I'm the proud new owner of two pairs of Pluto speakers - SL's design. Their great, they raise the hair on my arms. The only problem is I am getting noise out of them, just barely audible at the listening position (all four of them, exactly the same). I've tenatively solved a ground hum problem, but the speakers hiss. It sounds exactly like tape hiss. I am using a passive pre, and Cambridge Audio's Azur 640C V.2. The hiss stays no matter what I connect the speakers too. Any ideas where the source is? The electronics are all IC based, and the boards fairly simple. I don't see any fault in assembly... Could I have hurt an OPA2134 or a voltage regulator? Poor quaility caps? I have no idea...
Patrick
Patrick
fwiw, this is a link to the design;
http://www.linkwitzlab.com/Pluto/electronics.htm
you can work backwards from the electronic XO and repeatedly ground the inputs to see from which stage the hiss may eminate -- also did you use a printed circuit board? did you use all the bypass caps which Siegfrid recommends?
http://www.linkwitzlab.com/Pluto/electronics.htm
you can work backwards from the electronic XO and repeatedly ground the inputs to see from which stage the hiss may eminate -- also did you use a printed circuit board? did you use all the bypass caps which Siegfrid recommends?
here is the kicker
the hiss seems to eminate from the rca connector. when I remove it and hardwire a cable, the hiss is gone. wtf? is it possible that some small amount of capacitance is causing leakage from ground to signal at high frequencies? im still working, the hiss returns when connected to some components and not others, as does the ground humm. I wonder if these circuits are especially sensitive to noise. can anyone clue me into why there might be leakage across my connector?
I am thinking of building Jon Risch's AC line filter to clean up my mains, which are part of the problem. Does this circuit look like it would clean up the AC well?
http://www.geocities.com/jonrisch/surge.htm
the hiss seems to eminate from the rca connector. when I remove it and hardwire a cable, the hiss is gone. wtf? is it possible that some small amount of capacitance is causing leakage from ground to signal at high frequencies? im still working, the hiss returns when connected to some components and not others, as does the ground humm. I wonder if these circuits are especially sensitive to noise. can anyone clue me into why there might be leakage across my connector?
I am thinking of building Jon Risch's AC line filter to clean up my mains, which are part of the problem. Does this circuit look like it would clean up the AC well?
http://www.geocities.com/jonrisch/surge.htm
Do you have an oscilloscope? Sounds suspiciously like there might be some high frequency oscillation going on. As a quick fix install some resistors (470 ohm - 1k) right at the rca output jacks of your x-over.
Without more information it is hard to really know what is going on.
RCA jacks and plugs don't make noise, although jacks directly grounded to the chassis can cause problems with internal and external ground loops. These should be isolated and grounded at one point - usually the star grounding point. Depending on the dielectric of the jack they can add a significant amount of additional shunt capacitance - if the circuit driving them is marginally stable that in conjunction with the cable capacitance may be enough to make the op-amp driving them oscillate.
Without more information it is hard to really know what is going on.
RCA jacks and plugs don't make noise, although jacks directly grounded to the chassis can cause problems with internal and external ground loops. These should be isolated and grounded at one point - usually the star grounding point. Depending on the dielectric of the jack they can add a significant amount of additional shunt capacitance - if the circuit driving them is marginally stable that in conjunction with the cable capacitance may be enough to make the op-amp driving them oscillate.
Linkwitz said he had heard of low frequency oscillations around 7hz, caused by low quality voltage regulators. I suspect them, but replacing them hasn't fixed it. They are my main suspect, but the really odd thing remains, that if the rca input is disconnected, no hiss. That totally stumps me. I will figure it out.
He also said that using anything 'nicer' than the panasonic caps he suggests would lend no difference to the speakers preformance. He is the boss, but I doubt it - I feel the speakers lack detail, and am looking into switching in blackgates and auricaps for the 70+ panasonic caps. Any thoughts?
He also said that using anything 'nicer' than the panasonic caps he suggests would lend no difference to the speakers preformance. He is the boss, but I doubt it - I feel the speakers lack detail, and am looking into switching in blackgates and auricaps for the 70+ panasonic caps. Any thoughts?
I'd pin down the problem with the cross-over first and then think about upgrades afterwards. Is it possible that the hiss you hear is actually noise from the pre-amplifier or some other source. Commodity op-amps like the TLO84 and LF353 for example are extremely noisy. What out of curiosity is used in the Linkwitz x-o?
Your Pluto lacks detail? I just built a Pluto for my friend. It is one of the best speaker system we ever listen. It is very clean and extremely detail. We are using the cheapest NAD preamp and twisted pair cat5e interconnect to Pluto without shielding.cuibono said:
You should fix all the problems before wasting money to upgrade.
HA!
Hello everyone! It has been a while, and I have beaten my problem - it was so dumb! The electronics were housed inside the wooden speaker stand. The are now in thick metal boxes, and basically don't make any extra sound. Duh.
I have also done a cap upgrade - I replaced every cap with blackgates and auricaps. The price was high ($550), and the change was astounding. Doing this put the speakers where I thought they should be. Totally amazing.
I have only one qualm now - there is a definate lack in depth. Its about 2/3 of what it should be. SL says something similar in his review of them. So, now I want to fix that. I am thinking of adding a lot more capacitance to the PSU. Each channel has about 40000uF right now, and I am thinking of going up to about 110000uF per channel. Do I need to worry about charging current? Similarly, the xfrmr is only 50VA. Could I easily increase this?
Anyway, any suggestions to increase depth would be much appreciated.
Hello everyone! It has been a while, and I have beaten my problem - it was so dumb! The electronics were housed inside the wooden speaker stand. The are now in thick metal boxes, and basically don't make any extra sound. Duh.
I have also done a cap upgrade - I replaced every cap with blackgates and auricaps. The price was high ($550), and the change was astounding. Doing this put the speakers where I thought they should be. Totally amazing.
I have only one qualm now - there is a definate lack in depth. Its about 2/3 of what it should be. SL says something similar in his review of them. So, now I want to fix that. I am thinking of adding a lot more capacitance to the PSU. Each channel has about 40000uF right now, and I am thinking of going up to about 110000uF per channel. Do I need to worry about charging current? Similarly, the xfrmr is only 50VA. Could I easily increase this?
Anyway, any suggestions to increase depth would be much appreciated.
Increasing the capacity of the reservoir capacitors or the power transformer will have zero impact on "depth."
This sounds to me like a room/listener placement issue. You should follow SL's placement recommendations on the PLUTO web page and you will have no problems with "depth."
http://www.linkwitzlab.com/Pluto/intro.htm
Cheers,
Davey.
This sounds to me like a room/listener placement issue. You should follow SL's placement recommendations on the PLUTO web page and you will have no problems with "depth."
http://www.linkwitzlab.com/Pluto/intro.htm
Cheers,
Davey.
you know, I've moved them around a lot, different rooms, room treatments - the image is flattened. The problem is that the low level detail does not recede enough, which I think is a problem with the dynamic range being truncated, hence my thinking of increasing the PSU capacitance. It helped on another project recently. Any more suggestions?
The caps have been in there for a many hundreds of hours - In case anyone is wondering, I'm thinking there is probably a decent amount of distortion coming from the drivers and the many op amp stages (about 10 per channel). I cant change these, and I'm not considering the source or cables. So that leaves miscelaneous stuff, like the PSU...
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