HiEnd la pret de doar un dolar ...

[sesebe]

Iesirea de casti din DAC-ul meu este realizata cu acest integrat.

Suna destul de bine si nu sughita nici cind pun boxele la iesire (3-18ohm in banda audio). Masurarea impedantei boxelor o fac cu iesirea de casti a DAC-ului.

[hpavictor]

Acum 4 ore, Alin_cj a spus:

Ce ziceti de acest "hi end" la un dolar si jumatate? Sau nu se califica pentru ca are curentul de repaus mic?

 

TPA6120A2(ACTIVE)High Fidelity Stereo Headphone Amplifier

• SNR of 128dB A-Weighted.
• THD of 112.5dB
• Current-Feedback Architecture
• Output Voltage Noise of 0.9µV_rms at 
  Gain = 1V/V (16Ω Load)
• Power Supply Range: ±5V to ±15V
• 1300V/µs Slew Rate
• Can be configured for Single Ended or Differential 
  Inputs
• Independent Power Supplies for Low Crosstalk

Este o excepție benefică în lumea audio .

Foarte bun spre senzațional .

Nu doresc să dezvolt subiectul , cine își amintește ce am comentat despre acest integrat uluitor  acum ceva timp , bine , cine nu ... ghinion , vorba lu' 6 case adică @nicolicea de Sibiu  .

[+_Florin_+]

Nu am testat acest integrat, dar orientandu-mă după datele postate pare suficient de audiofil. Îmi place (În mod special) viteza de creștere a impulsului  . 

Editat Iunie 14, 2019 de +_Florin_+

[sesebe]

Viteza aia nu te ajuta "direct"in reproducerea sunetului pt ca nu exista zgomote (ca sa nu zic sunete) in natura care sa aiba o viteza asa de mare de variatie, poate cu exceptia exploziilor dar pe alea oricum nu le poti reproduce corect.

Slew-rate-ul mare te poate ajuta totusi dar mult mai subtil si nu cum cred majoritatea.

[franzm]

Da, da. exploziile. 1812, piesa de rezistenta pentru orice inginer de sunet.

[sesebe]

Destul de dificil de reprodus corect............

[hpavictor]

O pagina de istorie , care nu mai uimeste pe nimeni ...

Oare de crede lumea ca este inca o referinta in HiFi ? 

Exista amplificatoare DIY cu performante excelente , intotdeuna e loc de mai bine  .

In atasament aveti schema in format  .asc , pentru entuziastii amatori de simulari .

Quad405.zip

[+_Florin_+]

Eu percep "slew rate" ca parametru ce caracterizează amplificatorul dpdv al răspunsului său la semnal dreptunghiular. Cu cât e mai bun (raspunsul) cu atât mai bine. Că n-or exista pasaje muzicale obișnuite care să necesite viteze de mii de volți pe microsecundă, e altă poveste. Dar audiofilul e mulțumit când "impinge" performanțele amplificatorului dincolo de cele necesare, astfel încât e sigur că semnalele audio vor fi redate (cât mai) corect.

 

Integratul in cauză pare a avea un slew rate excelent pentru un amplificator siliconat și mai ales "integrat".

Slew-rate depinde atât de Ft tranzistoarelor cat si de configurația reacțiilor negative. În principiu, e de evitat un grad mare de reacție negativă globală (pe mai multe etaje) lucru care poate fi compensat prin reacții negative locale, pe etaje. Așa obținem un procent de distorsiuni redus, combinat cu o viteză de creștere a impulsului ridicată. 

La 15.06.2019 la 0:09, sesebe a spus:

 

Slew-rate-ul mare te poate ajuta totusi dar mult mai subtil si nu cum cred majoritatea.

 

Dacă doriți, vă rog detaliați cele cuprinse în afirmația de mai sus, sunt un audiofil fără "h", deschis la orice afirmație atâta timp cât e argumentată dpdv tehnic.

[sesebe]

Sint propriele mele idei și nici nu as vrea sa stirnesc alte discuții Off-topic aici. Oricum ar fi mult de explicat și sigur se vor găsi haudiofili care sa ma contrazică. 

Sa zicem ca un slew-rate rezonabil de bun este unul de minim 3 ori mai mare decit ce ce iese din calcule în funcție de banda de frecventa și puterea maxima posibila. 

[hpavictor]

Nu e nimic complicat , cel mai bun exemplu poate fi Quad405 , un amplificator deficitar la capitolul SlewRate .

Testul IMD cu  19KHz+20KHz cred ca e convingator ... in prezent , Quad 405 ar fi considerat un gunoi !

Pentru evaluarea performantelor audio , in afara de testul THD , exista si altele cum ar fi IMD ITU-R ( CCIF ) sau IMD SMPTE etc .

Exista si alte teste care " tortureaza " amplificatorul , dar nu sunt recunoscute international , fiind standarde interne ale unor  firme renumite . 

Majoritatea standardelor interne  nu sunt publice  .

