Messages

(incidentally, have you gotten my PM/email from a while back?)

Yes, sorry I will respond today.

Two things come to mind - you diodes are not clipping properly and your op-amp is crapping out at higher gain...or R8,R9 or R10 are incorrect. Also, check your VB voltage.

Hey it's an awesome color, though.

Its on its way back.

You definitely did the right thing. Gibson does have a bit of a QA problem as we all know.

Funny story (which I am probably totally not supposed to discuss), but my wife works for Mapex/Sonor and has a colleague that works at Gibson here in Nashville. That employee was just let go after letting a promo photo get out of a guitar with a major chip in the finish. The photo went through several sets of eyes before being released publicly (I feel bad for the guy, honestly...he's not to blame).

That said, they'll pry my SGJ from my cold dead hands...best $500 guitar ever.

I ran into a couple issues on this build.

- When I first tested the built board I had lots of sputter. It sounded misbiased. A quick voltage check confirmed that the VB rail was reading 260mV. I knew my soldering was good so I suspected a dodgy component. I took out the first 47k on the VB voltage divider and started testing. Turns out there was continuity between things that there should not be. So, I was faced with the prospect of doing some desoldering or building a new board. I decided to desolder the 16mm pots and check my work.

After studying the PCB traces on the Eagle brd file I made a guess to where the problem might be - a little via next to pins 3 and 4 of IC1. And, I guessed lucky cause that was the problem - there was a micro bridge somewhere in that area. After running an Xacto carefully around that via I was able to get my VB voltage where it was supposed to be. All in all, it was a couple hours worth of debugging.

(PS not to worry - it's not a board fault as far as I can tell. I checked all the other Merman PCBs with my continuity checker after this and they all came back clean. Pretty sure it was a little hair of steel wool).

- Second issue was I apparently over-sprayed the shit out of the clear coat on my faceplate. So, it's got some texture. But, I kinda like the way it looks.

- Also, I decided to try non-mounted jacks on this build. It turned out to be pretty easy, actually.

I like the Merman - I think splitting the clean and drive pots was a fun idea and useful as well. Mostly, I prefer the Klon for clean settings and the Bottom control really makes the clean boost setting sound huge.

It's center negative. No need for polarity reversal.

Though actually ... R14 and the comp pot could have been combined to be a single pot. The comp pot is the lower leg of the voltage divider. You could use a 10KA, omit R14, and jumper the side touching the op amp to the comp pot's unused leg, though that would still involve twisting the legs.

Yeah that is a good idea!

2kB turns out to work pretty well for the Comp control. I definitely like it better than the 10kB I used. There's still some bunching up at the last 1/4 of the turn but overall it has a good range.

Get your mecha-Klone on with the Merman! I got a partial shipment of micro-controllers last week so I have 45 available.

Also, I added a note in the doc - smallbear does not have reverse-audio plastic shaft pots and the Merman uses a 10kC. There is a link in the doc to Tayda which does have them. You can use 10kB (it's what I used) though it does bunch up the control at the end. If I have time today, I'm going to try a 2kB instead and see if that improves the bunching. The reverse audio taper won't have that problem.

Out of curiosity, just in case (of course), what flavor of JFET does the Tractor beam use? 5952s? J201s? 5485s? Unicorn scented 2n4303s?

No reason, not building a shopping list or anything... I swear I can stop anytime I want...

It will require four matched 2n5952. It also uses three resistor networks to save some space on the board. I'm waiting on a few parts myself!

Yes, you can use tantalum. There are low-ESR tants as well. Just be sure to put them in the right way.

Last question... does a second order low pass filter like this minimize ripple on the DC power more than a simple first order low pass would do?

Or maybe I should ask: "does a low pass filter affect the stability of the DC power minimizing the ripples? Or it just cut off the (noisy) high freq. content of the DC?" 

Actually, I don't know. My gut says no. I'd have to look that up (or maybe we both should!)

One way to look at it - you pay $20, hate the Choral Reef (doubtful) you can easily get your money back selling it. I've paid upwards of $50 for certain BBDs and just recycled them through other projects for years.

One thing I did not explicitly state in the build docs is that the component values of a lot of the VFE products changed over time. You should always use the BOM values (which are duplicated on the build image on the first page over every doc). Ignore the values printed on the silk-screen of the actual PCBs. Much of the time they are the same, but to avoid confusion follow the values shown on the build image.

I will update all the docs with this info.

Two reasons -
Inductors are more efficient than resistors - they don't dissipate heat like resistors.
Inductors give you a two-pole filter instead of the one-pole filter you get with resistors.

To find out more look up LC vs RC filtering

Two things -

1) I fixed the transposed voltages on the HT8950 and indicated to set the Mode switch to position 8 for comparison.
2) I previously stated to set the tab on the Mode switch to pin7 normally and pin8 when doing the up/down mod. This is incorrect. The pin should ALWAYS be set to 8. The 8th step is where you also get the arpeggiator! My mistake...I thought that setting was duplicated in another position and never noticed.