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Messages - phatt

#2296
Schematics and Layouts / Re: Passive Tone Circuit
June 08, 2009, 10:12:16 AM
Just adding Something to help you understand why this works so well.
Here is a snapshot of shootout between the *Tonemender and the PhAbbTone*.

Tonemender is average, at around 13dB cut in the mid.

The PhAbbTone big mid notch is clearly evident and my 30dB cut claim is really quite conservitive.
That deep mid notch does amazing things when used in front of even the most basic tube screamer OD pedal.

BTW all those frequency altering switches and add-ons only really shift the mid point up or down a bit and in reality are not much use (IMO)
I have built The famous Dumble tone stack and it's another one that shifts the mid around but nowhere near as powerfull as the HiWatt setup.
Cheers, Phil.
#2297
Quote from: J M Fahey on May 31, 2009, 12:33:30 PM

As Phil does, I find your Drain voltages perfect. The Gate should be at "0" volts and the source slightly negative relative to it. The slight deviation compared to theory may be due to the fact that Sources are "force-fed" through a resistor from the -15V supply.


Thanks JMF,
Sadly sims don't give the novice those little gems of knowledge that you have collected. :( 
So thanks the sim now makes more sense,, good to know.

But for a chap like me starting out a hobby in electronics at the middle part of life,,, Sims do help put some of the puzzle together.

Yes Drew,, intermitant problems are the worst kind.
At least you got it fixed.
Phil.
#2298
The Newcomer's Forum / Re: Audible Hum in Ruby Amp
June 01, 2009, 08:22:03 AM
Great,
         Just to be clear you only need shielded cable for the sensitive things like the *Input* and maybe long wires inside cases that might pickup hash and hum.

But sounds like your catching onto it all so keep up the good work.
Cheers, Phil.
#2299
Hi Doug,
Well if your going to use fets be warned that tillman preamp will just distort very quick on such a low supply.

I've built fet circuits with 35VDC supply and no matter what you do they just hate really big signals.
Lets face it there are 100's of circuits that will distort but try and find one that does really good clean?
This is where valves shine as they can handle really big signals.
The best way round this often over looked issue that I've come across was to make the preamp passive this way the input to your amp will always be clean.

Then you insert the other OD devices if you so wish.
Read what JM Fahey has to say about those fet preamps as they are way to over rated sure they work but you can do a lot better with other tricks.

Fets sound and react much like a pentode on a staved voltage,,
masses of gain but very little headroom.
Some like that   but don't ask for clean.
Just my two cents,, Phil.




#2300
Schematics and Layouts / Re: Passive Tone Circuit
May 31, 2009, 11:46:27 AM
I thought you chaps where going to breadboard it all first?
But hey if you want to just dive in I'll help as best I can,
Phil.
#2301
I'm not the best expert here but to the best of my Sims Knowledge,, ;)

With Pos = +25VDC and a Neg rail =  -15VDC
Then Drain sounds about right,,, around +15VDC

My Sims says; Source should be about -3VDC
Therefore Gate should hang around -2VDC

I'm only using the jfet model so won't be perfect but should give you an idea of what to expect.
Long time since I played with fets but generally the gate voltage should be close to Source voltage.
Hope it helps,, Phil.
#2302
Hi sounds like you doing well, ;)
Trouble shooting your own problems is the best way to learn.

Re CAT5 cable is lightyears away from audio cable it will have very little effect at reducing Audio noise.

If you wish to reduce noise then shielded audio cable is what you want to use,,
not to be confused with 75 ohm TV coax.

I just trash old VCR's and other electronic equipment to get a lot of parts like that.
I'm a pensioner and have very little funds so every little piece of unwanted equipment is gutted for parts.

Try the audio cables that those old CD Roms came with,, the ones that went to the old sound cards,,, they where shielded Audio and they are very fine and flexable.

When you use the Aux power input don't be suprised if there's an increase in background hum,, t'will depend on how good the regulation of the DC supply is.
Some are good and some,,, not so good.

A battery has Zero ripple so darn hard to beat for noise free PSU.
Cheers, Phil.
#2303
Hello Doug,
Are you intending to breadboard all this first or are you just jumping straight into the build stage,,, and prey for a miracle? :loco

I don't mean to hurt your feelings but I strongly advise you to think about it as there is a minefield of problems that I can see already.

Just one issue for starters ; Tillman circuit is only for outboard preamp
ala Acoustic guitar peizo PU's,, Not really intended as a main Preamp.
Phil.
#2304
Q?
     Is this one powered by a Battery or are you using a Plugpak?
Phil.
#2305
Hi DrewV, sounds like your getting closer, :tu:

Um I don't believe you can test FET's in situ? Just wondering how you tested Q1,2,3?  (head scratch?)

