phase linear 400

And be very careful. The meter movements are very delicate.

I have managed to fix a couple meters that had jumped the gimbals due to a big mechanical shock.
 
Well here's an interesting development. I closed her back up and gave a listen. It appears to me that the right one is working just fine, but the left one is WAY oversensitive. The right one (the one that I thought was broken) is dancing between -10 and -20. The left one is constantly pegged.
 

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Something isn't sounding quite right to me. Seems like I'm missing frequencies below 40hz and when I turn it up there seems to be a bit of distortion. Or maybe that was the left meter pegging...
 
Does that meter peg with the RCAs and speaker wires disconnected? Put it back on bench and double check bias and DC on the speaker terminals per the build instructions. If all good, try it with meters disconnected and connected. Try it in both systems to isolate the issue.
 
The meters seem to be responding in synch with the music. They are steady at 0 (-20) on power on through the start of play back. Then when the music starts the left meter has a sweeet spot where if the volume is low enough (background music level), it appears to have accurate movement. It's a narrow sweet spot though. A little less volume and it stays put at 0. Normal listening levels (for me) have it bouncing off of the rev limiter, while the right channel seems to be responding accurately. It's bouncing so hard off of the right stop that I think that is the distortion/rattle that I was hearing last night.

I'm going to lower the sensitivity on the left meter as much as possible through the jumpers (which is the least sensitive setting?) and maximize sensitivity on the right meter and see if I can even them out a bit. I'm also considering running the amp on my bench with the meter outputs connected to my oscilloscope where I can see what the meters are getting fed. I'm assuming it's the meter, but who knows, maybe I have a output signal disparity between the two channels to the meter (both speakers have equal volume and soundstage/imaging is excellent).
 
ABebar said:
The meters seem to be responding in synch with the music. They are steady at 0 (-20) on power on through the start of play back. Then when the music starts the left meter has a sweeet spot where if the volume is low enough (background music level), it appears to have accurate movement. It's a narrow sweet spot though. A little less volume and it stays put at 0. Normal listening levels (for me) have it bouncing off of the rev limiter, while the right channel seems to be responding accurately. It's bouncing so hard off of the right stop that I think that is the distortion/rattle that I was hearing last night.

I'm going to lower the sensitivity on the left meter as much as possible through the jumpers (which is the least sensitive setting?) and maximize sensitivity on the right meter and see if I can even them out a bit. I'm also considering running the amp on my bench with the meter outputs connected to my oscilloscope where I can see what the meters are getting fed. I'm assuming it's the meter, but who knows, maybe I have a output signal disparity between the two channels to the meter (both speakers have equal volume and soundstage/imaging is excellent).
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Are you sure you did not inadvertently short a left meter terminal to the cap hold down plate or other internal item upon reassembly?
 
My 400 Series 1 WOPL is a 8 fin with the Dixson meters. They're not very accurate, the 100 marking on the meter is supposed to represent 100 watts, not 100%. They do swing evenly, but I feel they really don't track power output well. This is why I prefer the Series 2 digital Cylon meters.
First thing to look for, is a meter stud contacting the copper buss bar or aluminum plate holding the storage caps? Joe was on same track.
 
Adam
You should post a picture of the transformer internal section of your amp so we can see if we can help you. You have posted very limited pictures so cannot tell if the setup in that area is correct.
 
Wow, you guys are good at this. You could DEFINATELY be on to something here... Take a look at the attached. I took this when I was about to close it up on Tuesday evening. It does appear that there is the potential for a short of the meter input to the capacitor hold down plate.
 

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I could easily shift that plate over using the other mounting hole. I could also add some electrical tape to the backside of that meter input stud. I'll take the top plate off and get a good pic before I remove the face. I should be able to determine immediately if there is contact or not.
Thanks!
 
Overall, while I was not blown away with the bass response, I was impressed with the separation, clarity, and imaging that I got out of my short 2-3 song listening session. The dual mono setup is obviously a vast improvement over the separation I was getting out of my old Yamaha 70wpc amp.
Looking forward to acting on any suggestions you may have to help improve performance from here. I was going to swap cables and speakers tonight to see if there is any change. Looks like meter work will be my first order of business.
 
ABebar said:
Overall, while I was not blown away with the bass response, I was impressed with the separation, clarity, and imaging that I got out of my short 2-3 song listening session. The dual mono setup is obviously a vast improvement over the separation I was getting out of my old Yamaha 70wpc amp.
Looking forward to acting on any suggestions you may have to help improve performance from here. I was going to swap cables and speakers tonight to see if there is any change. Looks like meter work will be my first order of business.
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Are your speakers capable of reproducing those frequencies? Most sealed cabinets roll off fast around 60hz. That WOPL should be able melt most home audio speakers without breaking a sweat!
 
ABebar said:
Wow, you guys are good at this. You could DEFINATELY be on to something here... Take a look at the attached. I took this when I was about to close it up on Tuesday evening. It does appear that there is the potential for a short of the meter input to the capacitor hold down plate.
Click to expand...
The plate should be all the way against the left side wall Adam. We are not good, we just know the design intent
 
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