AC30CC preamp tube layout

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AC30CC preamp tube layout

Postby stevewire on Thu Dec 17, 2009 4:08 pm

Hello. I am having a little trouble locating information about the preamp tube layout for the AC30CC2. I am trying to figure out which is V1 and which is the PI. I've come across a few schematics of which I can't make heads or tails. I also did a search on this forum. I find the search function here to be lacking. I have to imagine that this information must have been covered at another time. Could someone help me please? Thank you.
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Re: AC30CC preamp tube layout

Postby Grog on Fri Dec 18, 2009 6:06 pm

steve,

V1 (normal channel and first stage top boost) is towards the edge of the chassis R/Hand side looking from the front v2 (second stage top boost) in the middle and V3 (PI) is closest to the centre of the amp furthest left looking from the front.
AC30 Super Twin(1963) S/N 9952N Rear Panel TB Head, Dynamic Bass (1968) #1153, AC30CCH, V212BN 1 x Alnico Blue 1 x Wharfdale, VBM1, AC4TV, Marshall JTM312, Gibson 347(1987), Les Paul Custom, US Fender Telecaster and Stratocaster, CIJ Jaguar HH.

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Re: AC30CC preamp tube layout

Postby P-Dawg on Fri Dec 18, 2009 7:26 pm

Grog wrote:steve,

V1 (normal channel and first stage top boost) is towards the edge of the chassis R/Hand side looking from the front v2 (second stage top boost) in the middle and V3 (PI) is closest to the centre of the amp furthest left looking from the front.


That's why my CC sounds so good. From outboard to inboard are an RCA 12AX7, a military Sylvania 5751, and a Hytron 7025 in the inboard position. Also a recently acquired Mullard GZ34. I've set the filtering on vintage and the output on warm. I use the top boost for clarity with a measure of normal for bottom end grunt.

Got a nice pair of Jensen P12R reissues I might try out in it too.

Hey. It only took a year to figure this all out. :cheers:
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Re: AC30CC preamp tube layout

Postby Grog on Fri Dec 18, 2009 8:26 pm

P-Dawg wrote:
Grog wrote:steve,

V1 (normal channel and first stage top boost) is towards the edge of the chassis R/Hand side looking from the front v2 (second stage top boost) in the middle and V3 (PI) is closest to the centre of the amp furthest left looking from the front.


That's why my CC sounds so good. From outboard to inboard are an RCA 12AX7, a military Sylvania 5751, and a Hytron 7025 in the inboard position. Also a recently acquired Mullard GZ34. I've set the filtering on vintage and the output on warm. I use the top boost for clarity with a measure of normal for bottom end grunt.

Got a nice pair of Jensen P12R reissues I might try out in it too.

Hey. It only took a year to figure this all out. :cheers:


My set up is similar to P-Dawg, V1 12ax7, V2 12au7 low gain 17 as opposed to 100, P-Dwags 5751 is lower but only slightly, V3 12ax7 all valves are Mullards.

Ditto for use top boost for clean blend the normal for grunt and then a EH Nano Linear Power Boost if I need more.
AC30 Super Twin(1963) S/N 9952N Rear Panel TB Head, Dynamic Bass (1968) #1153, AC30CCH, V212BN 1 x Alnico Blue 1 x Wharfdale, VBM1, AC4TV, Marshall JTM312, Gibson 347(1987), Les Paul Custom, US Fender Telecaster and Stratocaster, CIJ Jaguar HH.

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Re: AC30CC preamp tube layout

Postby P-Dawg on Sat Dec 19, 2009 5:46 am

Grog wrote:
P-Dawg wrote:
Grog wrote:steve,

V1 (normal channel and first stage top boost) is towards the edge of the chassis R/Hand side looking from the front v2 (second stage top boost) in the middle and V3 (PI) is closest to the centre of the amp furthest left looking from the front.


That's why my CC sounds so good. From outboard to inboard are an RCA 12AX7, a military Sylvania 5751, and a Hytron 7025 in the inboard position. Also a recently acquired Mullard GZ34. I've set the filtering on vintage and the output on warm. I use the top boost for clarity with a measure of normal for bottom end grunt.

Got a nice pair of Jensen P12R reissues I might try out in it too.

Hey. It only took a year to figure this all out. :cheers:


My set up is similar to P-Dawg, V1 12ax7, V2 12au7 low gain 17 as opposed to 100, P-Dwags 5751 is lower but only slightly, V3 12ax7 all valves are Mullards.

Ditto for use top boost for clean blend the normal for grunt and then a EH Nano Linear Power Boost if I need more.


