SEX & the Hifiman

[Todd R]

Just wanted to let everyone know the SEX 2.1 is working out great driving the Hifiman HE-500 phones.
Plenty of power and killer sound.
I'll be retiring my HD-650's now. Never thought that would happen.

[SilverS]

Congratulations!

[Raksasa]

Just wanted to let everyone know the SEX 2.1 is working out great driving the Hifiman HE-500 phones.
Plenty of power and killer sound.

Aww, that's awesome news.  (https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi204.photobucket.com%2Falbums%2Fbb272%2Fraksasajohn%2FSmilies%2Fthumbzup.gif&hash=1da0f9a591a720f4cb896f78b18d225e8cb6b4c8)

Lookin' for a tube amp for HE-500s.

Cheers,

John T

[Raksasa]

Whoops, just saw no 240v yet on product page.  (https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi204.photobucket.com%2Falbums%2Fbb272%2Fraksasajohn%2FSmilies%2Fcry_1.gif&hash=7a84ee03e0bbef2bdbbfc19affb87b714a5eb3dd)
Coming later, tho.

And output impedance switching coming too.  (https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi204.photobucket.com%2Falbums%2Fbb272%2Fraksasajohn%2FSmilies%2Fhmm_smiley.gif&hash=1e0e22c5fdbbea4ed3e0af320bb5871a51d931fb)

Will keep an eye out.  (https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi204.photobucket.com%2Falbums%2Fbb272%2Fraksasajohn%2FSmilies%2F2cool.gif&hash=cc52bdf2a988551ffc51b21cde5d82912a843487)

[Todd R]

Yep,
Works pretty good.
I have not got it to clip, but I have ran out of gain on the rare occasion depending on the overall level of the music that happens to be playing. We should be able to adjust that, right Doc?

[Doc B.]

I'll presume you have it wired for 32 ohms output impedance? If not, that will give you the most gain from the amp. Beyond that there isn't a lot more you can do in the amp to increase the gain. Best bet would be boosting the level of your source by putting another gain stage ahead of the amp, i.e., a preamp. Without having tried them it's difficult to say for certain if the increased signal level will sound clean or if the headphones are simply too inefficient to be driven by the S.E.X. and it will be driven into clipping. But I think it would be worth the experiment if you have a preamp available to try out.

[Todd R]

Doc,
Yes I'm wired for 32 ohm.
It's a rare problem, maybe 10% of the time and really it's a problem with how loud the music is recorded more than anything else.
Don't have the schematic in front of me right now, but was just pondering if there might have been a resistor that I could change or something.

If not, no biggie. Wife always tells me l I listen too loud anyway :-)

I have a pre-amp I can try with and will let you know.

[Beefy]

Don't have the schematic in front of me right now, but was just pondering if there might have been a resistor that I could change or something.

If you have the 120R at the headphone jack, *definitely* remove that.

[Todd R]

Don't have the schematic in front of me right now, but was just pondering if there might have been a resistor that I could change or something.

If you have the 120R at the headphone jack, *definitely* remove that.

I would but it cuts down on the noise a lot when I use my low impedance phones.
Maybe after Doc gets the impedance switching board out I'll give that a try.

[Paul Joppa]

Beefy is right, the 120 ohm resistor is costing you more than 10dB, both sensitivity and total available power. That's how it reduces noise, it just attenuates everything at the output (with low-impedance phones).

I take it you also use high sensitivity low impedance phones as well as the [low sensitivity] HE-500s, which is why you want to retain that reduction in output level. You might consider putting the 120 ohms in the more sensitive phones' plug, or making an adapter plug/jack set like the one with a right angle plug shown in another recent thread.

[Todd R]

Beefy is right, the 120 ohm resistor is costing you more than 10dB, both sensitivity and total available power. That's how it reduces noise, it just attenuates everything at the output (with low-impedance phones).

I take it you also use high sensitivity low impedance phones as well as the [low sensitivity] HE-500s, which is why you want to retain that reduction in output level. You might consider putting the 120 ohms in the more sensitive phones' plug, or making an adapter plug/jack set like the one with a right angle plug shown in another recent thread.

Ah! Brilliant.
I needed to make an extension cord anyway.
BTW...
Any word on those impedance boards? If I making cords I'd like to put a balanced capable plug on the end while I'm at it.

[Paul Joppa]

Doc B is on his way to SF for the headfi show, but I believe the manual for the impedance switch kits is drafted and just needs a final edit before the kits can go out.

[Todd R]

Doc B is on his way to SF for the headfi show, but I believe the manual for the impedance switch kits is drafted and just needs a final edit before the kits can go out.

Great news. Sign me up for one.
How about the C4S kit for the 2.1? About ready also?

[Paul Joppa]

I could be wrong about which is coming when, but I know Doc and Shawn have been working like crazy, building and photographing, and Josh is putting manuals together. IIRC, we have:

* install v2.1 transformers in v2.0 SEX

* install latest C4S in v2.1

* install latest C4s in v2.0

* install switch board in v2.1

* install switch board in v2.0 which has been upgraded with v2.1 transformers

I'm not clear on which if any can be combined into a single kit and manual. And meanwhile, remember that the switching phone jack is no longer available, so the v2.1 manual needs some corrections, and the 120 ohm resistors help some phones and hinder others, so that should be documented somewhere besides just a sticky post, and is slightly different in each of the above variants. I begin to understand why Doc looks glum whenever anyone has another "improvement" idea!

[Raksasa]

Beefy is right, the 120 ohm resistor is costing you more than 10dB, both sensitivity and total available power.

Oh wow, this is looking more and more like a great amp for HE-500s (89 dB sensitivity, 38 ohm).
I was gunna go down the grunty SS path (eg Violectric V200 or Meier Audio Classic etc), but I lurve vacuum bottles.

Any idea when 240v option may be available ? This year ?
Won't be buying till I have some money towards end of 2012. Plenty of time.

Cheers,

John