6176

antichef

antichef

pornk rock
Hey I have a new UA 6176 - i have not yet applied power to it. Here's the guts:

guts.JPG

Build quality is very good, imo. The case is a little flimsy compared to some other rack units I have, but it keeps the weight down, which is greatly appreciated - my main rack is oppressively heavy already.

I guess I was expecting a bigger output transformer for the preamp section (assuming that's what this is):

trafo.jpg

but - it is just a preamp section. The output tube is a mere 12AT7/ECC81 (the one in front):

tubes.jpg

which brings me to the reason for my post. These are new JJ tubes - probably fabbed in the Balkans. UA claims to have tested them, and I bet they're great (and if they are great, I will use them). But I've also read about folks changing out the tubes for older American/Western European ones.

As chance would have it, there was an old TV/Radio repair shop not far from my old place that I use to raid for tubes, and I wound up with several old GE and RCA and a couple of Mullard 12AX7s and 12AT7s. Some of them are noisy (including the Mullards, unfortunately), but some of them are good -- so - do any of you have any ideas for a before/after test? Without guidance, I'm planning to use a glockenspiel, because there's one sitting next to the rack, and it's something that sounds pretty much the same each time you strike it. I could use a C414 for the mic. I'll be using a Lynx converter, which seems really clean to me and has a ton of headroom.

Any ideas? I'm happy to post the results.
 
No guidance for the impulsive? I couldn't wait. I both like and hate doing these tests and at the same time appreciate that they're kind of a waste of time (hence the reason why those people who have the expertise and resources to do the tests well generally don't do them, leaving the job to people like me). I like the tests because they go some distance toward satisfying my curiosity and let me geek out a little. I hate them because all the way through, the limitations and defects of the tests themselves and the testing process are glaring.

Anyway - I went with these replacements:

tubes1.jpg

You'll have to trust me, but the one on the left is a GE USA made 12AT7 which I had previously determined to be quiet (i.e. not hissy) - most old (and the few new) 12AT7s I have tried seem to hiss.

The one on the right, which you can kind of see, is an Amperex Dutch made ECC83/12AX7.

[edit: wow, those pins are pretty dirty - didn't notice until I looked at the pic. The sockets in the 6176 are really beefy, though, and I think they're cutting through the uck)


Samples in a sec....
 
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I used both the Glockenspiel and DI electric guitar. I suppose DI bass (and a whole lot of other things, like vocals) would have been nice, but my bass sucks and it's downstairs (and I can't sing). For the test, I "split" the preamp and the compressor and worked only with the preamp, where the tubes are. I had the input gain at '0' and the output level at 3.5. I let everything warm up for 5 minutes before recording.

I exported to massive 24 bit wav files - you deserve no less - but if you're on a slow connection, you might want to wait until you're not.

The guitar is a SG standard using the neck pickup (for more bass) - I can't even remember what it is, but it's probably the stock 490R.

I won't make you all guess - here's the unit with stock JJ tubes with the DI guitar:

http://www.recursor.net/6176/6176-stock-diguitar.wav

and here it is with the Amperex/GE combo with DI guitar:

http://www.recursor.net/6176/6176-old-diguitar.wav


For the Glockenspiel (can I call it a Glock for short?) I used an AKG C414B-ULS mic in cardioid mode in front about 4 inches away. There are actually some "performance" differences - I had no idea how expressive you could be with mallets, but hopefully you'll hear through them. I let the mic warm up too, btw - it's got some honkin' capacitors:

Stock JJs:

http://www.recursor.net/6176/6176-stock-glockenspiel.wav

and with the old ones:

http://www.recursor.net/6176/6176-old-glockenspiel.wav
 
It's worth noting that I've moved from my first-string setup downstairs to a more comfortable chair to post - down here I've got some low-end monitors, and a low volumes, I can't really hear a difference.

But anyway, on the good monitors at high volume, I was kind of surprised -

What I thought: There wouldn't be much difference, but maybe the JJs would be noisier

What I heard: There wasn't much difference in noise - the JJs were very quiet, and the old tubes maybe a little bit noisier (maybe I need to clean the pins). The JJs had more, or more strident high frequencies - the Glockenspiel kind of hurt my ears when all the notes were blending together. The older tubes had either less or smoother sounding highs.
 
Hey antichef - don't let the chirping crickets get you down. I know the complete lack of response from anyone could leave you feeling a little insecure, but don't let it! Keep fighting the good fight.

You know, the 6176 has variable impedance settings for the input - you failed to mention which ones you used.

Did I say 'failed'? I didn't mean...

I didn't.... um....
 
Thanks for the encouragement antichef! I used the lowest impedance setting for the mic, and the highest for the DI guitar.
 
I couldn't hear everything you said over the din of the crickets (which I think would have made a great test subject, btw) But did you say you swapped out tubes tested by the manufacturer and known to be good because you read somewhere on the internet that they may not be good???
 
yes.

I should say that I've had similar experiences swapping out newer tubes with older ones in guitar amps. The one exception has been the last of the new Orange amps I got - the tubes are new, and they sound great. But much (not all) of the time there's a shrillness/ phasiness/ or noise with the newer ones that doesn't seem to be present with the old USA/Western European ones, for the most part. The old ones can be duds, too - especially in the noise department.


BTW, I'm really liking the 6176 - I patched in the compressor to the vocal track in a mix I'm working on, and it was like a new world :) -- with the new (old) tubes, I'm sure I'll be at least trying the preamp on a bunch of sources, including vox and, in the very near future, bagpipes (for the chanter mic)
 
I use the LA610MKII - same pre with stock tubes and it is a nice sounding unit. I don't think I'll try out different tubes though as I'm much too lazy lol....
 
ido1957 - that does look like exactly the same pre with a different compressor. Glad you dig it - have you had it for a while?

I just spent about an hour noodling direct with a guitar just to get the feel of the compressor on mine - sounded very nice, I thought.
 
thanks for listening Greg - yeah I guess the extra bass and treble on the JJs make the guitar sound fuller
 
I have had it for over a year and love it. I have only recorded with it a couple of times but it has always sound good with just a touch of eq and compression.
 
I wound up putting back the JJ 12AT7 - better bass, but the harshness is still gone, so maybe that was coming from the 12AX7.

Anyway, I force my kids to record christmas songs on christmas, and we're starting to use it - so far so good
 
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