Opamps & Studio Electronics

Shootout to Red Dot, SL-1731 / stock modern API2520

Red Dot Opamp

SL-2520 Red dot opamp
SL-2520 Red dot opamp
Two versions of the SL-2520 were designed as replacement opamps for vintage console restoration. The vintage or “red dot” version is built to match the Huntington and Melville NY opamps from the 70’s. The clean, or “blue dot” version, is made to sound like the newer 2520 opamps. The original intent for making two versions was to use the colored vintage opamps, in console mic pres, and the cleaner versions in the summing amps of vintage consoles. Since then, thousands of SL-2520’s have found their way into  DIY projects, commercial studio gear, and large format consoles. A great number of SL-2520’s are in use everyday in major market studio consoles including Nashville and New York. Upgrades – The SL-2520’s utilize the same circuit as the highly desirable vintage opamps from the 70’s but with modern components. (The original transistors are no longer manufactured) Modern transistors are generally quieter and faster than their vintage counterparts. Through exhaustive lab and listening tests, I was able to match the distortion characteristics of the vintage and modern opamps to achieve a sound that has been deemed “indistinguishable” from the originals by vintage console owners. $65 each.  Quantity price breaks available.  Please use contact form to inquire about ordering, or email; scott@scottliebers.com

SL-1731 "Melcor" opamp

A faithful recreation of the one that started it all. Melcor engineers formed API and used the 1731 as a basis for the ever popular 2520.
True to the original 8 transistor 1731, medium stage output transistors are used. Medium stage transistors have a faster slew rate than power transistors which translates into a tighter bass with more punch. The 1731 still has some color to the overall signal due to added second order harmonic distortion. Sadly, not many original Melcor 1731s have survived due to the weaker output transistors. My design deviates only to parallel a pair of each complimentary output pair to share the current drive and heat dissipation required. The slew rate stays the same, but the load duties are now shared half each transistor to make them more robust and last longer.

$65 each.  Quantity price breaks available.  Please use contact form to inquire about ordering, or email; scott@scottliebers.com

 

SL-2510

 SL-2510’s were designed to improve reliability for an on-air music production 32 channel Legacy console. Within 4 years, many of the stock 2510 opamps started to fail, especially in the EQ sections. I blame the failures on the potting compound used to enclose the guts of the 2510’s. This potting compound has a consistency similar to a pencil eraser. It makes a nice insulation to bottle in the heat
generated by the output transistors eventually cooking them.

Upgrades – Additional longevity improvements were made to the output stage. By putting the output stage on a separate PCB, heat sink pads could be added and larger output transistors are used to dissipate heat better. A chemical fuse feeds the collectors of the output stage allowing the SL-2510 to drive a dead short without damage.  In addition to having better heat dissipation, SL-2510’s are repairable should a failure ever occur.

$70 each.  Quantity price breaks available.  Please use contact form to inquire about ordering, or email; scott@scottliebers.com

Blue Dot opamp

Modern version of the 2520 opamp.  The SL-2520 Blue dot has a faster slew rate and cleaner sound vs. the vintage 2520 and Red dot SL-2520.  Blue dots were created to match existing opamps in consoles and multi-channel units to alleviate total replacement of opamps.

$65 each.  Quantity price breaks available.  Please use contact form to inquire about ordering, or email; scott@scottliebers.com

 

SL-2520 blue dot
SL-2520 blue dot
sl-2520 blue dot