THD. Total Harmonic Distortion

What is tested? A form of nonlinearity that causes unwanted signals to be added to the input signal that are harmonically related to it. The spectrum of the output shows added frequency components at 2x the original signal, 3x, 4x, 5x, and so on, but no components at, say, 2.6x the original, or any fractional multiplier, only whole number multipliers.

How is it measured? This technique excites the unit with a single high purity sine wave and then examines the output for evidence of any frequencies other than the one applied. Performing a spectral analysis on this signal (using a spectrum, or FFT analyzer) shows that in addition to the original input sine wave, there are components at harmonic intervals of the input frequency. Total harmonic distortion (THD) is then defined as the ratio of the rms voltage of the harmonics to that of the fundamental component. This is accomplished by using a spectrum analyzer to obtain the level of each harmonic and performing an rms summation. The level is then divided by the fundamental level, and cited as the total harmonic distortion (expressed in percent). Measuring individual harmonics with precision is difficult, tedious, and not commonly done; consequently, THD+N (see below) is the more common test. Caveat Emptor: THD+N is always going to be a larger number than just plain THD. For this reason, unscrupulous (or clever, depending on your viewpoint) manufacturers choose to spec just THD, instead of the more meaningful and easily compared THD+N.

Required Conditions. Since individual harmonic amplitudes are measured, the manufacturer must state the test signal frequency, its level, and the gain conditions set on the tested unit, as well as the number of harmonics measured. Hopefully, it's obvious to the reader that the THD of a 10 kHz signal at a +20 dBu level using maximum gain, is apt to differ from the THD of a 1 kHz signal at a -10 dBV level and unity gain. And more different yet, if one manufacturer measures two harmonics while another measures five.

Full disclosure specs will test harmonic distortion over the entire 20 Hz to 20 kHz audio range (this is done easily by sweeping and plotting the results), at the pro audio level of +4 dBu. For all signal processing equipment, except mic preamps, the preferred gain setting is unity. For mic pre amps, the standard practice is to use maximum gain. Too often THD is spec'd only at 1 kHz, or worst, with no mention of frequency at all, and nothing about level or gain settings, let alone harmonic count.

Correct: THD (5th-order) less than 0.01%, +4 dBu, 20-20 kHz, unity gain

Wrong: THD less than 0.01%

THD+N. Total Harmonic Distortion + Noise

What is tested? Similar to the THD test above, except instead of measuring individual harmonics this tests measures everything added to the input signal. This is a wonderful test since everything that comes out of the unit that isn't the pure test signal is measured and included -- harmonics, hum, noise, RFI, buzz ... everything.

How is it measured? THD+N is the rms summation of all signal components (excluding the fundamental) over some prescribed bandwidth. Distortion analyzers make this measurement by removing the fundamental (using a deep and narrow notch filter) and measuring what's left using a bandwidth filter (typically 22 kHz, 30 kHz or 80 kHz). The remainder contains harmonics as well as random noise and other artifacts.

Weighting filters are rarely used. When they are used, too often it is to hide pronounced AC mains hum artifacts. An exception is the strong argument to use the ITU-R (CCIR) 468 curve because of its proven correlation to what is heard. However, since it adds 12 dB of gain in the critical midband (the whole point) it makes THD+N measurements bigger, so marketeers prevent its widespread use.

[Historical Note: Many old distortion analyzers labeled "THD" actually measured THD+N.]

Required Conditions. Same as THD (frequency, level & gain settings), except instead of stating the number of harmonics measured, the residual noise bandwidth is spec'd, along with whatever weighting filter was used. The preferred value is a 20 kHz (or 22 kHz) measurement bandwidth, and "flat," i.e., no weighting filter.

Conflicting views exist regarding THD+N bandwidth measurements. One argument goes: it makes no sense to measure THD at 20 kHz if your measurement bandwidth doesn't include the harmonics. Valid point, and one supported by the IEC, which says that THD should not be tested any higher than 6 kHz, if measuring five harmonics using a 30 kHz bandwidth, or 10 kHz, if only measuring the first three harmonics. Another argument states that since most people can't even hear the fundamental at 20 kHz, let alone the second harmonic, there is no need to measure anything beyond 20 kHz. Fair enough. However, the case is made that using an 80 kHz bandwidth is crucial, not because of 20 kHz harmonics, but because it reveals other artifacts that can indicate high frequency problems. All true points, but competition being what it is, standardizing on publishing THD+N figures measured flat over 22 kHz seems justified, while still using an 80 kHz bandwidth during the design, development and manufacturing stages.

Correct: THD+N less than 0.01%, +4 dBu, 20-20 kHz, unity gain, 20 kHz BW

Wrong: THD less than 0.01%

IMD -- SMPTE. Intermodulation Distortion -- SMPTE Method

What is tested? A more meaningful test than THD, intermodulation distortion gives a measure of distortion products not harmonically related to the pure signal. This is important since these artifacts make music sound harsh and unpleasant.

