Thanks for all the orders!
- Thread starter Doc B
- Start date
Grainger49
New member
Now that, is addictive!
As I mentioned in another thread, even after we have doubled production we have only seven kits left available as of this afternoon. There will be some lag before we have a second production run complete, so order soon if you want a kit from this first run.
http://www.bottlehead.com/store.php?crn=44&rn=442&action=show_detail
http://www.bottlehead.com/store.php?crn=44&rn=442&action=show_detail
The first run sold out a bit after midnight. We have initiated a second production run, and it will probably ship two to three weeks after the first run. We hope to begin shipping the first run around the first or second week of April. We have been selling several kits each day and it looks like this kit will continue to move pretty quickly so I would suggest getting in on the second run early if you plan to order.
lextek said:
Yes, there are ways to make this amp run well with Grados. If you increase the current in the 6080, the output impedance will decrease. Along with this, the 100uf output coupling caps would need to be at least doubled to attain acceptable low frequency response.
The upgrade path we will offer with the kit will optimize it for use with 100+ ohm headphones, as 250+uf film capacitors are pretty tough to find, expensive, and physically huge. I would mention, however, that there will be some ways to modify the upgrade package, but I can't disclose much on that until the upgrade package is complete.
Caucasian Blackplate said:
This makes me wonder about another set of cans with "low" impedance, the AKG K-701/2. I think their rated impedance is something like 62 ohms, so they're not quite as bad as the Grados. I'm still debating between these and Sennheiser HD600/650's, and placed an order for the Crack amp the day it was released, so I want to find a replacement for my Beyers that will work equally well with the Crack and S.E.X. amps. The S.E.X. will have no problem driving anything, but OTL is a different story. In the case of the AKG's, is the impedance high enough where one could simply substitute a 5998 for the 6AS7/6080 in the Crack amp and be fine? If the 6AS7 nets a Z-out of 100 or 120 ohms, I would think the 5998 would get you about a 60 or 70 ohm output impedance, right?
Paul Joppa
Moderator
For low impedance headphones, there are two considerations - how much current they need, and whether they are tolerant of the standard 120-ohm source impedance.
The AKG701 is specified at 105dB for 1 volt input - relatively insensitive. The required current for 102dB would be about 16mA peak. Its impedance (from the Stereophile review) is quite flat below 10kHz, so it will not be very sensitive to source impedance - no special precautions needed. With a low drive impedance, the inductive rise of the phones above 10kHz might drop the response a few dB at 20kHz. If they seem bright in the highest octave, a lower drive impedance might help a bit, but otherwise I'd say they are well suited for the standard source impedance.
I am working on a white paper on headphone impedance matching focussed on Bottlehead applications, but it won't say much more than what is on the head-wize site. Some good stuff there!
The AKG701 is specified at 105dB for 1 volt input - relatively insensitive. The required current for 102dB would be about 16mA peak. Its impedance (from the Stereophile review) is quite flat below 10kHz, so it will not be very sensitive to source impedance - no special precautions needed. With a low drive impedance, the inductive rise of the phones above 10kHz might drop the response a few dB at 20kHz. If they seem bright in the highest octave, a lower drive impedance might help a bit, but otherwise I'd say they are well suited for the standard source impedance.
I am working on a white paper on headphone impedance matching focussed on Bottlehead applications, but it won't say much more than what is on the head-wize site. Some good stuff there!
I can save you the trouble, get the HD-600's. Having owned both the HD-600, and the K-701, the HD-600 is an easy choice for most listeners. The K-701 does shine pretty well on the SEX amp, but the HD-600 is still preferable IMO.
