My first build Jim 5watt V2.0

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Tomten
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My first build Jim 5watt V2.0

Post by Tomten »

Hi guys..

This is my first post and i am new here, i´ve been building some stompboxes and other electrical stuff for some years now, i know the basic things about components and how to use them. Some months ago i started thinking that i want to build my own amp, i already have several 100 watt amps (Marshall DSL100 and Laney IronHeart 120H) so this build will be much less than that, 18-20 watt would be great.

I want to build a high gain amp with Marshall or SLO DNA so started looking at different schematics and layouts for different amps, man.. its a jungle, its so much out there. I though about buying a Kit but i think they are to expensive, i live in Europe and need to source the komponents here as well, Tube-Town and Banzai and Musikding and Mouser is great places to start. Also i want to build an amp that can be modded with even more gain and other things, i would prefer point to point.

I have a budget for this build and its about 250-300 Euros or so, it seem like its the PT and OT that is the most expensive, that's also why i don't manage to build a 50-100 Watt JCM 800 or SLO 100 when the transformers costs total close to 300 Euro..

So now i would be happy for suggestions of high gain schematics and layouts that are ok to build with no problems, i see alot of the schematics out there are reported to have problems and i don't think i would manage to deal with to complicated problems when it could be avoided from the beginning by finding a working schematic instead. It would be my bad if i mess up the build by my own.

I apologise for this long first post, i just thought i would bring up the most information as possible so that you guys know a little more about my capabilities and what i am looking for..

Thanks...
Last edited by Tomten on Sat 03/19/22 8:21 am, edited 1 time in total.
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Re: Need ideas for my first build

Post by zaphod_phil »

All high-gain amp designs carry an increased risk of instability and require lots of extra care with the layout. We could say it goes with the territory :roll: So basically, a high-gain amp isn't a good idea for your first build. So start with something like an 18W Lite IIb. Once you've got that working fine, do a cascade mod, so the two preamp channels' gains multiply. :mrgreen:
Another word of advice, don't waste your time trying to build a 100W amp. You can get neighbors complaining when you play an 18W with reasonably efficient Celestion, Eminence or WGS speakers! With a cranked 100W amp, you can kill small birds flying nearby :lol: Keep in mind that sound intensity is logarithmic, so a 10W amp will give you half the volume level of a 100W (assuming the same speaker efficiency) and an 18W will likewise give half the volume of a 180W amp. 8O
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Re: Need ideas for my first build

Post by Bieworm »

You should order the PWAM01 power transformer from primarywindings. It's cheap and has a few nice features. Check on my tremolo tmb posts for details...
The rest I order comes from Tube-Town (hardware)and jukeboxrevival ( electric components and tubes) . Top quality and very good prices. Banzai is expensive..
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Re: Need ideas for my first build

Post by Tomten »

zaphod_phil wrote:
Tue 03/08/22 12:34 pm
All high-gain amp designs carry an increased risk of instability and require lots of extra care with the layout. We could say it goes with the territory :roll: So basically, a high-gain amp isn't a good idea for your first build. So start with something like an 18W Lite IIb. Once you've got that working fine, do a cascade mod, so the two preamp channels' gains multiply. :mrgreen:
Another word of advice, don't waste your time trying to build a 100W amp. You can get neighbors complaining when you play an 18W with reasonably efficient Celestion, Eminence or WGS speakers! With a cranked 100W amp, you can kill small birds flying nearby :lol: Keep in mind that sound intensity is logarithmic, so a 10W amp will give you half the volume level of a 100W (assuming the same speaker efficiency) and an 18W will likewise give half the volume of a 180W amp. 8O
I ordered a 5 watt kit from Tube Town called Jim, it was not point to point but still fun to build and it works great, it has a Volume and a Main Volume and only one channel so it has not alot of gain but i can put a boost pedal infront of the amp and it will tighten up the gain a little. I am thinking maybe its possible to make some mods to this amp for a little more gain except from the boost pedal that is. Best of all for this kit is that it was cheap and still pretty loud, i don't have any neighbours so i can crank up my 100 watt amps as much as i want.. :D Would a cascade mod be possible on the Jim 5 watt amp you think ?
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Re: Need ideas for my first build

