Carl Martin - Quattro  [schematic]

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Bernardduur
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Post by Bernardduur »

So, I got this unit in for some repairs and some mods; the overdrive sounds pretty much like a Carl Martin, and for the owner it was not good enough.

The unit gives you a compressor, an overdrive, a chorus and an echo

the unit runs on + and - 12V, 9V and 5V
The compressor is a THAT4301 compressor which you can find on the net pretty easy
The overdrive is a standard Carl Martin Overdrive
The chorus is a classic kind of chorus
And the delay is a PT2399 echo with tap tempo

I don't really like the OD and the delay..... the delay is too edgy for me and has some lofi character to it. I'll add some pics later!
PSU.JPG
Switches.JPG
Compressor.JPG
'No more....... loud music.......'
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Bernardduur
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Post by Bernardduur »

Overdrives.JPG
Chorus.JPG
Echo.JPG
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Bernardduur
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Post by Bernardduur »

DLY.JPG
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arjepsen
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Post by arjepsen »

Thanks a lot.
Im looking at the tap tempo and echo circuits.
The delay seems like a straight forward pt2399 delay.
I might try to add the tap tempo to the pt80 i build from the GEneral Guitar Gadgets website.
Im a little curious though... Seems like the quattro delay can go up to one second. The pt80 doesnt go that high.
In the pt80 the time is controled by a 50k pot, and in the quattro by the tap circuit, somimpresume the tap circuit just allows for higher than 50k resistance? I wonder if that has any effect on the sound?

Any chance og gutshots???
:popcorn:

Regards
Anders

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Bernardduur
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Post by Bernardduur »

I'll try to add the guts tonight!

The tap on the delay works with that 'ladder' contruction; it can vary the resistance by switching in and out the resistors from 750R to 98.35K

I dunno about the 1s of the Quattro; I know that I found the unit on higher delay times pretty edgy and lofi sounding that was cured by using a shorter delay time. I really disliked the fact that it didn't have a delay time knob and that everything needed to be done by tap tempo....... I'm just not used to tap tempo :). I had the same problems with the red repeat of Carl Martin
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Post by arjepsen »

So, how many different settings/timings will the tap-circuit provide?
I can count 7 obvious settings, but is the circuit able to combine switches?
I guess my question is about how precise the tap circuit is. If its only 7 settings, i guess its not that precise...???

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Post by jhreid »

arjepsen wrote:So, how many different settings/timings will the tap-circuit provide?
I can count 7 obvious settings, but is the circuit able to combine switches?
I guess my question is about how precise the tap circuit is. If its only 7 settings, i guess its not that precise...???
Looking at the values of the resistors in the ladder, I would guess that they represent binary digits. that would be 7 bits or 128 subdivisions if you include 0.

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Post by arjepsen »

Bernardduur wrote:
DLY.JPG
Looking forward to the guts :-)
I'm a little confused about the connection "bubbles" on the cd4520's
Does those cirkles just mean that those pins are connected, or do they signify something else?

Regards
Anders

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Post by arjepsen »

Bernardduur wrote:
DLY.JPG
Also, I think maybe you forgot the power pins on the cd4066's..??

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Post by Bernardduur »

arjepsen wrote:
Bernardduur wrote:
DLY.JPG
Looking forward to the guts :-)
I'm a little confused about the connection "bubbles" on the cd4520's
Does those cirkles just mean that those pins are connected, or do they signify something else?

Regards
Anders
The bubbles are in the datasheet of the IC; the numbers on the bubbles are the pins of the IC they are connected to!
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Post by Bernardduur »

arjepsen wrote:
Bernardduur wrote:
DLY.JPG
Also, I think maybe you forgot the power pins on the cd4066's..??
Yes, I see..... must add that!
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Post by arjepsen »

Bernardduur wrote:
arjepsen wrote:
Bernardduur wrote:
DLY.JPG
Looking forward to the guts :-)
I'm a little confused about the connection "bubbles" on the cd4520's
Does those cirkles just mean that those pins are connected, or do they signify something else?

Regards
Anders
The bubbles are in the datasheet of the IC; the numbers on the bubbles are the pins of the IC they are connected to!
Ah,ok. I found it now.
I think it looked differently in another datasheet I looked at.

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Post by arjepsen »

Bernardduur wrote:I'll try to add the guts tonight!
Any chance for them? :D

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Post by Jarno »

Fascinating stuff, the delay being done with a PT2399, combined with a compander, and switched resistors to set delay time, certainly different from the more common schematics seen.
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Post by Dirk_Hendrik »

Fascinating indeed to see how they spend a relative fortune on board space and components to avoid having to learn how to program a 1 euro uController. IMHO this is a prime example of very poor engineering.
Sorry. Plain out of planes.

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Post by Winther »

Or a boss who did not wanna spent any funds on it ;)
Let us just say it was never quite finished.

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Post by clintrubber »

Bernardduur wrote:I'll try to add the guts tonight!
...
I really disliked the fact that it didn't have a delay time knob and that everything needed to be done by tap tempo....... I'm just not used to tap tempo :). I had the same problems with the red repeat of Carl Martin
Thanks for the schematics, and interesting to see the indeed old school approach to the tap tempo.

Curious if the latest Red Repeat version ('2016') still spends all these components.

(As known, the 'first' Red Repeat (in the big but nicely shaped box) had a simple time-knob, no tap tempo)

The latest version has modulation as well.

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Post by PedalJerk »

Sorry for the necro-bump, but I'm trying to wrap my head around the clipping section of the Drive circuit. What's going on with the bridge rectifier in the opamp loop? And is D1 a Zener? What does this do compared to, say, the traditional anti-parallel "soft clipping" diodes I'm used to seeing in OD circuits? I've seen this weird diode arrangement in a couple Carl Martin schematics posted online. :scratch:

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Post by clintrubber »

PedalJerk wrote:What's going on with the bridge rectifier in the opamp loop? And is D1 a Zener?
It's not too uncommon, thought to have seen it in Marshall (tube!) amps form long ago already as well, and they might not have been the first.

Just follow the direction of the diode-arrows for a positive signal, and then again for a negative signal at the opamp-output, and count the amount of diodes you pass for each signal polarity.

So it's simply some saving of diodes. The circuit shown is equivalent to six diodes (two strings of three, anti-par.) but Carl now only has to buy five...
or in case of using a bridge-rectifier, only has to insert/place & solder two components.

D1 could indeed be a zener, or anything of the other diode-types.

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