XTC Board Architecture

[marl3y]

Not sure if this is common knowledge or if anyone cares, but I find this kind of thing useful for DIY. The only Randall module I have is the XTC, so I'm not sure how informative this is for other modules/PCBs.

Basically I've tried to highlight the signal components on the PCB by color coding them and illustrating their connections to the tube board. No being an EE I find this graphical blend of the PCB and schematic the easiest to visualize when trying to make informed tweaks. I'm sure there are better ways of doing this so please feel free to comment.

Happy modding.


free photo hosting

http://www.scribd.com/doc/114286254/XTC-Board

 

[kc2eeb]

Very useful. Thank you very much for your effort.

 

[BigBrewtus]

Great looking layout! I am sure this will be helpful to many.

 

[pettymusic]

Very helpful indeed! Thanks!

 

[nikki-k]

Thanks!
The XTC board is a unique one, yes? I think there are XTC, Clean, Brit, and Recto boards, with multiple modules built on each of them, except the XTC which is just the one?

 

[marl3y]

Yeah, that's the sense I'm getting, although I'm not sure what about the XTC circuit demands a unique board. I'm assuming the clean board has the tone stack before the gain stages. I don't know much about rectifiers. If I get my hands on a Brit board I'd do that one as well. It seems like it could be the most flexible for the majority of designs.

 

[pettymusic]

I have been learning a great deal about these circuits and what does what all thanks to knowledgeable people who contribute on this forum. I have basically altered all of my stock modules in some way. I find it very peaceful and relaxing when I am there soldering, adding switches, and just experimenting with different values and cap/ resister types. It is also very pleasing to know that when I fire up and play through my rig, I am as much a part of my amp as I am the music that I play...and my guitar as well (it is also heavily modded :twisted: )

I have learned that the amp is an instrument itself. This is something I have only realized in the past year, since I have been tinkering with my RM22.

So, thanks to those who contribute to this site. Thanks for sharing with us and guiding those of us who may not be electrical engineers per say but, guys that are handy with the soldering iron and have just enough know how to get ourselves in trouble. :roll:

Now for my newb question:

I heard it stated before that silver micas and ceramic caps are best used in certain parts of the circuit. Can someone shed more light on this subject for me?

I recently replaced all ceramic caps with Silver Micas (of the same value) and all of the other cap types (C1,C7,C8,C11,andC18) with Wima caps of the same value on my XTC.

I definitely got more detail out of the changes however, the highs tend to be slightly loose and grainy, if you will, for my taste.

Any advise, input, criticism is welcome.

Thanks!

 

[mikegyver]

Sweet post! Thanks for the XTC PCB! I don't know if it's in the database, but you should contact graham pearson and make sure this gets into the module database.

I heard it stated before that silver micas and ceramic caps are best used in certain parts of the circuit. Can someone shed more light on this subject for me?

I recently replaced all ceramic caps with Silver Micas (of the same value) and all of the other cap types (C1,C7,C8,C11,andC18) with Wima caps of the same value on my XTC.

I definitely got more detail out of the changes however, the highs tend to be slightly loose and grainy, if you will, for my taste.

There have been countless discussions on this topic, and I think I have read them all! The consensus is that silver-micas are generally "smoother" sounding than ceramic caps. Most people say they are more crucial in any treble-related frequencies, where if it is treble-related, it should be silver-mica for the "best" sound.

Others claim there is no audible difference, and that silver-micas just cost more. The audible difference comes from the value change, and not the material. Though, it is said that small ceramic caps are more prone to temperature degradation than silver-mica, so silver-mica might be the long-term choice.

If you are hearing changes, it's probably because the old caps had looser tolerance or had drifted from age. If you put in high-quality 1% tolerance ceramic or 1% silver-mica, it supposedly won't make a difference. Either cap will work, though Egnater uses silver-mica so I would probably pick whatever he thought would work in that particular spot.

Bottom line = Value change is far more important than ceramic vs. silver-mica