+ Reply to Thread
Page 3 of 8 FirstFirst 12345 ... LastLast
Results 21 to 30 of 75

Thread: Mythbusters does Hi-Fi.

  1. #21
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 37,778
    I'm Martin.

    Default

    I think I'm following so far.
    Current Lash Up:

    TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.

  2. #22
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,848
    I'm openingabottleofwine.

    Default

    Agreed! Looking forward to Part II.
    Barry

  3. #23
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

    Default

    Quote Originally Posted by Barry View Post
    Agreed! Looking forward to Part II.
    Yer a bleedin' EE yerself IIRC you don't need it explaining Barry!
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  4. #24
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

    Default

    Added another paragraph to that first bit.
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  5. #25
    Join Date: Jul 2016

    Location: Welsh Borders

    Posts: 283
    I'm Gary.

    Default

    Very good, Jez! A scorching start. You must have done this before?
    I have a Q: in your example the " sag" in power supply stiffness had the effect of introducing a false signal of 0.1v at the first of the three amplification stages. Given that all three amplification stages run off the same power supply, they will - as you mentioned - all be experiencing the same sag. Does that mean that stage 2 and stage 3 will also be introducing their own false signals, compounding the one introduced at stage 1? And those false signals all get amplified in each subsequent stage they pass through? It's a wonder there is any audible music signal left!
    IB

    Quote Originally Posted by Arkless Electronics View Post
    Sorry if this is patronising to many but to begin with I'll assume zero knowledge on the part of the reader...

    So what is a power supply and what qualities do we want from it?

    Everything powered by the mains needs a PSU (power supply unit) and even in the case of battery power, the batteries are then the power supply. A PSU is NOT only an external box which supplies power to another piece of equipment. It will often be built into the equipment and even in the case of an external PSU there will often be more circuitry associated with the power supply within the main unit.

    The perfect power supply will give a precise DC voltage which does not vary under any circumstances and has zero noise superimposed on the DC.

    Imagine a perfect 10V DC PSU. The 10V output would not vary with time, temperature, incoming mains voltage (if it's mains powered of course) and most importantly it will not vary with the current being drawn from it by the load.

    This last quality is known as a PSU's regulation. All PSU's, even batteries, have as one of their characteristics their regulation but this is not the same thing as having a voltage regulator... other terms such as the "stiffness" of a supply, its internal resistance, source resistance or source impedance all refer to basically the same thing. The perfect supply has 0% regulation, meaning infinitesimally low internal resistance. This means it would maintain exactly 10V whether it had no load on it or 1000 Amps being drawn from it. Think of the 10V being 10 foot of rope. It should stay 10 foot exactly even with 1000kg weight hanging of it. (I shall use analogy here and there to try and make things easier to grasp so apologies for the clumsiness of some of them! In this case the less than perfect rope would stretch to more than 10' but the less than perfect supply "sags" under the load and gets to be less than 10V...)

    Why is it so important that a PSU be "stiff", have excellent regulation etc?

    Imagine an amplifier with 3 stages of amplification, typically that means that at it's most basic we have 3 transistors (or valves) each with a particular gain (amplification factor). Lets say each has x 10 amplification so in total we have 10x10x10 = 1000 x amplification of the input signal.

    Now the problem is that an amplifier has more inputs than just the one labelled "input"... The point where each of the 3 stages takes its power from the PSU is also an "input", of much less sensitivity than the actual input but present nonetheless. Imagine that a 1mV signal in the form of a kick drum beat from a cartridge is the input. This will be amplified 1000 x and appear at the output as a 1V kick drum beat. The final stage obviously has the biggest signal as it's amplified by 10 by each stage and to give this 1V signal out the final stage must draw the most current from the PSU.

    If the PSU has poor regulation, ie is not "stiff" and has a high source resistance, then the 10V from the PSU will drop to lets say 9.9V in sympathy with the drum beat... The first stage is being powered from the same PSU and so it also experiences this drop down to 9.9V. The original 10V minus the drop to 9.9V gives us in effect another signal to the first stage of 10-9.9=0.1V or 100mV, 100 x more than the 1mV actual input from the cartridge! This will mainly appear at the output of the first stage, forgoing its x 10 amplification but still then being amplified by 100 x by the two following x10 stages.... In a severe case such as the example given we get "howl round" in the same way as a mic too close to the speaker in a PA system, but of course all happening in the electrical domain rather than via sound. (it would most often be at an ultrasonic frequency beyond even bat hearing in practice).

