[vcoheda]

Roam:

the Raptor is a pretty popular and well regarded amp. Ray must be doing something right. is it possible that the design is not optimal but still sufficient. i mean i haven't heard anyone complain about one or report any failures. i don't question your credentials but these are audio amps, not nasa rockets.

do you hold single power amps in a similar low regard?

 

[Hi-Finthen]

Quote:

Originally Posted by Roam /img/forum/go_quote.gif Forget about the Raptor, 5687 tubes in an OTL configuration will never come anywhere close to driving an RS-1 to its full potential, and that's not to mention the countless design flaws, defects and shortcuts in the Raptor which are so numerous they'd fill a small phonebook. Personally I feel anything short of a Moon Audio Luna or EC Zana Deux would be shortchanging the RS-1. The RS-1 will still sound quite pleasant out of lesser amps, however, a lot of its potential will never be realized. My recommendation would be the Moon Audio Luna, which not only sounds good, in a rarity for high-end audio it also follows solid design & engineering practices. Very good resolution, liquid effortless sound, never crosses over into harshness unless one sticks a crappy Sovtek 6DJ8/6922 on the input; it's what good tube sound should be. One warning though, do not expect to be impressed by the amp on first listen. It's not a "wow" amp, there's nothing which will really step out and grab you; no overly exaggerated midrange bloom, no emphasized leading edges, no flashy highs, nothing like that. Rather, it's an amp which will grow on you, as you go through you music you'll start hearing new things in new ways, and that's when you'll start realizing how good it is. All those transformers also take a long time to break in and sound their best, give it a good week or so of solid play for best results. Use the cheap tubes during this time so you don't burn hours off your good 6DJ8/6922 tubes.

The EC Zana Deux is said to be mid-fi by certain owners here, but at some point we all settle in with what we accept as the amps limitations if it sounds good to us. I mean other than fanboys of course...

 

[Roam]

Quote:

Originally Posted by Negatron /img/forum/go_quote.gif I can't speak for the Raptor but I have to stick up for one of my more favorite tubes. The 5687 with the prober plate load (and that is a narrow window) can, with proper bias drive 32 ohms with voltage and curent to spare configured as an White Cathode Follower OTL. Several other configurations are also possibe to achieve the same results. Don't hurt the feelings of an innocent tube.

Voltage, current, low output impedance, pick two. Aim to minimize output impedance and voltage headroom disappears. If you want good voltage swing the output impedance rises and current capability falls a bit. The best one can hope for is an output impedance of around 20-25 Ohms with decent voltage & current swing. For Grados, the output Z is still too high.

The 5687 is a great tube, just like a Porsche is a great car. The problem is application, the 5687 isn't any more suited for driving low impedance loads than a Porsche is for pulling a tractor. Sure it can be done, but there are other tubes & vehicles which will do a far better job.

 

[Negatron]

Quote:

Originally Posted by Roam /img/forum/go_quote.gif Voltage, current, low output impedance, pick two. Aim to minimize output impedance and voltage headroom disappears. If you want good voltage swing the output impedance rises and current capability falls a bit. The best one can hope for is an output impedance of around 20-25 Ohms with decent voltage & current swing. For Grados, the output Z is still too high. The 5687 is a great tube, just like a Porsche is a great car. The problem is application, the 5687 isn't any more suited for driving low impedance loads than a Porsche is for pulling a tractor. Sure it can be done, but there are other tubes & vehicles which will do a far better job.

20 ohms is about right. Output at 4v RMS with a couple of volts to spare and yeh, I know that isn't a great deal of headroom, but with 500mW 2nd harmonic is at about 55.0mV and 3rd a tenth of that. But I find distortion specs an indicator not a law.

The tube isn't strained there, it's airy, open and tight way down. It, and it's Russian semi-clone are a great little OTL tube. I do tend to use old 6V6 and EL84 power transformers though.

I've never heard a Raptor but I have heard some very fine and accurate amps in my day that didn't look so good on paper. Many times it's about synergy of component and tireless voicing to the point of insanity. A lot of fine cooks threw out the book long ago.

 

[J-Pak]

Isn't the output impedance on the PPX3-SLAM supposed to be fairly high as well?

 

[shplorgh]

Quote:

Originally Posted by Hi-Finthen /img/forum/go_quote.gif The EC Zana Deux is said to be mid-fi by certain owners here, but at some point we all settle in with what we accept as the amps limitations if it sounds good to us. I mean other than fanboys of course...

Who says that?

 

[Redo]

Quote:

Originally Posted by hungrych /img/forum/go_quote.gif Who says that?

Not me!!!

 

[Hi-Finthen]

Quote:

Originally Posted by hungrych /img/forum/go_quote.gif Who says that?

granodemostasa: In the thread by Member Hellenback Here: http://www.head-fi.org/forums/showth...03#post3187003


Question: When does sound become High-FI?

Answer: "actually, I think it's about 4000-6000$ when that happens. (I'm still not there yet)"

Point being, for the OP, he very well maybe satisfied, as are many with the Mapletree I suggested, rather than as Roam had said, anything less than a EC Z.D. would be less than blah blah blah...

 

[shplorgh]

Nowhere does he say that the Zana Deux is mid-fi.

If you want to go the diy or commisioned diy route, you could wait a little bit for the aikido headphone amp kit, or even do a balanced one. I'm probably going to do that for my RS-1, I'll try to report on it if I ever do.

 

[coinup]

Quote:

Originally Posted by Roam /img/forum/go_quote.gif The most obvious flaw is the shared ground between the high voltage B+ and the low voltage filament supply. This will couple the noise from the switchmode PSU used for the latter into the nicely regulated B+, and introduce RF noise into the tubes. Next, the switchmode PSU is underpowered, 3.4A sounds like a lot compared to the nominal filament draw of 1.05A, however, this neglects the inrush seen when the filaments are cold. Cold filaments will often use up to 5-10 times as much power as their nominal rating until they warm up. Every time the amp is turned on, the filament heater supply is stressed beyond its rated specs, over a period of time its filter capacitors are guaranteed to fail from the abuse. While we're still on the power supply, the high voltage B+ is also under-spec'd, and likely being run close to or aboved its rated limits. The toroidal transformer used is about a 25W unit, Plitron cannot defy the laws of physics and make a 50W transformer that's the size of a 25W one. The size of a transformer places an upper limit on its power rating. With that out of the way, let's assume the tubes are being run at about 80% of maximum, which is typical of audio designs, this would give a figure of around 17.8W being dissipated at the plates. Next, we look at the PSU itself, the heatsinking on the regulator would imply at least 5W of heat dissipation, and the size & mounting of the resistors a further 1-3W apiece. This gives a lower limit of 26.84W and an upper bound of 35W or so. Best case, the transformer is marginally over its limits, worst case, its limits have been exceeded by a whopping 40%. And finally we come to the circuit, yes I do have the schematic. The output impedance is at best around 32 Ohms, no, that is not a typo, it is 32 Ohms. The plate load for the 12AU7 is also too low, for best results it should be about 25-40% higher. Which brings me to my next point, why even bother with a 12AU7 as the gain tube? It's one of the most non-linear tubes used in audio, 6DJ8s, 6SN7s, 12AY7s, and many others all measure and sound a lot better. A 12AU7 is acceptable in a cathodyne phase-splitter where the copious NFB and lack of gain will take care of most of its shortfalls, but as a gain tube it's miserable. I could go on & on since I haven't even scratched the surface, but frankly I feel we all have better things to do with our time.

what would you go for??