Update to Hwy 89 schematic and parts.

[John Lyons]

I spoke via email with Doug Hammond and he had a couple bits on info about the Hwy 89 which are not reflected on the schematic or layouts I've seems around here.

Both Tone controls should be log pots

The volume control should be log and can be 100K instead of 500k as well.
The 500K pot has a ton of volume on tap...maybe too much. The impedance is also too high for using pedals after the 89.
Try 100K and it should be better than 500K. If the pedal has too much high end you can put a small cap (.002 or more) across the outer lugs of the volume pot, or make it switchable....

"...just thought you had the right to know"

If you have time MarkM, maybe you could change this on the layout you have up...

John

[markm]

If you have time MarkM, maybe you could change this on the layout you have up...

John

Thanks John!
I'll make a note of these mods as I have plans to re-vamp my 89 Layout so, this is good timing! 

[John Lyons]

Good timing is always a nice thing.

Thanks Mark.

John

[96ecss]

My 89 does have too much volume on tap. I was thinking of changing the volume control anyway, so this confirms it. Thanks John.

Dave

[Traintrack]

Too much volume with a 100K Log! but better that the 500K.

Also in between wake'n up the town with an A-chord, I get radio freq. on both units i Built that are wired with a very stable ground,

Maybe include a fix for this also?

I think this is a great sounding effect, thanks Doug for the circuit and John and Mark for all the help. 

[John Lyons]

I've built two 89s and haven't had any problems with radio interference.
I think it's an isolated problem(s) not inherent to the circuit.

There are a number of threads here that reference how to cure that. Just search "radio"
You can always go lower than 100K if you want. Whatever works will be fine.
Ground solidity doesn't have that much to do with interference.
Did you use a metal box?
Are the wires short and direct?

John

[km-r]

mr hammond gave the permission to post the schematic[with values], right?

[John Lyons]

Yes, Doug gave permission a while back to post the schematic and parts values.

[ulysses]

i also found 500 was to high and dropped it to 100 when i built mine.

the tapers of the pots on my layout are consistent with your post.

i found that it was to trebly for my taste - increasing C2 to .047uf gave much better all round overdrive tone - it got flabby with anything higher than .047uf

cheers
ulysses

[alfafalfa]

Traintrack,

I had similar problems and solved the radio interference with a 68k resistor on the input to Q1.

Try it and let me know.

I also went back to a 100 k pot on the output and put a few low pass rc filters in it  to tame some highs.

Alf

[Traintrack]

I have the radio out now, and I have a 100K log for volume. I tried a few different caps on the lugs and found that it sounds best without any caps. I wish that the design did not have so much headroom, but it is a great box.

[John Lyons]

You can always try a lower value pot for the output. Try 50K and see what that does for you.
The lower the values the lower the impedance...which is a good thing.

Looks like you used an mylar static bag under the board there.
They have metal in them if I'm not mistaken, maybe that's a source of radio signals
if the bag makes contact with all/most of  the solder pads...?

John

[Traintrack]

I have used mylar static bags before. I think they do a good job with shielding. The Radio is gone after I used the wire tubage.

I am done with these. Great pedal. I would recommend to anyone building one to toggle a cap on the volume pot. The smoothness is worth the effort. 

[Antero]

Heh.  I LOVE the insane volume and the brightness.     I've used my Hwy89 on more of my band's songs than any other box.

[John Lyons]

Traintrack

Wait a minute...
The Bag under the board is for insulation ( not shielding) to guard against the traces/pads from shprting against the metal enclosure. Static bags may be non conductive but the shiney metal looking color is mylar which is metal...

The tubing you put on the wires isn't shielding them...or I mean it isn't actually shielded wire is it? I can't see any ground connections to the shield if so. It looks like shrink tubing which isn't "shielding" but just "insulation" same as the plastic insulation already on the wire (blue).

Just trying to clarify here.

John

[Traintrack]

I use the "static bags" to eliminate the shorting but also, I think it does produce some shielding. Electronics are shipped in these bags to protect them and I always thought that it would serve some protection of the circuit. I might be wrong.

The rubber tube in another layer on wire. Some of the cheap wire that I have bought in the past is coated with plastic that could use another layer. It is not "official" shielding wire, that was just a term that I threw out. The pedal did quiet down with those two additions. I no longer hear Christian radio stations. Nothing against Christian radio, but every time I get a radio in any electronics here in NC or back in NJ it is always some preacher!

I am millions of miles away from becoming an expert on building and circuits. But I am learning as I go.

[John Lyons]

Shielded wite  is an outer braid of wire wrapped around a center core wire which block extraneous signals and preventing oscillations between two parts of a circuit. The shield sends the offending signal to ground and "sheilds" the sensitive inner wire.
Wrapping another layer of insulation on a wire will not help with blocking a radio signal or anything electrically speaking. You must have moved a wire of two in the process but electrically, using more insulation won't do anything.The physical layout of wire often will help or hurt a circuits performance. This must have been the case.

The metal case shields everything inside. Adding a mylar bag inside between the case and the board won't help shield it. Think about how thin the bag is compared to the enclosure.The bag is just insulating the board from the metal enclosure.
I use the "blister pack" clear thick-hard-flat plastic stuff that comes on things from the store. Sometimes I hot glue it to the bottom of the enclosure.

I'm not trying to pick on you for what it's worth...   

John

[markm]

I'd put money on it that when the wires were shrink wrapped, it moved the wiring in such a way that cancelled some of the noise.
Such as the way some builders will "braid" wiring and such.
I think this is what you were getting at John.

[Traintrack]

Cool, thanks guys. Learning as we go. I understand where you are comming from John and thanks again.

All in all very happy with the circuit. Can't wait to see somone rip it off and sell pedals for 320.00 

[Ucho]

Thanks for the infos John, I'll try these as soon as I can get a pot.

Concerning the higher otuput impedace using a 500k pot instead of a 100k one....
Sometimes, when I can't use the tube amp in my room, I like to connect the stompboxes output to my PC line in and run a software amp sim, so I can play in my headphones etc.
(I know it's not the best solution, but it works ok for these needs).

One thing I noticed with the HW89, using it this way, is that I had to turn the volume control way up (above halfway) to have unity gain with bypassed volume, while when I use it in my amp i usually set volume on 2-3/10.
This is the only pedal having this behaviour, all others mantain the same volume ratio with bypassed signal as when used on an actual amp.

Could this behavior be caused by the output pot and the resulting output impedance?