Craig405 said:
Yes and no. As usual, the Gerber files will be available on my web site for free, so you can build your own. But don't expect me to sell any boards, life is to short for that.
syn08 said:
For those who prefer a less smeared copy, please contact me.
I don't think the PGP and VSOP amps are the most appropriate examples to explain the ins and outs of this version of the active clamp. The crux is the additional feedback provided by R111 and R172 (not so obvious at first sight). These two simple resistors greatly improve the stability of the clamping FB loop (that is, at least in the PMP and MCP amp).
syn08 said:
If we take a closer look at your latest creation, what the heck do we see? Right, R141 (1k). So this OPS has gotten some voltage gain, 1.1 times. Apparently you too have recognized that a little bit of gain has some advantages: no need for an elevated PSU for the front end. Simply derive it from the main PSU.
Now I wonder what will be the next idea that you will adopt, ETMC or a NDFL version of the Alexander amp, or maybe even both. I really hope so, as it saves me a lot of work. 😀
Edmond Stuart said:
A couple of years ago I was involved in a particularly obnoxious patent troll research project and came across a patent that almost read onto the Alexander amp. It was titled in a way that put in under an unexpected classification IIRC. Has anyone run across this? I've lost the reference. BTW someone managed to get some basic current feedback claims issued in 1998.
patent
Nope, I'm sorry Scott.
The modified Alexander amp I was referring to can be found here:
http://www.diyaudio.com/forums/showthread.php?postid=1776548#post1776548
Cheers,
Edmond.
Nope, I'm sorry Scott.
The modified Alexander amp I was referring to can be found here:
http://www.diyaudio.com/forums/showthread.php?postid=1776548#post1776548
Cheers,
Edmond.
Very nice looking amp Syn08 - congratulations and thanks for sharing it with us.
Its great to see working amps of this calibre vs a lot of discussion and opinions about 'vapour amps'.
Its great to see working amps of this calibre vs a lot of discussion and opinions about 'vapour amps'.
syn08 said:
Thanks a lot. I am reading this and if I may, I will come back with some questions.
Here is a first one:
from a weak non linear point of view ( no crossover, no slewing, no saturation) do you expect this current topology to behave better than a voltage one ?
JPV
syn08 said:
Thanks a lot. I am reading this and if I may, I will come back with some questions.
Here is a first one:
from a weak non linear point of view ( no crossover, no slewing, no saturation) do you expect this current topology to behave better than a voltage one ?
JPV
JPV said:
Not sure I understand the question, but anyway I'm in L.A. on business for the rest of the week. I'll be back over the weekend and try to figure it out.
THD simulation
Hello syn08
Congratulations on your new amp.
I have one question and that relates to THD simulations with PSPICE how low does it simulate at 20Khz 80Vpp , and do you have problems with the package when it comes to THD simulations. The reason I ask this is because I had real problems getting consistent low THD sims even when the circuit was known to be a good performer THD wise.
Regards
Arthur
Hello syn08
Congratulations on your new amp.
I have one question and that relates to THD simulations with PSPICE how low does it simulate at 20Khz 80Vpp , and do you have problems with the package when it comes to THD simulations. The reason I ask this is because I had real problems getting consistent low THD sims even when the circuit was known to be a good performer THD wise.
Regards
Arthur
syn08 said:
Let me rephrase it.
If we have to compare the distortion performance of your current mode audio power amplifier to a voltage mode audio power amplifier and limit ourself to weak non linearities in the circuit, is there a definitive advantage of one topology.
I am excluding hard non linearities like slew rate because there it is obvious and like crossover distortion because it is difficult to model and i believe that the problem is equivalent for both topologies except if using feedback we have more desensitivity at high frequency with one topology
I am considering I vs V non linear characteristic , non linear capacity and non linear early effect.
there are two aspects to the answer: one is low distortion due to use of circuit tricks that could be used in any topology and second, lower distortion specific to the topology.
JPV
Gopher said:
Hello Gopher
Can you give us an example of a silly 80's amp that achieved 0.0001% at 20Khz 100Watts into 8R.
Regards
Arthur
Great work, syn08
Thanks for sharing
I would be glad if you answer a few questions:
1. What exactly are the models and parts used for simulation, respectively, for the amplifier? I mean complementary 2SA1381/2SC3503 transistors - SANYO or Fairchild? Fairchild offers models 2SA1381/2SC3503 and KSA1381/KSC3503, but they are different. Models for 2SA1381/2SC3503 are newer (and may be better?)
