Did the JCM800 tone stack and cap mod to SL+ module...

Well, I finally did the JCM800 tone stack mod to my silverface SL+ module. I changed R31 to this:

http://www.mojomusicalsupply.com/item.asp?pid=85926&pg=45001&id=7294333

C14 to this:

http://www.mojomusicalsupply.com/item.asp?pid=96053&pg=44974&id=5168225

While I was at it, I also did the cap mod. I first changed C3 from a .0047u to this:

http://www.mojomusicalsupply.com/item.asp?pid=17611&pg=44974&id=5165002

Then I converted C3 to this:

http://www.mojomusicalsupply.com/item.asp?pid=17610&pg=44974&id=5165001

Here is what the module ended up looking like after the mods:

Tone difference: wow, I've gone from not really caring for the SL+ to absolutely loving it! I really can't believe the difference that 3 part changes made.....it's almost like a new module. From the factory, the module has a muffled, sloshy/loose character IMO. It was okay for leads, but terrible for rhythm. Now there are nice cutting mids and palm mutes sound nice and tight. Overall, a very articulate sound. It seems there might be a touch less gain on tap, but I'm guessing the sloshyness of the factory module made it just *seem* like there was more gain.

Regarding the cap mods, I didn't listen to the module with the factory .0047u cap and tone stack mod. I went straight to the tone stack mod, then the cap mods. I felt the .0022 tightened things up decently, but I wanted to try the .001u as well. It tightened the module up even more and I am still able to get decent bass by playing with the bass tone control and the resonance control on my RM50B combo. I'm now wondering if I should try the .001u on some of my other modules.

I like my Plexi better with the .001u cap mod...I appear to be in the minority, though, as most folks are happy with it stock.

Generally, I think all the Randall modules have too much low end stock...haven't heard the Egnaters.

Wow, that's a rather drastic cap value change for a Plexi considering they have a higher value cap (.022u) in C3 than most modules. Did you try other values before arriving at the .001u......like .015u, .010u, .0047u, etc? I'm actually quite happy with my Plexi module in stock form.

I wouldn't recommend anything lower than.022 on the XTC mod. While I loved the change on the SL+ , the XTC sounded way too weak.

You mean .0022, right?

Chad said:

You mean .0022, right?

Click to expand...

Correct

No problem......all of those micro cap sizes get confusing to keep track of.

i was wondering if anyone had any samples of this mod...

i'd love to try it, but i want to hear what it sounds like before i make the change

Just did the same conversion of my SL+ to the JCM800 tonestack..
Well I didn't have a 33k resistor but used a 38k instead for now.

What I can say is that as Chad already mentioned, cutting mids is much better, and the module get's more usefull.

I already did the cap mod before this, think I used a 0033 or 0022..
What I do know is that a 001 does not work well at all with the SL+..

Glad to hear all worked out okay. I still much prefer the .001u....I was just playing through my SL+ module about an hour ago and was admiring the bass clarity and thinking about how the .001u increased clarity while still leaving adequate thump in there.

Of course, what works for one person doesn't always work for everybody. The key is finding what works best for you (sounds like you did).

It was clearly a fall forward for the SL+ module, I probably put the 33k in as soon as possible..

Also thinking on changing the V1 tube(the one in the amp not module) to one with less distortion...

I think the amp right now could work better with another tube there..
Maybe a Tung Sol 12AX7.. If I find one to try with..

Tung Sol in V1 is a great choice.

Is it true that Tung Sol 12ax7 has more gain than EH?

The way I understand it (I could be wrong), if 12AX7 tubes are to spec, then their gain should be the same. The problem is that tolerance variances are all over the place.....some brands/models worse than others.

Some 12AX7's work better in high gain circuits, but that doesn't necessarily mean they are higher gain themselves.

If you are looking for higher gain 12AX7's, then look for a vendor that measures gain and will sell you some that are higher than normal spec.

The Bass Boost switch on the Egnater Dual Sound modules actually selects three different capacitors for you. No mods needed.

Chad said:

The way I understand it (I could be wrong), if 12AX7 tubes are to spec, then their gain should be the same. .

Click to expand...

From what I've read on the various tube sites, some tubes are said to have more gain than others. For instance Chinese tubes are said to have the highest gain available and some of the cheaper Sovtec tubes are said to have lower gain. Many of the internet tube dealers have charts were they rate tubes for their gain (and other things like harmonics and microphonics)

I know you can pay a couple of extra dollars to have tubes selected with high gain, but do some brands run in the higher end of the tolerance than others?

MetalMajik said:

Chad said:

The way I understand it (I could be wrong), if 12AX7 tubes are to spec, then their gain should be the same. .

Click to expand...

From what I've read on the various tube sites, some tubes are said to have more gain than others. For instance Chinese tubes are said to have the highest gain available and some of the cheaper Sovtec tubes are said to have lower gain. Many of the internet tube dealers have charts were they rate tubes for their gain (and other things like harmonics and microphonics)

I know you can pay a couple of extra dollars to have tubes selected with high gain, but do some brands run in the higher end of the tolerance than others?

Click to expand...

I think this link may help explain things better:

http://www.guitaramplifierblueprinting.com/12ax7.html

About the Tung Sol 12AX7...

After lifting this question to some amp builders they all agred on that it sounds great, however some had problems with realiabilty of them..

What they keep on coming back to is to get some NOS Mullard..

here's another place to read about 12AX7 and other tubes..

http://www.thetubestore.com/12ax7review.html

chad, i love how you laid out the details of that mod with the pic and everything. if you do anymore mods please show them like that again. thanks alot , super good info on that, we need more stuff like this on here.