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Thread: Switched attenuators, what's all the fuss about?

  1. #11
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 7,121
    I'm Oliver.

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    Ok maybe 300
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: NONE
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

  2. #12
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 990
    I'm Chris.

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    Glad you are finding differences with different methods of attenuation

    The history of varying a signal using resistance, which has similarity but is not quite the same as switched attenuation
    goes back nearly 100 years to a patent for the rheostat, that was intended for a musical light display instrument "The Sarabet " https://en.wikipedia.org/wiki/Mary_Hallock-Greenewalt
    used with a type of Visual music she called - Nourathar

    It is interesting to note that varying audio signals, this way via a rheostat, was never intended at all.

    In your journey discovering different methods of attenuation, keep in mind there are many alternatives, such as using contact-less opto- coupling methods.
    Last edited by Light Dependant Resistor; 07-12-2018 at 09:47.

  3. #13
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,801
    I'm Simon.

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    Alan which of the Khozmo's did you try? I think there's at least as much variation between them as there is with other brands. My own personal favourite switched attenuator is the Goldpoint V47, they just didn't do a reasonably priced RC version so I settled on the 10k rotary encoded Khozmo.
    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

  4. #14
    Join Date: May 2015

    Location: Greece

    Posts: 193
    I'm Panos.

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    Hoping that I am not hi-jacking this thread, I would like to contribute my experience with stepped attenuators, if I may.
    There has been a lot of debate among fellow audiophiles about the comparison of passive and active preamps. Each side had certain advantages to propose. I have a top-of-the-line Croft preamp, the Micro 25RSLS (line only), upgraded by Glenn.

    IMG_3115.jpg

    But I took the plunge and purchased a passive Hattor dual-mono preamp (the higher-end brand that Arek Kallas, the owner of Khozmo, has on offer).

    4.jpg
    3.jpg

    My Hattor passive preamp uses Khozmo shunt attenuators with z-foil resistors. In comparison to the Croft preamp, the Hattor was more transparent, more detailed, but simultaneously somewhat "thinner" and smaller in body. The passive preamp sounded more neutral, more precise, whereby the Croft sounded more alive, with greater body and more realistic. I could not say that the one was better than the other one on all points. I liked several qualities in both preamps.

    And then it dawned at me. What if I could combine the best of each preamp?

    So, I decided to make a small experiment. More specifically I decided to bypass the low-cost pots of the Croft (Tocos) and use the Hattor as a volume control upstream the Croft. In other words, I connected all sources (phono stage and DAC) to the Hattor and then I connected the Hattor output to one of the Croft's inputs. Interconnect cables for that connection were Mark Grant HDX1. All other interconnects were Belden 8428.

    Croft_potentiometer_bypass copy.jpg

    IMG_3731.jpg

    The result? REALLY, really interesting! The combined preamps gave me both the transparency, detail, body and dynamics. The realism of the sound was upgraded. And all that, taking into account that there were additional circuits, binding posts and an extra set of interconnects than before.

    After this introduction, I am now seriously thinking of having two Khozmo attenuators with z-foil resistors (similar to the ones in the Hattor preamp) installed inside the Croft preamp. This will allow me to achieve a shorter signal path than what I currently have with my chained preamps. Hopefully a remote control will fit inside the Croft box as well.

    I understand that other fellow members have tried Khozmo attenuators, and there seems to be a consensus that series attenuators are better than shunt. I have not had the chance to make such a comparison, but I've liked the shunt attenuators of the Hattor (having followed Arek's recommendation).

