Dearmond Rhythm Chief 1100

[rjb]

I'm looking for the original circuit. If you have a proper schematic I would appreciate seeing it...

What I had was a "best guess" schematic I drew based on Belwar's photos. Sorry not to accommodate, but I don't think it's worth searching- given (as I've mentioned) that the G&L circuit works better.

But if you are set on recreating the DeArmond control box, I think that Belwar's photos and David's sketch provide enough information.

You can't always get what you want
But if you try sometime you find
You get what you need

I haven't seen David's schematic.

Sketch, not schematic.

I'm not sure if that thing at the top is supposed to be a switch or the signal input.

It's a latching pushbutton switch.

...there's no signal input on the diagram.

As you can see in the photos, the pickup cable was hardwired between the wiper and and the shell of the volume pot.
Note also that there is no wire connected to the output jack's ground lug, because DeArmond depended on continuity to the metal enclosure to provide signal ground- a practice which I think you have discovered is not always "best".

The sketches of the 2-tap pots aren't particularly clear either.

Um, the wiper is in the middle.

That sketch should have been drawn with a crayon.

Maybe it was. What's your point?

Refs:
Belwar's photos: http://music-electronics-forum.com/t15107/#post120793
David's sketch: http://music-electronics-forum.com/t31838/#post293011
G&L S-500 "Wiring Diagram" (actually a Schematic): http://music-electronics-forum.com/a...patrician-.jpg

If you still need a Rhythm Chief schematic: Take the S-500 schematic. Erase the pickups, SW1, SW2, and C3. Replace the "bass" pot with a normally closed latching pushbutton switch. Change the component values to those in David's sketch (perhaps omit the .005uF treble bypass cap, which is absent in the photos). Then attach the pickup at the circuit output (wiper of the volume pot) and take the output where the selector switch used to be ("top" of the tone pot).

-rb

PS:
Directions for the DeArmond Rhythm-Chief (F hole) Guitar Microphone
The rhythm switch acts as a filter, eliminating low frequency reproduction and permits the playing of rhythm without the usual masking effect. In order that the rhythm switch may operate most effectively, the tone control must be in the treble position.

[bob p]

My apologies to David for the crayon comment. I thought the sketch came from an end user who wasn't familiar with electronics.

Refs:
Belwar's photos: http://music-electronics-forum.com/t15107/#post120793
David's sketch: http://music-electronics-forum.com/t31838/#post293011
G&L S-500 "Wiring Diagram" (actually a Schematic): http://music-electronics-forum.com/a...patrician-.jpg

Part of the problem making sense of this is that I didn't encounter both of your photos in the other threads. Only one of them had been posted, and without the second view its not possible to see everything. The links to the more complete photos are helpful, thanks.

Looking at them it appears that the sketch and the photographs are not of the same circuit. The real Rhythm Chief control box had 3 caps in it, as does David's sketch. Your photos show a circuit that appears to have been modded. It has only two caps. Something is missing. The fact that the circuit isn't the same doesn't simplify the analysis.

What I had was a "best guess" schematic I drew based on Balwar's photos. Sorry not to accommodate, but I don't think it's worth searching- given (as I've mentioned) that the G&L circuit works better.

Worldwide, the jazz musicians who are looking for the Dearmond box schematic are having problems finding an accurate schematic of the original circuit. The best information out there seems to be that sketch of David's. People are posting it without linking to David's thread, which means that David isn't getting credit for having drawn it. It's also not being accompanied by both of your photos, which would have been helpful. Thanks for posting all of the references together.

Unfortunately I was having trouble making sense of the sketch because it's drawn using non-standard representations and the photographs haven't always been accompanying the sketch in online posts. That made it difficult to disambiguate the sketch.

Just like you made a "best guess" at the circuit, everyone else had been forced to speculate about the circuit as well. That surprises me. I would have thought that a schematic of the original circuit would exist somewhere. Maybe it does, and the problem is that whoever has it just isn't sharing it. As a result, people are forced to guess because the information is being withheld.

I hate to think that anyone looking for the authentic circuit should have to guess about something like this. I would have thought there would be an accurate schematic somewhere. I also hate to think that someone looking for the original circuit should have to bow to the better judgement of someone who professes to know what's best for them. As you can imagine, the last thing that a person who is looking for the original schematic wants to hear is, "Here use my circuit instead, it's better." We've all heard things like that before.

As you can see in the photos, the pickup cable was hardwired between the wiper and and the shell of the volume pot.

I'm not following your use of "between." It must be a semantic mental block on my part. I only see two terminals in the left hand pot in the sketch, and I can only see two terminals in the corresponding pot in the photographs. In the photo one of the terminals is obscured behind other parts. I'm guessing that your use of the word "between" is meant to imply that the hot terminal is connected to the wiper, and the shield is connected to one of the pot's fixed terminals which is grounded to the case.

If you still need a Rhythm Chief schematic:

well yes -- that's why I'm here -- for the original schematic.

the wiper is in the middle.

