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The article below after I re-read it again,I guess states that the Valvetronix amp might have benefited from the use of EL84s...I mis-interpreted the info...

I didn't think that you could fit one in there, only 12a's. For that matter anyone tried out a lower gain tube like a 12at7?

I thought thoae amps only had one pre amp tube...


Originally Posted by the guy who invented fireI thought thoae amps only had one pre amp tube...

Me too...

I think that John is running out of pedals to mod.......he's asking crazy questions! LOL!!!

LOL....I never seem to run out of pedal mods! I have Wattage's DD3 I'm on a break from after a repair....

The 60 watter only has 1 12AX7 for the Valve Reactor
The 120 watter has 2 12AX7s....

I read an article about the Valvetronix where this guy use EL84s instead,but there was no mention about tonal changes....Guess I'll be the test dummy....

from : localhost/interpret this article in that Vox should have used EL84s in the output section and not the 12AX7s......Power-Tube Distortion Placement in the Chain
quot;You can make the power tube (one per side) distort by turning the quot;Gainquot;, quot;Volumequot;, tone, and quot;Masterquot; controls very high, and then I venture that the distortion is not quite as smooth and gradual as an actual power tube such as EL84. This is post-delay distortion, so heavy echo with heavy 12AX7 power tube distortion causes dissonant beats as you bend a note. Why didn't VOX put delay after the power tube and dummy load, as is standard for a dummy-load rig?

In practice, if you avoid that 12AX7 power tube clipping, you can think of the quot;power-amp modelquot; (it sounds like there are just 3 distinct ones) as a mere final eq. Reread the marketing lit in that light: quot;The VariAmp Power Circuit [solid-state amplification after the 12AX7 power tube saturation] cannot be overdriven, is totally transparent ... The VariAmp Power Circuit does not color or change the signal in any way and the resulting output tone is pure.quot; Echo is before power tube saturation, but that's a universal problem solved only by adding echo at the mixer or after the dummy load in a 3-stage amp rig like Van Halen.

Direct-inject of a loud signal into the fx loop return (between echo and 12AX7 power tube), then cranking the quot;Masterquot; knob, produces 12AX7 power-tube distortion. I need a signal generator and scope, to see at which stage distortion is being introduced. I trust that when you crank the quot;Gainquot;, quot;Volumequot;, and quot;Masterquot;, and tone stack, the final clipping is actually the intended 12AX7 power-tube saturation, and not some solid-state buffer.

This amp has two distortion stages:

o The quot;Gainquot; distortion, which I think of as preamp distortion and power-tube saturation rolled into one as in the POD or SansAmp

o The 12AX7 power-tube saturation that, with dummy load, is immediately before the final solid-state power amp.

Cranking the Volume and Master controls does cause 12AX7 power-tube distortion but that I suspect, as I've always held, that EL84s would probably sound better. So to speak, swap the 12AX7s with EL84s instead.
The Headphone jack enables you to hear the 12AX7 distortion, indicating that the headphone jack is not positioned like in a POD, but later, after power tube and dummy load.

An interesting exercise is to turn up the reverb, then crank Volume and Master to produce that dubious-quality 12AX7 power-tube distortion. This produces strong distortion after strong reverb, which causes reverb ducking; when you hit the strings, no reverb is audible at all, then as the notes die, the reverb swells up.

Also, strong echo followed by strong 12AX7 power-tube distortion causes the expected beats as you bend a note. This may be one reason some people like real room reverb better than built-in reverb that's positioned before power-tube distortion: reverb followed by distortion sounds unnatural, largely because of this ducking effect. Real room reverb is always after the power-tube saturation and speaker distortion, so there is no reverb ducking; there's always more headroom for real room reverb to respond to the amp's peaksquot;.

I'm not a tube expert by any means, but I wouldn't go plugging a power tube where a preamp tube should go. The pinout is probably way different anyway and it wouldn't fit. I hear what your saying about power tube gain and all, it's good stuff.

Here's a (short) list of 12AX7 substitutes:
from : localhost/tdsl.duncanamps.com/show.php?des=12AX7

Here's a good list of different 12AX7 substitutes' gain characteristics:
from : localhost/www.torresengineering.com/realinonprea.html


Originally Posted by DankerellaI'm not a tube expert by any means, but I wouldn't go plugging a power tube where a preamp tube should go. The pinout is probably way different anyway and it wouldn't fit. I hear what your saying about power tube gain and all, it's good stuff.

Here's a (short) list of 12AX7 substitutes:
from : localhost/tdsl.duncanamps.com/show.php?des=12AX7

Here's a good list of different 12AX7 substitutes' gain characteristics:
from : localhost/my idea....I was reading the article and it's all quoted above in my post...The Valvetronix doesn't have preamp tubes...The 12AX7s are used solely in the output section of the amp...quot;Valve Reactor Technologyquot;

not to get too far off topic, but what are you doing to Scott's DD-3? I have a DD-5 and if it can be Spinaized, maybe it should be!

Sounds freaky to me. The EL84 is a single pentode where the 12AX7 is a pair of triodes. I'd be surprised if the EL84 had a pin-out that was even compatible with 1/2 of the AX7. Finally, I don't see him saying he tried it, merely that he suspects it would sound better.

Can you say quot;guinea pigquot;?


Originally Posted by the guy who invented firenot to get too far off topic, but what are you doing to Scott's DD-3? I have a DD-5 and if it can be Spinaized, maybe it should be!

I don't mod time based effects...Scott's DD3 got a new switch is all....


Originally Posted by alecleeSounds freaky to me. The EL84 is a single pentode where the 12AX7 is a pair of triodes. I'd be surprised if the EL84 had a pin-out that was even compatible with 1/2 of the AX7. Finally, I don't see him saying he tried it, merely that he suspects it would sound better.

Can you say quot;guinea pigquot;?

No guinea pigs here! LOL... :fing25:

The article reads that Vox could have used the EL84s instead of the 12AX7s...My bad....

With my knowledge of tubes,I'm surprised on my way of thinking on this..Anyway.....I goofed...

John

Hey John. Did'nt you change the tubes in your 120? Was it worth the money and effort, and do you think it would benefit my 60 watt head? What tonal difference did you notice? Scott.


Originally Posted by sacHey John. Did'nt you change the tubes in your 120? Was it worth the money and effort, and do you think it would benefit my 60 watt head? What tonal difference did you notice? Scott.

Yep....Both my Valvetronix and my Fender Cyber Twin have a set of RCA Black Plate 12AX7s....They are pricey,but I really feel like they make both amps more powerful and rounder....Maybe not powerful so much,but the amp seems rounder and just better sounding to my ears? If it's not the case,then mentally I'm happy with it...