Problem with Cinemag and AA 2006 phono.

[pengboon]

I have been using the Denon DL-103R with the Denon AU-300LC and the AA 2006 Phono

Recently I decided to try the Cinemag CMQEE-3440A as step up based on good feedback on audioasylum. However, after wiring it up as per cinemag's documentation, all I get is very distorted and scratchy sound, and I still can't figure out why.

Appreciate any suggestions from anyone to help me troubleshoot. I already checked the wiring many times, I also tried using only one primary, without success.

thanks!

 

[phn]

It's hard to say. But have you made sure it's properly grounded?

 

[pengboon]

I tried grounding both primary and secondary, only the primary. I tried revering one primary, I get very low sound level but the sound seems un-distorted. With both primaries in the same direction (as per the instructions), sound level is OK but distorted.

The instructions are here

I'm really scratching my head on this one, I thought this should be relatively simple to do...

 

[SY]

If you haven't already, use an ohmmeter and get a sanity check on the windings. Mistakes on the manufacturer end have been known to happen...

 

[SY]

BTW, maybe some of the analog and transformer experts can weigh in here, but that connection scheme shown at the Cinemag page linked to by pengboon seems very suboptimal, wasting wire and throwing away potential common-mode rejection advantages. Or am I missing something? How well balanced are those primaries?

 

[pengboon]

I have, the primaries are about 26 ohms, with the centre tap somewhere in between the 2 ends. The secondaries are 3.9k. Anything else I should check?

 

[SY]

OK, for fun, ignore one primary completely. Connect your cartridge across the other, ignoring the CT for the moment. What happens?

 

[pengboon]

Hi SY, same result, scratchy, distorted sound.

 

[SY]

OK, now do this same thing with the other primary.

When you were measuring resistances, did you check that all coils were isolated from one another and all isolated from shield and core?

edit: How do you have the secondary hooked up to the phono stage? Which input, what loading, yadda, yadda?

 

[pengboon]

Same result with the other primary.

I chekced between coils, the resistance were in terms of Mohms, then slowly decreasing to kohms... is this normal?

I have the secondary (VIO) into the phono's input and white/grey/black into the phono's input ground. I tried connecting phono ground with primary ground and not, both yielded the same negative result.

The loading of the input should be 50kohms, I tried a 30k in // to make the reflected loading 14R to match the cart, but same result still.

The thing is, my Denon SUT (AU-300LC) works fine, so I think my TT/cart is fine, and the phono is fine. Something is wrong with the way I am hooking up or with the SUTs themselves...

 

[SY]

I chekced between coils, the resistance were in terms of Mohms, then slowly decreasing to kohms... is this normal?

If the transformer is isolated from the circuit, then no, that's not normal.

I don't remember, do you have a scope? It might be interesting to see if the transformer could be causing an oscillation. You are using the MM input?

 

[pengboon]

Hi SY,

Let me check again, which wires should I measure across?

I don't have a scope, using MM input. Is it possible the transformers are interacting with the input capacitances? This phono has absolutely no problems with my denon 1:10.

 

[SY]

Disconnect the transformer and measure between any primary and any secondary lead. Should be open circuit, as should any of those wires to case or shield.

Looking more and more like you've got some defective transformers.

 

[pengboon]

I measured, they are in the Mohm range, at least 1Mohm, then slowly the DMM reading goes up (my mistake previously in saying it goes down)...

 

[SY]

A scope would confirm it, but I think the transformers were wired wrong internally; they came out of the same batch, presumably? I've seen this happen when multiple sections are connected internally out of proper phase. This would be a good time to contact Cinemag.

 

[pengboon]

I have, thanks SY! they were bought as a pair, so I would think they would be from the same batch.

 

[kevinkr]

Is there any possibility that the input of the phono stage is being overloaded by the voltage gain provided by this transformer which for the 37 ohm input would be about 37:1 and for the 150 ohm input about 18:1? This is substantially more gain than the 10:1 transformer it is being compared against.. Just a thought..

Cinemag makes very good stuff and has excellent QC on their products, while it isn't impossible I would be very surprised if something was wrong with those transformers.

 

[SY]

You'd think so, wouldn't you? But I have some input trannies from a first-line manufacturer (much more expensive than Cinemag) which had exactly that problem- the secondary coils were connected out of phase internally. The manufacturer acknowledged the issue somewhat sheepishly and would have replaced them without hesitation.

 

[pengboon]

Is there any possibility that the input of the phono stage is being overloaded by the voltage gain provided by this transformer which for the 37 ohm input would be about 37:1 and for the 150 ohm input about 18:1? This is substantially more gain than the 10:1 transformer it is being compared against.. Just a thought..

Cinemag makes very good stuff and has excellent QC on their products, while it isn't impossible I would be very surprised if something was wrong with those transformers.

My cart is spec-ed at 0.3mV, and I load it with 18.75k on the secondary, so on the primary it will be about 14R, same as the cart. This should result in about 5+mV into the phono. Will this overload the phono?

 

[SY]

If 5mV overloads the phono stage, that's a pretty weak phono stage.