List of JTM 45 mods you can make

slashsound · Post by **slashsound** » Thu Apr 23, 2009 7:53 pm

Hello guys, for the sake of practicality I wanted to make this thread pretty much a compendium of the best and coolest mods you can do to a JTM 45. My contribution:

1. Using EL 34 instead of KT 66 seems to sound real cool as in http://www.youtube.com/watch?v=kKFRaienxfk" onclick="window.open(this.href);return false; which is one of the best tones I have ever heard. In the beginning it sounds a little flabby on the bass...which I hate, but as the song gets near 3/4 of the way... I can clearly say this is one of the all time best sounding lead single notes I have ever heard on ANY amplifier.

Roe · Post by **Roe** » Fri Apr 24, 2009 9:32 am

dbl post

Roe · Post by **Roe** » Fri Apr 24, 2009 9:33 am

in order to use el34s - rebias and install 1k screen resistors

another mods:
- reduce v1 k to 50uf, or even 8uf
- reduce PI coupling caps to .047uf or .022uf

also reducing the v1 coupling caps to .018uf or .015uf can help controlling the bass

slashsound · Post by **slashsound** » Fri Apr 24, 2009 5:07 pm

Roe wrote:dbl post

Can you please link the original post you are referring to ? Thanks bro.

Roe · Post by **Roe** » Fri Apr 24, 2009 5:59 pm

the original post was just like the second post in this tread

slashsound · Post by **slashsound** » Fri Apr 24, 2009 6:50 pm

Roe wrote:the original post was just like the second post in this tread

LOL ok, im sorry, i thought you meant that this type of thread already exists.

Coot Boy · Post by **Coot Boy** » Fri Apr 24, 2009 8:26 pm

If you want to make that 45 into something else, something I have done recently and just love, check out here, the specs are on page 2.
http://forum.metroamp.com/viewtopic.php ... &sk=t&sd=a

billstets · Post by **billstets** » Tue Apr 28, 2009 5:14 pm

Roe wrote:in order to use el34s - rebias and install 1k screen resistors

another mods:
- reduce v1 k to 50uf, or even 8uf
- reduce PI coupling caps to .047uf or .022uf

also reducing the v1 coupling caps to .018uf or .015uf can help controlling the bass

The only thing I've done to reduce my bass is change my V1a to 10uf. The thing I always question about these bass controlling techniques is do you lose some sound quality in mids and highs? Will the mids and highs get thinner if you tighten the bass?

Roe · Post by **Roe** » Tue Apr 28, 2009 6:02 pm

billstets wrote:
Roe wrote:in order to use el34s - rebias and install 1k screen resistors

another mods:
- reduce v1 k to 50uf, or even 8uf
- reduce PI coupling caps to .047uf or .022uf

also reducing the v1 coupling caps to .018uf or .015uf can help controlling the bass
The only thing I've done to reduce my bass is change my V1a to 10uf. The thing I always question about these bass controlling techniques is do you lose some sound quality in mids and highs? Will the mids and highs get thinner if you tighten the bass?

yes, reducing the v1 k alot will kill the woman tone. 10uf is to low IMHO. but reducing the coupling caps only takes away low bass - it doesn't take away gain and fatness in the same way

billstets · Post by **billstets** » Wed Apr 29, 2009 11:39 am

Roe wrote: yes, reducing the v1 k alot will kill the woman tone. 10uf is to low IMHO. but reducing the coupling caps only takes away low bass - it doesn't take away gain and fatness in the same way

Does 50uf kill the woman tone?

Roe · Post by **Roe** » Wed Apr 29, 2009 11:52 am

I'n my 45 with the RS I can bet a fairly good woman tone with a 50uf NOS iskra cap

neikeel · Post by **neikeel** » Fri May 01, 2009 1:47 pm

Try reading this it goes over different mods for RIs but is relevant to normal 45s

http://raw-sewage.net/jtm45ri_mods.html

slashsound · Post by **slashsound** » Fri May 08, 2009 3:40 pm

Come on guys, lets get a few more mods on this list

bulatovic · Post by **bulatovic** » Fri May 08, 2009 4:10 pm

- Steve's Zero Loss Effect Loop

- Lar/Mar PPIMV

- SS rectification

- Rising voltage by reducing the 8K2 resistor

- EL34s (screen resistor to 1K from 470R)

- 56k/250pf - 47k/340pf - 33k/500pf tone stack switch (SDM's site)

- 0.1 - 0.047 - 0.022uf PI coupling cap switch (the same principle as tone stack switch)

- 100pf PI cap instead of 47pf

- 0.15 - 0.18uf preamp coupling caps

- higher value capacitors for mains, screen, PI, preamp filtering

- lower value capacitor for the V1 bypass cap

- Split / shared V1 cathode switch (SDM's site)

- .68uf V2 cathode bypass cap

- Different bright cap values (up to 5600pf)

(or just about anything that would work and you might like, or transform it from JTM45 with KT66 to say 2204 or above...)

slashsound · Post by **slashsound** » Thu Dec 24, 2009 7:39 pm

Are there any other mods you guys can come up with? Like is there a way to make a jtm 45 sound like a 68 plexi or even a 2203 or 2204 ?

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List of JTM 45 mods you can make

List of JTM 45 mods you can make

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