Marshall power amp link out jack

[arkieboy]

Hi all

Can you use the 'link out jack' on the Marshall rack power amps (mines a 9100) as an alternative input for a second preamp? I wouldn't be sending signal to both at the same time...

Thanks

Steve

[zenguitar]

Hmm, interesting question Steve,

I'm really not sure, and (as always) the Marshall manual doesn't tell you enough to work it out.

However, I've found the schematics on this site which might help Dave or Folderol work it out whether it's possible/sensible.

And you never know, it might be OK to have both pre-amps working at the same time. So perhaps I should add my 9005 power amp to the question too (there are schematics for that there too )

Andy

[Folderol]

Looking at the schematics (the 9005 is MUCH clearer) I'd say the answer is no. You would be feeding the output of one pre-amp directly into the output of the other. You could add series resistors in the leads turning them into a passive mixer but then it starts to get a bit silly. You would have to make sure you used the right leads all the time!

[zenguitar]

Cheers Will,

I had a feeling you were going to say something like that. When it looks too good to be true, it probably is

Making custom leads is probably as much work as making an A/B/Y box between the pre amps and power amp or using a line mixer I guess.

Andy

[arkieboy]

Thanks Will

I'll get one of these then!

Steve

[arkieboy]

Will, Andy

While I have your collective attention

Although I've owned the gear for quite some time, I'm embarrassed a little to confess that I'm struggling a bit lately to get to on top of the relative volume levels between patches. Especially lead and rhythm. This is because I've finally met a drummer who can drum at many volume levels rather than just 'as hard as I can hit them'

My suspicion is that the power amplifier is compressing the output of the pre amplifier (which is good - I like power amp squash). At some settings I'm getting less compression and thus a bigger difference between lead and rhythm patches. I think I get the best results when I adjust the master volume on the power amp rather than twiddling the seductively labelled knob that says 'volume' on my JMP1. This is of course best as far as S/N is concerned...

However I get precious little time alone with the kit to be able to do any vaguely scientific test

Andy, Is that your experience? Will, What does the circuit diagram say?

Thanks

Steve

[zenguitar]

It's been a long while since I fired up the rack in anger Steve, but I do recall something similar to what you describe. It's predictable with the power amp flat out, and with it ticking over gently with the Masters turned down low. But in between it can be quite sensitive when juggling channels.

I've since put together a pair of SE100's, one for each channel, to give me the option of driving hard and attenuating the speaker outputs. But I haven't had a chance to give it a good workout. The whole rack really ought to go off to Marshall for a full service

Andy

[zenguitar]

WEIRD!!!

I've just returned from New Year's Eve in the pub to discover that this post has been bumped.

And despite what it says, it wasn't by me. When Eddy's posts had the same problem we established that the bump feature hasn't been activated.

And the rack still hasn't been fired up and still needs a visit to Marshall for some TLC.

Andy

[Wonks]

Maybe all the old posts are being resurrected by the ghost of forum past?

Both of Arkieboy’s 1U Marshall rack units are sitting in my hall waiting to be looked at by my amp repair man. Both the JMP and his (fairly new to him) 20/20 power amp are very dead. One of them went very wrong and killed the other, along with the RCD that fed them.

If the power transformers are fried, then it’s game over for both of them as the transformers are no longer available/obtainable.

He’s still got the 9100, but it’s too big and heavy and powerful for his current needs.

[zenguitar]

Maybe all the old posts are being resurrected by the ghost of forum past?

When you consider the number of revisions the forum has experienced, there's a lot to be said for the Ghost of Forums Past.

That 20/20 power amp has been high on my wish list for over a decade, it really is a very good stereo power amp... So best wishes in getting it sorted. It really was a sweet spot and remains such.

Finger crossed.

Andy

[Folderol]

Maybe all the old posts are being resurrected by the ghost of forum past?

Both of Arkieboy’s 1U Marshall rack units are sitting in my hall waiting to be looked at by my amp repair man. Both the JMP and his (fairly new to him) 20/20 power amp are very dead. One of them went very wrong and killed the other, along with the RCD that fed them.

If the power transformers are fried, then it’s game over for both of them as the transformers are no longer available/obtainable.

He’s still got the 9100, but it’s too big and heavy and powerful for his current needs.

If kit is wanted badly enough, it is possible to get transformers rewound. A (very) long time ago I did that myself. Mains ones are a doddle, Output ones need more care, however even if the primaries are fused to a solid lump it's still possible to work out the turns ratio from the secondary and the rest of the circuit.

[arkieboy]

(I was even more surprised to see this pop up - for a moment I wondered if there had been some username snafu and it was someone else’s question)

I do hope the JMP1 can be fixed at least - I have both the valvestate (8080) power amp and the 9100 I can pair with it.

It might anyway be time to move on anyway - the JMP1 was an excellent solution for me up until about a decade ago, but these days it’s hard to beat the simplicity of a digital rig when you need to be on-and-off stage in a handful of minutes at a festival or support slot. I do want a valve amplifier, but I really want something studio oriented, and if it can do the live thing then that’s a plus. Currently thinking something Cornford - either a Harlequin or possibly a MkII for additional live options.

[Gadget13769]

...Currently thinking something Cornford - either a Harlequin or possibly a MkII for additional live options.

Remember that the Harlequin is only 6 Watts.

[Wonks]

I think he meant the 20W Hurricane, not the 6W Harlequin.

[arkieboy]

Could have phrased it better. Definitely considering an amp purely for the studio, Wonks, although a Hurricane would be far more useful.

The problem with the MkII is there’s a disparity between what owners think they’re worth and what buyers want to pay for them. So I’m not holding out much hope of one wandering along at the right price when I’m ready to pay for it!