Electro-Voice 7100

EV 7100

The EV 7100 is a 1.75 inch high (1U) stereo power amplifier that is well suited to drive near field monitors in recording studios. She is totally silent as no fans are used. With a power rating of 75W into Ω and 100W into 4Ω, she can be “mono-bridged” for 200W into 8Ω if higher power is desired. Other applications include commercial installations like in retail spaces, restaurants and public venues.

EV 7100Fig 1 – Electro-Voice 7100 Amplifier Schematic

I was blown away when I saw the schematic of the EV 7100. This is not your normal commercial amplifier. She is more HiFi like. All her transistors are highly regarded Japanese types, including the SANKEN power transistors 2SC3519 and 2SA1386. The input differential incorporates a pair of current mirrors for an active load. This results in high gain without “loading” the differential. A bit over the top is a Pre-Driver driving a Main Driver. There’s really no necessity for this as there’s only one pair of power transistors but it’s a nice touch. Lastly, she uses a NJM 5532 for a Servo to null the DC offset. No manual adjustment is required.

Fig 2 – Inside the EV 7100

Summary

The EV 7100 is one of those rare commercial amplifiers that straddle the PA market as well as Domestic HiFi. She can be tweaked to sweeten the sound without much effort.

Fig 3 – EV 7100 Power Supply

One of the improvements that can be easily made is to upgrade the Filter capacitors. In the original amplifier (Fig 2), there are only two pieces of 10,000uF/63V. They can be replaced with 20,000uF, totally 40,000uF. Whether they will fit is another matter. That’s one of the issues with a 1U height chassis.