New Voxes

JezWynd

TTBZ said:

Jota said:

The Mini SuperBeetle looks amazing!

Kinda reminds me of an old ladies tartan trolley bag.

If Marshall was marketing it, it probably would be.

ICBM

thermionic said:

I noticed that again the new AC30 has only two ECC83s. My AC15 has five - PI, tremolo and reverb take one each, which means two are in the single channel Top Boost preamp. So how can they make a Top Boost channel with two triodes?

They can't. The minimum number even for a single-channel AC30TB is five triodes - two gain stages, the cathode-follower tone stack driver, and the two halves of the PI. My guess would be that they've dropped the cathode-follower, which has also caused them problems with valve failures - that's why modern AC30s are fitted with Tung-Sols in V1 and V3 and a standard cheap - not failure-prone! - Chinese 12AX7 in V2. But without the cathode-follower, it won't sound quite right.

olafgarten said:

It's only 50w into 4 ohms

That's true - what's slightly odd is that the amp appears to have an impedance selector switch which implies some sort of matching, but the power ratings are what you would expect for a solid-state amp directly coupled to the speaker. So what is the switch for? Or is the spec wrong?

olafgarten said:

the G10 Vintage isn't available as a 4 ohm speaker. 

Unfortunately not. But even at 25W into 8 ohms, I'd guess it will be louder than the stock speaker by enough to make a useful difference. The G10 Alnico is even more efficient at 98dB, although admittedly it would cost half as much as the entire amp... but it would also look fantastic in the back of that little cab .

I fitted a Celestion 'Eight 15' to my AD15VT and it's just about doubled the perceived volume! I think I could probably get away with it at a small gig, and that's only 15W into a 95dB speaker.

thermionic

ICBM said:

thermionic said:

I noticed that again the new AC30 has only two ECC83s. My AC15 has five - PI, tremolo and reverb take one each, which means two are in the single channel Top Boost preamp. So how can they make a Top Boost channel with two triodes?

They can't. The minimum number even for a single-channel AC30TB is five triodes - two gain stages, the cathode-follower tone stack driver, and the two halves of the PI. My guess would be that they've dropped the cathode-follower, which has also caused them problems with valve failures - that's why modern AC30s are fitted with Tung-Sols in V1 and V3 and a standard cheap - not failure-prone! - Chinese 12AX7 in V2. But without the cathode-follower, it won't sound quite right.

That’s what I thought. I’ve read that the cathode follower makes up some gain lost in the tone stack, but also confusingly that it provides no gain (or even attenuates). Either way, I’m guessing there must be some sort of solid-state buffer replacing it. So effectively a hybrid amp? It does sound good in that demo though, fair play.

darthed1981

TA22GT said:

Very impressed with the sound from that Andertons video posted earlier. 

Must take a listen.

Ditto that AC30S1 sounded absolutely superb, GAS attack!

ICBM

thermionic said:

I’ve read that the cathode follower makes up some gain lost in the tone stack, but also confusingly that it provides no gain (or even attenuates). Either way, I’m guessing there must be some sort of solid-state buffer replacing it. So effectively a hybrid amp? It does sound good in that demo though, fair play.

The cathode follower provides no gain - it's actually very slightly less than unity, but not much - but what it does is provide a low-impedance source to drive the tone stack, which does help reduce the insertion loss and also evens out the frequency response - more bass and treble relative to the mid, basically.

The normal way of removing it is to simply drive the tone stack from the plate of the previous gain stage, rather than use a solid-state buffer, although I know of at least one amp that does use a high-voltage Mosfet transistor instead (one of the Marshall 50th Anniversary amps).

In my opinion the cathode follower is essential for the classic Marshall 'roar', but how much difference it makes to the Vox TB sound I'm not sure - I don't think I've heard one without.

jpfamps

ICBM said:

thermionic said:

I’ve read that the cathode follower makes up some gain lost in the tone stack, but also confusingly that it provides no gain (or even attenuates). Either way, I’m guessing there must be some sort of solid-state buffer replacing it. So effectively a hybrid amp? It does sound good in that demo though, fair play.

The cathode follower provides no gain - it's actually very slightly less than unity, but not much - but what it does is provide a low-impedance source to drive the tone stack, which does help reduce the insertion loss and also evens out the frequency response - more bass and treble relative to the mid, basically.

The normal way of removing it is to simply drive the tone stack from the plate of the previous gain stage, rather than use a solid-state buffer, although I know of at least one amp that does use a high-voltage Mosfet transistor instead (one of the Marshall 50th Anniversary amps).

In my opinion the cathode follower is essential for the classic Marshall 'roar', but how much difference it makes to the Vox TB sound I'm not sure - I don't think I've heard one without.

The DC coupled cathode follower will have significant non-linearity when driven into grid conduction, which is a likely explanation for the "sound" of this circuit, or indeed the Tweed Bassman.

A MOSFET source follower would reproduce this effect.

DC coupled cathode followers can be made more reliable by putting a silicon diode from the grid to the cathode.

https://www.tubecad.com/2007/04/blog0104.htm

The expense of doing this is negligible, but I've yet to see this in a commercial design (although we always include it).

impmann

TBH, from hearing that Anderton's vid, I'd say that it sounds closer to what an AC30 sounds like than most modern ones. Interestingly I think they have dialed the gain back in the design - I always found that the CC amps had too much and got a bit flubby when dimed.

