Headphones
- Thread starter TexasRugger
- Start date
The output impedance on the amp is 120 ohms so I am wondering is this amp would pair well with the DT 48 E which has a nominal source impedance of 120 ohms although the nominal impedance is rated at 200 ohms. I am just looking to see which headphones have specs best suited to work with the crack.
Crack OTL headphone amp.
Designed to optimize performance of high end, high impedance headphones.
Wonderful!
Sennheiser HD595 with 50 ohm rating not considered a good match.
Durn it.
So what!?!
Crack makes the 595 sound great.
Works surprisingly well with low impedance cans.
Still plan to stimulate the German headphone market.
Total number of Bottlehead powered tubes in system; 13
Oh, no!
-Joe Sengl
Designed to optimize performance of high end, high impedance headphones.
Wonderful!
Sennheiser HD595 with 50 ohm rating not considered a good match.
Durn it.
So what!?!
Crack makes the 595 sound great.
Works surprisingly well with low impedance cans.
Still plan to stimulate the German headphone market.
Total number of Bottlehead powered tubes in system; 13
Oh, no!
-Joe Sengl
Hello Joe,
You can also fudge the low impedance factor by using a bigger coupling cap at the output. The stock cap will give you a -3db point at around 20hz, going to 300uf will drop that dramatically!
EDIT: these numbers are with 50 ohm cans.
You can also fudge the low impedance factor by using a bigger coupling cap at the output. The stock cap will give you a -3db point at around 20hz, going to 300uf will drop that dramatically!
EDIT: these numbers are with 50 ohm cans.
Dyna Saur
New member
Completed my Crack today, and it sounds great! I "modded" it by setting up the input stage for 6CG7, rather than the stock 12AU7, just a matter of wiring to filament pins 4 and 5 and leaving 9 open.
I have a couple of RCA cleartop 6CG7s that were just beggin' to get used ;-)
No problems, no "hitches" everything came up working perfectly. No audible hum or buzz at all, it is so quiet, that at first, I thought something was wrong.
Painted the chassis plate and tranny top bell metalflake bronze, which I've used on some other amp projects, and it looks pretty good. I'll have to finish the wood base with a "complememtary" color.
It sounds fantastic with the Sennheiser HD600s.
/ed B in NC
I have a couple of RCA cleartop 6CG7s that were just beggin' to get used ;-)
No problems, no "hitches" everything came up working perfectly. No audible hum or buzz at all, it is so quiet, that at first, I thought something was wrong.
Painted the chassis plate and tranny top bell metalflake bronze, which I've used on some other amp projects, and it looks pretty good. I'll have to finish the wood base with a "complememtary" color.
It sounds fantastic with the Sennheiser HD600s.
/ed B in NC
The 6CG7 vs 12AU7 seems to be a matter of personal taste. IMO the 6CG7 and 6SN7 are pretty close, with the SN7 taking an edge when you get the more exotic types. Personally I would go for the E80CC or a 5687, but the 5687 needs a little more than pinout adjustments.
Caucasian Blackplate said:
Other than a slightly higher heater current draw, is the E80CC a drop-in replacement for the 12AU7/5963? They're sort of pricey - if I can find a (relatively) cheap one, I might bite, but otherwise, the 5963 tube I have in there now is supposedly a well-regarded 12AU7 variant anyway....
The Crack is so clear with my Beyers that I actually may stand a chance of hearing the difference between various driver tubes!
I've always been given to understand that the 6CG7 is the hip, new 9-pin miniature version of the 6SN7. Literally. Then, I believe it was the 6FQ7 that got mixed in there somehow, resulting in one of those dual-designation tubes that doesn't quite equate to either of its parents, but is close enough to both to work for most applications.
I'm not sure I've ever seen a plain, old 6CG7 without the /6FQ7 tag-along; if I have, it has been a very, very long time!
I'm not sure I've ever seen a plain, old 6CG7 without the /6FQ7 tag-along; if I have, it has been a very, very long time!
The 6FQ7 is "supposed" to be a 6CG7 with no internal shield. Of course, I have 6FQ7's with shields, and 6CG7's without, so the whole distinction kind of became meaningless.
The E80CC is indeed a very expensive tube. Consider, however, that the lifetime is probably in excess of 50,000 hours for such a tube run conservatively, and the price start to seem a little more reasonable.
The E80CC is indeed a very expensive tube. Consider, however, that the lifetime is probably in excess of 50,000 hours for such a tube run conservatively, and the price start to seem a little more reasonable.
I've been spending the majority of my listening with a Tungsram E80cc with a Sylvania 6080wb and I'm really enjoying that pairing. The Tungsram was a little on the clinical side with a Tung-sol graphite plate but it's more to my tastes with the Sylvania.
As always, this is really subject to sources, headphones and personal likes. I'm thinking this will be the tube set I'll take to the big Headfi meet in a few weeks.
As always, this is really subject to sources, headphones and personal likes. I'm thinking this will be the tube set I'll take to the big Headfi meet in a few weeks.
Dyna Saur
New member
6CG7 vs 12AU7, more of a matter of personal taste than any sound technical reasoning. Previously I modded an FPIII to use 6SN7s, and I liked the result, so this was, in a way, a follow-on to that. 6CG7 is pretty close to 6SN7, though the total plate dissipation rating is somewhat lower.
