Audio Research LS-25 Mk II Pre AmplifierNew: $5495
Ask: SOLD Delivered (includes shipping in continental US and PayPal fee) (low hours on tubes; < 200 hours – see service life below)
Pay Method: Paypal
Cosmetic: 8/10; looks great, conservative rating due to age.
Ships from: 45202
Specs: • Frequency response: ±.5dB, 1.0Hz to 100kHz -3dB pionts below 0.2Hz and 400kHz
• Distortion (THD): Less than .01% at 2V RMS output
• Noise & hum: 14µV RMS residual IHF weighted balanced noise output with gain control at minimum (103dB below 2V RMS output).
• Gain: Main Output: Selectable for each input: 18db, 12dB, 6dB Balanced output. (12dB, 6dB, 0dB SE output)
• Input impedance: 120K ohms Balanced, 60K ohms SE. Inputs (
Tuner, Phono, CD, Video, Aux 1, Aux 2, Monitor, Processor (XLR and RCA connectors)
• Output impedance: 650 ohms Balanced, 325 ohms SE Main (2), 20K ohms minimum load and 2000pF maximum capacitance. Outputs (3: 2 Main, 1 Record (XLR and RCA connectors)
• Maximum inputs: 28V maximum, BAL, 14V maximum SE (6dB gain)
• Rated outputs: 2V RMS 1Hz to 100kHz into 200K ohm balanced load (maximum balanced output capability is 40V RMS at less than 0.5% THD at 1kHz).
• Power supplies: Electronically-regulated low and high voltage supplies. Automatic 40 sec. warm-up/brown-out mute. Line regulation better than .01%.
• Tube complement: LS25 MKII: (2) 6H30 dual triode
• Power requirements: 100-135VAC 60Hz (200-270VAC 50/60Hz) 45 watts maximum
• Other: Controls: Volume (104 steps), Gain, Balance, Input. Toggle switches: Power On/Off, Stereo/Mono, Bal In/SE In, Processor/Input, Monitor/Input, Mute/Operate.
• Dimensions: 19" (48 cm) W x 5.25" (13.4 cm) H (standard rack panel) x 11.75" (29.8 cm) D Handles extend 1.50" (3.8 cm) forward of front panel.
• Weight: 18 lbs. (8.2 kg) Net; 28 lbs. (12.7 kg) Shipping.
Reason for sale: Spring Audio Cleaning in Summer!
Notes: 2nd Owner
* Sonically and functional perfect
* Manual and original box
* Includes 2 Russian 6H30Pi Platinum Grade, Cryogenically Treated from Upscale Audio (less than year old)
Online Feedback: pgbcincy (audiogon); zosocincy (ebay)
Used this pre amp with the ARC VT-100 Mk III, a great combination. I’ve never experience more of an improvement in soundstaging and instrument spacing than when I inserted this pre.
Any questions, let me know.
Thx! Paul
From Audio Research about Mk II: Having held a firm position in our product lineup for two-and-a-half years, the LS25 has proved highly popular for both its musicality and its many features and system flexibility. With recent engineering breakthroughs at Audio Research, however -- especially stemming from the development of the VTM200 input stage technology -- it became increasingly clear that the venerable LS25 was the perfect preamplifier candidate for these latest performance enhancements.
Because it already has so many useful control functions, the LS25MKII remains almost entirely unchanged in its exterior configuration -- meaning original units can be updated at the factory to the MKII spec. Inside, however, you will find a new motherboard architecture that incorporates a JFET input stage similar to that used in the VTM200, followed by a cathode-follower / output driver stage using two 6H30 twin triodes.
The 6H30 is a new tube for Audio Research ideally suited to its function in the LS25MKII. It is a Russian military tube in current production and use, and is rated by its manufacturer to have an estimated service life of up to 10,000 hours. It has shown highly stable and consistent in its operating characteristics. While its pin configuration is similar to the 6922, it is not a direct replacement. It has higher current requirements for the heater filaments, so it requires a different power transformer than used in the original LS25, as well as power supply adjustments.
Finally, like the VTM200, the LS25MKII also incorporates a rear-panel 12V on/off trigger for even easier incorporation into audio-video installations, or simply for installations where the customer wants more convenient system control. This is the only external modification to the original. You will see this feature appear on future models from Audio Research as well.
The complete MKII changes are available to original LS25 owners as a factory update. New 6H30 tubes with damping rings are included. Contact the Audio Research Customer Service department to schedule any LS25 updates. Units sent in without prescheduling may encounter substantial delays in turnaround.
In performance, we believe the LS25MKII blows by the original in every respect. It is faster, more dynamic, more open-sounding and presents a more tightly focused soundstage. Bass response is cleaner, quicker, with more apparent impact, while high frequencies are much purer sounding than the original. You will love the coherence of the new MKII -- vividly alive from top to bottom, with an immediacy that is stunning when driving really capable power amplifiers like the VTM200's!
Link:
http://www.arcdb.ws/LS25/LS25.html