It also made the AC15 sound terrible. I'm not surpised as I've never really been a fan (especially of the modern ones) but it just sounded awful.

Pricing sounds a touch odd, but then again if its 60% of the weight of a regular amp that counts for a MOUNTAIN of beans in this house. Honestly... I'm interested in playing through one.

ICBM

jpfamps said:

DC coupled cathode followers can be made more reliable by putting a silicon diode from the grid to the cathode.

https://www.tubecad.com/2007/04/blog0104.htm

The expense of doing this is negligible, but I've yet to see this in a commercial design (although we always include it).

[Thread hijack I know!]

Will that help with the usual cathode-follower failure, which is cathode-to-filament insulation breakdown in Russian (and occasionally JJ) 12AX7s? It doesn't look like it would but I may be missing something...

impmann said:

TBH, from hearing that Anderton's vid, I'd say that it sounds closer to what an AC30 sounds like than most modern ones.

Watched the video now. My instant first impression was that the Tele sounded like Mike Campbell's tone on 'Boys Of Summer', which as far as I know is a vintage AC30.

I was a bit disappointed by the lack of bottom-end though - real AC30s are actually surprisingly full in the bass, despite their reputation as quite a bright/midrangy amp. I compared my Mesa Trem-o-verb to one, and the Vox had noticeably *more* low-end. You can hear that in The Edge's sound too - which for me is the definitive AC30 tone. (Sorry, U2 haters .)

The AC15 actually sounds like it has noticeably more bottom-end in the video, but they said it sounded the other way round in the room, so it may just be the way they're mic'ed. (I don't find AC15s have enough low-end for me either.)

And an extension speaker jack which cuts off the combo speaker is *not* cool... it's a feature found mostly on low-end solid-state amps, not professional equipment. It reduces your connection options and introduces a potential failure point.

I'd want to hear one in person, but I'm still much more interested in the Mini Super Beetle .

EricTheWeary

I wonder how many people are looking at that S1 and thinking ‘that sounds like what I was after for a gigging/ jam night amp.’ I know it won’t be to everyone’s taste but there’s a sector of the market which that goes for the jugular of. 

TheMarlin

Why don't Vox make something new and interesting, instead of the same old stuff and gimmicky tinny sounding tiny pastiche amps?

Babones

I was hoping for a slightly larger/expanded MV Clean, that isn't the overpriced, overkill MVX150.

Grocer_Jack

Interested in the S1, but the best sounds I've got from AC30s is by jumpering TB and Normal channels. Still worth a try though. 

darthed1981

impmann said:

TBH, from hearing that Anderton's vid, I'd say that it sounds closer to what an AC30 sounds like than most modern ones. Interestingly I think they have dialed the gain back in the design - I always found that the CC amps had too much and got a bit flubby when dimed.

It also made the AC15 sound terrible. I'm not surpised as I've never really been a fan (especially of the modern ones) but it just sounded awful.

Pricing sounds a touch odd, but then again if its 60% of the weight of a regular amp that counts for a MOUNTAIN of beans in this house. Honestly... I'm interested in playing through one.

@impmann do you think it would make a decent indie/alt rock jamming and gigging amp?  Though I'm unlikely to do the latter it just seems so cool.

I thought it sounded superb.

ICBM

TheMarlin said:

Why don't Vox make something new and interesting, instead of the same old stuff and gimmicky tinny sounding tiny pastiche amps?

They do, quite a lot. The problem is that their market only seems to want something that sounds - or at least looks - like an AC30. The other problem is that they don't seem to be able leave anything to settle in, they're always changing stuff unnecessarily and cheapening it - although to be fair, this problem goes back to the Tom Jennings days.

I think the AD series digital modellers and the Tonelab stuff were definitely new and interesting - and actually sound good. The Nutube range is an interesting idea too, even if it doesn't necessarily produce very groundbreaking results. But I agree that the world probably doesn't need yet another not-quite AC30.

I would actually like to see them experiment more with plain solid-state - it's worth remembering that they produced probably the world's first more or less successful solid-state instrument amp, the 1962 T-60 bass head. OK, they weren't reliable (at all!) but if you've ever heard one in working order, they sound wonderful.

I do like the look of the MVX150 too, and it's not really overpriced if you compare it to a Yamaha THR100HD or a Quilter Aviator... assuming it sounds as good. And if they don't discontinue it after ten minutes.

impmann

darthed1981 said:

impmann said:

TBH, from hearing that Anderton's vid, I'd say that it sounds closer to what an AC30 sounds like than most modern ones. Interestingly I think they have dialed the gain back in the design - I always found that the CC amps had too much and got a bit flubby when dimed.

It also made the AC15 sound terrible. I'm not surpised as I've never really been a fan (especially of the modern ones) but it just sounded awful.

Pricing sounds a touch odd, but then again if its 60% of the weight of a regular amp that counts for a MOUNTAIN of beans in this house. Honestly... I'm interested in playing through one.

@impmann do you think it would make a decent indie/alt rock jamming and gigging amp?  Though I'm unlikely to do the latter it just seems so cool.

I thought it sounded superb.

Simply - yes.

An AC30 excels at that sort of thing.

darthed1981

I just loved the tone that Pete gets just with those open chords, could just have so much fun just thrashing through many of the songs of my youth!