1964 copper panel AC30 Top Boost with panel integrated Top Boost

[VintageCharlie]

Hi folks,

some time ago i was lucky enough to score this panel integrated Top Boost AC30 from 1964. It is one of supposedly less than a 100 copper panels with the integrated top boost. ( i would appreciate a hint towards the source of this info btw.)
It sounded nice as is, but once i changed to some old unbranded el84's it sounded phenomenal. At about 6 and above on the Top Boost channel with Treble at anywhere between 7-10 and Bass 7-10 it easly gets into Marshall Plexi style tones - with slightly less low-end, but with that soft, singing and spongy feel, incredible string definition even when driven hard and not the faintest hint of harshness. And of course, when you crank it past 6 on the brilliant volume, you get that hot fire-breating VOX drive thing. It is also a very quiet amp, less hum than my jtm-45/100 clone and no noticeable ghosting. I own 6 vintage amps or clones thereof, which many would consider iconic and the AC30 turned out to be my favorite (after the tube swap). Also the clean up with volume and the dynamic response of the amp are truly incredible. I know, everyone has been raving about it, but it is really an experience to try that yourself. It is a phenomenal blues amp that lets you explore all of those rolled back guitar volumetones, while still sounding dynamic and alive. For some reason it also sounds massive recorded. It sounds fatter and bigger than my big amps (DR504, OR120, JTM 45/100). I am sure the big amps have way more bass response, but to the ear, recorded the AC30 sounds "fatter" and just massive. I assume part of that is the compression, which helps it sound louder and part of it is some low mid frequency that i would call a "push", which is behind the AC30 and which i do not hear in any other of these amps - this gives it the feeling of punchyness and a very dynamic nature. If i had to choose just one amp, with a gun to my head, i think this might be it - it kind of does both - clean AND mean better than any of my other amps. Takes pedals perfectly as well. Harder to dial it in on the TB channel, but normal channel with pedals is an easy recipe for success Out of interest i compared it to a AC30HWH and while the HWH was good, it had a completely different feel, was quite a bit brighter and sometimes harsh. I wonder, if this can be done right with modern parts, when following one specific example closely.

At some point i will try to clone it (minus the vibrato channel) and add an EF86 channel instead.

Here are 2 clips i did. One is with an ES335 copy (Yamaha SA-1000) and the other one is a 62 hot rod Fender Strat, no pedals. That is recorded DI and with an added Impulse response of a 2x12 cab with greenbacks. (I prefer these over the alnico sound). There is no EQ or other post processing, not even a room sim. If you would a room IR, it would sound absolutely massive.

https://soundcloud.com/vintagecharlie/1 ... t-es335-sa
https://soundcloud.com/vintagecharlie/1 ... oost-strat

[pdf64]

Nice!
Does the vib-trem work properly?

[VintageCharlie]

Nice!
Does the vib-trem work properly?

Yes, it does work as good as it can I am not a big fan of the vib/trem. The vibrato sounds nice, but it is very subtle and the speed range is also narrow - hence it is quite a bit limited. One has to admire how well Magnatone did this in comparison.
And the tremolo is ok if you play it with the amp clean, but driven it has that type of trem which i personally do not like - that's the one, which makes the signal distort/fizz in and out, instead of smoothly modulating the volume. There are also some tremolo pedals that do this. In contrast the bias tremolo on a Supro clone sounds godly. But that is of course subjective, as there are surely lots of folks, who enjoy this sound.

I wondered myself, if it is supposed to sound like that and finally found a couple of videos on youtube that demonstrated vib and trem on all settings - mine sounds pretty much exactly the same. What i was not convinced about first was that there is a very small difference in the preset vib/trem speeds.
If there is interest, i can make a recording of all the settings at some point for reference.
The vibrato channel also does not behave nicely with pedals. It sounds nice on it's own without the vib/trem effect enabled though.

What i find a bit ironic is that a big part of the VOX AC15/AC30 amp design is probably due to VOX's decision to include the complicated onboard vib/trem effects - so the amp itself had to be simple and they ended up with el84's to better fit everything in the box (at least that is what i have read. This is a great article that touches that topic: https://www.stevesamps.co.uk/?page_id=287). Thereby the AC15 and therefore also the AC30 recipe has a few happy accidents in it due to other design considerations.

[Colossal]

Very nice! I see yours has Albion transformers. Do you happen to have B+ voltages? Do you have Alnico Blue speakers in the cab, but just preferred the IR of Greenbacks for your DI recording?

Thanks.

[VintageCharlie]

Very nice! I see yours has Albion transformers. Do you happen to have B+ voltages? Do you have Alnico Blue speakers in the cab, but just preferred the IR of Greenbacks for your DI recording?

Thanks.

Yes, albion throughout. I have another one just like that actually (also with albion), looks more tatty and sounds slightly different (slightly softer and sounds as if the focus of the frequencies would be slighter lower than on this one), but also spectacular. I have no B+ measurements yet, but can follow up on that on both of these amps.

The cab is also from 1964, from what i know, purchased together with the head by the original owner. It does indeed have original silver alnicos in good shape. I did the recording in my flat, so i went with silent recording and an IR. But i have to admit, at least when going with IR's, i prefer Greenbacks. In the room the silver alnicos sounded sweet - it also did not feel like they were missing in the bottom end. Maybe the closed back cab helps there.

[Colossal]

I have no B+ measurements yet, but can follow up on that on both of these amps.

No worries, I just wanted to see if you had them handy. It is hard to get real data on these amps. Most sources I've seen say B+ for the early AC30s was low at 310-320VDC, post rectifier (with 117VAC on the primary).