FWIW, I tried (just for the halibut) an 8CG7 in the driver's slot, and it worked, though at slightly lower gain, and it took about a minute to warm up. Back to 6V tubes... I may try a 6GU7 next, as this is the 6V version of 12BH7, and is 6CG7 pin-compatible.
From observation of my old tube stash, the older US made 6CG7s and 8CG7s generally have the larger ribbed gray or black plates (and some are RCA cleartops), and the 6CG7/6FQ7s (those I have are Japanese Raytheon) generally have the smaller "tighter" plates. So far I haven't been able to hear any noticeable sonic differences. I'll have to check other manufacturers' tubes, besides RCA and Raytheon.
As stated earlier, some have pin 9 conected to an internal shield, and others don't. For now I leave pin 9 open, rather than grounded.
Of course, I can't ever leave anything as original, so I bypassed the two 100 uF caps with some Auricap 0.68 uF / 400V, and connected a 10 uF 400V film cap across the last PSU electrolytic. There seems to be a slight improvement in the upper octave's response, but this may be as much of a "placebo effect" as an actual improvement, this is yet TBD...
/ed B
FWIW, I tried (just for the halibut) an 8CG7 in the driver's slot, and it worked, though at slightly lower gain, and it took about a minute to warm up. Back to 6V tubes... I may try a 6GU7 next, as this is the 6V version of 12BH7, and is 6CG7 pin-compatible.
From observation of my old tube stash, the older US made 6CG7s and 8CG7s generally have the larger ribbed gray or black plates (and some are RCA cleartops), and the 6CG7/6FQ7s (those I have are Japanese Raytheon) generally have the smaller "tighter" plates. So far I haven't been able to hear any noticeable sonic differences. I'll have to check other manufacturers' tubes, besides RCA and Raytheon.
As stated earlier, some have pin 9 conected to an internal shield, and others don't. For now I leave pin 9 open, rather than grounded.
Of course, I can't ever leave anything as original, so I bypassed the two 100 uF caps with some Auricap 0.68 uF / 400V, and connected a 10 uF 400V film cap across the last PSU electrolytic. There seems to be a slight improvement in the upper octave's response, but this may be as much of a "placebo effect" as an actual improvement, this is yet TBD...
/ed B
That seems like a pretty small valued bypass cap to have much effect on the sound. I could be wrong and if you had those caps on hand,.. what's the harm?
I'm pleasantly surprised how good the Panasonics sound. I do have a couple of 10uF Auricaps and a couple of 1uF Dynamicaps rolling around here someplace that I might try once I get a firm handle on the way this amps sounds stock.
I guess I'm just in the "enjoy it" stage right now. And since I don't have much experience with 6080s and the like, I'm pretty happy to just be tube rolling right now.
I'm pleasantly surprised how good the Panasonics sound. I do have a couple of 10uF Auricaps and a couple of 1uF Dynamicaps rolling around here someplace that I might try once I get a firm handle on the way this amps sounds stock.
I guess I'm just in the "enjoy it" stage right now. And since I don't have much experience with 6080s and the like, I'm pretty happy to just be tube rolling right now.
Dyna Saur
New member
The 0.68 uF Auricaps were some I had on hand, leftovers from a J.R. Broskie "Aikido" project.
I figured they only had to work above 5KHz or so, so the relatively small value should be sufficient.
Ditto for the 10 uF film cap, I have "boatloads" of them, found at a NEAR-fest (NH Hamfest) a few years ago. The 100uF caps are amazingly good sounding by themselves, much better than I would have expected, or have experienced with lesser, cheaper caps.
Like I said, the perceived HF effects may be more "placebo" than tangible...
Next is to try rolling in my various 6080s, 6AS7Gs and 5998As. One thing at a time...
/ed B
I figured they only had to work above 5KHz or so, so the relatively small value should be sufficient.
Ditto for the 10 uF film cap, I have "boatloads" of them, found at a NEAR-fest (NH Hamfest) a few years ago. The 100uF caps are amazingly good sounding by themselves, much better than I would have expected, or have experienced with lesser, cheaper caps.
Like I said, the perceived HF effects may be more "placebo" than tangible...
Next is to try rolling in my various 6080s, 6AS7Gs and 5998As. One thing at a time...
/ed B
Truth is the 100uF 'lytic coupling caps were what I was most concerned about when we decided to do this. I figured everyone would just have to "chuck them in the trash and buy a good cap", as we couldn't include 100uF film caps and keep the price anywhere remotely near where I wanted it to be. But in fact I don't hear a huge difference between the stock Panasonic 'lytic caps and the Dayton film caps we recommend for folks who eant to switch to film. Those Panasonics are a really solid value. I will however forewarn folks that at this ridiculous price point we may have to change to different brands from time to time as our suppliers fall into back order situations. We've sold about three times as many Cracks as I expected by this time, and keeping up the delivery pace means we have to stay flexible about parts sources. So you might see a Nichicon or a C-D here and there - or maybe even the new EPCOS caps that Mouser is stocking. Right now I think we are shipping with Pannys for the coupling caps and maybe Nichicons in the power supply.
