powering 600ohm cans?

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powering 600ohm cans?

Postby jkhuri44 » Sat Jul 09, 2016 8:58 pm

Hi all,

Does anyone here have any experience with amplifying 600ohm headphones?

I bought Beyerdynamic's DT880 - 600 ohm version, and went down to a hi fi shop in newtown to try out a few amps in store for them....i tried Schitt, Bryston, etc etc and found all of them to be lacking in both fullness, bass, and volume.

Schitt was also advertised as high power tube amp....

Does anyone know what the hell amplifies 600 ohm cans sufficiently? either brand, topology, whatever it may be....

I'm currently using a 1990s nakamichi hi fi amp, which does an incredible job, but it needs to be turned up to nearly half way to do the trick. This amp is bloody incredible ...for speakers too...and aparently the headamp section is excactly the same but with resistors inline....but im keen to see if there's something better.
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Re: powering 600ohm cans?

Postby wez » Sun Jul 10, 2016 9:37 pm

My (600 ohm) AKG K240s have the same issue - they're great but they do need a lot of juice. Pretty much useless plugged directly into a macbook, ipod etc.

Oh sorry I don't have a solution, just empathising ;-)
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Re: powering 600ohm cans?

Postby gigpiglet » Mon Jul 11, 2016 9:34 am

my headphone amps that rob squire built are AWESOME.
plenty of juice in them.
and if you wanted one specifically for 600ohm cans im sure that would be a small change for him to make to get the best out of them.
get in touch with rob - he will have an (affordable) solution for sure
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Re: powering 600ohm cans?

Postby rob » Mon Jul 11, 2016 9:38 am

thanks Gareth. The Headphone amps I make will deal with 600ohm headphones out of the box and be loud enough.
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Re: powering 600ohm cans?

Postby jkhuri44 » Mon Jul 11, 2016 11:59 am

haha thanks wez...

i was especially bummed as i built a DIY headamp which i was looking forward to using with these, and they must need to be modded to suit 600ohm headphones...grrrrr!

i did ask the project owner if iot would work with these, but yeaaaah, didnt quite work out
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Re: powering 600ohm cans?

Postby rob » Mon Jul 11, 2016 12:05 pm

if you want to DIY a headphone amp that will work with your cans, get a JLM kit. It will work without modification. ( or be even louder with a small mod but then it will lose it's universality and not be so good with 32 ohm cans.)

There is no free lunch
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Re: powering 600ohm cans?

Postby gigpiglet » Mon Jul 11, 2016 7:32 pm

ive bought you lunch plenty of times rob.... ;-)
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Re: powering 600ohm cans?

Postby jkhuri44 » Mon Jul 11, 2016 8:30 pm

thanks for chiming in rob!
could i ask on an educational note, what specifically to look out for when qualifying an amp as being able to amplify 600ohms? i know it's probably a basic question, but thats me :P
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Re: powering 600ohm cans?

Postby rob » Wed Jul 13, 2016 11:11 am

Gareth - of course you have.
In fact quite a few here have and that is always one appreciated free lunch.

Driving 600ohms - the simple concept is to put x amount of power ( volume ) into your ears. If the device doing this is of a higher impedance then it will need more volts ( and less current ). If it is a lower impedance it will need less volts ( and more current )
Learn ohms law and it's power variants.
So you have higher than usual impedance headphones so they need lots of volts. So the power supply for your headphone amp needs to run off lots of volts. How many volts does your phone run off? Maybe 3 volts? How many volts does the Pro Harmonic / JLM amp run off - 36 volts and sometimes 48 if we want to squeeze max dbs of headroom out of it.
See the difference -- it's over 20dB

And ... before the more savvy chime in ... the Pro Harmonic / JLM headphone amp compensates for different headphone impedances. So I'm not saying that it will drive 36 volts into you headphones but ... it has the potential to.
Anyone got 10K headphones? I had a pair that were great... you could just plug them into any old line output.
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Re: powering 600ohm cans?

Postby jkhuri44 » Wed Jul 13, 2016 10:45 pm

thanks for the response again rob :)

i see...
i think the mistake i made was building this amp:

http://www.ska-audio.com/diy/HeadAmp.html

as class A....
it can be set up to have 200mW @ 600 ohms ...
i wish i did that before...doh.
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Re: powering 600ohm cans?

Postby rob » Wed Jul 13, 2016 10:58 pm

If you built that and are running it on +/- 18v
and ...if it isn't loud enough there is probably one part to change to get more level

Need a schematic
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Re: powering 600ohm cans?

Postby jkhuri44 » Thu Jul 14, 2016 10:47 pm

hey rob,

the head amp consists of the headphone amp itself....plus what he calls a 'dual reg" power regulator

Schema for headamp:

Image

Parts:

R1, R2 100K 1/4W m.f.
C1, C2 100pF 50V polystyrene.
R3, R4 1K 1/4W m.f.
C3, C4 10uF 16V electro
R5, R6 3K 1/4W m.f.
Q1, Q3 BD139
R7, R8, R9, R10 22 ohm 1/4W m.f. * Q2, Q4 BD140
R11 27K 1/4W m.f. IC1 OPA2134 or TSH22IN
R12, R13 4.7K 1/4W m.f.
3 way terminal block
VR1 10K log dual vol pot
LD1,2 Red or GRN LEDs transistor mounting hardware
HeadAmp PCB . 2 heatsinks and 8 pin IC socket.

I built it to be class A so, changes were:
resistors
R7, R8, R9, R10 need to be replaced with 10 ohm 1/4W m.f. types. The heatsinks will
need to be fitted for best reliability as the transistors are approaching 1/2 their package
dissipation rating. Power demand is ~ 100mA at +/-12V - +/-18V, nominal +/-15V. A
good regulated supply is needed here. The DualReg is ideal.


Dual reg schema:

Image
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Re: powering 600ohm cans?

Postby rob » Thu Jul 14, 2016 11:13 pm

So. Here's the question. Are the cans running off this HP amp just not loud enough with the volume pot flat out.

Or is it distorting before it gets loud enough?
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Re: powering 600ohm cans?

Postby jkhuri44 » Thu Jul 14, 2016 11:48 pm

no distortion, just not loud enough with volume flat out.
i'l double check tomorrow as i've got it packed at the moment, and let you know for sure. but yeah dont remember any distortion
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Re: powering 600ohm cans?

Postby rob » Fri Jul 15, 2016 9:09 am

if you are hitting it with +4 line level it should be very loud
this HP has no series limiting resistor and if the amp is running off 15V power rails will deliver close to a 30 swing into the cans ... this is lots of volts and if it doesn't get loud enough in your cans, either something is wrong or get different cans. How loud is it in 32 ohm Headphones?
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Re: powering 600ohm cans?

Postby jkhuri44 » Tue Jul 19, 2016 9:24 am

i blew a pair of 32ohm cans....haha....after i disconnected the 600ohm ones to try another pair :/ so this thing is loud....and to answer previous question, there is no distortion at any stage, even at full volume with the 600 ohmers.
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