Tube Rolling w/Crack

Can anyone advise as to whether a Shuguang cv181-z is a safe 6sn7 alternative in the crack? 

I've read conflicting comments on the net - one site claiming the cv181-z is a safe 6sn7 replacement "in any circuit" (http://thetubestore.com/sh-cv181-z.html), while another gives it rave reviews while also emphasizing the heightened current draw from the heaters of the cv181-z (http://www.tnt-audio.com/accessories/shuguang_treasures_cv181_e.html).  Has anyone tried this tube in their crack, and is it okay to do so?

Thanks in advance for any comments any of your can offer!
 
Neither of the suggested web sites has much actual data, and I'm afraid the tnt-audio one has a fair amount of misinformation. (I am not questioning his listening report, just some of the technical aspects.) Do read his follow-up article. But Grant Fidelity has a spec sheet for the tube:

http://grantfidelity.com/site/files/shuguang%20treasure%20tube%20spec%20cv-181_0.pdf

From these specs, it is equivalent to a 6SN7-GTA, including the same 600mA heater current, the same mu of 20 and transconductance of 2.6mA/volt, and the same 450v maximum plate voltage. In fact the specs are so identical that it is clear they are copies of the 6SN7 specs. A couple of them are mis-labeled but the intention is clear. Not surprisingly, no information is available that I could find reporting how close to these specs the average tube might actually be.

A real CV181 (no -Z, not from Shuguang) is said to be equivalent to an ECC32, but the available information is small and inconsistent - I found one report of 600mA and another of 950mA heater current, for example. Why they would mark a tube with the designation of another is beyond me - unless they mean to indicate the size and shape of the envelope rather than the operating parameters. Kind of like a $20 "Rolex" watch, I guess.  :^)
 
Much appreciated Paul!  Setting aside the needlessly confusing naming scheme, it sounds like they should at least be safe to try in the crack - at least based on the paper specs.  I've heard generally good things about the "treasures" on head-fi - although I believe most of the chatter was about their 300b variant.  

I just might give one a try.  If I do, I'll make sure to chime back in and let you all know how it worked out.

Thanks again for breaking this all down for me!  

 
Yes, after my initial enthusiasm for the 2a3z Treasures, they didn't live up to the hype for me -- very smooth sound, but not very good on the top end.

I really like the Russian military 6h8c 6sn7 equivalents (well, almost equivalents) -- the military version with the metal base -- the regular run of the mill ones are again, nothing to write home about.  Of course the real ones are hard to get and expensive.

-- Jim
 
This thread has gotten quite long, so I'm not sure where the crept in - but a 6SN7 is a viable substitute for the 12AU7 (with a socket adapter). It is NOT a substitute for the 6080/6AS7/etc! You can plug it in and you'll get some sound out - for a while - but it will throw the operating points way out and will increase distortion a lot.
 
I have one of those adapters on the way and a box of red base 6sn7's Ken-Rad's etc.  I can't wait to tube roll.  I've promised my self to give it a week before I start rolling
 
I just put in the JJ 12AU7 just to see if it was any better than the EH and I think it's more musical and I can hear better seperation in between the instruments.  For a ten dollar new production tube it's worth a roll. 

Next is the groove tubes 12au7 ( I think I saw one in my tube box).  I'm waiting for at least 24 hours of break in before I try my telefunken and clear top rca's
 
Paul Joppa said:
This thread has gotten quite long, so I'm not sure where the crept in - but a 6SN7 is a viable substitute for the 12AU7 (with a socket adapter). It is NOT a substitute for the 6080/6AS7/etc! You can plug it in and you'll get some sound out - for a while - but it will throw the operating points way out and will increase distortion a lot.
Click to expand...

Thanks for the further clarification Paul!  I had gotten the naming schemes mixed up in suggesting that I might use a Shuguang in place of my 5998.  I have edited my prior post accordingly to minimize the confusion.
 
I couldn't resist....  After 15 - 20 Hrs. of break in I put in a 50's NOS Sylvania 6AS7G (black plates) and a Telefunken 12AU7.

All I have to say is holy crap!  That is the closest I've ever felt to "being there" while listening to my gear.  My Crack is totally stock and I did this on purpose this time so that I could see what changes made the biggest difference.

I can't wait until it breaks in!

My source is a heavily modified Philips DVD 963 SA.
http://www.diyaudio.com/forums/digital-source/19911-upgrading-philips-dvd-963-sa.html
The key mods were:
Replacing opamps in output stage with BB OPA627's
Coupling caps are Blackgate NX
Main PSU cap is a Blackgate VK (or STD, I can't remember )
Nichicon Muse KZ's in all the key locations
Seperate Bi Polar regulated supply for the output stage ( bumped up to 24V, if I remember )
Replaced DAC chip with next model up in the same line, and then stacked another one on top ( That was not for the faint at heart )
 
Does anyone know if oxidized pins can result in hum?