    I know that commercial (vs. DIY) hi-fi gear is built to a price point, and I have the utmost respect to Croft gear. However, in my humble opinion, I believe that Croft's designs would perform significantly better with upgraded valves (NOS instead of new stock) and switched attenuators (than carbon pots). I hope my comments are not misunderstood, I am just speaking from personal experience.
    System1: Roksan Xerxes original (HiFi Inspire plinth) with OriginLive DC motor + Audiomods Series5 + Denon DL-103R Namiki retipped, Music Maker III, ASR Mini Basis Exclusive, Marantz CD6005, LAB12 DAC1 SE+, Hattor BIG, Croft Micro25RSLS + Series7R monoblocks (110W/ea), Harbeth SHL5 Plus 40th Anniv., KEF LS50, LAB12 Gordian, Belden 8428, Black Cat Red Level Triode, LAB12 Knack MkII

    System 2: Marantz CD6003, Croft SuperMicroII ('R' spec by Croft, Tesla E83CC in phono)+ Series7, Snell Type EII (with bypass caps, new internal wiring, WBT nextgen 0703Cu), Mark Grant HDX1, Atlas Hyper 3.0

  5. #15
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 7,121
    I'm Oliver.

    Default

    Quote Originally Posted by pankon View Post
    Hoping that I am not hi-jacking this thread, I would like to contribute my experience with stepped attenuators, if I may.
    There has been a lot of debate among fellow audiophiles about the comparison of passive and active preamps. Each side had certain advantages to propose. I have a top-of-the-line Croft preamp, the Micro 25RSLS (line only), upgraded by Glenn.

    IMG_3115.jpg

    But I took the plunge and purchased a passive Hattor dual-mono preamp (the higher-end brand that Arek Kallas, the owner of Khozmo, has on offer).

    4.jpg
    3.jpg

    My Hattor passive preamp uses Khozmo shunt attenuators with z-foil resistors. In comparison to the Croft preamp, the Hattor was more transparent, more detailed, but simultaneously somewhat "thinner" and smaller in body. The passive preamp sounded more neutral, more precise, whereby the Croft sounded more alive, with greater body and more realistic. I could not say that the one was better than the other one on all points. I liked several qualities in both preamps.

    And then it dawned at me. What if I could combine the best of each preamp?

    So, I decided to make a small experiment. More specifically I decided to bypass the low-cost pots of the Croft (Tocos) and use the Hattor as a volume control upstream the Croft. In other words, I connected all sources (phono stage and DAC) to the Hattor and then I connected the Hattor output to one of the Croft's inputs. Interconnect cables for that connection were Mark Grant HDX1. All other interconnects were Belden 8428.

    Croft_potentiometer_bypass copy.jpg

    IMG_3731.jpg

    The result? REALLY, really interesting! The combined preamps gave me both the transparency, detail, body and dynamics. The realism of the sound was upgraded. And all that, taking into account that there were additional circuits, binding posts and an extra set of interconnects than before.

    After this introduction, I am now seriously thinking of having two Khozmo attenuators with z-foil resistors (similar to the ones in the Hattor preamp) installed inside the Croft preamp. This will allow me to achieve a shorter signal path than what I currently have with my chained preamps. Hopefully a remote control will fit inside the Croft box as well.

    I understand that other fellow members have tried Khozmo attenuators, and there seems to be a consensus that series attenuators are better than shunt. I have not had the chance to make such a comparison, but I've liked the shunt attenuators of the Hattor (having followed Arek's recommendation).

    I know that commercial (vs. DIY) hi-fi gear is built to a price point, and I have the utmost respect to Croft gear. However, in my humble opinion, I believe that Croft's designs would perform significantly better with upgraded valves (NOS instead of new stock) and switched attenuators (than carbon pots). I hope my comments are not misunderstood, I am just speaking from personal experience.
    Panos,

    You are the man!!

    I have been saying the same thing to Croft owners & Firebottle KIN owner, Alan, for the last 12 months are least.

    The TOCOS pots in the Croft is an adequate pot and one I prefer to the Alps blue but there is so much more available from the preamp than either pot allows.

    The Khozmo is an absolute beauty. I have the series stepped attenuator and I love it. It's my second one.

    There was a bakeoff today between the Firebottle KIN fitted with an Acoustic Dimensions SA and my new DCB1 with Khozmo.

    There was certainly enough quality in the FIREBOTTLE KIN that was being strangled by the Alps pot. Now, it's a thing of beauty all thanks to the upgrade to the ADSA.

    Get the better attenuator fitted and enjoy the croft. Good work sir!
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: NONE
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

  6. #16
    Join Date: May 2015

    Location: Greece

    Posts: 193
    I'm Panos.

