pabbi1
Cavalli Audio Spiritual Advisor
- Joined
- Jan 12, 2004
- Posts
- 3,879
- Likes
- 38
Caveat: I am an unabashed advocate for this design, having originally asked the designer (well, and Pete Millett) for a different electrostat amp approach more than a year ago. While others have driven the exact specs, I have watched this evolve from inception, and prototyped every step, and yes, with some bitter disappointment along the way.
Further disclosure: I also have another design that is more complicated (with greater expectations and ambitions) that will get equal attention upon completion.
The eXStatA is a new electrostatic amp design from Alex Cavalli that was born of the desire for a DIY Stax compatible amp that bettered the options available currently, while being less intimidating to build. For those who don't venture into the DIY forum often, the build thread may give insight not found on the website.
Cost NOT an evaluation criteria for this review, so no quarter is being granted for cost considerations.
I have been withholding this review through several iterations of this amp as there were things that, IMHO, needed resolution before exposing it to the community at large. Anyone who watches the DIY forum is well aware that there is a new electrostatic amp, quite capable of driving all stats, pro and regular bias, with a superior price to performance ratio. And, in the same performance bands as anything up to the (quite arbitrary) $2000 price point, and possibly beyond. All my concerns have been addressed with the latest iteration.
This design is buildable by intermediate level DIY builders, without any lead time for fab, or exotic parts. While there is still a product maturity curve at work, I have a working unit now that proves this is at the threshhold of absolute viability. Extended Beta is in process, but should validate these findings over the next couple of months.
There are, as of now, the Winter Solstice, approximately ten units functioning and being used. Bits and pieces of impressions are here and there, but I hope the concentration will be added here. Two intermediate prototypes were at the Houston meet in October, and feedback there made for one last major change to address concerns to meet ORIGINAL spec, NOT to move to a substantially higher level of performance.
Is it the best stat amp ever? NO, at least not yet, and nor does it aspire to be. The technical specs (1000Vpp) leave it shy of other designs (BH at 1800Vpp, for instance), though the difference in cost is a significant multiple (in my case almost 5x) and tubes are definitely an order of magnitude or worse. Only head to head comparisons, which have NOT been done, will answer those questions, and is beyond my capability to answer currently. But, those answers are coming within the next 30 days, especially after the DFW meet on Jan 23rd.
That said, the relative merits of a stat amp are NOT measured by Vpp alone.
The eXStata design has both Solid State and Hybrid (tube) flavors, where I strongly favor tubes. There is a single tube type, the 6s4a, which runs $5-10, well, in realistic transactions (and yes many eBay vendors want more, along with their $5 shipping). Tube Depot lists these tubes at $3.95, which is what I estimate the market to be. There are a LOT of different construction types, but no data yet if the design is sensitive to tube variations, or not.
Chain definition:
Source: Cambridge Azur 840c
Phones: Sennheiser he60 (reterminated with an Amphenol silver Stax plug - no adapter)
Cables: APS silver cored copper XLR
Power cords: Quail
Source material:
NIN - Pretty Hate Machine
Radiohead - Amnesiac, OK Computer
Tool - Lateralus, 10000 Days, Aenima
Allison Krause - New Favorite
Rhianna - Good Girl Gone Bad
Godsmack
Marcy Playground
Hoobastank - The Reason
Rolling Stones - Sticky Fingers
Oasis - Stop the Clocks
Beck - Sea Change
Mudvayne - "Fall Into Sleep" (single)
Brandenburg Concertos
Listening Impressions:
Superior instrument seperation
Superior vocal seperation
Superb soundstaging (instrument and vocal positioning)
Outstanding resolution and presentation of microdetail
Crisp and precise percussion - NO sibilance (not that I am sensitive to it anyway)
Bass resonance, timbre, punch and pitch - reproduces lower registers accurately, with all the transients expected in bass notes - not just "something 'down there"
Balanced presentation from top to middle to bottom - nothing traded off at other spectrum's expense
No clipping (this was an issue with the intermediate proto builds without the ccs on certain Tool cuts, but a RARE occurrance)
Plenty of gain driving he60 (TBD with OII)
Emotionally involving - not a truth for all 'accurate' stat amps
Just a fun amp
Weaknesses:
None yet defined
Summary:
Here is a new electrostatic amp, superior to the commonly available Stax amps, and most other designs I have heard or owned to date. It was meant to perform on par (or better) than the venerable SRM-T1 and it's lesser ilk (srm-252, srm-323, Sennheiser hev-70) and even challenge the higher end units, and has, IMHO acheived this design goal. It is definitely on par with the best new production Stax amp, and in the same discussion with all the non-Stax amps I have heard (Woo, KGSS, KGBH, HEV-90 and ES-1). From memory, the ES-1 and BH may be "better", but it would be a split decision depending on the judges, and criteria for measurement.
This is a fun, extremely capable amp. It uses cheap, readily available tubes (6s4a), and is an easy build as electrostatic amps go. Though it does not aspire to be the best electrostatic amp, it is in the same conversation nonetheless.
