RunOffGroove Tube Reamer Question

[slashandburn]

This is bugging me. One of the first circuits I started playing around with was this TS clone from RunOffGroove.
http://www.runoffgroove.com/tubereamer.html

Its incredible simplicity appealed to me. Had a lot of beginner problems. Went back and forth between loads of different schematics, lost a bit of hair, eventually got a working circuit that was worth all the hard work.  I was just glancing back over it there still trying to work out where I was going wrong.

The low pass filter going into the (active?) the tone stage, Is that 22n cap going to ground a typo? Im probably misunderstanding something or overthinking again.  Please someone correct me if I wrong.  Most other schematics show a .22 (220n?).  Is there a reason wed want that Low Pass set at 7kHz?   *edit* I not trying to find a way to blame someone else for my own mistakes.  Honest!  Well, maybe.

Iain

[ubersam]

Have you read this: http://www.geofex.com/article_folders/tstech/tsxtech.htm ? It helped me understand what was going on with the TS & similar circuits when I started DIY-ing.

In the TS, the 1k/220nF cuts the highs from 723Hz on up, the tone control brings it back up centered around 3KHz. The ROG Tube Reamer does not have a tone control. Instead, by using a smaller cap (22nF) the filter is set to cut off at a higher freq. (7.23KHz) to retain the highs. It would sound pretty dull with a 220nF. The second stage is a booster with a 5.25 gain, boosting from around 132.7Hz on up.

[Frank_NH]

The low pass filter on the second stage is there to pass all of the guitar-relevant frequencies, and perhaps to avoid squealing due to amplifying higher frequencies.

But one of the great things about Tube Reamer is that it is a great platform for modding!  Tack on a tone circuit at the end, before the volume control.  Add a boost switch by switching between the 12K resistor and say a 2.2K resistor in the second op amp feedback network.  Use LEDs for the clipping diodes.  Use asymmetrical clipping diodes.  The sky's the limit.   

[slashandburn]

Nice one thanks Sam!   Nobodys fault but my own, then. Ha, oh well.  I need to learn to think aswell as just read.   Yeah Ive skimmed through the geofex TS article, "skimmed" apparently becoming the key word there. Ill start doing some more reading (and thinking the circuits through) before posting halfbaked questions again!

Cheers Frank!  Yeah, I got a bit carried away adding all sorts of stuff.  Had to strip it back down to basics and now looking to see where I was going wrong.  Had a few somewhat "working" iterations with different features, the last one (which im certain had no low pass filter or tone control at all, just a single opamp) did infact squeal like a banshee. You could be onto something there.

Bugger.  Back to the breadboard and textbooks.

Iain

*edit* Im known to stretch the word "working".

[slashandburn]

It would sound pretty dull with a 220nF.

That helped clear this up for me.  I guess I found it more confusing since the cutoff frequency for the other low pass is (usually) around 720Hz too (though in this ROG Tube Screamer thats been brought down).  When it looks like Ive just added or missed a decimal point on my calculator I find myself getting a bit lost.  Damn all these number conversions.

[bluebunny]

This is probably no help at all, Iain, but I built this exactly according to the ROG schematic and it's my fave TS pedal.

BTW, do go back and re-read R.G.'s excellent TS article.  It's one of the first things I came across when I started down this slippery slope.  I ended up reading it many times, and each time more and more of the detail fell into place and made sense.  Stick with it!   

[slashandburn]

That enclosure looks fantastic Marc! Good Job.

Its a great little circuit, even just the first "block" of it gave me a surprise. I just got myself a bit carried away with lifting blocks from circuits from all over the place and bolting them together.

The sky's the limit.   

That has probably been my biggest problem, biting off more than I can chew. It's all good though, I like learning this way. I just need thrown a rope occasionally when its time to reign myself back in for a while.