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I bought one of these amps a couple of weeks ago and noticed that the internal speaker is wired up backwards. The tip (red wire) of the internal speaker jack is connected to the ground buss of the extension speaker jacks. And the ring (black wire) of the internal speaker jack is connected to the tip of the extension jacks. I notified vht and they seem to think it is not an issue unless i was to connect an extension speaker and cause phase issue. I disagree with that statement as the speaker as it is wired from the factory will travel inwards when hit by a signal as opposed to outwards. I'd be interested to see how many amps left the factory like this. I can post some pics if anyone is interested.
Johno

it's just a phase issue.

it's not a big deal.

are you sure it moves inwards?

the phasing polarity is determined by initial phase of the output signal.

diagrammatiks wrote:are you sure it moves inwards?

Well i'm not 100% sure of it as i'm not a tech but it is my belief that that is the situation. Let's think about it for a moment, what causes phase issues in speakers? One speaker wired backwards and therefore it moves in the opposite direction to the other speaker causing cancellations. So i would say yes the speaker is moving inwards instead of outwards when hit by a signal.

diagrammatiks wrote: it's just a phase issue.

it's not a big deal.

Maybe not a big deal but certainly an issue IMO

Makes no difference for the cone, there's no "inward" nor "outward" movements issue.

kleuck wrote:Makes no difference for the cone, there's no "inward" nor "outward" movements issue.

Fair enough. I guess I don't understand the operation of a speaker. But it's still and issue if you run an extension speaker.

Yep.
But, wait, i do not own the "Ultra", but the regular SP6 doesn't have any extension output, when you connect an external speaker, the internal one is disconnected.

kleuck wrote: when you connect an external speaker, the internal one is disconnected.

This is not the case with the SP6 ultra. When and external cab is connected the internal speaker is still in circuit unless it is unplugged.

wait so are you saying the two speaker outputs are wired up differently?

if it's in parallel the 2 speakers will be the same phase.

This picture shows the connection from the extention speaker jacks. The orange and black wires on the right are from the OT. The red and black wires on the left connect to the internal speaker jack.

This pic shows the connection to the internal speaker jack. The wiring does not match the vht schematic.

Just swap them.

It also depends on the speaker. JBLs (at least the old ones) deflect backwards when a positive voltage is applied to the positive tab, whereas most American and British speakers deflect forwards. So, depending on the speaker you may need to rewire or not. The way to test is to apply a 9v (best to use a very tired one) to the wires to determine which way the speaker goes if + is applied to the tip. If it deflects backward then you'll want to rewire it. It's a concern for an external speaker cab in series, and there are those at TGP who claim to be able to hear the difference in attack from a speaker wired to deflect forwards initially vs one wired the other way???

Can they hear the color of the cables ?

kleuck wrote:Can they hear the color of the cables ?

Thought i would share here me VHT SP6 mods.
Here is the last schematic :

Lot of things here :

Tonestack modified for a more British Vibe, more boost too.

Twin bias, to be able to use also 6P3S, 6P3S-E and 6L6 (using a 8 ohms speaker in the 16 ohms output >> 4K5 on the plate)

Choke and heaters elevation (to the power tube cathode) to get rid of the hum.

Zener dropper for a more vintage/compressed sound, and too safely use EL84/6K6/6F6.

Higher screen resistor for a better sound at low volume and more compression at high volumes,to protect El84 and the like etc..

Adde a led for the Hi-Bias position (6L6 etc) and another for the "vintage" mod (-50 volts zener)

Nice, I get my Ultra combo tomorrow! Yay, my first tube amp and mod-friendly

JOHNO wrote:

IMG_1086.JPG

This picture shows the connection from the extention speaker jacks. The orange and black wires on the right are from the OT. The red and black wires on the left connect to the internal speaker jack.

IMG_1079.JPG

This pic shows the connection to the internal speaker jack. The wiring does not match the vht schematic.

There shouldn't be any problems with re-wiring the socket /s so that it/they agree with the schematic......


The manufacturer might not think it's an issue, but when it comes to live sound and recording that might cause phasing issues, so I reckon go ahead and sort it out......