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

  1. #21
    Join Date: Aug 2011

    Location: Coventry, England UK

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    I'm Simon.

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    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.
    Go with a series attenuator. Not that there is anything wrong with a shunt but I don't buy their supposed advantage over a series because of 2 issues:

    1. Impedance changes as you rotate through the attenuation range
    2. If any of the contacts fail for whatever reason, the volume will go full (no attenuation) so likely to destroy speakers.

  2. #22
    Join Date: Jun 2018

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    The Slagle AVC has been described to me by a EE, as a attenuator, that works as a filter, that will have a suppression of a full frequency range. I was informed a Slagle could be measured and a simple filter could be produced, allowing the frequency range to be matched to the frequency range of the Slagle.
    This will allow for a lot less wire to be used in the circuitry of the signal path, so technically this will be more in keeping with a minimalistic topology philospophy.
    The Slagle AVC is a Volume Control, and as such a device, is not a traditional Pre-amp by design.
    I suppose a question of interest relating to this thread would be,
    How will a Slagle AVC, compare against a Khozmo, DACT, or ADSA in a DCB1, as a Volume Control.
    I at present have a Slagle AVC with a built in head phone input, and I use as it as my go to Volume Control over the other choices I have.
    I am curious to compare the stand alone Slagle AVC, to other devices, just to see where the division in performance is perceived to be for the better in relation to my tastes.
    As for the comparisons, as a person who does not get out to listen to live music on a regular basis,
    any comparisons I do are not based on how a device produces a reproduction, that in my mind resembles the overall effect of the live performance with a type of Honesty.
    My comparisons are done to assess if a device can create a performance that appears to be a perceived improvement and creates a stimulus to the senses.
    If I were to follow the comparison method that I don't use, the reality 'may be' that I would need to uproot from my system devices that I value and start looking for their replacements
    " That's not going to Happen "

  3. #23
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 9,564
    I'm Oliver.

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    Quote Originally Posted by JohnG View Post
    The Slagle AVC has been described to me by a EE, as a attenuator, that works as a filter, that will have a suppression of a full frequency range. I was informed a Slagle could be measured and a simple filter could be produced, allowing the frequency range to be matched to the frequency range of the Slagle.
    This will allow for a lot less wire to be used in the circuitry of the signal path, so technically this will be more in keeping with a minimalistic topology philospophy.
    The Slagle AVC is a Volume Control, and as such a device, is not a traditional Pre-amp by design.
    I suppose a question of interest relating to this thread would be,
    How will a Slagle AVC, compare against a Khozmo, DACT, or ADSA in a DCB1, as a Volume Control.
    I at present have a Slagle AVC with a built in head phone input, and I use as it as my go to Volume Control over the other choices I have.
    I am curious to compare the stand alone Slagle AVC, to other devices, just to see where the division in performance is perceived to be for the better in relation to my tastes.
    As for the comparisons, as a person who does not get out to listen to live music on a regular basis,
    any comparisons I do are not based on how a device produces a reproduction, that in my mind resembles the overall effect of the live performance with a type of Honesty.
    My comparisons are done to assess if a device can create a performance that appears to be a perceived improvement and creates a stimulus to the senses.
    If I were to follow the comparison method that I don't use, the reality 'may be' that I would need to uproot from my system devices that I value and start looking for their replacements
    " That's not going to Happen "
    Nobody, and I mean nobody, wants a system that replicates live music. That's a PA system and its crap.

    The Slagle was excellent but I prefer what the DCB1 does and to me, it really gives a lot of what I'd expect to find in the studio.

    A bakeoff needs to happen at some point
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Raspberry Pi 3+/Allo Boss 1.2/Isolator 1.3 & Firebottle LPSU with Volumio & JRiver
    Amplification: Nelson Pass Derived DCB1 with Khozmo 48 Step Series Attenuator & Neurochrome Modulus 686 Amplifier
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

    Price List For SPOTFIRE Cables here:https://bit.ly/2Uxiv3j

    Alternative reading: http://www.audioaddictsforum.com

  4. #24
    Join Date: Feb 2010

    Location: Berkshire, UK

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    I'm Tom.

