My first build Jim 5watt V2.0

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Tomten
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Re: Need ideas for my first build

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TriodeLuvr wrote:
Wed 03/16/22 9:17 pm
Yes, that's it. I would just make the following additional changes (parts designators same as in your V2 schematic):

Install a jumper in place of R6 (220K). Replace R15 (470K) with the 220K removed at R6. Change R13 (6.8K) to 1.5K and bypass it with a 10uF capacitor (just like the first stage).

These changes will allow you to compress the front end using the Volume control, but still control overall gain with the Master.

Jack
This is getting better and better, i made those changes in my schematic just to see what it would look like with all the changes, i will try those things today on the original PCB and i will get back with a report.
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Re: Need ideas for my first build

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When I put in a 1.5k on R13 and bypass it with a 10uF the amp is not working properly, almost no sound coming out of it, if I put in the 6,8k it works but the distortion sounds not very good if I go past 1 o clock on the Volume knob..it sounds ok before I go past 1 o clock, maybe similar to full blast before all these mods.

How do I fix this so its working as you was thinking Jack ? These mods makes sense to me so I think it needs some minor adjustments.. ?
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Re: Need ideas for my first build

Post by JMPGuitars »

C16 is backwards in your schematic. If you're using a polarized cap, negative goes to ground there.
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Re: Need ideas for my first build

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JMPGuitars wrote:
Thu 03/17/22 7:49 am
C16 is backwards in your schematic. If you're using a polarized cap, negative goes to ground there.
Yeah.. i noticed that before i started the project, in the amp its polarity is ok.. :D
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Re: Need ideas for my first build

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Tomten wrote:
Thu 03/17/22 8:03 am
JMPGuitars wrote:
Thu 03/17/22 7:49 am
C16 is backwards in your schematic. If you're using a polarized cap, negative goes to ground there.
Yeah.. i noticed that before i started the project, in the amp its polarity is ok.. :D
Check the connections and wiring carefully at V2A. It's just a standard amplifying stage. Check the voltages on the tube with the 1.5K and 10uF installed. They should be essentially the same as the first stage.

Jack
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Re: Need ideas for my first build

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Check the connections and wiring carefully at V2A. It's just a standard amplifying stage.

Jack
Yeah I've double checked and re-soldered all those connections, as soon as I hook up that 10uF/63 Volts capacitor its not working properly.. it sounds normal if the Volume is at 8 o clock in the morning, then I just touch it a little and its all super distorted and there is almost no sound comming from the cabinet at all, so I just turn the amp of and to be honest, I can't understand why that capacitor is making this problem...
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Re: Need ideas for my first build

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But its not only the capacitor causing a problem, as I said earlier also I can't have the Volume (Gain) more than 1 o clock, or else the distortion starting to sound very very bad.. like there is 300% to much gain or something..
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Re: Need ideas for my first build

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Tomten wrote:
Thu 03/17/22 10:31 am
I can't have the Volume (Gain) more than 1 o clock, or else the distortion starting to sound very very bad.. like there is 300% to much gain or something..
It sounds like your amplifier is probably suffering from blocking distortion,a well-known problem:
https://guitar.com/features/opinion-ana ... uitar-amp/
https://hiwatt.org/2_mod.html
So I recommend using a 470k value for the grid stopper R15, instead of 220k and likewise inserting a 470k grid stopper on V2a. I also recommend changing cathode resistor R13 to 620 ohms, to bias that stage warmer, for a thicker and less fizzy overdrive sound
Also to balance the overall frequency response for guitar,
I suggest changing C2 and c16 to 1uF, with C10 and C12 = 10nf or 22nF (you decide which sounds best to you :) )

This circuit looks like the preamp from something "Single-ended Plexi-like", complete with a "half-PI", but where oh where is the power amp? :?
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Re: Need ideas for my first build

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It feels like I just want to put back the original components and just build another one, another model of amp but the same wattage and better schematic, I mean an amp that is designed alot better than this Jim amp. I would ditch the PCB and use a Point to Point board instead so it will be alot more simple to mod and change components. Would this amp schematic make more sens then the Jim ??
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Re: Need ideas for my first build

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Take a look in our downloads section for some well-tested options.
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Re: Need ideas for my first build

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JMPGuitars wrote:
Thu 03/17/22 6:18 pm
Take a look in our downloads section for some well-tested options.
Yeah.. seem to be a few cool amps there, i am sorry to say that as a beginner i am no way near to just build an amp out of a layout or a schematic only, i would need a parts list including what PT and OT and if choke is used or not, and exactly what resistors and capacitors to get.

