Here’s one more from the ROG archives. Apparently amazing sounding OD/dist. Should be doable in 1590B, if you feel brave enough with the rotary 🙂
From ROG: Back in the mid-90s, the Matchless DC/30 became one of the first boutique
amps to hit the market. It excelled at clean tones, as well as thick
Vox-like overdriven lead sounds.
There is good reason for the similarity in sound to a Vox amp. The lead
channel of the DC/30 appears to be a modified Vox AC30/4. The AC30/4 amp
featured the EF86 pentode preamp tube, just as the Matchless design.
runoffgroove.com set out to capture the lead sound of the Matchless DC/30
amp, using the technique developed by Doug Hammond for his excellent Meteor circuit.
We opted for a MOSFET to replace the EF86 tube. The MOSFET has better
gain and fidelity attributes than the JFETs we normally use. We used J201
JFETs for the remaining two stages.
We’ve named this circuit the Matchbox.
An item of interest in this circuit is the odd-looking Tone control.
This
is in some ways similar to the FAC control on old Orange amplifiers.
The
sound is “thinnest” on setting A, and gets thicker as you progress
through the settings. The Cut control acts as a simple Low Pass Filter.
As you
turn it counter clockwise, it will roll off some of the treble
frequencies.
We departed from the schematic a bit here. We used a 10n cap where the
amp used only a 2n2. The reason for our deviation is to achieve a more
dramatic effect.
NOTES:
-Try using a different MOSFET for the first stage. A 2N7000
sounded a bit “tighter” than a BS170. BS170 had a nice “loose” sound.
-Any N-channel MOSFET can be used, but as always, pay close attention to the pinout.
-Try to use all metal film caps in this circuit. It really seems to add to
the smoothness of the sound. Ceramic caps or “greenies” will work fine, but you will probably notice a bit more “grainy” sound.
-A 12v Zener diode can be used in place of the LED used for static
protection of the MOSFET.
-Philip Miller Tate (a.k.a. Ge_Whiz) found the Cut control to be
quite subtle when using the stock values. He reports that substituting a
47nF capacitor and 50k-B pot provided a much more effective control.
-You can use other JFETs, but be warned! The middle stage may not bias
correctly or have enough gain to distort. Try other transistors at your
own risk. PLEASE do not post on Aron’s Stompbox Forum
with a complaint about the circuit does not working or sounding good
when you do not use the specified components. You can always purchase
J201 FETs from our friend, Steve Daniels at www.smallbearelec.com, who will ship to anywhere in the world.
