Unwell Phase Linear 700 series II
- Thread starter Michael F
- Start date
Glen,
I was asked many years ago either on this forum or elsewhere to post some schematics for the fully comp 700 series two amplifier. I hesitated at that time because I knew there were some errors in the schematics and that some debate would follow. Most notably is the inclusion of the fly back diodes which neither I or Dean have ever seen on any 400 or 700 series two fully complementary output amplifier. NOTE: The fully comp amps started around 1981 and were in production for only 1 year with the exception of the PRO700 which was in production as late as 1984 and were made in Laredo Texas.
I asked Dean about the fly back diodes and his comment was they were probably not needed. As a result of this comment, I got a lot of feedback. I was only reporting what he told me on the forum. These were not my thoughts or opinions. Maybe someday when the moment is right, I can ask Terry P. who designed the 700 series two amplifier why he removed the fly back diodes along with a bunch of other questions I have.
In general, I have tried to adhere to the "Service Center Agreement" contract over the years. However I now am finding myself not in adherence to section 7.11 "To keep my knowledge of Phase products, design techniques and service information confidential". At some point I will not be compliance with section 7.12 "Not make any circuit changes or install any parts or components which are not authorized by Phase Linear".
Someday I may also report what was going on in the engineering department in 1977 and the differences in design concepts which was one of the things that led up to Bob's departure in March 1978.
Ed
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Every designer worth his salt puts a clamp diode around the coil of a DC relay. When power is turned off to a relay, usually by a transistor turning off, the collapsing magnetic filed in the relay turns into a voltage spike generator. A 12 volt relay can easily generate a pulse in excess of 100V. The diode clamps the voltage. Without the diode the transistor sees the voltage spike and may be damaged.
Speaker cabinets with woofers can also generate inductive spikes just like a relay. The potential cost of a blown amp versus the cost of a couple diodes should seem a like an easy decision to include them.
As for the service center agreement, I signed one, and figured it was null and void once the service department no longer existed. I scanned the common manuals that I was provided by P/L and have posted them here and elsewhere. Nobody is being hurt because of that and I don't lose any sleep about it.
Speaker cabinets with woofers can also generate inductive spikes just like a relay. The potential cost of a blown amp versus the cost of a couple diodes should seem a like an easy decision to include them.
As for the service center agreement, I signed one, and figured it was null and void once the service department no longer existed. I scanned the common manuals that I was provided by P/L and have posted them here and elsewhere. Nobody is being hurt because of that and I don't lose any sleep about it.
Don,
Most people have no idea how much grief I got from Dean over the 25+ years I worked with him when I replaced the XPL909's, FPL909's, etc with MJ15024 (and later MJ21196) output transistors in series 1 amplifiers. He hated dealing with the oscillations that they created and in some instances we couldn't get the amplifier to meet the .25% factory spec for THD at 20kHz at rated output. In which case, I had to re-install the old semiconductors and he would have to re-test again. Using slow-down and by-pass capacitors would also have an affect on a number of other parameters that weren't measured in the service manual but were stated in the sales brochures and owner's manuals.
There is more to the story but it wouldn't benefit me to share the details. I would much rather appreciate the time he was willing to spend with me as a mentor and a friend.
I have also seen Dean work on a fair number of pieces of Phase Linear audio equipment that has been modified over the years. Most of them did not meet spec and had to be restored back to original in order to meet factory specs.
Ed
Most people have no idea how much grief I got from Dean over the 25+ years I worked with him when I replaced the XPL909's, FPL909's, etc with MJ15024 (and later MJ21196) output transistors in series 1 amplifiers. He hated dealing with the oscillations that they created and in some instances we couldn't get the amplifier to meet the .25% factory spec for THD at 20kHz at rated output. In which case, I had to re-install the old semiconductors and he would have to re-test again. Using slow-down and by-pass capacitors would also have an affect on a number of other parameters that weren't measured in the service manual but were stated in the sales brochures and owner's manuals.
There is more to the story but it wouldn't benefit me to share the details. I would much rather appreciate the time he was willing to spend with me as a mentor and a friend.
I have also seen Dean work on a fair number of pieces of Phase Linear audio equipment that has been modified over the years. Most of them did not meet spec and had to be restored back to original in order to meet factory specs.
Ed
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You cannot keep your information Confidential unless you mark it as such and put a non-disclosure agreement in place to protect that confidentiality (which would have long since expired). NONE of the original PL documentation that I have in my collection has confidential, copyright or trademark notices on them.
The 700 will be more specifically doing LFE duty. I have a few classic amps that I rotate in and out for that role, a BGW 750B, a Yamaha P2200, Peavey CS800 and the 700B I once owned. The 700B was the clear champion in that role, I`m hoping the 700 series II will re claim that title.
My main speakers easily go down to the high 20s in-room so a sub is not needed for 2 channel listening.
Once the 700 is up and running, I`ll definitely give it a try full range but for the past few years I`ve been very happy with the Krell KSA 50s. It`s a wonderful class A amplifier
My main speakers easily go down to the high 20s in-room so a sub is not needed for 2 channel listening.
Once the 700 is up and running, I`ll definitely give it a try full range but for the past few years I`ve been very happy with the Krell KSA 50s. It`s a wonderful class A amplifier
