XLR to RCA Adapters

There are so many considerations relative to the specific gear being used that IMO "one size fits all" answers do not apply. My single-ended Tom Evans Vibe/Pulse II is far and away the quietest preamp I have owned (out of many) and running it through 2.5M rca cables into Jensen PI-2RX (rca to XLR) transformers then through very short XLR cables into balanced amps results in the best sound I have achieved in many years of doing this.

I will answer this by saying the folks at Jensen are available and IME very helpful in answering questions about the use of their transformers. They are very good at determining which of their products best suits your goals and then explaining the anticipated result of using the product. I would call them if you are serious.

Regarding channel balance tracking and sound quality improving as you advance a volume control, these may be two different things. The channel balance improvement should only be relative for volume pots (e.g., potentiometers) and should not be affected if the volume control is resistor based or a chip control. However, I suspect there could be instances where sound quality improves as the preamp is operated at higher gain (or less attenuation) because the associated componentry is operating in a more linear range resulting in a lowered noise floor and improved signal to noise ratio. This is one benefit the Rothwell people speak to when promoting their 10dB attenuators. I suggest the EE's or designers chime in on this issue since I am in the deep end now.

As Al discusses, perhaps the cables also make a difference. My rca IC's are a balanced (they call them that when both legs are the same) twisted pair type shielded cable from Furutech made from PCOCC copper. There is literally no noticable noise from the speakers at virtually any typical volume level, unless music is playing.

Hi guys, I just had a chance to check in and see Bob's question about the input transformers. I believe these minimized any impedance differences, as long as you keep the balanced IC's from the transformers to the amps very short. Jensen says 1M or less, but shorter is better. Of course the ideal approach would be to mount the transformers internally with RCA inputs to the amps.

Between talking with Jensen and going over their literature, I remember that the input transformers were clearly the better approach for the rca/XLR interface. Virtually no sonic penalty with regards to measurements (I believe some very small input loss - like 1.5 dB) which I cannot detect even when comparing to balanced preamps. They work with loads as low as 10K ohm and I believe the impedence issues are somewhat related to the load, and to the transformer to amp cable length. My highish 100K ohm input amps result in an optimal impedance situation. The transformers also provide noise rejection benefits. Here is a link to read,[url]http://www.jensen-transformers.com/datashts/pi2xx.pdf[/url]

The guys at Jensen and the associated documentation do a better job of explaining than I can. Compared to giving up equipment you like the price of trying the transformers make them a stupid easy decision. I remember initially trying the output transformers based on someone's suggestion but they were noisy and didn't sound good, I called Jensen and they told me "you want the input transformers." They swapped me for the input transformers and I later purchased their mono version to keep cables very short - mine are like 2 feet long from the transformers to the amps. Call Jensen, they are very friendly and knowledgeable.

Now if you are using a single-ended source with a balanced amplifier, you will not be able to realize this advantage. Thus comes the idea of a transformer. You would use the transformer directly at the output of the source, keeping the cables between the source and the transformer as short as possible.

Ralph, with all due respect, this solution did not work for me using the Tom Evans Vibe/Pulse 2 single-ended preamp into Clayton M300 (balanced input only) monoblocks. It is also contrary to what I was told by Jensen, who recommended using the input transformers next to the amps with very short balanced cables to the amps, which is the solution that has worked very well.

However the transformer (including the Jensens, which are excellent) will have a sonic artifact which is easily heard, even if properly loaded.

In my case, where my preamp output impedance is very low (12 ohms) and my amp input impedance is 100K ohms, "easily heard" would be an overstatement, better replaced with "barely heard" or perhaps "negligible." Also, the acceptance of this solution can be dependent on the gear. In my case, based on my desire to stay with SS devices, the TEAD preamp with transformers beat every balanced (SS) preamp (without transformers) alternative I have tried to-date.