McIntosh C2500 Tube Preamplifier, Complete and Like New

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The C2500 is one of my favorite preamps McIntosh ever made.

I used this exact listed preamp in my main system for many years until I replaced it with the flagship two-piece C1100.

While the C1100 is a formidable tube preamp and probably the best measuring unit we've tested, the C2500 comes pretty close. I do miss the convenience of the built-in DAC for streaming which the C1100 eliminated. 

The C2500 is also a gorgeous unit with its visible glass tube window on top and the highly polished stainless chassis.

It also has a fully tubed phono section for hooking up even the most demanding of MC (Moving-Coil) phono cartridges. 

If you're considering the new C2700 and don't want to wait for eternity until the massive back order is cleared, then this might be your best option with little to no compromise. The C2700 will also set you back $8000.

This C2500 will arrive complete with the original owners manual and remote.

It will also ship in its original special McIntosh double carton which is the only way to ensure safe travels.

Firmware Notes:
• C2500 Operating Firmware: Updated to V1.03, latest available.
• C2500 USB Audio Firmware: Updated to V2.21, latest available.

Recommended Cables:

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects - Better

Kimber Kable - Flagship Phono Interconnects - Best

Kimber Kable - BALANCED XLR Connectors - Better

Kimber Kable - BALANCED XLR Connectors - Best

Kimber Kable - Coaxial Digital Interconnect

Kimber Kable - Optical Digital Interconnect

Kimber Kable - USB Select Series Interconnect

Kimber Kable - Power Cords - Better

Kimber Kable - Power Cords - Best

More from McIntosh:

The McIntosh C2500 Tube Preamplifier is one of the finest Preamplifiers ever created with connections for both analog and digital sources. The C2500 Outputs have the ability to drive multiple Power Amplifiers. The C2500 reproduction is sonically transparent and absolutely accurate. The McIntosh Sound is “The Sound of the Music Itself.”

Performance Features Include:

• Electromagnetic Input Switching with Level Trim Adjustment

Digital Logic integrated circuits drive Electromag- netic Switches on all Inputs and operating functions for reliable, noiseless, distortion free switching. All eight Inputs on the C2500 can be matched in level, so there are no abrupt changes in volume levels between the different Inputs.

• Moving Coil and Moving Magnet Phono Inputs

The C2500 contains two different precision Phono Preamplifier Circuits. One for low output Moving Coil Phono Cartridges with selectable resistance loading, the other is for Moving Magnet Cartridges with select- able capacitive loading. Both circuits use the latest designs to provide the lowest possible noise and dis- tortion. The RIAA Correction Equalization Circuitry utilizes close tolerance resistors and capacitors for an extremely flat frequency response.

• Digital Audio Inputs

The C2500 has Coaxial, Optical and USB Digital In- puts to Decode PCM Signals from an external source. The C2500 Up Samples the Digital Signal to 192kHz with 32Bit resolution before the Digital to Analog process begins.

• Balanced Inputs

The Balanced Inputs allow the connection of a source component using long cable lengths without a loss in sound quality.

• Precision Tracking Volume Control

Volume levels are controlled by a new Multi-Stage Precision Digitally Controlled Attenuator System with superb tracking accuracy.

• Variable Rate Volume and Balance Controls

The C2500 Tube Preamplifier’s Volume and Balance Control Circuitry provides an ideal rate of change with control rotation.

• Remote Control with External Sensor Input

The Remote Control provides control of the C2500 operating functions and McIntosh Source Components connected to it. Enjoy your McIntosh System from another room in your home by connecting an external sensor.

• Special Power Supply

Fully regulated Power Supplies and a special R-Core Power Transformer ensure stable noise free operation even though the power line varies.

Manual:

McIntosh C2500 Tube Preamplifier - Owner's Manual

Technical Specifications

Frequency Response

+0, -0.5dB from 20Hz to 20,000Hz 

+0, -3dB from 10Hz to 100,000Hz

Total Harmonic Distortion

0.08% from 20Hz to 20,000Hz

Rated Output (Main)

2.5V Unbalanced, 5V Balanced

Maximum Output

8V RMS Unbalanced, 16V RMS Balanced

Sensitivity (for rated output)

High Level, 450mV unbalanced, 900mV balanced 

Phono MM, 4.5mV

Phono MC, 0.45mV

Signal To Noise Ratio (A-Weighted)

High Level, 100dB below rated output 

Phono MM, 75dB below 5mV input Phono MC, 75dB below 0.5mV input

Input Impedance

High Level, 22K ohms unbalanced, 44k ohms balanced

Phono MM, 47K ohms; 50 to 750pF, in 50pF steps 

Phono MC, 25, 50, 100, 200, 400 or 1,000 ohms; 100pF

Maximum Input Signal

High Level, 8V Unbalanced, 16V Balanced 

Phono MM, 80mV

Phono MC, 8mV

Voltage Gain

High Level to Record Output: 0dB 

High Level to Main Output: 15dB 

Phono MM to Record Output: 40dB 

Phono MC to Record Output: 60dB

Output Impedance

220 ohms

Headphone Impedance

20 ohms to 600 ohms

Digital Input Sample Rates

Optical: 16Bit, 24Bit - 32kHz to 96kHz 

Coaxial: 16Bit, 24Bit - 32kHz to 96kHz

USB: 16Bit, 24Bit, 32Bit - 32kHz to 192kHz

Power Control and Trigger Output

12VDC, 25mA

General Specifications

Power Requirements

Field AC Voltage conversion of the C2500 is not possible. 

120 Volts, 50/60Hz at 50 watts 

Standby Power, less than 0.5 watts

Overall Dimensions

Width is 17-1/2 inches (44.45cm)

Height is 7-5/8 inches (19.37cm) including feet Depth is 18 inches (45.72cm) including the Front Panel, Knobs and Cables

Weight

30.5 pounds (13.8 kg) net

46 pounds (20.9 kg) in shipping carton

Shipping Carton Dimensions

Width is 27 inches (68.6cm) 

Height is 14 inches (35.6cm) 

Depth is 25 inches (63.5cm)

The SkyFi Testing Process for Preamplifiers:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCB’s for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface. The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope. We then switch to a 1KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment. Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.

We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected. If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.