Sunday, June 21, 2009

Topping M1 Class "T" Headphone Apmlifier (Tripath TA2024 Chipset).

The Topping T-Amp is a so-called Class T integrated amplifier, based upon the Tripath TA2024 chip set. the chip makes use of a kind of "Digital Power Processing", this is, more or less, a Class D amplifier with a very high rate of switching . That is why they put the word "digital" into it. Actually, there's nothing really digital about it inside, not in terms of D/A conversion.

Output Power 120mW*2(32Ω)

6mm panel

Signal-to-Noise Ratio (SNR) 98dB
Dynamic Range 98dB
IHF-IM Distortion 0.1% @ 1W, 4ohm
THD Distortion
0.03% @ 9W, 4ohm

0.1% @ 11W 4ohm
0.1% @ 6W 8ohm
10% @ 15W 4ohm
10% @ 10W 8ohm
Power Efficiency 81% @ 15W, 4ohm, 90% @ 10W, 8ohm
Input Sensitivity 200mV

Audio IN RCA (Left/Right) x 1

Power socket (5.5mm/2.1mm) x 1
Output
Speaker OUT (Left) x 1 pair (+ / -)
Speaker OUT (Right) x 1 pair (+ / -)
Power Indicator (Blue LED) x 1
Power Supply input DC 12V~13.2V5A
Dimensions
71mm*26mm*103mm

Weight 1kg

Saturday, June 20, 2009

6H30P-DR "Super Tube"

A double triode, this is an unusual 6922 tube variant (sometimes called the 6H30, 6N30 or 6N30P) which is used in the BAT VK-50SE pre-amp by Balanced Audio Technologies. Sovtek has purchased the factory where they were made and is now importing them for BAT owners. Even though this a variant to the 6922 tube, this tube can not be used in place of 6DJ8 or 6922 tubes in other pre-amps; it can only be used in equipment that is designed for the 6H30!

The 6H30P-DR Super tube is the absolute top grade of the 6H30 tube type. To be certified a DR grade this tube had to pass lengthy and rigorous testing meaning it is much better than the 6H30P-EB or EV versions. It's original use was in critical space and military applications within the Soviet Union. This is the same 6H30 Super tube was dubbed the Super tube by Balanced Audio Technology in use in BAT equipment. The 6H30P-DR tube is also known as 6H30P-DP and 6N30P-DR.



"6H30 Data"

Lifetime not less 10000-20000h! Highly-durable and extra long life, double triode with separate cathodes. Orginal application was for use in pulse mode in special equipment for space by Soviets.

6H30 is now used in reference level pre-amplifiers of Audio Research and Conrad Johnson to name a few.

  • Name: 6N30P-DR
  • Type: Double triode with separate cathodes, highly-durable, extended-life span
  • Application: application in pulse mode in special equipment
  • Cathode: type oxide, indirect heating
  • Envelope: glass, miniature
  • Mass,g: 20
  • Filament voltage,V: 6,3
  • Filament current,A: 0,725-0,9
  • Anode voltage,V: 80
  • Anode current,A: 0,03-0,05(3A in pulse)
  • Anode power,W: 4
  • Steepness,mA/V: 15,0-23,0
  • Microphnic noise,mV: 50
  • Gain: 12,0-18,0
  • Socket type: rsh8
  • Sunday, June 7, 2009

    Elekit TU-884CB 12AU7 Tube Output CD Player.

    真空管ステレオCDプレーヤー(TU-884CD)組

    立解説ダイジェスト版 Elekit (Japan) CD

    Player Kit with 12AU7 Tube output:





    ELEKIT TU-884CD Test


    Poem: Intolerant Egotistical Old Man.

    Today I met an intolerant
    egotistical old man so proud
    and so full of himself that he
    could not see right from wrong.

    So filled with notions that only
    what he could see as far as his nose
    was right and true no matter
    how wrong he may be.

    I felt sorry for this old fart,
    since he will not be able to mend
    his ways since his days he
    would be counting.

