# SS 12AX7



## Paul Running (Apr 12, 2020)

Wondering if anybody has tried this product?





AMT 12AX7WS Warm Stone LE | AMT Electronics official website


AVAILABLE NOW THIS PRODUCT USED BY MUSICIANS:




amtelectronics.com


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## Lincoln (Jun 2, 2008)

wow! Never seen that before. Is that our future?

I imagine an IC provides the amplification?


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## Lincoln (Jun 2, 2008)

We need Wild Bill's opinion on this one.


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## Granny Gremlin (Jun 3, 2016)

Interesting. Kinda surprised nobody else has tried something like this before. Precident exists - see the octal plug in diode rectifiers that replaced a lot of tube rectifiers in the 70s.

I wonder what the price is (didn't see in the link - did I miss it?). Also curious about the highlighted caveat (make sure B+ is at least 30V) - more important is the max, but at least we know it may work in some starved plate designs.


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## Paul Running (Apr 12, 2020)

Not sure about retail sales however, they do have a Canadian distributer in BC. Speculating that power for the ICs is provided by switch-mode means (SMPS transformer) so, a voltage less than 30VDC and the power to the ICs becomes unstable which would affect the devices linearity. Here's the data sheet for the device:


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## jb welder (Sep 14, 2010)

Granny Gremlin said:


> Interesting. Kinda surprised nobody else has tried something like this before.


See mesa boogie 'fetron'.

I guess this is a solution for when tubes are not available and some will want to have solid state amps that have all the weight and size of real tube amps.  At that time I'll just go solid state thanks.
They can have whatever specs they want, but unless they compress and distort when overdriven exactly in the same way tubes do, it's pretty much a dead end. And that is something that does not show up on datasheets.
Seems kind of like a solution in search of a problem, to me.


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## Latole (Aug 11, 2020)

Lincoln said:


> wow! Never seen that before. Is that our future?
> 
> I imagine an IC provides the amplification?


Future ?

It's just a solid state circuit in a different package.
I must admit that the idea is ingenious.
But who likes tube amps would like to convert them to solid state? Just buy solid state amp.

How many times have we read that a new solid state circuit would be equivalent to tubes


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## Granny Gremlin (Jun 3, 2016)

jb welder said:


> See mesa boogie 'fetron'.


Cool - will check those out as prior art.



Latole said:


> But who likes tube amps would like to convert them to solid state? Just buy solid state amp.


I get that - about the compression and distortion, BUT, I do think even without those it could be useful. Tube front ends find certain signals hard to handle (like my Gibson basses - 30k mudbuckers produce near sine wave fundamental and V1 chokes on it; similar thing with my active RD artist, just not as bad - solid state amps, or at least preamps, handle these a lot better). I wonder if subbing in a solid state device like this might help with that; you can still get compression and distortion from the rest of the amp. Like the idea behind 70s Musicman amps - a more robust ss preamp with a tube power section makes sense - much more so than the other way around (which is done ju7st so they can say there's a tube in it, while lowering pricepoint and weight). Except I'm proposing just a ss V1 with the rest of the preamp remaining tube.

Luckily I don't think 12AX7s are going anywhere anytime soon.


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## Granny Gremlin (Jun 3, 2016)

heh - for 150shipped I'll take a 12AX7 thanks (or DIY something).









Mesa Boogie Fetron Device 1978 Came From My Mark II Boogie | Reverb


VIEW MY OTHER LISTINGS FOR A BOATLOAD OF OTHER ACCESSORIES AND PARTS So I bought my first Boogie from a friend who bought it new in 1978. Had the choice of tube or this "Fetron" device. Don't know if it was in the preamp section or rectifier. Boogie is long gone but still have this. I am sur...




reverb.com


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## Jerome (Dec 4, 2015)

I also remember Fetrons , solid state plug in replacements for tubes . Recall seeing some in an electronic surplus store , back in the '80's .


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## rtomancini (Dec 26, 2021)

Hi
Did some research and found this:
-Video
and a paper explaining in detail the concept of solid state triodes.


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## player99 (Sep 5, 2019)

Do they provide even or odd harmonic overtones?


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## nonreverb (Sep 19, 2006)

jb welder said:


> See mesa boogie 'fetron'.
> 
> I guess this is a solution for when tubes are not available and some will want to have solid state amps that have all the weight and size of real tube amps.  At that time I'll just go solid state thanks.
> They can have whatever specs they want, but unless they compress and distort when overdriven exactly in the same way tubes do, it's pretty much a dead end. And that is something that does not show up on datasheets.
> Seems kind of like a solution in search of a problem, to me.


The FETRON! I've got one of those somewhere in my shop. One had to reduce the plate voltage before it was plugged in from what I recall from the Mesa documentation.


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## Paul Running (Apr 12, 2020)




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## aC2rs (Jul 9, 2007)

An interesting concept.
I wonder what the market for them is?
Personally I will stick to regular tubes


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## Paul Running (Apr 12, 2020)

aC2rs said:


> I wonder what the market for them is?


Applications concerning these primary characteristics:


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## geetarman (Aug 9, 2015)

Paul Running said:


> Wondering if anybody has tried this product?
> 
> 
> 
> ...


Got one coming this week.


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## Hammerhands (Dec 19, 2016)

It looks like these go back a few of years, at least 2013.

Here's the non-LE version that has a metal cover, and glows.






AMT 12AX7WS | AMT Electronics official website


AVAILABLE NOW THIS PRODUCT USED BY MUSICIANS:




amtelectronics.com


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## Paul Running (Apr 12, 2020)

Hammerhands said:


> Here's the non-LE version that has a metal cover, and glows.


Yeah, on their website they mention that they went to the heat-shrink model to reduce cost but they are electrically the same.


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## diyfabtone (Mar 9, 2016)

rtomancini said:


> Hi
> Did some research and found this:
> -Video
> and a paper explaining in detail the concept of solid state triodes.


The paper is so poorly translated from the original I found it far less illuminating than hoped for.

I got one delivered today and will start trying it out in the V1 position of a few amps and see if it's got any value.


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## Paul Running (Apr 12, 2020)

diyfabtone said:


> The paper is so poorly translated from the original I found it far less illuminating than hoped for.
> 
> I got one delivered today and will start trying it out in the V1 position of a few amps and see if it's got any value.


Looking forward to hear your personal opinion of their product. I agree about the loss in translation of the paper however, some editing may help. The source info on the Fetron radio is interesting. Here is the Teledyne note:


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## diyfabtone (Mar 9, 2016)

I've had the LE version in the first 2 preamp stages of my YVM-1 for a week now and I have to say it's quite good. A bit cleaner with less noise, slightly darker (lack of noise may do that), and more headroom than the real AX7's I've had in the other 2 inputs. I have to try it in other guitar amps to understand what it can/can't do. It's different, but more in the way different tubes sound from each other than SS versus tube. I suspect if I dropped it in an audio amp I 'might' hear more contrast, but I don't use AX7 for audio.


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## oldjoat (Apr 4, 2019)

RCA had a similar unit back in the late 60's ....


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