Nelson,
Is there something about FETs that makes them more immune to RF?
I watch for overall reactions in the field. Being out here in the hinterlands, I don't have anyone to use as a listening panel. There's not one single person around here whose hearing I trust--half of them can't tell you which end of the room the speakers are in with their eyes closed. (Nor would I trust them to put batteries in my flashlight.) The next best way I can cross check my ears is to see if there's a consensus out in the "real" world. Naturally, there will be some who say that any given circuit is the best thing since sliced bread; others will say it's devil-spawned. If I discount the extremes I can sometimes see a trend among those in the middle. Yes, it's a flawed research strategy, I know that, but it's all I've got.
When it comes to something like wide bandwidth, it's even more difficult because there are so many other factors involved and the benefits (if any--maybe I'm mis-identifying the origin of the sound qualities I'm hearing) of wide bandwidth are so subtle. In the final analysis, I have to rely on my own judgement, but it would be interesting to see if I'm in a minority or if there's a broader sense of agreement.
Given the increasing amount of RF in the world due to computers, cell phones, etc. I'm probably advocating a doomed position anyway. The advent of "smart houses" and such things will eventually make wide bandwith gear impractical for everyone.
Richard,
Thanks for the schematic, that made things clearer. How do you envision adjusting bias?
For the record, I have no opinion pro or con on lateral MOSFETs. The reason I suggested them was that it would give Richard's circuit a better chance of working than the IRF-style vertical MOSFETs. The laterals are very difficult to get here in the US and quite expensive (at least five times more costly than IRF parts). I've never bothered to try to get any.
Grey
Is there something about FETs that makes them more immune to RF?
I watch for overall reactions in the field. Being out here in the hinterlands, I don't have anyone to use as a listening panel. There's not one single person around here whose hearing I trust--half of them can't tell you which end of the room the speakers are in with their eyes closed. (Nor would I trust them to put batteries in my flashlight.) The next best way I can cross check my ears is to see if there's a consensus out in the "real" world. Naturally, there will be some who say that any given circuit is the best thing since sliced bread; others will say it's devil-spawned. If I discount the extremes I can sometimes see a trend among those in the middle. Yes, it's a flawed research strategy, I know that, but it's all I've got.
When it comes to something like wide bandwidth, it's even more difficult because there are so many other factors involved and the benefits (if any--maybe I'm mis-identifying the origin of the sound qualities I'm hearing) of wide bandwidth are so subtle. In the final analysis, I have to rely on my own judgement, but it would be interesting to see if I'm in a minority or if there's a broader sense of agreement.
Given the increasing amount of RF in the world due to computers, cell phones, etc. I'm probably advocating a doomed position anyway. The advent of "smart houses" and such things will eventually make wide bandwith gear impractical for everyone.
Richard,
Thanks for the schematic, that made things clearer. How do you envision adjusting bias?
For the record, I have no opinion pro or con on lateral MOSFETs. The reason I suggested them was that it would give Richard's circuit a better chance of working than the IRF-style vertical MOSFETs. The laterals are very difficult to get here in the US and quite expensive (at least five times more costly than IRF parts). I've never bothered to try to get any.
Grey
GRollins said:
GRollins, yes, it’s what I have in mind, but in this case I would rather use the 2SK246/2SJ103 pair with a high Idss (7/8 mA.) and as you pointed it, the Hitachi lateral mosfets as output devices. Unfortunately for both cases I have to use 2 current sources !!! and just like the capacitors I don’t like as well the current sources, I always prefer a resistor, but I must work on this subject more in depth, in some cases resistors are not practicable.
GRollins said:
The output devices source resistors could be slightly adjust to set the correct bias together with the leds choice green or red as well as the current trough them. Eventually the mosfets also could be matched to reach the bias compound properties.
I have been listening to the F4 on the Abby-clones for a while now. The Abby's are ofcourse an easier load than my ProAc clones and the F4 overall seems to be at home in this setup, with the NS10 as preamp. The F4 can drive the Abby's to really high sound levels, seemingly without loosing the grip at any time. It has more control than the Zen's and Aleph's in the same wattage range. All music genres comes through as they should. Listening to acoustic Delta blues and jazz is intimate and engaging. Power Blues and heavy, comes through in a realistic way too. I think the F4 is one of the most versatile amps I have heard yet. Soundstage is very precise, I beleive mostly because of the extended and detailed J-fet topend? Good firm bottomend, deep and clear cut. Voices are very good and natural.
I will stop now, trying to keep both feets on the ground, allthough its hard not to be very enthusiastic about an amp sounding as great as the F4
Steen
I will stop now, trying to keep both feets on the ground, allthough its hard not to be very enthusiastic about an amp sounding as great as the F4
Steen
Attachments
steenoe said:I have been listening to the F4 on the Abby-clones for a while now. The Abby's are ofcourse an easier load than my ProAc clones and the F4 overall seems to be at home in this setup, with the NS10 as preamp. The F4 can drive the Abby's to really high sound levels, seemingly without loosing the grip at any time. It has more control than the Zen's and Aleph's in the same wattage range. All music genres comes through as they should. Listening to acoustic Delta blues and jazz is intimate and engaging. Power Blues and heavy, comes through in a realistic way too. I think the F4 is one of the most versatile amps I have heard yet. Soundstage is very precise, I beleive mostly because of the extended and detailed J-fet topend? Good firm bottomend, deep and clear cut. Voices are very good and natural.