    Sorry that he has fewer and
    fewer friends, his insolence so
    overpowering like the stench from
    an age old sewer.

    For he cannot see, even
    with his reading glasses, these would
    not help since his mind is shut.
    Shut from all truths.

    He is purging his life,
    purging his life away of all friends and
    acquaintances because he is
    so filled with his own selfish
    and egotistical beliefs.

    He is right and everyone
    is wrong, if that were true
    then let me be counted by
    him amongst those in the wrong.

    As I do not want to become
    an Intolerant Egotistical Old Man
    like him alone in his last
    days!

    Sunday, May 31, 2009

    My Love - Westlife



    Peace In Our Lifetime.


    Nature ~ Humanity ~ Environment
    UNITING ALL CAUSES, ALL PEOPLE, ALL CULTURES, NATIONS, ALL BELIEFS & NON~BELIEFS

    Go to: "Peace In Our Lifetime"

    PLANTING SEEDS

    a SEED is:







    a BEGINNING
    of a new possibility

    a START
    of something new

    a STARTING POINT
    to make it real and let it grow

    to SOW we:















    PLANT SEEDS
    of possibility, that

    SPREAD
    everywhere and

    PROPOGATE
    in it's own unique way, and naturally

    DISSEMINATE
    to wherever it leads us - we

    INTRODUCE
    new paradigms and ideas and

    IMPLANT


    FREEDOM in everything we do

    Analog VU meter kit (ver.2) From JM7RTI Institute


    Ever wanted to add a nice analog VU meter to you headphone amplifier project or your amplifier projects. Well you need the analog VU meters and in addition a VU meter driver amp board. It's a bit of a hassle, but I found a nice kit for the driver amplifier board for analog VU meters from JM7RTI Institute shipped to me for US$20.00. You just need to add your own VU meters, or you can also order seperately a set from them.

    "JM7RTI Blog & Information page"

    If you are interested, drop JM7RTI, Kimura Hideki san an email to order: jm7rti@gmail.com He will accept PayPal payments.


    Valve Substitution Table.

    Table for valves substitution


    12AX7

    :

    12AX7WA, 12AD7, 5751, 6057, 6681, 7025, ECC83, ECC803...

    12AU7

    :

    12AU7WA, 5814, 6067, 6189, 6680, 7318, 7730, ECC82, ECC802, ECC186...

    6DJ8

    :

    6922, E80CC, E88CC...

    12AT7

    :

    12AT7WA, 6060, 6201, 6679, 7316, 7728, 7730, ECC81, ECC801, ECC85, 6AQ8...

    6CA7

    :

    6L6GC, 5881, 7581, EL34, KT66...

    6BQ5

    :

    EL84, 7189...

    6550

    :

    KT88, 7027...

    6SL7

    :

    5691, 5755, 6188, ECC35...

    6SN7

    :

    6BL7, 6BX7, 5692, 6180...

    6CA4

    :

    6V4, EZ81, EZ80...

    5U4

    :

    5AS4, 5AU4, 5R4WGB, 5931...

    5AR4

    :

    5AW4, 5AQ4, GZ34...

    Saturday, May 30, 2009

    Audio Space Acoustic Laboratory AS-2.8i Tube Intergrated Headphone Amplifier (4 x 6V6, 2 x 12AU7, 1 x12AX7)

    Teaser Pics Now, Details Later


    Vacuum Tube Integrated Headphone Amplifier
    Model No. : AS-2.8i
    (275 x 266 x 160) mm Weight: N.W. 7.8kg/ch / G.W. 8.9kg/ch
    Input Impedance:
    Output Impedance: 4-16 Ohm
    Output Power: 10W x 2 Class AB1 P-P(Ultralinear), 15W x 2 Max.
    Power Consumption:
    Damping Factor: > 3
    Frequency Response: 20Hz - 30KHz / -1dB
    T.H.D.: <1% 20Hz - 20kHz(Ref. Output)>
    Total Gain: 30dB
    Input Sensitivity: 300mV - 600mV
    S/N Ratio: 89dB