    Noise on the DC Voltage gets into the circuitry by the same method.... Note. In electronics "noise" refers to anything present which should not be there but is not related to the signal. So we mean mains hum at 50Hz, the frequency doubled rectification products at 100Hz, clicks pops, hiss etc etc

    Now, depending on circuit topology, real amplifier stages vary hugely in how susceptible to the above problems they are... in the degree to which their power input is also a signal input if you like. This gives us a figure called Power Supply Rejection Ratio, or PSRR. As a brazen generalisation, the simplest "purest" circuits with the fewest parts tend to have the worst PSRR (with the exception of a simple triode valve stage, which can have a useful degree of PSRR inherent to it. Still not that good in this respect though) and much more complicated circuitry is needed to give better inherent PSRR. Op amps tend to have extremely good PSRR.

    At the two extremes a very simple purist input stage for a very high gain circuit like a phono stage could require a really superb PSU to even work without obvious mains hum, hiss and pops and a state of the art PSU to sound really good. whereas at the other extreme some op amp circuitry could be powered by a really crap PSU with poor regulation and loads of noise and yet be impervious to it.

    Sorry to technical types for all the ifs, buts, caveats etc I've glossed over or not mentioned but this is aimed at the layman.

    I'll let folks absorb that and answer any questions arising, things needing clarification etc before moving on

  6. #26
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,848
    I'm openingabottleofwine.

    Default

    Quote Originally Posted by Arkless Electronics View Post
    Yer a bleedin' EE yerself IIRC you don't need it explaining Barry!
    My post was in support of what Anthony said.

    Yes, I spent 30 years working at an electronocs research laboratory, but my work there was in the design of microwave components (mostly filters) for radar and communications systems. My understanding of electronic circuitry is somewhat basic, and is largely what was taught to me for my undergraduate physics degree.
    Barry

  7. #27
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

    Default

    Quote Originally Posted by Barry View Post
    My post was in support of what Anthony said.

    Yes, I spent 30 years working at an electronocs research laboratory, but my work there was in the design of microwave components (mostly filters) for radar and communications systems. My understanding of electronic circuitry is somewhat basic, and is largely what was taught to me for my undergraduate physics degree.
    Aha a plumber
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  8. #28
    Join Date: Jan 2009

    Location: Essex

    Posts: 31,848
    I'm openingabottleofwine.

    Default

    Quote Originally Posted by Arkless Electronics View Post
    Aha a plumber
    Not necessarily, though my first filter design was about 5' long and had to handle a peak power of 1 Megawatt. My second design though required a microscope for assembly!
    Barry

  9. #29
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

    Default

    Quote Originally Posted by Infinitely Baffled View Post
    Very good, Jez! A scorching start. You must have done this before?
    I have a Q: in your example the " sag" in power supply stiffness had the effect of introducing a false signal of 0.1v at the first of the three amplification stages. Given that all three amplification stages run off the same power supply, they will - as you mentioned - all be experiencing the same sag. Does that mean that stage 2 and stage 3 will also be introducing their own false signals, compounding the one introduced at stage 1? And those false signals all get amplified in each subsequent stage they pass through? It's a wonder there is any audible music signal left!
    IB
    Yes that's spot on Gary Then it it's stereo and all stages are working from one supply.....

    I'll throw a spanner in the works by saying that it all happens at t'other end of each stage as well... ie where each stage goes to earth... which is why good grounding practice is critical in hi fi and sometimes regarded as a "black art"... but that's for another day and the pub is beckoning me right now
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  10. #30
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

    Default

    Quote Originally Posted by Barry View Post
    Not necessarily, though my first filter design was about 5' long and had to handle a peak power of 1 Megawatt. My second design though required a microscope for assembly!
    Yeah such a different field of electronics it makes the brain hurt that they're part of the same subject... I recall hand tuning interdigital microwave filters on Duroid whilst monitoring S parameters on a VNA in a previous life but I wouldn't pretend any design expertise in that field
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

+ Reply to Thread
Page 3 of 8 FirstFirst 12345 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •