Audio Research LS25 Vacuum Tube Preamplifier

Audio Research LS25 Vacuum Tube Preamplifier

Audio Research

Regular price $1,750.00 USD
Sale price $1,750.00 USD Regular price
Sale Sold out
A tube type line-level preamplifier developed as a new generation model following Reference1.

All eight inputs, including the processor and tape monitor, support balanced / unbalanced connections.
Two main out and REC out channels are also equipped with balanced output jacks.

The amplifier circuit uses a pure A-class balanced amplifier.

The output stage employs 3 types of infinicaps for the coupling, and the impedance is extremely reduced in a wide band, so the optimum matching condition can be obtained regardless of whether it is a tube power amplifier or a semiconductor power amplifier.

The function control uses a microprocessor, precision relay and full digital control by toggle switch operation.
An electronic switch or electronic volume is not used, and the signal system and control system are separated from the power supply and are designed without interference.

The LS25 is equipped with an independent gain setting for each input and a set value last memory function.
This function allows you to change the total gain of the amplifier in three 6 dB steps (6/12/18dB for balanced connections, 0/6/12dB for unbalanced connections). The individual gain memories are retained even when the power switch is turned off.

Digital control is also used for volume control, and it can be adjusted by 104 steps.

Equipped with an auto-mute circuit for approximately 40 seconds when power is turned on.

The balanced and unbalanced inputs can be selected at any time by operating the toggle switch.

A detachable power cable with an IEC connector is used.

Out of stock

There’s something undeniably magnetic about vintage audio gear. The tactile weight of milled aluminum knobs, the warm glow of dial lamps, and—above all—the rich, analog sound that today’s sterile streaming boxes can’t quite replicate. But time is merciless: capacitors dry out, switches oxidize, and those gorgeous walnut cabinets lose their sheen. That’s where the art (and science) of our vintage audio refurbishment comes in.

Why Vintage Audio Still Matters

In the golden era of hi-fi—roughly the mid-1960s through the early 1980s—companies like Marantz, McIntosh, Pioneer, Sansui, and Technics were engaged in an arms race of build quality. This was before cost-cutting plastics and disposable designs; amplifiers were over-engineered, receivers were works of art, and turntables were precision instruments.

Owning one wasn’t just about sound; it was about status and permanence. These machines were built to last a lifetime—or two. The irony? Decades later, they often do, provided they’re given the care they deserve.

The Philosophy of Refurbishment

Refurbishment is not just about fixing; it’s about preserving authenticity while ensuring reliability. The goal is to keep that lush, analog character alive without compromising safety or sound quality.

Some enthusiasts chase museum-level originality—keeping every factory component in place. Others opt for sympathetic modernization, upgrading parts that never existed in the ’70s to improve performance. Both approaches can be valid; it depends on your vision.

The Turntable Store refurbishing process.. step by step

Step 1: The Initial Encounter

When we first meet a 40-year-old amplifier, we resist the urge to plug it in right away. That dusty Marantz 2270 might look gorgeous, but old electrolytics and brittle insulation can short instantly under full voltage.

Instead:

  • We inspect for corrosion, burnt resistors, and leaking capacitors.
  • We use a Variac (variable transformer) to bring up voltage slowly, reforming capacitors rather than shocking them back to life.
  • We check fuses—not just for continuity but for correct ratings.

Tip: A faint musty smell? That’s often the scent of old phenolic boards, not trouble. But a burnt smell? That’s trouble.


Step 2: Deep Cleaning & Control Detox

Dust is the enemy of good sound, that is why we clean the interior carefully with compressed air and a soft brush.

The real magic comes with switches and potentiometers. Over decades, oxidation builds up, causing scratchy controls and dropouts. A deep contact clean in each pot and switch, followed by vigorous cycling, often restores silky-smooth operation.

Step 3: Electrical Resurrection

This is where science meets art:

  • Capacitors: Electrolytic caps often need some attention. We replace out-of-spec caps with high-quality modern equivalents (Nichicon, Panasonic), avoiding over-capacitance unless the power supply can handle it.
  • Resistors: Carbon comp resistors drift over decades. Measure and replace out-of-spec parts.
  • Transistors: Certain vintage transistors (e.g., 2SC458) are notorious for noise. We do swap defective ones for modern low-noise equivalents.
  • Relays & Lamps: Speaker relays oxidize; replace or clean contacts. Dial lamps? Upgrade to warm LEDs for a factory glow without the heat.


Step 4: Cosmetic Glory

Refinishing the walnut cabinet can transform a unit. We do use real wood oil or Danish oil, not polyurethane. We clean the glass dial carefully; those silkscreened letters are fragile.

Knobs? We polish with metal cleaner, but never use abrasives on anodized aluminum.

Faceplate lettering? We avoid harsh chemicals—just mild soap and a microfiber cloth.


Step 5: Calibration & Sonic Check

After the repair and cleaning, it’s time to dial in the performance:

  • We do adjust bias and DC offset on amplifiers for stable operation.
  • On turntables, we re-lube bearings, replace belts, and check speed accuracy.
  • On Cassette Decks and Reel to Reels, we replace belts ( if needed ), we clean and demagnetize the heads before the alignment process ( a must ! ) 

When done right, the result is astonishing: a sound that breathes—liquid mids, velvet highs, and bass with a tactile presence that modern gear rarely matches.


Our promise for Audiophile-Level Results

  • We Avoid Cheap Parts: That $5 eBay capacitor kit? Hard pass. We use reputable brands.
  • We Don’t Over-Polish: Patina is part of the charm. We aim for “well-loved,” not “plastic surgery.”
  • We Upgrade Discreetly: If we must modernize (like adding gold-plated RCA jacks), we keep it tasteful and reversible.


Why It’s Worth It

The payoff isn’t just sonic—it’s emotional. Restoring a 1970s Marantz or Sansui is like bringing a classic car back to life. Every glowing dial lamp, every smooth rotation of a volume knob, connects you to an era when music mattered enough to build machines like this.

And when you drop the needle on your favorite record and hear that warm, enveloping sound, you’ll know: this wasn’t just a repair. It was a resurrection.

We have a 14-day return policy, which means you have 14 days after receiving your item to request a return. 

To be eligible for a return, your item must be in the same condition that you received it, unworn or unused, with tags, and in its original packaging. You’ll also need the receipt or proof of purchase.

To start a return, you can contact us at theturntablestore@gmail.com. Please note that returns will need to be sent to the following address: 

The Turntable Store
45 Market Square
Manheim PA 17545

If your return is accepted, we’ll send you a return shipping label, as well as instructions on how and where to send your package. Items sent back to us without first requesting a return will not be accepted.

You can always contact us for any return question at theturntablestore@gmail.com.


Damages and issues
Please inspect your order upon reception and contact us immediately if the item is defective, damaged or if you receive the wrong item, so that we can evaluate the issue and make it right.

Exceptions / non-returnable items
Certain types of items cannot be returned, like turntable needles and custom products (such as special orders or personalized items). We also do not accept returns for hazardous materials, flammable liquids, or gases. Please get in touch if you have questions or concerns about your specific item. 

Unfortunately, we cannot accept returns on sale items or gift cards.

Exchanges
The fastest way to ensure you get what you want is to return the item you have, and once the return is accepted, make a separate purchase for the new item.

European Union 14 day cooling off period
Notwithstanding the above, if the merchandise is being shipped into the European Union, you have the right to cancel or return your order within 14 days, for any reason and without a justification. As above, your item must be in the same condition that you received it, unworn or unused, with tags, and in its original packaging. You’ll also need the receipt or proof of purchase.

Refunds
We will notify you once we’ve received and inspected your return, and let you know if the refund was approved or not. If approved, you’ll be automatically refunded on your original payment method within 10 business days. Please remember it can take some time for your bank or credit card company to process and post the refund too.
If more than 15 business days have passed since we’ve approved your return, please contact us at theturntablestore@gmail.com.

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All items are meticulously serviced and restored to meet factory specifications

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