Getting a little more balls out of a 1987

[SteadyEddie]

I finished my 50 watt clone a while ago. Started tweaking. Lowered preamp filtering to 2x16uf, screens, PI, 16 uf, and mains 32 uf. I can't hear any ghosting, so I guess it's all right. Amp FEELS more natural now, my point of reference was my old Super Reverb and it played like a charm.
I've also changed tone stack to 56k/250. I don't have the .005 cap on the volume, my volume is always dimed anyway.

I've got the Lar/Mar PPIMV in there. it sounds great. I see myself playing with the volume at about 50 to 60 percent with the gigs/jam volumes I'm used to.

The amp sounds great for rhythm, nice complex crunch with beautiful harmonics. Real nice.
But for leads, I'd like a bit more fluidity, a bit more sustain ... just a bit. The easy solution would be to get a tube screamer and stick it in front but I'm trying to avoid pedals.
The other solution would be to crank the master to get that poweramp compression going on. Can't really do that without pissing off the band. I like the dynamics of an amp that can "breathe" anyway. Just want the compression to affect the high notes.

I briefly tried the one-wire mod. Turning up my bright channel volume made it oscillate. So I brought both volumes up, and it seemed a little to dark and hairy. I reduced the 330uf bypass cap on v1a to 5uf and added a 500pf bypass cap on that channels 470k resistor. Still, not quite thrilled with the tone. I also increased the feedback resistor to 100k.

I am somewhat interested in the 2203 mod, is it much more complex than the one-wire mod? Or is there more that can be done to the one-wire mod to make it more tonally pleasing?

Optimally, I'd like to keep the amp "plexi" but just squeeze that extra bit of good ness out of it.

[54strat]

Do you have a .68 bypass cap on V-2? I have a 1987 I converted to 1986, but lowered the V-1 bypass to 5uF as you did, then put my .68 mustard back on V-2 for a little more gain and upper mid punch.

[OdgeUK]

I have a similar setup. A '73 1987 head which I put a PPIMV in. It's the scnizzle for Hard Rock rhythm (which is what I play mostly anyway) but it's a little too stiff and unforgiving for a sustaining lead sound. I bought a Bad Monkey pedal for £36.00 and have been experimenting with lowering the Pre-Amp volume from 10 to about 8, upping the master a little more and using the Bad Monkey for lead or for post 70's rhythm sounds (then I use a MXR MicroAmp to get a lead on top of that). Just experimenting with this setup at the moment but it seems to work well without really losing the character of the natural amp overdrive.

[arledgsc]

Try lowering the NFB (increasing the NFB resistor). This easy mod will open up the amp and add more gain. If running 47K NFB resistor try 68K or even 100K ohm. The cojone factor jumps up with lower NFB.

Bass can get loser with lower NFB so watch out for that. I run 68K/8 ohm tap in my JTM45 and JTM50 and love it. Scott

[PCollen]

You have split cathodes, right ? Here are my comments/suggestions

The 500p bypass cap belongs ONLY across the bright channel mixer resistor, not on the normal channel and certainly not on BOTH. Increasing mixer resistors to 470K will add a little more drive to both channels.


You can get a gain boost for BOTH channels by changing the V2a plate resistor from 100K to 150K..I wouldn't go any higher. Also you can bypass the V2a cathode resistor (820) with a 40uF cap for some extra gain for both channels.

I'd recommend changing the V1a Rk/Ck to 1.5K/22-25uF.

Change the NFB to 47K and put it on the 8 ohm tap.

[SteadyEddie]

You have split cathodes, right ? Here are my comments/suggestions

The 500p bypass cap belongs ONLY across the bright channel mixer resistor, not on the normal channel and certainly not on BOTH. Increasing mixer resistors to 470K will add a little more drive to both channels.


You can get a gain boost for BOTH channels by changing the V2a plate resistor from 100K to 150K..I wouldn't go any higher. Also you can bypass the V2a cathode resistor (820) with a 40uF cap for some extra gain for both channels.

I'd recommend changing the V1a Rk/Ck to 1.5K/22-25uF.

Change the NFB to 47K and put it on the 8 ohm tap.

Thanks, PCollen. I'll try the plate resistor thing. I knew increasing the plate resistance increased gain, but I didn't know how high I could go before the sound would degrade.
I tried bypassing the V2a resistor with a 22uf cap, didn't care for it. I like that upper mid bite. But I think I'll change the 2.7k resistor on V1b to 820 ohm, I think that was a standard value, and try like a 2.2uf bypass cap. I haven't calculated the frequency, but it should still have some Marshally upper mid, from what I'm thinking.

