Getting More "Focused" Low Notes in my plexi...

[wavey63]

So I am really happy with my amp now that I have the channels jumpered and my standby strata set up with a humbucker...a Duncan '59... I just need some direction on getting a slightly tighter low note tone. When a do power chords on the low frets I get a slight loosened on the notes. Should I tweak the amp ...if so where Do I start? Or would an eq pedal do the trick?

[bulatovic]

I guess that this might help: http://forum.metroamp.com/viewtopic.php ... 7&p=283746" onclick="window.open(this.href);return false;

What i guess you'd need is to beef up the filtering - i guess you did the stock 2x 50+50uf can caps and a dual 32uf on the board? You could put 50+50uf for preamp instead of that stock 32+32uf. Also i've heard that reducing the V1A bypass cap from 330 (or 220uf) to something around 50uf or even as low as 5uf would make the amp feel tighter especially in the lower freq. range. I'm not a big fan of 0.0022uf on bright channel V1 coupling cap, i find it too thin and brittle - so i'd stick with 0.022uf instead.
Lower negative feedback resistor value (27k instead of 47k) should also tighten it up a bit as well but it would make the amp cleaner as well - correct me if i'm wrong here...

Oh - and, what sort of speakers are you using? That might have something to it...

[wavey63]

Any idea where to buy the 50x50uf cap? Or could I just use 2 separate ones? I think that may be good. I am using eminence speakers now..I used deletions but wasn't happy with the vintage 30... cone cry. I may try some warehouse speakers. Any suggestions?

[trevorus]

I got my dual 50uF cap cans from Ted Weber, and I also use the WGS Speakers in my Plexi combo. A Reaper (G12H30 clone) and a Green Beret (Greenback). they sound phenomenal. When I first got them, I thought they were a bit too tight/nasty/middy, but I went through a little break-in work, and they settled in to a delicious sweet tone. I won't pay the Celestion prices, especially since a lot of the production is now outsourced to China. That, and a Vintage 30 failed me (the magnet's center pole moved, trapping the VC).

[wavey63]

I have a pair of early 80's Greenbacks that I am afraid to use. Don't want to blow them. How loud do you use your amp? I want enough power without ruining anything.

[trevorus]

I've dimed my amp, and it's only going through 2-12's, and one is 25 watt rated, the other is 30. I don't dime it very often (no need playing at church and at practices), and the speakers do fine.

[arledgsc]

I believe in another post I suggested you change the NFB resistor to 100k to open up the amp. In doing so the bass will get looser. You may have to increase NFB (lower NFB resistor value) to tighten it up a little. So how was the bass before you changed to NFB resistor to 100K? I run 100K in my 50W but like 68K in the JTM50.

If increasing the cap values doesn't give the bass tightness you need try backing off the NFB resistor value to see if you can find a happy medium. Scot

[bulatovic]

I wouldn't worry too much about ruining Greenbacks, but i wouldn't run the amp on 10 all the time to be honest... I'm about to do a 50w with G12M 25w reissue Celestions, they should hold up nicely - there are a lot of manufacturers putting 2 Greenbacks into 50w combo amps and 4 greenbacks into a 4x12 box with a 100w amp so... - there are even George's clips of 100w amp with 100 or 120w box - running on 10 (i think i remember right)

Yeh - lowering the resistor value means increasing the negative feedback and will make the amp feel tighter and less gainy - so give 27k resistor a try instead of 47k you have there - or connect the existing 47k from 8ohm tap to a 16ohm tap - see if you like that. Also try to lower the V1 bypass cap to about 100 or 50uf - that might help - those are easy mods, worth trying...

[wavey63]

Thanks arledgsc. Idid get your previous posts am just trying to plan out what to change on the amp before I start changing everything.i do ask tons of questions. I am just like that! heheh I have to say that the 100k nfb res aon the 8ohm tap got me real close to what I am looking for in tone and gain. I just want to tighten up the looseness and get a bit more "hair" to the notes. I do have to say though even now this amp is one of if not THE best sounding amps I have ever played though. I thank George every time I play it that he made an impossible amp to get, possible to get...i.e affordable.

[Arclight]

Have you tried different power tubes? The difference is dramatic. Granted Mullard xf2's are very costly-$275+ for actual NEW Old Stock tubes-but for around 90-100 dollars a pair of RFT's (aka "Siemens"-typically lableled 6CA7 National Electric in red letters) EL34's absolutely transform the amp.

The RFT's aren't nearly as "full" as the Mullards and to my ears lack some mids-but compared to Winged C's or the supplied JJ's you WILL gain across the board. The "Mullard" reissue is woefully inadequate and only shares the name and not the tone. You might also want to give the 6CA7 American made "Fat Bottles" a try-still costly but was the secret to EVH's tone.

[Roe]

don't jump channels. if you do, decrease cathode resistor on the dark ch to .68

[Mars Hall]

A larger choke will also tighten up the low end. I have a RS 20H from Marstran in my jtm45 build.