Sutton's Phased Linear White Oaked 1000 Rigg

[laatsch55]

I don't use the lighted magnifier.......YET.......I am nearsighted so the up close stuff i have to take my glasses off. The board takes 3 hours to do, from unpacking the goodies and bending leads to popping on the heatsinks. Anty office supply store should have those lights Sutton.

 

[ksrigg]

I have got to do something. I can see stuff far away, but not up close. Reading glasses they call them here in the hills, is what I use. I do need to do a little work to finish soldering and re-checking my M-125 monoblocks...and it would be nice to be able to see what I am doing for a change. I'm going to have to get a magnifier, plus I'd love th=o have a PCB Holder, but I've done so few, I don't really need one. I see theat you have the tube premap from Yaqin, Lee. I sent one to Roy at Vacuum Tube Audio who changed the couling caps to Sonicaps, and the resistors to Mills...also the voltage to the 12AU7's is too high, and he reduced the voltage to 12.6V. They were getting something like 13.6 or thereabouts. He wanted to put his PCB in the pre, and turn it inot a pure linestage amp, but I wanted to keep the phono circuit. Maybe I made a mistake...You may want to mail Roy and see what he says about mods. He is modding Transcendant Preamps, and is looking into modding the Yaqin MS-12B which is wht you have, rebadged for the Canadian Company which is selling it in North America.

How goes the 1000B and the 500 SerI projects?

 

[speakerman1]

My magnifier wasn't cheap at all. Yes that is a Grant Fidelity phono amp. To me the Berelli tubed phono is better if you roll the tube.

Larry

 

[jbeckva]

Man I know what mean about not being able to see stuff up close. Interesting part tho... the other day for grins I put my wife's reading glasses on. And then I felt like I had the eyes of a 11 year old!

Gotta get to the eye doctor I guess.. time to wear some "specs" for this getting-older dude...

 

[ksrigg]

What do you think of adding a fan (quiet) into the PL/White Oak amps? As I remember, heat was BLAMED as being a problem with many failures in PL amps. I see that you have some from the heat sink purchase. I love to err on the side of caution. Would it be good to have some air moving inside the amp, or over the transistors of the amp? Maybe this is a dumb question, but I usually run the crap out of amps, and you did ask for my input..What do you think? Worthwhile or not?

 

[speakerman1]

Where would you put a fan? The back is nothing but fins and a small space for your ICs and speaker connections. Mine doesn't get that hot that I have ever noticed. I am just asking here.

Larry

 

[ksrigg]

I really don't know, and don't know if it is even needed. Maybe inside the chassis pushing cooler air, or pulling cooler air across the back plate where the heat sinks and transistors are? I'm just thinking out loud. Or maybe not attached to the chassis or sinks at all, maybe just a plug in from the back of the amp and pointed at the heatsinks..I don't know....

I'm just thinking of the Hafler P-500. it has one (way loud) on the back of the amp that kicks in when the amp gets hot....


In some of the discussion I had read that the PL got hot, and needed dry ice stacked on it in PA racks used for touring bands...

 

[ksrigg]

Plus, if you wanted to put it in one of those nice wooden cabinets, which might look kinda neat, I'm afraid heat might become a real possibility....

 

[speakerman1]

Yes in a case I agree you may need it. When Pink Floyd used them they had roadies with fire extinguishers standing by them. There are a lot of stories about the PLs. I thought about a case at one time then thought about the heat and changed my mind. I think Mark has his in a case. I think in that case I would just get a nice quiet one and blow it over the heat sinks. Have it thermo controlled. Mine w/o the board sounds very good. Lee says it will only get better with the new board. I have the BGs and I'm thinking hard with the Mills resistors. I do need a new meter though.

Larry

 

[mlucitt]

Lee,
That one is a challenge! However, it just means that much more of an improvement. Any more history on that unit? S/N? Working? Smell? We just want to "be" there looking over your shoulder...

Mark

 

[mlucitt]

Speaker,
My PL gets so hot at the top of the heatsinks, I cannot leave my fingers on for more than 2 sec. I think someone said that equates to 150-175 degrees. I also have two 4.5" fans that I intend to run at half speed (wired serial across 120V) to install in the back of the cabinet soon. I have to figure out a way to wire them in and a thermostat would be an ideal way to do it.