Intermodulation distortion testing was first adopted in the U.S. as a practical procedure in the motion picture industry in 1939 by the Society of Motion Picture Engineers (SMPE -- no "T" [television] yet) and made into a standard in 1941.

How is it measured? The test signal is a low frequency (60 Hz) and a non-harmonically related high frequency (7 kHz) tone, summed together in a 4:1 amplitude ratio. (Other frequencies and amplitude ratios are used; for example, DIN favors 250 Hz & 8 kHz.) This signal is applied to the unit, and the output signal is examined for modulation of the upper frequency by the low frequency tone. As with harmonic distortion measurement, this is done with a spectrum analyzer or a dedicated intermodulation distortion analyzer. The modulation components of the upper signal appear as sidebands spaced at multiples of the lower frequency tone. The amplitudes of the sidebands are rms summed and expressed as a percentage of the upper frequency level.

[Noise has little effect on SMPTE measurements because the test uses a low pass filter that sets the measurement bandwidth, thus restricting noise components; therefore there is no need for an "IM+N" test.]

Required Conditions. SMPTE specifies this test use 60 Hz and 7 kHz combined in a 12 dB ratio (4:1) and that the peak value of the signal be stated along with the results. Strictly speaking, all that needs stating is "SMPTE IM" and the peak value used. However, measuring the peak value is difficult. Alternatively, a common method is to set the low frequency tone (60 Hz) for +4 dBu and then mixing the 7 kHz tone at a value of -8 dBu (12 dB less).

Correct: IMD (SMPTE) less than 0.01%, 60Hz/7kHz, 4:1, +4 dBu

Wrong: IMD less than 0.01%

IMD -- ITU-R (CCIF). Intermodulation Distortion -- ITU-R Method

What is tested? This tests for non-harmonic nonlinearities, using two equal amplitude, closely spaced, high frequency tones, and looking for beat frequencies between them. Use of beat frequencies for distortion detection dates back to work first documented in Germany in 1929, but was not considered a standard until 1937, when the CCIF (International Telephonic Consultative Committee) recommend the test. [This test is often mistakenly referred to as the CCIR method (as opposed to the CCIF method). A mistake compounded by the many correct audio references to the CCIR 468 weighting filter.] Ultimately, the CCIF became the radiocommunications sector (ITU-R) of the ITU (International Telecommunications Union), therefore the test is now known as the IMD (ITU-R).

How is it measured? The common test signal is a pair of equal amplitude tones spaced 1 kHz apart. Nonlinearity in the unit causes intermodulation products between the two signals. These are found by subtracting the two tones to find the first location at 1 kHz, then subtracting the second tone from twice the first tone, and then turning around and subtracting the first tone from twice the second, and so on. Usually only the first two or three components are measured, but for the oft-seen case of 19 kHz and 20 kHz, only the 1 kHz component is measured.

Required Conditions. Many variations exist for this test. Therefore, the manufacturer needs to clearly spell out the two frequencies used, and their level. The ratio is understood to be 1:1.

Correct: IMD (ITU-R) less than 0.01%, 19 kHz/20 kHz, 1:1, +4 dBu

Wrong: IMD less than 0.01%

 

 

 

[Vizitator]

La un moment dat te saturi și de lampi! 

[hpavictor]

Pentru amatorii genului , prezint schema  unui amplificator cu performante absolut deosebite :

 

[hpavictor]

https://www.ampbooks.com/mobile/vacuum-tubes/?fbclid=IwAR0vw5VWHSKeH9PkSarPSwqd4e8p424KkM3C9SNf9nkUSpsN5IYjUej-gI8

[hpavictor]

Articol de interes pentru @Vasile :

 

 

https://www.audioxpress.com/article/speaker-design-driver-induced-vibrations?fbclid=IwAR2dGw7J_j4Bp40mVsAV7DrAAsH5h2qg6x--L-1DI3ZpUGX1zSArgUJR6Us

[carageae]

La 30.05.2019 la 9:17, hpavictor a spus:

TDA2030 , TDA2050 LM1875 etc pot fi manarite sa functioneze in clasa A , rezultand un amplificator ieftin si performant pentru casti sau auditii de mica putere .

Atentie , curentul de " repaus " este mare ( 300-400 mA ) si se stabileste din valoarea rezistentelor dintre sursa de minus si iesire  . 

Radiatorul trebuie sa disipe la greu , deci trebuie sa fie mare si eficient  .

 

Mie schema asta imi aminteste de montajele PD1A din Tehnium....sau e chiar pe bune si imi scapa mie ceva? Din ce vad, cu rezistenta totala de 40 de ohmi intre minus si iesire, chiar daca ar functiona cumva, se cam duce bobina difuzorului din motive de CC. Sau chiar echilibreaza cumva rezistenta aia de 30K tensiunea continua la iesire? Sau aia e momeala pt. cei nehotarati?