Principle behind a tube buffer

Tomasito
Tomasito Posts: 142
edited February 2011 in DIY, Mods & Tweaks
Hello,
I am not sure if this the forum to post this inquiry, let me know if it is not.

I read and heard a lot of good feedback/results of putting a tube buffer.
Can anybody explain to me what is the principle behind a tube buffer?
Post edited by Tomasito on
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  • mhardy6647
    mhardy6647 Posts: 33,909
    edited April 2010
    Typically they are (I presume) cathode folllowers and essentially they are impedance matching devices.
    I love vacuum tubes for audio, but unless you have an impedance mismatch between, e.g., a source and a preamp, or a preamp and power amp, they should do nothing at all (i.e., they should be unity-gain devices and have minimal impact on the signal other than to "buffer" against impedance mismatches).

    http://www.glass-ware.com/tubecircuits/Easy_Cathode_Followers.html
    http://www.freewebs.com/valvewizard/accf.html
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  • FTGV
    FTGV Posts: 3,649
    edited April 2010
    mhardy6647 wrote: »
    ... unless you have an impedance mismatch between, e.g., a source and a preamp, or a preamp and power amp, they should do nothing at all...
    Except perhaps add abit of even order harmonic distortion and raise the noise floor.
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  • mhardy6647
    mhardy6647 Posts: 33,909
    edited April 2010
    Note that I stopped short of saying that :-)
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  • ShinAce
    ShinAce Posts: 1,194
    edited April 2010
    mhardy6647 wrote: »
    Note that I stopped short of saying that :-)

    But the even order harmonics are the end goal!
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  • mhardy6647
    mhardy6647 Posts: 33,909
    edited April 2010
    ShinAce wrote: »
    But the even order harmonics are the end goal!

    Of the tube buffers? Quite possibly.
    Of "tube magic"? Not so much.
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  • hearingimpared
    hearingimpared Posts: 21,137
    edited April 2010
    I used a Musical Fidelity X10 v3.x tube buffer between my Denon 2900 that I use for SACD and my tube preamp. It did add more of the tubey sound to the music but 1) I found it to be overkill, i.e. too warm because the preamp is tubed 2) I had to increase the volume of when playing SACD to get to the volume level I like to listen to perhaps due to MH's theory on impedence mismatch. However, if you have a completely solid state rig it really does add that tubey sound with lush, warm, non-fatiging music.

    I would recommend trying one between your digital front end and your preamp as that is where you will hear the biggest difference and improvement.

    Funny thing, my CDP uses class A tube output and I don't get the problem of overkill that I got with the tube buffer.
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  • ESavinon
    ESavinon Posts: 3,066
    edited April 2010
    Joe, did you get your x10 modded?
    SRT For Life; SDA Forever!

    The SRT SEISMIC System:
    Four main satellite speakers, six powered subs, two dedicated for LFE channel, two center speakers for over/under screen placement and three Control Centers. Amaze your friends, terrorize your neighbors, seize the audio bragging rights for your state. Go ahead, buy it; you only go around once.
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  • zingo
    zingo Posts: 11,258
    edited April 2010
    Tomasito wrote: »
    Can anybody explain to me what is the principle behind a tube buffer?

    Since tubes amplify an electrical signal in a little different way than chips, the sound comes out a little different. A tube buffer would be the easiest way to insert the tube signature sound into an all SS rig.

    Theoretically, a tube buffer should only benefit you if you do not have tubes in your system. But, apparently the exception to this might by the tubed CDP? It's a interesting little device that I've heard work in some systems, but it will most likely be a trial and error type thing.
    Jake
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  • heiney9
    heiney9 Posts: 25,197
    edited April 2010
    My main preamp is an Adcom GFP-750 which is SS and can run in passive mode as well as active mode. It's a damn fine sounding, dead neutral piece of gear. I have a Dared SL2000A tube preamp (not buffer). For convenience I run the Dared through the HT bypass/processor loop on the Adcom. I can then use the remote to switch the Dared in and out.

