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Cheap headphone amplifier to drive 600 ohm headphones.

Shadrach

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#1
I've worked my way through lots of the head amp tests (great job amirm) but the in the tests I've read, 300 ohm is the highest impedance mentioned.
I have two pairs of 600 ohm headphones, Sennhieser 595 and Beyerdynamic DT 880.
Currently I'm using a World Audio HD83 valve headphone amp which I built. This drives the above headphones with ease.
The stated sensitivity is 30mV in giving 180mV out into 30 ohms. I have no idea what it does with a 600 ohm load.
The HD83 sounds very nice but it's far to heavy and fragile to be easily transportable. Any suggestion doesn't need to fall into the portable category but under 1 Kilo in weight would be handy.
I like my bass, I can't hear much above 11 KHz.
Something under 150 GB pounds is the price range I'm looking for.
 

RayDunzl

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#2
The stated sensitivity is 30mV in giving 180mV out into 30 ohms. I have no idea what it does with a 600 ohm load.
A 600 Ohm load is less demanding upon the amplifier than a 30 Ohm load on terms of current delivered, so, I would expect the output voltage of the World Audio HD83 to be at least 180mV and possibly more.

I have no suggestion for a different amp.
 

solderdude

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#3
Do you mean the HD595 ?
As far as I know it is 50 Ohm.

The DT880-600 needs a higher output voltage.

The WAD is specified for 1W and has a >250 Ohm tap so expect about 0.5W in 600 Ohm = about 15Vrms. when set to this tap.
When the 16-50Ohm tap is used there will be max 6V = 60mW in 600 Ohm
In S.S. you need an amp with at least +/- 24V power supply rails for a 1 to 1 replacement in output power.

IMO the DT880 works fine on +/- 9V rails though so battery fed devices should be able to work as well.
 

Shadrach

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#4
Thank you both.
I'm reasonably happy with the sound I get from the WAD, but it isn't really portable and I'm looking for something more robust and lighter to travel with.
I'm also interested in hearing something with modern solid state specifications that will drive the 600 ohm headphones to an acceptable level; probably around 85 db.
 

solderdude

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#5
JDS Atom amp comes to mind which can output 125mW in 600 Ohm (which is the DT880-600 max power rating and can drive the HD595.

Won't sound the same as the tube amp because that one has a higher output resistances and thus boosts lows somewhat (a lot for HD595)
 

AnalogSteph

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#6
A DT880-600 needs about 0.5 Vrms for 90 dB SPL. With about a 17 dB crest factor, you'd want ~102 dB SPL max, that would be ~1.9 Vrms. This should be within the range of quite a lot of headphone amplifiers. Two questions:
  1. What's your source and how loud does it go? A smartphone (often ~400 mV max) might need a gain of >12 dB (4X) for the desired output level, some amps only provide 8 dB (2.5X).
  2. Is mains operation required or is battery operation also an option?
Some popular candidates include SMSL SAP II (should have plenty of power, but gain unknown, possibly 6 dB) and FiiO A3 (high gain = +12 dB).

As mentioned, the HD595 never came in 600 ohms. Most of them would be a nominal 50 ohms, with early samples at 150 ohms.
 

Shadrach

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#7
JDS Atom amp comes to mind which can output 125mW in 600 Ohm (which is the DT880-600 max power rating and can drive the HD595.

Won't sound the same as the tube amp because that one has a higher output resistances and thus boosts lows somewhat (a lot for HD595)
Thanks, I appreciate that current isn't likely to be a problem but voltage may be.
Not sounding like the WAD valve amp shouldn't be a problem given it's a bit of an effects box.
I read the review here of the JDS Atom (I had never heard of the company before. I'm a bit out of touch with audio gear) and at the price it may well be worth just buying on it's specifications. I prefer to listen to anything audio related I buy at home,if possible, but it isn't possible with most products and my location doesn't help.
 

