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
Last edited by a moderator:
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 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.