[luke1]

I read a lot over the winter months and I finally decided to buy (I found them used) of the AKG K501. I listen to lots of classical music and a bit 'jazz.
Almost always, now, the source is my netbook to which I connect an Musiland 01US that works well (at least with the traditional system connected to the KEF Corelli's vintage '79).
With the new headphones, however, the output of Musiland not convince me that much. The sound and very low in back and the headphones sound a little 'too high with no heat.
I've tried to an old traditional system (headphone output of a JVC JA-S22) and the sound improves significantly.
I read that the K501 need to be controlled according to the IEC standard.
My budget is about $ 200. What could you advise me to amplify to the best of my headphones?
Do not try to color the sound, but only to exploit them at best.
I also thought of building an amplifier, maybe a valve, alone (I manage with a soldering iron) but I could not find a pattern with the right output impedance (and maybe with a good transformer output) in my budget.
Thanks to all those who want to help me out!

 

[MrSlim]

Congrats on snagging the 501's!  
The CK2III from amb  http://www.amb.org/audio/ck2/ is well regarded for the price(you should be able to build it for $200). 
 
Another option might be the Panda amp that they are raving about on Rock Grotto http://rockgrotto.proboards.com/index.cgi?board=m&action=display&thread=5700&page=1, particularly for the K701's which are notoriously hard to drive
correctly.  The Panda should also be able to be built for under $200, as the basic kit(PC board, and parts) is only about $85.  You probably won't be able to build one with a fancy front panel ala Front Panel Express, but you should be able to build it in a basic Par-Metal case, with an Antek power supply and the various connectors, etc for $200.
 
  I am in the process of building both a CK2III and a Panda, (and a Beta22 for a friend) and have K601's and HD580's which I am really looking forward to trying with them.   I plan on being busy over the Christmas/New Years break..
 

 

[luke1]

Thanks for the advice!
However I would like to try a tube amplifier with high output impedance (120 Ohm), can you suggest one?
Thanks again.

 

[dBel84]

The problem with the K501 is that it is not particularly sensitive and really needs a powerful amp to show its colours. ( I still own a pair - in fact the only dynamic headphone I have kept in my collection) Have you considered using your power amp to drive them? You could make a simple adapter quite cheaply, or for about $150 get a transformer device ) As for amps in your budget, I would think about hybrid designs if it is a tube flavour that you are after. You will not be able to build a powerhouse tube amp for $200 and even the transformer coupled amps will double your budget. Dsvastik's less pressivo - a parafeed design with good performance would fit in your budget. There are many hybrid designs out there, some that you could probably buy for about $200 , DIY options include the CTH and the Max (mini). These are the budget options but by no means inferior, I am a great supporter of Cavalli designs ( no secret here ) and I use one of his amps to drive my headphones. The amp I have is capable of 25W into an 8ohm load so a powerful amp , but well over the $200 budget. The EHHA would be such a powerful amp if you wanted to explore this possibility a little more. 
 
You could even try the simple 6DJ8 amp as an exploration into hybrids, this would be well below budget and still offer you good sound and the power to drive the K501. 
..dB
 

 

[Pars]

I would also think Amb's M3 (not to be confused with the mini3) would drive 501s quite nicely. Ideally you would want to use Amb's sigma11 as the PSU for this, but you could add that later to keep within your budget. I believe that GlassJarAudio will supply a kit for the M3; you would need to contact him though as it is not shown on the site. I drive my 601s with a Gilmore Dynalo, and have run 501s with it as well.

 

[luke1]

Thank you all for your valuable advice.
I realized that probably the best way forward would be solid state (there is certainly more choice in my budget) but as I said I'd rather go on the tube

I had thought of using my power amp but it is a card that has TK2050 Sure outputs in bridged mode and the patterns of the various resistive dividers can not be used with this type of amplifiers (true?)

Having no way to make PCBs rather stay on simple circuits, such as the 6DJ8 Simple would be a good compromise (I think I have understood that the PCB is on ebay ...). It seems very interesting also the "less pressivo" safe side, but I'm not sure of being able to easily find parts here in Italy.

Next if you have more ...

 

[peppe]

 
If the amp itself does not have much/any output impedance you can add output impedance.  In most designs if you use TRS jacks you should add at least a small output resistor to each channel to mitigate the TRS connector shorting on insert/removal.  If you want to get 120 ohm output impedance and you know the output of the amp just add a resistor to each channel output to sum up to 120 ohm. 
I have an order on the way to try out various resistors on my CK2III from 2ohm - 120ohm.  CK2III has < .5 ohm output impedance.  I didn't feel like adding a switch to the unit, but you can put the resistor on a switch to toggle between a high and a low output impedance.
 
