Nice job. Who makes the heat sinks. I have looking at Modu and Conrad. I can get Conrad to answer any email enquiries though. I'm about to start assembling mine.
Chassis with heatsinks come from antek the transformer place. He has them in his ebay store. Very reasonable...
I have been studying the BA1 front end. I have a question...If I wanted to try and breadboard up this front end and use in conjunction with a stock F4 can I omit the + and - bias circuitry and simply use +D as my output?
Basically, RCA in => BA1 +IN => +D => F4 IN.
If I were to omit the bootstrap section would there be any need for R208 & R209 or would this be worth implementing?
Basically, RCA in => BA1 +IN => +D => F4 IN.
If I were to omit the bootstrap section would there be any need for R208 & R209 or would this be worth implementing?
Attachments
F4 Monoblocks for ELS Speakers
I recently bought a pair of Martin Logan Ethos ELS speakers after a revival in my enthusiasm for good old fashioned two channel audio. I was about to buy a pair of Rouge Audio M180 Valve monoblocks when I opened the "Special Gain Edition" of the diyAudio newsletter. With my curiosity aroused, I started reading a few of the articles and posts. Now I am hooked and have given up on the M180's and started to buy parts for a pair of F4 monoblock's instead.
The ML Ethos are hybrid's, with an ELS panel crossing over to a moving coil woofer at 375Hz. An integral crossover and 200Watt Class D amplifier drive this bass unit. So the F4 is basically working the panel which has a nominal 4 ohm impedance dropping to 0.8 ohm at 20KHz when you hit the panel resonance. Sanders Sound Systems have a ESL Amp White Paper about some of the issue with driving ELS speakers.
I know that NPass has tested the F4 at 2 ohms, but there is no mention of 0.8ohms. So I have decide to buck the trend of balanced pairs of amplifers, and build each monoblock as a pair of F4's wired in parallel to give twice the current drive capability and half the damping factor - theoretically a better match to a much lower impedance load.
In one sense, I don't need a pre-amplifier as I have a single source, a Wyred-4-Sound DAC 2 which has a balanced output and a digital volume control. However, I do need about 18db of gain so in keeping with my early love of valves, I have decided to integrate John Bronskie's (of Aikido fame) new "Unbalancer", an balanced input stage with gain driving a cathode follower into each F4 chassis.
I only hope that building the things will take less time than reading the 3000+ post in this thread.
PJG
I recently bought a pair of Martin Logan Ethos ELS speakers after a revival in my enthusiasm for good old fashioned two channel audio. I was about to buy a pair of Rouge Audio M180 Valve monoblocks when I opened the "Special Gain Edition" of the diyAudio newsletter. With my curiosity aroused, I started reading a few of the articles and posts. Now I am hooked and have given up on the M180's and started to buy parts for a pair of F4 monoblock's instead.
The ML Ethos are hybrid's, with an ELS panel crossing over to a moving coil woofer at 375Hz. An integral crossover and 200Watt Class D amplifier drive this bass unit. So the F4 is basically working the panel which has a nominal 4 ohm impedance dropping to 0.8 ohm at 20KHz when you hit the panel resonance. Sanders Sound Systems have a ESL Amp White Paper about some of the issue with driving ELS speakers.
I know that NPass has tested the F4 at 2 ohms, but there is no mention of 0.8ohms. So I have decide to buck the trend of balanced pairs of amplifers, and build each monoblock as a pair of F4's wired in parallel to give twice the current drive capability and half the damping factor - theoretically a better match to a much lower impedance load.
In one sense, I don't need a pre-amplifier as I have a single source, a Wyred-4-Sound DAC 2 which has a balanced output and a digital volume control. However, I do need about 18db of gain so in keeping with my early love of valves, I have decided to integrate John Bronskie's (of Aikido fame) new "Unbalancer", an balanced input stage with gain driving a cathode follower into each F4 chassis.
I only hope that building the things will take less time than reading the 3000+ post in this thread.
PJG
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Thank you Zen Mod! So I was "barking up the right tree" then...I was thinking that since the F4 already has provision for bias and DC Offset that this was the case.
Another crappy cellphone pic...but I have been enjoying the F4...
I had an idea to put the jfetboz before the aikido...and I must say now we are talking!
The jfetboz is almost wide open and the aikido can drive to enormous volume now. I may attempt the burning amp front end and incorporate it inside the F4 chassis.
Oh yea...this thing is DEAD QUIET!!!
I had an idea to put the jfetboz before the aikido...and I must say now we are talking!
The jfetboz is almost wide open and the aikido can drive to enormous volume now. I may attempt the burning amp front end and incorporate it inside the F4 chassis.
Oh yea...this thing is DEAD QUIET!!!
I went with Panasonic TUP series - 35V 39,000uF - ~$15 each from Mouser or Digikey
I would have loved to have gone with RIFA's but they are BIG $$$...I figure If I like the amp enough I would convert...
I would have loved to have gone with RIFA's but they are BIG $$$...I figure If I like the amp enough I would convert...
I also noticed something interesting...listening to the Jazz channel on directv I noticed some distortion especially on female vocals. Some playing around with the aikido and JFETBOZ volumes led me to believe that the JFETBOZ was causing the distortion.
I then reconnected my Yamaha CA-810 that I use for a phono-pre as the pre-preamp. The typical source - directv satellite music - goes to the yamaha then to aikido then to F4...kind of bastardized but I tell you what...watch out the next time the mrs is out!
I have all the parts for the BA front end coming so I will mount them in the F4 chassis, then I can put the CA-810 just to phono duties.
I then reconnected my Yamaha CA-810 that I use for a phono-pre as the pre-preamp. The typical source - directv satellite music - goes to the yamaha then to aikido then to F4...kind of bastardized but I tell you what...watch out the next time the mrs is out!
I have all the parts for the BA front end coming so I will mount them in the F4 chassis, then I can put the CA-810 just to phono duties.
you will need at least 2 caps per rail to have a CRC supply filter which is highly recommended. The "R" part being 3 or 4 paralleled 0.47 ohm 3-5W resistors. The 3W panasonic film resistors from Digikey are really nice.
Are you doing p2p wiring or do you plan to get a PCB for your PSU?
Peter Daniel has a really nice universal PCB allowing 2 caps per rail with an R connecting them. The CViller PSU boards are also very nice and very similar to NP's design. These allow 4 C's per rail.
Are you doing p2p wiring or do you plan to get a PCB for your PSU?
Peter Daniel has a really nice universal PCB allowing 2 caps per rail with an R connecting them. The CViller PSU boards are also very nice and very similar to NP's design. These allow 4 C's per rail.
With an 18V xformer my rails run right at 24.5V - 35V caps give me a better safety margin.
25 would probably work but I feel more comfortable with 35.
Unfortunately the higher the voltage the capacitance options become narrower. 33,000-39,000 is ample per cap... You can always off-board more caps if you like.
25 would probably work but I feel more comfortable with 35.
Unfortunately the higher the voltage the capacitance options become narrower. 33,000-39,000 is ample per cap... You can always off-board more caps if you like.
You can actually use the same 3W panasonic resistors for the source resistors - they are even the same value 0.47R. Just get at least 20-24 of them...more even...this is a very commonly used resistor in many Pass designs...
"generally" more capacitance is better for bass...but the difference between 33 and 39 I would imagine is negligible. I have been running 2X33,000uF per rail on my F5 for a year and it sounds great.
"generally" more capacitance is better for bass...but the difference between 33 and 39 I would imagine is negligible. I have been running 2X33,000uF per rail on my F5 for a year and it sounds great.