Kevin's "I Want a Phase Linear 700 B White Oaked" thread

[soundude]

WOW, gotta keep me updated....one question, when would you use a 1.3k mod!!!
Scotty i need more power, sorry captain just ain't got it!!

 

[soundude]

I hope Kevin live very close to the power station...gonna need it after your done with his amp...

 

[laatsch55]

John ----DYNAMIC HEADROOM------TRANSIENT RESPONSE-----I personally believe if you have way more power than you need , the transient peaks will be heard. the K's have taken peaks of 800-900 watt range and they live, because it's clean. Also to overcome the inertia of large drivers besides damping factor, if the amp can "Hump up" the response to those transients will be better. I would love to see Joe's board push outputs doing 1,000 watts into 8. Having a problem sourcing the appropriate devices.

 

[soundude]

Yeh thats the problem having with my maggies....planars are know for enormous amouts of headroom but need the power to get them there.
What if you bump up the voltage and parallel more devices, the mj's can haandle close to 200v if not mistaken. will you have to parallel another set of drivers too?
Joe would probably increase the current capablities of the board too, rite?

 

[soundude]

BTW, love those pioneers, had a SA9500II with mosfets and chimney style sinks, rebuilt the enire thing and gave to my insurance agent...couldn't drive any of my speakers so couldn't use anymore.
Love to get one of those Pioneer preamps though,,whats the model so I can look for one.

 

[Gepetto]

The MJs are already seeing over 200V in the 700B application. Remember the rails are +/-100VDC. As an example, that means when the sine wave is at its lowest negative point and getting ready to clip it peaks out at -100V. The return trip (the positive slope of the sine wave) is performed by the upper bank of devices pulling it up towards the positive rail. This means that the upper devices are pulling collector current and they are seeing 200V from collector to emitter.

This is what those Safe Operating Area charts are all about. The MJs are capable of this type of operation for only a small number of milliseconds.

The opposite works the same way when the music is peaking on the positive rail.

So if you extend this example, if the rails were +/-150VDC apiece, transistors for this application would need to be minimum of 350V Vceo in order to survive or else have 2 lesser devices put in series cascode mode.

 

[laatsch55]

BTW, love those pioneers, had a SA9500II with mosfets and chimney style sinks, rebuilt the enire thing and gave to my insurance agent...couldn't drive any of my speakers so couldn't use anymore.
Love to get one of those Pioneer preamps though,,whats the model so I can look for one.

Pioneer Spec 1's. If and when you get one, let me know, I have a list of things to do to make it as good as anything out there.

 

[laatsch55]

or else have 2 lesser devices put in series cascode mode.


Say what?????

 

[Gepetto]

We can talk Lee

 

[laatsch55]

My e-mail is working again.

 

[laatsch55]

I just cleaned 4 of the worst heat sinks i have seen, in 5 minutes, spray and rinse. Holes cleaned and everything.
Got a new socket in, the one next to it looks pretty bad now , so it'll get replaced too.
Gutted the input section. To keep from using a switch in the input circuit I'm going to install another set of input RCA jacks where the switch was. These will be for a direct connection to thge board, bypassing everything. the original set will go through the volume pots.

 

[Gepetto]

Looks like triple bypass surgery Lee

 

[laatsch55]

LOL, yeah a lot of comparisons there, except I don't have a scantily clad hottie wiping my brow,.

 

[soundude]

Joe I thought the devices on the 2 seprate rails operate in a push pull fashion which I thought each rail on see's the 100+ volts of each half of the power supply..confused..
Also aren't the mj's rated at 400v 16amps?

 

[mlucitt]

Lee, what did you use on the heatsinks to get them so clean so fast? I though about putting a set in the wife's dishwasher, but then it occured to me that I prefer to stay alive, she would kill me.

For your high power amp are you thinking complementary? On Semi has the NJL4281D (NPN) and NJL4302 (PNP) devices in TO-264 packages. These are 230W, 350V, 15A audio power transistors with the bias diodes built-in, they call it Thermaltrak I think.

The MJ21196G devices are rated to 250 Volts I believe.

 

[laatsch55]

Yes Mark, that was the preliminary choice. Then Joe said " We'll talk Lee". He's said that before, meaning, don't do anything crazy, I'm workin on something.


The heatsinks were sprayed with Shannon formation crude oil condensate. When natural gas comes out of the ground froma mainly liquid hydrocarbon formation, the gas stream is rich in NGL's(natural gas liquids). These streams contain every aromatic and non-aromatic hydrocarbon compounds separated mainly by their vapor pressure. I suspect what i get when I drain the volume pots at my treaters are mostly, pentane, hexane,serptane, octane, nonane and decane, along with some benzene rings thrown in.The white grease starts flowing immediately upon contact. The trick is to keep spraying till it's off the heatsink as this stuff will actually vaporise and dry in a matter of seconds so ya keep it on the move.

I have a feelin some solvent from Dad's day would be just as effective---good ol Carbontetrachloride.

 

[laatsch55]

kevin, the 700 is an all NPN output stage in an emitter-follower arrangement, with the negative half fed by the inverted driver Q7.

 

[soundude]

Joe just seen the spec sheet for the MJ rated 250 Vceo, thought it was higher..

 

[soundude]

Lee I remember back in the day we use refrigerant 11, trichlorofluoromethane....that cleaned everything until EPA outlawed for cleaning...worked excellent on electrical burnouts, now we have to scrub with brakekleen or acetone...

 

[Gepetto]

Nope John, that is what everyone thinks about push-pull and they wonder why their under rated devices blow up. When you are driving heavily reactive loads like loudspeakers the push has to do a lot of pullng and vice versa.