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This should help with the write up on amp test procedures. I apologize for the "crooked scan". It is a copy of a copy.

Happy (belated) Turkey Day to everyone.

Thanks Glen for confirming that. I tried to keep the PLX the same size as the original PL36, but there were just too many components in the new design to use the same size PCB and have room to comfortably layout the components without the PCB being "densely populated". Sniffer, The PLX will...

The new PLX driver board is slightly larger than the original PL36. The PLX is 8.25" x 5.75". The original Pl36 is about 6 3/4" x 5 5/8". The PLX will fit into 400 and 700 chassis, but I'll have to double check fitting both the PLX and a DCP. I just thought about how popular the DCP is just...

After tossing the new amp idea around for awhile and considering the 400 and 700 chassis layout, I have finalized the amp design. It's not the one I was anticipating originally, but it is a good design (tried and true) and should offer exceptional performance from a 400 or 700 chassis. The amp...

I think you helped Santa out financially for quite a while with that purchase! I'm sure they will sound great too.

Solid state amps have been built with bridging options for a long time. There are different ways to bridge an amp, and depending on the method used, DC offset may be affected. Distortion will usually rise slightly because you are driving a lower load as seen by the amp. With the configuration...

What do you have planned for the 700ll? Keep it stock or go all out and mod it?

I have long suspected that the bias circuit on the 400 / 500 / 700 was too sensitive. A small change to the bias circuit confirmed this. See revised schematic for changes. Adding RNew (27 Ohms) compensates for the internal resistance that all transistors have. This internal resistance changes...

Audio Control used the 4136 extensively in their early car audio products in the mid 80's and after. Their products were not what I would call "inexpensive", but they did develop a cult following with good marketing and engineering/technical support. Bose uses 4558's in most of their consumer...

Let's do it. How do I pay.

There is a free basic box program called Win ISD. It works good for box alignments. Check it out. http://www.linearteam.dk/default.aspx?pageid=winisd

What is the going rate for a 400 power transformer and one Dixon meter?

The sound improvement will probably not be as incredible as you might think. Certainly not worth $5. If 100 people answered your question, you would get 100 different answers. My advice is to not get sucked into that audiophool universe. Just use good quality parts and your projects will turn...

More re-drawn D500 schematics. I'm working on the rest of the LED meter(s) and control section next. I can't believe PL (attempted to) squeeze the entire schematic on one lousy page and made the print so small.

This is a full comp amp, so it uses MJ15024 and MJ15025's. A quasi comp would use all MJ15024's. I have a lot of these MJ150xx types and I don't run my amps hard so they are fine for me. The MJ21xxx have a higher SOA and are better in general terms (more beta, etc). The idle current is not...

In stock configuration this may be a true statement. It depends on your listening habits. When I first acquired my pair of 1974 La Scala's, I was listening to a pair of Heresy's (1977). The La Scala's sounded "bigger and better" but they did lack a bit in the low-end. After porting the La...

Images showing how to reconfigure pre-driver and driver resistors and head sinks used on VAS transistor.

I have been experimenting with some easy modifications on the PL36 driver board. My main interest has been to modify the pre-driver and driver circuit to reduce crossover distortion that, in my opinion, has always been too high in the 400II and 700II amps. Here is some history of my “test...

With a 48dB/octave slope, you can cross over a speaker right up or down, to its limits, without damage. Al K. knows his stuff. Although nowadays with access to good laptop based hardware and software, you can spend $300 and get a "poor man's" Klippel and design and tweak your own speakers and...