This is an enhanced version of the legendary desktop preamp. The previous owner upgraded the tubes to NOS JAN and Mullards ($200+ upgrade). They made this even better. I have compared it to a stock solo 610 and my current stock LA 610 MK II, and you can hear the difference. The NOS tubes are wonderful, rich and smooth. The original stock JJ tubes will be included with the unit as well. 

This was the cornerstone of my studio for a number of years and has been dotingly cared for. A tremendous bass DI, and wonderful for piezo pickups. Vocals sit well in the mix with definition, but not harshness. It was also a wonderful part of my studio re-amp flow, bringing its tube magic to everything I sent through it. This is a special box. 

The unit is in excellent condition. The unit has been with me for five years and never left my smoke free studio. The unit will be lovingly packed, and will include the original JJ tubes in a separate box within the shipped package and an and IEC power chord. 

From Universal Audio:

The SOLO/610 delivers the classic Putnam 610 tube console sound in a portable, highly versatile mic preamp design. It provides the silky, vintage warmth of the original console’s mic amp design, and will flatter and enhance any microphone or instrument with its iconic tones. Thanks to its convenient form factor, the SOLO/610 can be conveniently used in the control room or the recording room, on stage, or on a desktop. Functionally lean but sonically mean, the SOLO/610 maintains the character of the 610 console — at a price every serious project studio can afford.

• Record through the classic tube circuit of the Putnam 610 console mic preamp and DI
• Add tube girth and detail to any mic
• Sculpt signals with Gain, Level, and Impedance controls for maximum tonal variety
• Craft your sounds with classic UA tube circuits, hand-built in the USA
• Details
• Classic Putnam 610 console mic preamplifier and DI

Specs

Input Impedance

• Mic Input - Selectable 450 ohms (Lo-Z) or 1.6 kilohms (Hi-Z)
• DI Input - Selectable 2.2 megohms (Lo-Z) or 50 kilohms (Hi-Z)

Output Load Impedance

• 20 Hz to 20 kHz +/- 1 dB

Maximum Gain

• 61 dB

Tube Complement

• (1) 12AX7, (1) 12AT7

Maximum Mic Input Level

• -12 dBu, 1.0% THD+N Ratio

Maximum Instrument Input Level

• +4 dBu, 1.0% THD+N Ratio

Maximum Gain Mic Input

• 55 dB (1.6K ohm input), 60 dB (450 ohm input)

Mic/Instrument In Frequency Response

• 20 Hz to 20 kHz, +/- 0.1 dB

Maximum Gain Instrument Input

• 37 dB

Dimensions

• L: 14"
• W: 5 3/4"
• H: 5"

Weight

• 9 lbs.

• Legendary all-tube sound, at a project studio price
• Gain, Level, and Impedance selection for maximum tonal variety
• Portable design for studio, desktop or stage
• Rugged construction-steel chassis
• DI features include Thru and Mic/Line level output
• Hand-built in USA; backed by 1-year limited warranty