Post by zaphod_phil »

Cascading is only possible when you have more than one channel, so that you can feed the amplified output of one channel into the input of the other one. Glad you're enjoying your 5W amp! That's also how I first got into amp building.
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Re: Need ideas for my first build

Post by TriodeLuvr »

zaphod_phil wrote:
Sun 03/13/22 2:38 pm
Cascading is only possible when you have more than one channel, so that you can feed the amplified output of one channel into the input of the other one. Glad you're enjoying your 5W amp! That's also how I first got into amp building.
Couldn't he add a cascade gain stage between the single input and the first tube? Don't know whether the kit has sufficient filament power or if the result would be noise-free, but it should be OK from a topology standpoint.

This might also be a candidate for a FET with a few dB of gain. That would draw very little current, and it could possibly be powered from the cathode bias voltage at the output. Just thinking out loud here...

Jack
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Re: Need ideas for my first build

Post by JMPGuitars »

The first preamp tube is already cascaded: https://www.tube-town.net/cms/userfiles ... layout.pdf
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Re: Need ideas for my first build

Post by TriodeLuvr »

JMPGuitars wrote:
Sun 03/13/22 9:30 pm
The first preamp tube is already cascaded: https://www.tube-town.net/cms/userfiles ... layout.pdf
I know, but that only gives it two gain stages ahead of the tone controls. The Marshall JCM800 2204 (as an example) has three. The Jim probably has enough gain overall, but it's in the wrong place to provide front end compression. If the tone controls could be relocated between V2A and V2B, it would feel a lot more sensitive to input levels.

Jack
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Re: Need ideas for my first build

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zaphod_phil wrote:
Sun 03/13/22 2:38 pm
Cascading is only possible when you have more than one channel, so that you can feed the amplified output of one channel into the input of the other one. Glad you're enjoying your 5W amp! That's also how I first got into amp building.
Yeah.. it was fun building it, 2-3 days later it was turned on for the first time, i checked the voltages and then i played it, i also put on a bright cap but today i put the bright cap on a switch so i can have two different brightness tones.. :D
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Re: Need ideas for my first build

Post by Tomten »

This might also be a candidate for a FET with a few dB of gain. That would draw very little current, and it could possibly be powered from the cathode bias voltage at the output. Just thinking out loud here...

Jack
This would be awesome, i think it know what a FET is and how it works, and i think it would give a little more gain, maybe that's just what i need to get that little extra i am looking for ? :D
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Re: Need ideas for my first build

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Tomten wrote:
Mon 03/14/22 6:24 am
This would be awesome, i think it know what a FET is and how it works, and i think it would give a little more gain, maybe that's just what i need to get that little extra i am looking for ? :D
If you're not familiar with FETs, this might be a bad idea. It would require a small perf board and wiring techniques that are different than those used in building your kit. I can provide a schematic, but honestly, you'll probably be better off using an external preamp.

One other thing that might help would be to increase the gain after the tone controls. This won't compress the font end, but overall gain will go up. You can do this by simply jumpering R11 and/or R15. Each of these resistors is part of a voltage divide that decreases the signal by 6dB (÷2). Jumpering both will increase the voltage gain X4. Note that this might increase noise or make the volume control seem "touchy." You'll need to approach this as an experiment, but it's easily undone if you don't like the results.

Incidentally, after a second look, I realize this circuit only has one gain stage ahead of the tone controls. V1B is a cathode follower that contributes no gain. This is probably why the amp feels as though gain is lacking.

Jack
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Re: Need ideas for my first build

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One other thing that might help would be to increase the gain after the tone controls. This won't compress the font end, but overall gain will go up. You can do this by simply jumpering R11 and/or R15. Each of these resistors is part of a voltage divide that decreases the signal by 6dB (÷2). Jumpering both will increase the voltage gain X4. Note that this might increase noise or make the volume control seem "touchy." You'll need to approach this as an experiment, but it's easily undone if you don't like the results.

Incidentally, after a second look, I realize this circuit only has one gain stage ahead of the tone controls. V1B is a cathode follower that contributes no gain. This is probably why the amp feels as though gain is lacking.

