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Scott Liebers Labs - Op Amps and Outboard Gear. SL-2520 - Two versions of the SL-2520 were designed as replacement opamps for vintage console restoration.

Scott Liebers Labs - Op Amps and Outboard Gear.

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, many SL-2520’s have found their way into numerous DIY projects, EQ’s and even newer Legacy consoles. A great number of SL-2520’s are in use everyday in major market studio consoles including Nashville and New York. Some customers have mixed 2 clean channels and 2 colored channels in multiple channel mic-pre’s to take advantage of different sonic characteristics within the same circuitry of a mic pre.

Eden Microphone Preamplifier. This is the Eden Microphone Preamplifier from Expat Audio.

Eden Microphone Preamplifier

It comes are a completed module that only needs to be hooked up. In fact, all it needs is power, input, output and a gain setting resistor. It's assembled and tested here in Texas, USA. Performance It has flat THD+N at 30dB of gain as low as 0.003%, all the way to 30kHz (higher I believe - but the audio test kit isn't quite up to it). At 60dB of gain (max setting) the THD+N is still very impressive at 0.04%. Documentation Users Guide: Available for download here: Expat Audio Eden Mic Pre PG2.0 Users Guide. How to make custom resistors. How to make custom resistors.

How to make custom resistors

Or individually hand trimmed by frictive attrition (tm) It is not generally known that you can customize a resistor fairly easily. The technique was taught to me by my late farther. The Philbrick Archive. Deciphering Electrical Characteristics in an Op Amp Datasheet. The Operational Amplifier (Op Amp) is often the key analog gain block in acquiring and scaling real world signals in any data acquisition system.

Deciphering Electrical Characteristics in an Op Amp Datasheet

To predict system accuracy when using op amps it is important to understand the op amp data sheet and how individual specifications affect both the DC and AC transfer accuracy through the op amp. Both DC and AC limitations will be discussed in detail. Sboa054.pdf (application/pdf Object) Sboa059.pdf (application/pdf Object) Sboa067.pdf (application/pdf Object) Opamp Test and Design Board. Opamp Design and Test BoardRod Elliott (ESP) Introduction Opamps are wonderful little building blocks, but quickly building a test circuit is a real pain.

Opamp Test and Design Board

Most people will use a "breadboard", one of those plastic blocks with holes and connections, but I have found them to be a complete pain in the backside. OA10 Discrete Op-amp. Hairball Audio, LLC - DIY JE-990 Discrete Operational Amplifier. One of the key features of the Lola Microphone Preamplifier is the inclusion of two 990 op-amps. Deane Jensen’s now famous JE-990 paper describing the design, testing, and theory behind a powerful ultra low noise operation amplifier, was first introduced in the February 1980 AES journal. The design started with the LM394 dual super matched transistor as the input device. The LM394 is actually a monolithic device consisting of two pairs of 50 transistors connected in parallel to eliminate random variations in the individual devices. Quad Eight CA27 Dual Op Amp « Orphan Audio. JLM Hybird Opamp Kit. [header.htm] JLM Hybrid Opamp JLM Hybrid PCB & full PCB parts kit Parts List.

JLM Hybird Opamp Kit

MCI 2002 Opamp - NEW: SystemsStore.com. How transistor works, an alternate viewpoint. Voltage-driven charge-flows First of all, you must abandon the idea that current travels in transistors or flows inside of wires.

how transistor works, an alternate viewpoint

Yes, you heard me right. Current does not flow. Electric current never flows, since an electric current is not a stuff. Electric current is a flow of something else. Since a current is a flow of charge, the common expression "flow of current" should be avoided, since literally it means "flow of flow of charge So what flows inside of wires?

The stuff that moves within wires is not named Electric Current. Second: the charges found within conductors do not push themselves along, but instead they're pushed by "potential difference;" they're pushed by the voltage-fields within the conductive material. Third: have you discovered the big 'secret' of visualizing electric circuits? The OP-AMP. Before we describe anything technical, let's see one in action.


An op-amp can be connected to a single voltage rail (called UNIPOLAR SUPPLY - 0v to Vcc) or a dual voltage rail (called BIPOLAR SUPPLY +/-Vcc). When connected to a single voltage rail, the output can go from 0v to approx full rail voltage. The OP-AMP has two inputs. A "+" input for non-inverting and "–" for inverting. When the "+" input is a few millivolts higher than the "–" input, the output goes HIGH. If the "–" input sits at half rail voltage via two equal-value resistors, the "+" input must go above ½V for the output to go HIGH, as shown in the animation below: Classic Audio Products of Illinois. The gar2520 DOA Full Kit Bundle is a full and complete parts kit with everything required to complete the gar2520 Discrete Operational Amplifier build.

Classic Audio Products of Illinois

This board has been designed by Gary Barnett of Barnett Industries. Gary has built upon the reverse engineering work of Peter Lazaro, better know as “Peter Purpose”. Scott Liebers Labs - Op Amps and Outboard Gear. Gar2520 Discrete Opamp Kit. Quote: Originally Posted by skydog a couple of questions...will there be a pre built option available?

gar2520 Discrete Opamp Kit

If so how much? Hey skydog, When Gary and I developed our "relationship" regarding his opamps, I agreed that I would never assemble and sell them myself. I do also have Scott's SL-2520 red and blue dot available with the same add to VP26 method. And what do you feel are the sonic differences and similarities between the gar2520 and the sl 2520 red and blue dot versus old/new school api?

Well...as usual...this is a slippery slope and very subjective to each individual.