The SC-1 Mic Preamp is a THAT 1510/1512/SSM2017/SSM2019/INA217 based Mic preamp with phantom power, DC servo and Balanced line output driver.

Rev.1.00 PCB Design for the SC-1 Preamp

Introduction

The THAT 1510 is a high performance audio preamplifier suitable for use in microphone preamp application. It is pin compatible with the now discontinued, Analog Devices SSM2019 and SSM2017 IC chips, and the Texas Instruments INA217 and INA163 mic preamp chips.

Designed from the ground up in THAT’s complementary dielectric isolation process and including laser-trimmed Si-Chrome thin film resistors, the THAT 1510 improve on existing integrated microphone preamps by offering lower noise at low gains, wider bandwidth, higher slew rate, lower distortion, and lower supply current. The parts feature internal ESD overload protection on all critical pins.

In short, the THAT 1510 provide superior performance in a popular format at an affordable price.

Features

* Low Noise:
1 nV/ ÖHz input noise (60dB gain)
34 nV/ ÖHz input noise (0dB gain) (1512)
* Low THD+N (full audio bandwidth):
0.0005% < 40dB gain
0.005% @ 60dB gain
* Low Current: 6 mA
* Wide Bandwidth: 7MHz @ G=100
* High Slew Rate: 19 V/µs
* Wide Output Swing: ±13.3V on ±15V supplies
* Gain adjustable from 0 to >60dB with
one external resistor
* Industry-standard pinouts

Yes, build your own pads. By pads, I mean "attenuation pad."  These are devices or circuit meant to attenuate or insert a loss in your signal path.

There are 2 kinds of pads you can use... The first is called a "T" pad and is mainly used for unbalanced lines.  The second is called an "H" pad and is mainly used for balanced lines.

We'll be building an "H" pad.

If you want a -10dB attenuation on your signal, use the values 150ohms for Ra, and 430ohms for Rb.  These values are meant for a 600 ohm line, which is the impedance typically used in pro gear.

For other values, see table below:

dB Loss	Ra	Rb
1	8.2	10K
6	100	820
10	150	430
20	240	120
40	300	12
50	300	3.6

This is a DIY Signal Isolation/Unbalanced to Balanced Converter Box. I'm using high-quality MADE IN USA Audio Output transformers to create this SI/UnBalanced-to-Balanced (or Balanced-to-Unbalanced) Converter Box. In addition, a Ground Lift switch is provided.

On this picture, you can see the 4 TRS jacks (2 per channel x 2 = 4), the 2 large audio output transformers, and the ground lift switch in the middle.

And this is the picture of the finished project. The switch on top is the GND LIFT switch.

The jacks from left to right, are Unbalanced in/out, Balanced in/out (for Channel 1), Unbalanced in/out, Balanced in/out (for Channel 2).

The unit can perform as a Unbalanced to Balanced converter, or as a Balanced to Unbalanced converter.

It's done... some pictures.  Using my custom PCB for the power supply, and an MCI output transformer on the outputs to convert it to balanced outs.

It works... sounds nice and clean!  The EQ lets you sculpt the sound nicely. No hum, no noise. It's great!

I designed a new PSU for people who'd like to rack those Yamaha PM1000 channel strips.

The Yamaha PM1000 are usually called Japanese "Neves" because of a similar approach in design. Just like the Neves, this is all discrete transistor and uses an input transformer and output transformer.

The EQ section is especially sweet because there is not a single IC on this preamp. The EQ section uses inductors and capacitors... totally analog manipulation and shaping of your frequency. (circa 1974)

I've tested them on drums and vocals and they really make the sound FAT. The EQ section shapes your sound anywhere from slight barely noticeable to extreme gain/reduction. Bass frequencies are solid. Of course, being an analog EQ, it is not as precise in shaping the sound as IC chip Equalizers. But the curve is smoother I would think.

So if you're racking a PM1000 strip you bought from eBay, this PSU will be perfect for you. Output is +44VDC and +48VDC for the Phantom Power.

I'm having prototypes built. If you're interested, email me.

Screenshot:

PCB Rev.2.00



The new PCB designs will be smaller and double-sided measuring 2.25" x 2.25" 

I don't have this mass-manufactured, so I'm selling it at a low price just to recover some of my costs.  $20 each.  Email me first  before ordering. Thanks.