output transformers>to step up or not to step up.

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JW

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Jun 8, 2005
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I attatched this question to a thread over in the Black Market, but I thought I'd ask it here, to be proper.

I'm another one of the folks wiring up output transformers to the PM1000 channels.

I've tried a couple Cinemags that someone reccomended (the CMOQ-2 series) and I've also wired up the original Tamura.

I've wired up the Cinemags @ 1:2, and when comparing a Cinemag channel to a Tamura channel, I noticed that indeed, I can get more gain out of the Cinemag, but it's at the cost of a lot worse headroom.
I get an avalanche of noise when I'm really pushing the gain when using a low output mic.

Anyway, I need to contact Cinemag again. I lost the diagram as to how to wire the Cinemags 1:1 and try that out.

But I thought I'd ask why the headroom is so bad when I wire those babies at 1:2. Compared to the Tamura, I'm really not getting that much more gain out of the Cinemag. So, I figure, 1:1 will be fine if it gives me better headroom.

Do you guys think wiring it at 1:1 will solve the problem? If that's the case, what's the theory behind why it works?
 
maybe the outputs of the PM1000 can't supply the current needed and goes into early clipping?

nothing is free with transformer ratios
 
Don't bother Cinemag for info that is already readily available on their website. They are busy guys. See here: http://cinemag.biz/output/CMOQ-2.pdf

Because it is quadfilar there are four equal windings. You can wire it for 1:1 by combining these four windings into two equal pairs, either series:series or parallel:parallel. In "test circuit 3" in that pdf they show series 1:1 wiring. My guess is that this may work the best with your PM module.

What's wrong with the Tamura output transformer that you felt the need to replace it, anyway? I am not in the know concerning Yamaha modules so please excuse my ignorance if this is a silly question.
 
[quote author="Family Hoof"]
What's wrong with the Tamura output transformer that you felt the need to replace it, anyway? I am not in the know concerning Yamaha modules so please excuse my ignorance if this is a silly question.[/quote]

There's probably nothing wrong with the output transformers. But there's a small problem with the pm1000. It's got 16 channels and 15 output transformers :grin:

Where do you connect the outputs? If i remember correctly the 2 echo sends don't really have enough juice to drive an output transformer. Especially not if it steps up the levels. So that might be your problem

Another problem might be in what you connect the output to. If you're trying to drive 600 ohm with a 1:2 output transformer the pm1000 will see 150 ohm. I'm not sure this will work.
 
Thanks guys.

I'll try wiring the Cinemag at 1:1.

The diagram in this thread (couldn't be much simpler) in the tubejay post is how I'm wiring the direct outs: http://www.groupdiy.com/index.php?topic=5643&highlight=pm1000+transformer

For those of you who have done this (w/ the Tamuras), do you ever ground the little black wire that's hanging off? Or just leave it hanging, like it always is in the rest of the board?

One more question: When I rig up the XLR output jack, I'm grounding pin 1 on the XLR to a spot on the PCB where a million things are grounded (I think this is the star ground, right? Mostly around the edges of the PCB?) Does that sound like the right thing to do?

To explain why I'm trying to hook up the Cinemag, I'm adding direct outs to at least 8 of the PM1000 channels, which it doesn't originally have.
I like the Cinemag so far (even at 1:2) for louder sources like drums.
I'm toying with the idea though, now, of borrowing the Tamuras from the monitor and redundand buss sections, maybe even the talkbalk channel instead of ordering a bunch of Cinemags.
 
Thanks Hoof for that link,

If anybody takes a look at that Cinemag PDF, and the link I provided in the last post as to how to wire up a direct out from C37 on the PM1000,
could you tell me if this sounds right?:

C37 >brown wire(transformer in) >green wire(transfomer out) > pin2 XLR

Red and Orange connected together/ Blue and Violet connected on other side

star ground>yellow wire (Xformer in)> Grey wire(Xformer out) > pin 3 XLR
___________________________________________________________

star ground > pin 3 XLR out
 
JW, I just started playing around with my PM1000 tonight. Did you catch that there is a pad used right before the output transformers on the 4 bus section? 12K series, 6.8K shunt. If you forgot the pad, that might explain why your xformer is overloading.

-Chris
 
Hmmm.

No, I havn't put a pad in at all. You mean, as the the transformers are originally wired up in the buss sections, there is a pad right before them?

There's also an extra input transformer on the buss channels, so maybe the level has to be knocked down again before it hits the output transformer?
(I don't know. I really hardly know anything about this stuff)

As for distortion, I actually havn't experienced any distorting (except for when I was accidentally grounding C-37 to the chassis, which was in a post a long time ago)

I actually kind of wish there was another optional gain stage before the output transformer (within the input strips and before the direct out mod) that you could switch off when you're mixing with the PM1000 and using the inputs as line amps.
 

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