TT-JC18 Add gain stage ?

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Tomten
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TT-JC18 Add gain stage ?

Post by Tomten »

Hi

I recently thought I would buy the PX18 kit from Tube Town, but I would want to add a gain stage to it, adding a 4th 12AX7 tube, would it be possible ? If that's possible to do I will buy this kit and it will be the second amp I build in total.

https://media.tubetown.net/cms/userfile ... layout.pdf

Thanks guys...
Last edited by Tomten on Wed 06/26/24 11:07 am, edited 1 time in total.
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Re: TT-PX18 Add gain stage ?

Post by Bieworm »

It is possible if the power transformer has enough filament current on tap. But why would you need an extra gain stage on a plexi? If you need even more overdrive you could look at JCM800 schematics. They have more overdrive, but the same amount of preamp tubes. Quite an adventure for a 2nd build though…
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Re: TT-PX18 Add gain stage ?

Post by Tomten »

I´ve been looking at the Tube Town JC18 kit also, its more of a JCM style amp-kit, the question is, would it be better to put in a 4th 12ax7 tube in this type of amp ?

In response to your question why someone would want to add a 4th pre-amp tube in their plexi or even other mods ? Well I would say that its because they want more gain out of their amp and possible tighten it up a little, its all about personal preferences I guess and still there is many many people modding their Plexi amps, like, why on earth would someone want to put EMG´s in their guitar ? That's because it's a personal preferens and/or likings.

I would need to pay a professional to help me draw a correct schematic and make a correct layout of how to add a 4th pre-amp tube in this JC18 kit, because so far, no one on the internet have given me the correct information.

Quite an adventure for a second build ? well, this type of amps with low wattage is quite simple actually, I would agree that it would be quite of an adventure of I told you I am about to build a VH4 clone as a second amp build, that would really be challenging. Learning by doing have always been the best way for me to learn stuff.

Link to the JC18 kit..

Thanks

https://media.tubetown.net/cms/userfile ... layout.pdf
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Re: TT-PX18 Add gain stage ?

Post by JMPGuitars »

Tomten wrote:
Sat 06/22/24 6:47 am
Quite an adventure for a second build ? well, this type of amps with low wattage is quite simple actually
It's not that simple, that's an illusion. If you want to see some 18Watters with an extra gain stage, look at my "Xtra" series in the downloads section. I've already done it, and it's awesome.

Lead dress and soldering skill matter more than the layout, so read the soldering and grounding threads and watch the videos in my signature and improve your skills.

Thanks,
Josh
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Re: TT-PX18 Add gain stage ?

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I am 47 years of age, I did my first soldering project at the age of 7, since then I´ve been working with soldering for a long long time, today I have a small company where I build and sell distortion pedals that I sell and shipping, Canada, USA, Germany, UK, Australia and all over the world, I´ve made my own schematics and get my PCB´s done in .. what should I say, a professional way, 10-12 years ago I did my own PCB´s but I don't do that anymore since I scrapped my etching tank due to lack of space. I have a huge stock of component, many many hundreds of thousands of components, mostly for pedals and other electronics than guitar amps.

Now I want to get in to amps, i´ve never really had the interest to build amps until a couple of years ago, its quite something different compared to a pedal or a radio or a tv, even when it comes to the schematics I do understand most of it, but I am not there just yet how the circuit in an amp works and the tubes and gain stages, even though I do understand the 4 gain stages in my own pedal more than well, because I made it, more or less.

How ever.. I have hired a professional to take a look at the schematic and layout of the JC18, he can make the schematic for the 4th 12ax7 and also extend the existing layout of the PCB so I can look carefully at the schematic and then at the layout to see what needs to be done practical. There will even be possible to some other great mods with this type of kit he said.. so I have to wait and see..

I will have a look at your build/mod thread JMPGuitars, I have a feeling that it can be quite awesome to do.. :D
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Re: TT-PX18 Add gain stage ?

Post by JMPGuitars »

Watch the videos anyway. I've also been soldering for decades (we're about the same age), and I still watch them occasionally to improve. 😉
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Re: TT-PX18 Add gain stage ?

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JMPGuitars wrote:
Sat 06/22/24 12:37 pm
Watch the videos anyway. I've also been soldering for decades (we're about the same age), and I still watch them occasionally to improve. 😉
When it comes to soldering I don't think I have anything to improve, it's gotten to the point where I feel like everything is working just like it should, at least for the last 20-25 years, or even better. I can improve on the schematics when it comes to tube amps.
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Re: TT-PX18 Add gain stage ?

Post by JMPGuitars »

Tomten wrote:
Sat 06/22/24 1:28 pm
When it comes to soldering I don't think I have anything to improve, it's gotten to the point where I feel like everything is working just like it should, at least for the last 20-25 years, or even better. I can improve on the schematics when it comes to tube amps.
Got any photos of your first amp build?
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Re: TT-PX18 Add gain stage ?

Post by Bieworm »

IMHO building amps with that many tubes/gain stages is pretty tricky. You’ll need a well thought through layout and lead dress. Oscillation will be your enemy, lurking around the corner. It’s the easy part of drawing a simple adapted schematic that worries you? I’m confused, based on your experience, that this would even be an issue.
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Re: TT-PX18 Add gain stage ?

