

[jnew]

One has Sozo's and the other has regular Mallory 150's except the .68 across the 2.7K on V1. Just happened across a vintage WIMA .68 and threw in in that spot to try. Glad I did. It added clarity. You can hear the amp with the Mallory's in the signature link on the bottom of this post. It's using all the specs you talked about, plus a 4700 bright cap on CH. I. Your amp will need that for sure. Or 5000, 5600, any will do but is definitely needed.

[fhn_lopes]

dumb question but if you LP feels dark at times, have you tried a treble bleed cap in her? It works nice sometimes... I don't use it anymore though as I don't have this problem in my amp, but before I had this marshall, all my guitars were equiped with treble bleed caps/resistors and that worked out nice.

[motrock]

One has Sozo's and the other has regular Mallory 150's except the .68 across the 2.7K on V1. Just happened across a vintage WIMA .68 and threw in in that spot to try. Glad I did. It added clarity. You can hear the amp with the Mallory's in the signature link on the bottom of this post. It's using all the specs you talked about, plus a 4700 bright cap on CH. I. Your amp will need that for sure. Or 5000, 5600, any will do but is definitely needed.

Well, I think I do want to throw a .68 in there for sure. Have you tried a SoZo .68?

Yeah, the amp needs a bright cap for sure!

[motrock]

dumb question but if you LP feels dark at times, have you tried a treble bleed cap in her? It works nice sometimes... I don't use it anymore though as I don't have this problem in my amp, but before I had this marshall, all my guitars were equiped with treble bleed caps/resistors and that worked out nice.

LP doesn't feel dark. The amp does. Doesn't matter what guitar I plug in to it. LP, Franky, PV Wolfgang, Strat, etc.