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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
whitestix OP
721 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
721 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. 
gdhal's avatar
gdhal
1,641 posts
 
Pardon my seemingly confusion but genuine curiosity in this thread.

I’m assuming "DIY" is "do it yourself". However, when I check the first watt FAQ page http://www.firstwatt.com/faq.html there is a question specific to Do you really build them yourself? to which the response is Yes, until this last year, when my son Colin and nephew Sean began helping with assembly. I’m assuming that means Nelson himself is building the amp.

Can the OP or someone else please clarify if the first watt amps are something Nelson Pass or the end consumer is building? Thanks.
kdude66
1,200 posts
 
gdhal,

Both,the production versions of first watts and the "Diy" versions that Nelson gives his blessings to the Diy community.Different models were available as kits on the Diy audio website store.

I own a production version of the F7,and my Sit2 is a Diy version but differs from the production version in that mine is class a push pull and uses Nos Sony Vfet's that were made available in matched pairs,The pwr supply,case and the heat sinks are the same,It just doesn't say first watt on it.

I hope this clarifies your question.

I have heard all the first watts,except the F1,and I have owned the F3,J2,and the F7.I have built the F5 and the F5 turbo version from kits and my Sit2 "Diy" I bought used from audiogon.

Kenny.
kdude66
1,200 posts
 
Whitestix,

The F5 is a little bit aggressive from the upper midrange to the highest frequencys and does tend to have a slightly hard edge to the leading edges of notes.It's basically a very picky amp that needs the best components upstream of it.

This Offcourse is highly system and listener dependent.

Kenny.
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