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Bieworm wrote:
Sun 06/23/24 8:18 am
IMHO building amps with that many tubes/gain stages is pretty tricky. You’ll need a well thought through layout and lead dress. Oscillation will be your enemy, lurking around the corner. It’s the easy part of drawing a simple adapted schematic that worries you? I’m confused, based on your experience, that this would even be an issue.
I have hired a professional that will make a new schematic and a new layout so that it will be more easy for me to add the extra gain stage, you don't have to be confused, I will learn how tubes work and how to do things the right way when it comes to tube amps, its not quite the same things as building pedals.
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Re: TT-PX18 Add gain stage ?

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And now I know how to add this extra gain stage the best way possible on the Hi input, also another mod that tighten up the distortion a little bit on the Hi input, also possible adding a bright switch in the Hi input, the idea here is to be able to use the Low if I want to use external distortion pedals and such. We will have to see how this is going to turn out, I do believe that I will be able to build and or two awesome amp heads and maybe a matching speaker cab also. :D I will need a backup amp head so maybe I will build one more after I gotten the first one to work the way I want.
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Re: TT-PX18 Add gain stage ?

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why buy the kit? I order a lot at Tube-Town. They’ve got almost everything you need in loose parts. The kit often dictates you to use certain tubes and parts of which there are better alternatives. I avoid JJ tubes for that matter. Nothing but trouble nowadays with those. It’s sad, because they used to be great tubes with a very warm tone.
Also, I don’t know if the kit has Belton sockets. Those are a lot better than most ceramic types. The ceramics are hard to determine the quality ones from the crap ones. And with crap I mean that the lugs are flimsy sharp and the ceramic body loosens from its support when yanking tubes in and out.
But what I mean is.. since you appear to be very enthusiastic on the build(s), why take away the fun in sourcing the parts and build from scratch. It helps to buy a blank turretboard and turrets, so you can easily make the layout according to the extra gain stages, and still get a tight looking monster. 🤘
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Re: TT-PX18 Add gain stage ?

Post by Fire18tone »

So, the basic question here is "Can I hot rod a plexi?", and the answer has got to be "Yes"! This has been a favorite pass-time for amateurs and professionals alike for the past 40+ years. Just Google it!
But, why start from the PX18 kit? You would be better off getting the Modulus Deep Fried Marshbar. It is an already hot rodded plexi, just build it.
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Re: TT-PX18 Add gain stage ?

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Fire18tone wrote:
Tue 06/25/24 1:26 am
So, the basic question here is "Can I hot rod a plexi?", and the answer has got to be "Yes"! This has been a favorite pass-time for amateurs and professionals alike for the past 40+ years. Just Google it!
But, why start from the PX18 kit? You would be better off getting the Modulus Deep Fried Marshbar. It is an already hot rodded plexi, just build it.
I think that's exactly what Mike Soldano did. check those schematics
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Re: TT-PX18 Add gain stage ?

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Bieworm wrote:
Tue 06/25/24 7:05 am
I think that's exactly what Mike Soldano did. check those schematics
And I used the SLO lead channel with an 18 watt power amp in my last build, work just as great as expected :D
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Re: TT-PX18 Add gain stage ?

Post by Tomten »

Bieworm wrote:
Mon 06/24/24 12:38 pm
why buy the kit? I order a lot at Tube-Town. They’ve got almost everything you need in loose parts. The kit often dictates you to use certain tubes and parts of which there are better alternatives. I avoid JJ tubes for that matter. Nothing but trouble nowadays with those. It’s sad, because they used to be great tubes with a very warm tone.
Also, I don’t know if the kit has Belton sockets. Those are a lot better than most ceramic types. The ceramics are hard to determine the quality ones from the crap ones. And with crap I mean that the lugs are flimsy sharp and the ceramic body loosens from its support when yanking tubes in and out.
But what I mean is.. since you appear to be very enthusiastic on the build(s), why take away the fun in sourcing the parts and build from scratch. It helps to buy a blank turretboard and turrets, so you can easily make the layout according to the extra gain stages, and still get a tight looking monster. 🤘
Ok, to tell you the truth, I am on total going to build 3 of these amp heads, two on stage and one spare, this first one is a kit but I will build the other two heads by ordering the parts my self when I have made a BOM and sourced some good quality components. I will get the schematic and layout for the 4th pre-amp tube tomorrow or the next day. I also would want to add a FX loop module, but that's for a later project when the amp is up and working good. Yeah it should come with Belton sockets.
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Re: TT-PX18 Add gain stage ?

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Fire18tone wrote:
Tue 06/25/24 1:26 am
So, the basic question here is "Can I hot rod a plexi?", and the answer has got to be "Yes"! This has been a favorite pass-time for amateurs and professionals alike for the past 40+ years. Just Google it!
But, why start from the PX18 kit? You would be better off getting the Modulus Deep Fried Marshbar. It is an already hot rodded plexi, just build it.
I ordered the JC18 kit instead, and I live in the EU and UK is not, that means I will have to pay 25% in Customs and another 3.4% VAT, that will be an expensive amp in the end, that's why I went with Tube Town.
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