2. Is it a good idea to use Toshiba's 2SA1360/2SC3423 instead of 2SA1381/2SC3503 (KSA1381/KSC3503) in this amp? Is there a requirement for best VAS performence like in PGP?
3. What are Vz for references LM285 and LM385? Both have 1.235V and 2.5V versions according to TexInst's and NatSemi's datasheets. Is there any reason not to be used only LM385?
4. What is the model for LME49710 used in YAP v2.1 simulation? NatSemi offers LME49860 instead of LME49710.
5. Do you plan to post info for YAP v2.1 on www.synaesthesia.ca - schematics, PCBs, measurements and comments?
Thank you
Thanks for sharing
I would be glad if you answer a few questions:
1. What exactly are the models and parts used for simulation, respectively, for the amplifier? I mean complementary 2SA1381/2SC3503 transistors - SANYO or Fairchild? Fairchild offers models 2SA1381/2SC3503 and KSA1381/KSC3503, but they are different. Models for 2SA1381/2SC3503 are newer (and may be better?)
2. Is it a good idea to use Toshiba's 2SA1360/2SC3423 instead of 2SA1381/2SC3503 (KSA1381/KSC3503) in this amp? Is there a requirement for best VAS performence like in PGP?
3. What are Vz for references LM285 and LM385? Both have 1.235V and 2.5V versions according to TexInst's and NatSemi's datasheets. Is there any reason not to be used only LM385?
4. What is the model for LME49710 used in YAP v2.1 simulation? NatSemi offers LME49860 instead of LME49710.
5. Do you plan to post info for YAP v2.1 on www.synaesthesia.ca - schematics, PCBs, measurements and comments?
Thank you
JPV said:
"weak" and "hard" non linearities, I'm not sure I understand this sort of metric.
This amp is proof of a) what can be done by using current feedback topologies b) what can be done by using nested feedback loops and proper frequency compensation and c) the type of frequency compensation is irrelevant, from a distortion and stability perspective, it's a multiple options game.
kl said:
1. Fairchild
2. I haven't tried the Toshiba pair, but looking at the data sheet they should be ok.
3. LM285 should be here 2.5V and LM385 should be 1.2V
4. All LME voltage feedback audio opamps from National share the same topology and model.
5. Absolutely. It will last some time though, YAP 2.1 is going to get case, power supply, auxilliary circuitry, etc... following the PGP model.
traderbam said:
The definition of "signal path transistors" is to me highly subjective, but then again, as you said, I'm not really keen of this sort of metric. I do appreciate simplicity, but only for the purpose of keeping projects manageable and maintenable.
This amp is about the same complexity as the first YAP and has extra features (clean clipping, better overload protection). If somebody could get the same performances while significantly simplifying the signal path, I would appreciate clues.
The VSOP amp was certainly simpler, but I was not really happy with the results. It's very good, but the trouble is with the lead compensation in the global loop. While this was required for stability, it introduced a load dependency of the phase margin I was not really happy with. It was still unconditionally stable, but the pulse response depends on the reactive load, something that I consider clearly audible.
I haven't done and sound evaluation and comparations with the PGP, ML333, etc... but I did listen a little to the YAP 2.1 and I can tell so far, all the PGP issues are gone. Perfornces in 4ohm loads are much better, etc...
How it sounds trumps how many parts it has. I'd like to hear it. Unfortunately, an ocean separates us.
syn08 said:
Weak non linearity is defined as a non linearity where the power serie ( taylor expansion) around an operating point is converging and where the energy is concentrated in the fundamental and first harmonics with therefore a decrease of level of higher harmonics. We can then approximate the non linearity by looking at the first terms of the power expansion
Good examples are I vs V characteristic of bjt or Mos ( or equivalent non linear Gm), non linerar capacitance, non linear Early effect.
Bad examples are slewing or cross over distortion ( derivatives are not continuous or do not exist)
One question is: is current mode topology better than voltage mode to decrease distortion caused by weak non linearities?
JPV
JPV said:
Not sure, but I don't think so. The advantages of current feedback toplogies in audio are the same as for any current feedback opamp, and as outlined in the TI white paper I quoted above. Probably any base amp gain topology can be included in (or modified for) a current feedback loop.
The current feedback technology has nothing to do with the open loop non linearities, be they "weak" or "hard" as you defined them.
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