Regarding the sketch -- I understand that it was probably drawn quickly and wasn't intended to become the world's reference standard, but that seems to be what it has become. Some of the notations aren't exactly conventional which adds to the confusion. I've never seen anyone represent pots with the two outer poles in their normal positions, with a wiper terminal being located as a blob on the other side of the rear of the case. That representation makes that connection look like a pot case grounding point, as if the .005 cap was being grounded to the case. What's also confusing is that while the volume control in the sketch is located on the left side of the layout (just like the photo) the order if the lugs on the pot are reversed in the sketch so they don't match the photo. This isn't a case where the perspective changes depending upon whether you're looking at the pot from above or below, the layout diagram appears to have a mistake in it where the terminals are reversed. Just another one of those little bugs that makes the analysis more difficult and time consuming than it needs to be.

[rjb]

Note: Having seen too many contradictory potentiometer terminal numbering systems, I'm going to use these naming conventions in this discussion: CCW, wiper, CW.

Bob, I think you are over-thinking this. It ain't rocket surgery.
In the R.C. control box, you've got three controls- volume, "rhythm" (bass cut), and "tone" (treble shunt) - in that order.

Volume: There are two standard ways to wire a guitar volume control. You can wire it like a Les Paul (ground to CCW, pickup to CW, output at wiper), or you can wire it like a JBass (ground to CCW, pickup to wiper, output at CW). In either case, you may install a "treble bleed" capacitor between the wiper and CW lugs.
In the RCCB, you have a 1Mohm volume pot, wired JBass style. It may or may not also have a .005uF treble bleed capacitor.

Rhythm: This is just a series (coupling) cap between the Volume & Tone controls, shunted by a pushbutton switch.
When the switch is closed, the cap is shorted and does nothing.
When the switch is open, the cap passes treble and blocks bass frequencies. Smaller cap -> more bass cut. The RCCB uses .001uF.

Tone: Standard guitar tone controls shunt highs to ground via a capacitor in series with a variable resistor. The "variable resistor" is always taken between the CCW and wiper lugs of the pot. The CW lug might float, or it might be jumpered to the wiper. The capacitor might be connected to either the CCW or the wiper lug of the pot. Either the capacitor or the variable resistor end of the series combination might be grounded. The particular configuration usually doesn't much matter.
As shown in the sketch, the RCCB uses a .02uF capacitor in series with a 400K (500K -20%?) variable resistor, with the capacitor grounded and output taken at the CCW lug of the tone pot.

Note that part of the reason the RCCB is so hard to decipher is that the metal box is used as signal ground in places where prudence would dictate use of a ground wire.

Part of the problem making sense of this is that I didn't encounter both of your photos in the other threads.

Not my photos. Belwar's photos.

The real Rhythm Chief control box had 3 caps... as does David's sketch. Your photos show... only two caps. Something is missing.

The missing cap is the .005uF treble bleed between the volume pot's wiper and CW lugs. I've never seen an R.C. control box in person, and can't say why the cap is missing in the photo. Perhaps there was more than one version of the control box. DeArmond was never known for consistency.

...As a result, people are forced to guess because the information is being withheld.

Yea, sounds like a conspiracy.

I'm not following your use of "between." ...I only see two terminals in the left hand pot in the sketch, and I can only see two terminals in the corresponding pot in the photographs. In the photo one of the terminals is obscured behind other parts. I'm guessing that your use of the word "between" is meant to imply that the hot terminal is connected to the wiper, and the shield is connected to one of the pot's fixed terminals which is grounded to the case.

In the sketch, the left hand pot- although unconventionally represented- has three terminals.
In the photo, it appears to me that the hot wire is connected to the wiper, the shield is soldered to the pot's case, and the CCW terminal is bent either up to the pot case or down to touch the metal box!

Regarding the sketch --
...with a wiper terminal being located as a blob on the other side of the rear of the case. That representation makes that connection look like a pot case grounding point, as if the .005 cap was being grounded to the case.

Yes, the pot representations are not conventional. No, the wiper terminals are not soldered to the case.

...the volume control ... the order if the lugs on the pot are reversed in the sketch so they don't match the photo.

Oops, I hadn't noticed that the order of the lugs on the pots are reversed! I just saw what my brain recognized to be a volume pot and a tone pot. That could be confusing to someone who doesn't know how to wire potentiometers!

I also hate to think that someone looking for the original circuit should have to bow to the better judgement of someone who professes to know what's best for them.

Have it your way. Do you want authenticity, or do you want to sound good? Your choice.

-rb

[bob p]

Bob, I think you are over-thinking this. It ain't rocket surgery.

That happens when I get roped into wasting a lot of time analyzing something that shouldn't even require my attention. A schematic would have prevented all of the fuss that's been generated by trying to decipher the sketch, which I have determined contains some discrepancies when compared to the photos.

Note that part of the reason the RCCB is so hard to decipher is that the metal box is used as signal ground in places where prudence would dictate use of a ground wire.

not a contributing factor here.

