Re: Re post 174
Hi,
I have another end use for this amp and it's better (for me) if it uses regular devices. The triple EF shows slightly better THD performance (here) and is more stable. Also, to change it up
The bias solution I used in the Abomination works splendidly, so I can't see a reason to change it, but thanks for pointing out the circuit - I may use it someday.
I'm not ready for FETs yet. Maybe sometime in the future...
I haven't looked at the gain and such in this one, but the Abomination didn't need any such compensation.
atiq19 said:
Hi,
I have another end use for this amp and it's better (for me) if it uses regular devices. The triple EF shows slightly better THD performance (here) and is more stable. Also, to change it up
atiq19 said:
The bias solution I used in the Abomination works splendidly, so I can't see a reason to change it, but thanks for pointing out the circuit - I may use it someday.
I'm not ready for FETs yet. Maybe sometime in the future...
atiq19 said:
I haven't looked at the gain and such in this one, but the Abomination didn't need any such compensation.
I did CFP's and noticed very little improvement.. it is your
widlar CM that will increase OLG... Strange, when I did your
amp thats what I did as well as use the zetex killer Hfe
trannies to get 70+ out of it (abomination)
It looks like your amp is a hybrid of FA2 and 3 (cascode)
Still you have a "lavardin amp" as well as me...
Read this ....http://peufeu.free.fr/audio/memory/memory-5-vas.html
All about cascoded VAS's (fast, fast)
OS
re post 182
you can check necessity of such compensation on your simulator by parallelling a ,say, 2.2uf capacitor at the output..
however, a single parallel cap does not necessarily represent a real life complex x-over network loudpeakers variable impedance.
some real amp testing can bring more practical results.
you can check necessity of such compensation on your simulator by parallelling a ,say, 2.2uf capacitor at the output..
however, a single parallel cap does not necessarily represent a real life complex x-over network loudpeakers variable impedance.
some real amp testing can bring more practical results.
some tuby fun with abomination
in the spirit of 2009,
how about changing fb loop with some twist of 6GM8 (low voltage ) triode...
in this way the amp could be switched from pp to se.....2nd harmonic dominant..
since 6gm8 is low voltage, you don't think about HV.. you may have to shield 6GM8 on actual pcb..
cheers
in the spirit of 2009,
how about changing fb loop with some twist of 6GM8 (low voltage ) triode...
in this way the amp could be switched from pp to se.....2nd harmonic dominant..
since 6gm8 is low voltage, you don't think about HV.. you may have to shield 6GM8 on actual pcb..
cheers
Attachments
Re: re post 182
Hi OS,
Look again, that isn't a CM. It's 2 CCS only different from the Abomination in that it uses a T instead of an LED for bias.
Hi atiq19,
Good tip for the simulator.
Such compensation is easy to tack on after the board is done if I find that it is needed.
If this is anything like the Abomination, it won't be needed - I have tested that amp already with capacitive loads.
Fixed up the schematic:
ostripper said:
Hi OS,
Look again, that isn't a CM. It's 2 CCS only different from the Abomination in that it uses a T instead of an LED for bias.
atiq19 said:
Hi atiq19,
Good tip for the simulator.
Such compensation is easy to tack on after the board is done if I find that it is needed.
If this is anything like the Abomination, it won't be needed - I have tested that amp already with capacitive loads.
Fixed up the schematic:
KLe said:Nice John
Hi KL,
Me being a minimalist again
This only uses two more transistors (total=28).
The question is, is it a better amp? I have massively improved PSR, but below a certain value, this won't be a discernible improvement (IMO).
I have about the same 1k THD. Spectrum of the harmonics I don't trust, but both amps simmed show 2nd stronger than 3rd, with not much up higher. I haven't tested 20k yet.
Loop gain:
Picture perfect.
As I said , it's the cascoded VAS that makes the grade..
I had the exact same plot at 1.1mhz UGwith 47pf Cdom/same VAS..
(63 db at 100hz /-100 phase- UG intersection)
[that is with 68pf]
Much better than "standard" blameless or even symasym
topology(simulation). The question remains, How will a cascoded VAS sound ,(maybe you could tell me as you have heard it..)
The french article earlier in my post and the "magic resistor"
definitely changes the distortion content (stupid low already)
increasing H2. you might want to include pads for the resistor
in case my hunch is right.
Os
I had the exact same plot at 1.1mhz UGwith 47pf Cdom/same VAS..
(63 db at 100hz /-100 phase- UG intersection)
An externally hosted image should be here but it was not working when we last tested it.
[that is with 68pf]
Much better than "standard" blameless or even symasym
topology(simulation). The question remains, How will a cascoded VAS sound ,(maybe you could tell me as you have heard it..)
The french article earlier in my post and the "magic resistor"
definitely changes the distortion content (stupid low already)
increasing H2. you might want to include pads for the resistor
in case my hunch is right.
Os
ostripper said:
Feeling a wee bit queasy this morn'...
That's a dead ringer for this amp! There is magic in these designs, for sure.
As for the sound, well I listened to the Abomination and it sounds very good, very smooth in the mid/high. There seemed to be a slight difference to my Patchwork, but that may have been imagined.
Personally I don't think there would be an audible difference as long as it it working as it should.
Hi KL,
Bain is on the shelf until I get the time and motivation to attack it again. I am encouraged by the recent progress though and think it can be a worthwhile amp to develop.
I'm busy with projects I started and didn't finish - one of which is a phono preamp. I've made several board changes and etched several boards in an attempt to find the most quite one.
Also started and halfway finished a pair of small speakers for my office that will play my new K10A. These have a solid wood baffle with a waveguide carved in for the tweeters. Here's how they look. A bit rough still in this pic, but they have been sanded and look a lot better now:
I'm a sucker for punishment.
Bain is on the shelf until I get the time and motivation to attack it again. I am encouraged by the recent progress though and think it can be a worthwhile amp to develop.
I'm busy with projects I started and didn't finish - one of which is a phono preamp. I've made several board changes and etched several boards in an attempt to find the most quite one.
Also started and halfway finished a pair of small speakers for my office that will play my new K10A. These have a solid wood baffle with a waveguide carved in for the tweeters. Here's how they look. A bit rough still in this pic, but they have been sanded and look a lot better now:
I'm a sucker for punishment.
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