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

[laatsch55]

Rest of the test results-----Phase Shift----????-Zilch?

 

[laatsch55]

Signal to noise ratio----

 

[laatsch55]

THD & N at 1 watt into 8 ohms.....

 

[laatsch55]

My idea of running 2 separate RCA jacks, 1 set for direct to board connection, 1 set for routing through the volume pots, DID NOT WORK. Having the 2 sources join up at the board input solder pads---even though the other set was empty--we had a lot of feedback coming from ground I believe.
I will now have a double throw/single pole switch for each channel instead of 2 separate sets of input jacks. Switching 1 will totally isolate the other.

 

[soundude]

Lee did you shunt the direct inputs with a resistor to ground, say 47K to close the loop when not used?
Basically volume controls act as shunts, but you have 2 input jacks one norm. and the othe direct...?
If i understand you are feeding the directs straight from joes board, rite?
Think the R/C network works the same when switch is in normal position, R/C is in, direct R/C is shorted.
Did you install the coupling caps on the back plane, rail to ground? I had alot of noise from that!

 

[laatsch55]

Correct John , the R/C network is switched in or out. That exists no more on this iteration of amp. I was trying to isolate the choices without a switch , which , can over time, have non-glorious consequences on the music.

 

[laatsch55]

No shunting, no capping, no clothes much at all. Needed to see how it sounded without that stuff. Now we work our way back in.

 

[soundude]

Ya might want to throw on some clothes then, you drip any solder and it might land somewhere important!!! LOL, Like on the Kitty!! The resistor always worked for me and it was common value of 47K...can't hurt..

 

[laatsch55]

Why tie ground to the hot with a resistor?? IIRC, the rail caps were .33 at 100??

 

[kevin]

Ya might want to throw on some clothes then, you drip any solder and it might land somewhere important!!! LOL, Like on the Kitty!! The resistor always worked for me and it was common value of 47K...can't hurt..

Hold on now !!!! something here just dont sound right..... Unless of course you were talking about the cat ????????

 

[mlucitt]

I took the R/C circuit out of my PL 700B and ran the inputs direct to the volume pots, careful to bring the amplifier input signal into one side of the pot with ground on the other and the wiper going to the board. I have seen many amps with the amplifier input signal going to the wiper and that is just silly.

I left the Zobel network in place on the outputs because I think it is good to roll off the power above 318kHz!

 

[soundude]

Lee, the resistor wil close the loop from rf injecting into the open circuit, the resistor will close the loop, if you think about it the r/c network does the same thing in the normal posistion. the resistor doesnt seem to have a effect on the sound quality.
I dont know kev, Lee has you amp naked..LOL.seems the cat wears the boots on Lee's bench...

 

[soundude]

[attachment=0:3tt0ehmc]puss-in-boots.png[/attachment:3tt0ehmc]

 

[laatsch55]

The zoebel network is on the DC PCB.

 

[laatsch55]

Johnny D That's cold Man!!!

 

[laatsch55]

I have the amp hooked to a small Koss speaker, without a generator input I have some buzz, hook my scope to it and the buzz dies, scope off buzz comes back.

 

[soundude]

Lee I had that same problem, take a jumper and connect face to ground in amp, the pots pick up hum if the face isnt mounted to chassis....I clipped test jumper from meter mounting screw cause its so long and clipped other end to strap holding in caps, but any clean spot on chassis should work. Try that...

 

[laatsch55]

Yep, faceplate was off being Jani-ized. Pots flapping in the breeze.

 

[soundude]

Lee you off for holiday today? Get alot done...did you do a load share test?

 

[kevin]

Heck !! I remember when a little BUZZ was a good thing !! lol