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Genz Benz Streamliner Tube Rolling

#21
Note that "gain" is only one parameter that's different between all of the 12A_7 family. There are different dynamic impedance and current curves and bias/operating points that will vary between tubes in the family. Voltage gain (or another critical operating parameter) of the circuit may depend on a specific plate current capability, and if the tube can not be biased to deliver that amount of current swing something may not operate properly. There's a lot more going on than appears on the surface.

Also, some circuits will not bias correctly or will operate way too far off the desired operating point with some tubes if the parameters or curves are very different. Which curves depends on which circuits.
 
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#22
agedhorse said:
Note that "gain" is only one parameter that's different between all of the 12A_7 family. There are different dynamic impedance and current curves and bias/operating points that will vary between tubes in the family. Voltage gain (or another critical operating parameter) of the circuit may depend on a specific plate current capability, and if the tube can not be biased to deliver that amount of current swing something may not operate properly.
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I'd like to know more about this stuff. We were only taught solid-state electronics when I was in college, so i'm pretty much self-taught when it comes to tubes.

The books i've read from guys in the MI industry (Aspen Pitman et al) have all been long on practical application, and short on theory. Can you recommend any good reading materials?
 
#23
Some of the old tube era design manuals, and engineering books. Understand the variables involved in the transfer function equations and you will then recognize the importance of each variable in the solution.

I too was at the tail end of the tube era, we did look at circuit solutions with triodes purely as a learning experience (and as an introduction to the FET principle which was pretty new at the time).
 
#26
seamonkey said:
Some of these old books the copyrights were not renewed and are available online.

Technical books online

Good books, like:
"Getting the Most of of Vacuum Tubes"

Somewhere between this ancient knowledge and today many myths have appeared and continue to echo across the internet.
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Great resource, thanks for posting. I just downloaded this book to my iPad.
 
#31
I put one of these in V3 for the Mid Control. They are no longer available. I keep hoping someone will come along and pick this moder design up and restart production. Great tube.

black-valve-01-1.jpg


In V1 I have the 5814A and in V3 I have a 1955 Mullard ECC83 Long Plate. I need to try some other stuff as well for kicks.

If you can find any I like the EI 12AX7's but they are hard to come by as the factory went belly up a few years ago. I have some gold pin versions from a buying spree I went on. They do not work so well in a hi gain guitar amp but they work great in a bass amp and have really good clarity.
 
#33
Ukiah Bass said:
Today Jeff Genzler told me these are the factory specified tubes:

All are Ruby Tubes

V1= 12AX7-CZ
V 2 and V3 are 12AX7-AC5 tubes

Can anyone suggest where one could buy all of these from a single source? I've been coming up short after hitting tubedepot and several others. Thanks.
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http://www.dougstubes.com has both.
12AX7-CZ are rebranded JJ's
12AX7-AC5 are Chinese

Dougs tests all of the tubes they sell too. Great vendor!
 
#34
#35
Ukiah Bass said:
I saw they have the AC5s but could not find CZ. They do have an ACZ -- is that the same thing? It's a high gain JJ ECC83.
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The Ruby catalog only has the 12AX7AC5 HG and 12AX7AC5 HG+ so I am sure they are the same. The + are the same tube but just test better.

I would not get hung up on getting the exact same tubes anyways. Rolling is half the fun!
 
#36
Gig report on the EHX 12AY7 in V2:

I've played a couple of fairly quiet duet performances with the new tube, and I'm really digging the smooth, round tone I'm getting with the bass and low mids (220Hz) rolled back to around 9 or 10. Not a lot of punch, just a nice laid-back sound that sits very well with rhythm guitar and vocals. Sounds like playing through a good studio channel strip.

I also used it at a loud, bratty rock rehearsal last night. Boosting 2.7K with the bass at 9 and the treble at 1 gave me a nice subtle midrange grind. This is the first time I've been able to enjoy the 2.7K setting on the mids, because up until now, I needed the mid control to help manage the low end.

The 12AY7 is definitely working better for me, than the stock 12AX7. I'm still getting that rounded Streamliner sound, but the pillowy low end is more subtle, less in-your-face. This could be a keeper. Not bad for a $13 mod...
 
#37
BeauZooka said:
I suspect that the 12AX7-CZ is a rebranded JJ. I think CZ stands for Czech Republic, and I think that JJ is the only tube producer there.
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Mine was not a re-branded. It was a JJ labled JJ.

BTW folks. Only buy JJ tubes from Bob at Euro Tubes. He gets the cream of the crop. Do not ever buy a JJ tube from a New Sensor based supplier. You can count on almost every tube being a dud as they only sell the rejects.

Also check out the tonal differences between the JJ ECC83 and ECC803 tubes. Biiiiigg difference.
 
#39
OK, so I'm baffled. I was bench testing some other gear, and got curious about how the EHX 12AY7 in V2 would look on the RTA. I hooked my Streamliner up and ran a set of frequency response plots at various tone control settings.

It occurred to me that the numbers didn't seem a lot different from what I saw with the stock tube, so I swapped the OEM Ruby 12AX7 back in, and ran the charts again. Sure enough, they were identical to within tenths of a dB.

I'm still convinced that I'm hearing a noticeable difference between the two tube types in V2. If it isn't frequency response, what am I hearing when I roll the tubes?
 
#40
I'm not really sure that V2 and V3 would affect gain at all. They are driving the EQ section not amplifying signal. I think the greater tonal difference would be affected by the capacitance of the tube rather than the db.

V1 I can see would have a major affect on gain by substituting amplification factors.

I'll have to try some different tubes (other than what I already have) in V2 and V3 and see what the affect is.

Oddly enough I did have a tube go badly micro-phonic in V3 and you can tell how much that tube is really in the circuit when this happens.
 

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