Couple of new additions to the stable
Options
I found an extremely well built DIY First Watt amplifier that somehow utilized a stock chassis. These are typically not commercially available. Nelson Pass has been using this enclosure since the Aleph 30 since about 2001. Still uses the same chassis today for all First Watt creations.
This is a DIY audio First Watt F6 rev.2
I am extremely impressed with the builders skill and attention to detail. Looks almost as well built as the commercial F6. I've been looking to purchase a DIY First Watt product for awhile, but honestly many look very haphazardly put together and homemade chassis just looked "cheap".
The workmanship here is exceptional which gives me confidence this will run as expected for a long time. The potted transformer is huge! This weighs about 50lbs. 25/50 wpc 8/4 ohm. 60,000uF per channel. And of course the price was right
The thing with the DIY F6 is the power Jfets are Mosfet's not the exotic SIT (Vfet) as those are unobtanium. Or rather Nelson bought all that are in existence even paid to have them (Semi South) make a special run. Semi South is no longer in business.
The F6 is a very simple Class A push-pull design which uses N channel power
Fets driven by a high quality line level transformer which splits and isolates the
drive signal to the output stage while also serving as the feedback element for
the amplifier. In this way loop feedback operates locally over a single gain
stage.
The output devices are operated in “Square Law Class A” where the conducted
current is a square function of the Gate-Source voltage. With a constant bias
voltage, this creates a Class A operating envelope for the output stage which
allows both halves to remain in healthy forward conduction for output currents
about three times the bias figure, resulting in an approximate doubling of Class
A output power.
The bias of the F6 is high enough to reach the 25 watt Class A figure even
without the square law effect, but it is helpful in delivering more current at lower
distortion into lower impedance loads. Keep in mind that this not some fancy
bias circuit – this is what push-pull Class A Fets do naturally if you don't saddle
them with the usual ballast resistors.
So, while he is extremely generous, he didn't make the SITs available for this project. Which is totally understandable as he's still working with SIT Jfet designs.
For those interested attached is good read about the development of the First Watt F6, which was never intended to be a commercial product.
It sounds fantastic in the office rig. Soundstage is HUGE!
The second addition is a new pre-amp for the main rig. Ever since the Galion TS P75 pre-amp has been on my radar I've become very impressed with the professional accolades and owner experiences. I figured if I could find a lightly used one I'd give it a listen. I missed a couple FS because they sell almost instantly. But I finally jumped on a barely used unit.
It uses a bank of Clarity ESA, Solen Silver and Bumble Bee caps to help with impedance matching. Uses (4) 12AT7's. A pair for voltage gain and a pair for buffer impedance matching.
I still have a small stash of higher end 12AT7's left over from my Dared SL2000 days. Never get rid of everything, never know when you might need it again....lol. I also just purchased true NOS 50's Brimars and 50's Tung Sol's from a UK dealer. This isn't going to be a "rolling machine" like the Avant. I'm going to try a handful of combo's, find the best, and set it and forget it.
So far it's impressive. I swapped the stock Psvane 12AT7's with a pair of 1956 Valvo Hamburg D getter ECC81's in the voltage gain stage and a pair of 1957 Sylvania 6201 black plate gold pin tubes in the buffer stage. Wowzers! SDA hugeness!
Not had a lot of listening time yet, but will do a full review when the time comes. If this works out, like @nooshinjohn , I'm done chasing.
H9
This is a DIY audio First Watt F6 rev.2
I am extremely impressed with the builders skill and attention to detail. Looks almost as well built as the commercial F6. I've been looking to purchase a DIY First Watt product for awhile, but honestly many look very haphazardly put together and homemade chassis just looked "cheap".
The workmanship here is exceptional which gives me confidence this will run as expected for a long time. The potted transformer is huge! This weighs about 50lbs. 25/50 wpc 8/4 ohm. 60,000uF per channel. And of course the price was right
The thing with the DIY F6 is the power Jfets are Mosfet's not the exotic SIT (Vfet) as those are unobtanium. Or rather Nelson bought all that are in existence even paid to have them (Semi South) make a special run. Semi South is no longer in business.