You don't have to make your own PCBs for any of the builds previously listed. 
 
The CK2III board is at AMB's site is $12 and he also stocks the hard to find or to individually source parts for you to buy along with the board.  Go to his shop page, http://www.amb.org/shop/,  and switch to CK2III to see.   You should be able to source the rest of the parts from a eurozone supplier.  You can probably search this forum and find out who everyone uses.
 
The minimax kit, while being $220, comes with everything you need.  The custom case with all the holes pre-drilled will save you many hours.
 
There is a group buy thread for this Point to Point tube amp to get it for $180, Crack OTL Headphone Amplifier Kit - http://www.bottlehead.com/store.php?crn=44&rn=442&action=show_detail.  Comes with 120ohm resistors to make its output impedance 120 ohm. Group buy:  http://www.head-fi.org/forum/thread/527004/bottlehead-crack-group-buy.  I'm not too familiar with this amp, but looks like the 'Speedball' upgrade makes it into a hybrid and can be added down the road...

 

[holland]

Use 2 jacks.  One wired with a resistor, the other not.
 
I've not heard of TRS jack shorting out the output transistors in the C2KIII, however, if it's a concern, changing the 0.47 ohm resistors to 2.2 ohm will work just fine.  There's no real need to add additional series resistance unless you want to hit a high Z output jack, in which case you can use 2 jacks as noted in the prior paragraph.
 
For $200, I don't think you can get better than the C2KIII or the Dynalo.

 

[peppe]

 
Thanks holland, I haven't heard of any CK2III having problems with TRS jacks, but I wanted to experiment with mine to see if the Beyers respond better to more output impedance and while I was at it understand why more powerful amps can damage themselves with a TRS jack. I have my eye on the EHHA Rev A and Beta 22.  Pretty sure the EHHA bom has a 100 ohm output resistors for the default build, so it should survive TRS jack abuse.  A saw a response by Ti on the Beta22 that recommend swapping out some resistors from .47 to 2.2 ohm to improve the Beta's tolerance of the TRS jack short.
 
For now I am planning to socket various resistor sizes at the output to see how they change the sound with my 600 ohm Beyers.  If i find something I like i will just make it a permanent change as I rarely use other headphones on my CK2III and don't plan to sell it.   I was thinking about using a small toggle switch to go from low z to high z as I used the big neutrik locking jack, so not much room in the little hammond case to stick another one.   Had a planned ahead I think it would be a good simple option to have a low z and high z jacks in parallel.
 

 

[holland]

Quote:

 
Thanks holland, I haven't heard of any CK2III having problems with TRS jacks, but I wanted to experiment with mine to see if the Beyers respond better to more output impedance and while I was at it understand why more powerful amps can damage themselves with a TRS jack. I have my eye on the EHHA Rev A and Beta 22.  Pretty sure the EHHA bom has a 100 ohm output resistors for the default build, so it should survive TRS jack abuse.  A saw a response by Ti on the Beta22 that recommend swapping out some resistors from .47 to 2.2 ohm to improve the Beta's tolerance of the TRS jack short.
 
For now I am planning to socket various resistor sizes at the output to see how they change the sound with my 600 ohm Beyers.  If i find something I like i will just make it a permanent change as I rarely use other headphones on my CK2III and don't plan to sell it.   I was thinking about using a small toggle switch to go from low z to high z as I used the big neutrik locking jack, so not much room in the little hammond case to stick another one.   Had a planned ahead I think it would be a good simple option to have a low z and high z jacks in parallel.
 

The Beyerdynamic headphones like 100-120 ohm output, IMO etc. etc..  Their A1 amp has 100 ohm output.  I either use an inline adapter or 2 jacks with different impedences in my more recent amps.  The inline adapter is easy to make and generic enough.
 
EHHA uses 2.2 ohm for the Mosfet and 10 ohm for the BJT versions.  The JISBOS uses 2.2, and the Beta22 can use 2.2 for TRS shorts.  The CTH has 0 to 100 ohm optional resistors, in addition to the 6.8ohm in the diamond buffer.
 
Socketing is fine, but might be easier to "socket" an inline wire if you're going to be experimenting alot.  That way you don't need to open the amp or leave it opened.