Having said that, when I throttle down to a reasonable level, the heatsinks cool off pretty fast right now. I have heard that the secret to keeping the PL is keeping the PL cool.

 

[laatsch55]

The heatsinks are barely adequate when your cranking it. I have air moving over them at all times when at mach 8.

 

[jbeckva]

I can't get past mach 2 without losing my hearing, heheh

 

[mlucitt]

Someone on this board still has their hearing? Stand by for some quantitative measurements...

Doing them now, while listening to some Shpongle!!!

Mark

 

[mlucitt]

OK, here is the test I just ran to help me evaluate the thermostatic switch rating for the dual fans I will install in the back of my White Oak Audio / Phase Linear 900 amplifier. Excuse any typo's my ears are still ringing and my hands are still shaking. It was so loud on the last run that the CD player kept skipping tracks (THAT MY FRIENDS IS LOUD).

Starting conditions:
Amp cold. Thermometer on center depth, middle height, inner side of Channel A Negative Output Transistor Row Heatsink. Ambient temperature 70 degrees F. +/- 0, as indicated on my 0-250 +/- .01 degree F., NIST-traceable calibrated, deadly accurate digital surface thermometer, cleaned with alcohol before each measurement and allowed to reset to ambient temperature after each run. (Quantitative enough for ya?)

Run #1:
Playing Neil Young "Live Rust" at reasonable level. 15 minutes at average of -10 to -7 db as indicated on the meters. Temperature indicated 100.2 degrees F.

Run #2:
Playing Grand Funk "Caught In The Act" at moderate level. 15 minutes at average -5 to -3 db as indicated on the meters. Temperature indicated 134.9 degrees F.

Run #3:
Playing Humble Pie "Rockin' The Filmore" at extreme level. 15 minutes at 0 db as indicated on the meters. The amplifier SHUT DOWN at full volume like someone pulled the plug after 11 minutes! I quickly made a measurement and recorded 159 degrees F. I assume the built-in thermostats are set at 160 degrees F. and one of them worked as designed. I reduced the volume anticipating a restart and the amplifier came back on at 142 degrees F. (probably a 140 degree close). I increased the volume to the previous 0 db level momentarily and the sound was exactly the same as before - LOUD!

Based on this experiment I will likely select the Selco CA-120 1/2" disc thermostat which closes at 120 +/- 7 degrees F. and opens at 90 +/- 10 degrees F. This will keep the fans off most of the time and turn them on at a maximum of 127 degrees F. well below the shutdown temperature.

Thoughts?

Mark

 

[laatsch55]

Mark, a cycling cooling and heating with a thermostatically conrolled fan only exacerbates that semiconductor lifecyling. Semiconductors are rated in heating/cooling cycles, why cycle that by doing the fan turnoff/turnon.
Joe has concurred on this on a question I had a few months ago. If you're going to fan cool it, turn on the fan a, just my and leave it on, just my 2 cents.

 

[mlucitt]

Good point. I never considered the cycling issue. I thought the fan might limit the higher temps while still letting the outputs get some heat. But the thermostat does have a 30 degree swing...

It is much simpler to just let them run when the power is on. I'll try it and see. By the way, the fans I got from Steve Slater at Apex have a blue, brown, green, and yellow wire coming off of them. For 120V operation I need to connect the two stator coils in parallel but the wiring diagram is marked gn, bl, br, and ge. If I assume gn=green, bl=blue, and br=brown, does that mean ge=yellow? Spreken ze deutsch?

Mark

 

[Gepetto]

Recommend that you consider a fan with PWM control that you can continuously vary the speed of. A thermistor on the heatsinks to provide feedback and convert that into a 555 based PWM signal to control the fan in response. The hotter the amp runs, the faster the fan goes and vice versa. That way you get rid of the bang bang type operation that heat cycles the semiconductors. As Lee says, most semiconductor failures are basically mechanical in nature.

 

[laatsch55]

Once again Joe has presented an elegant soluion, Thanks Joe.

 

[ksrigg]

Ssssssshhheeeewwww!!! Right over my head....but I ain't book smart like the rest of you fellers...I'm just an old hillbilly who likes his music loud, and don't want his amp shuttin' down..

Really, Joe must be brilliant to engineer the solutions to all these problems, and I think even ran a SPICE model of the amp to determine the design problems..I just wish I were half as smart and had something to add..

Thank you Joe !!!!