Kevin's PL400 Upgrade
- Thread starter mlucitt
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Thanks for the responses.
To answer some questions posed by Don:
1) Amp is stable, DC offset is low, 4 mV and 8 mV.
2) Pretty sure no subsonic stuff being delivered by source. Happens on phono and CD both, and with phono I always use the subsonic filter, which is recently recapped so pretty sure all is well here.
3) Problem is tied to volume level (output voltage). Does not happen until the meter needles are hugging the right side.
4) Amp is outputting from however low my source is capable to 120Hz (all sub duty)
Lee is sending me another board to try, will report back after the 26th on how I come out.
To answer some questions posed by Don:
1) Amp is stable, DC offset is low, 4 mV and 8 mV.
2) Pretty sure no subsonic stuff being delivered by source. Happens on phono and CD both, and with phono I always use the subsonic filter, which is recently recapped so pretty sure all is well here.
3) Problem is tied to volume level (output voltage). Does not happen until the meter needles are hugging the right side.
4) Amp is outputting from however low my source is capable to 120Hz (all sub duty)
Lee is sending me another board to try, will report back after the 26th on how I come out.
I was not happy with the way the 40mm capacitors from Joe's kit fit into the original 50mm clamps so I ordered new 40mm clamps from Mouser. I should get them by the end of the week. After they are installed, the amp will be ready to go. In the meantime, I will measure the box size and weight and send you that information.
How are the big silver caps held in place in your amp, just the double stick tape?
Thanks,
How are the big silver caps held in place in your amp, just the double stick tape?
Thanks,
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You're running a 700 with the white oak board right? I don't think changing the board is going to make a difference. Please confirm. Any other details?
Note to all. If at any time the relay trips and fuses blow it's almost certainly due to a blown channel. Do not get in a hurry and shove new fuses in it. Disconnect all inputs and outputs before attempting to power up again wiht new fuses.
Note to all. If at any time the relay trips and fuses blow it's almost certainly due to a blown channel. Do not get in a hurry and shove new fuses in it. Disconnect all inputs and outputs before attempting to power up again wiht new fuses.
I wasn't about to put my ESS's or JBL's on it. My 400II that is on the way to Lee went was blown when I got it. I put used MJ15024's in it when I fixed it because it was mine. A few months later it went down while idling. Of course I initially blamed my high school son. No damage to the ESS's though. It reaffirmed my position about changing out all outputs.
I checked the inductive kick with the RC network. Peak was about 100V. Diode definitely slowed down the relay. I wanted all the speed I could get.
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Hey, I just had an idea. With those of us in VA (Wise, Powhatan, Manassas) and folks from other countries such as Oh-hio, Illi-noise, and Why-oming - why don't we start a group meeting. Like AA for Phase Linear equipment. We could start a Phase Linear User Group (PLUG). Hold our first meeting in some central location, like Virginia...
Sounds like a plan to me. We could each bfing one amp and a pair of speakers, but I don't know where we would be allowed to meet. The decibel levels would limit the renting of a hotel conference room. Would be lots of fun though. Probably a central location would be around Roanoke.. I'l put my PLUG in for that...
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I will run the relay cut out test case through the SPICE model that I have built for the Phase Linear amp and advise if it discloses much. My hunch (and just a hunch right now) is that at VERY high output levels (like you guys like to run them) that the artifacts of the quasi-complementary design of this amp is factoring in. The low side of the amp drives much better than the high side in the Phase Linear amp owing to the basic design of the amp output stage. The upper side is a true emitter follower configuration whereas the bottom side starts with an emitter follower but then follows up with a common emitter configuration. This configuration can easily be driven into complete saturation because the base drive for the RCA410 (Q12) and MJ15024 (Q14) output transistors is derived from current passing through the speaker itself from the ground terminal of the speaker to the negative supply via the base emitter junction of the 2 output drivers limited primarily by R34||R35. The top half of the amp however relies on base drive (for Q11 and Q13) derived from the current flowing through R17 in series with R18 plus the bootstrap current from C11 in conjunction with R18. This upper half has a much more difficult time saturating Q11 and Q13 than the lower half of the amp output stage. Surmise that when driven to excessive levels that signal assymetry starts to occur near clip that when integrated (averaged) by the relay disconnect circuits appears to be DC voltage on the speaker when it is really a large scale AC signal with a slight imbalance in signal quality (distortion). If the circuit on Don's board is the same as the original PL200 Series 2, I have that schematic and can add it to my SPICE model and see if it predicts that this condition occurs at very high signal levels. If it does, then perhaps we can experiment a bit more with the Phase Linear bootstrap circuit to see if we can get a little more juice out of it. Regardless, once clip is hit, the final small imbalances between the plus and minus rail will be seen at the output and trip the relay circuit as well.
Clear as mud guys??
Clear as mud guys??
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- Joined
- Jan 14, 2011
- Messages
- 74,948
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof