'All tube' may not mean all tube...

radiocaster

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Trying to keep this about ad copy and possible misrepresentation, my Micro Terror is a tube pre and SS power amp. I have seen them called tube amps (not by the manufacturer), but if I wrote an ad for it, I’d call it a “hybrid” amp.
I would call it hybrid as well, but the pre-amp is also hybrid.
 

red57strat

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Fender's marketing for the Super Champ XD boasted a 12AX7 as a preamp tube. Technically it's a preamp tube (it's before the power stage in the circuit), but practically it's not because the preamp on these amps is a sound engine microprocessor (100% digital modeling). The 12AX7 tube is a phase inverter for the pair of 6V6 power tubes.
Half of the 12AX7 in a Super Champ XD is the phase inverter. The other half is used in the preamp. Still, it's a hybrid amp.
 

bigben55

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I've had a big bunch of amps over the years. FWIW, I disagree with 5Y3 rectified amps as having a slower response in general. That 'sag" is real, but it's more a tone thing. It makes the amp SOUND different, not react slower. My 5Y3 rectified Valvetrain Saratoga with a Scumback H75 is one of the most immediate, responsive amp ive ever played. Notes are jumping out of the speaker before you're seemingly done picking them. I did notice the amps response being "faster" when I got the Scumback.
 

burntfrijoles

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I have a PRRI SE w 12” Jensen. It’s all tube including the rectifier. However I don’t use the onboard spring reverb or tremolo as I prefer the Strymon Flint for both.

I’ve never bought an amp without being fully aware of the specs. I’ve purchased hybrid amps but was fully aware. However I did almost buy an amp that I thought was hand wired before learning it was not (Thanks to a TDPRI poster who clarified it for me.)
 

wabashslim

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So, regarding my 6AQ5 version Musicmaster Bass amp: is it all tube or not? Because the phase inverter is not a tube, but a transformer. What say you?
Transformers aren't active (amplifying) devices, so if that's the only issue in the signal path then yes, your amp can be considered all tube (not familiar with MM bass amps).
 

wabashslim

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Half of the 12AX7 in a Super Champ XD is the phase inverter. The other half is used in the preamp. Still, it's a hybrid amp.
The line between "preamp" & "driver" is a flexible one but I consider the 1st 12AX7 in the SCXD & the Princeton (practically identical circuits) a "driver". The job of the preamp - processing the sound - is finished at that point (note the line-out buffer) and ready for amplifying for line-level work. Since the cathodyne PI has a gain of less than 1, as do all cathode-driven signals, the driver is necessary to give the PI something to chew on & spit out. It's part of the output section, not the preamp. But, I wouldn't stand on a podium & debate that.
 

Wound_Up

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You often see tube amps described as 'all tube'; but what does that mean? When you delve further into the technicalities many tube amps are actually a hybrid of tube and solid state working together . The initial gain stage of the overdrive is SS. Digital Reverb has mostly replaced the spring tank, same with tremolo. with a MOSFET in the gain stage, some pedals inc. overdrive will react differently. It may explain also why people cant hear much or any difference in sound quality between SS and Tube amps. SS amp technology has improved a lot of course.
Genuine all tube amps, tube driven overdrive, spring reverbs, more tubes in the circuit, are still out there, if you can pay the extra, but they sound superb...

They've been doing hybrid amps for 50 years by now. Why harp on it now?
 

11 Gauge

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What's kinda funny to me is that some folks now equate all tube as being something you can only get as boutique or top dollar, and yet I have a Marshall Origin 20H with an all tube pre (including the effects loop) and all tube power, and it cost me less than half a grand.

Even my little EVH 5150III lunchbox has a tube effects loop. It does use a mosFET for a source follower to the tone stack, but that's just to properly drive it, and IMO has zero tonal effects. If anything, plate loading the tone stack from the prior triode stage would actually screw things up audibly worse! Long story short is that the mosFET was a necessity, otherwise the amp would need 7 preamp tubes instead of the 6 that it has.

Regarding tube rectifiers, while they will indeed cause effects like sag, IMO they are still diodes, whether they are tube or SS. Point being that they aren't actually amplification devices. If you really want the sag effect, you can actually replace SS diodes with something that will give you the same effect as a tube - check out the Weber Copper Cap stuff as one example. I had one in a '79 DR to actually lower the B+ vs. a GZ34 tube recto (it was equivalent to a 5V4, IIRC), and it worked perfectly, IMO.

What's also funny to me is how some folks will think that their 'advertised as all tube amp that actually isn't' will sound good until they discover that it's not actually all tube. So it seems to me that it's not really an issue of the amp not being designed to sound good, regardless of whatever tech was used.
 
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JIMMY JAZZMAN

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I like sag, it sounds organic to me. Presently waiting on the new Harmony amps to come out.
Yes, they are "all tube" with reverb and tremolo. Coming out this fall.
 

printer2

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The line between "preamp" & "driver" is a flexible one but I consider the 1st 12AX7 in the SCXD & the Princeton (practically identical circuits) a "driver". The job of the preamp - processing the sound - is finished at that point (note the line-out buffer) and ready for amplifying for line-level work. Since the cathodyne PI has a gain of less than 1, as do all cathode-driven signals, the driver is necessary to give the PI something to chew on & spit out. It's part of the output section, not the preamp. But, I wouldn't stand on a podium & debate that.
The 'driver' is not transparent. Is it a preamp tube? I say yes as it has the same resistor values as a preamp section (1.5k and 100k resistors). So it is adding the same signal modification as a 'regular preamp' triode does, just 1X rather than 2X.
 

Masmus

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Does it make a difference if the rectifier is solid state or tube?
50 years ago the only thing that any body talked about were if it had any tubes. later you got SS pre and power tubes like an early Peavey Classic or Mace. In the last 40 years I've never heard anyone call a 70's marshall anything other than all tube. They didn't have tube rectifiers and 99/100 people would never have even thought of the rectifier.

The Vox AC10C1 mentioned before while having some SS circuitry does in fact use 12ax7 tubes in the pre amp and EL84 power so I do believe most people wouldn't have a problem with the all tube description.
 
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Nogoodnamesleft

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To me "all tube" is an audio path through which the active devices in each amplifier stage (pre amp stages and power amp stages) are tubes.

Clipping diodes, solid state rectifiers, etc. - affect the tone but the actual amplification of the signal from the string generating an induced signal in a coil to the sound we hear coming out of a speaker is processed through multiple stages that are all tube driven.

Inductors (as in transformers), capacitors, resistors - all passive devices required to do what they do to the tubes to make them work.

Some might argue the clipping diodes contravene such logic, since they are SS and modify the signal. But chopping off the peaks of a signal isn't the same as amplifying.

Just my EE 2 cents.
 

RetiredUnit1

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Well you can always build your own, I do. And I'm a programmer. Was. Retired. I learned a heck of a lot just in online forums. Just getting ready to build a Fender 59 bassman, and a Marshall 18w TMB. I've built about 35 amps in the past 25 years.
 




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