No problem dear Nando...go ahead!
they have not perceived...so...this is fine.
Go ahead my dear...your posts are fine.... i think you shake a lot with the thread.
Tamonáboa...ficapeixe.
Carlos
they have not perceived...so...this is fine.
Go ahead my dear...your posts are fine.... i think you shake a lot with the thread.
Tamonáboa...ficapeixe.
Carlos
Hi !!
I would like to know, if I swap the MPSA18 with 2N5551, will the amp change the gain?
Thanks a lot !
I would like to know, if I swap the MPSA18 with 2N5551, will the amp change the gain?
Thanks a lot !
R29 and R30 !? So, the gain isn't 40, it's 45 as the R29 is 22K, and R30 is 499R. 22 / 0,49 = 44,8979 😱 Is this right!?
So, if I want to go with a Bi-Amp configuration with Symasym for the woofer and LM3886 for the tweeter, I must use the same resistors, so 22K and 499R. Am I right?
Best Regards !
So, if I want to go with a Bi-Amp configuration with Symasym for the woofer and LM3886 for the tweeter, I must use the same resistors, so 22K and 499R. Am I right?
Best Regards !
Hi -_nando-_,
Those are the feedback parts. Don't change them. Why not pad the inputs down with a semi fixed resistor? This way you can correct for the difference in driver efficiencies.
The tweeter is almost always far more efficient than the woofer.
-Chris
Those are the feedback parts. Don't change them. Why not pad the inputs down with a semi fixed resistor? This way you can correct for the difference in driver efficiencies.
The tweeter is almost always far more efficient than the woofer.
-Chris
No problem with the feedback resistors and the amp gain, but I must build an LM3886amp that have the SAME gain as the Symasym, because I already have a frequency cut and tweeter attenuation before the amps, so I must have two amps with exactly the same gain. So, should I build an LM3886 using the same feedback resistors that Symasym is using?
Hi Nando,
the gain for a non-inverting amplifier is [Rupper/Rlower]+1
the gain of this amp is 22,000/499+1=45.09
The gain of a chipamp is either the same as above for a non-inverting topology,
or
for inverting topology Gain=Rupper/Rlower.
The chipamp resistor values do not have the be the same.
The RATIO determining the gain must be the same.
For example an inverting chipamp with Rin=499(Rlower) and Rfeedback=22k(=Rupper) will have a gain that is a little low, but the serious problem is that Zin is ONLY 499ohms. A less serious problem is that the gain of any inverting amplifier changes with changes in the source resistance (Rs) feeding the amplifier. Small changes from 50 to 100ohms for Rs will make only a little difference in gain. A big change from 0ohms to 2500ohms will completely change the chipamp gain (this would happen with a 10k passive pot for voulune control).
You can scale (raise by the same factor) the feedback resistors around the NFB loop of an inverting amplifier. 68k/[1k5+Rs]=45.33 (getting close) if Rs=8r2 then the gains match. Get your calculator out and play with some numbers.
the gain for a non-inverting amplifier is [Rupper/Rlower]+1
the gain of this amp is 22,000/499+1=45.09
The gain of a chipamp is either the same as above for a non-inverting topology,
or
for inverting topology Gain=Rupper/Rlower.
The chipamp resistor values do not have the be the same.
The RATIO determining the gain must be the same.
For example an inverting chipamp with Rin=499(Rlower) and Rfeedback=22k(=Rupper) will have a gain that is a little low, but the serious problem is that Zin is ONLY 499ohms. A less serious problem is that the gain of any inverting amplifier changes with changes in the source resistance (Rs) feeding the amplifier. Small changes from 50 to 100ohms for Rs will make only a little difference in gain. A big change from 0ohms to 2500ohms will completely change the chipamp gain (this would happen with a 10k passive pot for voulune control).
You can scale (raise by the same factor) the feedback resistors around the NFB loop of an inverting amplifier. 68k/[1k5+Rs]=45.33 (getting close) if Rs=8r2 then the gains match. Get your calculator out and play with some numbers.
Hi Andrew,
Yes.
My suggestion was to build each amp with the recommended feedbak values and either amplify or attenuate as required.
-Chris
Yes.
My suggestion was to build each amp with the recommended feedbak values and either amplify or attenuate as required.
-Chris
STRANGE behavior !
I built an LM3886 amp using the same feedback resistors that symasym uses, but the LM3886 sounded MUCH louder than Symasyn ! When I apply a signal to the inputs (generated by trueRTA), LM3886 shows a higher voltage on the output.
The system was sounding awful.
I tried to compensate the gain diference, but the MOST strange is that, at lower frequencies, Symasym shows higher voltage than LM3886, and at high frequencies (since 200hz) LM3886 shows more voltage.
I could not use Symasym with LM3886. I'm using two LM1875 now, and the system is singing ok again.
