dave

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Everything posted by dave

  1. dave

    Does rfi makes a system sound brighter?

    Thanks, I have an hp8591e that I rescued from work, and a digilent analog discovery, very versatile tool for the lower frequencies. I live in a dip, so RF is not to bad, apart from local transmitter on 96MHz, but the pumping station down the road, I am convinced is doing strange flickering on the mains, suspect a VFD beating with the 50Hz.....
  2. dave

    Does rfi makes a system sound brighter?

    This is an entirely reasonable perspective IMO (of wich I am generaly sympathetic) for some one who obviously has skills in electronics, but who does not hear differences in cables. (This is not supposed to be an attack, I am not sure if there is a name for this type of audiophile, maybe Serge's * would suffice?). But then again, there are people who do hear what really are quite subtle effects. There does not seem to be much widely held "belief"? in the effects Mr Chord seems to suggest, this is the first time it has been thrust into my consciousness, enough to give it serious consideration. It is an interesting theory, but it does seem to have some holes in for me, mainly the known effects of demodulation V what seems to be some amorphous "RFI harshness field". And yes, I have spent countless hours with headphones plugged into multi k£ Rhode & Schwartz EMI receivers, debugging all sorts of emissions problems, mostly caused by inadequate screening curiously.... and occasionally immunity. Anyway, I will be now on the lookout for for this possible cause and effect, and curiously again, I have just been given a DA03A, which I have connected to my TV tuner for DATV radio 3 reception. My stereo has been sounding really quite odd at times since, I have turned it off now and some kind of normality has been restored. (maybe, or was it a coincidence) Oh wait, I used TOSlink. *Serge = certified measurist
  3. dave

    Does rfi makes a system sound brighter?

    It would not produce any output if it was not fed some RFI, I mean digital data.
  4. dave

    Does rfi makes a system sound brighter?

    I used to be a bit suspicious of them when I was a yooth. Now I design high speed amplifiers driving peculiar loads down, shock horror, wires, I see the true need and purpose of the zobel network. As the frequency extends towards the low MHz, it's a jungle. At one frequency the load is open, at another a dead short. It is no wonder the poor amplifier gets confused and starts oscillating. The zobel is an attempt to isolate the amplifier from the anarchy and give it a more predictable environment for its feedback to work, without getting its knickers in a twist.
  5. dave

    Does rfi makes a system sound brighter?

    Early ac coupled solid state amps use a solitary transistor at the input.
  6. dave

    Does rfi makes a system sound brighter?

    Maybe you could qualify that, I thought it was only strange people like me trying to escape from that circuit.
  7. dave

    Does rfi makes a system sound brighter?

    One of the hifi mags, can't remember if it was choice or news, did an RF immunity sweep in their testing once iirc, must have been 20 years or so ago, possibly coinciding with the CE mark. Doesn't seem to have caught on though.
  8. dave

    Does rfi makes a system sound brighter?

    I am not convinced of anything till I have proved it to my self in a quasi controlled manner.... I have no axe to grind incidentally, and thanks for your responses, you seem to be making things that make people happy, and that can't be bad. I feel my self being drawn in to the head fi for a number of reasons, I may be some time, I am a slow reader......
  9. dave

    Does rfi makes a system sound brighter?

    er that would be me actually...
  10. dave

    Does rfi makes a system sound brighter?

    I am not convinced that the effect / improvements are necessarily caused by normally occuring "RFI". My problem is what appears to be apparent repeatability of the phenomenon. RFI of any consequence typically comes from a thing, and would often have a characteristic signature. It is rarely an amorphous background hash, and even if it was, it would be stronger in some areas than others, and probably vary during the working day. These things are regulated an policed, with the possible exception of power line ethernet extenders.
  11. dave

    Does rfi makes a system sound brighter?

    no I am not....
  12. dave

    Does rfi makes a system sound brighter?

    If there is no filter on the input, like an IEC filtered inlet (and they don't block everything), it just comes in on the power cable, then it is inside the essentially Faraday cage.
  13. dave

    Does rfi makes a system sound brighter?

    You did indeed, I think the OP was talking about mains cables, where I guess screening of this type could be of some benefit to stop electrostatic 50Hz interference escaping, but personally I do not really associate that with the term RFI, because it is not RF..... This is an interesting point and reminds me of something I read somewhere, it was the first article I read that made any sense of power cables having a sound. Extrapolating a little, what you are also implying /saying is that if the impedance (resistance) of the path through the screen return of the RCA phono wire is the same, for example, as the resistance of the path between the two pieces of equipment through their respective ground connections, half the return signal will travel through the power cable ground wires.... So the power cable is in the signal path..... Unless one uses proper transformer balanced connections and run all the electronics on their own internal battery power supplies. This stuff makes my head hurt sometimes... I am still a little confused about your IMD statements, to help me understand, I understand IMD in principle, but is that the same the demodulation of an RF carrier, like taxi breakthrough in the old days, or a different effect, which, with typical minuscule levels of EMI, I would tend to agree. should not really be audible.
  14. dave

    Does rfi makes a system sound brighter?

