Ray Samuels Audio A-10 Thunderbolt II

Audio Addict

Headphoneus Supremus
A-10 Thunderbolt II
Pros: Provides the SR-009 / SR-009S with a full musical spectrum
Includes full function preamplifier section for 2 channel systems.
Cons: Only supports electrostatic headphones
Expensive (requires NOS for best performance)
Only 2 left to be built
On March 29, 2009 Ray introduced the A-10 Thunderbolt II to Head-Fi. The 1st post of the earlier link describes Ray's design for the A-10 Thunderbolt II. Since then, Ray has continued to improve the A-10 as even the early A-10 had some of the same electrostatic restrictions as other similar electrostatic amplifiers. It had the speed and clarity but in my opinion they all still lack really natural sub-bass and bass and just left you wanting. As I looked back through that thread, I saw I was extremely excited about the A-10 but found myself hesitant about going down the electrostatic rabbit hole. For over 10 years I was able to keep myself out of electrostatic systems even while listening to them at meets and shows.

Fast forward to October 2019 and I found myself up at Ray's workshop having my Apache tested out. As I talked with Ray about what he has been doing since slowing down in the headphone amplifier world, he told me he made some changes to the A-10 and I should hear them. I really didn't want to since I had avoided this rabbit hole for over 10 years but ended up going upstairs to his home and listening to his personal A-10 Thunderbolt with his Stax SR-009. Ray mentioned he had focused on the pairing of the A-10 with the Stax SR-009 and with these latest improvements felt the SR-009 actually was exceeding the sonics of the HE-90s and as such he had sold those. I said "what, you sold your HE-90s? Those and your R10s are the best out there." As many know, Ray just smiles and hands me the SR-009 to have a listen. As they say the rest is history. I could not believe what I heard. My regular day to day listening had been with the Apache and the Focal Utopias. I honestly didn't think it was going to be close but I was wrong.

The SR-009 had the speed and clarity one comes to expect but the entire musical spectrum was now in the presentation. The sub-bass and bass were there in full. They weren't boomy but instead they were at the same level as the speed and clarity of the mid-range and treble. Everything just came together and really pushed this beyond any expectation I had. It really does not seem to matter what I listen to. I can put on a Qobuz playlist and I just sit back and enjoy the music, even if I am not familiar with it. Okay, well not all as there are a few genres I just can't find myself getting into.

I have also had the opportunity to compare the A-10 Thunderbolt II with the SR-009 to his B-52 using either his Sony R-10s or my Focal Utopias. There is no doubt his latest improvements took the SR-009 to a level I never expected.

I spent over a year trying to talk myself out of going down the electrostatic rabbit hole but obviously I failed. For those Star Trek fans, "Resistance is Futile" so I broke down and ordered the A-10 and purchased a pair Stax this year.

This isn't your typical review, just my story of how a headphone amplifier and pair of headphone impacted me and I wish others had the opportunity to experience. This truly is what Summit Fi is about. This listening experience just creates such an emotional connection to the music and brings out so much realism.

As I write this summary on New Year's Eve, I wish everyone a great new year and hope your search for musical connections can be fulfilled as mine has been with the A-10 and the Stax headphones.
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Audio Addict
Audio Addict
Ray has just finished another update for the A-10. It is supposed to slightly extend the bottom and top end. Also improved is the amplifier's power output. Even Ray can't use all the available output. I plan to take mine up later in the month for the update.
John Massaria
John Massaria
Awesome man I like ray he’s the the best
After I got my A-10 totally redone by Ray, it was better but still seemed for some music, not enough power but so enjoyable, I was good with that. Then time went on, and on and even though I have much time on the redo, it continued to mature. A few hundred hours and few more and then volume increased? What? The dynamics, the energy, bass, transparency all increased. As did layering. I prefer not to go above 85dB on peaks but now it can do over 90 on peaks with complex music, without issue!

If anyone is reading this and has the A-10 and you haven't had it updated, I strongly suggest you do. The Voce (new earpads), the HE90 and Jade II, all sound excellent on this. I am a little blown away by the realism!