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    Roy Mottram Custom Headphone Amp is a Blazing Success!

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    Kentley

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    Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by Kentley on Thu Apr 27, 2017 11:43 pm

    About six weeks ago, I asked Roy (Mr. tubes4hifi) about the possibility of a nice headphone amp suitable for use with Sennheiser 650 300 ohm cans. I was not aware that he had already built a one-off all-purpose heavy-duty HA-14, basically IINM a conventional stand-alone powerhouse of an octal-tube HP amp capable of driving anything. Somehow we ended up deciding on a custom-build specifically for my Sennheisers. It is a modified SP-14 Aikido circuit with 6SN7 amp stage and a novel and brilliant 6BL7 current-driver stage to supply a solid 1/2 watt signal for high-impedance HPs such as mine.
    It's built into a modest-sized chassis (10"WX12"DX5"H). No-frills.
    It sounds INCREDIBLE. Never have I heard cans sound so perfect. The fatigue factor has disappeared. It is a true alternative, finally, to firing up the ST-120.
    Roy gave this away practically at cost. And he swears he'll never make another. HOWEVER - he will make a noval version with four 6922s for approx. $700. I suggest that anyone with a set of 250+ ohm cans which may be gathering dust from lack of suitable amplification might consider it.
    It is DEAD quiet, and if I ever turn it up past "noon" I'll require hospitalization.
    N.B. Roy has stated that he would provide a complete kit of the 6922 version (built in the same chassis, I believe) for only $500.
    A nice pair of Sennheisers costs almost that much.


    Last edited by Kentley on Sat Apr 29, 2017 11:23 pm; edited 2 times in total (Reason for editing : correction of unit dimensions)
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    deepee99

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by deepee99 on Fri Apr 28, 2017 12:48 am

    Kentley wrote:About six weeks ago, I asked Roy (Mr. tubes4hifi) about the possibility of a nice headphone amp suitable for use with Sennheiser 650 300 ohm cans. I was not aware that he had already built a one-off all-purpose heavy-duty HA-14, basically IINM a conventional stand-alone powerhouse of an octal-tube HP amp capable of driving anything. Somehow we ended up deciding on a custom-build specifically for my Sennheisers. It is a modified SP-14 Aikido circuit with 6SN7 amp stage and a novel and brilliant 6BL7 current-driver stage to supply a solid 1/2 watt signal for high-impedance HPs such as mine.
    It's built into a modest-sized PH-16 chassis, no-frills.
    It sounds INCREDIBLE. Never have I heard cans sound so perfect. The fatigue factor has disappeared. It is a true alternative, finally, to firing up the ST-120.
    Roy gave this away practically at cost. And he swears he'll never make another. HOWEVER - he will make a noval version with four 6922s for approx. $700. I suggest that anyone with a set of 250+ ohm cans which may be gathering dust from lack of suitable amplification might consider it.
    It is DEAD quiet, and if I ever turn it up past "noon" I'll require hospitalization.
    You already do require some certifiable attention.
    Glad to hear, amigo, and equally happy that Roy came through for you.
    -d-
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    tubes4hifi
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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by tubes4hifi on Sat Apr 29, 2017 10:55 pm

    here's a couple photos for anyone interested, one of the interior before any wiring, the second photo of the finished amp (but before adding the cover for the transformer).


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    deepee99

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by deepee99 on Sun Apr 30, 2017 12:41 am

    Roy, is this a one-off or do you plan to go into production with them?
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    tubes4hifi
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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by tubes4hifi on Sun Apr 30, 2017 5:19 pm

    this was definitely a one-off, as Kentley mentioned, but of course I'm always available to do one-off's of anything people are willing to pay for.
    As Kentley and I mentioned, I would be more than willing to build an HA-12 or supply a kit for that, or do a noval version of the one Kentley has, but using 6922 tubes (let's call that an HA-9).
    Kentley's octal version required two large power transformers and was a real pain to build. The HA-12 would be alot simpler, less expensive, and have more power,
    and work with ANY headphones.
    http://tubes4hifi.com/HA12.htm
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    cci1492

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by cci1492 on Wed May 03, 2017 10:12 am

    Looks like a killer little amp, congrats Kentley and Roy. I see many dacs today with headphone amps, all crap compared to this I'm sure. I wonder how tough would it be to use this little amp with a dac? The digital part of a dac is the part that goes outdated....no? So you swap that part out with newer chips but the amp portion you keep. I'm old school, don't know sh*t about dacs, been looking into them lately and even the ones that cost crazy money to me look like a rip off. They throw a single noval in there and charge $2k for it and people love them.
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    tubes4hifi
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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by tubes4hifi on Wed May 03, 2017 11:22 am

    simple, any line level input (that includes all DACs and CD/DVD players and streaming media) works
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    Kentley

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by Kentley on Wed May 03, 2017 11:45 am

    I'm using this amp with a nice little DAC from the British Rega company. It's da ballz.
    I think cci may have meant could this unit be built with an on-board DAC. Probably not in this configuration. The DAC chip is small, but the switching mechanisms would require a lot of space, and several additional spaces to mount the switches. And the additional inputs. And the power supply.
    The whole point of this customization was to make the simplest "perfect ten" octal HP amp for my Sennheiser 650 cans, and that's what it is.
    cci does raise a good point. Why not make a preamp with a DAC under the same hood, as a lot of companies are doing now?


