AC30/6N v's AC30/6T Question

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AC30/6N v's AC30/6T Question

Postby Philthy on Thu Aug 19, 2010 4:32 am

Is the Normal channel of each amp the same, or are only the Brilliant channels different?

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Re: AC30/6N v's AC30/6T Question

Postby Grog on Thu Aug 19, 2010 6:47 am

Simple answer, yes only the brilliant channel is different
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Re: AC30/6N v's AC30/6T Question

Postby Beus on Thu Aug 19, 2010 9:45 am

no, normal and briliant channel are different. they both have a kind of treble cap circuit on the T model.

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Re: AC30/6N v's AC30/6T Question

Postby Grog on Thu Aug 19, 2010 11:28 am

Beus,


As soon as I posted that I guessed that someone would contradict it, but I didn't have time to check this morning. From looking at the schematics and component differnces listed in Stephen Grosvenor's excellent book "A Service Engineer's Guide to the Vox AC30 Valve Amplifier" I thought that differences were only on the brilliant channel, but I may be wrong, memory is not what it was. I'll have another look later, he posts on here as Stephen so maybe he'll chime in and clarify anyway

http://www.thevoxac30guide.com/
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: AC30/6N v's AC30/6T Question

Postby Masco on Thu Aug 19, 2010 12:13 pm

From what I remember, the "T" version Has the same coupling cap values as the "N", but the "T" has the added 330k /220pF RC network at all 3 channel volume controls. Someone please verify w/ schematic. For some reason the "T" schematic is omitted from most free schematic sites.
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Re: AC30/6N v's AC30/6T Question

Postby johnorth on Thu Aug 19, 2010 3:39 pm

Yes, the treble network is definitely on the volume pots of each channel. Grog, your confusion might come from the fact that Stephen Grosvenor's listing of component differences between AC30N and AC30T doesn't include the treble networks on the pots in the list, but rather mentions it in a footnote or something.
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Re: AC30/6N v's AC30/6T Question

Postby Grog on Thu Aug 19, 2010 3:48 pm

johnorth,

yes that could well be it, thanks
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: AC30/6N v's AC30/6T Question

Postby Graham on Thu Aug 19, 2010 3:59 pm

Hi! On my AC30T I,m sure it has the red caps under each volume pot, I haven,t looked for a while. These are part of why the treble model is bright on all three channels, making it very well balanced. It reminds me of an old Fender Pro Reverb I used to have, very clean on all channels! :D
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Re: AC30/6N v's AC30/6T Question

Postby Beus on Thu Aug 19, 2010 4:27 pm

you would indeed expect the treble part only on the brilliance channel. but the treble network is indeed on all channels, which makes the normal channel very useful; it has bass but also highs.

another rather big difference is that the first tube used for both brilliance and normal channel don't share the cathode resistor and cap (1500ohm + 25uF). they have separate resistors and caps which influences gain and bass response (1500 + 25uF for normal and 1500 + 0.1uF for the brilliance channel). thus both less gain. at least according the schematics. I have a T-model which has the N-model resistor and cap.

plus the last couple caps are smaller for the T model: .047uF vs 1.5uF for the N.

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Re: AC30/6N v's AC30/6T Question

Postby Masco on Thu Aug 19, 2010 5:22 pm

Beus wrote:
another rather big difference is that the first tube used for both brilliance and normal channel don't share the cathode resistor and cap (1500ohm + 25uF). they have separate resistors and caps which influences gain and bass response (1500 + 25uF for normal and 1500 + 0.1uF for the brilliance channel). thus both less gain. at least according the schematics. I have a T-model which has the N-model resistor and cap.



Aart


Ah yes, a very important part I overlooked.
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Re: AC30/6N v's AC30/6T Question

Postby Grog on Fri Aug 20, 2010 5:49 pm

Beus wrote:you would indeed expect the treble part only on the brilliance channel. but the treble network is indeed on all channels, which makes the normal channel very useful; it has bass but also highs.

another rather big difference is that the first tube used for both brilliance and normal channel don't share the cathode resistor and cap (1500ohm + 25uF). they have separate resistors and caps which influences gain and bass response (1500 + 25uF for normal and 1500 + 0.1uF for the brilliance channel). thus both less gain. at least according the schematics. I have a T-model which has the N-model resistor and cap.

plus the last couple caps are smaller for the T model: .047uF vs 1.5uF for the N.

Aart


Iwas thinking of the seperate cathode bias when I posted I didn't realise the treble on the volume pots was on both channels, you live and learn and probably forget again as well
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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