AC4C1 tube option in V1

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somanytoys
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AC4C1 tube option in V1

Post by somanytoys » Mon Jun 10, 2019 11:31 am

I recently bought an AC4C1 (TV), and I was thinking about replacing the 12AX7 tube in V1 with a 12AT7 tube, that I'm using in another amp (Bugera T5). That tube works pretty well in the Bugera, which is a single tube gain stage, and I can still get a lot of distortion with the gain knob on the Bugera.

I've read some things about it, and some people have said that using either a 12AT or a 12AU in V1 works well, giving a broader, less compressed signal over to the 12AX7 in the next stage of the preamp, to allow it to compress and distort it more, for a smoother overall response.

I like amps having the ability to distort well on their own, especially for when I might use it as a standalone amp. But it's a small 4 watt combo, and I'm mostly using it with pedals, so it doesn't need the ability to scream too much on its own, more to effectively handle the different pedal sounds well that I pump into it. I'll have fuzz & OD, like a Range Lord and a Zenkudo for the harder pedals, and a Mini-mu, a Realizer (reverse reverb) and Count to 5 and half a Polymoon on the lighter side.

I know that I can just pop one in, try it & see, I was just wondering if anyone already had any experience with trying this, and how it worked, before I go in and spend the time to take the amps apart & swap the tubes. Then maybe have to do it all over again if I'm not overly happy about it in the end.
-David

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Re: AC4C1 tube option in V1

Post by Danley » Mon Jun 10, 2019 11:59 am

I haven't done the swap you're referring to - but changing to RFT AX7s totally fixed the AC4C1 for me (less headroom/earlier distortion, a lot more bass, less painful high-end, no speaker swap required.)
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Re: AC4C1 tube option in V1

Post by somanytoys » Mon Jun 10, 2019 1:20 pm

What are RFT's? I'm actually looking for more headroom.

The breakup is okay, but I want to be able to achieve more volume before it starts breaking up on its own, so that I have more room to play with pedals, but where I can still kick it in when I tank the gain knob for playing it by itself.

I'm thinking I'm going to go ahead and try this, especially since it worked pretty well in the single stage Bugeras. I know those amps are different beasts, but I would think it would work even better in the first position of the dual stage in the AC4C1. I also have a set of matched Tung Sol tubes to replace the originals, I just haven't opened that amp up yet.

I guess I'll find out, I hope it's worth the time. It's not THAT much time, but it's time, and twice as much if I have to end up swapping it back. Time wasted, but for good experience.

I'm still considering a speaker swap in that one. I have 2 AC4TVs (10"s), one with a Vintage 30 and one with a Greenback. I tend to like the sound of one with the Vintage 30 better overall, more bass and articulation, but I'm also thinking about going more in the alnico direction for the AC4C1. I'm definitely going that way with at least one of my 12" cabs.
-David

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Re: AC4C1 tube option in V1

Post by somanytoys » Tue Jun 11, 2019 5:33 am

Well, I ended up doing this, and more last night. I tried the amp with 3 different 12" cabs loaded with different speakers, one being the stock VX12 just for a 10/12 stock speaker comparison. It sounded much better with the other 2 speakers, so I decided to go ahead and open it up and change the speaker, and change the tubes while I was inside it.

It came loaded with China tubes. I swapped out V1 with a Groove Tubes Gold 12AT7, and swapped out the other 2 tubes with JJ's (12AX7 & EL84). And I swapped out the VX10 stock speaker with an 80th Anniversary Celestion G10 Vintage.

The 2 JJ tubes definitely gave me a much better sound overall, but I think that putting the AT in V1 gave me much more headroom before breakup, and because of the smoother first stage, a much more round and smooth distortion when I dimed the gain. I really think the speaker makes a huge difference as well, but all in all it's an entirely different amp now.

It was pretty late when I did this, so I didn't play it very loud. But I'm going to compare it to an AC4TVH & V112TV cabinet, with Tung Sol/Mullard tubes and a WGS G12C. I think it's going to hang in there pretty well, it may just a little bit shy on bass compared to a 12". And there's always the speaker out, which I'm going to try again, too.