My guess is ,,One of the first 3 FET's has died and gone to Electro Land.
The schem is blured but Data  for a 2N4304 says;
general purpose 30 volt JFet.
I'd just grab a couple or three of something similar and replace them (one at a time)
Maybe try 2SK30?
Or if you want keep going backwards with you detective skill,,,just keep working through each stage.
Break the signal path between each stage and just inject an audio signal untill you find which stage is stuffed.
Hope it pans out,, Phil.
#2306
Quote from: mpuckett on May 27, 2009, 01:12:10 PM
Hi Phatt,
Thanks very much for the diagram. I think I can follow that. Could you tell me though why the input needs to be a stereo jack plug? Does it function the same as a jack plug that contains a normally open or a normally closed switch? The current jack I have is just a mono tip, ring. On a tip, ring, sleeve jack would that be a left, right, ground connection?

Yes your right it *IS* a stereo socket but who said you have to use it for audio?

As your only needing *Mono Audio* then the Ring is left *Unused*. So now we can be inventive here and use the ring as a Switch.     Pretty kool ay?
There are lots of oddball tricks like this used in electronics.
Understanding analog switching takes time to grasp sometimes it can bend the brain even for those who are experienced.

Yes you can use a simple mono socket but you then need another seperate power switch so why not use the insertion of a mono guitar cord to bridge the *unused ring* to the battery negative ,,switching on the unit as you plug in.
Phil.
#2307
Schematics and Layouts / Re: Passive Tone Circuit
May 28, 2009, 10:46:28 AM
Quote from: iTzALLgoOD on May 28, 2009, 09:33:18 AM
Have you downloaded the GM libraries for Eagle?  It is set-up almost perfect for most of the stuff we do here. I'll see if I can find a link.

here ya go.  Click on the link and follow the destructions.

http://gaussmarkov.net/wordpress/tools/software/eagle-cad/

Thanks I'll look into that myself but not until these chaps have sorted their issues.
I hate updating programs in the middle of using them as something always goes fut and you end up in a nightmare not being able to find /access a file.
Cheers Phil.
#2308
Schematics and Layouts / Re: Passive Tone Circuit
May 28, 2009, 10:33:59 AM
First my sincere apoligies as I fluffed the schmo,, opps.
No pain as it works both ways which is why I probably gooffed it up cause I've built it both ways and my ears can't tell the diff.  A sim reveals very little difference also.
Just the same I should have been more careful. :trouble  (the bats for me.)

Obviously a little trouble with Eagle.
So here goes;
1/
Pots are *piher PC16S* these are very close to the 16mm pot I use.
2/
  Com1,2,3 are just *wire pads* renamed you just have to give them different names.
3/
  If you want to change a component just click the little *spanner* and select *package*
this brings up the part list again.
4/
  I struggeld with opamp packages so I just used the *dil* and select dil8 for my needs it's fine as you know the pinouts.
Zappacat note that VR2 and VR3 have the wiper not connected, you need to fix that.

As I don't mount the sockets on the board there is no need for them which is probably good cause I've never found a part that comes close to standard 6.5 either.

I have found those onboard mounted sockets can be a pain and are often the thing that breaks down first.
so standard chassis mount and hand wire up for me.


Again sorry for stuffup, I guess my only excuse is it a hobby and I'm not making money from it. thanks Phil.  Here is a couple of shoots of my file.
#2309
Schematics and Layouts / Re: Passive Tone Circuit
May 27, 2009, 08:57:05 AM
Hi sergscar,
Here's a pic of how I do it,,, might help?
I use eagle but I do the boards by hand as most of my stuff is simple and for one off's it's not worth all the bother. 
I just use a fine tip oil pen and etch the thing, Eagle just helps to keep all my centre pops exact. I print out a mirror on paper tape it to a blank,, lightly C pop all holes,,,then just join the dots,, etcxh and drill.
Of course you would not do it like this if you went into mass production. :loco

Note: This is the earlier version so it's not exactly the same.

Cheers Phil
#2310
Hi there mpukett,
There are several ways to do it.
This is similar to the way Boss pedals do it but you do need the right 6.5 input socket which turns the power on when you insert a jack plug. Just use a stereo TRS socket. (Tip-Ring-Sleve)
When you insert a mono plug the Ring is shorted to ground which turns the unit on.
So TWO Things are happening here,
Input socket turns the unit ON (by connecting the ground to the negitive rail) and inserting the wallwart disconnects the the battery positive passing supply over to the wallwart.

Be aware that the DC socket is a trick to wire up as it has 3 terminals. The centre is usually obvious but if you wire the other two wrong then you can fry your battery.
These Aux power sockets come in many sizes so make sure you use the same dia as the plugPak/Wallwart you use.
Diff dia's, diff lengths, I do wish they would try to stick to one type/size,,
it would make life just that little bit easier.

Use a plugpak that is well regulated and designed for audio use,, some are porely regulated and can add a lot of unwanted noise to your sound.
I've drawn the aux power as "Centre Negative" (Boss) but there are other ways to do it.
Hope it helps a bit. Phil.