Oops, I hadn't noticed that the order of the lugs on the pots are reversed! I just saw what my brain recognized to be a volume pot and a tone pot.

that suggests that your attention to detail was superfluous, as if you were taking a bird's-eye view of the circuit.
that's understandable, but a superficial assessment doesn't provide a valid position from which to establish criticism:

That could be confusing to someone who doesn't know how to wire potentiometers!

To be fair, the confusion exists within the drawing, not on the part of the reader. The drawing uses non-standard representation of components, it contains a wiring error and a component discrepancy vs the photos. In this case anyone reading the sketch is being forced to recognize these idiosyncracies and correct them.

Do you want authenticity, or do you want to sound good? Your choice.

My question was never unclear. I specifically asked for the original schematic -- twice -- but I keep getting a different recommendation: use this instead it sounds better.

At the risk of re-re-stating the obvious, I asked for the original circuit to serve as a starting point. If I wanted a different circuit that sounded better I would have asked for that.

Thanks for all of your help. Based on your description of the circuit in the previous post I've gotten the info that I was looking for.

Thanks to David for taking the time to draw-up the circuit sketch, and to Belwar for posting the photos.

[rjb]

Thanks for all of your help. Based on your description of the circuit in the previous post I've gotten the info that I was looking for.

Fantastic. When can we expect to see your schematic?
Or do you intend to withhold the information?

-rb

PS - Now that the scales have fallen from your eyes, do you see why I said the RCCB circuit is the S-500 circuit flipped around?
Some years ago, someone online was selling home-made RCCBs in a stomp box configuration. He claimed it didn't matter which way it was plugged in between the guitar and amp.

[bob p]

Some years ago, someone online was selling home-made RCCBs in a stomp box configuration. He claimed it didn't matter which way it was plugged in between the guitar and amp.

The jazz guys with pickups but not the control boxes have been looking for a suitable repro box for onboard mounting. Not being able to find them they end up making their own stompboxes. Someone has just posted a schematic for the circuit on one of the jazz sites. Those schematics seem to be missing the bright cap on the volume pot and the tone cap differs in value from David's sketch (as does the consensus of photos of the original units).

do you see why I said the RCCB circuit is the S-500 circuit flipped around?

I think it's more accurate to say that the S-500 circuit is the RCCB circuit flipped around.

Fantastic. When can we expect to see your schematic?

Sorry not to accommodate, but I don't think it's worth drawing- given (as you've mentioned) that the G&L circuit works better.

[rjb]

Those schematics seem to be missing the bright cap on the volume pot and the tone cap differs in value from David's sketch (as does the consensus of photos of the original units).

I may be wrong, but it seems that you are still searching the "one true circuit". There may not be one true circuit. DeArmond was never a paragon of consistency. For example, different runs of the same model pickup were made with different coil wire gauges. I have noticed that Belwar's control box used a .047uF +/-20% tone cap and no bright cap. But since you are building your own control box, the thing to do is to pick component values that sound best to you with your own equipment.

BTW, in order to accurately reproduce the Rhythm Chief experience, you must use microphonic coax cable.

I think it's more accurate to say that the S-500 circuit is the RCCB circuit flipped around.

Yes, chronologically speaking.

Sorry not to accommodate, but I don't think it's worth drawing- given (as you've mentioned) that the G&L circuit works better.

Oh, I wasn't asking for myself. Just for society at large. "Information wants to be free" and all that.

-rb

[bob p]

I may be wrong, but it seems that you are still searching the "one true circuit"

Yeah, you're wrong. But I've still enjoyed the several posts of patronizing banter.

I have noticed that Belwar's control box used a .047uF +/-20% tone cap and no bright cap.

As have the others I've seen. They match Belwar's photo but I haven't encountered one yet that matches the sketch.

But since you are building your own control box, the thing to do is to pick component values that sound best to you with your own equipment.

thanks. i never would have thought of that on my own.

[rjb]

Yeah, you're wrong. But I've still enjoyed the several posts of patronizing banter.

Yes, it has been rather fun, hasn't it? :grin:

They match Belwar's photo

Hey, where'd you get that pic? You've been withholding information!

OK, now I think we can really put this puppy to bed.

Two out of two specimens have no bright cap on the volume pot.
The "new evidence" clearly shows the physical configuration of the tone circuit: Tone pot CCW to ground; wiper & CW to .047uF cap; cap to output. (That was a detail I couldn't quite make out in Belwar's photos.)
Output at the junction of the two capacitors.
I think we've got our schematic mapped out with close to 100% confidence.
Let's not tell anyone.

but I haven't encountered one yet that matches the sketch.

Picky, picky, picky.
The cap values may be a bit off, but (if you have the intuition to reverse the order of the pot lugs) the big picture is there:
volume pot -> bass-blocking cap shunted by pushbutton switch -> tone control.

BTW: You may get noticeably less noise if you configure the tone circuit as in the sketch, and use a foil type tone cap with the outer foil tied to ground, than if you configure the tone circuit as in the original RCCB.

thanks. i never would have thought of that on my own.

You are quite welcome.

Hey, PM me if you need some NOS microphonic coax.

-rb