Search for some of these on the bay, NuForce Icon DAC or uDAC.  They are small and they have a lot of different models but the headphone amps and DACs work very well with the 650's, 600 and 580's. There is at least one NuForce Icon 2 that might slip into your price range and new it is about $450.

I had the same issue with mine when I first got the balance card.  I had to remove, and reinsert it and press it into the slot really well.  Once I did that it has been working fine and the switch is noticeable.  On regular trs cans simply flick and then down for trrs balanced.  The audio...

I should have stated I am not happy with the bugs in the firmware either but the sound quality is too good to pass on for me. I have ordered a balanced cable for Sennheiser Momentums that should arrive withing a week or so.  It will be the third balanced cable for my headphones so I can enjoy...

  That only has a fixed 32GB?  If so that would be too limiting for me. I'm staying with the HM-901.  Once I worked out the balanced amp card installation issues I have had no problems.

I have had similar but not as bad issues with my balanced card. I noticed there is a plastic flange retaining tab on the top of amp cards just opposite the bottom metal retaining connector.  Orientated with the amp card ziff connector to your right as looking down on the unit.   This top...

I bought mine from Charleston Cable.  Christopher made my set ending in a standard 4 pin xlr and then made me a 4 pin xlr to 3.5mm TRRS pig tail.  That way I have one cable with more options. I also have a moon audio silver dragon that ends in a 3.5mm trs. Both are great cables but in balanced...

I just received a cable for HD 650 ending in balanced 4 pin XLR and an XLR to 3.5mm TRRS balanced for the HM-901.  Wow! The cable is very well built, sounds superb.   He told me the TRRS was on back order so I just assumed a week or two for arrival, nope took maybe a week to arrive.

Thanks glockhit.  I had read your posts but at the time did not understand what could be going on.  Now however I do, unfortunately. My balanced cable (4 pin to to TRRS), made by Christopher at charleston cable, arrived today.  IT does seem to be in balanced mode all the time now but even...

Thanks man, me too.  It sounds so great in balanced mode.  After messing with it all morning it does seem to be working most of the time in the proper mode. I am still going to email HiFiMan support about it though.

  I do have the balanced amp installed.  It just not stay balanced mode even with the switch in balanced mode.  It is like it slips out or my connector on the 901 has the pins in the wrong spots to make a good connection.  Once my HD650 cable arrive I will see if it does the same thing.   The...

So, I had my 901 for a few days before the balanced amp card and RE-600 Songbirds arrived.  I could not tell too much of a difference so I tested with the TRS adapter and no matter what switch position it sounded the same. I then removed the TRS adapter and messed with the switch and not...

Most of my files are M4a and play fine but for some reason my flacs from Society of Sound and HD Tracks sound better to me.   I am going to test rip a few CDs straight to flac and compare.  I have not had issues with playback though.

  I just recently bought one of these the muses edition and really like it a lot.  I did not read any bad review of the AXEO or especially the Muses edition. I am currently using it with USB on HD 650 with a cardas 20' cable and HD 580 w/600 backs and a moon audio 4' silver dragon with 3.5mm...

Oh yeah!  PS I enjoyed your video of first listen.  Pretty much my reaction is the same.  I am very happy i bought one of these DAPs.

  This is a good point here.  I noticed the 32GB cards are a lot better performers than even 64GB cards.  I had two of those and ordered two 128's so I will get used to the speed but hopefully firmware updates will improve the reading in of cards.