I really wish i could just look at a schematic and figure things out by my own, but i can't. This is the only thing that is a problem, if not i would have built several amps a long long time ago. Thats why a kit is great for me to start off with :D, or something that has clearly instructions about all i need so i can source the parts and get started..
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Re: Need ideas for my first build

Post by JMPGuitars »

Look at my docs for the Lite 2b(ish): viewtopic.php?t=24431

My layout is drawn to scale. You can get a complete kit version of it from GDSAmps.com, but it's not 100% the same (which is fine).

Most of the amps on this site will work with standard Marshall 18W (or 36W) transformer sets. I'm sure Bieworm could link you to the right transformers if you're ordering in Europe somewhere.

Besides that, 1W resistors except where noted. I use CMF series metal film resistors. It's really not that hard to source the parts, especially if starting with a simpler circuit like the Lite 2b series.

Thanks,
Josh
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Re: Need ideas for my first build

Post by TriodeLuvr »

Don't give up. I actually built your circuit with these values in a simulator the other day before making these suggestions. It's too late this evening, but I'll take a second look tomorrow to see if there's anything I overlooked. One thing - are you driving this direct from a guitar? No preamp or anything like that, right? Two 12AX7s in cascade should not create blocking distortion, but they might if the input signal is way too big.

Jack
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Re: Need ideas for my first build

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TriodeLuvr wrote:
Fri 03/18/22 12:05 am
Don't give up. I actually built your circuit with these values in a simulator the other day before making these suggestions. It's too late this evening, but I'll take a second look tomorrow to see if there's anything I overlooked. One thing - are you driving this direct from a guitar? No preamp or anything like that, right? Two 12AX7s in cascade should not create blocking distortion, but they might if the input signal is way too big.

Jack
Thanks very much :D I use just the guitar, no pedals at all, my plan with my build was to not have any pedals, i have a great pedal I've been using for some years now that i like very much but i want to see if its possible to have a small amp with no pedals but still a good amount of tight distortion... :D
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Re: Need ideas for my first build

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Look at my docs for the Lite 2b(ish)
Maybe someone have built this and have a video online ? like a demo or something like that ? It would be interesting to hear the distortion in this amp... :D
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Re: Need ideas for my first build

Post by JMPGuitars »

Tomten wrote:
Fri 03/18/22 4:55 am
Look at my docs for the Lite 2b(ish)
Maybe someone have built this and have a video online ? like a demo or something like that ? It would be interesting to hear the distortion in this amp... :D
A TON of people have built it. Probably hundreds. The Lite 2b is the same as channel 1 on the standard 18W, but with a better tone knob.

Another option, which is very similar in difficulty level (easy), is the EF86 Lite. That will give you a little more distortion, with a little bit of the Vox sound meshed with the Marshall sound.
Here's a demo of an EF86 Lite I made for somebody: https://www.youtube.com/watch?v=dj0RL4XVv6A

Thanks,
Josh
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Re: Need ideas for my first build

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I don't think I am very interested in that particular amp, it seem to simple, I would want mids and treble and bass, as well as possible a gain and/or volume and master volume. But thanks for the advice.. :D

After all, I was originally going to build a SLO 50 or 100, I have the PCB´s for it but I find it to expensive to build right now, and I feel like those 5-10 watt amps are a lot cheaper to build. 150-200 Euros or so. Even thought the SLO have a massive amount of gain I don't want to spend the money to build it, I can get an original JCM 800 for the same price as the build cost of a SLO clone, yeah I know, the SLO costs 3-4000 Euros and should not be compared to a JCM 800, but still the JCM 800 is a great amp.. :D
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Re: Need ideas for my first build

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I was thinking if this amp and schematic are better designed for gain then the Jim schematics ? If so, i might just go ahead and build that instead of messing around with the Jim.. :D
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Re: Need ideas for my first build

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So I recommend using a 470k value for the grid stopper R15, instead of 220k and likewise inserting a 470k grid stopper on V2a. I also recommend changing cathode resistor R13 to 620 ohms, to bias that stage warmer, for a thicker and less fizzy overdrive sound
Also to balance the overall frequency response for guitar,
I suggest changing C2 and c16 to 1uF, with C10 and C12 = 10nf or 22nF (you decide which sounds best to you :) )
As I am a beginner at this.. I have no clue where this is, I mean I know where V2a is but not where I am suppose to put that 470k resistor ?
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Re: Need ideas for my first build

Post by JMPGuitars »

Tomten wrote:
Fri 03/18/22 7:45 am
I don't think I am very interested in that particular amp, it seem to simple, I would want mids and treble and bass, as well as possible a gain and/or volume and master volume. But thanks for the advice.. :D
In that case, the best amp build for you would be the SuperLite TMB: viewtopic.php?t=24430

Thanks,
Josh
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