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Thread: Meticulous detail

  1. #21
    Join Date: Oct 2012

    Location: NE England

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    I'm Jez.

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    Quote Originally Posted by Lawrence001 View Post
    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.

    Sent from my NEM-L51 using Tapatalk
    No you can't do it with transistors in the same way as op amps.
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

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  2. #22
    Join Date: Apr 2016

    Location: Essex

    Posts: 127
    I'm Slawa.

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    Quote Originally Posted by Arkless Electronics View Post
    No you can't do it with transistors in the same way as op amps.
    Why not?

    Check this http://sw1xad.co.uk/transistor-rolli...ersion-option/

    Rolling transistors is almost as easy as rolling valves or op-amps or any components that have pins and could be installed on sockets.

    As with any component that has pins it is paramount to make sure that it is pin compatible and to observe the correct orientation.

    S
    Last edited by SW1X; 17-09-2017 at 16:46.
    SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
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  3. #23
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    Quote Originally Posted by SW1X View Post
    Why not?

    http://sw1xad.co.uk/transistor-rolli...ersion-option/

    Rolling transistors is almost as easy as rolling valves or op-amps or any components that have pins and could be installed on sockets.

    As with any component that has pins it is paramount to make sure it is pin compatible and to observe the correct orientation.

    S
    Because they come in NPN and PNP, germanium has a Vbe of 0.2V but silicon 0.7 (roughly), they have different voltage ratings, max current, power ratings, Hfe, Ft, internal capacitances etc. A silicon transistor will not work in a circuit designed for germanium and vice versa (other than certain types of emitter follower). The different Ft and capacitances may cause oscillation, either locally, or in the case of a feedback amplifier the compensation will usually need changing to avoid oscillation or gain peaking. In zero feedback amps the Hfe and Vbe become pretty critical and transistor matching is often required.... Some are rated as low noise, some for switching duty, some for RF uses and which may have a max voltage rating of only 12V. With fet's it's even worse as the range of Idss and pinch off voltage is huge even among devices of the same type and they often need selecting for Idss or to have a select-on-test resistor in the biasing...

    If a circuit is pretty non critical in most ways, and has robust biasing, then a range of similarly rated transistors will work yes. eg in the line stages of something like a Quad 303 virtually any transistor that fits in the "small signal, >30V, >60MHz Ft, >50mA, >100Hfe" and of the correct polarity will work, but may well not be optimum. In many much more critical applications, changing a transistor that has been carefully chosen for its specific characteristics in that circuit will often result in the amp blowing up, and maybe taking out the speakers if it goes DC!
    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
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  4. #24
    Join Date: Apr 2016

    Location: Essex

    Posts: 127
    I'm Slawa.

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    Quote Originally Posted by Arkless Electronics View Post

    If a circuit is pretty non critical in most ways, and has robust biasing, then a range of similarly rated transistors will work yes. eg in the line stages of something like a Quad 303 virtually any transistor that fits in the "small signal, >30V, >60MHz Ft, >50mA, >100Hfe" and of the correct polarity will work, but may well not be optimum. In many much more critical applications, changing a transistor that has been carefully chosen for its specific characteristics in that circuit will often result in the amp blowing up, and maybe taking out the speakers if it goes DC!
    We are talking I/U (current to voltage conversion) stage here not driver or output stages. There are no heavy loads at the R2R DAC current output! As a matter of fact the DAC itself would love to see a short circuit here.
    We are dealing with a couple of mA currents at I/U conversion stage, which are very critical to the sound.
    Nothing can really blow here as we are really dealing with tiny currents and small voltages <10V.

    Even mixing up pins is not going to do any damage- happened to me a couple of times without any damage neither to the transistor nor to the I/U power supply.

    I would not recommend to try any transistor that is a different breed other than bi-polar NPN, though e.g. PNP instead of NPN.
    SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
    www.SW1XAD.co.uk

  5. #25
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    Quote Originally Posted by SW1X View Post
    We are talking I/U (current to voltage conversion) stage here not driver or output stages. There are no heavy loads at the R2R DAC current output! As a matter of fact the DAC itself would love to see a short circuit here.
    We are dealing with a couple of mA currents at I/U conversion stage, which are very critical to the sound.
    Nothing can really blow here as we are really dealing with tiny currents and small voltages <10V.

    Even mixing up pins is not going to do any damage- happened to me a couple of times without any damage neither to the transistor nor to the I/U power supply.

    I would not recommend to try any transistor that is a different breed other than bi-polar NPN, though e.g. PNP instead of NPN.
    I was mainly wanting to point out to people that in general it is a very bad idea to attempt "transistor rolling" and at worst could release the magic smoke!! I'm sure you know what you are doing in the context of your own products
    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

  6. #26
    Join Date: Apr 2016

    Location: Essex

    Posts: 127
    I'm Slawa.

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    Chris just posted his impression on the DAC I Signature with the newly rolled I/U transistors. I installed 2 x 3 sockets and inserted his favorite sounding transistor which he determined by himself.

    http://theartofsound.net/forum/showt...duction-Update

    S
    SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
    www.SW1XAD.co.uk

  7. #27
    Join Date: Apr 2016

    Location: Essex

    Posts: 127
    I'm Slawa.

    Default SW1X DAC I Review updated

    Greetings,

    The review of SW1X DAC I STD Active I/V just got updated. One can read about the results of rolling different transistors in the I/U conversion stage. The updated review can be accessed here:

    http://www.hifi-advice.com/blog/revi...ws/sw1x-dac-1/

    S
    SW1X Audio DesignTM ... Finest Audio Components ... Designed and Handcrafted in England
    www.SW1XAD.co.uk

  8. #28
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 1,250
    I'm Chris.

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    Glad to see Slawa's ideas gaining traction. I believe he now offers this as a customer option on some of his DACs..

    Like the appetite for tube rolling, this now gives enthusiasts yet another option to customise the sound to their liking. Differences easily match the scale of those achieved by tube rolling.

  9. #29
    Join Date: May 2014

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    I'm Martin.

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    Quote Originally Posted by Macca View Post
    How did Germanium score?
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    As usual, they beat England on penalties!

    Sorry, as you were.

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