    In the beginning I did this so I could compare the two units. The Adcom has gotten accolades since it's introduction so I figured it would be a good benchmark. Now that I have compared the two it's a matter of preference and convenience. I can listen to music or a movie w/o having to always turn on tubes. But, when I want to sit and have a serious, intimate listening session I can use the Dared w/o having to unhook, rearrange, etc.....etc.

    Overall I prefer the tubes just slightly when I'm having a serious "audiophile" session. The tubes add a bit of dimensionality to all recordings and seem to add depth and width to recordings. Bass notes, especially mid-bass becomes a little more emphasized, midrange seems to become a little thicker and more lively (good stuff!!!) and highs seem to "shimmer" and decay better.

    Of course it depends on the tubes and rectifier. If I level match the two units it does take some listening to hear the differences, but they are there and the tubes win for musicality everytime.

    12AT7 tubes I use on a regular basis are:

    1962 Amperex "Bugle Boy" made in France- Nice extended highs, lush, but not overdone midrange, slightly fat lower midbass. A nice fairly balanced tube

    1959 Valvo Hamburg. Similar to the above, great decay and very precise on the highs. Neutral midrange and tight bass and nice 3D soundstage

    1965 Valvo 6201 Gold Pin- Same as above only even more neutral with great 3D presentation.

    1967 Telefunken ECC801S 3 Mica- Superb tubes, lively, punchy, very quiet and very neutral this tube has the best attributes of transistors and then the charm and "Soul" of tubes. My favorite.

    1958 GE 6201 5 Star series w/ 3 Mica. Huge soundstage, simply huge!!!! Slightly plump bass, detailed highs, liquid midrange. A favorite for sure but on some recordings along with the SDA's it can be a bit much as the soundstage can sound unnatural at times.

    I use a 1945 5Z4G (CV1863) STC Brimar rectifier. A superb sounding rectifier that has great synergy with the above tubes. 2nd favorite is a 1954 5V4G w/Black inline plates and double D bottom getters.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
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  • hearingimpared
    hearingimpared Posts: 21,137
    edited April 2010
    ESavinon wrote: »
    Joe, did you get your x10 modded?

    No I didn't Ed but I sold it to Greg (inspiredsports) and he gave it the complete mod and wall wort treatment. IIRC he even sent it to England to get the work done but don't hold me to that. I believe Ted uses the MFs.
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  • FTGV
    FTGV Posts: 3,649
    edited April 2010
    ShinAce wrote: »
    But the even order harmonics are the end goal!

    Distortion is distortion albeit the even order variety is considered to be more pleasing to the ear.
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  • Tomasito
    Tomasito Posts: 142
    edited April 2010
    I got alot of info to digest....bottomline the tube buffer is to give a tubey sound to a SS rig... Thank you guys
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  • zingo
    zingo Posts: 11,258
    edited January 2011
    I'm bumping this thread as I'm looking for a balanced in/out tube buffer kit to use in a DIY amp; can you say integrated, hybrid class D. :biggrin: Has anyone ever seen any such product or kit?
    Jake
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  • Face
    Face Posts: 14,340
    edited January 2011
    This is the only one I'm aware of. http://www.space-tech-lab.com/SP-BUF-103.html
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • FTGV
    FTGV Posts: 3,649
    edited January 2011
    I think Borbely published something like that for the now defunct Glass Audio mag.I'll see if I can dig it up.
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  • zingo
    zingo Posts: 11,258
    edited January 2011
    FTGV wrote: »
    I think Borbely published something like that for the now defunct Glass Audio mag.I'll see if I can dig it up.

    Any follow up on this Fred?
    Jake
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  • zingo
    zingo Posts: 11,258
    edited January 2011
    Would I be able to use two unbalanced tube buffers for a pair of balanced inputs? The board below accepts left, right, and ground, and outputs left, right, and ground; three connections ins and outs. That seems like it would work, even though I would have to use twice the boards and tubes. Any comments would be great, thanks!

    260755651_o.jpg

    http://cgi.ebay.com/High-End-Class-tube-buffer-6922-6N11-6DJ8-assembled-/160527006991?pt=LH_DefaultDomain_0&hash=item256027bd0f
    Jake
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  • headrott
    headrott Posts: 5,496
    edited January 2011
    zingo wrote: »
    Would I be able to use two unbalanced tube buffers for a pair of balanced inputs? The board below accepts left, right, and ground, and outputs left, right, and ground; three connections ins and outs. That seems like it would work, even though I would have to use twice the boards and tubes. Any comments would be great, thanks!

