spritzer

The board will always output balanced regardless of the input. Not really intended for SE but you could just leave the - leg not connected for SE. We are not concerned about the distribution as that is up to the people who want to build these. I have enough boards for my own use but the Gerber's will be available to all. The parts are all in stock at Mouser so that side is covered. PSU is +/-20V.

I'll know soon enough as mine is sitting in customs.

Happy Birthday little one. How does it feel to be old?

Ahh that explains it. Bloody Krell...

After a week of battling customs, here we are: Looks kinda cute... That's the PSU above it and it needs a 12V/2A brick to power it all. Just need to figure out the loading for the output tubes but I'm leaning towards 30K for the Anode and 280R for the cathode.

Well I haven't done anything on that small one for months... Too much crap going on and currently thinking too much about DHT's... Ohh and my Tiny Triode amp PCB's just arrived for some true miniature fun.

It should be between 180-200mV if I remember correctly.

Happy to help.

The T1 bias supply is just a voltage doubler with a divider. Just set it to 500V and with a 10M ballast resistor and you'll be fine.

Some may have them in stock still but they are officially phased out by Stax.

I've got my old 507 here now and been doing some comparisons against the 207. Very different headphones and even the sensitivity is different which makes direct comparisons difficult off the BHSE with two Pro outputs. Still nothing that the SPL meter and some test tones can't deal with. The 507 clearly has more bass, I''d even say far too much, of the two. It really dominates the sound in the same way that annoying *thwack* of the LCD's does. The 207 is far leaner and more down to earth. It can raise hell if needed but it's always a bit muted. Still I'll always side with restraint over exaggeration. The midrange has always been the Lambda's strong suit and these are no exception but the 507 lacks here because the bass is so overbearing. Give it any excuse to get out of control and there goes the midrange. The top end of the 507 is similar to the 009 as in it has a bite to it that isn't supposed to be there. This gives instruments/voices a "sheen" that is quite annoying to these ears. The 207 has a bit of this when pushed hard but at normal levels they are quite smooth. Not up to the Nova Series standard but they do ok. In terms of detail retrieval the 507 seems like it is superior but it really is just like the 009, abound with apparent detail. The 207 is just as good but it's just more laid back about presenting the information. As for comfort, it is pretty much a tie as the 207 headband is better but the leather earpads of the 507 win out over the pleather. Now the easy solution would be to just order some leather pads for the 207 but how much that changes the sound is not known. Both pads have similar height so protruding ears will be a problem.

The mounting is not as nice, that for sure. One odd thing, I've ordered a lot of the larger 2.5" sinks and some have shown up with the cutouts while others have just had one mounting hole. Same Mouser number... *Calling Steve to the local Krell thread.... Steve to the Krell thread....*

The drivers are sealed on both sides so it shouldn't be a problem.

The amp will be US spec and have the right adapter. The amp will work just fine with any of the Lambdas. The bass is a bit loose and you need to push the volume a bit to make it spring to life but it's not bad for something so small.

So I'm the only one using the 2.5" sinks? They fit the chassis so why not... I got my panels back from the laser but the guy destroyed the front panel (don't ask). So I'll either have to use the back which is the suck in terms of finish or steal a fresh one from my stock and get a replacement sent with the next order.

...and a defibrillator.

I'm really opposed to eating paper so I shy away from Mc D. It was a happy day when they closed here. Says something about the food that neither Mc. D or Burger King have survived here when we are obsessed with fast food.

I'll see about having them side by side over the weekend and do some direct comparisons.

Twice the voltage would help as it offsets the natural cable loss. Mics also follow the same basic line as cartridges so more voltage means more problems. Nothing that can't be over come though but most are also balanced as in there are just two conductors for the signal. I do agree with Tyll that some balanced amps make no sense at all and could never surpass a properly done SE unit. People want tube amps for the "tube" sound and running a quad of single amps will not give you that. Working on the Stax side also spoils as those are true balanced amps where the channels are linked internally and there is no individual drift between the two outputs. I really like the idea to use Susy on these newer SS amps as it just improves their performance so perhaps it is time to do something similar to a tube amp... As for going off topic, isn't that what we always do?

They certainly have some comfort issues for me. The pads are indeed too thin and the material is a bit clammy. My head is gigantic though with them at max extension...

Well the common mode rejection applies with no ground as well. It's the difference between the two conductors that matters so any interference will be applied in equal amounts to both conductors and thus cancelled out.

Inductors would certainly be possible and one could pot them all in one piece.

Stax did change the earpads when they moved over to the cloth dust cover so they are thinner now, too thin IMO. Still the leather pads are the worst of the bunch so the normal black pads are a bit better. I just asked my friend to borrow my old 507's so I can do a comparison off the same amp. I do know that the 207 trumps the 507 to these ears but it's nice to know just how much of a difference there is.

For balanced signal transmission you don't need ground, it's just the difference between the "+" and the "-" (remember this is AC so not actually + and -) that matters. The ground is there as a shield but that's it. For balanced transducers this is more complicated or rather, the signal transmission is mixed in so that pretty much anything with a XLR socket is balanced. Take something like a spud amp for instance. It has one triode per channel so only one phase could be amplified but with input and output transformers that are center tapped it can have balanced input and output. Now the question, is it really balanced and do you get the same benefits as with something like the SuSy Dynahi? I'd like to see some better separation of this but I doubt it could be done and I doubt the noobs would understand even a tiny bit of it. This is also why I want to make an electrostatic spud amp as they have to be balanced to function...

It will always be a huge compromise, no matter how one tries to spin it. No magic to it really though, just switchable secondaries on the output transformers. Use relays to leave the secondary open and take the ESP signal directly off the tube plates through caps and for dynamics you just engage the secondary.