I think that I'll make passive crossovers with the frequency cut that I'm using, and use only one amplifier, with the tweeter attenuated trought resistor. What you think?
I built an LM3886 amp using the same feedback resistors that symasym uses, but the LM3886 sounded MUCH louder than Symasyn ! When I apply a signal to the inputs (generated by trueRTA), LM3886 shows a higher voltage on the output.
The system was sounding awful.
I tried to compensate the gain diference, but the MOST strange is that, at lower frequencies, Symasym shows higher voltage than LM3886, and at high frequencies (since 200hz) LM3886 shows more voltage.
I could not use Symasym with LM3886. I'm using two LM1875 now, and the system is singing ok again.
I think that I'll make passive crossovers with the frequency cut that I'm using, and use only one amplifier, with the tweeter attenuated trought resistor. What you think?
Hi -_nando-_,
The SymAsym has what I would consider to be a low input impedance. The feedback values from the SymAsym probably do not simply "plug into" another amp design.
-Chris
The SymAsym has what I would consider to be a low input impedance. The feedback values from the SymAsym probably do not simply "plug into" another amp design.
-Chris
Yeeeeesssss that was my guess, but I didn't consider it, but that's what it really seems to be ! 😀
That's right. Now LM3886 is with 39K/1K for feedback, 32Db of gain, the same as the announced symasym gain, and it's working fine !
Qual é a tua?.... ficou dôido?...what is going on Nando
Are you kidding?
Comparing Symassym with LM3886....my God!
You must be kidding.
regards,
Carlos
Are you kidding?
Comparing Symassym with LM3886....my God!
You must be kidding.
regards,
Carlos
Dear Carlos,
Hide your weapons my friend, I'm not comparing these amplifiers. Symasym is MUCH better than LM3886.
I'm just asking here about the GAIN of the Symasym, because as I want to make a Bi-Amped system, I must have two amps with the same gain. If I'll use a LM3886, or a single end tube class-A amp as the secondary amp, doesn't matter. I must know the gain of Symasym to match with the other amp.
If I live near you, I would invite you to drink a beer at the beach, to relax a little...
Hide your weapons my friend, I'm not comparing these amplifiers. Symasym is MUCH better than LM3886.
I'm just asking here about the GAIN of the Symasym, because as I want to make a Bi-Amped system, I must have two amps with the same gain. If I'll use a LM3886, or a single end tube class-A amp as the secondary amp, doesn't matter. I must know the gain of Symasym to match with the other amp.
If I live near you, I would invite you to drink a beer at the beach, to relax a little...
Nando, the easiest solution would seem to be building another pair of Symasyms for the tweets.😉
PinkMouse, believe me, LM3886 for the tweeter is doing well. Smooth trebles, not clear as Symasym, but it's ok. LM3886 performs BAD in mid / bass region, laid back mid with shy bass, so Symasym is driving the woofer 😉
I'll build passive crossovers to use only one amplifier (symasym), as I don't like bi-amped systems very much.
I'll build passive crossovers to use only one amplifier (symasym), as I don't like bi-amped systems very much.
That bass lose of power you have with the chip is easy to fix, just increase a...
condenser value.
But i think the distance, quality distance, related Symassym and this chip makes every kind of comparison a scandal.
There's no possibility to compare aluminium shine with gold shine... distance of shine quality is enormous.... the same related that chip.
Those protections it has Nando, the overcurrent, the limits it has, all those things killed the sonics....... of course it is good...but compare to Symassym?... a beetle with a BMW.... the possible comparison could be the number of sales of one compared to the other..... but performance?
pirou?
regards,
Carlos
condenser value.
But i think the distance, quality distance, related Symassym and this chip makes every kind of comparison a scandal.
There's no possibility to compare aluminium shine with gold shine... distance of shine quality is enormous.... the same related that chip.
Those protections it has Nando, the overcurrent, the limits it has, all those things killed the sonics....... of course it is good...but compare to Symassym?... a beetle with a BMW.... the possible comparison could be the number of sales of one compared to the other..... but performance?
pirou?
regards,
Carlos
-_nando-_ said:
I build chip amps as well, I have several, and I like them. But I think that in the above sentence you have made my point for me. 😉
power supply
I have succesfully built SymAsym5_3, and it is in fact dead silent when I use 2 laboratory-psu's however when I connect it to my 300VA 30-0-30 (some 42V peak DC) transformer I can hear a little 50hz hum. My question now is if this might be because my filter caps (4 x 4700uF) are too small?
I have succesfully built SymAsym5_3, and it is in fact dead silent when I use 2 laboratory-psu's however when I connect it to my 300VA 30-0-30 (some 42V peak DC) transformer I can hear a little 50hz hum. My question now is if this might be because my filter caps (4 x 4700uF) are too small?