In that respect it was nice to have the Rose Morris AC30 around here so I could hear what one's supposed to sound like when working properly. Now I know what I'm looking for. :cheers:
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Re: AC30CC preamp tube layout

Postby stevewire on Sat Dec 19, 2009 3:23 pm

Thank you guys. The information is much appreciated. Now I need to figure out where to get some NOS 12AX7s that I can afford and that work well with the CC.
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Re: AC30CC preamp tube layout

Postby Grog on Sat Dec 19, 2009 4:25 pm

I've always found ebay to be good in the uk anyway, especially for pulled tube ie 6aken out of working equipment so still testing to a usable state sometimes as new or lower gain alternatives (12au7, 12ay7's, ECC88's, CV4024's) which can be quite a bit cheaper. Never paid more than £9 for a tube at that was for a cv492 (miltary 12ax7) NOS probably a Mullard. If you see a 9 pin pre-amp tube with a designation code you don't know look it up, there's a site called the valve museum, and just see what it does if its a double triode then you could well be in business, just look for the gain/amplification factor often written as a u with a little tail on it.
AC30 Super Twin(1963) S/N 9952N Rear Panel TB Head, Dynamic Bass (1968) #1153, AC30CCH, V212BN 1 x Alnico Blue 1 x Wharfdale, VBM1, AC4TV, Marshall JTM312, Gibson 347(1987), Les Paul Custom, US Fender Telecaster and Stratocaster, CIJ Jaguar HH.

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Re: AC30CC preamp tube layout

Postby stevewire on Sun Dec 20, 2009 2:56 pm

Grog wrote:I've always found ebay to be good in the uk anyway, especially for pulled tube ie 6aken out of working equipment so still testing to a usable state sometimes as new or lower gain alternatives (12au7, 12ay7's, ECC88's, CV4024's) which can be quite a bit cheaper. Never paid more than £9 for a tube at that was for a cv492 (miltary 12ax7) NOS probably a Mullard. If you see a 9 pin pre-amp tube with a designation code you don't know look it up, there's a site called the valve museum, and just see what it does if its a double triode then you could well be in business, just look for the gain/amplification factor often written as a u with a little tail on it.


This seems to be an area that is filled with much mystery and myth. I am curious about the low gain alternatives, but I am not sure they will be appropriate for me. I'd like to find some regular 12AX7s that I am happy with before I start exploring and investing in the low gains. From time to time, I look on Ebay, but I am not sure what is worth it or not. I'd like my first venture into NOS preamp tubes to be characterized by most bang for my buck. I want it to be something that I can actually hear the difference well rather than it be so subtle that I regret my investment. At this point I don't want to already experience the law of diminishing returns.
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Re: AC30CC preamp tube layout

Postby Grog on Sun Dec 20, 2009 4:00 pm

For whatever style you play may not wan't/need to go the low gain route, I found it makes the top bosst and normal channels have different charactaristics and was what I was after so it works. If not then just get some normal 12ax7's or CV492's a miliatry ruggedrised version maybe cheaper, but many folks are happy with current production JJ's in their Vox, I've not tried them so I can't comment. All can say is to me the stock Sovteks that mine came with sounded harsh and brittle compared with the Mullards I have in there now both in my CCH and in the AC4 I got recently especaially noticable in the ac4 the Mullards really took the boxy sound out of the amp. I happened to go on ebay anmd saw two untested Mulaard el84'S WITH 13 mins left at 16£ so whacked £20 and for £19 plus psotage ended up with the pair, 63 and 64 Blackburn codes. Turns out they came out of a closed down physics lab, popped them in the AC4 and wow, superb sound, one does sound tighter than the other so they don't all sound the same anyway.
AC30 Super Twin(1963) S/N 9952N Rear Panel TB Head, Dynamic Bass (1968) #1153, AC30CCH, V212BN 1 x Alnico Blue 1 x Wharfdale, VBM1, AC4TV, Marshall JTM312, Gibson 347(1987), Les Paul Custom, US Fender Telecaster and Stratocaster, CIJ Jaguar HH.

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Re: AC30CC preamp tube layout

Postby P-Dawg on Sun Dec 20, 2009 7:26 pm

Grog wrote:For whatever style you play may not wan't/need to go the low gain route, I found it makes the top bosst and normal channels have different charactaristics and was what I was after so it works. If not then just get some normal 12ax7's or CV492's a miliatry ruggedrised version maybe cheaper, but many folks are happy with current production JJ's in their Vox, I've not tried them so I can't comment. All can say is to me the stock Sovteks that mine came with sounded harsh and brittle compared with the Mullards I have in there now both in my CCH and in the AC4 I got recently especaially noticable in the ac4 the Mullards really took the boxy sound out of the amp. I happened to go on ebay anmd saw two untested Mulaard el84'S WITH 13 mins left at 16£ so whacked £20 and for £19 plus psotage ended up with the pair, 63 and 64 Blackburn codes. Turns out they came out of a closed down physics lab, popped them in the AC4 and wow, superb sound, one does sound tighter than the other so they don't all sound the same anyway.


