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The C-500 is a nice amp (I have 2 of them). Build quality of the C-500 is just as good as the PL gear. It is very similar to a PL 400. The C-500 puts out a little more power than the 400 and has 8 outputs (per channel) instead of 6. If you can get it for a decent price, I would buy it...

My intention is to make the new PCB the same dimensions as the original PL36 board with connections at the bottom. The only modification will be to the 150 Ohm pre-driver and 10 Ohm driver resistors. The 150 Ohm resistors can be removed because the new PCB will include the pre-driver resistor...

The Leach DB design used stacked output transistors to increase power output. The "stacking" (a variation of cascoding) also allowed the use of transistors with a lower voltage rating. However, to answer your question, the design I am working on is not the same as the Leach. The Leach design...

Each stage (input stage, VAS stage and output stage) is optimized / linearized with local feedback (degeneration), then global feedback is used. Since each stage is operating in a very linear manner, minimal global feedback is needed. I prefer to keep a design a simple as possible and not use...

Joe's design and my design are totally different. Joe's design is similar to the original PL circuit. Mine is not. My design offering is not meant to be a "competition", it's an alternative. In the end, when the PCB is available and you want to try it, great. If not, I'll still be tinkering...

Probable not. It may be better. It may not be. From a technical standpoint the design will address distortion mechanisms that have been identified and documented (Cordell, Self and Slone). Noise and distortion will be low, but we all know that that doesn't really mean anything when it comes to...

Here are some parts of the D500 schematic that I re-drew awhile back. The original is too small to easily follow. I'm slowly working on (re-drawing) the rest of the circuitry.

I have finally had a chance to design a new driver circuit for the 400 and 700. The 400 and 700 make excellent project amps because of the way the chassis is laid out and the power transformers are robust. The latest power supply caps pack more Farads, so updating to more capacitance is easy in...

I have access to about 100 of the 3439 as well as the 3440/5415/16. NOS, not clones or junk. About $1.00USD a piece.

Here is the schematic of the famed 80's Class A amp. I drew the schematic in Orcad, next I'll start on the PCB layout.

I did the layout and a Chinese associate got one of his vendors to make the boards in Asia.

If anybody needs a PL36 driver board for a PL Series II 400 / 700 I have a few extra that I can let go for cheap. I needed a driver board for a 700II that I was restoring and I had some made. These are bare boards only. You can stuff them with your own preferred parts.

It has been a long time since I actually did A/B silicon testing. I'll use my test equipment to "guide me", but you know the ears are the final judge. I think I have a pretty good ear, but not a golden ear like some audiophiles seem to have.

Hello everyone. Recently, while going through my ever increasing stash of electronic hobby parts (I swear these things breed like Tribbles when I am not around), I found items I had forgotten that I had! Imagine that. Fast forward a few weeks... while flying to "Vegas for the annual CES, I came...

Ok, I have to ask... please give me the whole story on the last post.

Is that a challenge to start a new thread and proclaim "op-amp" wars? :o)

I have been wanting to design a driver board for the 400 / 700 with a transistor based CCS (constant current source) for the VAS instead of the 'ole "bootstrap" method. However, the bootstrap method is inexpensive, almost foolproof and last but not least... it works. The Series II seem to have...

From what I remember, the noise, distortion, etc were very similar to other Series II based PL amps.

I could have sworn I had some AP curves of the D 500, but I can't find them. I'll have to run some new ones, perhaps tomorrow.