[neikeel]

http://home.comcast.net/%7Ejbjdav26/195 ... 20grnd.jpg

Best of both worlds

If you want to try without ripping it apart use this version:

http://home.comcast.net/%7Ejbjdav26/195 ... %20alt.pdf

Obviously you only do the preamp/push-pull bits. No drilling, no tearing it apart and you get a 2204 and a 1987 and only lose the hi vol II input where you put the gain pot.

The pre-mv works in both modes, just crank it to get pure 1987 tones (you can calm this volume down with a PPIMV if you want).

[SteadyEddie]

Okay, I've got it sounding super sweet right now.
I'd been away from the amp for a week so I got to listen to it again with fresh ears.
I've got the "grease," that bit of compression on the high notes. I think the biggest factor was going from the 2.7k to the 820ohm on the cathode of v1b.
Another "grease" mod was upping the presence cap to .68. This gives the effect of lowering NFB on highs and mids, but keeps the bottom end tight. I might try a .47 to narrow it a little bit more.
I had changed the 500pf tone stack cap to 330 pf but went back to 500pf, that gave back a little bit of gain. I went back to 47k NFB, it's nice and tight on the bottom end. At 100K, I lost that "bell-like" bottom end, it sounded "dry" and didn't clean up well with the volume knob at all.
I also had some KT66s in my Super Reverb, so I popped them in and biased them. I didn't need to change the resistor to get into the bias range, as I thought I might. I set the impedance selector down one click. I haven't changed the screen resistors, I understand that's kind of optional. Someone please advise me if it's something I really should do. These tubes have a "prettier" sound than the EL34's. Nice, big bottom (like J-Lo) with these sparkly sweet highs.
I didn't really want to add extra gain stages (although that 1959/2203 layout looks VERY interesting) at this point, just get it to where it "plays easy"
I think a good amp can play easy without a lot of gain. Right now it's perfect for classic rock/blues rock, I can cop AC/DC, Free, Bad Co., Zeppelin, Thin Lizzy, ZZ Top, Aerosmith, etc... turn down the volume knob and I can get a nice Black Crowes sound. No pedals, just straight into amp.
Thanks everyone for your help and advice.

[SeaTea1967]

Wow. That post took me back to the days when I built my first preamp and tried just about everything over the course of a year before I had it dialed in the way I wanted. Frustrating but so satisfying when you get it where you want it finally, isn't it?

I built two identical amps back then, but one never sounded as good as the other, so it sat on the shelf for 10 years until I decided this Summer to install a Marshall 2204 preamp into it (no mods at all). Sounds amazing, so I'm just going to leave it and not tinker.

Right now it's perfect for classic rock/blues rock, I can cop AC/DC, Free, Bad Co., Zeppelin, Thin Lizzy, ZZ Top, Aerosmith, etc... turn down the volume knob and I can get a nice Black Crowes sound. No pedals, just straight into amp.
Thanks everyone for your help and advice.

This is where you post some sound clips for everyone to enjoy. Would LOVE to hear how things turned out!

[SteadyEddie]

That's gonna be my next step, recording some clips.
I should add that I changed the 500pf cap over the 470k mixer resistor to approximately 880pf.
Now the notes fly off of the fingerboard. It changed the highpass filter frequency from approx. 7k to 4k. It seems to let more of the "character" of your guitar and pickups through. Still sounds like a plexi, but it's easier to play.

[SteadyEddie]

This is where you post some sound clips for everyone to enjoy. Would LOVE to hear how things turned out!

Here's a video clip, I used my iphone as a camcorder and the sound level is really low (The Lar/Mar PPIMV is FANTASTIC. IMO, this sounds just as good or better than my Weber MASS attenuator.)

I'm going into a Marshall 1965a 4x10 cabinet. Perfect size cabinet, sounds great (Jose Arredondo said the Celestion G10L-35 was the best sounding 10" speaker) and it's portable. I had to get Sour Mash cabinets build me a custom small head cabinet to fit on the speaker cab.

This just gives you an idea of the sounds I can get. I'm not into high gain but I get some seriously good blues to hard rock tones out of this. It's fun to play even at low low volumes.

Excuse the sloppy noodling. I'm just trying to demonstrate the sounds I get. I can get "almost clean" on the neck pickup, turn it up and it's a nice woody solo blues-rock sound. The bridge humbucker is a bit more growly. I can get some good sounds with the volume about halfway for some rootsy stuff, or turn it up for full rock roar.

The amp is quite a bit more dynamic and aggressive when the speakers are moving some air and the power tubes are chugging.

Take this video for what it is, I hope you enjoy....

http://www.youtube.com/watch?v=jCzmCxBow14" onclick="window.open(this.href);return false;