Originally Posted by Magnus_CA
Are you certain these are wired correctly? Neither give any pinout information.
Sent from my Pixel 3 XL using Tapatalk
I believe they should going off what was said in the message below from page 60 of the other HTP-1 thread:
There was this quote in the Trinnov Altitude Thread which explained why you need to be very careful about Balanced Pre-amp to Unbalanced (RCA) Power Amp converters / cables. Only ever use the type of converter / cable for this that Preamp manufacturer recommends. e.g. floating (not connected) pin 3 in case of the Trinnov.
Originally Posted by ss9001 View Post
Second, I had a similar situation, one amp had unbalanced only plus I had a unique setup scenario. So I used unbalanced RCA connections to amps. I did a month of reading and talked to Trinnov's Jon Herron. You have to be careful in selecting the proper XLR adapter or balanced transformer. Most adapters are internally wired so that pin 3 (ground) is connected to pin 1 (negative) and this can work in many applications. But with an active preamp, like the Altitude, this will short the negative half of the signal to ground and the Altitude will not be happy! Noise & overheating - both not good!
If using an adapter, the Switchcraft 322X unwired adapter is the only one Jon recommended to me. I had looked at various isolation/balanced-to-unbalanced transformers like the Neutrik, Jensen, DTI Cleanboxes, and others. But I'm not experienced with pro audio applications and many of these transformers-cleanboxes have adjustments for matching signal levels & impedances.
So the safest & easiest thing for me was to use the Switchcraft adapter that he recommended:
Jon Herron posted a comment in the review section at Amazon which I'll quote here -
"Sorry, but the other review is mistaken.
There are two common ways to wire an XLR to RCA adapter: in this case, Pin 3 floats (is not connected to anything), which is better when using these adapters on the output of a high quality, low output impedance piece of pro gear. If Pin 3 is tied to ground (the other way), it is the preamp equivalent of shorting a speaker wire to ground. The output buffer will overheat and likely distort something awful, usually within 15-20 minutes.
Since the output of this thing is a single-ended signal, and the outer ring of the RCA is tied to the chassis ground, the only remaining signal that needs to be connected is Pin 2 (the red wire mentioned in the other review). Ground is handled by the body of the adapter.
These are the only such adapters I will use with our products, which are designed to pro-sound standards in terms of the balanced interface."
Mine did come unwired so I had to unscrew the barrel (easy) and solder the red wire (the only wire inside the adapter) to pin 2 (+ hot). Pin 3 (-) and Pin 1 (ground) are left unconnected.
Using the adapter instead of signal matching transformer costs 6dB signal volume. We did discuss the possibility of ground hum and if I had hum then I would have to look at Jensen RCA isolation transformers but fortunately I had no hum.
Of course Trinnov will recommend a transformer since the right one can compensate for the signal strength. Picking the right one (with no impact to noise and freq response) is the issue. For me, the Switchcraft adapter was the simplest, least expensive with no harm to the signal. They worked for me; I still have plenty of volume headroom even with my inefficient Magnepan speakers.
You might want to give Jon Herron or Chuck Best @ Trinnov a call to discuss your setup & using transformer vs adapter.
And that vdctrading XLR-RCA cable will most likely NOT be compatible with the Altitude. Every XLR-RCA cable I looked at have pin 1 & 3 wired together - a big no with the Altitude (2 preamps per channel, 1 positive & 1 negative so 2 separate signals).