I will stop now, trying to keep both feets on the ground, allthough its hard not to be very enthusiastic about an amp sounding as great as the F4
Steen
how's on vacation......
accus recharged.....?
steenoe said:I have been listening to the F4 on the Abby-clones for a while now. The Abby's are ofcourse an easier load than my ProAc clones and the F4 overall seems to be at home in this setup, with the NS10 as preamp. The F4 can drive the Abby's to really high sound levels, seemingly without loosing the grip at any time. It has more control than the Zen's and Aleph's in the same wattage range. All music genres comes through as they should. Listening to acoustic Delta blues and jazz is intimate and engaging. Power Blues and heavy, comes through in a realistic way too. I think the F4 is one of the most versatile amps I have heard yet. Soundstage is very precise, I beleive mostly because of the extended and detailed J-fet topend? Good firm bottomend, deep and clear cut. Voices are very good and natural.
I will stop now, trying to keep both feets on the ground, allthough its hard not to be very enthusiastic about an amp sounding as great as the F4
Steen
Well, it's not really the amp, but the supra baffles on the Abbey's that makes it sound so fantastic....trust me it is....would I lie to you??
BTW, have you noticed those nice looking supra baffles those Abbey's got?
Magura
Thanks, just great. Have a look at the pic. The Azorer's look like that! Man, I never took more than 8 hours to drive 80 km! Had to stop all the time for view's
I had more than 600 pic's on SD-cards when I got back. Still sorting them out
I guess this was another OT, on this nice thread.Nope you wouldnt lie. I know only one guy who can produce baffles like those
The Magura man I wouldnt know what to do, without that guy That was another OT. Seems like I am good at that Steen
Attachments
steenoe said:How do you get that "Posted by......" attached to your quotes??
Steen
when you click the checkbox to quote a post, it attaches the message for you.
Abby clones, F4 clones, I would really hate to be the audio dealer in your area Steenoe
I just got my ApexJr order today, so hopefully I can resume working on my F4, then start work on Frugal-Horn, but I have to finish renovating the basement, so it looks like it's going to be a very busy summer for me ...
<- that will be me finishing the basementI understand Richard Perez disire to remove the coupeling caps or at least to make them smaller, What is the reason for having them this big. In simultion they can be 1/10 th of the value and still not sacrifice much more than a few Hz. 2-3 Hz bandwith with 22uF.
Can anyone cast a light on this issue for a loudspeker designer with a solid solidstate DIY fetish.
Can anyone cast a light on this issue for a loudspeker designer with a solid solidstate DIY fetish.
What checkbox? I only have the quote button to hit! When I hit it, I have to paste the text!! I am probably just a dumbass
Dont worry, I am trying to keep it all to myself
I would never want to spoil NP's business Ask him how many amps he sold in DK, lately And how many before I entered the DIY scene Steen
Re: coupling capacitors... There is a theory that the frequency band where capacitors do add distortion is where they have a significant effect on the circuit. At low frequencies, the cap's Xc rises, and so would the distortion. I believe this is the reason so often you see coupling caps with values such that the -3db point would be about 2Hz. 3 to 4 octives higher, where there is music, the distortion would be negledgable
steenoe said:What checkbox? I only have the quote button to hit! When I hit it, I have to paste the text!! I am probably just a dumbass
Dont worry, I am trying to keep it all to myself
Steen
steen my man
on bottom of this post you have "quote " little field
check it and just click reply on bottom of page
tip- you can quote more than one post
flg said:Re: coupling capacitors... There is a theory that the frequency band where capacitors do add distortion is where they have a significant effect on the circuit. At low frequencies, the cap's Xc rises, and so would the distortion. I believe this is the reason so often you see coupling caps with values such that the -3db point would be about 2Hz. 3 to 4 octives higher, where there is music, the distortion would be negledgable
If this is the case the 22uf should be sufficient. At least if simulations are just a little right. 22 uF is app 2 Hz bandwith.
I suspect there may be other reasons for selecting big caps other than bringing frequency response down to 1/10 Hz
The revison ll of the circuit allows for gratervoltage swings so more power is possible without going into bridge mode. This could be good for us with speakers of more modest effecincy.
Michael
MiiB said:
I wanted to try out the quote thing
Regarding the voltage swing, you really need a preamp that is a shotgun! I didnt try the rev. 0 of this circuit, but it still needs a pretty good preamp! I had the NS10 running at full throttle with the Abby-clones!! No sign of clipping and no sign of cone breakup!!!!! Pretty unusual.So, my conclusion is: NP; give us that preamp
Steen
Here a simplified schematic to show the means of avoiding capacitors of my first post ,well... it's nothing else than a diamond follower!
In the schematic post 421 2*TL431 can be used to set the bias in lieu of leds for a more practical bias setting.
F4_Diamond
In the schematic post 421 2*TL431 can be used to set the bias in lieu of leds for a more practical bias setting.
F4_Diamond
steenoe said:All music genres comes through as they should. Listening to acoustic Delta blues and jazz is intimate and engaging. Power Blues and heavy, comes through in a realistic way too. I think the F4 is one of the most versatile amps I have heard yet. Soundstage is very precise... Voices are very good and natural.
Steen
Wait and see to when those Fostex are really broken in.
Good to see you back after some nice vacations…
Cheers
Nice it works.steenoe said:
I wanted to try out the quote thing
So, my conclusion is: NP; give us that preamp
Steen
A circuit could then be a cascoded jfet pair as mosfet or bipolar 2. stage and the F4 input jfets at the driver stage. Could be like the circuit I posted earlier. with an input running at 60 V volts and an output stage at 40 V I know you then have to decrease the current through the output fets but as its running in Class A-B that should pose no problem. Or you could add more Fet's if full sving should stay in Class A for the first 80 W (Quite A monster)