Just search for EF94 or 6AU6 https://www.ebay.co.uk/itm/2x-Fisher-EF94-6AU6-valve-tube-TESTED-GOOD/123584739018?hash=item1cc63976ca:g:JyoAAOSwCXxcM8ha:rk:2:pf:0

Yes, it will help. I just plugged into my latitude 6430 using winamp with no adjustment it sounded fine on my HD600's

Thanks for the info, i'm also looking at Oppo pm3's. I'll need to expand my budget a bit..

Hi all, i upgraded from sony mdr 1a's to HD600's and i love the sound with my setup which is PC based, Xonar STX essence card into a nobsound hybrid headphone amp. It all works great however i have discovered that the open back hd600's are not compatible with the wife. She is forever complaining...

I moved back to the amperex 6688 tubes for a while and left them to warm up. they sound smoother than the russian tubes. My ears aren't good enough to accurately describe the differences, they are all good but some are gooder than others :-) I finally moved back to the mullard nos e180f's and...

I was using Sony headphones and the cable had a 3.5mm jack at each end, i reversed it and it worked. The 6xxx use their own cable, maybe a replacement will make a difference.

You can also try different cables, from your sound source to the nob amp and if your headphone cable can be changed try that as well. Make sure the earth wire from the circuit board to the back panel is still attached. Previously with different op amps I had hiss that changed when i moved the...

Ok, I tried this track in flac format. There was a lot of left/right positioning and all the instruments were well defined. I could separate them and they didn't blur together. That said it wasn't my fav Heep song. I prefer the Salisbury album as i knew the recording studio well and heard the...

Today i received a pair of dual opamps to try from Charles at Burson Audio. They are V5i hybrid amps, a mix of discrete components and a custom integrated circuit. They are a drop in component and can replace a multitude of differing opamps. The website states that they need a 'burn in'...

At the moment NOS mullard e180f's. I have 6688's to try as well and should be getting some Russian tubes soon.

I got a pair of these to try today as well :-)

So i decided to get a pair of hd600's. Yes it was worth it. I play flat don't use eq and it's all there. Bass, mid's and high's but nothing is overpowering. A well balanced sound. I.m using the burr brown opamps with amperex 6688's with absolutely no complaints. I have a few more bits arriving...

I have just put a pair of Burr Brown OPA2134PA opamps in and they sound good with the mullard e180f's. I'm waiting for a pair of muses02's to try. If they don't work so well i can always try them in my soundcard.

no, they should all be manufactured to the same spec. I would buy 2 from the same supplier though. copy this item number into fleabay, they're the pair i got: 182581579004

I also put a pair of these in, JRC 4558D. These are inexpensive high quality op amps and they sound great.

This was just an example, the chances are if you bought 2 they'd be NOS from the same batch. A matched pair will be more expensive.

i use E180F's in mine and it sounds great(to me) ebay is a good source for these valves. http://www.ebay.co.uk/itm/Mullard-E180F-CV3998-5A-170K-pentode-/310889763205?epid=0&hash=item4862795185:g:CTMAAOxy4YdTQtGw

Thanks for the heads up, they're cheap enough to play with i wouldn't try with muses chips though..

I put a pair of 50yr old new mullard e180f's into this little box and it sounds great. I use sony mdr1 phones which are punchy on the mid to high range. They've mellowed a lot, i am going to invest in another pair of headphone, just need to find some that suit me.also i will be 'rolling' the op...