We will do are best to bullet point the main feature and sonic differences between each model of CAPI preamp.

The VP312 is a faithful recreation of the oringal API 312 preamp module. It has a large 2503 outputs transformer and a 2622 style input transformer with a single 2520 footprint op amp. Sonically the VP312 has punchy mids and a smooth low end.

Features:

· Mute Switch

· Pad

· Polarity

· Phantom Power

This unit is only a mic preamp and uses a passive attenuator to control the output level.

The VP25 preamp is essentially an exact recreation of the legendary preamp circuit found in the vintage API consoles of the mid to late '70's. The 528/536 input modules have precisely this same exact circuit. The only exception being the change to the larger 2503 output transformer. Sonically this preamp has a nice extended low end compared to a VP312

Features:

· Mute Switch

· Pad

· Polarity

· Phantom Power

This unit is only a mic preamp and uses a passive attenuator to control the output level.

The VP26 is the exact same circuit as a VP25 EXCEPT it uses a smaller 2623 output transformer that gives it a little bit more focus in the upper mids.

Features:

· Mute Switch

· Pad

· Polarity

· Phantom Power

This unit is only a mic preamp and uses a passive attenuator to control the output level.

The preamp section of the VP28 is almost identical to a VP26. One big difference is the VP28 features a second stage booster fader that actively boosts or attenuates the output. The great part about this second stage is it allows you to use low gain and high output for a clean signal or high input gain and low output for a more pushed aggressive sound.

Features:

· Polarity

· Mic/Line Input Mode

· -20dB Pad

· Phantom Power

· Three Frequency High Pass Filter with -6db or -12dB Settings.

· Signal Indicator Light

The mic audio path is very similar to the VP28. The main changes are Platinum exclusive CA2618 1:8 input transformers and Platinum exclusive CA2623-Pt Litz wire output transformers. In addition, Scott Liebers has created a ground up exclusive Platinum Super Dot opamp. Scott has referred to the Super Dot as his best sounding opamp yet!

A FET Direct Inject has been added to the front panel of all Platinum preamps. The front panel jack is auto switching so inserting a 1/4" plug automatically activates DI mode.

Like its kit counterpart, the VP28-Pt is a true 2-stage mic/line amplifier. The 2nd stage fader booster has 12dB of gain 'in hand', exactly like a real console. This allows for many different gain combinations. You can crank the fader and reduce the preamp gain or in contrast, attenuate the 2nd stage and crank the preamp gain for some sweet, additional harmonic content.

All Platinum preamps have a buffered two pole (-12dB) 80Hz High Pass Filter.

All Platinum preamps have a selectable input impedance. 1k or 3k for the VP28-Pt. 3k can be very useful for ribbon mics or just a great tonal option for any other microphone.

The preamp stage has been carefully modeled after the preamps in the famous Wally Heider Recording Studio 4 console custom built by Frank DeMedio circa 1972.

The CA-0887 input transformer has a buttery smooth sound quality to it.

To enhance this special preamp circuit even further, CAPI chose to employ a stepped fader similar to the popular VP28 preamp. In remaining true to the Heider® circuit, all AC coupling capacitors have been removed from the audio path. This fader booster stage has 12dB of gain 'in hand', exactly like a real console.

Capi uses a custom wound 2503-Litz output transformer.

In trying to be loyal to the console signal path, both gain stages have a 2503-Litz output transformer. The first preamp stage output transformer provides +6dB of gain, blocks DC from the stepped fader and imparts a little more character into the overall circuit, as compared to a 'direct' output.

Each Heider® H2 contains two of their potted CA-0252 op amps.

Features:

· Polarity

· Mic/Line Switch

· -20dB Pad

· Phantom Power

· 80Hz HPF

· Full Scale LED Meter

· Internal Impedance Switch (200 or 450 ohms)

It's easy to get lost in the rabbit hole trying to figure out the difference between the different models of 2520 style op amps. Here is a short description of some of the most popular op amps available with CAPI gear.