Shadrach

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#8
A DT880-600 needs about 0.5 Vrms for 90 dB SPL. With about a 17 dB crest factor, you'd want ~102 dB SPL max, that would be ~1.9 Vrms. This should be within the range of quite a lot of headphone amplifiers. Two questions:
  1. What's your source and how loud does it go? A smartphone (often ~400 mV max) might need a gain of >12 dB (4X) for the desired output level, some amps only provide 8 dB (2.5X).
  2. Is mains operation required or is battery operation also an option?
Some popular candidates include SMSL SAP II (should have plenty of power, but gain unknown, possibly 6 dB) and FiiO A3 (high gain = +12 dB).

As mentioned, the HD595 never came in 600 ohms. Most of them would be a nominal 50 ohms, with early samples at 150 ohms.
I have a few possible sources. A few computers, mostly old, a home built music server, but for travel it will probably be a lap top feeding an HRT Pro with a separate 5V power supply, via USB.
I would prefer mains powered although batteries may inject less noise into the system.
I could be wrong, but I'm pretty sure Sennheiser did make a limited quantity of 600 ohm, HD 595s that sold in the UK market and maybe in Europe.
I can't find any reference to them on the Internet but I know someone else with a pair he bought for studio use.
 

Shadrach

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#10
Thanks, I'll have a look through and see if I can find some specifications for the various models.
 

solderdude

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#12
Nope, in fact the amp only needs to deliver less current.
Around the resonance the efficiency in dB/mW rises but in dB/V remains the same.
The impedance reaches 720 Ohm by the way.
 

JohnYang1997

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#15
higher the impedance the easier to drive. No matter it's 1000ohm or 10kohm. If the sensitivity is high enough it's easy to drive.
In terms of the variation of impedance in the frequency. Normally just choose low output impedance headphone amplifiers.
But with beyers it's a bit different. The a1 from beyer has an 100ohn output socket. The dt880 might be designer for 100ohm output amplifiers. But let your ears be the judge. You can get an 100ohm resistance adapter easily.
 

Shadrach

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#16
I built one of these http://sound.whsites.net/project113.htm and use it with Sennhieser HD 650s .... it has power to spare, sounds great, measures well, and is not expensive. Of course you have to build it but at least you know the part quality and will be able to repair it easily which you can't do with the pre-built Chinese units.
I had looked at this before. I've got a lot of time for Rod Elliot; one of the few rational voices in audio over the years. I've built some of his kits in the past and they always performed well.
However, I've done all the building I'm interested in doing in electronics. If I build anything again it will be speakers.
Thanks for the link and a good suggestion.
 

Shadrach

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#17
I think I'm going to try the flavor of the month and get the JDS Atom assuming they can make them fast enough for me to get hold of one.
It is, according to this site at least, pretty much state of the art in performance and I'll be very interested to find out if I can hear any difference compared to my old effects box, the WAD HD83 and which I prefer the sound of.
I haven't had any flavor of the month kit since, oooohhhh, 1970's something.;)
 

tired_guru

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#20
Atom is my reference amplifier now for driving dt880 600 (low sens 96dB) with sdac grace when listening to classical music or very well recorded tracks (and I compared head to head a lot of gear, even very expensive stuff in local audio store, I am extremely picky classical recordings listener). There was a moment I wanted to sell it and have some all in one combo, but nothing sounded so clear and fast, with such resolution and transients handling. There was always something that was NO GO for me regarding classical.

For most of the cases it is fine to use low gain, and trust me, I like it loud sometimes (sdac puts out 2,15 Vrms). High gain is needed when there is low volume recorded file with great dynamics - max I got was about 1-2 o'clock in high gain with them.

So if you like beyers, you know how they sound and you are good with it, atom will show you what they are really capable of. Have no idea why are you still looking :)

For jazz/female vocals/relax I prefer questyle cma400i with hd600 (it can sound almost like with quite expensive wooaudio with it, gets almost max from this headphones that I remember from old pairings), with punchy metal, rock, grunge, alternative, acoustic etc, cma400i with fostex th610.
 
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