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Description of Item:
This is the premier PL400 Capacitor Upgrade Kit on the web. It is a professional-class upgrade product, meticulously engineered to look and perform better than the original.

Do you own a Phase Linear 400 Series 1 Amplifier (the one with the 2 big VU meters) or the Series 2 with the LED based Cylon meters? It is a great amplifier but it has always been deficient in bulk storage capacitance in the power supply. Coupled with that, 40+ years has taken its toll on the quality of the original capacitors installed in your amp. You are not getting the bass punch that this amp is capable of and you are living with a noise floor that is far worse than it can be.

Here is your opportunity to replace the original pair of 5900 uF 85V capacitors (some vintage PL400s may have differing values such as 7,300 uF 75V) with a high-quality, long-life replacement pair with a capacitance value of 15,000uF 100V.

This is a brand new, fully assembled, bulk capacitor upgrade to replace the original worn out electrolytic power supply capacitor pair with brand new pair of modern high capacity electrolytics. Like all White Oak Audio Products, this kit is a direct drop in for the original. The results below speak for themselves.

This scope trace is what your power supply voltage rails looks like BEFORE the upgrade while playing normal program material at ~2W output:

This scope trace is what your power supply voltage rails will look like AFTER the upgrade while playing normal program material at ~2W output (Yes, the scale is identical between the two scope traces):

This is a complete, ready to install assembly including all the electronic components as shown in the photos above and the link to the installation instructions and documentation. The components you receive in your assembly may differ slightly in appearance from those above due to parts changes by the component manufacturers.

Quick and easy installation involves:
  • Removing the top cover from your Phase Linear amplifier
  • Removing the faceplate assembly from your Phase Linear amplifier
  • Removing the original capacitor hold down bracket
  • Removing your original bulk capacitors
  • Removing the wires from the original capacitor screw terminals
  • Reattaching the wires to the new White Oak Audio capacitor screw terminals
  • Re-installing your new White Oak Audio bulk capacitors
  • Reinstalling the new White Oak Audio hold down bracket
  • Dressing and neatening up the wiring
  • Reinstalling the faceplate assembly on your amplifier
  • Reinstalling the top cover on your Phase Linear amplifier
  • Enjoying your new upgrade

You get exactly what you see in the picture above which includes:
  • 2 - White Oak Audio Design upgrade PCB (double sided, computer grade, with silkscreen and solder mask) assembled to the 2 capacitors
  • 4 - High quality, 100V, 105C, 40mm diameter snap in capacitors.
  • 4 - RAF Electronics 3077-B-1032-B solid brass swage standoffs, 5/16" OD x 3/16" long, internally 10-32 threaded
  • 4 - 10-32 x 1/4" machine screws with 8 internal tooth lockwashers
  • 1 - 6061 0.090" thick aluminum alloy, precision laser cut capacitor hold down plate to replace the original Phase Linear bracket.
  • 1 - 10-24 threaded rod, 1.875" long with 2 - 10-24 SS hex nuts, 2 - #10 SS internal tooth lockwashers and 2 - #10 SS flat washers.  
  • Complete subassembly by White Oak Audio Design as shown in the first picture!

Capacitor Stackup Options:

  • 15,000uF, 100V Pair (30,000uF total capacitance).  2 - Premium rated Capacitors, 15,000 uF, 100V 40mm x 105mm.  Overall length approx. 125mm with the cap boards installed.
Detailed photographs, assembly parts list and "crystal clear" installation instructions are located at this link below:

New capacitor specifications:
  • Total capacitance per rail: 15,000+/-20% uF vs. 5900 uF original (some vintage PL400s may have differing values)
  • DC working voltage per capacitor: 100V steady state/125V surge vs. 85V steady state/100V surge original
  • Capacitor maximum operating temperature: 105 degrees C vs. 85 degrees C original
  • Capacitor maximum ripple current: 7.8A minimum at 120 Hz, 85 degrees C for each capacitor
  • Capacitor maximum ESR: 0.021 ohms maximum at 120 Hz, 25 degrees C for each capacitor

This upgrade assembly is easy to install but requires some skill. While installation is not a difficult procedure, the installer should be familiar and comfortable with working on electronic equipment and using associated tools. If you are not familiar with working on electronic equipment or do not possess the proper equipment, it is recommended that you take your amplifier to a service technician that can perform the Capacitor Upgrade installation for you. Bare board only and complete ready to build kits are available from White Oak Audio Design (whiteoakaudio.com) or on possibly on Ebay if we happen to be running such auction at the time.

The printed circuit board is a high quality FR-4 based, epoxy-glass PCB with HASL tin/lead plating on the solder pad areas. The PCB is 0.062" thick double sided circuit board with plated through holes and white epoxy silk screen legending on the component side and green solder mask on both sides. This capacitor assembly is a direct drop in for the original capacitor size, using mounting hardware supplied in the kit to secure it in the amplifier. This replacement kit includes a new, high quality, aluminum hold down plate to replace the original.

Watch for other innovative Phase Linear upgrades that are always coming from White Oak Audio Design.

Photos of the finished project are shown below (installed in chassis before and after).

Applicability of Kit: The White Oak Audio Design PL400 Capacitor Upgrade Kit replaces only original Phase Linear 400’s that are equipped with 1.75” diameter by 4.125” long screw terminal capacitors as shown in the above figures. It is not for replacement of any other type capacitors or terminal configuration. If your original Phase Linear amplifier does not match these requirements or look like these photographs, do not install this kit without contacting White Oak Audio Design first for guidance.

This kit is sold AS-NEW with no returns (due to potential damage to the circuit board once assembly has begun).

Ship From Zip Code: 01564
Shipping Weight:1 pound 8 oz.
White Oak Audio will ship via USPS Priority Mail worldwide for Cap Assemblies at buyers expense. When ordering from the eStore, please let us know your ship to destination.  If you require other than USPS Priority shipping service, buyer will be responsible for shipping charges by method selected on the shipping weight stated above. If you do not pay for shipping insurance, delivery will be made totally at buyer's risk for loss and damage.

Your purchase will be professionally and neatly packaged for shipment within the standard USPS Priority Mail Box. International orders are welcome.

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