JTM45 Build

Littlewyan · Post by **Littlewyan** » Wed Aug 19, 2015 7:49 pm

Ah yes the 5000pF Bright Cap that turns your volume control into an on/off switch! I found on my old 1987xl that 500pF was a good value for me if I kept all tone controls at 5 and had the volume at 8.

pdf64 · Post by **pdf64** » Wed Aug 19, 2015 9:37 pm

Yes, with my LP I tend to use 470pF on the lead channel, 220pF on the rhythm, a simple external AB box selects which is active. Twist the switches down a notch to halve those values for use with the Strat.

Littlewyan · Post by **Littlewyan** » Sun Aug 23, 2015 6:29 pm

Well I fitted the PPIMV. Not overly impressed. It does get the amp down to bedroom level but the tone gets very fizzy. I think I'll keep it just for those occasions when I need to drop the volume just a tiny bit more.

I think I'm going to go for the split cathode with the 33k/500pf tonestack. I'm not going all the way to 68 spec and lowering the coupling cap to .0022uF and adding a .68uF Cathode Bypass to V2 just yet. I know that with the .68uF Cathode Bypass Cap it makes it harder for the amp to clean up.

I thought about trying a Solid State Plug in for the rectifier but the HT is already at 460-470VDC so I think it'll be way too high with the solid state plug in. Mains and Screens Filter Cap is rated at 500VDC.

joeboo88 · Post by **joeboo88** » Mon Aug 24, 2015 5:57 pm

Hey Ryan. I also did a PPMIV and didn't like it. I did the spilt cathode, but I didn't have a .68uf cap, so I used a 1uf/2k7 cap and resitor. I didn't alter the tonestack. Should I have to get the benefit? I found it brighter but I didn't get anymore oomph out of the amp. Plus my fuzz face didn't sound good with this mod, so I put everything back to stock.....and will probably accept that this amp just won't have the balls I want......oh well ,stock it sounds great, I'll just use a pedal in front of it......Joe.
Let us know how you make out.

Littlewyan · Post by **Littlewyan** » Mon Aug 24, 2015 7:14 pm

Changing to split cathode will just simply make the amp brighter. Changing the tonestack to the later 33k/500pF will give you slightly more gain. If you want more balls move the feedback loop onto the 8ohm tap. If it still hasn't got enough for you then change the feedback resistor from 27k to 47k. If you do give the amp more gain you'll probably want to increase the filtering in the preamp and PI but see how you get on first.

joeboo88 · Post by **joeboo88** » Mon Aug 24, 2015 11:32 pm

Thanks Ryan. I will try tomorrow and let you know, luckily there is an electronics store in town, I need some 33k anyways....they have Good assortment of resistors, but a crappy selection of capacitors. Go figure

Littlewyan · Post by **Littlewyan** » Tue Aug 25, 2015 4:22 pm

Think yourself lucky. I have no electronics shops near me. Have to order everything online

.

joeboo88 · Post by **joeboo88** » Tue Aug 25, 2015 9:18 pm

Hey Ryan. I tried the tonestack mod and didn't like it. Bass sounded flubby.
I put in the 47k and 8ohm, and will try it later, family is over so no cranking.

Littlewyan · Post by **Littlewyan** » Tue Aug 25, 2015 9:24 pm

Did you try it with the split cathode though?

joeboo88 · Post by **joeboo88** » Tue Aug 25, 2015 11:40 pm

No I didn't and after I put it back I remembered that the .68 cap makes it brighter.... I don't have a .68 ,I have a 1 uf and a .47 only. Which would be better?
I could try the split cathode and the .68/2k7 and see

Littlewyan · Post by **Littlewyan** » Wed Aug 26, 2015 5:13 am

Yeah I think you need to do the split cathode and 33k/500pf tonestack together. I'd try 1uf. 68 spec amps used a 820R resistor for the .68uf side and later amps used 2.7K.

Reeltarded · Post by **Reeltarded** » Sat Sep 05, 2015 5:30 am

ArrogantOwl wrote:
JazzGuitarGimp wrote:Reel, did you get yourself another amp garage account?
Nope. I am not Reel. I do lurk a lot though.

Can find me on TGP under the same tag.

Don't sweat him. He's been an asshole since he asked to see an amp I sold in a package deal to someone else and he never mentioned intrest in the amp, just seeing it, so, it's him.

JazzGuitarGimp · Post by **JazzGuitarGimp** » Sat Sep 05, 2015 11:58 am

Just for the record, reel is referring to me, not angryowl. That is, unless reel has screwed more than just me out of an amp. This happened a few years, in private discussions between reel and I, and I saw no reason to air this shit in public - but apparently reel doesn't have a problem with that. That's all I'm going to say on the subject, and I apologize for the thread derail.

Reeltarded · Post by **Reeltarded** » Sat Sep 05, 2015 1:43 pm

Screwed you out of MY amp.

So funny. We never had anything out anywhere. It was all apology from me for not being a mind reader, you fucking asshole.

It was a great time for me having just lost my dad and then my best friend and there you are a fuckhole.

Post by **HeeBGB** » Sun Sep 06, 2015 2:49 am

OK well Reel and JazzGuitarGimp wont be down for breakfast for at least a couple of days to cool off.

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