Jack
Wow.. what an great idea, you seem to know very very much about this stuff.. :D so I can just go ahead an jumper R11 and R15 and that would give more gain ? maybe one at the time and see the difference ? I have plans to put in a choke for noise reduction in the rectifier area, maybe that will help a little if I got X4 more gain ? Maybe put the the two new gain stages on two SPDT switches on the front panel ?
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Re: Need ideas for my first build

Post by TriodeLuvr »

Tomten wrote:
Mon 03/14/22 2:41 pm
One other thing that might help would be to increase the gain after the tone controls. This won't compress the font end, but overall gain will go up. You can do this by simply jumpering R11 and/or R15. Each of these resistors is part of a voltage divide that decreases the signal by 6dB (÷2). Jumpering both will increase the voltage gain X4. Note that this might increase noise or make the volume control seem "touchy." You'll need to approach this as an experiment, but it's easily undone if you don't like the results.

Incidentally, after a second look, I realize this circuit only has one gain stage ahead of the tone controls. V1B is a cathode follower that contributes no gain. This is probably why the amp feels as though gain is lacking.

Jack
Wow.. what an great idea, you seem to know very very much about this stuff.. :D so I can just go ahead an jumper R11 and R15 and that would give more gain ? maybe one at the time and see the difference ? I have plans to put in a choke for noise reduction in the rectifier area, maybe that will help a little if I got X4 more gain ? Maybe put the the two new gain stages on two SPDT switches on the front panel ?
Yes, you just need to try a small jumper wire across one or the other (or both) of those resistors. No harm done if you don't like the results. My biggest concern is that V1 isn't shielded and the filaments aren't elevated (biased up with a positive voltage). This might result in hum that will become audible when gain is increased. Hopefully that won't happen, and these changes will make it more satisfactory.

Jack
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Re: Need ideas for my first build

Post by Tomten »

Yes, you just need to try a small jumper wire across one or the other (or both) of those resistors. No harm done if you don't like the results. My biggest concern is that V1 isn't shielded and the filaments aren't elevated (biased up with a positive voltage). This might result in hum that will become audible when gain is increased. Hopefully that won't happen, and these changes will make it more satisfactory.

Jack
This is very valuable information for me as a beginner at amp-building, I will try this tomorrow and I will post a report here how it went.. I am very thankful for the information I've gotten so far.. a big tank you :D
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Re: Need ideas for my first build

Post by Tomten »

Today I removed and jumper the R11 and R15 and yeah, I got more gain, as a matter of fact a lot more gain :D Now I have a question, is there a way to tighten up the distortion a little bit and make it smoother, I mean without putting a pedal infront of the amp. I like the amount of distortion but it seem to be a little bit all over the place.

Any suggestions would be helpful :D :D
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Re: Need ideas for my first build

Post by JMPGuitars »

If you like the sound with R11 and R15 jumpered, you should instead remove R12 and R16. Then replace the R11 and R15 jumpers with 10K resistors.

EDIT: I wasn't awake yet when I wrote that, and was focused on the voltage divider, not the tube.

Thanks,
Josh
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Re: Need ideas for my first build

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JMPGuitars wrote:
Tue 03/15/22 6:12 am
If you like the sound with R11 and R15 jumpered, you should instead remove R12 and R16. Then replace the R11 and R15 jumpers with 10K resistors.

Thanks,
Josh
That sounds interesting, will it tighten up the distortion but also keep the amount of distortion I have right now ?
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Re: Need ideas for my first build

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you should instead remove R12 and R16
You mean just remove, and not jumper R12 and R16 ?
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Re: Need ideas for my first build

Post by JMPGuitars »

The 10Ks will help block unwanted noise, and shouldn't have any noticeable change to your volume/gain level.

Without hearing your distortion, I wouldn't know what to change. Though if I were going to guess at something, I might lower the value of C2.

Another thought, and again, without hearing your distortion, is that those voltage dividers might have been there for a reason. Maybe dropping less voltage would increase gain without being crazy.

Thanks,
Josh
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Re: Need ideas for my first build

Post by Tomten »

Without hearing your distortion, I wouldn't know what to change. Though if I were going to guess at something, I might lower the value of C2.
The C2 is now 10uF, what value would you suggest and what will it possible to do the distortion ? :D
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