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DIY Pass Labs First Watt F5 amp impressions

I recently acquired a well- built DIY First Watt F5 amp for the cost of the parts, which is the understanding among those that build the designs that Nelson Pass has made available to the DIY folks.  I have been using a McCormack DNA .05 Deluxe amp and a Don Sachs 6NS7 tube amp to drive my Spatial Audio M4S Turbo S Hologram open-baffle speakers, which are ~94 db efficient.  I have raved about the McCormack amp on this forum, but swapping the F5 for the McCormack amp has been a  sheer revelation.  I have had dozens of tube and class A/B amps my system over the past 4 decades, as well as a couple of very good class D amps recently, but the tonal accuracy and 3-D representation of music with this F5 is simply stunning.  It is offers a glimpse into the inner details of the music.  I do not have the superlatives to describe the musical enjoyment of the addition  this amp provides to my system.  I am put off the heat his amp generates -- similar to that with a tube amp with a quad of KT88's, but it is a fair bargain for the most ruthlessly revealing sound reproduction I have ever heard in my system.  My regret is that I waited so long to have a Nelson Pass-designed amp in my system.  If your speakers are quite efficient, there are several variants in the First Watt line of amps that might be a great match for your system.  Mark at Reno Audio is the guy to help you sort out the best amp for your needs.
Cheers, Mark
whitestix

Showing 10 responses by whitestix

whitestix OP
731 posts
 
Kenny,
We evidently traveled the same path with the Class D amps. I do think they have a lot to commend themselves, but after listening to them for a few weeks, something was missing.  The lacuna of sound is only apparent by comparing it to other amps. Interesting other SS amps you have.  As I mentioned, I have admired Pass gear just like I do fancy car that drive by, but this oppty to get a well-constructed F5 ranks as the all time audio score of my life.  

I swapped my McCormack amp back in place of the F5 after the post above and immediately had a frown on my brow!  It is just two-dimensional compared to the 3-D presentation of the F5.  Folks on this forum might note that I have never had a piece of gear that I did have something good to say about -- very little gear now days sounds bad, I am literally awestruck with the sound of my speakers with the F5.  

In terms of the heat generated by the amp, it is rather like having big tube amp... but never having to bias it or replace pricey tubes.   Cheers. 
whitestix OP
731 posts
 
Larryi,
 Thanks for you keen observations.  I would agree that there is a slightly hard edge to the leading attack of notes with F5.  
whitestix OP
731 posts
 
Pass Labs sells factory-built First Watt amps, as well as panoply of Pass Labs amps.  A great source is Mark at Reno Hifi.  Mine was built by a guy who took the plans that Nelson Pass has generously made freely available for DIY folks.  This fellow then sold it to me for the "price of the component parts."  That is, he did not build and sell it to me as a commercial endeavor for profit, which is antithetical to the intent of Nelson Pass in making the First Watt designs available to DIY guys.   

I will hasten to add that if you are DIY-inclined person, the build of the F5 can clearly be done for a fraction of the cost of a factory-built version and is consistent with the desires of Nelson Pass.  The rub comes when folks use his detailed designs to build his amps for commercial profit.  Reselling such a First Watt as I acquired at the "cost of the component parts" is copacetic, so far as I know.  Others can clarify this understanding.
whitestix OP
731 posts
 
I too await a report on the LTA amp from Kenny.  I seem to recall Julius Futterman might have been a early designer and user of this circuitry. 
whitestix OP
731 posts
 
Update:  I earlier stated that the F5 runs as hot as a tube amp with four KT88 tubes.  That assertion is clearly wrong.  While the F5 runs much warmer than class A/B amps I have had, it generates nowhere near the heat generated by a robust tube amp.  My HK Citation II toasted the self above that in which it resided, but with the F5, the upper shelf is unaffected.  In conclusion, the F5 runs much warmer than a class D or class A/B, but far cooler than a tube amp.  Whitestix
whitestix OP
731 posts
 
I'll bet you are getting very eager to complete the project and fire it up in your system.  I wish I had auditioned a First Watt amp 5 or 6 amps earlier as I would have saved a lot of dough.  Let us know how your masterpiece sounds when it is up and running.  
whitestix OP
731 posts
 
Let me be the first to say that I am very happy to hear you are enjoying the sound of your First Watt amp build!  I have had a ton of amps in the past 45 or so years and the F5, with a pair of compatible speakers, is  a sheer glimpse of audio nirvana.  I will say that my F5 does have a bit of a bright edge to the leading notes of music --- no amp is perfect of course, but it reveals music in my recordings with a visceral impact that I have formerly not heard.  I reckon after a couple hundred hours of burn-in with your amp, you will be even happier.  Cheers, Whitestix
whitestix OP
731 posts
 
Gents,
I just returned from hearing a $6K Bryston 4B3 amp in a pal's system and got home to my system with the F5 warmed up and am hearing artifacts to the same music I was just listening to in my pal's system that were absent in his system.  The Bryston sounded excellent, but it didn't provide the inner glimpse of music that the F5 does.  However, I am biased so take that into account.  

I kinda think I got the sweet spot of the First Watt amps with my F5, but clearly their are nuances to all of them, particularly the more robust version of the F5 that our friend has built. At retail prices, the First Watt amps are reasonably priced, but if you are a DIY sort of guy, they would be an affordable way to have some of the best amplification available, so long as they are compatible with the sensitivity of your speakers.  
whitestix OP
731 posts
 
Kosst,
Great information!  You clearly know your way around electronics. I am going to attend Burning Amp this fall down the road in San Francisco to meet "Papa" again.  It is funny that you mention the KEF LS50's.  I bought them shortly after they came out and drove them with a 175 wpc Plinius 8200 MK II integrated amp and the amp rather struggled to drive them properly. There is no chance a FW amp would be compatible with them.

However, with OB speakers like my Spatial Audio Holograms, DeVores, Omegas, etc, the FW amps are a great match it seems to me.  Forget about Martin Logans and the like, but a pair of Klipsch speakers would sign with these amps.  You and Kenny wisely pointed out in your posts the compatibility issues one needs to be aware of to get the the best performance from the FW variants.  

 



whitestix OP
731 posts
 
Kenny,
Did I miss your post regarding your impressions of the LTA amp you acquired?  Kosst, I am using a Don Sach's 6SN7-based preamp with my F5 and can say that it is a match made in heaven.  I have plenty of gain with my Spatial Audio OB speakers and zero noise.  Mark
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