STUDER A68 power amplifier (REVOX A740 shared circuit)
It was introduced in 40 years ago about 1977. It according to the Recording Industry standard, the distortion is less than 0.1% .
I start simulate A68 in TINA-TI, and feel the schematic looked a bit familiar . Then I find the Voltage-Amplification-Stage (VAS) is almost same with the darTZeel NHB-108 internet uncovered schematic, there are 12 resistors value all fully equal and the all 4 pairs of transistor structure are exactly the same, only the feedback networks are different.
If the uncovered schematic is right, is the darTZEEL NHB-108 reprint STUDER A68 VAS or someone designed the structure earlier?
fig.1 STUDER A68 service manual schematic
fig.2 STUDER A68 simulate
fig.3 darTZeel NHB-108 internet unofficial uncoverd schematic
It was introduced in 40 years ago about 1977. It according to the Recording Industry standard, the distortion is less than 0.1% .
I start simulate A68 in TINA-TI, and feel the schematic looked a bit familiar . Then I find the Voltage-Amplification-Stage (VAS) is almost same with the darTZeel NHB-108 internet uncovered schematic, there are 12 resistors value all fully equal and the all 4 pairs of transistor structure are exactly the same, only the feedback networks are different.
If the uncovered schematic is right, is the darTZEEL NHB-108 reprint STUDER A68 VAS or someone designed the structure earlier?
fig.1 STUDER A68 service manual schematic
fig.2 STUDER A68 simulate
fig.3 darTZeel NHB-108 internet unofficial uncoverd schematic
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This is such an amusing catch. Well done!
Mr Delétraz combined this with a diamond output, added two mysterious diodes and got himself a patent and full bragging rights
Rumours are he gave up on the diamond with the patented diodes in his later amps, so i guess he now produces exact Studer clones.
Mr Delétraz combined this with a diamond output, added two mysterious diodes and got himself a patent and full bragging rights
Rumours are he gave up on the diamond with the patented diodes in his later amps, so i guess he now produces exact Studer clones.
Well, did anybody compared a clone to the real thing to confirm that what Chinese claim is
a proper schematic of a Dartzeel amp is actually true? Seem's like a lot of Chinese copy cats are producing this amp . Did all of them buy the amp to make a clone? It sounds unlikely. All those Ebay's Kondo or Jadis amps performing "80%" like originals ....
a proper schematic of a Dartzeel amp is actually true? Seem's like a lot of Chinese copy cats are producing this amp . Did all of them buy the amp to make a clone? It sounds unlikely. All those Ebay's Kondo or Jadis amps performing "80%" like originals ....
Ha ha , chief of Goldmund used the phrase "sounds like an old Studer" in derogatory comment relating to a fashionable at that time NOS dacs
I wouldn't call it a clone when the "original" differs in a number of crucial details, most importantly its application of feedback.
One would hope that the clones do not replicate the original too closely in some respects, as those apparently had their quirks, as Stereophile found out. Its measurements are rather non-terrible - at least with 8-ohm loads - considering its lack of negative feedback across the output stage, thanks no doubt to the good inherent linearity of the diamond buffer and a decent amount of bias current.
I would not be surprised if the Studer design could be made to perform quite well with some faster output devices and higher bias current.
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