dBel84

yes, what Nate says - let her breath , gale forces may be called for ..dB

talk about a big hairy monster - that is one beast. Did you by any chance hook he HD800s up to the EHHA - i suspect this union to be nothing short of a revelation..dB

no questioning that then ..dB

well that will give you 104mA per mosfet = 208mA per board . There is about 10mA in the VAS stage and about another 4mA in the mirror ( I allowed 20mA all in for good measure ) So in theory , your amp should be drawing about 230mA per board ( unless I am missing something here ) How did you measure current draw for your amp? The easiest way is to use a dummy load and check the voltage drop , calculating the current from that..dB

and you never invited us??? Well I was just looking at the EHHA and idling for each board ( set with a MOSFET idle current of 100mA ) will be about 220mA. I am not sure what bias your boards are set to digger but your measurements suggest that you are idling around 75mA - all within spec ..dB

the tubes have their own supply , so it is just the amp rails that need to be considered - I will go back and work it out but my suspicion is that it will not be more than 300mA per board..dB

The voice of reason I am embarrassed to say that I fell into the same trap too, just looked at the 2 amps under consideration, figured both running full tilt would draw more that the S22 heatsinks would tolerate and abandoned the idea. The truth iabout the S22 Come on Smeggy , I am sure you want to see how much moar power you can push The rethink I have not done the math but a ballpark for the EHHA pushing headphones is a max of about 1-2W ( my boards idle at a bias current of about 200mA ) , I suspect the B22 is about the same. Thus, driving headphone loads, both amps should be able to work happily with a single S22 in a well ventilated case. I was just scanning the B22 information and Ti says the following "The current draw from the β22 board is approximately 200mA per board as a headphone amplifier ... 5A peaks driving speakers" and I recall a comment about a single S22 being able to power 4 B22 in balanced mode quite comfortably. I am not sure if the on board S22 heatsinking would be adequate , we would have to do the real math for that one ..dB

and your torroid is the mutha load iirc , so it would handle both S22's without any concerns? seems the sensible thing to do then ..dB

this was my concern too, both those amps can suck good juice. Switching the rails between the 2 amps would work but you effectively lose one active amp with this configuration ( not that that was obvious at all ) . Are you averse to dropping a second S22 into the case ( is there enough room? - i don't see the torroid in there , could be stacked but still very tight and from Nates experience, the B22 can pick up noise like this ) ..dB

CJ , thought I would pick from earlier discussion. The simple SE is pretty straight forward but I am always weary of encouraging someone with little HV experience to jump in without someone around to assist in the process. I have a few questions - why DIY , it is very cool if you want to get into building things and have that ability and there is only one way to learn and that is getting your hands dirty. However, if this is to find a budget route to better hifi than is available in retail, I might suggest alternate routes. eg vintage HiFi that often gather dust and even though they have been replaced by the latest FOTM, can still offer excellent sound quality and be found at shockingly cheap prices ( also crazy money at times ) check out The Vintage Knob to get an idea Other options Besides the gainclone Nate suggested which I think is a superb DIY idea Digital amps The T-amp should be able to drive the fostex and be a good entry point read this 6 moons review I listened to the Two Bald Guys system at VSAC and nothing too shabby about it. BUT not DIY - 41Hz will satisfy that lust As for tubes , the EL84 based zen amp you originally linked to was rated as being very good value with a decent enough sound but again it is high voltage. One way to get a tube fix is to consider a Hybrid - Moskido would offer excellent value but I would recommend using the 24V version and running in front of a simple gainclone , this would give you a superb headphone amp / line stage as well as enough power to drive the speakers. ( the integrated concept that yu mentioned ) - not sure if this could be squeezed in under your budget but possibly. Many other options which is part of the problem when it comes to DIY and the (in)ability to stop building after you have completed the project. ..dB

would you ever want them running at the same time? ..dB

yes , you could load both sides of a differential amp, make sure you used a 4 pin xlr so that the headphones are driven balanced , you could probably just attenuate one side as the amp would see the same resistance of HP + resistor ( my anal symmetry freak side would want to put 1/2 R on each leg but that is my own nightmare ) . Out of all the soultions, I like the transformer matching box the most ..dB

I chose a load that my amp would be happy with, 8 ohm seemed about right. Any additional resistance in parallel is going to be negligible. I wanted to attenuate the signal and 100 R seemed a good starting point and I had them sitting in my parts bin. This was not a scientific process by any means but rather a scrounge through the parts bin to see what was available and what I could make work. I am sure this has been mentioned in this thread but just a reminder not to try this with differential output amps ( ie bridged output ) - in other words , no amp that doesn't use a common ground for the output stage. ..dB

I have built a simple version which uses an 8 ohm 5+W resistor to load the amp and a 100R in series with the headphones Rod Elliot has a more thorough approach to balance power supply and impedance. ..dB

looks like a GU 6M series - 6A rated at 700V for a 1000V rev voltage limit. ps sorry to hear this went down Al, hopefully it will allow some reverse engineering to enable future repairs. ( gotta look at the bright side .. dumdedum...) ..dB

iirc that is where NoNoNoNoNoNo has his EHHA set and he is enjoying the ID2's immensely. I suspect the ID1's are similarly inefficient if not more and enjoy the power that these amps have to offer..dB

not sure how to follow these comments without images of sagging spandex glad to hear you got this sorted smeggy ..dB

aaah CJ looked like an incredible event, congrats JP Not dead just resting ........ I won't let it go away did you get a chance to listen to it Nate? @Frihed89 , afraid I can't answer your question specifically as I don't have an SP amp to directly compare but one of its strengths is resolving detail. ..dB

just a follow up , I will have to get him to sign up here too ..dB

what did i miss?? ..dB

You would probably like some of the clamps I stumbled on and discounted for their price tag. The THORlabs optical brackets were particularly cool. These are the other type of plate mountings 1 2 3 ..dB

good to hear ..dB

aaaah no - I was assuming octal = I should know never to assume , this is most likely a loctal converter , I will give myself a ..dB edit - it does look pretty sweeet ( i had forgotten just how cool it turned out )

Or ask for free prototypers - nothing would have given the orthoheads more pleasure than to be involved and there is vast experience just waiting to be tapped ..dB

Anyone know what these octal tube extenders are ? am also VERY curious if anyone else got round to spending some time with it at CJ - all those pics of the gear make me think that most folk were a little overwhelmed ..dB