1987X reissue issues......

[TheDirewolf]

Thanks a million times over, Dan. Exactly the info I was looking for.
A little more clarity is exactly what I'm shooting for. I'm also finding that, as Tone Slinger mentions in another post, there's a fine line between delivering clarity and getting enough overdrive out of the preamp. I have to say though that the tone is outstanding and the sustain and note bloom is right up there with my Fuchs TDS 100.

Thanks again for the info!

[danman]

No problem! Let us know how the fine tuning goes.

[TheDirewolf]

I spent some time yesterday tweaking the circuit. So much time that I didn't realize I was almost late for a gig. Amazing how time passes when you're sniffing solder. I didn't get to use the plexi since it was tore down and I didn't have time to put it back together. Literally had to drop everything, grab a guitar, and bolt.

I made a few changes that helped out in cleaning it up with the guitar volume. I swapped v1b cathode R to a 2K7 instead of the 1K I had. I also ditched the 2n8 bright cap on the bright volume for a 100pf. This really helped but I lost some of that gnarly mid snort. I also dropped the v1 dropping resistor to 8K2 instead of 10K. This helped tighten things up a bit. While doing so it made me realize/wonder just how important voltage numbers are. I know it all interacts with each other but I wonder does the cap values and construction material matter as much as the voltages applied to each area? I guess my question is "is the magic in the voltages or the component construction?"

I have 16/16uf on the preamp. Does the lower filtering "add" distortion too? I suppose in the end I need to decide on what kind of amp I want. A gainbanger or a general all arounder?

[danman]

I think it all matters to some degree. You can tweak the amp for weeks and still never be happy because one change always affects something else. If you change the values and voltages too much you will end up with a completely different amp in the end. i think Marshall pretty much got it right because every time I try to mod the circuit I always end up back at the original design...lol! I did change my original 1987 build to a 1986 because I prefer the bass circuit it seems. When it comes to whether the voltages or component construction matter the most, I think everything works together to create that perfect sound. Some amps just have that magic combination of the right parts and perfect voltages that end up sounding great while others only so so. You can see this in the older Marshalls where some sound better than others. A great OT doesn't hurt either! If you love the sound of the amp as it is, I wouldn't go too far with the changes. If you want more gain you could try the "one wire mod" which will put the first two preamp stages into series like the 2204 & JCM 800 series or simply mod the front end into a 2204 style.

[TheDirewolf]

So.....I spent a little more time with it yesterday and found/fixed a few minor issues I was having. Is it just me or does it take about 15-20 minutes for each little tweak to kinda settle in? Like all the components have to "get to know each other" again? I agree with you about Marshall getting it right the first time. Why else would everybody and their brother still be copying it?

I swapped the v1 dropping resistor back to 10K. When I installed the loop I had to tie in between the 10K and the 8K2 for my loop B+ but I didn't lower the 8K2 resistor to compensate the voltage consumption of the Loop. By not doing that it lowered all the voltages to the whole preamp. At first I liked it but I noticed that the effects are fighting for space in the PI with the dry signal. I'm going to change the 8K2 to a 5K6 and see if that helps. Bottom line? The amp sounds GREAT and I couldn't be happier with it. I guess at some point I have to stop tinkering and start playing!

Dan thank you so much for talking me through this process. Much appreciated!

[danman]

No problem Direwolf! Happy to help out a fellow Marshall lover!