    Channel Balance: /- <
    1dB 20Hz - 20KHz (Max. Volume)>
    Channel Separation: > 60 dB (1KHz - 3.3KHz)
    Tubes: 6V6 x 4, 12AX7 x 1, 12AU7 x 2
    Hum Noise:
    less then 3mV

    Present tube Rolling:

    I have left the present stock Sino black glass 6V6 tubes in place since I have not decided on tube rolling types. However have rolled the following:

    12AX7 changed to Telefunken Smooth Plate 12AX7 (ECC83) -


    2 x 12AU7 changed to NOS Matched Pair Tungsram 12AU7 (ECC82)-



    Saturday, May 23, 2009

    The Homebrew 6DJ8 Single Tube Headphone Project.

    New beginnings, I am embarking on the construction of a 6DJ8 Single tube headphone amplifier and will during the course of construction add photos and description on the work and components. This is a tube hybrid amplifier. The first set of photos are of the cabinet and the pcb board being measured and prepared for mounting to the cabinet. the cabinet is lovely DIY cabinet called "Oceania" which is designed for headphone amplifier projects. The power for the pcb is 24V DC (low voltage) and on board regulation is accomplished by the LM317 (in my case I have upgraded to Linear Technology LT-1085). The volume use in this instance is a Blue Alps 2 x 100K A pot.


    The power supply used will be a 24 V switching power supply and will be outboard and not housed in the same cabinet.

    Stage 1 ( Cabinet & Hardware):


    Above: The PCB for the amp layed in the bottom cabinet being measured for placement.


    Above: The 6DJ8 Headphone Amp. front panel facia.



    Above: The top half of the slide on cabinet.



    Above: The hardware, knobs, feet and on/off button.


    Stage 2 (PCB population):

    Stage 2 is the population of components on the PCB, the following photos show the speed of which the components have already become populated.

    Sorry for the quality of some of the photos, the digital camera will need to be replaced at some stage!

    Above: The front panel beginning to take shape, the phone socket fitted, the Alps volume pot fitted and a nice custom made Goncalo Alves Wooden 1/4 gloss finish knob fitted.

    Components:

    Tube Socket: Gold Plated / Ceramic Tube Socket for 6DJ8

    Tube: NIB NOS Tungsram 6DJ8


    Regulators: LM-317 - Replaced with Linear Technology LT-1085

    Semicon.: K117 x 2, K310 x 2


    2SK117 x 2 :
    Field Effect Transistor Silicon N Channel Junction Type Low Noise Audio Amplifier Applications.

    Toshiba 2SK117 Data Sheet PDF.

    3SK310 x 2 : 2SK310 Silicon N-Channel MOS FET (High Speed Power Switching) - Hitachi Semiconductor.

    Hitachi 2SK310 Data Sheet.


    Resistors: Dale Vishay & Tokyo Ko-on


    10 ohms x 2
    13 ohms x 2

    15 ohms x 2
    35 ohms x 2
    100 ohms x 2
    220 ohms x 2
    2K ohm x 1

    2.2K ohms x 2
    1M Ohms x 2 (1watt)

    VR - Blue Alps 2 x 100K A

    On board VR: 2 x 1K ohms Bourns

    Fuse (pcb mount): Silver plated contacts

    Capacitors:

    Musicap "Hoviland" 0.1uF PP x 2

    220uF x 2 Black Gate 16V
    1000uF Elna "For Audio" 50V
    1000uF Nichicon 35V


    Misc:

    1 x Headphone Chassis

    1 x gold plated panel mount headphone socket
    2 x gold plated panel mount RCA sockets

    1 x 24 DC panel mount DC connector
    1 x LED

    1 x push button on/off for panel mount
    4 x isolation feet
    1 x 24 DC switching power supply housed seperately
    4 x heatsinks for semicons

    The Finished Project:


    I finally finished the project on 26th June, 2009 and here are the photos of the completed single tube 6DJ8 headphone amplifier which is up and running and using a NOS Tungsram tube:


