[Victor Chew]

What kind of transformer do you think will drive it Spritzer? Will it still be a push pull and uping of the ratios?

 

[spritzer]

That 200V figure is from TakeT so you are running the phones out of spec and might damage them. There are parts inside the phones which aren't designed to handle more then 200-250v and overdriving them isn't a good idea.

Volume is also the easy part but like you say, the bass is the problem and that's where current, a lot of it in fact, comes to play. You should find some cheap but large OPT's and wire them up backwards and see what happens.

Quote:

Originally Posted by Victor Chew /img/forum/go_quote.gif What kind of transformer do you think will drive it Spritzer? Will it still be a push pull and uping of the ratios?

It's been a while since I looked at the T2 internals but IIRC you can run them either SE or push/pull. They would need a lower ratio then Stax.

 

[b0dhi]

I'm trying to move away from transformer coupling for a lot of reasons. I'll be building a direct drive amp for them soon (assuming the stuctural mods don't go awry and ruin them). The simulations indicate it should drive the H2 very well, and it won't cost more than $1000. Hopefully it works out so we can finally see what these babies are capable of.

 

[spritzer]

I've been trying to get Duggeh to build a BH or even get the community to do it for him but no joy.

 

[Duggeh]

Curiously and unexpectedly. I actually find myself in a position to afford a full lot of BH parts including casework. However it's far beyond my still very simple electronics skill zone. One day far from now perhaps. The O2 and the TakeT remain my favourite headphones.

I've just remembered I've done nothing about that F5 Birgir. I'll put it in a box tomorrow.

 

[b0dhi]

I've been doing some mods to mine and thought I'd share in case anybody else is still interested in these.

First thing I did is ripped out all the circuitry inside. These consisted of a thermal protector (in the signal path...) and a resistor network. The resistor network basically kept current in check and also attenuated the signal reaching each of the speakers.

The H2 are actually 3-way headphones.

The strip down the middle is the super-tweeter. I have no idea how high these things go but I suspect they go well beyond 100Khz. The narrow wafered section at the top is the tweeter/midrange, which goes from roughly 4khz to beyond 20khz. The woofer takes up most of the room, and is the deeper set of wafers on the lower majority of the headphone unit. The bandwidth of this depends on the series resistance you use with it. The woofer itself is basically a 55nF capacitor.

So, I removed the super-tweeter and removed the cabling for the tweeter/midrange, thus disabling it. I use a 15R (5W) in series with the woofer, and surprisingly I get the full audio bandwidth. It definitely goes up to my limit of hearing without significant attenuation, which is 17Khz. I shudder to think how high that super-tweeter goes.

So now I can hook it up directly to my crappy speaker amp which puts out about 45Vpp and get a pretty decent volume.

I'm also in the process of doing some structural mods to it, since piezo drivers need a rigid support to work at their best, and plastic (especially the kind of low elastic modulus plastic used in the H2) is not it. So far I've added steel supports to each wafer of the woofers:





I'm now in the process of re-inforcing the sides of the unit with steel.

As to the sound, I don't want to say too much before the mods are complete, but I did some testing after installing the rods to make sure everything was ok, and found it hard to stop listening hours later. There are a lot of changes to the sound compared to the original, but I'm trying to suspend judgement until it's all finished.

I think a balanced beta22 putting out about 90Vpp could drive these to a fairly high volume and do so exceedingly well. Any b22 owners want to volunteer their ears?

 

[MDR30]

World's best a couple of years ago - what happened to the TakeT piezo-Heill monster?

 

[MDR30]

See above post.

 

[MDR30]

Must be some owners left out there from the famous group buy?