Atma-Sphere MP1 with single-ended inputs and outputs? Adapters OK?

@parsons 

I'm sure you are thrilled with your Thoress 845 SET,  an excellent sounding amplifier by all accounts.

Charles

I appreciate all the feedback.

I tried it with 3-4 SET amps actually with unfortunately the same results in each...never had the impact that the all Atma- in balanced provided when being driven single-ended from the MP-1.  Perhaps it was just something with mine if others are having better luck.

I sold my Atma gear last year as the amps were more power than I needed and I found a really strong preamp that complimented the SET amps straight away.

@parsons 

I'm also a happy SET amplifier owner. I wonder if your issue is specific to your particular SET. I heard my Coincident Frankenstein 300b SET paired with the Atma-sphere MP-1 and it was splendid! This MP-1 had RCA outputs.  No noise, just very open, transparent, full bodied beautiful sound filling the room.

If I did not already own the superb sounding Coincident Statement Line Stage I could very happily live with the MP-1.

Charles 

I got return and refund of the ISO MAX transformer finally.

It has strong noise for my system, I do not know how other's situation.

@parsons Just a FWIW, any SET can be set up (if you see what I did there 😁) to use both phases of a balanced signal. Its easy to do, inexpensive and does not change the character of the amp. By doing it this way there is no buzz or the like. That is how I have used the MP-1 (or MP-3) with SETs in the past and it works a treat.

The hardest part of this mod is finding a spot on the amplifier chassis to install the XLR connector. The rest of it does not require any component changes in the amp. Normally the SET accepts a signal on the grid of its input tube; but it can accept a signal on the cathode of that tube as well. So we just make that input available on the XLR connector.

i had forgotten about this thread.  Sorry I never responded back to my own original post once I got further in my own search.

In the end I tried a number of different solutions.  Adapters seemed to be less than ideal for me on a number of different single-ended amps, including the Atma amps I had that also had single ended inputs.  I tried a few different pairs from some decent brands.  Balanced out and in from the Atma gear were great.  All the adapters, if I recall, seemed to collapse the sound stage and ultimately seemed to be a poor solution for the quality of the rest of the gear, including the MP-1.  There was also a bit of noise that was inconsistent with the amps fed from other (unbalanced) pre-amps I owned.

I sent the MP-1 in for service (for a different reason) and while there I had Ralph install some single-ended outputs which included a switch.  I will admit when I got it back I didn't totally understand what the switch did because in either position there was the same level single-ended output (it also didn't appear to cut off the balanced output).  I didn't have the greatest luck with single-ended connections out of these outputs either, again with a pretty large number of amps I tried, and with the switch in either position.  Similar issues, but maybe even more noise than with the adapters, or at least as much.  I remember being pretty dissatisfied overall.  Impedance issues between the pre and the amps?  I don't know, but that's what my un-educated brain concluded.

Later settling on some fairly high-end SET amps, I got a bit desperate and through research took a long-stretch last chance on an Art Accessories Clean Box Pro.  This was WAY outside of what I was going for but somewhere I had read that they were very effective even in some pretty serious systems, wall wart powered and all.  In an ultimate irony I had $1K balanced cables going to $1K RCA cables with a $79 converter box sandwiched in the middle.  Ironically enough, the whole setup sounded pretty amazing, low noise and much better sounding than I had reached with the MP-1 and these unbalanced amps, and I ran with that configuration for probably 18 months.

In the end I bailed on the Atma- pre-amp once I had found another that worked better for me, knowing I wasn't going back to balanced amps again.

Worth a $79 try if you're in the boat I was in...just return it if it doesn't work.

I wrote email 3 days ago and they do not reply me yet.

I have to say that when I dealt with Jensen, they were very easy to work with.

I am sure if you explain the situation, they would be able to find a suitable product.

B

The one I got is defective one, when I connect it ,just less than 5 minutes later, strong noise coming from the speakers even I shut down the volume.

I am discussing with Jensen for return.

I think the isolation transformer should have gain volume control and let you get the right gain after the transformer, as the signal will become weak  if no gain increase and that's the reason I give up the way to use Jensen isolation.

There are a variety of different Jensen transformers. Some have step-up, others step down and still others are 1:1, doing only isolation or conversion from balanced to single-ended (or vice-versa).

So what is final solution for RCA pre to go xlr  only  power amplifier? The answer is passive preamplifier with XLR output.

You put that passive preamplifier in between your  RCA pre and. The power amplifier, that's it.

Get high quality one to match your RCA pre.

I use the Jensen isolation transformer, and the sound lose a lot of detail.  I think the isolation transformer should have gain volume control and let you get the right gain after the transformer, as the signal will become weak  if no gain increase and that's the reason I give up the way to use Jensen isolation.

I think RCA output to XLR input cable will be safe, but XLR output and RCA input will be careful.

The Jensen Isomax transformer works very well converting balanced to SE. But, correct me if I’m wrong @atmasphere , doesn’t connecting a stand alone transformer inline w/ an OTL affect the sonics?