This is an answer to a long desired intermediate level DIY stat amp that raises the performance of even modest stats (STAX 202, Stax 303), and the ideal driver for he60 and Koss ESP950. For OII owners, the jury is still out, mainly because I have not yet heard this version with them.
Two thumbs up - even if I am the most partial advocate for this amp.
Money shots:
Further disclosure: I also have another design that is more complicated (with greater expectations and ambitions) that will get equal attention upon completion.
The eXStatA is a new electrostatic amp design from Alex Cavalli that was born of the desire for a DIY Stax compatible amp that bettered the options available currently, while being less intimidating to build. For those who don't venture into the DIY forum often, the build thread may give insight not found on the website.
Cost NOT an evaluation criteria for this review, so no quarter is being granted for cost considerations.
I have been withholding this review through several iterations of this amp as there were things that, IMHO, needed resolution before exposing it to the community at large. Anyone who watches the DIY forum is well aware that there is a new electrostatic amp, quite capable of driving all stats, pro and regular bias, with a superior price to performance ratio. And, in the same performance bands as anything up to the (quite arbitrary) $2000 price point, and possibly beyond. All my concerns have been addressed with the latest iteration.
This design is buildable by intermediate level DIY builders, without any lead time for fab, or exotic parts. While there is still a product maturity curve at work, I have a working unit now that proves this is at the threshhold of absolute viability. Extended Beta is in process, but should validate these findings over the next couple of months.
There are, as of now, the Winter Solstice, approximately ten units functioning and being used. Bits and pieces of impressions are here and there, but I hope the concentration will be added here. Two intermediate prototypes were at the Houston meet in October, and feedback there made for one last major change to address concerns to meet ORIGINAL spec, NOT to move to a substantially higher level of performance.
Is it the best stat amp ever? NO, at least not yet, and nor does it aspire to be. The technical specs (1000Vpp) leave it shy of other designs (BH at 1800Vpp, for instance), though the difference in cost is a significant multiple (in my case almost 5x) and tubes are definitely an order of magnitude or worse. Only head to head comparisons, which have NOT been done, will answer those questions, and is beyond my capability to answer currently. But, those answers are coming within the next 30 days, especially after the DFW meet on Jan 23rd.
That said, the relative merits of a stat amp are NOT measured by Vpp alone.
The eXStata design has both Solid State and Hybrid (tube) flavors, where I strongly favor tubes. There is a single tube type, the 6s4a, which runs $5-10, well, in realistic transactions (and yes many eBay vendors want more, along with their $5 shipping). Tube Depot lists these tubes at $3.95, which is what I estimate the market to be. There are a LOT of different construction types, but no data yet if the design is sensitive to tube variations, or not.
Chain definition:
Source: Cambridge Azur 840c
Phones: Sennheiser he60 (reterminated with an Amphenol silver Stax plug - no adapter)
Cables: APS silver cored copper XLR
Power cords: Quail
Source material:
NIN - Pretty Hate Machine
Radiohead - Amnesiac, OK Computer
Tool - Lateralus, 10000 Days, Aenima
Allison Krause - New Favorite
Rhianna - Good Girl Gone Bad
Godsmack
Marcy Playground
Hoobastank - The Reason
Rolling Stones - Sticky Fingers
Oasis - Stop the Clocks
Beck - Sea Change
Mudvayne - "Fall Into Sleep" (single)
Brandenburg Concertos
Listening Impressions:
Superior instrument seperation
Superior vocal seperation
Superb soundstaging (instrument and vocal positioning)
Outstanding resolution and presentation of microdetail
Crisp and precise percussion - NO sibilance (not that I am sensitive to it anyway)
Bass resonance, timbre, punch and pitch - reproduces lower registers accurately, with all the transients expected in bass notes - not just "something 'down there"
Balanced presentation from top to middle to bottom - nothing traded off at other spectrum's expense
No clipping (this was an issue with the intermediate proto builds without the ccs on certain Tool cuts, but a RARE occurrance)
Plenty of gain driving he60 (TBD with OII)
Emotionally involving - not a truth for all 'accurate' stat amps
Just a fun amp
Weaknesses:
None yet defined
Summary:
Here is a new electrostatic amp, superior to the commonly available Stax amps, and most other designs I have heard or owned to date. It was meant to perform on par (or better) than the venerable SRM-T1 and it's lesser ilk (srm-252, srm-323, Sennheiser hev-70) and even challenge the higher end units, and has, IMHO acheived this design goal. It is definitely on par with the best new production Stax amp, and in the same discussion with all the non-Stax amps I have heard (Woo, KGSS, KGBH, HEV-90 and ES-1). From memory, the ES-1 and BH may be "better", but it would be a split decision depending on the judges, and criteria for measurement.
This is a fun, extremely capable amp. It uses cheap, readily available tubes (6s4a), and is an easy build as electrostatic amps go. Though it does not aspire to be the best electrostatic amp, it is in the same conversation nonetheless.
This is an answer to a long desired intermediate level DIY stat amp that raises the performance of even modest stats (STAX 202, Stax 303), and the ideal driver for he60 and Koss ESP950. For OII owners, the jury is still out, mainly because I have not yet heard this version with them.
Two thumbs up - even if I am the most partial advocate for this amp.
Money shots:
