Boss HM-2

[Freppo]

I've been wanting to build the HM-2 for a long time..
So I though i'd give it a try at making my own layout, so here it is. :)

I've exchanged the IC's and transistor to modern more common ones.
I had to make two separate boards because of the size.
But hopefully both will fit inside a 1590BB.





VERIFIED!!!

cheers!
/ Fredrik

[IvIark]

Excellent, nice one matey

[mirosol]

Second that.

This one has been requested over and over.
+m

[Freppo]

Ok, so this is my progress so far...

I built it today, but I found a couple of mistakes.
I had screwed up the transistor symbols/pinouts of Q1 and Q2.. doh...
Had to wrist the legs of the transistors to get it to sound.

Now it works, but not as it should. It oscillates alot when turning up the gain. I probed the layout and the oscillation starts after Q2.  I've probably made some mistake around there when I screwed up the transistor symbols/pinouts.

I will investigate further... Besides the oscillation, it sounds very promising!
It definitly has the HM-2 sound and the controls works as they should :)

Until I fix it, please don't built it!
cheers / Fredrik

[Freppo]

VERIFIED! Woohoo

I exchanged Q2 for a 2N5088 and now it works fine!
I still got alittle oscillation when the gain is maxed. But increasing the value of C5 cured that, so try a 22pf or higher there if you get any oscillation.

I also changed the values of the pots to give better control. The 250k gain pot did all the action at the first 30% of the turn, so a A100K works alot better. Also, the tone pots had a sudden jump at the end of the turn, so anti log pots will work much better.

I rejigged the layout to match the transistor pinouts and updated my first post.

cheers
/ Fredrik

[Freppo]

oh, and btw. It does fit a 1590BB comfortably. :)

[Freppo]

Another update

I borrowed an original from a friend today to compare..

My clone has way less gain then the original... :(
Probably because of the transistors. I will play around with different ones when I have time.

It's also a bit bassier (but it's probably also percieved that way because it's lacking in gain)

So... not quite there yet. :/

EDIT.
BTW, spotted another error.. Q1 needs to be turned around.
Will update the layout later and also add the pinouts, so you can try different transistors.

cheers
/ Fredrik

[Freppo]

Finally I'm done with this one...
Macsniper at the freestompbox forum found a small error on the layout, when corrected it solved the issues with oscillation I was having while using hi gain transistors.

Now it comes very close to the original. I've updated the layout with the latest changes.

Here's a quick video I did


I will put up some pics and a better recording when I'm finished boxing it.. Waiting for my C10K pots to arrive...

EDIT. Btw.. I think 50K log is a better value for the volume pot. It lets more volume through, making it alittle louder. The gain pot could also be exchanged with a lower value (like 20K or 50K for a better sweep (it won't effect the range, just the sweep), so experiment and choose for yourself. :)

cheers
/ Fredrik

[Geiri]

I've built the circuits for this and I will be trying it out soon-ish. I'll let you know how it turns out!

[Freppo]

Cool

Just a heads up, if you have problems with oscillation, try a buffer in front of the circuit. It worked for me. The original is buffered, but that section is missing from the schematic I did the layout from.

I ended up using a Klon buffer and these transistors: (to get as much gain as the original)
Q1: 2N5457, Q2: 2N5089 (flipped 180 degrees), Q3: 2N3906

Good luck
/ Fredrik

[Geiri]

Thanks for the heads up! I'm about to tackle this pedal now so I better just include the buffer anyways to be sure. I'm also going to try your transistor combo and see how it turns out.

Cheers!

[Geiri]

Here's my finished build:



I used the same transistors you mentioned except I didn't have 2N5089 so I used 2N5088 and it sounds good. I tried other higher gain transistors and it didn't sound any different to me. I used the Klon buffer before the circuit like you suggested but I didn't try without it.

The pedal sounds great but I'm not sure how close it is to the original because it's been years since I tried one and I can't do an A/B but it sounds convincing to me.

I'm doing a demo of it tomorrow and I'll post it here.

Cheers for the layout man!

[cylens]

My favorite Converge album

[Freppo]

Great work Geiri, it looks awesome!
I'm looking forward to the demo :)

cheers
/ Freppo