    Default

    Indeed, Oliver, this is what I am going to do. I'll have Khozmo attenuators fitted into the Croft. I hope (and expect) that the final result will be even better than my current overkill preamp combination. But that recent experiment has been quite enlightening.

    Now the question is whether I should go for shunt or series attenuators. Arek favors shunt...

    I understand that Josie has significant experience with Khozmo attenuators in her Croft preamp for several years now.
    System1: Roksan Xerxes original (HiFi Inspire plinth) with OriginLive DC motor + Audiomods Series5 + Denon DL-103R Namiki retipped, Music Maker III, ASR Mini Basis Exclusive, Marantz CD6005, LAB12 DAC1 SE+, Hattor BIG, Croft Micro25RSLS + Series7R monoblocks (110W/ea), Harbeth SHL5 Plus 40th Anniv., KEF LS50, LAB12 Gordian, Belden 8428, Black Cat Red Level Triode, LAB12 Knack MkII

    System 2: Marantz CD6003, Croft SuperMicroII ('R' spec by Croft, Tesla E83CC in phono)+ Series7, Snell Type EII (with bypass caps, new internal wiring, WBT nextgen 0703Cu), Mark Grant HDX1, Atlas Hyper 3.0

  7. #17
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 7,121
    I'm Oliver.

    Default

    Quote Originally Posted by pankon View Post
    Indeed, Oliver, this is what I am going to do. I'll have Khozmo attenuators fitted into the Croft. I hope (and expect) that the final result will be even better than my current overkill preamp combination. But that recent experiment has been quite enlightening.

    Now the question is whether I should go for shunt or series attenuators. Arek favors shunt...

    I understand that Josie has significant experience with Khozmo attenuators in her Croft preamp for several years now.
    I don't think Josie is alone in that experience either.

    I asked for advise on whether to go shunt, ladder or series and the concencious was for series. No idea why but when electrical engineers are saying it, I listen.

    I've heard a hattor, it was decent but suffered the same traits all passives do. I prefer active/unity gain.

    Good luck with the mods to the croft, I'll look forward to the pics
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: NONE
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

  8. #18
    Join Date: Jan 2013

    Location: Bristol

    Posts: 4,431
    I'm Justin.

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    Anyone heard the Hattor active tube stage with the Hattie passive?

    What's nice is the ability to switch it out easily, so you can listen in active or passive modes depending on mood.

    It is about twice the price of the passive unfortunately.
    "I travelled far and wide through prisons of the cross. What did you see there? The power and glory of sin. What did you see there? The blood of Christ on their skins."

  9. #19
    Join Date: Nov 2008

    Location: belgrade serbia

    Posts: 703
    I'm gordan.

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    A bare Slagle AVC was $200. Don't tell me any RVC kills it?

    What is KIN? Any links?
    Gordan.
    Speakers: Oris Swing MkII
    Amps: Thomas Mayer 300b/ Hiraga La Maison de L'Audiophile 20
    Preamp: Silver AVC by eng. Ferenc Lazar
    Phono Preamp: Shishido LCR by Solaja Audio
    Deck: Garrard 301 Martin Bastin reworked/plinthed with Fidelity Research FR64fx
    Cartridges: SPU Spirit/ Koetsu Black revisited by eng. Salai/ Miyajima Shilabe
    Step Up Transformers: Tango MCT 999/ Ortofon T-5000/ Lumiere SUT
    Digital: Shigaclone by eng. Ferenc Lazar with Lampizator Amber II
    Wires: of sufficient length

  10. #20
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 7,121
    I'm Oliver.

    Default

    Quote Originally Posted by anubisgrau View Post
    A bare Slagle AVC was $200. Don't tell me any RVC kills it?

    What is KIN? Any links?
    Firebottle KIN - Valve preamp, with or without phonostage. Made by Firebottle of this forum.

    RVC - Relay volume control, cheap as chips Chinese passive preamp. Exceptional sound for 100 but not perfect.
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: NONE
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

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