I understand that Vox is/was trying to maintain a price point with these amps, and that's respectable and cool to keep them affordable, but it's amazing how nice these amps can be with better tubes and a better speaker, it's a pretty drastic improvement.
-David

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Re: AC4C1 tube option in V1

Post by 601210 » Tue Jun 11, 2019 5:59 am

somanytoys wrote:
Tue Jun 11, 2019 5:33 am
I understand that Vox is/was trying to maintain a price point with these amps, and that's respectable and cool to keep them affordable, but it's amazing how nice these amps can be with better tubes and a better speaker, it's a pretty drastic improvement.
Speakers I'll concede, though for most Vox models they release special editions with different speakers like Greenbacks/V-types/whatever.

But for tubes, I always thought a tube change is expected at some point for any tube amp anyways? I guess for some people it's more of a mod than routine maintenance, but I generally expect to like the tubes on a new amp about as much as I expect to like the strings on a new guitar.

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Re: AC4C1 tube option in V1

Post by Larsongs » Tue Jun 11, 2019 7:26 am

I recently did upgrades to my Vox AC-10C1. First a Celestion Greenback Spkr.. Then JJ Tubes.. Sounded much better.

But I wanted a sound like my AC-15 with Alnico Blue Spkr. Unfortunately Celestion's won't fit.. I opted for Webers Special Design for AC-10's which sounds close.. Then I tried Tung Sol's..... It sounds really good! Much like my AC15 but more compact & lighter.. Great for Practice, Studio Recording, Gigs & Travel...

I agree that some pretty simple minor Mods can take Amps to a whole new level & really improve their Sound...

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Re: AC4C1 tube option in V1

Post by somanytoys » Tue Jun 11, 2019 8:03 am

601210 wrote:
Tue Jun 11, 2019 5:59 am
somanytoys wrote:
Tue Jun 11, 2019 5:33 am
I understand that Vox is/was trying to maintain a price point with these amps, and that's respectable and cool to keep them affordable, but it's amazing how nice these amps can be with better tubes and a better speaker, it's a pretty drastic improvement.
Speakers I'll concede, though for most Vox models they release special editions with different speakers like Greenbacks/V-types/whatever.

But for tubes, I always thought a tube change is expected at some point for any tube amp anyways? I guess for some people it's more of a mod than routine maintenance, but I generally expect to like the tubes on a new amp about as much as I expect to like the strings on a new guitar.
Yes, the 15 & 30 watt versions of this amp have 12" greenbacks in them, but they're the larger, more expensive versions. This is just a cost cutting method for the smaller versions. This was a special edition, but it still came with a VX10.

Yes, depending on the amp maker and how cheap they decided to go with the tubes, or whatever your tube preference might be (brand or type), it's exactly like the strings that come on a guitar. So many tube types can be swapped for different effects, that's why I went with the 12AT7 instead of 2 12AX7's. I have a few AC4TVs, with different tubes in most of them, and while the differences are usually more subtle than different speakers, it makes enough of a difference that it's worth it.

That's one of the things I'm going to check out tonight. I put the new VX10 and the new China tubes from the AC4C1 into an AC4TV 10", and I'm going to compare it to my other one that I have JJ tubes and a greenback in. I think the difference is going to be pretty stark.
-David

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Re: AC4C1 tube option in V1

Post by somanytoys » Tue Jun 11, 2019 8:13 am

Larsongs wrote:
Tue Jun 11, 2019 7:26 am
I recently did upgrades to my Vox AC-10C1. First a Celestion Greenback Spkr.. Then JJ Tubes.. Sounded much better.

But I wanted a sound like my AC-15 with Alnico Blue Spkr. Unfortunately Celestion's won't fit.. I opted for Webers Special Design for AC-10's which sounds close.. Then I tried Tung Sol's..... It sounds really good! Much like my AC15 but more compact & lighter.. Great for Practice, Studio Recording, Gigs & Travel...

I agree that some pretty simple minor Mods can take Amps to a whole new level & really improve their Sound...
Yeah, that greenback sounded really good in the AC4TV, and the G10 sounds great with the AC4C1. I wouldn't mind getting something else, but I think my next speaker is going to be a WGS Blackhawk or Black & Blue 12" for cab, I really want an alnico or alnico style. I like the speakers in the small combos, and I can always plug those into the 12" cabs, so that's the way I'm going next.

I already had JJ's in a couple of my AC4TV's, and a set of Sovteks, and I really like the sounds of both of those. Slight differences, but the JJ's seem the loudest.

I've bought a few matched sets of Tung Sols, to replace in the AC4TVs and the AC4C1 when they need to be changed, but things are good for now.

It really is amazing how much of a difference those 2 things can make in some amps. These amps are really cool sounding, decently and convenient, with their size, they're perfect for those things you listed. And I have larger, 25-30 watt amps, when I need more wattage for a specific occasion.
-David

It's a boost booster, to boost your boost - it makes your tone much muchier.

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Re: AC4C1 tube option in V1

Post by Steadyriot. » Thu Jun 20, 2019 2:53 am

If you ever feel like swapping / experimenting you could also try a 12dw7 or the JJ EC832.
These are both a tube which houses one half 12ax7 and one half 12at7.
In the 12dw7 the first half is a 12ax7 and the second half is a 12at7.
The JJ EC832 is the other way around so a 12at7 for the first stage and a 12ax7 for the second.

Who knows, maybe it'll float your boat.
It seems you already like where you're at though..!
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Re: AC4C1 tube option in V1

Post by somanytoys » Thu Jun 20, 2019 10:30 am

That sounds pretty cool, especially to use for the preamps with a single tube - the best of both worlds in one.

I think I'd like the smoother side first, like I did with the 2 tubes in the C1, but it might be interesting to buy both & see.

Thanks for the info, I appreciate it.
-David

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Re: AC4C1 tube option in V1

Post by jorri » Thu Jun 27, 2019 6:21 am

Try a 5751. There is much less of gain drop at 70% vs. the 30% of an AU, but to me make a big difference to distortion. Much warmer useable distortion in my ac30. I had V2 and V3 though- the phase inverter switch was great but some might think it will not do much. Had the effect of more headroom, because the distortion was just more stable and not just 'mush' (this was a 'custom classic' and that can be the case with pedals)

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Re: AC4C1 tube option in V1

Post by somanytoys » Thu Jun 27, 2019 6:55 am

I'll have to take a look at those as well. I've been looking at some EC832s, that seems right in line with what I did with the C1 (12at, then a 12ax), and I really, really like the improvement in the sound. Cleaner cleans and (I find) a throatier, smoother distortion that can be further shaped with pedals.

I'm curious if it will do that same type of thing with the regular AC4TV using an EC832. I would tend to think so, since there is no master volume on that amp. It is an interesting sound, playing both of them, a smoother sounds out of the C1 and a little screamier tone out of the TV, but in a good way. I'll have to see if I miss that sound or rather the smoother sound from the TV.

I'll also have to look at a 5751, that's the 12au version? I haven't tried a 12au yet, but I would like to check it out and see how it works. I like having he ability of nice distortion from the amp, but I mostly use pedals so I usually don't need a hell of a lot of distortion from the amp, and those have a lot on tap with the 12ax. I find that the headroom works better than too much distortion, when I'm playing clean or letting a fuzz pedal do most of the work. Sometimes fuzz can blend really well with distortion, but with too much amp distortion, its' sometimes hard to get the different clean and fuzz sounds where one doesn't end up with giant volume spike or dip.
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Re: AC4C1 tube option in V1

