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Genz Benz Streamliner Tube Rolling

#341
Agedhorse,
After reading I have found some tubes are failing due to Heater-Cathode voltage exceeding the rated voltage when used in a Cathode follower circuit (not necessarily the Genz Benz). The data sheet in the link provided shows the Heater-Cathode max rating is 180 volts for the Tung-sol Reissue 12AX7. Can you tell me what the V2 and V3 Heater-Cathode voltage (max) is for the Streamliner 600/900 please. Please forgive my being cautious, I just love this amp and don't wish to experience any damage to the amp as a result. If you can just assure me If a tube failed in this amps V2 and V3 positions it would limit the damage to the tube only and not the amplifier then that is all that matters to me and you do not have to state the circuit voltages.
Thank you and I value your help here,
Gary

Here is the datasheet
[Invalid or Expired Link Removed]
 
#342
Looking into this more, 180v is the typical cathode to heater voltage spec in my books. A cathode follower is typically biased (by design) at 1/2 the plate voltage quiescent or about 150 volts between cathode and heater ground. Add to this the signal excursion and you are still within spec. which is a guaranteed minimum sustained voltage. I do not have an explanation for why this may not apply for this particular tube.

LoveThatBass said:
Agedhorse,
After reading I have found some tubes are failing due to Heater-Cathode voltage exceeding the rated voltage when used in a Cathode follower circuit (not necessarily the Genz Benz). The data sheet in the link provided shows the Heater-Cathode max rating is 180 volts for the Tung-sol Reissue 12AX7. Can you tell me what the V2 and V3 Heater-Cathode voltage (max) is for the Streamliner 600/900 please. Please forgive my being cautious, I just love this amp and don't wish to experience any damage to the amp as a result. If you can just assure me If a tube failed in this amps V2 and V3 positions it would limit the damage to the tube only and not the amplifier then that is all that matters to me and you do not have to state the circuit voltages.
Thank you and I value your help here,
Gary

Here is the datasheet
[Invalid or Expired Link Removed]
Click to expand...
 
#343
agedhorse said:
Looking into this more, 180v is the typical cathode to heater voltage spec in my books. A cathode follower is typically biased (by design) at 1/2 the plate voltage quiescent or about 150 volts between cathode and heater ground. Add to this the signal excursion and you are still within spec. which is a guaranteed minimum sustained voltage. I do not have an explanation for why this may not apply for this particular tube.
Click to expand...

I am thinking there is some "Snake oil" being posted on the Internet and some tubes such as Sovtech 12AX7LPS that is touted to have a high premature failure rate in a CF circuit as possibly tube quality. As woolysock stated below:
woolysock said:
Would like to see the post where you got your info.
Been running a TungSol 12AX7 in V2 & V3 for more than a year and still sounds great.
Click to expand...
 
#344
FWIW...I haven't replaced any of the preamp tubes in my SL-900 and it sounds totally brilliant. I have no issues whatsoever with 'tubby', 'flubby' or any other kind of undesirable sound/tone with the low end. My personal settings give me a warm, full, thick and ever so slight growly sound. This amps magic settings for each particular user are in the hugely interactive eq. Love this amp.
 
#345
godblender said:
FWIW...I haven't replaced any of the preamp tubes in my SL-900 and it sounds totally brilliant. I have no issues whatsoever with 'tubby', 'flubby' or any other kind of undesirable sound/tone with the low end. My personal settings give me a warm, full, thick and ever so slight growly sound. This amps magic settings for each particular user are in the hugely interactive eq. Love this amp.
Click to expand...

Same here with my STL 600. Just a curiosity what other tube may or may not do for me.
 
#346
I purchased some Ruby Tube 12AX7's from Doug's and got them today. My Favorite is the same as the Stock V1 Ruby Tube 12AX7 ACZ (which shows it is a JJ 12AX7 ECC83S) which Ruby buys test them and gives you a 6 month warranty instead of JJ's 90 day and then puts their Sticker label on them. Excellent tube! So I have to say the age old saying "If it ain't broke, don't fix it" ;)
BTW: I did buy 1 JJ 12AU7 ECC82 to try in V2 slot as previous posters mentioned and have one comment STUPID! lol

What I do like about Dougstubes.com is he tests them and writes the gain reading of each section on the box and the tube (i.e. 110/110)
 
#348
agedhorse said:
The ACZ tube from Ruby is really hard to beat, and they have proven to be quite reliable.
Click to expand...

