Don Imlay's Phase Linear 400 Series II Quasi -Comp.

[laatsch55]

With the 21194's as drivers, VERY slightly MORE than a 15024. Say .005 to .008 more.

 

[laatsch55]

Got some 3059's i might throw in too. 2SD55's?? 1BO5's?? MJ1800's??

 

[laatsch55]

Yeah, your analyzer is awesome. And in thhe hands of someone wheo knows how to use it, it must be fun as hell. So are Phas Linear 400 Series II going to be a viable rebuild amp? Are they going to perform at the level of the Series I? I know you said the bean counters had made the component quality dive, but some of those things can be changed. Were there any real improvements to the circuit from the SEries I, or are they mostly cosmetic and economic? Just interested in whaat your overall take on these amps might be. How about the DRS Series? Anything worth rebuilding there? How about a Dual 500? Worth the effort? What would one of them do after a rebuild....600 Watts per, or more? Worth the efort to get one that would work?

Don't know about the DRS series. The Ser II 400 I have here is just a newer version of the Ser I. If you replace the board you essentially have a SEries I with LED meters.
Would love to work on a DUAL 500. They can be touchy Ed tells me.

 

[Gepetto]

As Lee says, the Phase Linear series 2 quasi-comp is really just window dressing on the Series 1 (new high tech meters) and a cost reduction for the control board which occurred as the era of mass market, low cost integrated circuits ushered in during this time period. It got rid of a lot of discrete components on the board and allowed Phase to lower production costs. Putting the White Oak board in a Series 2 restores it to the original greatness that made Phase Linear famous.

 

[ksrigg]

That is good to know. I was under the impression that a Series II could not be made to work using Joe's Whit Oak PCB. Now I'll be on the lookout for cheapo Series II's as well as Series I's.. Cool stuff. I think a pair of Series II's at the top of a rack of Series I's would look so cool..

 

[laatsch55]

It won't if that Series II is a fully complementary output stage Series II.

 

[ksrigg]

Oh &%!+.......It's always something....plus, after the one I'm trying to get up and running, I'm done for a while. I know I've worn Mark and Joe and you out Lee, and I am sorry for all the questions and stupid mistakes. I've just been trying to do something I'm not really trained to do.

Like I said, my next project is building a Space Shuttle in the back yard..

 

[Gepetto]

Those are next to unobtainium anyway Sutton so it is not a big worry there.

 

[laatsch55]

LMPOAO!!!!!!

Sutton, you are not driving anyone crazy. When you get Joe to postin funnies, that's worth it!!

 

[laatsch55]

Hookay. Havin fun with Don's Ser II. First pics are of the left channel THD & N in a sweep.

What the graph doesn't tell you Bias .380 VDC, offset 16mv DC, Both channels loaded at 8 ohms.

 

[laatsch55]

Now the right channel.

 

[laatsch55]

So the right channel sucks. Here are some pics of the waveforms.. They start out at 80khz and go down to 21 KHZ.
As it went down in frequency, the notch you see disappears and the upper half of the sine wave loses its nice curve and progressively gets pointy-er, until the upper half looks like a 15 degree angle.

 

[laatsch55]

We have all the clues to what is wrong with this. What's your guesses??

 

[mlucitt]

Looks like crossover distortion to me. I would check the bias.

 

[laatsch55]

Bias steady at .380, tracks well with warming and cooling of the fins.

 

[laatsch55]

Here's the right channel tonight, almost identical to the left.

 

[laatsch55]

One last pic before it gets buttoned up and put on the horns. The problem was in the DC protect board. It tracks the DC on the base bus bar , and if it's not right can can severly effect the quality of signal on that channel..

 

[mlucitt]

Can you elaborate on "if it's not right..." What means this? What did you DO to fix it? Inquiring minds want to know.

By the way, that amp looks bee-u-ti-ful.

 

[Gibsonian]

Yes, here also wondering what the cause of the distortion was. Will be interesting too to hear what Don has to say about this amp when he hears it. He has heard a few in his day I reckon.

 

[laatsch55]

This particular amp had his prototype 400 board in it , or close to it anyway, and yes, I found a way to hurt it. I think there is something in the IC that gave way and started bleeding into the base bus bar, but that is pure speculation. To truly quantify that I should have had it wired to the left channel to see if it followed it over. AND, it still operated as intended, just real noisy.