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  1. pma

    Fast transient in music recordings - tweeter load - amp response

    It is generally acknowledged that music signals do not contain much of high frequencies / fast transients of high amplitude and that the music signal looks like a pink noise. It is also suggested that tweeters do not need to handle much power and that amplifier power capabilities at higher...
  2. pma

    Measurements of speaker cables in frequency and time domain

    Measurements of 6m zip-cord speaker cable in frequency and time domain A controversial theme and I would like to contribute with facts only. I have made measurements on my 6m 2x4mm2 speaker cable and wanted to show the effect of the cable in isolation, however with the cable connected in the...
  3. pma

    Stereophile VAC Sigma 170i integrated amp review

    If I would call something coloured then it would be this amp https://www.stereophile.com/content/vac-sigma-170i-iq-integrated-amplifier-measurements Frequency response flies with dips and peaks +/-3dB into dummy load, https://www.stereophile.com/images/321VAC170fig01.jpg superbly high buzz...
  4. pma

    Comparison of power amplifier distortions and FR into complex speaker dummy load

    Comparison of AIYIMA A07 with DIY class AB amplifier into complex speaker dummy load (and more amps added soon) This is a measurement comparison of AIYIMA A07 amplifier (powered by SMPS Mean Well RS-100-24 27V)...
  5. pma

    DIY 250W/4ohm amplifier based on "blameless" topology, and measurements

    DIY 250W/4ohm power amplifier based on “blameless” topology Hello all, the thread posted here by @sabristol https://www.audiosciencereview.com/forum/index.php?threads/luxman-l-85v-integrated-amplifier.20657/ inspired me to build a new DIY amplifier functional sample. The circuit posted in the...
  6. pma

    Luxman L-509X

    This is Luxman L-509X integrated amplifier and it really looks good and measures well Stereophile measurements https://www.stereophile.com/content/luxman-l-509x-integrated-amplifier-measurements Manufacturer's web info http://www.luxman.com/product/detail.php?id=26
  7. pma

    Olimex USB-ISO Isolator mixed experience

    Olimex USB-ISO isolator Sometimes I need to break the loop created by 2 USB devices on same PC or a ground loop from class I grounded PC to class I grounded amplifier driven from USB DAC. So I bought and inexpensive Olimex USB-ISO and had hoped it could fix an issue if it occurs. But it did...
  8. pma

    PM-H2 headphone amplifier

    PM-H2 headphone amplifier 1. Introduction PM-H2 is a kind of modification of my Dispre 2-JFET preamplifier. It was designed in 2011. The main difference is that PM-H2 uses one pair of Toshiba 2SK170 devices in the differential input stage, not the complementary-differential input quadruple...
  9. pma

    Test of RFI circuit susceptibility to AM modulated signal with 1MHz carrier

    Test of RFI circuit susceptibility to AM modulated signal with 1MHz carrier Well – this was tough. I wanted to test possible susceptibility if input analog circuits to AM modulated signals like AM transmitters etc. Sometimes we hear complaints about audio equipment capturing and demodulating...
  10. pma

    AB(x) testing of Power Amplifiers

    AB(x) testing of Power Amplifiers I had to do it. Once again I was convinced that I hear a difference in a sighted test, so I had to prepare a properly level matched A/B test. Two amplifiers, both of 2 x 50W/4ohm rated continuous sine power. conservatively designed class AB, with...
  11. pma

    DacMagicPlus Filter Mirror Images - Short Study

    DAC filters have been discussed in several threads now. I have decided to measure responses of filters in DacMagicPlus especially with respect to mirror images, that create beats at difference frequency and possible IMD tones in inevitably nonlinear components of the audio chain like speakers...
  12. pma

    50+ years of Sinclair Z-30 amplifier and 40+ years of my DIY mods

    50+ years of Sinclair Z-30 amplifier and 40+ years of my DIY mods It was in 1969 when Sinclair Project 60 kit appeared on the market in UK and it contained Z-30 amplifier modules, advertised as 25W and 50W peak. It also advertised to be “the world's lowest distortion high fidelity amplifier”...
  13. pma

    Can you tell diode limiter distortion in the ABX test (sine, music)?

    Please let me know if you would be interested to participate in the test with diode limiter distortion. BAT Schottky diode is connected in parallel to the output, behind 1k resistor. The resulting distortion at -2dB, -11dB and -21dB is shown in the following plots. The upper (left) channel is...
  14. pma

    Magnat Monitor Supreme 102 speaker (with AIYIMA A07 TPA3255)

    Magnat Monitor Supreme 102 speaker (with AIYIMA A07 TPA3255) As I was unable to live with the sound of JBL Control1 Pro in my workshop, I have decided to buy a pair of Magnat Monitor Supreme 102 small speakers, which was available at about $85 in a local electronics shop, at the price lower...
  15. pma

    Any suggestions for a small, good sounding speaker to my workshop?

    In my little workshop I have JBL Control1 Pro speaker and I am suffering when I listen to it. So I would like to make a change and I would appreciate some suggestions and hints. My requirements are: - small speaker, up to 25 x 15 x 15 cm - power handling at least 50W - low sensitivity is a non...
  16. pma

    Mytek Brooklyn Amp - Stereophile review

    Another interesting class D amplifier with good measurements is definitely Mytek Brooklyn Power Amplifier, as reviewed by Stereophile https://www.stereophile.com/content/mytek-brooklyn-amp-power-amplifier There seems to be a lot of true power together with reasonable measurement results...
  17. pma

    AIYIMA A07 TPA3255 amplifier with MW RS-100-24 SMPS power supply (measurements)

    AIYIMA A07 TPA3255 Amplifier with MW RS-100-24 SMPS Power Supply I have just received the Mean Well RS-100-24 SMPS power supply, connected it to AIYIMA A07 and made a set of measurements and some listening. As the amplifier must be paired with a power supply and these 2 units make a complete...
  18. pma

    Class D AIYIMA A07 amplifier (ABX) listening test

    I was curious if inserting AIYIMA A07 TPA3255 class D amplifier in the D/A – A/D loop would be audible. I tested the amp in another thread and found that the frequency response depends, at higher frequencies, on speaker complex impedance, due to amplifier's output LC filter - that is outside...
  19. pma

    AIYIMA A07 TPA3255 Amplifier Measurements and Review - LM4562 option

    AIYIMA A07 TPA3255 Amplifier Measurements LM4562 option I received my A07 yesterday, on January 6, 2021, shipped from Italy. Purchased at Amazon.de and as stated on their website, it arrived without a power supply. I am testing the A07 with 2 different power supplies. One of them is a linear...
  20. pma

    An attempt to measure headphone (non) linearity

    Based mostly on discussion in this thread https://www.audiosciencereview.com/forum/index.php?threads/stax-tube-amplifier-distortion-vs-solid-state.18832/ I thought about alternative methods to measure headphone linearity. I tried the X-Y plot where on X-axis there is a driving voltage and on...
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