Frotronics is your premier destination for elite vintage audio restoration. Below is a comprehensive conversion-focused on the phase linear PL-400 and PL-700. It addresses the notorious issues of Phase Linear amplifiers while highlighting Frotronics use of White Oak Audio premium replacement parts to turn them into reliable modern powerhouses. The only way we service these two amplifiers now is with a total upgrade, and is the only way we warranty the PHASE LINEAR to you our valued customer!

 

 

🛠️ Phase Linear PL400 & PL700 Restoration Services

 

From "Flame Linear" to Modern Powerhouse: Total White Oak Upgrades

The Phase Linear PL400 and PL700 amplifiers designed by Bob Carver are legendary for their raw power, effortless dynamics, and striking looks. However these vintage giants were built without modern speaker protection circuits and have old technology components that are obsolete and unobtainable in todays market. A single component failure today can cause a catastrophic DC voltage dump directly into your rare speakers.

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At Frotronics, we eliminate this vulnerability. We completely re-engineer your Phase Linear PL400 or PL700 using White Oak Audio premium replacement kits. Our comprehensive overhaul strips out the old, failure-prone original boards, backplanes, lighting/meter board, wiring, and transforms your amplifier into a rock-solid high-fidelity beast that runs cooler, safer, and cleaner than ever before.

 

 

📦 The Frotronics White Oak Restoration Package

 

We do not just patch up old circuits. We rebuild your amplifier using a bulletproof array of engineering upgrades:

• Control & Driver Boards: We drop in modern heavy-duty White Oak driver boards built with superior trace designs, low-noise metal film resistors, and precision hi-end audio components.

• DC Speaker Protection: We install dedicated relay-based speaker protection modules to ensure your speakers are forever insulated from damaging voltage faults.

• Power Supply Overhaul: We swap out degraded filter capacitors for massive high-end replacements alongside upgraded high-current bridge rectifiers for stable punchy bass.

• Output Transistor Re-Backplaning: We replace weak original factory sockets with premium White Oak backplane kits with precision metal-oxide resistors and our perfectly matched power output transistors.

• LED Meter Upgrades: We replace dim, heat-generating, incandescents with crisp long lasting White Oak LED meter lighting boards to keep the iconic faceplates glowing perfectly.

• Wiring: Rewiring is a must to accommodate all the upgraded kits on an overhaul.

• Meter-Faceplate Replacement Kit: This is not included in an upgrade package, but is available as an add-on package. If your meters are bad they can be replaced with a White Oak Audio faceplate & meter kit. Since the meters are different style a new faceplate with the meters is required.

 

 

🔍 Our Step-by-Step Restoration Process

 

Process Step What We Do

1. Diagnostic Evaluation: Bench testing the power supply rails, tracking bias stability, and evaluating structural integrity.

2. Total Deconstruction: Removing degraded original PCBs, brittle factory wiring, and old style output sockets.

3. Precision Solder Work and Cleaning: The chassis is thoroughly cleaned, populating White Oak boards, and performing expert hand-soldering.

4. Component Matching: Testing and sorting high-current transistors to guarantee perfectly balanced channels.

5. Calibration & Burn-in: Setting precise bias and DC offset, followed by a rigorous multi-day load test on the bench.

6. Sound Test: Comprehensive sound testing to insure the quality of the sound and proper operation.

 

 

🚚 Ship Your Amp to the Experts

 

Ready to revive your legendary amplifier? We offer expert nationwide mail-in repair services for audiophiles looking to protect their investment.

If you would like to get started on your restoration, let us know:

• Which model you own (the PL400 or the PL700)

• PL400 series I or II and if it is 4-fin or 8-fin

• The history or current symptoms of your unit (blown fuses, hum, dead channel, etc.)

• If you have any other vintage gear you would like to ship in the same bench cycle

 

Contact Frotronics Today to secure your spot on our bench and request a custom quote!