I have been dealing with EMI and RFI since the 60s. I will eventually solve it. I would like to have an underground feed for the main line. Great excuse maybe. Truthfully, I don't need to solve it. My ear needs to be nearly in the driver to hear it. Still, it bugs me. The power company may have a failing transformer. Episodes of voltage fluctuations come and go.
I have been tweaking the system for a few months now. I setup a rack yesterday. Today, I setup a listening chair. Analog audiophiles are coming over to audition the BCD-3/HPA-1/XA25. I suspect that they may rethink their systems.
I have been tweaking the system for a few months now. I setup a rack yesterday. Today, I setup a listening chair. Analog audiophiles are coming over to audition the BCD-3/HPA-1/XA25. I suspect that they may rethink their systems.
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Just for starters. Under the conditions you cite, yes. In fact, I can put my ear to the speaker midrange and, at the same time, break/make contact with a speaker wire at the post and demonstrate the hum being driven by the cable. But it gets worse (more interesting). I can disconnect the speaker cables and the speakers go silent. BUT, if I bridge the bi-wire terminals, the speakers hum. The hum from the low-range, with the speaker cables connected to the speakers (floating, no connection to the XA25) is pure 60 Hz. The hum from the mid-range is more complex. Perhaps the crossover network coming into play. The bottom line, the speakers, with no connections whatsoever, hum when the high/low terminals are bridged. Presumably the mid-range has enough sensitivity to be driven by EMI when all of the internal wiring of the speaker is connected through the crossover networks. Further, I can turn off the breakers for the receptacles/lights in the listening room. The speakers still hum away.Am I missing something? You have your speakers unplugged from the amp with just wires laying on the floor "acting like an antenna" and you hear 60Hz from the midrange?
Frankly, humming speakers, with no external connections, do not surprise me. I acquired a Amateur Radio operators license when I was 12 years old. Then, later in my life, built instrumentation amplifiers feed by up to 30M input impedance. I am well prepared for the frustration, and compromises, that come with EMI/RFI.
I could blame the power company, but this is rarely a fix. Generally, I have had to work around noisy power lines. I know I can fix this, but it is going to take some fancy cabling, grounding, and routing. More fancy. Plus, I am the only one that would know there was a hint of EMI in the system. Unless, an engineer came looking for it.
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maybe trying Tannoy thing - separate binding post on speaker box , connected with speaker basket(s), intended to be connected with amp GND with separate wire
then using coaxial cables inside cab , with screens connected to basket(s)
though , from your words , I can conclude that you already know way more than I will ever know about these things
then using coaxial cables inside cab , with screens connected to basket(s)
though , from your words , I can conclude that you already know way more than I will ever know about these things
Perhaps a wrong conclusion. I know enough to know that I don't know squat. All of cabling, including a 15 ft run of RCA and a 15 ft run of power is "directional." The shields are grounded at one end only. I biased the cabling toward guarding against ground loops. It appears that I opened the door for EMI. I do not like having hardware visible in the sound stage, except for the XA25 on a floor stand with short speaker runs. In fact, a major reason I like the XA25, sonics aside, is that there is not a meter visible in the sound stage. In fact, I wish the indicator light of the XA25 was mid-face. The XA25 splits the base of the listening triangle. I digress.
I have focused on the speaker hum, more as a curiosity. Divide and conquer. When bi-wired (without bridges) with the XA25 connected and powered (but without input connections), the hum at the speakers is no louder than when the speakers are disconnected at the speaker posts and the bridges in place. Thus, the XA25 is dead silent. Plus, the speakers, alone, are dead silent without the bridges in place. Thus, I should be able to make them silent when connected to a powered XA25. Thus, my original question about a chassis ground point on the rear panel.
To move upstream from the speakers. I have 15 ft of power cable running with 15 foot of RCA interconnects along the base boards. The power cable consists of three runs of instrumentation cable. If I wrap the five cables for 15 ft with Velcro rings, there is a slight degree of additional hum in the system. This hum is quickly eliminated by separating the RCAs from the power cable runs by about 2". Thus, I know I can solve this by using wire spreaders akin to spark plug cable routers. Or, perhaps if I ground the shields at both ends I kill the EMI without introducing a ground loops. Or, perhaps I ask my secretary to braid the power cable (studying this possibility).
I put much thought, love, art, and expense (thousands in parts alone) into the interconnects and power cables. There needs to be more time between my ego and the birth of the cables before I can bring myself to mutilate them. I could hide the Teflon jacket of the instrumentation cables with an additional shield but the white Teflon cabling looks terrific and I doubt that double/triple shielding would work anyway. Putting a bra on a 911 comes to mind. Much simpler to use wire spreaders along the baseboard. Maybe I put a model railroad in the listening room and disguise the connections between the rack and the XA25 as power lines. So many ways.
Let's just take a second and put things in perspective. The BCD-3/HPA-1/XA25, as it is currently configured in my listening room, serves as a foundation for the most black system, at any price, that I have ever heard. Whenever, a sound engineer cuts a pickup, rather than fades it, I look toward the rack to verify the indicator lights. This is a new experience with familiar recordings. I am adjusting. Going after a minuscule amount of EMI is mostly a sport.
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I imagine that each of these stages is exemplified by builds discussed on Pass DIYAudio? Might you suggest active device pairings if I wanted to play with a 1-5W output version of this circuit?