Post by jorri » Fri Jun 28, 2019 7:10 am

somanytoys wrote:
Thu Jun 27, 2019 6:55 am

I'll also have to look at a 5751, that's the 12au version? I haven't tried a 12au yet, but I would like to check it out and see how it works. I like having he ability of nice distortion from the amp, but I mostly use pedals so I usually don't need a hell of a lot of distortion from the amp, and those have a lot on tap with the 12ax. I find that the headroom works better than too much distortion, when I'm playing clean or letting a fuzz pedal do most of the work. Sometimes fuzz can blend really well with distortion, but with too much amp distortion, its' sometimes hard to get the different clean and fuzz sounds where one doesn't end up with giant volume spike or dip.
Its supposed to be a 12ax7 equivalent, (possibly: the equivalent for USSR?) which is what its closest to in gain, i think. But it has different characteristics i don't know too much about. Lower gain doesn't really produce more headroom; it just means on your gain knob will now be at a lower value when its turned up higher. It will produce other things though; even more power amp distortion sometimes, but could change the response and other ways the preamp distorts. I think its worth trying out a couple, because the 5751 isn't in the 12a-7 series it just sounds a bit different hence why i tried because i didn't just want a lower gain equivalent as if i just turned down the gain knob (assuming that would happen, though haven't tried the lower gain 12a-7).. The distortion is warmer and more usable, but as said, is AC4 a single tube? Its probably a different position to where i put it?

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Re: AC4C1 tube option in V1

Post by somanytoys » Fri Jun 28, 2019 8:38 am

I don't know, you're still getting the same level of output from the preamp tube, just at a less distorted rate. If you turn the gain knob down, you're lowering the output of the preamp level into the poweramp. I've always thought of it like the difference in sounds that I get on a Blues Driver - with the gain down and the level up, I get a smooth, fat tone, vs turning up the gain and turning down the level (to make it unity volume), I get a heavily distorted tone, but if i didn't turn the level knob down to compensate for the gain increase, it's loud as hell because of the output level. What I'm assuming is, the type of tube acts like a static version of the gain knob on the pedal , set to whatever that tube would be rated at, and the gain knob on the preamp acts like the level knob on the pedal, pushing into a poweramp.

But I could be totally wrong, I don't know enough about the dynamics of electrical engineering. That's just how it seems.

It could just be sort of an aural illusion that there is more headroom. But whatever way it works, since there is less distortion to the same overall volume output of the amp, it seems to give some of my signals much more definition, that normally more distortion would blur or bury. I agree with what you said below, I feel like the lesser rated tube does seem to give me a more usable distortion. That distortion sounds pretty nice on its own, not quite as heavy and distorted as it would with an AX tube, but it will still get most of the way there when pushed. I also find that the sound really seems to take better with OD and fuzz pedals, than them going into quite so much drive from the preamp as a 12AX7.

That's an interesting description of the 5751, it definitely sounds like something I'd like. I read about it, it's supposed to be a military grade version of the 12AXY, which is a 70% distortion level. The 12AT7 that I'm using now is 60% gain, and apparently there is a 5965 version of it that's like 47%. The 12AU7 is like 20% distortion, I think, which might be good to use with some things.

I definitely want to start experimenting with some more of these preamp tubes and see what works best, especially with combinations in my bigger amps, with more stages. Yes, the AC4TV is single stage, one pre and power tube. The AC4C1 TV has 2 preamp and 1 power, and I put the AT tube in V1 of that one, and left the AX in V2. But it seems like the EC832 tube would mimic that setup in a single tube, and may work perfectly. I was wondering about that last night, as I was playing both of those amps, if I'd miss the roar of the AX in the AC4TV. Sometimes having different sounds from each amp is better than 2 similar sounds.

But I'm going to try it, it's not difficult to change the tubes (just a lot of screws for the case), so it'll be worth checking out. Once I buy some of these other tubes...
-David

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Re: AC4C1 tube option in V1

Post by Larsongs » Fri Jun 28, 2019 8:39 am

The Tube info is interesting.. Out of curiousity what kind of Speaker did you upgrade to?

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