The F6 is a very simple Class A push-pull design which uses N channel power
Fets driven by a high quality line level transformer which splits and isolates the
drive signal to the output stage while also serving as the feedback element for
the amplifier. In this way loop feedback operates locally over a single gain
stage.
The output devices are operated in “Square Law Class A” where the conducted
current is a square function of the Gate-Source voltage. With a constant bias
voltage, this creates a Class A operating envelope for the output stage which
allows both halves to remain in healthy forward conduction for output currents
about three times the bias figure, resulting in an approximate doubling of Class
A output power.
The bias of the F6 is high enough to reach the 25 watt Class A figure even
without the square law effect, but it is helpful in delivering more current at lower
distortion into lower impedance loads. Keep in mind that this not some fancy
bias circuit – this is what push-pull Class A Fets do naturally if you don't saddle
them with the usual ballast resistors.
So, while he is extremely generous, he didn't make the SITs available for this project. Which is totally understandable as he's still working with SIT Jfet designs.
For those interested attached is good read about the development of the First Watt F6, which was never intended to be a commercial product.
It sounds fantastic in the office rig. Soundstage is HUGE!
The second addition is a new pre-amp for the main rig. Ever since the Galion TS P75 pre-amp has been on my radar I've become very impressed with the professional accolades and owner experiences. I figured if I could find a lightly used one I'd give it a listen. I missed a couple FS because they sell almost instantly. But I finally jumped on a barely used unit.
It uses a bank of Clarity ESA, Solen Silver and Bumble Bee caps to help with impedance matching. Uses (4) 12AT7's. A pair for voltage gain and a pair for buffer impedance matching.
I still have a small stash of higher end 12AT7's left over from my Dared SL2000 days. Never get rid of everything, never know when you might need it again....lol. I also just purchased true NOS 50's Brimars and 50's Tung Sol's from a UK dealer. This isn't going to be a "rolling machine" like the Avant. I'm going to try a handful of combo's, find the best, and set it and forget it.
So far it's impressive. I swapped the stock Psvane 12AT7's with a pair of 1956 Valvo Hamburg D getter ECC81's in the voltage gain stage and a pair of 1957 Sylvania 6201 black plate gold pin tubes in the buffer stage. Wowzers! SDA hugeness!
Not had a lot of listening time yet, but will do a full review when the time comes. If this works out, like @nooshinjohn , I'm done chasing.
H9
"Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | Galion TS P75 Pre | Holo Audio Cyan 2 Dac | MIT Shotgun S1 | Puritan Audio PSM136 Pwr Condtioner & Classic PC's | Legend L600 | Roon Nucleus 1 w/LPS - Tubes add soul!
Comments
-
That’s a huge transformer for the wattage of that amp.
Mucho reserves for sure.
Always wanted to try the 5. -
Glad to see you got the you got the Pre you were eying Brock enjoy.Home Theater
Parasound Halo A 31 OnkyoTX-NR838 Sony XBR55X850B 55" 4K RtiA9 Fronts CsiA6 Center RtiA3 Rears FxiA6 Side Surrounds Dual Psw 111's Oppo 105D Signal Ultra Speaker Cables & IC's Signal Magic Power Cable Technics SL Q300 Panamax MR4300 Audioquest Chocolate HDMI Cables Audioquest Forest USB Cable
2 Channel
Adcom 555II Vincent SA-T1 Marantz SA 15S2 Denon DR-M11 Clearaudio Bluemotion SDA 2.3tl's (Z) edition MIT Terminator II Speaker Cables & IC's Adcom 545II Adcom Gtp-450 Marantz CD5004 Technics M245X SDA 2B's, SDA CRS+
Stuff for the Head
JD LABS C5 Headphone Amplifier, Sennheiser HD 598, Polk Audio Buckle, Polk Audio Hinge, Velodyne vPulse, Bose IE2, Sennheiser CX 200 Street II, Sennheiser MX 365
Shower & Off the beaten path Rigs
Polk Audio Boom Swimmer, Polk Audio Urchin