    As soon as I clicked the post button, I started wondering about just this, as I deal with differential signals mostly, so I had to do some rummaging. It seems that the ferrite works on the magnetic field (not the electrostatic) and therefore effects the screen and the core in the same way, so differential signals are unaffected because their sum magnetic field cancels out, but common mode see the higher impedance. So if there is an unbalance in the current the ferrite will not be as effective. There are multiple other factors like the screening effectiveness, and (the dreaded) ground loop currents etc, etc. Just for my own satisfaction I put 10 clip-on ferrites onto a piece of coax. This increased the inductance across the length (measured on the screen) from 9uH to 30uH, but I could see no change in attenuation at randomly selected frequency of 170MHz, or anywhere else for that mater, of the spectrum of my wide-band noise source. I ensured that there was no alternative ground path. In defense of the 640, I had recently replaced the transport... In response to the original poster, partial screening is a bit like trying to stop light with mirrors. It is interesting if it made a repeatable change, but whatever you have done, you have not stopped RFI, just changed the environment. If it made an improvement.
  15. dave

    Does rfi makes a system sound brighter?

    Sorry that wasn't supposed to be a dig, can't stop being an inquisitive engineer type person. If anybody actually knows, with some measurements from whichever domain, would be quite interesting to know what was happening. Did read an interesting article on all the things that can go wrong with USB audio, and why wires are important. https://www.audiostream.com/content/usb-audio-gremlins-exposed-beyond-1s-and-0s-ifi-audio
  16. dave

    Does rfi makes a system sound brighter?

    Enlightened, but do you actually know what happened to what effect the change?
  17. dave

    Does rfi makes a system sound brighter?

    If you add a clip on ferrite to a screened cable, this affects the common mode inductance, not the differential inductance. This will have negligible filtering effect on the audio passing through the wire. I have an amplifier which is very susceptible to RFI, (name and shame, Sony TA F730es). It has a plastic base, and an un earthed 2 core mains cable. It makes random clicks and pops, and took exception to Cambridge audio 640 CD player, so much that I had to go in side it (the CD player) and re arrange the cables to reduce the amount of noise escaping. I don't know if it has a fault some where, but I have never had anything else like it. Mercifully it hasn't exploded in the presence of my mobile phone. Mobile phones are a good source of higher frequency RF....
  18. dave

    The eternal CD player

    I was enjoying pondering another purchase of another semi functioning CD player, when it occurred to me that it would be more sensible to press ahead with my DIY cd player. This consists of a cd rom drive, the root of the eternal, as they are plentiful. Thats the theory anyway. With this end in mind I purchased several Teac 500 reference CD players cause they remind me of my beloved VRDS7 to use as a box. The plan, first stage: CD ROM drive ebay CD ROM drive controller ebay TDA1543 SPDIF DAC mounted in 500 series box. Then evaluate how good is the transport. Second stage Valve current to voltage converter. Third stage own controller firmware. I made a start today!!
  19. dave

    The eternal CD player

    I am a little circumspect about resistive i/v with the 1543, but I must say, that Ciuffoli dac, I bet that sounds absolutely lovely with a bit of SE tube magic in the mix. When I was at university i did a project making a power dac, it started out quite ambitious with a big fast parallel input 16bit DAC, but did a proof of concept with a 1543. That was actually powerful enough, I did quite a lot of measurements and there is definitely an operating point for lowest distortion: That is with a 1.8v Pk to Pk in to 700ohms, which is not that bad actually...... I like the idea of using the DAC as the bottom half of a cascode, but with the experiences of this dac, the first valve is not really doing anything apart from a level shift, it is tempting to try feeding the current in to the inverting input junction (grid) of the second valve........ I concocted an inverting valve opamp circuit using one of the (almost free) PCF valves, which it would be interesting to try in this configuration as well... It is fun and very satisfying, when it works.
  20. dave

    The eternal CD player

    I have one of those dac boards on order.... I have already a couple of Dil devices for a future project, bit it's nice having it all done with the spdif IC. I also seem to be accumulating early Philips players, so some sort of 1541dac, or maybe just straight davizatoring.... Oh project overload. Re sound quality I have a 6x 1543 usb fax with just a resistor I/v, and that sounds quite muggy / clammy in comparison to the cd player. I think the valve stage is helping the sound a lot. Toying withe the valve I/v for that dac as well. But with 6 DACs in parallel, quite juicy.
  21. dave

    The eternal CD player

    The long pause in posting about this player is a very contented silence. It certainly isn't boring any more, the Mrs has listened to 2 whole tracks playing on it (a first, seems she has a preference for DHT SE triodes), and my 2 year old, on one track seems a little uncomfortable, and says "keep me safe".... I have on one occasion almost felt like holding on tho the sofa in a subconscious attempt to deal with the musical assault coming from the speakers.on other disks it is super smooth and seductive. I am interested in Rabski's new DAC project, have been thinking of one using that DAC chip, I can't really imagine anything sounding better some times listening to this one using its 1543. I wonder how much further there is to go...
  22. dave

    DCT (deep cryogenic treatment)

    Probably affecting the dielectric as well.
  23. dave

    Identify this tonearm

    Looks like it was home made by some one (a skilled metal worker) out of bits of other arms and parts made on lathe.
  24. Interesting posting on the archimago blog, re absolute phase and distortion. http://archimago.blogspot.com/2019/06/musings-and-listening-on-absolute.html I have an amp that clips asymmetrically, and when testing it with a pure tone, surprised it was not very audible. I also made a small SE bass guitar amp, that was very unsymmetrical, but sounded lovely - until I put in a stage that inverted the signal, then it sounded crap.....
  25. dave

    The ‘end game’?

    I have all the parts to build the "dark night(s)" (of the soul, not bat man) full range speaker, my only worry is that they will be a bit big, and extremely heavy (4 woofers each), and I am not sure how they will practically integrate in to my strange shape room. I will never stop making things, probably, but that is the big one....... Also a tube-transistor hybrid power amp is always being refined on the mental back burner.