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Discussion Starter #1
My friend RG Keen (www.geofex.com) has a passion for the mid-60's-era solid-state Vox amps, Maybe it can be chalked up to the Beatles. Maybe it's just sympathy for an undeservedly maligned series of amps that jettisoned tubes before Fender was ready to. RG has posted a number of Vox-related circuits and repair ideas on his site, and recently sent me not only his repair/maintenance guide for solid-state Vox amps (recently "micro-reviewed" in Vintage Guitar) but also generously sent me a circuit board for a replica of the 700 series preamp, discussed here: Vintage Amps Bulletin Board • View topic - 700 Series Preamp Project and here: The VOX Showroom - Vox 7120 Amp - A Look Under the Hood - Preamp Circuit

The preamp circuit is a two channel amp with T/M/B controls on each channel as well as reverb, tremolo, and distortion. Anyone have any experience, good or bad with that era of Vox amps? I seem to recall the other guitar player in my high-school era band having a Vox Berkeley or some related model, and I thought it sounded pretty decent. Nice and crisp..
 

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I have never tried old Vox amp but I do have a Vox Pathfinder 15R that I like. The reverb isnt that great but it's a great sounding amp that sounds huge though a proper cab.
 

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Theirs vr series with hybrid technology that became the valvetronix amps are good.

Vr-15 and Vr-30r.

Super cheap. I own three vr-15. Bought for 65-50-85 dollars respectively.

Sound huge through an ext cab.
 

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I also own a pathfinder 15r, they get pretty decent reviews online. I like mine a lot, and it's great for a little jamming amp.

I think the pathfinder is a bit of an oddity as it's cheaply designed with cost efficienct components but came together as a fully usable amp. For some reason, people just love them.
 

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Discussion Starter #5 (Edited)
The schematic for the Pathfinder suggests it is a nice little meat-and-potatoes (fish-and-chips?) amplifier.

Of course, just about any amplifier that uses a spring reverb pan, and doesn't provide a big enough cab to include a long-spring pan, will be a bit less than transcendant in the reverb department. It'll "work" but you won't be raving about it. I have the same deal on my Fender Champion 110 (same as a Frontman 25R)

Interesting tidbit is that the reverb send is tapped from a point after the tone controls but before the tremolo, and mixed in after the tremolo. So, the two effects are produced in parallel, and combined like two versions of the original signal. In some amps, the two effects are produced in series, such that tremolo is then reverbed.
 

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I have never tried old Vox amp but I do have a Vox Pathfinder 15R that I like. The reverb isnt that great but it's a great sounding amp that sounds huge though a proper cab.
I also have a Pathfinder 15R. I once ran it through an Oversized Stone Age cab with a 1x12 Scumback. OMG did it sound good.
 

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I love my little Vox DA5. For such a little amp it has a lot of power. I keep it at the cottage so I don't have to tote more equipment then necessary! It's like Christmas morning all over again when I play it! So many different settings on it. It even has a wah wah setting which is a lot of fun!

This was my very first real amp, it's a keeper. :)
 

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Discussion Starter #9
Used to have one of the Vox hybrid amps. Blech. Didn't like it. I still have two Pathfinder 15R's, though. They don't beat out any of my tube amps in a head-to-head comparison, but for something really light and portable that sounds good clean and has a nice tremolo, they can't be beat at under $100 brand new.
"Hybrid" in which way: solid-state front end and tube power stage, or solid-state most of the way but for a preamp tube in the front end?
 

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Discussion Starter #11
If it's a 12AX7 then it has a solid-state power stage and is using the tube to yield preamp-stage overdrive/coloration. Those can yield respectable overdrive tones, but tend to yield less satisfying sound than tube power stages, whether it be a Vox amp or some other brand. If it yields the sound one seeks, who am I to knock it, but essentially it is a solid-state amp with a tube stompbox built in.

One of the considerations about such amps is that the solid-state circuitry will usually not want more than +/-25V (and often less) where the tube amps one is trying to mimic are going to be running the 12AX7s at much higher voltage. Such "starved plate" uses of preamp tubes can be appealing, but usually best tones are obtained with higher voltages than one is likely to find in a SS amp.
 

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I just saw one of these the other day. Great for the back. Anyone try one?

MV50


 

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Discussion Starter #13
I guess Vox is trying to give Quilter and Crate a run for their money, eh?

I haven't tried any Class D guitar amps, although I can't imagine they sound any better or worse than A/B solid-state amps. Just lighter to carry around.
 

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Discussion Starter #15
Vox is not the only company to use that strategy (not that this is any excuse). I suppose many players, if given a choice between using a couple of diodes to produce clipping in the preamp, and using a tube to do the same, would likely say "Gimme the tube". But I'm sure you are well aware that there are players who like all-tube amps with master volume controls, some who decline any tube amp with a master volume, and some who don't mind some kinds of master volume (e.g., post-inverter), but eschew masters situated in the preamp.

So it all depends on how that lowly little 12AX7 gets used, and how the design intends to extract that harmonic content we all know and love. If the schematic I'm looking at is an indication, the tube is being "starved" (i.e., run at a much lower voltage than normally used), so I'm guessing it yielded a rather raspy sound.
 

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Sometimes, using diode "properly" can sound better than using tubes "improperly".
Yes, I agree. I think quite often the inclusion of a 'tube' somewhere in the circuit is a marketing thing as much as a sonic thing.

There's some amp out now (BluGuitar, I think) that uses one of those new nanotubes in it's configuration and they seem to be purposely blurring the fact that it is a preamp tube and not a power tube - I guess because there is so little experience with this type of tube. It doesn't seem that obvious on their literature that it is a preamp tube. Or maybe it's just the customers that are confusing it and posting things and that's muddying the waters.
 

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Discussion Starter #19
I don't know if you remember their amplifier ad campaign in the 80's, but A/DA used to have ads on the back cover of Guitar Player with a slogan of "REAL amps glow in the dark" and a snapshot of a glowing tube through the grill on the top. Of course, at that time, few of us would have immediately thought "How the heck do you fit a tube amp into a 1U or even 2U rack space?". We would not have thought "I'll bet they're only using tubes on the front end".

Recently, my friend Steve Daniels from Small Bear Electronics sent me an Eleca tube overdrive pedal to test out that he was considering carrying. It didn't sound bad, but wasn't especially inspiring or different. But what was conspicuous to me was that tube it contained seemed to warm up instantly when the power came on. I took the unit apart in order to see what modding possibilities it held, and found that there were two small red LEDs under the 12AX7. The LEDs would come on immediately, shine through the 12AX7 so that a red glow was visible through the top grill, and create the impression that the tube was functioning, before the tube had actually warmed up.

There is undoubtedly a certain cachet to guitar gear having tubes. Sometimes people don't seem to really care what those tubes do, as long as it has them...somewhere. And as the Eleca pedal illustrates, sometimes consumers don't even feel they need to know how tubes normally work.
 
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