I've got 2 extra outputs on my '74 DR 103.Any ideas??

[andynervous]

Hi,

Since joining your excellent forum about a month ago I've noticed,(I couldn't really miss them!),2 extra jack-plug sockets

on the back of my amp. I have owned,and used this amp several times a week,since '93 and it's wonderful,. It's a real

workhorse and maintains great quality of tone,perfect for my style of double bass playing,Rockabilly/Psychobilly slap,and

in all that time it's cost me just one set of cheap tubes,(how times have changed,I can afford better now,thank god!).

I must admit,before joining on here I've never met another bassist or double bassist using a 103 and so I assumed these

were standard and were line out sockets. Recently I've been playing bigger venues and have been using one of these as a

line out to the desk,but a few of the engineers have complained of hearing a hum. They were blaming my amp,which I

absolutely know does not hum,(how dare they!?!?),and,likewise,I'd blame their old mixing desk.

I've taken photo's of my amp and have tried to include this mod and I'd be very grateful if anyone can help/advise me

about,not only what it is,but also whether or not I should use them or remove them. I realise it's better to have

everything original,which as far as I know,mine is and I'd like to maintain it so. The other thing I wanted to ask is,I've

noticed my tranny's have non-corresponding no's on them,one's H2 and one's H3 I think,was this 'normal' practice or does

it mean one was replaced?

Thanks and best wishes,

Andy.

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[mhuss]

It's hard to tell from the picture you posted. It looks like one gray coax is going to the master volume (which would make me think line out/passive effects loop) but the other gray coax seems to be going to the speaker jacks.

A close up of where each coax connects would help.

If those extra jacks in the middle are grounded to the chassis, it could be causing to a ground loop with the mixing desk.

If you post the full numbers from both trannies, someone here can likely answer your question on that topic.

--mark

[Dr.HI-TONE]

If you can post more straight on, close up pics, we can tell you more.
Thanks!

[andynervous]

Hi guys,

Thanks for checking it out. I have taken some better pics,(I hope!). My canera isn't the best quality I'm afraid .

Mark,I tried to get the numbers off the trannies but they are a bit difficult for me to read. I've added a pic of each as I

thought that having seen others for comparison,your trained eye would be more accurate than my complete novice

view,(and failing vintage eyesight). I hope they are ok,if not,please let me know and I'll have another go when I'm sober!



Thanks and best wishes,

Andy

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[mhuss]

Sigh, those pictures are still not shedding a lot of light on things. Do you have a child or friend you could borrow a better camera from?

On closer inspection, it looks like the extra jacks have plastic sleeves, so that should not be be causing a ground loop just be being there. However, it appears the line outs are referenced to chassis ground, so an overall ground loop is still likely. You might want to try an isolation box (basically a 1:1 audio transformer) between the amp and the desk.

--mark

[OldSchoolDave]

Andy,

If your camera has a MACRO mode, use that for the close-up pics.

Dave