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High pinched whistling


VDS

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21 minutes ago, VDS said:

 

@Edgar, lots of controversy about ferrites.  Some say they work best on power cables bringing interference  into the amp, or other device.  

 

"Some say"? They're cheap enough that you can try them for yourself; on the power cable, the interconnects, the speaker cables, or any combination thereof. If they work, great. If they don't, then you're only out a few dollars. If they work but have a slight detrimental effect on sound quality, then you'll have to decide for yourself whether it's still better than the whistle that they eliminate.

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VDS: Please clarify a couple of things. Is the Pass amp a DIY or a factory version (what I am getting at is whether the input grounds are directly or indirectly electrically connected to the amplifier chassis). The shield on the RCA side of the cable is electrically connected to Pin 1 on the XLR. However is the mechanical connection at the RCA side or the XLR side (or both). The reason I ask (and this is a remote possibility) is whether the the "third wire" is not connected on one end then it could be acting like an antenna and picking up junk (not a technical term). In either case "fixing" the cable can help things (whether it is ferrite acting as a filter, or a transformer isolating any small potential difference (voltage)). This is why I say this is ultimately a cable issue and not an amplifier issue. 

 

The reason some of us are having difficulties is that bad cabling usually results in low frequency junk (hum etc). Your problem is a bit different. 

 

As an anecdote, I used to work in auditory labs (science kind and not the recording kind ...). Mixing balanced and unbalanced equipment was always a nagging problem (not every time, but occasionally). We would all come through the set up when there was a problem and frantically swap cables, power cords, toggle "ground float switches" etc, etc. Eventually, the circuit would quiet down (after going through an endless combination of wire / equipment swapping) and someone would proclaim: "see I told you so .... it was a ground loop" (although they never actually pin-pointed the culprit). 

 

BTW, if you look at the schematic of what the Jensen ISO unit is, you can mimic it for less money although it won't be packaged in a nice box (Cinemag will have the appropriate transformers for about half the price). These boxes are frequently used and have been even in the old days. 

 

Good luck, 

-Tom

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23 minutes ago, PrestonTom said:

 

BTW, if you look at the schematic of what the Jensen ISO unit is, you can mimic it for less money although it won't be packaged in a nice box (Cinemag will have the appropriate transformers for about half the price). These boxes are frequently used and have been even in the old days. 

 

 

I have a few WSM15K/15K https://www.edcorusa.com/wsm15k15k, though I haven't tried them yet.

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@PrestonTom, xa25 is official Pass Labs, First Watt F3 is clone.

Funny you mentioned grounding to the he chassis, I am just about to send the F3 to someone to fix some decisions made by a he original builder, one of them being the AC mains not grounded to the chassis. I don’t know enough about electronics to fully grasp this, but I’m told it’s a problem and a safety concern. 
 

 

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@VDS  Well the way I look at it you have invested $$$$ in your Loudspeakers and Amplifiers and IMHO based on personal experience the Jensen transformers and ISO-MAXX products are very well engineered high quality products with well published testing and technical specifications available and most important of all based on my listening experience they are neutral with no audible coloration or loss of detail/clarity and this is why I prefer them and believe they are well worth there cost. I have chosen to implement them in my system not because I was having any obvious Hum/Noise Issues but because I’m confident they offer me the highest signal preservation quality possible in the real world situation our systems have to operate in.

 

If you are the DIY type the Jensen Transformers are available themselves but I would caution for optimum performance how they are installed is very important.

 

Based on the information you have given us my thoughts are the Xilica and Pass xa25 are fine and you are just experiencing complications that periodically happen from mixing balanced with unbalanced equipment. IMHO the best solution now and for any future amplifier options you might like to try would be one of the ISO-MAXX products. 

 

I personally use the PI-XX, PI-2XX and PC-2XR (Uses a 4:1 transformer to match Pro Reference Level to Consumer Reference Level which is about a -12db gain reduction).

I use the PI-XX (single channel unit) and PI-2XX (dual channel unit) with my McIntosh amplifiers and my First Watt F3 amplifiers (F3 benefits from the higher drive level) and the Schiit Vidar sub amplifier.

The PC-2XR has advantages in systems where the gain structure is such that the Pre-Amplifier Volume Control can’t be adjusted beyond about 10:00 o’clock or 11:00 o’clock without it becoming to loud and often you will have audible noise/hiss at the listening position from the HF Compression Driver/HORN even at idle with no music playing. In these situations the Isolation plus (-12db gain reduction) gives the best performance.

 

miketn

 

 

 

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When the ground is added to the F3 clone maybe it will have the problem too:)

Sorry I am just alluding to the fact that adding grounds almost NEVER fixes any of these types of problems.

Think about it, adding a ground gives ground current another possible path to form a loop.

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1 hour ago, Edgar said:

 

JT-123-FLPCA

 

Did you mean JT-123-FLPCH…?

If so it is a Line Output Transformer and anytime a Line Input Transformer is an option it is the better choice to use.

 

 

Jensen about Line Input Transformer versus Line Output Transformer:

 

8EF458B5-2744-4FEE-823F-44C2E4FDA6DD.thumb.jpeg.8a4dde98769b7ca65c43a974757bfe1d.jpeg

 

 

More Information for those interested: See page 26 and 27 for advantages of Input Transformer versus Output Transformer as it relates to CMRR and RF noise.

 

generic-seminar 2.pdf

 

 

miketn 

 

 

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2 minutes ago, mikebse2a3 said:

 

Did you mean JT-123-FLPCH…?

 

 

No. FLPCA. Says so right on the label. But you're right, it is a line output transformer. I just used it for size and configuration comparison because that's what I had on hand.

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I have ordered the Jensen PI-2xx. Arrives tomorrow.  

@mikebse2a3, I was a little concerned about the 12db loss with the PC-2xr.  
I don’t know anything about these isolators, but I did wonder if using the Jensen pc-2xr to do the xlr to rca conversion would be better than the xlr to rca cable. @Chris A said he uses the PI-2xx, so I went with that.  We’ll see tomorrow.

As for the F3, it’s a Tim Rawson build, I don’t want to bad mouth him at all, but I’ve read many posts on DIY Audio pointing out some questionable build decisions, a safety concern over some lack of grounding being one concern.  
Thanks, Ted

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1 hour ago, VDS said:

I have ordered the Jensen PI-2xx. Arrives tomorrow.  

@mikebse2a3, I was a little concerned about the 12db loss with the PC-2xr.  
I don’t know anything about these isolators, but I did wonder if using the Jensen pc-2xr to do the xlr to rca conversion would be better than the xlr to rca cable. @Chris A said he uses the PI-2xx, so I went with that.  We’ll see tomorrow.

As for the F3, it’s a Tim Rawson build, I don’t want to bad mouth him at all, but I’ve read many posts on DIY Audio pointing out some questionable build decisions, a safety concern over some lack of grounding being one concern.  
Thanks, Ted

 

I generally use and recommend the PI-xx and PI-2xx over the PC-2xr (unless as I indicated in an earlier post that there is a clear gain issue in a system) because they are optimum with Balanced Equipment and have worked really well with Unbalanced Equipment in my experience..

 

miketn 

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1 hour ago, babadono said:

Ah guar- an -tee IF the problem is a ground loop it(the IsoMax) will eliminate. Or even if it is common impedance coupling it will eliminate that also.

A wondrous fix indeed... watching.

Cool...

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