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


I had the opportunity to hear an end-game system (for me) that was fronted by an Atma-Sphere MP1 preamp and their Novacrons.  I was blown away by the overall sound, and am highly considering starting purchases toward that system for myself, but had the following questions I'm hoping someone could answer.

In short, the purchase path for me is likely going to last 18-36 months, given the costs of the various components and speakers, so I'm going to have to be living with "hybrid" systems for that time period while I spread the purchases out.

My current weakest link is my pre-amp (although it's not weak, but...).  If I start with the MP1, both my source material (VPI Classic turntable) and amps (Thoress 845 SET monos) are single-ended.  I'm sure I could get an appropriate balanced output for the VPI (I think?) and my DAC already has balanced out (which is my only other source), but what loss in sound quality will I experience adapting for singled ended RCA connections out from the MP-1 to my SET monos?  My current set-up has short (1.5M) runs, so the length of cable won't be an issue for me in single-ended.  But will using something like adapters or the tape outs on the MP1 negate any sonic benefits of the MP1 I might otherwise be getting for the time period I'll be using single-ended amps?  BTW, I LOVE the Thoress 845 amps, so they will likely be the last part of the chain I will consider replacing, and I may choose to keep them in the end-game system depending on the synergy.

Thoughts or experience with the MP1 and single-ended output?
parsons
It's easy to turn the VPI Classic into a balanced output, just change out the junction box to XLR's.

http://www.elusivedisc.com/VPI-JMW-XLR-Junction-Box-With-Standard-VPI-Wire/productinfo/VPI-D1027/

The Atma-Sphere MP1 preamp will work well with adapters, but it will sound better without them. IMHO.


Parsons, 
A friend of mine has the Atma-Sphere MP-1 preamplifier and the MA-1 amplifiers with balanced cables.  When we placed my 300b SET amplifier into his system we used a  rca cable.  The sound was room filling gorgeous with both amplifier and cable configurations.  You'll be very fine with the MP-1 with either cable type based on what I heard. 
Charles 
I don't think you won't need to use adapters on the amp end, at least.  The Atma amps that I have owned (S-30 and M-60 ) all had RCA/SE inputs.
I'm specifically asking about using them with SET amps that only have RCA/SE connections.
Charles, do you remember how you connected it?  Did he have adapters or did his have SE outs?
You can use the adapters or have an XLR > RCA cable made. Another option are these which I use:

 http://http//www.jensen-transformers.com/product/pi-2xx/
First, I would contact Ralph at Atma-Sphere directly. He sometimes has demos/trades available. He sold me my equipment for a reasonable price. I always wanted to try tubes, but thanks to Ralph, I now have a killer system.
Second, I would consider an MP-3, if cost is concern.
I run my Vandy Treo's with the MA-1's and MP-3. I could not be happier.
Bob
Be careful before using XLR to RCA adapters on outputs!  Most of them short the signal on XLR pin 3 to ground (XLR pin 1).  Some equipment can tolerate that, but some cannot.  See this thread for an example of a situation in which it could not be tolerated. 

Also, note that RCA outputs on the MP1 are described as "optional."

Also, I would assume that the tape outputs you referred to are "ahead" of the volume control in the signal path, and therefore would not be suitable for connection to a power amplifier.

The suggestions of contacting Ralph and considering the use of a Jensen transformer are good ones.  And perhaps Ralph will respond in this thread when he returns to work tomorrow.

Regards,
-- Al
 
Agreed..."tape output" is full signal (no attenuation)...I misspoke there.  Also good advice to contact Ralph...I know he's quite active here as well.
Parsons there's a used, current Novacron on Audioasylum.  Looks like a good deal.
Hi Parsons,  
It was my friend's system so he did the cable connections himself behind his rack.I just assumed that his MP-1 had rca inputs.  As I wrote above the sound quality was excellent with either type of cable. 

The MP-1 mated flawlessly with my SET amplifier. It was a very memorable listening session for all involved. 
Charles 
Parsons, 
The more I think about it I believe that he didn't use a cable adapter,  so his unit probably has SE outputs. 
Charles 
The Atma-Sphere MP-1 and MP-3 are both available with optional RCA outputs (in addition to the dual balanced outputs). When this option is added there is also a switch installed to switch between single-ended and balanced operation. This is needed as otherwise you can encounter a buzz. When the switch is in the single-ended position the output of the preamp is then single-ended regardless of the connector used.

You can also use and adapter or cable that does the conversion. If so, it is important that pin 1 and pin 3 of the XLR be somehow connected together. This will not harm the preamp in any way and is needed to prevent buzz.

The reason the buzz can occur is that the output of the preamp (pins 2 and 3 of the XLR) is a true balanced circuit, and therefore is 'floating' with respect to ground. If only one side of the output (for example pin 2 of the XLR connection) is used, it will behave like an open input, because that is exactly what it is. To solve this, one side (usually pin 3) is tied to ground (pin 1). 
Do the adapters you talk about on the site help alleviate that?
The problem with XLR-to-RCA adaptors is that they’re made of brass, including the Cardas. But then so are most RCA jacks. Apparently copper is too soft.
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?
clio, almarg, et al.

I'm using Parasound JC 2 BP and JC 1 monoblocks to drive KEF Reference 107/2s.  The amps sit next to the speakers, about 15' from the preamp.  The RCA connections of a KEF KUBE prevent me from using balanced lines between the preamp and amps, but I have Jenson Isomax transformers and wonder if using them on either side of the KUBE would be a good idea.  The Isomax units would be close to the preamp with a long run to the amps.

db
@dbphd  that sounds like that should work.

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?
Of course, and OTL has nothing to do with it. I prefer to use adapters myself (the ones we make have the correct connections).

Now another way of dealing with this when using an amplifier which has a single-ended input (in particular tube amps) is to modify the amp so that it can process the inverting signal from the preamp (in addition to the non-inverting signal). This is a lot easier than it sounds and the character of the amp is not changed at all. All amplifiers have the ability to do this but the 2nd input (the cathode of the input tube) is usually just grounded.

Essentially you make a connection from the cathode to pin 3 of the XLR input connector via a coupling cap. If the amp is equipped with a cathode bypass capacitor on the input tube that is the cap that is used, if not, you add one. The hardest part is mounting the XLR input connector on the chassis. If any of this sounds even slightly mysterious have a technician do it for you. The cathode input connection is very low impedance, but our preamps have no problem driving that. I've been using this type of connection for years on several different amplifiers.
OTL?
@dbphd , yes- an OTL is a tube amplifier without an output transformer. In our case, the output of the amp is direct-coupled (so our our preamps).
Ralph, may I order your adapters directly from you?  I couldn't see how to order on your site directly.  I'd like to try the adapters first, then I'll consider sending you the pre for modifications.

Thank you very much for your help.
Sure, but just so you know Cardas and many others make adapters that will do the job. Just make sure no matter who you order from that pin 1 and pin 3 must be tied together.