Spatial Audio Raven Preamp

@donsachs @lynn_olson I have been looking at maybe purchasing the  preamp for a couple months and have a few questions. I have a nice SS state amp but it is not balanced or have zero feedback.  What will be the benefit of the Raven Preamp if  the amplifier is not balanced or has zero feedback.  Does this negate all the benefits of the Raven or is it a cumulative thing?  

@brbrock It is a cumulative thing.  Especially if your source is a DAC with balanced output.  The Raven will happily communicate with all things RCA on both input and output.  The gain is slightly less because XLR is a 5V swing and RCA is at most 2.5V.  But the Raven will work fine with anything.  That said, it can be in the middle of a fully balanced system, which has advantages.   I am pretty sure Spatial has a 45 day return policy with little or no restocking fee.  So you would just be out the shipping to try one.

I would say if your SS amp can be driven to clipping by 1.5 V or less, you will be just fine.

The Raven accomplishes several things at once:

1) Moderate voltage amplification (from the 6SN7).

2) Substantial current multiplication (from the internal step-down transformer).

3) Signal conversion from either RCA or XLR to RCA, XLR, and headphone outputs.

4) Volume control via stepped resistor array, with L/R balance control on the remote control, as well as volume and input selection.

5) Signal conditioning, with removal of DC offsets *and* RFI interference, and breaking of ground loops between components (via transformer coupling).

So it’s not just a preamp or passive volume control. These benefits extend to all types of power amplifiers ... Class A or Class AB transistor, Class D Mosfet or GanFET, or triode or pentode tube amplifiers.

RFI break-in is the bane of modern hifi gear, since most homes are bathed in microwave signals from WiFi, Bluetooth, and RFI noise from multiple switching supplies in TVs, computers, various gizmos that use ARM processors, etc. etc. Just scraping off all this RFI cruft before it gets to an analog circuit can make quite a difference in low-level sonics ... no more barely-audible buzz or hash getting into the power amplifier.

The classic tube preamps of the Fifties and Sixties were designed at a time when nearly all homes were RF silent. No computers, WiFi, Bluetooth, or switching supplies. No wall-warts. None of that. The only RF-noisy places were TV studios (15.75 kHz TV sync buzz is everywhere), AM and FM transmitters, microwave relay towers, or military installations ... where isolation transformers were routinely used to isolate and suppress RFI incursion into audio signal paths. We are applying the same isolation technology used back then, with custom transformers that are designed with modern computer modeling software.

RFI = Radio Frequency Interference

EMI = Electromagnetic Interference (includes magnetic fields)

15.75 kHz (or close to it) is the horizontal scanning rate of 525/60 NTSC (color or monochrome) analog television. The 625/50 PAL or SECAM rates are similar. Analog television environments were notorious for high interference levels, as well as electrical noise from early SCR light dimmers for on-set illumination.

Modern television is digital from camera, to signal processing, to transmission or storage, to decoding and display. No more sync noise, just computer hash at MHz frequencies.

My Raven preamplifier from Spatial Audio Labs arrived today and I thought I would post initial impressions.  More folks should be receiving theirs any day now so additional comments from them will be helpful.  The packaging was first rate and the box itself looked like it had been hand carried from the next town over.  Everything was pristine inside the double box and the finish on the preamp was perfect.  The only change in my system today was swapping my Ayre K-1xe preamp for the new Raven.  Everything else is the same.  The Raven has a cherry base and I upgraded the standard 6SN7 tubes to the Linlai elite version.  I let the preamp idle for an hour before listening to female vocals, then instrumental, then male vocals, female, etc... After only a few minutes listening the word that struck me first was REFINEMENT. There was no grain as one might expect with only one hour burn in.  Initially, I was pleasantly surprised how similar the Raven was to the Ayre; clearly better but not by a wide margin.  However, the gap began to widen over the next several hours.  Music was fluid, clear (like a sense of zero distortion), natural, well balanced top to bottom, and became more beautiful and emotionally engaging with every song I played.  I am astounded how good this thing is after only 3 hours.  I will provide more detail next week after spending more time listening but there is no question in my mind that this is an amazing preamp and I will be keeping mine.  I look forward to getting 20+ hours on it and reading the impressions of other new owners.