would it be easy to change the gain so as it could be used as a linestage also? I would like a switch so I can go from 26db to 0 db gain if that is possible.
thanks arthur
thanks arthur
Luke said:
Yes it certainly is possible. 🙂
You could rig a switch(or two) for RF to change gain.
Gain is a smidge less than RF/RG. Something like this:
G = .95 * (RF/RG);
So you could wire switch for RF a number of ways, but the best way might be to switch a parallel resistor in with RF which would be calculated to get unity gain. That way you don't ever rob the amp of feedback should you switch while powered on.
Cheers!
Russ
PCB Wiring Check
Hi folks,
I thought this thread might have continued a bit longer, but it has fizzled out.
Maybe Steen or ZenMod, or anyone else with a little bit of time on their hands:
Based on Zenmod's circuit "Jfet cascoded CCS-ed BOSOZ for Steenoe"
Could you just check over this PCB for dumb wiring mistakes please? I have not "streamlined" anything yet, but thought I would get the basics out of the way first.
Also, am I better off with a little heatsink on the Jfet and the CCS? I put them in because I am not especially space limited (famous last words) and because the components of the CCS seemed to it nicely in the gap between the two heatsinks anyway.
Steen, did you ever build this circuit?
(I am starting with a blank slate, and have bought parts suitable for Babelfish-J-X and should probably consider a new pre-amp too. Having said that, there will be a great big fat active crossover between any pre-amplifer and the amplifiers - Linkwitz Orions are the speakers, so the "match" between pre-amp and amp becomes a bit more distant.)
Regards,
George.
Hi folks,
I thought this thread might have continued a bit longer, but it has fizzled out.
Maybe Steen or ZenMod, or anyone else with a little bit of time on their hands:
Based on Zenmod's circuit "Jfet cascoded CCS-ed BOSOZ for Steenoe"
Could you just check over this PCB for dumb wiring mistakes please? I have not "streamlined" anything yet, but thought I would get the basics out of the way first.
Also, am I better off with a little heatsink on the Jfet and the CCS? I put them in because I am not especially space limited (famous last words) and because the components of the CCS seemed to it nicely in the gap between the two heatsinks anyway.
Steen, did you ever build this circuit?
(I am starting with a blank slate, and have bought parts suitable for Babelfish-J-X and should probably consider a new pre-amp too. Having said that, there will be a great big fat active crossover between any pre-amplifer and the amplifiers - Linkwitz Orions are the speakers, so the "match" between pre-amp and amp becomes a bit more distant.)
Regards,
George.
Re: PCB Wiring Check
I'll answer you later tonight......
btw - that schmtc need decreasing current through jfets and increasing accordingly of their drain resistors (on top of cascode) , just to preserve them from early clipping ;
problem is that - when you decrease current through jfets to achieve max level of and sym clipping, mosfets aren't happy anymore with that tiny current.
in that form - jfets cascoded with mosfets, this preamp is just compromise.
go and build Pumpkin,if nothing better
btw- where is your pcb
GeorgeBoles said:
I'll answer you later tonight......
btw - that schmtc need decreasing current through jfets and increasing accordingly of their drain resistors (on top of cascode) , just to preserve them from early clipping ;
problem is that - when you decrease current through jfets to achieve max level of and sym clipping, mosfets aren't happy anymore with that tiny current.
in that form - jfets cascoded with mosfets, this preamp is just compromise.
go and build Pumpkin,if nothing better
btw- where is your pcb
I posted too late at night!
Sorry about that Zenmod ... 'twas late at night when I posted and forgot the PCB. Here it is.
Planned for either Ground Plane or Ground "Spider/Star/Tree" on top surface.
I will have a look at your new options at "work" today!
Again this is mainly just to get "connections right" at this stage.
Regards and thanks,
George.
Sorry about that Zenmod ... 'twas late at night when I posted and forgot the PCB. Here it is.
Planned for either Ground Plane or Ground "Spider/Star/Tree" on top surface.
I will have a look at your new options at "work" today!
Again this is mainly just to get "connections right" at this stage.
Regards and thanks,
George.
Attachments
Re: I posted too late at night!
hehe
don't expect from me that I can check layout......... too much different things on my mind this days, I can check it and say that's good ......even if isn't ........ 😉
I'm just no reliable right now.....
GeorgeBoles said:
hehe
don't expect from me that I can check layout......... too much different things on my mind this days, I can check it and say that's good ......even if isn't ........ 😉
I'm just no reliable right now.....
Zenmod,
Woohoo ... That was a quick response. All I have had time to do was to change the colours so they didn't hurt the eyes, and you still beat me to a response!
Don't get me wrong, please. I don't "expect" you to check it. To check someone else's PCB must be boring and time consuming. It was only as a request for anyone who might have time.
Tahnks and regards,
George
Woohoo ... That was a quick response. All I have had time to do was to change the colours so they didn't hurt the eyes, and you still beat me to a response!
Don't get me wrong, please. I don't "expect" you to check it. To check someone else's PCB must be boring and time consuming. It was only as a request for anyone who might have time.
Tahnks and regards,
George
GeorgeBoles said:
I would do that ,gladly...... but...... brain is too fuzzy..... 😉
edit:
steen certainly made that circ and he sez that sounds pretty good....better than origigi one...... but he also tell that clipping was bad.......that's the reason why these corrections are made .
mebbe with J309 or 310 you can stay in 10mA per side bracket ,and with IRFs as cascode
Re: PCB Wiring Check
Hi George. Yes I did build it and found that it sounded great with the F4. I didnt find it so so great with my A-X's with the 20dB gainsetting afterwards, though. Lowering the gainsetting to 12 dB helped a bit, but it still didnt sound right. To augment the listening impression (actually in that order!) the scope showed clipping on the positive curve. I am not sure why, but with the F4 I was thrilled with the sound. Well....
You dont need heatsinks, nothing gets hot at that current rate.
If you like'em, feel free to use'em.
If you want to persist, following the X-BosoZ route I suggest you try the BJT cascoded version that ZM posted here:
http://www.diyaudio.com/forums/showthread.php?postid=1253001#post1253001
That version looks kind of healthier, somehow. I know its annoying for you, having me saying that after you designed a pcb, but.... If I wasnt busy, enjoying the holidays with the boys right now, I would build it and hear for myself😉 My boys are really heating up for a serious fishing expediton over the next few weeks, so you will have me excused if I dont answer back 😎
Steen🙂
GeorgeBoles said:
Hi George. Yes I did build it and found that it sounded great with the F4. I didnt find it so so great with my A-X's with the 20dB gainsetting afterwards, though. Lowering the gainsetting to 12 dB helped a bit, but it still didnt sound right. To augment the listening impression (actually in that order!) the scope showed clipping on the positive curve. I am not sure why, but with the F4 I was thrilled with the sound. Well....
You dont need heatsinks, nothing gets hot at that current rate.
If you like'em, feel free to use'em.
If you want to persist, following the X-BosoZ route I suggest you try the BJT cascoded version that ZM posted here:
http://www.diyaudio.com/forums/showthread.php?postid=1253001#post1253001
That version looks kind of healthier, somehow. I know its annoying for you, having me saying that after you designed a pcb, but.... If I wasnt busy, enjoying the holidays with the boys right now, I would build it and hear for myself😉 My boys are really heating up for a serious fishing expediton over the next few weeks, so you will have me excused if I dont answer back 😎
Steen🙂
Thanks for info
Dear ZenMod and Steen,
I am not too distressed about designing a PCB and having to do it again ... much better than making the thing and then having to work out why it is not "quite right" with my extreme inexperience.
I will look at the altered designs and make appropriate modifications.
In the meantime, I will put some 2SK30A jfets in my NS10 dual rail clone and see how that goes. It has the advantage that I only have 50 Volt power supply capacitors, and I will need much higher voltage for any of the CCS-BOSOZ designs.
Steen, did you ever get a power supply sorted out for the NS10 to your satisfaction?
Regards,
George.
Dear ZenMod and Steen,
I am not too distressed about designing a PCB and having to do it again ... much better than making the thing and then having to work out why it is not "quite right" with my extreme inexperience.
I will look at the altered designs and make appropriate modifications.
In the meantime, I will put some 2SK30A jfets in my NS10 dual rail clone and see how that goes. It has the advantage that I only have 50 Volt power supply capacitors, and I will need much higher voltage for any of the CCS-BOSOZ designs.
Steen, did you ever get a power supply sorted out for the NS10 to your satisfaction?
Regards,
George.
I've been experimenting with different preamps to feed the F4 and this is what made a wining combo: modified BOSOSZ-CCS and F4 without input buffer (one stage less in the signal chain). Preamp delivers 21 V peak with 2.8 V peak input (2V RMS) which is enough to fully drive F4.
-8 V supply (V5 on sch.) is made from -23V for F4 (with 7908 chip). For 60V supply (V4 on sch.) I use separate transformer and LM317.
Right now it's a working prototype (a mess realy) but it sounds extremely good. Compared to mini aleph and GC-SuSy this baby wins in every aspect of the game (probably due to the lack of global feedback).
Now, there will be some serious metalwork (case, heatsinks) so don't hold your breath for pictures of the finished amp.
Once again, thanks a 10e6 Mr. Pass !
-8 V supply (V5 on sch.) is made from -23V for F4 (with 7908 chip). For 60V supply (V4 on sch.) I use separate transformer and LM317.
Right now it's a working prototype (a mess realy) but it sounds extremely good. Compared to mini aleph and GC-SuSy this baby wins in every aspect of the game (probably due to the lack of global feedback).
Now, there will be some serious metalwork (case, heatsinks) so don't hold your breath for pictures of the finished amp.
Once again, thanks a 10e6 Mr. Pass !
Attachments
What a winning combination!!!
My guess is that it sounds as clean as you can want it. Just in case the 2V RMS input sensitivity is a little on the lower side, a crazy idea would be to precede the input stage with a JFET BOZ, adjusting the gain to bring the whole amp to deliver max. power with a 1V RMS input sensitivity.
As a bonus, the JFET BOZ should add a bit of warmth and romance to the overall sound.
I know this is crazy, but it seems like the best of all worlds!
My guess is that it sounds as clean as you can want it. Just in case the 2V RMS input sensitivity is a little on the lower side, a crazy idea would be to precede the input stage with a JFET BOZ, adjusting the gain to bring the whole amp to deliver max. power with a 1V RMS input sensitivity.
As a bonus, the JFET BOZ should add a bit of warmth and romance to the overall sound.
I know this is crazy, but it seems like the best of all worlds!
Samuel Jayaraj said:
Well, 2V RMS is standard output value from most of digital sources, but
if you want to increase sensitivity it's enough to decrease the value of 47 Ohm resistor (the one that connects the sources of two IRF510's).
Juma, thanks for the reply.
If another F4 is run off the Drain of Q6, would it be possible to bridge the amp without any offset problems?
Juma, tell us a little more about how it sounds.
Thanks.
If another F4 is run off the Drain of Q6, would it be possible to bridge the amp without any offset problems?
Juma, tell us a little more about how it sounds.
Thanks.
Samuel Jayaraj said:
Yes, another F4 could be run from Q6's (IRF510) drain in order to bridge them. Offset can be regulated by means of P2 in F4.
Sound is clean and true, but involving and unobtrusive. Acoustic material sounds a bit warm. Dynamic is high and stage is very wide and deep. Details are present but the whole presentation is balanced, nothing pokes you in the eye (ear).
This is my impression after two days listening. Now I'll have to tear the prototype apart in order to build it properly.
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