The cab is also from 1964, from what i know, purchased together with the head by the original owner. It does indeed have original silver alnicos in good shape. I did the recording in my flat, so i went with silent recording and an IR. But i have to admit, at least when going with IR's, i prefer Greenbacks. In the room the silver alnicos sounded sweet - it also did not feel like they were missing in the bottom end. Maybe the closed back cab helps there.

Fantastic to have the original Silver Alnicos! I really like 20W Greenbacks, so that's why I was asking. I know some guys use a blend of a Greenback or 30W G12H Anniversary with a Blue as well.

[Mark]

The Albion transformers are great at that Plex meets Vox thing. I played one years ago and loved it, the same as the pictured one in fact.

[Alnico]

No worries, I just wanted to see if you had them handy. It is hard to get real data on these amps. Most sources I've seen say B+ for the early AC30s was low at 310-320VDC, post rectifier (with 117VAC on the primary).

I have three JMI AC30s, with Albion, Woden and Parmeko transformers. Might be a while before I can dig them out for measurements though.

VintageCharlie - nice amp.

[Colossal]

No worries, I just wanted to see if you had them handy. It is hard to get real data on these amps. Most sources I've seen say B+ for the early AC30s was low at 310-320VDC, post rectifier (with 117VAC on the primary).

I have three JMI AC30s, with Albion, Woden and Parmeko transformers. Might be a while before I can dig them out for measurements though.

VintageCharlie - nice amp.

Wow, nice collection That would be extremely cool! Take your time, but hurry up!

[VintageCharlie]

The Albion transformers are great at that Plex meets Vox thing. I played one years ago and loved it, the same as the pictured one in fact.

Yes, this took me by surprise after having the impression an AC30 is all jangle and chime Do you feel the OT is a big part of that? I have asked about this on other forums, but usually even the guys who do have experience with the vintage originals with various transformers say that it is difficult to judge the role of the transformer alone, as lots of other things have variables/tolerances etc.

[VintageCharlie]

No worries, I just wanted to see if you had them handy. It is hard to get real data on these amps. Most sources I've seen say B+ for the early AC30s was low at 310-320VDC, post rectifier (with 117VAC on the primary).

I have three JMI AC30s, with Albion, Woden and Parmeko transformers. Might be a while before I can dig them out for measurements though.

VintageCharlie - nice amp.

Yeah, really great to have all 3 to compare - this was my first thought after hearing this one, i wanted to know how the ones with the other transformers sound.
I am very interested in the OT's tonal role in this circuit. I read various differing statements on various forums, but there does not seem to be a consensus due to many other variables in the amps. I've read albions are supposedly brighter sounding and are best suited for good overdrive tones. Wodens are supposedly darker. There is a clip of Johan Segeborn running a grey panel AC30 TB through its paces (https://www.youtube.com/watch?v=7110Ru9BP7w&t=220s) with similar settings as what i use with my amp and it also sounds glorious. Similar in many ways, but actually really a bit darker than mine (at least judging from the recording, which is always tricky, as it could be just miking).

Anyway, i would appreciate any input on your observations regarding differences between the amps that might be connected with the output transformers, if you find the time to write that down, of course.

[pdf64]

When comparing vintage amps, consider the potential effects of variance of every part, both in regard of their original tolerance to nominal for value and parasitics, and then subsequent change due to age / use.
eg perhaps some models with Albions seem brighter due to coincidentally, the batch of 220k resistors that happened to be used then were more prone to value drift, or the Tropyfols more prone to dc leakage.

[Mark]

Okay, this is what I know about the output transformers from experience. Using the same amp, the Mercury Magnetics Haddon transformer was the brightest, followed by the Mercury Magnetics Woden transformer which was quite similar to the stick Parmeko transformer.

In a small recording studio I played an super twin red panel AC-30 which I ASSUME had Albion transformers. I was using a PRS guitar which have high output pickups. It had a Vox meets Marshall sound, needless to say it blew me way.

I asked Patrick at Mercury Magnetics why this Vox sounds the way it does and he said the Albion transformers impart that timbre.

[VintageCharlie]

Okay, this is what I know about the output transformers from experience. Using the same amp, the Mercury Magnetics Haddon transformer was the brightest, followed by the Mercury Magnetics Woden transformer which was quite similar to the stick Parmeko transformer.

In a small recording studio I played an super twin red panel AC-30 which I ASSUME had Albion transformers. I was using a PRS guitar which have high output pickups. It had a Vox meets Marshall sound, needless to say it blew me way.

I asked Patrick at Mercury Magnetics why this Vox sounds the way it does and he said the Albion transformers impart that timbre.

I find this very interesting, of course, none of that is "scientific", but this is not the first source claiming that the Albion OT adds to that Marshall thing with these AC30's. Maybe at some point i will comopare some OT's te check it out in one amp. The two TB AC30's i have both have the Albion and both gradually do become a fire breathing Marshallesque monster above 5 on the gain (with the right EQ settings of course, as it is also easliy possible to make them much brighter/scooped if desired).

[pdf64]

I acknowledge I’m a ‘doubting Thomas’ regarding these things, but I recall wandering into an ‘upstairs room in a local pub’ gig over 20 years ago, by a blues rock band that totally altered my approach to guitar tone. The guitarist was using a Strat into a cranked vintage AC30, that sounded jaw droppingly good, ‘out Marshalling the best Marshall tone’ and sat perfectly in the band mix.
After that I gave up with master volume rigs and dusted off my old AC30 (Wodens), but I never quite got that tone; maybe his had Albions?