Sutton's Phase Linear, White Oak 500

[Skratch]

Lee, On your yellow sheet that you sent me it must have gotten wet. I was trying to read the bottom where you wrote the pin outs for TIS-97, TIS-93 and MPS-A93. Looks like TIS-97 is CBE TIS-93 is CBE and MPS-A93 is EBC. Is that correct. Thanks Mark

 

[Gepetto]

Correct Mark, datasheets attached for your reference

 

[mlucitt]

The full wave rectification period between charge deposits at 60 Hz is 8.333 milliseconds by the way. 1/60 = 16.666 milliseconds and there are 2 charge periods with full wave rectification (one for the positive half of the AC cycle and one for the negative half) leading to the charge deposit on the caps every 8.333 milliseconds. One of the advantages of larger caps is the ripple reduction that they afford, esp at higher frequencies which means the amp has a better chance of rejecting these input disturbances given the power supply rejection ratio inherent to the amp. The biggest advantage I have seen is replacing OLD dried out caps with NEW vital caps. Modern caps are generally made better and have much lower ESR than the old ones used 30+ years ago. This help in the high frequency rejection department helps the amp out in the area that it can least defend itself.

Thanks for chiming in Joe, I multiplied and I should have divided.

Mark

 

[Skratch]

Joe, Thanks for the info. Mark

 

[Skratch]

Put the board from Lee in this morning, sounds great. Biased at 400. Offset L 4 R 6. Put all new transistors and caps from Lee in.

 

[Skratch]

On a 400 what should the output voltage on the speaker terminals be when the VU meters are at 0

 

[laatsch55]

Not bad offset Lad. Keeping the bias that high will generate a lolt of unnecessary heat. ED Blackwood and Dean, set the bias with a scope and distortion analyzer by watching the "notch" on the scope while adjusting. So they in essence adjust bioas for the lowest crossover distortion point. ED tells me that 99.9999999% are at .380 volts DC after all that.

 

[laatsch55]

Skratch, depends on how hard someone has the hold down screws tightened. That's why I started to incorporate those 1/16 inch aluminum plates, to spread the load and avoid that pinchdown. Remember the PL meters were the worst of the worst, even then and they haven't got better with time. To calibrate, adjust the resistor while holding rated output on an 8 ohm load to reflect 0db on the meter.

 

[laatsch55]

Did you do the 1N4148's on the back of the board??

 

[Skratch]

Lee Yes I put the diodes across C6. Reset bias at 380. I read on Joes site that you test meters by using a 1.5 AA battery in series with a 390 ohm resistor you should be at -4 db. I had to use a 2200 ohm resistor to get there. I tested them out of the face plate and they both were the same. When I ran the amp into a 8 ohm load, both channels loaded, I was at 23 volts output and the meters were at 0 db. The amp clipped at 45 volts

 

[laatsch55]

QWere you at +3 when you clipped??

 

[mlucitt]

Today is a good day. Beer from Germany, Japanese caps mailed from Portugal for an amplifier made in the good ol' USA.
[attachment=0:2rq5do22]Beer and Caps.jpg[/attachment:2rq5do22]

 

[laatsch55]

50 at 470 BG":SSSSSS>????? Aw man!!!!

 

[Skratch]

Lee It was PEGGED. Going to see what the voltage is at + 3 db

 

[laatsch55]

Skratch, not much to be done other than change out that resistor till it comes in range.

 

[Skratch]

Lee Should it be at +3db when it is at full power?

 

[laatsch55]

Yes Skratch.

 

[Skratch]

Thanks Lee Did you get the envelope from me. I am going to make some new face plates, was wondering if their is any better meters that can be used

 

[laatsch55]

Sure did Skratch. Therte are still some old Series I meters around, the small ones with the teardrop pointer, made in Japan, 10 times the meter the Dixon or Jewells were.

So, gonna thread that faceplate adventure???

 

[Skratch]

We make a lot of aluminum molds for thermoforming and have 8 HAAS CNC machining centers. Ordered material to make 20 face plates. I have a friend who will put the brushed finish and silk screen them. Going to make a few black face plated with white lettering also.