There's a university near here and the physics department has a huge collection of military surplus tubes stashed away that were part of a DoD project to assist research people in the late fifties through the late sixties. They won't part with them at present and they won't let me in the storeroom to see what they've got. :POd: :POd: :POd:

Sorting out the glassware on my AC30CC2 took a little bit of cut and try but it was well worth it. I managed to reduce the background noise quite a bit, improved the clarity and definition, and took some of the rough edges off it. I even sold the EH EL84s to a guy and I installed a recently acquired used/serviceable Mullard GZ34 which was not necessary but a nice addition. Good tubes in these amps make them wake up and stand to attention. :cheers:

Here's the Rose Morris alongside my own amp.

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Re: AC30CC preamp tube layout

Postby stevewire on Fri Jan 08, 2010 8:25 pm

Further question about the preamp layout, does V1 only produce the signal for the Normal Channel and V2 for the Top Boost Channel? I understand they both travel through the PI, but with some amps the other valves are additional gain stages.

Oddly enough, through my stock of tubes an old Chinese 12AX7A sounded the best to me in the V1 position as compared to some new production JJs, Tung Sols, balanced Gold Pin JJ, balanced Gold Pin Tung Sol ECC803, Sovtek 12AX7WA and 12AX7WC. I would have thought that the Chinese one would have sounded the lowest quality. It was just the clearest, most balanced and smoothest.
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Re: AC30CC preamp tube layout

Postby Grog on Sat Jan 09, 2010 9:19 am

Grog wrote:steve,

V1 (normal channel and first stage top boost) is towards the edge of the chassis R/Hand side looking from the front v2 (second stage top boost) in the middle and V3 (PI) is closest to the centre of the amp furthest left looking from the front.



As I said V1 is for the normal channel and first stage of the top boost
AC30 Super Twin(1963) S/N 9952N Rear Panel TB Head, Dynamic Bass (1968) #1153, AC30CCH, V212BN 1 x Alnico Blue 1 x Wharfdale, VBM1, AC4TV, Marshall JTM312, Gibson 347(1987), Les Paul Custom, US Fender Telecaster and Stratocaster, CIJ Jaguar HH.

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Re: AC30CC preamp tube layout

Postby stevewire on Tue Jan 12, 2010 1:38 pm

Grog wrote: As I said V1 is for the normal channel and first stage of the top boost


This is why I asked the question. It still is not clear what you have said. Are you stating that the second stage of the Top Boost is V2? Or the the PI(V3)? And to be clear about the normal channel, is V2 a second stage, or straight to the PI?
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Re: AC30CC preamp tube layout

Postby Grog on Tue Jan 12, 2010 1:57 pm

Sorry steve, I thought you'd missed the previous answer in amongst everything else, think of the valves as two halves ie two valves in one, and I apologise if I'm teaching granny to suck eggs here.

So,
V1 has the normal channel on one half and the top boost on the other.
V2 is just the second stage of the Top Boost, the other half does nothing as I understand it,
V3 is the PI and so takes the output for the normal channel straight from V1 and the top boost from V2.

The normal channel has only one gain stage V1 whereas the top boost has two V1 and V2, sorry if it was unclear before :thumbsup:
AC30 Super Twin(1963) S/N 9952N Rear Panel TB Head, Dynamic Bass (1968) #1153, AC30CCH, V212BN 1 x Alnico Blue 1 x Wharfdale, VBM1, AC4TV, Marshall JTM312, Gibson 347(1987), Les Paul Custom, US Fender Telecaster and Stratocaster, CIJ Jaguar HH.

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Re: AC30CC preamp tube layout

Postby stevewire on Wed Jan 13, 2010 3:17 pm

Grog wrote:Sorry steve, I thought you'd missed the previous answer in amongst everything else, think of the valves as two halves ie two valves in one, and I apologise if I'm teaching granny to suck eggs here.

So,
V1 has the normal channel on one half and the top boost on the other.
V2 is just the second stage of the Top Boost, the other half does nothing as I understand it,
V3 is the PI and so takes the output for the normal channel straight from V1 and the top boost from V2.

The normal channel has only one gain stage V1 whereas the top boost has two V1 and V2, sorry if it was unclear before :thumbsup:


Hey Grog,
Sorry if I sounded a little grouchy. I'm only using the Normal channel at this time, and I was wondering of how much beneift it would be to switch out the tube I have in the V2 spot. I guess for right now, it won't matter until I start making use of the Top Boost. You have been very helpful. Thank you.
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