Amp advice on powering Raal CA-1a via the Raal TI-1b transformer box

[ipetruk]

Hi everyone,

I've got myself Raal CA-1A which I now power by Jotunheim-R, a specially designed amp that can only power Raal headphones. They drive me crazy and they are the best headphones I have ever heard. If you don't know about them, they are ribbon headphones with impedance of 0.2 Ohms (you heard it correctly, these headphones are literally "short").

As a Bottlehead fan I am thinking how to introduce my favorite amp company products and their tubiness into the chain.

Raal offers this transformer box that can be plugged to powerful headphone and speaker amps: https://raalrequisite.com/product/ti-1b/. By pretty much every account I know powering Raal from a capable amp (Ferrum Oor, Holo Bliss, Cayin) via TI-1b beats Jotunheim-R. But I wonder about Bottlehead products.

Raal page says:

Our general recommendation is a conventional headphone amp having from 2 to 6 Watts at 32 Ohms, but we’ve been pleasantly surprised with amps as low as 0.5 Watts when the sound is right. Of course, if your listening requires high dynamic range or you like it loud, choose something closer to 6 Watts than 2 Watts.

I already own Mainline and Crack, but they are probably out of the question.

This puts the choice between S.E.X, Stereomour and Kaiju. I can of course read their power specs and make a call, but I guess there are more things than pure watts. Is there anything else I should know? What about the noise (CA-1A are clean & crisp beyond the wildest imagination, think STAX, Susvara)? Any pitfalls to expect from a Bottlehead amp interaction and TI-1b box? Can it be damaged by some power spikes during amp turn up, etc? Any tips and comments are welcome.

Or, maybe I should email Raal for more information, ask them for more detailed spec of some parameter you are interested in?

Thanks,
Igor.

[Doc B.]

I experimented with my own ribbon headphone design many years ago, and also used Raal tweeters for several years. Based upon that experience and the info offered by Raal I would go with a Kaiju with the DC filament upgrade. Plenty of power and very quiet.

[ipetruk]

Thank you for the quick answer.

Kaiju is a very solid choice, if I wanted the thing to work for sure... but for more money.

What about cheaper amps, S.E.X. or Stereomour? Will there be issues with clarity or power? Or both?

[Paul Birkeland]

I would second Doc's recommendation for a Kaiju.  You want as much flexibility as possible in terms of being able to wire our output transformers in various configurations to figure out what works best for you, and the SEX amp is unlikely to provide sufficient power for those experiments and the Stereomour may not be quiet enough.

It's equally likely that you'd prefer the Kaiju wired for 2 ohm (lowest noise, most immunity from the nasties of the load it's driving) or the Kaiju wired for 16 ohm (most power, more distinctive tube sound). 

[ipetruk]

Thank you!

It looks like 16 Ohm makes more sense because the transformer box literally has a special 16 Ohm input. I do trust they mean it

[Paul Birkeland]

Without hooking the headphones up to that box and doing an impedance sweep at the outputs, I would not make any assumptions about what the numbers mean that are printed on it

[Paul Joppa]

It might be worth the trouble to ask the manufacturer how flat is the impedance curve. Reading between the lines, the statement that the cable resistance dominates over the ribbon impedance suggests it might be very flat, which would remove that concern. Raal provides very little information. In fact, that would make the SEX amp a reasonable candidate - it can make 2 watts into 16 or 32 ohms resistive equally happily.