It appears that the ouput stage of your amplifier (https://www.diyaudio.com/forums/attachments/pass-labs/729072d1547517850-pass-xa25-abstract-1-asc-jpg) exemplifies Zen V5 (https://www.passdiy.com/download.php?download_file=/images/uploads/project/zen-v5-hires.pdf)?
From the XA25 manual; "The XA25 is "a simple 3 stage circuit with total of three pair of push-pull gain transistors." Your circuit follows this description, two pairs for the front end and one pair for the output? Further, the manual states; "In their ideal state, matched push-pull FETs give perfect 'square law' cancellation of distortion, an effect somewhat spoiled by degenerative Source resistance used to constrain the 'personality' of the devices." As I look at the ZV5 circuit, there is no degenerative source resistance for ZV5 simplified circuit; correct? For the build, R9-12 are sources of degenerative feedback? Is there a PassDIY project that uses two push/pull pairs for front end? I have not found one. Thank you for commenting.
From the XA25 manual; "The XA25 is "a simple 3 stage circuit with total of three pair of push-pull gain transistors." Your circuit follows this description, two pairs for the front end and one pair for the output? Further, the manual states; "In their ideal state, matched push-pull FETs give perfect 'square law' cancellation of distortion, an effect somewhat spoiled by degenerative Source resistance used to constrain the 'personality' of the devices." As I look at the ZV5 circuit, there is no degenerative source resistance for ZV5 simplified circuit; correct? For the build, R9-12 are sources of degenerative feedback? Is there a PassDIY project that uses two push/pull pairs for front end? I have not found one. Thank you for commenting.
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Thank you for providing the related projects. As I was reading reviews for the XA25, one of the reviewers made the comment that the HPA-1 might have been designed with the XA25 in mind. Knowing that I would be running long single-ended interconnects, I chose the HPA-1 over the XP10/12. I don't even own a pair of headphones. I find it interesting that Jam is a main contributor to the the ZV5 thread. Am I wrong or has the ZV5 build been relatively ignored. I don't see where anyone literally built one. Might I be missing a DIYAudio thread?
I realize that the following question should be asked on the ZV5 thread but, the distortion for the ZV5 appears to increase at less then 1.5A. In my naivety, if I want to build a 1 Watt amplifier based on ZV5, can I find a different complementary pair with low distortion at maybe 1A or less?
So I am perhaps wrong about ZV5 being the basis for the XA25 output stage? The ZV5 requires gain by the complementary pair and, thus, is common source. And inverting. The XA25, having two complementary pairs in the front end is apt to be common drain (voltage follower) on the output?
Based on Nelson Pass's original post about XA25 characteristics, is it simply obvious whether the XA25 output is a complementary follower stage or a complementary gain stage? The LH Quam circuit is a common drain and, thus, has gain? Argh! Perhaps if I read the entire BA series and the F5 I will get ahead.
Ignorance is bliss. I simply connect the BA3 front end to a low wattage ZV5 back end and the angels may sing on battery power at my off the grid cabin?
I realize that the following question should be asked on the ZV5 thread but, the distortion for the ZV5 appears to increase at less then 1.5A. In my naivety, if I want to build a 1 Watt amplifier based on ZV5, can I find a different complementary pair with low distortion at maybe 1A or less?
So I am perhaps wrong about ZV5 being the basis for the XA25 output stage? The ZV5 requires gain by the complementary pair and, thus, is common source. And inverting. The XA25, having two complementary pairs in the front end is apt to be common drain (voltage follower) on the output?
Based on Nelson Pass's original post about XA25 characteristics, is it simply obvious whether the XA25 output is a complementary follower stage or a complementary gain stage? The LH Quam circuit is a common drain and, thus, has gain? Argh! Perhaps if I read the entire BA series and the F5 I will get ahead.
Ignorance is bliss. I simply connect the BA3 front end to a low wattage ZV5 back end and the angels may sing on battery power at my off the grid cabin?
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ZV5 is F5
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you asked several questions which lead me to conclusion that , even if I reply on them you'll not understand answer , given even in most simple way , while going simpler than possible is without point
some things can be mixed , some not
you can make new picture with puzzles from different pictures , but tearing puzzles in pieces is counterproductive
for instance - ZV5 (F5) is one whole - input JFets are not just having gain (and being gain stage) but also serve as biasing apparatus fro output stage ..... so tearing them apart is leaving you with two pretty much incomplete parts of construction
so , again , one can mix'n'match different function blocks , while disassemble of function block is ..... demanding higher level of recombination
download all articles from Papasite and read .......
you asked several questions which lead me to conclusion that , even if I reply on them you'll not understand answer , given even in most simple way , while going simpler than possible is without point
some things can be mixed , some not
you can make new picture with puzzles from different pictures , but tearing puzzles in pieces is counterproductive
for instance - ZV5 (F5) is one whole - input JFets are not just having gain (and being gain stage) but also serve as biasing apparatus fro output stage ..... so tearing them apart is leaving you with two pretty much incomplete parts of construction
so , again , one can mix'n'match different function blocks , while disassemble of function block is ..... demanding higher level of recombination
Thank you. I did so about 10 years ago. Obviously did not stick. Will do so again. In the meantime, I think I just need to start frying something up. Very much appreciate everyone's help and comments.
The XA25 has a follower output stage (Common Drain), which provides
current but not voltage gain.