    The heatsinks were replaced on the FET's and regulators with larger ones, the amp does not run too warm and is quite cool. One drawback is the LED configuration (refer to the circuit diagram), this is a bad design to be taking voltage for the LED from this location as it does cause oscillation when powering up the amplifier and you "Must" not plug in the headphones as you will hear a high pitched whinning sound. Only when the LED is fully lit and the circuit becomes stabilized should you plug in the headphones. The designer should rethink about the LED issue! I am using an off the shelf 24V DC (2amp) switching mode power supply which is available everywhere (ebay) and it is very quiet, the supply is not housed in the same cabinet and is external to the unit to minimize on any further noise. Of course you may choose to use a linear supply if you wish.

    Dynamics and transients are extremely good, bass impact is extremely good and mids-highs are well balance with high resolution. The NIB NOS 6DJ8 from Tungsram is an extremely high resolve tube and well suited to the amplifier. The sound stage is extremely deep and location of musical instruments is very precise. I expect things to further improve as the Hoviland "Musicaps" begin to burn in, since I have currently about 50 hours of time on the amp. One can hear the changes each time, the bass appears to be becoming tighter and better controlled.

    The
    Linear Technology LT-1085 regulators will be a night and day difference over the original LM-317 regulators and my advice is not to skimp on these regulators and change them to the Linear Technology regulators! You will have a much faster amp and the difference is stunning to say the least.

    I have used
    Musicap "Hoviland" 0.1uF PP x 2 caps. as I have found that these give the warm SQ that I want from this tube. Other caps used ar Black Gates and Nichicon, you must experiment with caps as these will alter the SQ signature of the sound. Overall, it is a very quiet amp and audio qulaity is very good once completely warmed up. The circuit board can be found on ebay and sells for about US$8.00.

    I have received enquires about the cabinet and volume knob, the cabinet is off the shelf made for headphone amplifiers and can be found on ebay, whilst the
    Goncalo Alves Wooden 1/4 gloss finish knob is a custom turned knob and is a once off item.

    Friday, May 15, 2009

    Sheryl Crow.


    I Dont Wanna Know - Sheryl Crow





    Artist: Sheryl Crow
    Song: Wildflower

    Wildflower - Sheryl Crow

    Capo – 3th Fret

    Intro
    E|---1-----1----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|

    E|---1-----2----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|


    (First Verse)

    Quiet eyes You have always been my
    E|---1-----1----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|

    Wildflower Showing up wherever
    E|---1-----2----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|

    Beauty's lost its way Your heart must break
    E|---------------------------------------------------|
    B|--1----1-----3------3----3-----3-------------------|
    G|--2----2-----3------3----4-----4------5--4---------|
    D|-----3---3---3---3----3--5---5---5----3-----7—5----|
    A|--3----------1-----------5------------5------------|
    E|--1----------------------3-------------------------|

    E|---2-----2----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|


    I was free Until I heard the song
    E|---1-----1----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|

    you sang me to me Pulling me away from
    E|---1-----2----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|

    Every thing I knew To be with
    E|---------------------------------------------------|
    B|--1----1-----3------3----3-----3-------------------|
    G|--2----2-----3------3----4-----4------5--4---------|
    D|-----3---3---3---3----3--5---5---5----3-----7—5----|
    A|--3----------1-----------5------------5------------|
    E|--1----------------------3-------------------------|

    you
    E|---2----2---5---5---2------|
    B|---3----3---6---6---3------|
    G|---2----2---5---4---2------|
    D|---0--0---0---0---0-0------|
    A|---------------------------|
    E|---------------------------|

    And everything I know just fades away
    E|---------------------------------------2-----2-----|
    B|----1---1--1--1--3----3----31—---3-----3-----3-----|
    G|----0---0--------2----2----2-----2-----2-----2-----|
    D|----3---2--0-----3--3---3--3--3----3---0--0-----0--|
    A|--------------3--2---------1-----------------------|
    E|---------------------------------------------------|


    And every time you go it hurts me
    E|---------------------------------------|
    B|----1---1--1--1--3----3----31—---3-----|
    G|----0---0--------2----2----2-----2-----|
    D|----3---2--0-----3--3---3--3--3----3---|
    A|--------------3--2---------1-----------|
    E|---------------------------------------|

    so I don't know why but I know we're
    E|--------------------------------------------------------------|
    B|--1----1---8-----8-----3-----3----------------------3---------|
    G|--2----2---8-----8-----3-----3----3h5p3p0-----------3---------|
    D|--3--2---2-8---8---8---5--5----5------------------3--3--------|
    A|--3--------6-----------5--------------------0--1---------1--0-|
    E|--1--------------------3------------------4-------------------|

    free Free to
    E|---------------------------------0---|
    B|--3-----3---------------3----2—3-----|
    G|--3-----3---------------3----3-------|
    D|--5--5----5----------3----3--2-------|
    A|--5-------------0--1---------1-------|
    E|--3----------4-----------------------|

    fly
    E|---2-----2----5----5----5----5----5----5----|
    B|---3-----3----6----6----6----6----6----6----|
    G|---2-----2----5—---5----4----4----3----3----|
    D|---0--0----0----0----0-----0---0-----0---0--|
    A|--------------------------------------------|
    E|--------------------------------------------|


    (Second Verse)

    Here we are
    Burning faster than the cursed star
    Falling back down to the Earth
    I love you so it sometimes hurts

    Closer still
    You will find me standing on the hill
    Waiting for you with my arms stretched open wide
    Now, come inside

    And everything I know just fades away
    And every time you go it hurts me so
    I don't know why but I know we're free
    Free to fly

    And everything I know just fades away
    And where the wildflower grows it picks its space
    And that's the way it is when nature plays its lovely hand
    We'll understand everything

    E|---2-----2----5----5----5----5----5----5----3|
    B|---3-----3----6----6----6----6----6----6----2|
    G|---2-----2----5—---5----4----4----3----3----3|
    D|---0--0----0----0----0-----0---0-----0---0--0|
    A|---------------------------------------------|
    E|---------------------------------------------|


    Everything, everything
    (Resolves on F major)

    Thursday, May 14, 2009

    Portable Cans: (Japanese) Excel Sound EH-98 Dynamic Portable Headphones.


    A friend was recently traveling through Tokyo taking the opportunity of the cheap air fares currently available. It was nice of him to think of me when he was in Akihabara, he stopped into one of the hi fi shops and picked up a pair of portable headphones and brought them back as a gift for me. What is unusual is that he choose to pick up a pair of headphones by a Japanese company called "Excel Sound" which is basically not known at all outside the Japanese domestic market. The cans indeed do not look like anything special, a very rudimentary pair of plastic portable cans, but only available for sale on the Japanese market. So they are indeed rare to be found outside of Japan.

    The cans are the portable / fold able "Excel Sound EH-98" dynamic cans and from what I can understand of the Japanese, they have 40mm drivers and have OFC headphone cable.

    On first listening to them I was taken back by the fact that they did not sound at all bad, quite neutral, in fact they were pretty good. I am burning them in over the next few days and will give you more details on these rather rare cans. Of course some more photos will be taken. The pair I have is the EH-98bk (bk = black), if fact the plastic is more like charcoal grey. The inset photo is what I could find on the Japanese site on the EH-98.

    Comfort wise, they are very comfortable, lightweight with no clamping of the head and ears.

    Tuesday, May 12, 2009

    Oumeidanji KT-88 Valve Amplifier.

    The Oumeidanji KT-88 Valve Amplifier is a unique amplifier since it is capable of using the KT-88, 6550 or the EL-34 tubes in the same amplifier. The amplifier was designed as a small integrated for driving a pair of speakers and it does support a headphone amplifier out with an impedance of between 300 - 600 ohms. I would not recommend to drive headphones of lower impedance since it would become a burden on the amplifier. The amplifier runs in Class A and once warmed up it does run hot, so strongly ventilated areas are recommended. Since the amplifier will drive 300-600 ohm cans, these are well suited to the likes of by Darth Beyers or other Beyer Dynamic headphones.

