Location: East Riding of Yorkshire these days
Posts: 4,779
I'm Shaun.
Greetings,
The pair of transistors for the I/U conversion stage are actually bipolar NPN type. The NPN type of transistor has a similar structure to a triode valve (anode=collector, grid=base and cathode=emitter) except having no filament and using a solid state semiconductor material such as Germanium or Silicon instead of vacuum. Their bias is only a couple of mA, while the current ability of the transistors and the discrete shunt power supply easily approaches or exceeds 1A.
Since all the NPN bipolar transistors have 3 pins one can easily replace them in a matter of seconds by installing 3 sockets on the PCB of the DAC. That provides the possibility to voice any NPN transistor in a given circuit and to customise the sound to its own liking.
S
SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
www.SW1XAD.co.uk
Location: London/Durham
Posts: 6,882
I'm Lawrence.
Sounds simple, why do I have the feeling someone will respond to say it's not quite that easy...
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SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
www.SW1XAD.co.uk
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
While it's true that many transistors have enough in common to be interchangeable and in many circuits feedback will iron out any differences, this does smack of a "suck it and see" approach or a hit-and-miss or trial-and-error approach.
Besides, transistors are entirely the wrong shape to be good for rolling - at least valves are cylindrical
It may be true in many circuits, however we do not employ any kind of feedback loop(s) in our circuits. It also applies to the pair of NPN transistors in the I/U conversion stage.
I must admit that it is a trial and error approach, though. That is also a part of R & D, which is costly & time consuming but can sometimes be very rewarding. I would recommend to try it sometimes.
SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
www.SW1XAD.co.uk
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
Location: London/Durham
Posts: 6,882
I'm Lawrence.
I know op amp rolling is very popular in headphone amps (although that doesn't mean it's a good idea). Is there any reason transistors wouldn't work the same? I think this is a technical discussion worth pursuing.
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Absolutely, the only but very significant difference is that we do not use op-amps as those integrated circuits are very complex in nature, containing dozens of transistors, resistors, diodes and negative feedback loops- all of which is responsible for degradation of sound beyond belief. There is a huge difference (like night and day) between a couple of op-amps containing around 20-40 transistors each and a pair of specially selected, quality transistors for the I/U followed by a powerful, low internal resistance triode running in single ended class A without any negative feedback loop.
http://sw1xad.co.uk/technology_post/...-question-faq/
One could also replace the I/U transistor with a carefully selected resistor and live with just one triode instead but then one would loose out on additional resolution and dynamics.
If that is desired then we offer that kind of solution too.
S
SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
www.SW1XAD.co.uk