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    Quote Originally Posted by Bigman80 View Post
    Nobody, and I mean nobody, wants a system that replicates live music. That's a PA system and its crap.
    Totally agreed on that.

    Also much preferred my DCB1 to any TVC or passive attenuator I tried, including 5k's worth of Music First Audio TVC.
    Main: Speakers 'RFC' Tannoy Canterburys / custom crossovers with Tannoy ST50 supertweeters; Amp - Silvercore 833C monoblocks; preamp TBA watch this space; Vinyl: Schopper'd Thorens TD124 MkII + Ikeda IT345-CR1 9 inch and Ikeda IT-407 12 inch tonearms; Cartridges Stereo - Miyajima Madake, Miyajima Takumi, Ikeda 9TT, vintage Ortofon SPU GM and SPU Gold; Mono - Miyajimas - Zero 0.7, Premium 1.0, Miyajima/Edison '78' 4.0 conical, and Shure M44 strapped for mono with several Expert Stylus conicals for different eras of 78s; Phono stage Allnic H7000V used with Miyajima ETR-Mono and ETR-Stereo SUTs; Digital: Audio Note CDT2/II transport, heavily enhanced AN DAC based on kit but aspiring to DAC5 spec.

    Study: Speakers - Tannoy DC6; Amp: Marantz PM-4; Digital: CDP Sony CDP-X3000ES & Arcam rBlink; Vinyl: Garrard 401 with AT 1503 MkI broadcast arm, Ortofon SPU Classic GM, Ortofon 2-15k SUT and Puresound Tenuto platter mat

  5. #25
    Join Date: Nov 2015

    Location: Wolverhampton

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    I'm Oliver.

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    Quote Originally Posted by montesquieu View Post
    Totally agreed on that.

    Also much preferred my DCB1 to any TVC or passive attenuator I tried, including 5k's worth of Music First Audio TVC.
    And agreed on that!
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Raspberry Pi 3+/Allo Boss 1.2/Isolator 1.3 & Firebottle LPSU with Volumio & JRiver
    Amplification: Nelson Pass Derived DCB1 with Khozmo 48 Step Series Attenuator & Neurochrome Modulus 686 Amplifier
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

    Price List For SPOTFIRE Cables here:https://bit.ly/2Uxiv3j

    Alternative reading: http://www.audioaddictsforum.com

  6. #26
    Join Date: Jan 2013

    Location: Birmingham

    Posts: 4,837
    I'm James.

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    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.

    Attachment 24845

    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).

    Attachment 24846
    Attachment 24847

    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.

    Attachment 24843

    Attachment 24844

    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.
    Certainly agree with NOS valves in the Croft but like all things one needs to tread carefully to see what gains can be had. Some NOS tubes sound better than others and some sound better in different positions in the Croft if you have a regulated version.

    I will be interested to hear your comments when you have done some further experimentation with attenuators, obviously Glenn uses dual mono to get around some of the inherent problems of single attenuators. I know of a few folk who have changed the carbon volume pots on Croft preamps only to loose some of the organic sound and have decided to stay with the Tocos pots.

    During the 80,s and 90,s Glenn built all sorts of exotic amps with many exotic parts but nothing beats good design and I feel only marginal gains are to be had from foo items, where as simple well designed circuitry is the key. The sheer transparency and live realistic sound you mentioned with great body is exactly what I have with my set up. I know more can be had if I moved to separate power supplies and a separate phono stage and probably mono blocks as you have found yourself. Changing a couple of volume pots in my humble opinion only gives subtle benefits and i would be very cautious to loose the sound I have currently.