    Last edited by Kentley on Wed May 03, 2017 9:22 pm; edited 1 time in total
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    cci1492

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by cci1492 on Wed May 03, 2017 3:19 pm

    Ah, I see, switching between a USB input vs. say an optical would complicate things. So an outboard dac with no amp at all would be fine then. Just to bypass any cheap amplifier that they put in those dacs, have the output go directly into this amp.
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    Kentley

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by Kentley on Wed May 03, 2017 3:41 pm

    I'm afraid, to my limited understanding, that it's never that simple. The DAC chip converts digital to analogue, yes, but this signal must be processed somewhere along the chain to a line-level signal of suitable impedance, which is then ready to feed into your amp, whether through a preamp or directly to a power amp. As far as I know, this involves some sort of buffer between the DAC chip and the output of the DAC. Unless you're willing to build your DAC from scratch, you are at the mercy of the manufacturer when it comes to the quality of this stage. But since it's not a gain-stage, decent results are not difficult or expensive. In fact, I'm wary of CD players or DACs with a tube output stage. They're actually more likely to be problematical than not. And as you say they provide an excuse to jack up the price, with no real discernible benefits.
    Perhaps someone with a keener understanding of DACs might wish to chime in to further complicate this issue.
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    Peter W.

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by Peter W. on Wed May 03, 2017 4:41 pm

    Perhaps someone with a keener understanding of DACs might wish to chime in to further complicate this issue.[/quote]

    My "understanding" ain't nohow that "keen", but here goes:

    a) there are but so many manufacturers of the chipsets in DAC devices. Nor are the differences in cost significant once a basic quality threshold has been crossed, and comparing apples to apples.
    b) Anything from a $99 portable DAC to a $megabuck$ outboard DAC uses chipsets from the same sources.
    c) They all perform *exactly* the same job the same way for the same results.
    d) Tubes, whether involved or not in a DAC would be strictly for the analog stages.

    With that in mind, the differences between one-to-the-other is solely and only in the quality of the analog stage. At which the point of diminishing returns is pretty rapidly found and crossed.

    The rest is eyewash.

    Opinion: DACs and their kin are one of the last prevailing opportunities for hucksters, bunco-steer artists, scammers and snake-oil purveyors.

    AKM Semiconductor
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    About cover it.
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    cci1492

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by cci1492 on Wed May 03, 2017 4:48 pm

    So do you guys just use whatever dac is in your CD player? I'm using a cheap Tascam cd-200 (my pioneer dvd player from 1995 died!) and was thinking about an external dac with a tube stage like this headphone amp.
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    corndog71

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by corndog71 on Wed May 03, 2017 5:14 pm

    While it's not tubed you could step into the world of outboard dacs with one of these.

    http://schiit.com/products/modi-2
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    Kentley

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by Kentley on Wed May 03, 2017 5:19 pm

    If all you are using your stand-alone DAC for is decoding CDs, assuming that your CD player is of reasonably modern vintage (say, 2000 or newer) you might enjoy only slight benefit from a DAC, which would bypass the player's DAC chip. I have a Rega Apollo CD player and subsequently purchased the Rega DAC, which contains two Wolfson chips in parallel rather than the one in the player. Different? Debatable. Possibly more jitter-free, possibly better at the margins of audiblity.
    The reason to buy a stand-alone DAC is versatility. You can decode digital signals from your computer through the USB port, hugely improving SQ. You can decode any of a number of modern sources, such as DSD and SACD with the proper unit. I believe Peter W is correct in emphasizing the diminishing returns of a sophisticated DAC if all one wants is "better" CD-quality sound.
    The Wikipedia entry for "DAC" contains a lot of info and references should you care to find out about such matters as "jitter" and "sampling rates" and "digital formats".
    https://en.wikipedia.org/wiki/Digital-to-analog_converter

    And yes. corndog - the Schiit is NOT $hitty. And the Price is Right.
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    cci1492

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    Re: Roy Mottram Custom Headphone Amp is a Blazing Success!

    Post by cci1492 on Wed May 03, 2017 5:28 pm

    Got that Cd player less than 2 years ago, I will read that info. Thanks!

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