JTM45 Build

[guitarmike2107]

Well the plexi screen will affect you how you hear the amp too of course, but then you hopefully have a monitor set up that you can get your amp put in the mix.

From the mics point of view there could be some reflection that you don't like and that can be easily solved with some acoustic foam, available on ebay for pretty cheap. there is actually a pre made solution for this, pretty sure I saw it at gear4music or on a Pete Thorn (youtube) gear demo

[ArrogantOwl]

Why would it take you 2 hours to read through this thread? Unless you're an extremely slow reader it wouldn't take you longer than 15minutes. Also why would you read this thread, find out it wasn't an issue and then read through the same thread on the Tube Guitar Amp Builder page?

.

Back tracking to make sure I didn't miss anything as certain terms are quite unfamiliar. Go through it with a fine tooth comb trying to think and learn something, and it'll take some time. I read the thread over on the FB page first and then came here.

And 15 minutes is less than a minute per page, so nice hyperbole.

[JazzGuitarGimp]

Yup.... It's quickly approaching a half-minute per page...

[Littlewyan]

Can't beat a good hyperbole......So basically you read the thread on FB where we found out that it wasn't an issue and decided to come here to read it all again. Anyway what do you want me to do about it exactly? I edited the first post as soon as Miles mentioned it so people are warned, in fact I edited it two days before you posted. You chose to read the thread, you can't have a go at someone because you didn't deem it worth reading.

Michael - I think I might stick to the PPIMV for now. I'm actually a bit tight on space at the moment so buying a plexiglass screen wouldn't be a great idea for me.

[pdf64]

Go through it with a fine tooth comb trying to think and learn something

I can't perceive how someone wanting to gain experience in the amp building / debugging process could not take away some useful info / points to note etc from a close reading / review of this thread?
It can be frustrating and sometimes there's no easy resolution.
Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.

[cbass]

I think this thread should be a sticky

[ArrogantOwl]

Can't beat a good hyperbole......So basically you read the thread on FB where we found out that it wasn't an issue and decided to come here to read it all again.

1. I personally didn't expect to see the same topic in a different place under different names.
2. Maybe I should've realized it was the same topic based on your stubbornness to refuse the advice of known experts.

Anyway what do you want me to do about it exactly?

Nothing. Let's stop wasting our time over it.

I edited the first post as soon as Miles mentioned it so people are warned, in fact I edited it two days before you posted. You chose to read the thread, you can't have a go at someone because you didn't deem it worth reading.

I started reading it before you edited it.

Go through it with a fine tooth comb trying to think and learn something

I can't perceive how someone wanting to gain experience in the amp building / debugging process could not take away some useful info / points to note etc from a close reading / review of this thread?
It can be frustrating and sometimes there's no easy resolution.
Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.

I learned little bits and things, but nothing entirely new and unknown. Other than the PI of a JTM45/50+ doesn't behave properly under an extreme scenario.

[Littlewyan]

Yeah you should have seen the stubbornness between the lines. You could have maybe guessed it was the same topic by the fact that a JTM50 was built and the same issue was described.

Which advice did I ignore? Miles mentioned this but I don't see which advice I ignored that would stop the amp from behaving in that way? PDF64 mentioned lowering the input cap values which I'm going to experiment with but other than that, nothing. Its a flaw with the circuit. So what did I miss?

[ArrogantOwl]

Yeah you should have seen the stubbornness between the lines. You could have maybe guessed it was the same topic by the fact that a JTM50 was built and the same issue was described.

Which advice did I ignore? Miles mentioned this but I don't see which advice I ignored that would stop the amp from behaving in that way? PDF64 mentioned lowering the input cap values which I'm going to experiment with but other than that, nothing. Its a flaw with the circuit. So what did I miss?

I think Lyle mentioned something about resistors failing in audio frequency but you were hung up on only finding information around Ghz. Not a big deal.

[Littlewyan]

You mean the only information I found regarding that issue was to do with Ghz frequencies. Bit high for an audio amplifier. I spoke to many people about that and no one had ever heard of it, so I asked for info from Lyle and didn't get any. I never said I didn't believe him, I just wanted info. In the end though before I got to replacing the resistors it turned out it was normal for the PI to behave that way.

None of the advice given would have solved this issue. Its a flaw in the circuit. The only thing that may stop the PI from behaving that way would be smaller input caps. Unless there was any other advice that I was apparently too stubborn to take that would stop the PI from behaving that way? You went over both threads with a fine tooth comb so you must know.

[ToneMerc]

it just doesn't have enough grit for my liking. Its very smooth.

Pretty much describes how it should be; this is not first time someone has built one of these and in the end, it turned out to be not exactly what they thought it would be.

TM

[Dai H.]

(perhaps not everyone, but) I think sometimes people who are disappointed with a JTM45 build really want the brighter, more aggressive 1987/1959 circuit (split cathodes, 33k slope R, etc.) instead.

[ToneMerc]

(perhaps not everyone, but) I think sometimes people who are disappointed with a JTM45 build really want the brighter, more aggressive 1987/1959 circuit (split cathodes, 33k slope R, etc.) instead.

Agreed.

TM

[Littlewyan]

Yeah I read over at the Metroamp forum that most people who build the JTM50 find it too smooth sounding.

Changing the NFB resistor to 47K really helped make it more of an amp for me. I'm staying away from the split cathode and 33k tonestack at the moment, but admittedly I do have the parts on my desk ready to do the change......

[pdf64]

(perhaps not everyone, but) I think sometimes people who are disappointed with a JTM45 build really want the brighter, more aggressive 1987/1959 circuit (split cathodes, 33k slope R, etc.) instead.

Don't forget the monster size bright cap!
Unless the amp's flat out, that may be the most significant difference.
Consider tuning the amp to the required tonal balance with the bright cap value.
6 way rotary switches are good for this.