    But I applaud your endeavours to improve your Croft and look forward to your results.
    VPI Scout 1.1 - Ortofon 2M Black FGS - Croft 25R+ - Croft Series 7 - Spendor SP2

  7. #27
    Join Date: Jan 2013

    Location: Bristol

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    Quote Originally Posted by Bigman80 View Post
    Nobody, and I mean nobody, wants a system that replicates live music. That's a PA system and its crap.
    Some modern PA systems are absolutely astonishing.

    Massive Attack on the Bristol Downs 3 years ago was mind blowingly good. An outdoor venue, the bass was beyond anything I have encountered anywhere. The scale was immense, and what's more, it didn't fail when assessing it with these hi-fi ears. It WAS hi-fi quality.

    Likewise, Orbital at the Bristol Downs this year was incredible sonically, too.

    First comment from wife as we got near the stage "that's better than your hi-fi". Too f^&*ing right it was. And way better than anything I heard at Munich this year.

    So apart from the fact that huge PA systems aren't practical domestically, don't assert they are crap. They are astonishing in the 'best of" cases. Really.
    "Trans like shhtate. Trans like shhtate. Do you know what doctors call that shhstate? Love." Electric Boogaloo - Isaac Chambers.

  8. #28
    Join Date: Nov 2015

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    I'm Oliver.

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    Quote Originally Posted by User211 View Post
    Some modern PA systems are absolutely astonishing.

    Massive Attack on the Bristol Downs 3 years ago was mind blowingly good. An outdoor venue, the bass was beyond anything I have encountered anywhere. The scale was immense, and what's more, it didn't fail when assessing it with these hi-fi ears. It WAS hi-fi quality.

    Likewise, Orbital at the Bristol Downs this year was incredible sonically, too.

    First comment from wife as we got near the stage "that's better than your hi-fi". Too f^&*ing right it was. And way better than anything I heard at Munich this year.

    So apart from the fact that huge PA systems aren't practical domestically, don't assert they are crap. They are astonishing in the 'best of" cases. Really.
    No, I assert that they are crap, in a domestic setting.
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Raspberry Pi 3+/Allo Boss 1.2/Isolator 1.3 & Firebottle LPSU with Volumio & JRiver
    Amplification: Nelson Pass Derived DCB1 with Khozmo 48 Step Series Attenuator & Neurochrome Modulus 686 Amplifier
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

    Price List For SPOTFIRE Cables here:https://bit.ly/2Uxiv3j

    Alternative reading: http://www.audioaddictsforum.com

  9. #29
    Join Date: Jan 2013

    Location: Bristol

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    Quote Originally Posted by Bigman80 View Post
    No, I assert that they are crap, in a domestic setting.
    The systems I mentioned are impossible in a domestic setting.

    I know where you are coming from. But the best of them are absolutely amazing, and do things no domestic hi-fi system could ever hope to achieve.
    "Trans like shhtate. Trans like shhtate. Do you know what doctors call that shhstate? Love." Electric Boogaloo - Isaac Chambers.

  10. #30
    Join Date: Nov 2015

    Location: Wolverhampton

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    I'm Oliver.

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    Quote Originally Posted by User211 View Post
    The systems I mentioned are impossible in a domestic setting.

    I know where you are coming from. But the best of them are absolutely amazing, and do things no domestic hi-fi system could ever hope to achieve.
    No, I agree with the idea that the best PA systems do things nothing else can but personally, if I put of an album recorded at Abbey road for instance, I want the system to portray that. I want to hear the mix and the layering, the doubly tracking etc. I don't want it to sound "live" because it wasn't.

    I want it to sound real.
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Raspberry Pi 3+/Allo Boss 1.2/Isolator 1.3 & Firebottle LPSU with Volumio & JRiver
    Amplification: Nelson Pass Derived DCB1 with Khozmo 48 Step Series Attenuator & Neurochrome Modulus 686 Amplifier
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

    Price List For SPOTFIRE Cables here:https://bit.ly/2Uxiv3j

    Alternative reading: http://www.audioaddictsforum.com

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