Classic Audio Products VC528 Build

After reviewing my in-depth photo documentation of several microphone preamp builds, Jeff Steiger, the owner and CEO of Classic Audio Products of Illinois decided to officially employ my photo-documentation services for his VC528 kit.  This post utilizes the photos I made from the official build documentation.

The VC528 is a unique 500 series or 51X module in that it is a "go-between" design.  While it is common to find preamp circuits from a variety of vintage consoles in lunchbox form, this module  re-creates the rest of the channel strip circuit of the vintage API console all the way out to the channel fader.  Many have referred to this module as "audio bacon" because it can be inserted after or before any other outboard device and add the analog goodness of a full frame vintage console at a fraction of the cost and space.  VC528 allows for a wide range of experimentation with gain staging when inserted into the signal chain because you can drive whatever previous device hotter or softer than normal and adjust for proper gain with the VC528 before hitting the recorder.  Another common use for the VC528 is inserting a pair on the main stereo mix bus.  For this application, Jeff offers stereo kits with closely matched resistors for optimal consistency of the left and right channels.

In this post, I will show a complete VC528 kit build from start to finish.  An assembly aid document as well as bill of materials, trouble-shooting tips, and calibration procedure can be found here.

Basses for Newbies - Pickup Shootout

Ever since we ran into the unfortunate "SX Effect" distortion problem in the stock SX pickups, I've been on a quest to locate a suitable replacement pickup for the basses for newbies builds.  While it could be argued that the stock pickups work just fine for a beginner, one of my design goals is to deliver a bass capable of holding up to all types of situations a working musician may encounter.  A real working tool that can be a long-term bass and not require upgrade (at least on the basis of playability or sonics). . . well, ever. 

Basses for Newbies - Bass #6

Let's get #6 started. . . back to SX's . I've been doing a lot of jazz basses lately, so I figured I'd try something different with a P/J.

This bass was the one that's started this whole basses for newbies ordeal. It's been sitting in the studio making its way onto various projects that come through. I leveled the frets already, but think I need to take another look at the level job and probably cut more fall-off. Hopefully this one will be straight forward and fast. Mainly, this bass makes noise so I will try to shield and re-wire. . . and throw in neck inserts. I was debating the series/parallel switch on a P/J, but I think I'll put that in as well just for kicks and giggles. . . see what "super phat" mode sounds like.

Thinking about trying out a GFS p-bass pickup on the neck position and see if the shielding alleviates the hum issues on the stock bridge position SX pickup because the "SX effect" only seems to happen on the neck pickup. If it still hums, I'll have to look into a split coil bridge pup.

IJ Research F76 Compressor Build

The Universal Audio 1176 FET compressor originally released in 1968 is broadly recognized as one of the all time great audio compressors.  It seems every major studio has a few of these in their outboard racks and the particular way the FET circuit compresses is distinctive and a "familiar" sound due to the widespread use of the 1176 through the years in the industry.

The I.J. Research F76 is a 51X format FET compressor designed around Universal Audio's revision F 1176 with a few very useful added features most notably, the addition of a 2:1 ratio, a side-chain high pass filter, and relay controlled true bypass.  The kit also allows for a myriad of build options.

Igor Kapelevich based in Haifa, Israel can only be described as a prolific designer, and he is the mastermind behind the F76 compressor.  Igor's primary business is building complete turn-key audio devices for various studios worldwide and his custom work is not cheap, but he is very active in the DIY community and makes his partial kits and PCB's available for purchase as a side business so that DIY people have an opportunity to build some fantastic sounding pieces of audio gear at very reasonable prices.  For support and technical questions regarding this project, please refer to the official support thread.  To purchase PCB's and font panel/hardware kits check out the IJ Research webstore.  Complete kits may be available again from time to time depending on Igor's current stock of parts.  In this post, I will try to show a complete build from start to finish.

VP312DI Microphone Preamp Build

One preamp that was very interesting to me from my initial DIY research was the VP312DI kit from Classic Audio Products of Il.  One of the main reasons I wanted to try this kit was the feature set seemed very conducive to live use for bass guitar.  It has some really cool modular features that allow for a wide range of customizations.  In particular, this preamp has easily detachable modules to allow for 4 completely different flavors of DI.  It also has a built-in switch to bypass the DI module and inject the signal directly into the opamp which yields a different sound option that is built-in and always available.  In addition, the opamp is a standard footprint 2520 opamp.  Because this preamp comes in a full 51X Alliance standard configuration, not only are API-type +/- 16V opamps accepted, but a number of +/- 24V opamps can also be used.  The DI section of this kit also has a selector switch for 16V and 24V operation depending on the module being used.

So, in short, there are a mind-boggling array of possible configurations for this preamp kit that can all be changed quickly and without soldering.  For this build, I will explore a few of them.

opamps:  GAR2520, APP2520E (+/- 24V)
DI modules:  FET DI, Picatron passive transformer DI, and the IC chip DI

The current revision of the VP312DI preamp has a new option on the PCB for stepped resistors on the gain knob, so you can now choose between the constant variable Bourns pot (as depicted in this older revision build) and the Grayhill switch with stepped resistors when purchasing this kit.


There is no in-depth step-by-step assembly guide for this build, but a lot of critical build information is consolidated in the official support thread on the http://www.groupdiy.com forum.  All of the critical build documents (schematics, bill of materials, and assembly guide) are also sent via email upon purchase.  In this post, I will attempt to detail every step of the VP312DI kit build.

Basses for Newbies - Bass #5 (part 2)

This is the continuation of the Bass #5 build.

We start out this installment with new electronics being installed.

Basses for Newbies - How to Install Copper Shielding Foil

It seems like there are a lot of folks out there with questions about how to shield the control cavity and pickup routes. I figured I'd take some more in-process photos on this one and see if it's helpful. This may very well not be the best or cleanest way to do this, but it is "one" way that works for me.

Let's start with the hardest part. . . the pickup cavity. I start from the bottom of the route and work my way up, so the first step is to make our bottom piece. I measure a piece of 50mm foil to the length of the pickup with an extra ~1/4" on top and bottom.