In tube amp... hiss from speaker, only if ear is close to speaker - is normal hum from speaker, faint if ear is closer to speaker - is acceptable, but usually can be tuned to almost nothing with hum pot buzz from speaker, is not acceptable - usually indicate issue with circuit, tube, transformer, or ground loop. try turn off as much other electrical equipment as you can in the house. see if that helps. the 508IA/805IA is not that sensitive to other equipment (but still possible it is definitely sensitive to ground loop. unplugging input should eliminate (reveal presense of) ground loop.
when I first got my LM805ia I had a hum that I tracked down to a ground loop between the DAC and amp. Lifted the ground on the DAC with a HumX and issue was solved.
Actually it was my preamp causing the hum issue not the DAC (haven't had my first cup of coffee yet). Lifted the ground on the preamp. When I spoke to my LM dealer he indicated that the preamp is the common culprit of ground loop hum with the LM amps.
Not a bad idea. But if I were you, I would have done comparison between two 6n9s tubes before sending one out. In theory, they shall sound same. But in reality, it is more likely that one sounds slightly better than the other.
https://photos.google.com/share/AF1...?key=VjN1SHRiUWYxUGd0dk5qWTVQOEJNNXdMaEZ0RGZB Although I already have one, I ordered one more Brimar CV1985 from Upscale Audio by mistake. Left side is one from Upscale Audio. Now I have two of them. The initial impression of Brimar CV1985 from Upscale Audio is favorable slightly less details than 6n9s but nice balance and clean treble. I will also compare those two Brimar CV1985 that I have.
Early on I tried the Brimar CV1985 from Upscale as well. I found it to be overly relaxed/warm with a closed-in, restrained sound in my system. I actually thought the stock tube in the LM sounded better. The Mullard ECC35 blows it away.
Now I remember that I had not been impressed with Brimar with Acme 805 two years ago with overly warm sound. But with RCA 805 which sound transparent but somewhat lean compared with Acme 805, I enjoy the sound out of Brimar. It seems that Brimar falls between National Union (very round and warm) and 6n9s (sweet but detailed). I will give my opinion after further listening to both Brimar 1985. Nos tubes may sound slightly different from each other even with same brand and denotation.
Admittedly I haven't used the Brimar since getting my RCA 805's so perhaps it sounds better with those than the stock 805's. However the Mullard is warm sounding tube as well but it produces more air and bigger soundstage than the Brimar so I suspect I will still prefer the Mullard over the Brimar. It's worth a try just seeing how the Brimar works with the RCA 805's so maybe I will try tomorrow.
The impressions that others have of the Brimar are far from what I experience with the one I have. Are there different versions of the same tube? Does the CV1985 version have a different sound from the 6SL7GT, which is the one I have similar to the image that @Pedro Guillemain posted. The CV1985, which is designated 6SL7GTY being described as warm is the complete opposite of what I experience with the 6SLGT(no Y) which is lean and has a tipped up high and narrow Z depth.
It seems that CV1985 version looks different from the one that Pedro bought. https://photos.google.com/share/AF1...?key=VjN1SHRiUWYxUGd0dk5qWTVQOEJNNXdMaEZ0RGZB I had done comparison between two CV1985 tubes that I have. They sounds very alike with old one giving tiny bit of more sparkle. When I had tried out CV1985 two years ago, I had used Acme 805 with EmmLab Dac2 which sounds warm an full. But with Rca 805 and Chord Dave and Mscaler which sounds more detailed, CV1985 sounds very pleasing, relaxed and musical. There is no best tube for everyone. It will depend on your system and personal taste. I will swap the 6sl7 tubes depending on my mood and music.
I've measured mine and I seem to recall that it's around 4.4 amps. As I type I can see the display of my power regenerator that my LM805 plus VAC preamp, Lampi DAC, and Lumin U1 draw a combined 5.3 amps.
Not much. I am very much enjoying the sound, esp after some other mods on my DAC. The only reservation is there is still some aggressiveness at the top end and I need to see if it can be tamed without compromising the sound in other places. This is mostly due to my speakers though. I haven't made changes under the hood of the 508IA recently as a couple of bicycling injuries on my arm and shoulder made me uncomfortable with flipping the 90lbs beast without hurting the amp or myself. Mostly just tube rolling at the moment. So in the internal modding front, I don't expect much to happen until a few more weeks.
After being back to 6n9s made in 50's, I found 6n9s to have more air and sparkle than Brimar CV 1985 although latter also sound musical with relaxed sound. It will be nice if Adamaley get them soon, so he can try them in his system. I think 6n8s and 6n 9s tubes made in 1950's are best bang for the money. It is always hit or miss to buy Nos tubes. But tube listed below looks like mine. 2pcs 6N9S MELZ / 6SL7 / 1579 TUBES Metal base 1956 NOS | eBay
Tracking information was just sent out this morning so it'll be maybe a week before I get them. They're coming from Ukraine, I think.
Kill-A-Watt monitor shows 400W power consumption regardless of how loud it plays (whis is what expected from class A design).
I'm sorry yo hear that. It must be a curse in this thread as I broke three ribs doing mountain bike just a month ago!