    Driving the pair of KT-88 are a pair of Chinese 6J8P tubes, and I did not bother with these. The western equivalents are the 6SJ7 or the premium 5693 metal cans. From the photos below you can see that I rolled the amplifier at first with a pair of RCA NIB NOS 6SJ7 matched pairs and then a pair of General Electric 5693 matched pair "Red Tubes". A note about the "Red Tubes", regardless of what brand you find imprinted on them, all "Red Tubes" are manufactured by RCA.

    Whist the Black Metal RCA 6SJ7 Tubes were good, they were sonically no match for the superior "Red Tubes" and this accounts for the vast difference in price between the two in the market place.

    The supplied pair of KT-88 tubes are from "Shuguang" of China, but I am very likely to change these to a pair of "Gold Lions" in the near future.

    RCA 5693 "Special Red" Tubes

    Replaces 6J8P, 6SJ7, and 6SJ7GT tube types. The RCA "Red" tubes (5690, 5691, 5692, 5693) were designed for 10,000 hours of use. RCA claimed the 5693 tube could withstand shocks of 100 G's for extended periods of time! These are the best upgrade tubes for this amp.







    Photos below show the amplifier rolled with the General Electric 5693 "Red Tubes" which are NOS matched pairs.


    In fact regardless of what brand is printed on these red metal cans, all the "Red Tubes" were manufactured by RCA.


    The "5693 Red Tubes" are sonically superior to the 6SJ7 Black Metal Tubes and of course far superior to the stock 6J8P which I did not even bother with.




    The Specs:

    • Shuguang KT88 X 2 , 6J8P X 2
    • Output Impedance : 8 ohm
    • Output Power :2 x 10 W (Class A)
    • Earphone Output Impedance 300-600 ohm
    • Frequency Response:5HZ-200KHZ
    • T.H.D. <>
    • Length 160mmx Height 170mmx Depth 320mm
    • Weight: 9kg
    • Color :Black
    • Power: Switchable 110V - 240V (50Hz -60Hz)
    Review CD's:

    1. Audiophile "Timeless Best Collection" 24 bit / 96khz DSP Mastering URCD;
    2. Wild Blue "Jeanne Newhall";
    3. We Miss You, Leslie "Chris Babida";
    4. Dark Side of the Moon "Pink Floyd";
    5. Tubular Bells "Mike Oldfield";
    6. Variations "Andrew Lloyd Webber";
    7. Hotel California "Eagles" - Japanese CD pressing;
    8. 2AM "Danny Summer" XRCD;
    9. Natural Elements "Acoustic Alchemy";
    10.Breakdown "Paulinho Da Costa";
    11.Gold Lion KT88 Vacuum Tube Audiophile Recordings "HECM - Musical Fedelity Recording";
    12.Eternity "Angella Christie";
    13.Hi-End Audiophile Test Demo "HD Mastering - ABC Recordings";
    14.The Tube Hi-Fi Saxaphone " High Resolution Tube Recording - ABC Recordings";
    15.Headphone Test Disc "ABC Recordings";
    16.Memorial Version 30 years - Tubes "ABC Recordings";
    17.Luxman 2009 Demonstration Disc " DSD recording";
    18.Blue Skies "Stan Getz";
    19.vol.SOUND "S.E.N.S."


    Update 1: 30th May, 2009

    Burn in is approaching close to 90 plus hours and the amplifier appears to be beginning to open up, the red tubes make a substantial difference to the overall timbre and sonic performance of the amplifier. I have still yet to decide on rolling of the KT-88 tubes and will leave them for now. I can hear the bag end (bass) tightening up and becoming better controlled. Once I near the 150 hour burn in mark I will report again. One thing, this is an amp for 300-600 ohm phones and it does not like the low impedance types - you will hear some hum with the low impedance phones. Phones in the right category work great with it!