    260755651_o.jpg

    http://cgi.ebay.com/High-End-Class-tube-buffer-6922-6N11-6DJ8-assembled-/160527006991?pt=LH_DefaultDomain_0&hash=item256027bd0f

    Yes, that will work. I am doing the same thing with my DIY DAC I am building. Different board, but same concept.

    Greg
    Relayer-Big-O-Poster.jpg
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion." :\
    My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee
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  • FTGV
    FTGV Posts: 3,649
    edited January 2011
    zingo wrote: »
    Any follow up on this Fred?
    Sorry Jake I didn't find the specific article but since you asked.
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  • Face
    Face Posts: 14,340
    edited January 2011
    zingo wrote: »
    Any comments would be great, thanks!
    I hate you for pointing that kit out, lol.

    If those caps are legit(not fakies) and the unit sounds good, it would be a great deal. I may pick up a pair too.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • zingo
    zingo Posts: 11,258
    edited January 2011
    I agree it COULD be a good sounding kit, but is it weird that it only requires a 12v source? Other tube buffer kits I've seen require 12v+200v or something similar.
    Jake
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  • FTGV
    FTGV Posts: 3,649
    edited January 2011
    Sorry Jake I dug through my tech library for that old issue of Glass Audio but no success.And I see Mr Borbely's website is no longer as he has retired.Too bad as he is one of the great audio circuit designers of our time.
    zingo wrote: »
    Would I be able to use two unbalanced tube buffers for a pair of balanced inputs?
    That should be do able if it was fed a true differential signal and the amp has a differential input.What is the amp?
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  • Face
    Face Posts: 14,340
    edited January 2011
    true differential signal=fully balanced?
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • FTGV
    FTGV Posts: 3,649
    edited January 2011
    yes.
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  • zingo
    zingo Posts: 11,258
    edited January 2011
    The class D integrated amp I'm building is based on two 250ASP ICEpower modules. :biggrin: Those boards are a true balanced in, and my NFB-7 DAC is also fully balanced.
    Jake
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  • FTGV
    FTGV Posts: 3,649
    edited January 2011
    zingo wrote: »
    The class D integrated amp I'm building is based on two 250ASP ICEpower modules. :biggrin: Those boards are a true balanced in....

    Ah yes indeed they are ,I had an 250ASP doing subwoofer duties until it gave out the magic smoke.:frown:
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  • zingo
    zingo Posts: 11,258
    edited January 2011
    Do you think the magic smoke was a product quality issue, or just a fluke?

    I'm interested to see how the amps sound with my Klipschs and father-in-laws LSi15s.
    Jake
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  • FTGV
    FTGV Posts: 3,649
    edited January 2011
    zingo wrote: »
    Do you think the magic smoke was a product quality issue, or just a fluke?
    I'm not certain what to atribute it to.It functioned fine for about 2 yrs,then it died.Unfortunately I doubt I will be able to find a schematic as I'm sure B&O are rather secretive about the circuit details and rightly so.Even if I could find one the density of surface mount parts would make it a challenge to service.
    I'm interested to see how the amps sound with my Klipschs and father-in-laws LSi15s.
    I doubt having enough power will be a problem with those.


    btw.the ASP modules have auxillary 12volt(+&-) DC outputs that you might be able to use to power in part atleast your buffer.
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  • zingo
    zingo Posts: 11,258
    edited January 2011
    FTGV wrote: »
    btw.the ASP modules have auxillary 12volt(+&-) DC outputs that you might be able to use to power in part atleast your buffer.

    My plan in to run the A/C main into the ASP boards, power the buffer of the aux 12v from each board, and add a passive, balanced, resistor-based shunt stepped attenuator between the tube buffers and the inputs on the ASP boards. In theory it should be a nice amp.
    Jake
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  • FTGV
    FTGV Posts: 3,649
    edited January 2011
    Tube input buffer + stepped attenuator + high powered Class D amp + fully balanced input to output = very cool .
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