ROG Big Grace help - SOLVED

[John R]

Hi,

I built this one
https://tagboardeffects.blogspot.com/2013/01/runoffgroove-big-grace.html

With the switch in Grace position, it sounds like the lord himself built an amplifier, however neither of the pots have any effect. It's glorious, but would be nice to play at volumes other than full blast. :)

With the switch on Big Daddy position, there's no guitar sound, just occasional little squeals when I turn the knobs.

The switch is connecting and disconnecting the proper poles when switched. Good connections from the switch to the board. The volume pot registers 100K when fully off. The drive pot registers 680R fully off. So somehow the signal bypassing both pots. I xactoed the crap out of the grooves so I don't think thats it.

Here's the transistor voltage readings:
wall wart: 9.38V

IC
1 1.35
2 0
3 0.1
4 0
5 4.42
6 9.39
7 4.74
8 1.54

Q1
D 7.76
S .24
G 0

Q2
D 9.38
S .22
G 0

You can see in the wide pic that I put a DPDT switch in the box to A/B it with ROG Eighteen (once I get it working) in the same box. I sent the 9V+ and the input to the two poles. Is that the best way to go about doing this sort of thing? Would it be better to do input and output? or just one of the three?

Thanks in advance.

John

[Ciaran Haslett]

Hi John...few things I think

You haven't connected Volume 1 to the board.  Is that lug grounded elsewhere?  Can't really see in the pic.
The double ground link under the IC looks broken?  If so the the top leg of the 15K isn't connected to ground.
The cut on the bottom row separating SW3 and SW6 doesn't look like it's completely cut.

Good luck

[John R]

Thanks for the help!

1. volume 1 was NOT grounded! Fixed that and the knobs work.

2. the wire under the IC isn't broken -- it's a jumper that connects to the hole above, so I ran the wire down the hole above and then up through the front in that spot. The connection to the 15K is good

3. i agree that cut looked suspect, but it tests clean. And I dug it out a bit more just to be sure.

So i'm getting volume and drive control, but still no Grace mode. I tried swapping the J201 but no go.

Also, now that I've played it a bit, there's a noticeable phasing effect when I hold long notes -- they phase and then die out. It's kinda cool, but can't be what it's supposed to sound like.

john

[Ciaran Haslett]

The wire connection is connected to the top leg of the 15K...but is the wire also connected to ground?

I don't see the other end of this wire on the copper side jumping to the double link spot under the IC in your pic.  In fact I see a lot of knife marks between these 2 points...almost as if you where trying to remove a bridge here...when you actually need one?

The Grace side is just a FET buffer into a 386 amp.  The 15K source resistor needs to connect to ground or the buffer just doesn't work.

Absolutely confirm this with a DMM on continuity/resistance mode.

Can't comment on the sound of the Drive side other to say that I've tried a few 386 circuits and didn't much care for them.

Let us know if you make any progress.

Cheers

[John R]

That was it! I must have hacked through that wire, thinking "pesky blob...".

Once the 15K was reconnected to ground, Grace mode works, and 90% of the phasing is gone too.

Good eyes!! thank you so much!

john

[Ciaran Haslett]

Happy days lad!  Glad you got sorted.  Let's get the other one going now

[John R]

Yes! Hoping to get back to it today.

You mentioned you're not a fan of 386-based distortions. Any suggestions for 60s/70s Marshall crunch a la early AC/DC, Zeppelin, Aerosmith, Kiss, etc.? I'm playing a Les Paul into a 70s Fender Showman.

Next on my list to try:

Marvel Drive (J201s - yay, more biasing!)
MAudio Crunch Box (LM833)
Nick Greer Sucker Punch (386)
Catalinbread DLS - v1 or 3?
ROG Thunderbird?
Bartolini tube-it?
JCM800 emulation?

Already built the LP Purple Plexi. Sound is so scooped I have to crank the mids to bring life into it. So I don't think that's it.

thanks,

John

[Pavlos]

Hi John

Glad you've got the Big Grace working. My suggestions (In no particular order) would be Marvel Drive, Rockett Animal and Menatone King Of The Britains, they all sound great for those classic Marshall style tones and it didn't take too much time to get the JFET's biased either. Crunch Box has a lot of fans but can't honestly say it does anything for me, I found it to be more of a generic distortion than amp-like, but still probably worth checking out. Can't comment on the others on your list though as I haven't built any them, but ROG stuff is nearly always worth a go (Eighteen is very nice for lower gain old style crunch) and BJFE/Bearfoot/Mad Prof (Honey Bee/Sweet Honey etc) are also well worth checking out.

Regards

P

[John R]

Band and I held a shootout just now in the rehearsal studio between Rockett Animal, ROG Big/Grace and LP Purple Plexi. Les Paul Studio > pedals > Fender Showman, A/Bed with guitar straight into Marshall JCM2000 lead channel (gain on 5).

The winner: ROG GRACE! We liked it even better than the actual Marshall! More mid crunch, plenty of balls and bite. Simply the most "present".

It sure helps to get them up to stage volume, and let 'em breathe.

Thanks for helping me get it running!

John