Sorry I should have provided more details.
I got the best sound using a 20K ohm passive preamp (glassware audio ladder/series attenuator). I also tried my B1 (which sounded great on the Parasound) but it did not sound very good with the F2J.
My sources are a Salas Folded Simplistic phono preamp and a Musical Fidelity V90-DAC.
I don't have a quality preamp with gain, but the system would play loud enough for me with the 96 dB efficient Vulcans.
Very nice amplifiers well executed .I have a similar pair of f2j pseudo mono blocks ie power supply in a separate enclosure then the amplifier boards in left and right enclosures.
I would like to pick your brains ie the rc filter.As i have a pair of medallion horn speakers with lowther silver coil pm6 drivers.Having read the notes that nelson pass has written on rc filters could not get my head round them would you be willing to share the values you used and how you wired them together so that i would have a place to start.the odd photo would be really helpful as aim dyslexic and some times struggle to get my head round things.Regards Spades
I would like to pick your brains ie the rc filter.As i have a pair of medallion horn speakers with lowther silver coil pm6 drivers.Having read the notes that nelson pass has written on rc filters could not get my head round them would you be willing to share the values you used and how you wired them together so that i would have a place to start.the odd photo would be really helpful as aim dyslexic and some times struggle to get my head round things.Regards Spades
spades, regarding the parallel RC filter I read the First Watt article and used the values given in the article for a speaker very similar to mine (see the chart on p7) and started with the closest values I had in my parts bin. Increasing the R value will result in less attenuation because less current will bypass the driver. Increasing the C value will lower the frequency that the attenuation begins and will also cause more rolloff on the higher frequencies.
The reccomended values from the article for the Fostex FE206E (I am using an FE206EN) were R = 4.7 ohm and C = 15 uF. I found (by ear) this rolled off the high frequencies too much for me so I tried C = 10uf which was not enough reduction of the highs, so I tried C = 13uF and that is where I am now. When I have some time I will take measurments, but for now the overall balance of highs and lows is pleasant to my ear.
Hope this helps.
Chas
Edit:
Link to First Watt Article http://www.firstwatt.com/pdf/art_cs_amps.pdf
The reccomended values from the article for the Fostex FE206E (I am using an FE206EN) were R = 4.7 ohm and C = 15 uF. I found (by ear) this rolled off the high frequencies too much for me so I tried C = 10uf which was not enough reduction of the highs, so I tried C = 13uF and that is where I am now. When I have some time I will take measurments, but for now the overall balance of highs and lows is pleasant to my ear.
Hope this helps.
Chas
Edit:
Link to First Watt Article http://www.firstwatt.com/pdf/art_cs_amps.pdf
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Thanks for the suggestion, I initially connected the speakers with reverse polarity thinking that the F2 was a phase inverting amp, but I don't see this in the F2 manual so I could be wrong about this. From a practical standpoint, I tried reversing the polarity this afternoon and listened to various types of music for an hour or so. I think inverting the polarity may have made a subtle change, but not too significant.
I did spend a bit more time on the RC filter and on speaker positioning and found improvement from both. The F2 manual says that the F2 is a "tinkerers amp", and in this way it really does create some nice options for tuning in the high efficiency full range drivers it was made for. I am confident that the amp is working properly and I will enjoy "tinkering" with it some more to see how I can affect the sound.
There is another relavent comment in the F2 manual:
"It’s interesting to investigate the difference in sonic character that comes from a 2nd versus 3rd harmonic character. Conventional wisdom descended from tube amplifiers has it that 2nd harmonic is known for its warmth and romantic character while 3rd harmonic offers greater dynamic range and clarity.
While these observations don’t necessarily apply to solid-state amplifiers, they pretty much correspond to the sounds of the F1 and F2. If you prefer a good push-pull tube, you are more likely to want the F1. If you like the more lush midrange of a single-ended triode, you would probably gravitate toward the F2."
This is why I was thinking that maybe I just prefer the push-pull sound that I am accustomed to. I don't want anyone to think that it is not a good sounding amp I think it is, it just doesn't make me sit back in my listening chair and say "Ah - this is what I was looking for."
my second AB 100 - or better to call it the AB60 ( 60 W @ 8R and 95 @ 4R).
I've been listening to it for a month now, the right panel mount blue LEDs still haven't arrived - so the wires are not yet properly arranged and temporary Leds installed.
I've been listening to it for a month now, the right panel mount blue LEDs still haven't arrived - so the wires are not yet properly arranged and temporary Leds installed.
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Applause!
thank you, ordering this leds has been going on for me for a long time - initially i ordered a 6mm 24V led from china but did not like the machining - rough metal traces visible..so i ordered 8mm ans 12mm flash mount type Led - they are still on the way ... but probably had to take APEM LEDs (I've used them before) , expensive - but nice.