I had at least 1 of each type 12AX7 that Ruby offers and that was the only one that made me smile. Don't get me wrong, the Ruby 7025 and AC5 and AC7 are good but the ACZ just had that Special touch, smooth sweet mids and highs and focused tight lows.
BTW Andy: I am having a hard time putting the top back on because the internal workings are so beautifully done but goes back on tomorrow. Can't look at it forever ;)
 
#350
I am back with the stock tubes as well. I found a set of tubes that I preferred to tame the low end, but that was when I was using Chromes. I swapped in some fresh nickel rounds and the tone went from crisp to anemic and brittle, so I tried the original tubes. The stock tubes work great with this particular bass, string and cab configuration.

Just a reminder that all the parts factor in.
 
#351
3rdcurve said:
So you stayed with stock tubes then?
Click to expand...

Yes I stayed with Stock with one exception, I left a new Ruby 12AX7 ACZ HG in V1 only because Doug and Dougstubes.com wrote that it was matched sections 110/110. I did not ask for anything but the free standard testing. He writes the gain values on the tube and the box. Nothing wrong with the stock so I put it in the box the new tube came from and stored it.
 
#352
Funny, none of my amps have tops either;)

Matched gain sections don't matter in this amp, there is nothing that benefits from this. Places where this can matter is in phase inverters, long tail pairs and current sources/mirrors.
 
#354
LoveThatBass said:
Good to know Andy, So it wouldn't even help with overall gain?
Thanks,
Gary
Click to expand...

Nope. Matching just improve the ratio of gain between the two sections. Overall gain may be higher or lower independent of how closely they are matched.

You need to know how each section is used in the circuit before you can make any assumption as to how absolute gain may affect performance. Higher gain may of may not have any significant effect depending on the circuit it's used in.
 
#355
agedhorse said:
Nope. Matching just improve the ratio of gain between the two sections. Overall gain may be higher or lower independent of how closely they are matched.

You need to know how each section is used in the circuit before you can make any assumption as to how absolute gain may affect performance. Higher gain may of may not have any significant effect depending on the circuit it's used in.
Click to expand...

Thank you Andy, That that is good to know so we don't spend extra money for Tube matching etc.
 
#356
Hi Steve,

Have you had a chance to chart the frequency response with the 12au7 in V2? I'd be curious to see that one. I'm planning on doing some rolling in a few weeks, and that's the one I'm really interested in.

Thanks,
Jeremy


steve_rolfeca said:
Finally got my RTA software problem figured out, gonna take a while to get traces posted, as I have to re-do all my plots. Grrr...

Anyway, here's a set of traces for a 1969 greyplate RCA 12AX7A in V1, OEM tubes in V2 and V3. RTA was reading preamp only, coming off the Preamp Out jack. Mid frequency switch was set at 2.5K, and the tone controls were at 10 o'clock for the bass, just past 2 o'clock for the mids, and half-way between 10 o'clock and 11 o'clock for the treble.

The curves show the characteristic treble change at various Gain settings with a 12AX7A in V1. This is not an RCA thing- the curves for the stock JJ/Ruby are the same to within a few 10ths of a dB.

EDIT: I ran another set of curves this morning, playing around with the Volume knob and varying overall signal levels. Proved that impact on tone is mostly dependent on the Gain knob. Volume only changes the treble response by a dB or so...

I'll post the curves for an Electro Harmonix 12AY7 when I get some time- the treble doesn't change as much with level and/or gain variations...

RCAinV125K10-22-105.jpg
Click to expand...
 
#357
Checking in to say another 5751 believer here. I was about to sell my Streamliner 900, it's just too fat, too much bass, not quite fast enough, could never get a growl out of it. After reading the tribulations here, bought myself a JAN Philips 5751 and can't believe what a difference it makes! Actually, it's kind of subtle, but it's subtle in a place that makes a huge difference: like everyone says, it tightened up the low end, and gave the sound a general clarity. But what I wasn't quite expecting is the punch it has now. Maybe the punch was always there, somehow occluded by all the roundness of the sound, but the STM900 with a 5751 in V1, at least in the practice room, is a growling punch machine. Something else I wasn't expecting: I can dial in a Stanley Clarke sound! There is still a huge amount of treble and brightness with the 5751. And even though the low end is tightened up, there remains a ton of bottom there. Crank the lows and highs, and cut the mid, and boom: Stanley. The short of this long-winded missive is that the STM900 becomes a massively more useful tool with the 5751 in V1. GB really ought to look into putting in this tube as stock.
Anyway, can't wait to get it onstage.
Thanks guys for the recommendations about this mod. Definitely worthwhile, unless you already love the sound of the STM, in which case you're set.
 
#358
I'm just back from a gig w my STM 900 w a JAN Phillips 5751 in V1 and lemme tell you it sounded great. I run the treble at noon, mids at noon and roll the bass back to just under 10. Punchy indeed. And w harmonic complexity. I mean my P-bass sings! This amp configuration makes it such that your fingers really control the tone and the amp is super responsive. Cheers!
 

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