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VC528 ML2-Litz Entire Bundle
Number of Product Bundles in stock: 10

Click to enlarge

Click to enlarge

To avoid massive build errors, make sure the BOM Revision you follow matches the Revision of the PCB you are building!!

The VC528 ML2-Litz Entire Bundle is a complete kit bundle that contains most all of the parts and components required (sans opamps) to complete a VC528 ML2 module. The ML2 is physically and electronically fully VPR 500 series compatible.

This kit ships with Litz wire 2623-1 output transformers. Kits with EA2623-1's are also available.

***Please note: The Litz 2623-1-L wire colors are different than the EA2623-1. To use the Litz 2623-1-L on this build, please follow the table on the bottom left of this datasheet.

The overall goal of the VC528 is to achieve the complete and lovely sound of a vintage API console channel without the cost of the rest of the console. It is definitely a little something different for the 500/51x format. Basically, it is a two stage console channel with the vintage circuitry of my API board.

The first stage is a 2520 style balanced, transformerless receiver. Everything is true to the original console circuit.

Next in the block diagram comes the fader. Due to space constraints and a request from a friend, I have chosen to use a 24 position Elma with a 1K overall value. Original faders in my board were 600ohm. The fader has 12dB of gain in hand to keep with the vintage API norm. Since the majority of the upper range gain steps are in 2dB increments, I have used a stepped Grayhill for a fader trim that is in 0.5dB increments.

I follow this filter stage with a 3 transistor discrete voltage follower using 5087/5088's. This buffer circuit is very reminiscence of the buffer amp used 4 times in the 550a. Very handy indeed.

Next in line is a 6 position stepped LP filter. This filter was not in my board. I have however implemented the same passive philosophy that they used for the HP filter that was in my board. Since it was easy to implement, I have added a switch to select 6dB or 12dB per octave for the filters. Very smooth and natural sounding, by the way.

A second 3 transistor follower is used to buffer the high and low pass filters from each other.

Next is a 6 position stepped HP filter. This filter can also be switched between a 6dB or 12dB slope per octave. Again, the overall philosophy is the very same that was used in my old board.

The last stage is the post fader booster amp. Again, the same circuit as found in the vintage console. I have modified the feeback R and C to provide unity gain when using the entire VC528 circuit.

The VC528 modules have been given a few nicknames by some happy users. They have been referred to as "Audio Bacon" as well as "The Missing Link".

So, what is new from the first version to the ML2 you ask?
The faceplate has been updated to a wet painted black with the same blue and light gray found on our other black faceplates.
An individual on/off pushbutton has been added to each filter section. This will allow for a quick and easy bypass of either one or both filters. Adding these switches freed up a position on each rotary switch so an extra filter point was added to each filter. 27kHz was added to the LP and 240Hz was added to the HP.
The previous 3-position mute toggle has been changed to a 2-position toggle that operates a hard-wire relay bypass instead of the mute function. This relay bypass has a shunt jumper connected to the Pin-6 DC bus so any adjacent ML2's can be bypassed by activating the toggle on only one unit.
A discrete follower has been added between the stepped trim switch and the LPF to prevent any interaction.
The post fader booster amp has a gain trimmer to precisely set the ML2 to unity gain.

Following is a list of additional components that are required to complete this build:
(2) 2520 style discrete operational amplifier
PS: DOA's can be added to this kit at the bottom of this page.

Here are required items that we do not carry at the store:
Solder, soldering iron and basic small hand tools
Very good assembly skills
A decent understanding of schematics and electronic components

This kit also requires the very same CMR calibration that the LC53A modules require. The extension test jig makes this a snap.

***This is one of the more complicated builds we have at the store. I do not recommend this for a beginner or inexperienced builder. While there are no plans of a dedicated "Assembly Guide", our friend and ex-newbie 'Chunger will be documenting a photo-build-doc like no other can! This may take a while so keep that in mind before purchasing. As always, I will have a build/support thread running at the GDIY forum.

Additional information and photos:

Click to enlarge

Partial Parts

Click to enlarge

The Gutz

This product bundle contains the following items:
VC528 ML2 Partial Parts Kit» 1 x VC528 ML2 Partial Parts Kit
   10 pieces in stock
2623-1-Litz Output Transformer» 2 x 2623-1-Litz Output Transformer
   164 pieces in stock
Elma 04, 1x24-1k, Shorting Rotary Switch» 1 x Elma 04, 1x24-1k, Shorting Rotary Switch
   31 pieces in stock
Grayhill 2x6 Adjustable Stop, Shorting Rotary Switch» 2 x Grayhill 2x6 Adjustable Stop, Shorting Rotary Switch
   457 pieces in stock
Discrete Voltage Follower #1» 2 x Discrete Voltage Follower #1
   716 pieces in stock
DOA PCB Socket Set» 2 x DOA PCB Socket Set
   4069 pieces in stock
Panasonic TQ2-12V DPDT Relay» 2 x Panasonic TQ2-12V DPDT Relay
   1140 pieces in stock
CAPI 5-37-1A Control Knob» 1 x CAPI 5-37-1A Control Knob
   676 pieces in stock
CAPI 5-50-1A Control Knob» 2 x CAPI 5-50-1A Control Knob
   38 pieces in stock
CAPI 5-75-1B Control Knob» 1 x CAPI 5-75-1B Control Knob
   246 pieces in stock

Cost of separate items: $363.25

Available Add-On Options for the VC528 ML2-Litz Entire Bundle
Selected Discrete Op Amp's:
 No DOA's» No DOA'sAdd-on to cost » - - -  
 (2) SL-2520 Red Dots» (2) SL-2520 Red DotsAdd-on to cost » $130.00  
 (2) gar2520 Full Kit Bundles» (2) gar2520 Full Kit BundlesAdd-on to cost » $35.00  
 (2) gar1731 Full Kit Bundles» (2) gar1731 Full Kit BundlesAdd-on to cost » $34.62  
 (1) gar2520 & (1) gar1731 Full Kit Bundle» (1) gar2520 & (1) gar1731 Full Kit BundleAdd-on to cost » $34.81  
 (2) gar2520 - Assembled» (2) gar2520 - AssembledAdd-on to cost » $120.00  
 (2) gar1731 - Assembled» (2) gar1731 - AssembledAdd-on to cost » $120.00  
 (1) gar2520 & (1) gar1731 - Assembled» (1) gar2520 & (1) gar1731 - AssembledAdd-on to cost » $120.00  
 (2) BB2521 LME49710 Full Kit Bundles» (2) BB2521 LME49710 Full Kit BundlesAdd-on to cost » $19.16  
This product was added to our catalog on Tuesday June 16, 2015.
Classic Audio Products, Inc.
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Classic Audio Products, Inc. is not affiliated with API. Customers and fans should not refer to Classic Audio Products, Inc. as "Classic API." API is a registered trademark of Automated Processes Incorporated. Classic Audio Products, Inc. has no affiliation with Automated Processes Incorporated.
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