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Little Dot I+ Tube Rolling
Jul 3, 2009 at 11:42 PM Post #391 of 3,154
so i will take notice of the batch I have coming from the Urals.
I didn't see anything at that link and when I stripped the url back to the site/hostname it redirected my to Disney.
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Yeha, I bought some tubes from yen. I sent them back for a refund. he gave the money back but the tubes were lame.

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Sylvania blue glass. ha. did some research and it may be that they are made by Brimar. I have a Brimar rectifier and in both cases those Brimars seem week.

Now the Amperex do seem worthy.

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Nice and detail, no rough edges, not the oomph you get from the Chinese 6J1 but they are sweet and fast with a lot of hifi trickery. these Amperex are most probably rebranded Mullards.
 
Jul 4, 2009 at 12:33 AM Post #392 of 3,154
it changed the + to a %20, bad forum!

you can try it now, it works

RightMark Audio Analyzer test: comparison

here is another goodie, EF91 CV4014s and EF92 large shield and small shield in MkII
Certainly makes no sense to say EF91 distort more.

Testing some CV4010 i got with I+ right now.
Going to be a EF91, 6J1P-EV, CV4010 comparison later.

Tell me if you think Large shield is worth the extra coin over small shield, like i said somewhere before, sounded the same to my ears, look a lot like each other in RMAA.
 
Jul 4, 2009 at 4:05 AM Post #393 of 3,154
Heater voltage as measured how little dot wanted to measure (across pins 3 and 4) is 3V.
But who would be surprised, i finally looked at the back of the amp....a 220V sticker quickly explained to me why everything runs at 1/2 the voltage, that it works at all and still performs so decently is amazing. just some high distortion, otherwise still powerful enough to drive even HD600....at half of everything...wow.

Will be fun retesting this little gem when little dot comes back telling me if i am in luck (double wind transformer i could change paralleled outputs to serial outputs to keep output voltage constant, or back up in my case) or if i am unlucky (and i usually are) and it's a single wound transformer needing replacement.
 
Jul 4, 2009 at 5:32 AM Post #395 of 3,154
Sure is, i did not think to look there, i bought it used form someone in the US, so i thought it's a done deal, i think he needs to try a working I+ when he gets around to buying another amp.....

I used to go by ear, and i think my ears are good.....or matching is not such a trouble....during setup of RMAA i noticed input level meters that i need to bring to -1db before running the test, matched pair (i do have 1 or 2) or unmatched, the levels hit the same value each time, I+ is very even, MkII has a .4dB imbalance on each set....and i couldn't tell it did, threshold for majorly good ears is what? 1dB?

Very informative experience all of this, i tell you that.
 
Jul 4, 2009 at 5:39 AM Post #396 of 3,154
"Nice and detail, no rough edges, not the oomph you get from the Chinese 6J1 but they are sweet and fast with a lot of hifi trickery."

I could steal your quote and claim i said that about the 6J1P-EV
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Jul 4, 2009 at 9:39 PM Post #398 of 3,154
Put OPA2107 back in so i can listen to it again with a properly working I+ after the transformer fix.
I figured i test 3.5x gain vs 7x gain.

While 7x gain does show 3dB more noise, it also shows only half the THD of 3.5x gain.
Take from it what you will, i take 7x gain since i like fact it drives my HD600 well.

RightMark Audio Analyzer test: comparison

I think i have measuring overload and stick to listening from here on until i can try the opamp bypass cap mod.
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Jul 9, 2009 at 7:38 AM Post #401 of 3,154
I've actually been using the GB-408a's more and more. The pins are not gold, but they are definitely a huge leap over the Sylvania 6ak5w's I have. Like I said, their different from the 6j1's; not better or worse. A little more bassy, full, and forward, less spatial. They color the sound in the same way that grados do.

I rolled a couple opamps, the LM4562 and the OPA2107. Much to my surprise I liked the 47 cent LM4562 more. I rolled these in with the GB-408a's though, so results might have been different with the 6j1's, but I swapped them back an forth a couple times to make sure. I was definitely expecting the opposite, especially since the OPA2107 cost about 25x as much. It just seemed to muddy up on complex/busy parts of some songs, and sounded rather lifeless.

I'm very very happy with my Grado SR80, GB-408a, LM4562 combo right now. Just perfect for rock music, which makes up a majority of my listening.
 
Jul 9, 2009 at 9:32 AM Post #403 of 3,154
i'm suprised there is not much mention of the Mullard EF92s.

I didn't like the Chinese EF92's mine came with. Excellent bass impact but the highs were just pericing and static sounding. One valve looked much older than the other and it was audibly quieter.

I got a 2 pairs of NOS Mullard EF92's for £32 and have never looked back. The mids are so much more detailed and the highs are smooth but still detail and dynamic the overall sound is much more liquid and fun with the sacrifice of a little bit of bass. The little dot I+ works fantastic with RS-1's!
 
Jul 9, 2009 at 12:22 PM Post #404 of 3,154
the LM4562 is a fast opamp @ ~55megahertz. The OPA2228 I have is about 33 and you can sense the slowing up on the OPA. I think the LM is fast enough to get out of the way. But with this speed, so I have found in reading about these opamps, the speed causes oscillation unless you add some capacitance to the power pins. Then tieing to ground draws the noise to ground.

Now with a sharp set of caps you might like the OPA since is softens the bite. But with a nice set of schmoozy tubes like the 6J1 or Mullards then the fast LM can unravel all the details and dynamics while retaining whateve character the tubes have. Big win/win.
 
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