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The White Oak Audio PL14_20 Rev G1 Dual Mono Control Board can be found here: https://www.whiteoakaudio.com/estore.aspx You will receive the proprietary schematic after your purchase. Here is some history of the WOA Control Board. Phase Linear had become known as "Blaze Linear" or "Flame...

It is OK to dip your toes in with the upgrade of a PL14b control board, many of us have done that. But when you pick up a White Oak Audio "Dual Mono" Rev G1 Control Board with four precision, +/- 15V regulated power supplies onboard, through-hole plating and two-side heavy copper etching with...

Many of us started out with tubes. Mine was a McIntosh 225. Eventually, tubes became expensive and then very hard to find. It has become better lately, but for me the damage was done. I migrated to a Marantz 2285 and never looked back. Now, no more foreign amplifiers for me - I just stick to...

The handles and meters are worth the asking price.

Lee and I found that after listening to the WOPL amplifiers at Mach 10 for about a hour, the meter problem went away on its own.

I found these folks to have a good selection... Brent Jessee Recording Supply, Inc. www.audiotubes.com

Did you replace the the 10 Ohm resistors (R38 and R39) on the backplane? What is the voltage on R25? Is it positive or negative referenced to Ground? Is you lift on leg of D12, does R2 still get hot? The amplifier might be in a permanent state of "current limiting". If you remove the yellow...

But wait! There is more. True to Joe's tagline - "Always working on making it better..." Joe has shipped me two upgrade board kits to assemble and install in my WOA Model ONE. The first upgrade board kit is Revision C of the Power Control Board. The major change is the substitution of a massive...

Your output transistor mix is fairly standard for a forty year old amplifier. We see a lot of that. The service manual states to not mix transistor types in a column, so you are good - for now. If you want a reliable, optimum set of output transistors, invest in (12) Onsemi MJ21196G. Or better...

Welcome. We like pictures because it helps us to better understand what is going on.

You always give me the best deals... How about if you buy it and I send you a 50 pound box of used power supply capacitors?

The Left and Right channels were terribly unbalanced. After I installed the 12 (WOA) MJ21196G Output Transistors, the Left and Right channels were perfectly matched.

I believe many of us hold that honor...

The OPA1611 is a Bipolar input device and the cost (from Ti) is $4.10 each. But the downside for me is the SOIC surface-mount package. The OPA134 is a FET input device and the cost (from Ti) is $2.47 each. These are PDIP packages and make replacement (and OPAMP rolling) easier. Maybe Joe can...

I just need the meters...

The mix of transistors I just removed from a customer's PL400 (not including the RCA410 Driver Transistors), I have mixed feelings of possible counterfeit MJ15024 devices:

The Phase Linear 400 Series II is probably the best amplifier ever made in the price/power category and is more than adequate for your bedroom system. These amplifiers are common on ebay. Find one that is cosmetically appealing because we have all the internal parts available now. Additionally...

This is an indication of a bad R47 10 Ohm resistor in the Right Channel. I have seen several of these 10 Ohm resistors physically cracked (electrically open) in the middle and this is due to the heat stress in that location. We typically upgrade this antique 1/4 Watt 10% Carbon resistor to a new...

As Lee can tell you, the key to getting the DC Offset low is to match the current gain, or hfe, of two TIS 97 (or TIS 93, they are close) because these transistors are used as a Differential Pair (sometimes called a "Long Tailed" Pair), common emitter configuration in each channel of the Phase...

Check that ten Ohm resistor resistance on channel B with a good Multi-meter. Those resistors were originally carbon 10% tolerance devices, but they have been known to drift after 50 years. We use 1% Metal Film resistors today.