I recently picked up 2 supposedly nos RCA 12bh7a's on the cheap on ebay.  Unfortunately, the black plate tube (1959), supposedly the better of the 2, produces a pretty noticeable hum when plugged into my crack. The grey plate tube (1963), by contrast, sounds quite good and is perfectly quiet.  For purposes of comparison, I wouldn't say that I clearly prefer the grey plate to the 12au7 bugle boy I was previously running, but I do like it better than the RCA "clear top" 12au7 I also have on hand.

The black plate tube definitely has dirtier pins than the others and was harder to slide into the socket.  Could this possibly relate to the hum I'm hearing.  Would it be worth my picking up some contact cleaner to see if this possibly improves the situation?  Alternatively, do brass or copper dampers like these (http://www.audiotubes.com/damper.htm ) actually help to reduce hum? 
 
Just buffing the pins with fine steel wool can work wonders. If you want to get hardcore you can chuck a Q tip in a Dremel and polish the pins with something like Simichrome.
 
I used to use Caig de-Oxit and then some Pro Gold... I'll have to find it and try some out. I had forgotten about it.
 
I hosed one side of my precious 5998 by being too hasty with an input tube roll, I didn't give it nearly enough time to cool down before powering back up...I wanted to cry.
I did a little research and decided to try 7236, which is basically a souped-up computer-rated version of a 5998.  To my ears, I actually think it sounds a little better than a 5998!  It's at least as good.  I would have to highly recommend checking one out if you are having trouble getting your hands on a real 5998.  Yes, they aren't the sexy ST style bottle, but I think they still look pretty darn cool on the Crack.
Brendan @ tubeworld has a NOS pile of these right now for a very reasonable price.  I'm fortunate (my wallet says unfortunate) to be local to tubeworld.com HQ!
 
I should probably ask this on the tube forum at the Asylum but I'll give it a shot here.  I was digging through my stash and found two tubes that I bought a decade ago off of ebay.  They were sold as Philips ECC82's.  Both tubes are completely wiped except for some etched codes near the bottoms.  One has the Herleen Delta followed by 2B3 and the other the Herleen Delta followed by 2B4.  Also, looking at the bottoms, each has a single letter etched inside the glass.  One with a capital  H and another with a capital E. 
I never used them because I was never 100% sure if they were 12AU7's or 12AX7's or one of the 9 pins with similiar internal construction.  I havent been able to correlate the code with a tube type, I think its just manufacturing plant and date code but I dont know much about code.    They have Halo getters and the half circle through one side of the plates and look like Amperex 12AU7 / ECC82's but I have 12AX7's that look the same.  They are flashers, but I think a lot of the Amperex and other euro 9 pins were flashers.  I tested them as 12AU7's and they test as such (relative to my known 12AU7's)  but it's just an old heathkit emissions tester that I use to give me a very general idea of whether the tube is strong (atleast out of circuit) and mainly to test for shorts.
I didnt try testing a 12AX7 using 12AU7 settings (or vice versa) in the tester, I assume that I could try that without damaging the tester or the tube, but Im not positive.  If I plugged them into one of my hi-fi amps that uses a 12AX7 preamp tube, I suppose I would easily notice the lower gain in the decreased output from the amp if they are indeed 12AU7's, right?  I just dont want to roll one into Crack and do any damage if it's not a 12AU7/ECC82.

Any advice appreciated.  Thanks.

 
Ive had fun rolling a few tubes through the Crack.  I have a friend who does Gov't work who is also a guitar amp builder and he comes across some nice tubes from time to time and had a pretty modest stash (compared to Doc anyways)  I rolled the following all NOS except the Mullard which tested very strong

RCA 12AU7 black plate
RCA 12AU7 grey plate
RCA 5814a black plate
Mullard 12AU7
Tung Sol 12BH7A black plate
Amperex 12AU7 orange globe
RCA 12BH7 black plate
EH 12AU7
GE 5814A grey plate

Havent had a chance to try anything other than the Raytheon 6080WA that came with it but I did manage to pick up a NOS GEC 6080 on ebay ...I have no idea what to expect but for $20 i figured its worth a roll....

Im really liking the Tungsol 12bh7a the best right now and the RCA 5814A is just slightly behind it.

Tube rolling is really fun

Anyone tried an Amperex 7316?

 
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