It looks good! But I'm not sure about the use of an opamp in front of the LM3886, many people there believe in a "less parts better" approach towards Gainclones. I don't know...
And what's that circuit (the first one on page 2)? Is it a speaker protection or a startup delay?
And where do you get LM3886 in Italy? How much you pay?
And what's that circuit (the first one on page 2)? Is it a speaker protection or a startup delay?
And where do you get LM3886 in Italy? How much you pay?
Hi maupenas!
Very nice! Thorsten would like it..
But you have overtaken us! It's ages that my friend pushes me to realize this concept! Though he wants it a bit modified, so as to get "constant power" drive, instead of current drive.
For me, the question is: how this all react with Your speaker? [Mine is a two-way bass reflex]
Did you measure the actual Rout? Stability?
Ciao, George
Very nice! Thorsten would like it..
But you have overtaken us! It's ages that my friend pushes me to realize this concept! Though he wants it a bit modified, so as to get "constant power" drive, instead of current drive.
For me, the question is: how this all react with Your speaker? [Mine is a two-way bass reflex]
Did you measure the actual Rout? Stability?
Ciao, George
Hello,
I've just glanced at your design, so my question is surely silly. How does your speaker protection cope with negative DC offset?
I've just glanced at your design, so my question is surely silly. How does your speaker protection cope with negative DC offset?
A very unusual design. The 3886 is just a power booster for the 318. I wonder how it sounds compared to the more traditional approach. Any problems with stability?
No, it's not a power booster..
Doh, I was not looking close enough at the first glance - so I take it back - it IS a kind of a power booster.. though a tricky one. [it's not a unity gain buffer on the output..]
At first I was only looking at the 3886 circuit. My note was referring to that. I still would like to try one day.
Doh, I was not looking close enough at the first glance - so I take it back - it IS a kind of a power booster.. though a tricky one. [it's not a unity gain buffer on the output..]
At first I was only looking at the 3886 circuit. My note was referring to that. I still would like to try one day.
sorry, analog_sa, as you see, in the meantime also I have recognized it
The opamp controls the output current..
The opamp controls the output current..
So as to be clear: the LM3886 is a voltage controlled bipolar current source in this configuration. It does not have any voltage gain; it has an input voltage/ output current transfer characteristic - which is, in this case, is 100.
And it is stable in this config.
And it is stable in this config.
Overall transfer
While it is true the output stage is transconductance, the overall input / output is voltage amplifier with a nominal gain of 30.
Have someone actually tested this circuit?
The LM318 may be unstable in integrator configuration as presented.
Frequency response and distortion performance at high frequencies worries me a little, with gain dumping capacitors C31 (C32) as shown (but depends on actual values).
Rodolfo
While it is true the output stage is transconductance, the overall input / output is voltage amplifier with a nominal gain of 30.
Have someone actually tested this circuit?
The LM318 may be unstable in integrator configuration as presented.
Frequency response and distortion performance at high frequencies worries me a little, with gain dumping capacitors C31 (C32) as shown (but depends on actual values).
Rodolfo
analog_sa said:
To make it stable at unity gain the value of C31 and C32 is critical.
Value not specified on the schematic.
sorry, my English is not good.
you have enough centered the operation of this circuit.
The LM3886 it's the power "bilateral current source" (National Semi app...), but the Low value of R3 end R20 (0,01 ohm or 20mm jump 05mm wire) create an "modest" Output Impedence of the bridge.
The LM318 controlling all over close loop.
This architecture it's very complex for tuning, but I the have chosen on account of the fantastic integration with the loudspeakers, end the modest "load invariant" propriety.
The close loop stability It's controlled on dominant pole (C33 end C34) end C31 C32 (0-3p3) not used for this configurations.
In the schematic 2 view a simple Power ON speaker delay (2sec) plus -+ DC protections, and power supply. The transformer It's 225 VA 240/25+25Vac, and Diode (Bridge D1, D5) 5A 250V C5000/3300
to attach the preliminary test of my (1 years old) prototype.
Ciao
you have enough centered the operation of this circuit.
The LM3886 it's the power "bilateral current source" (National Semi app...), but the Low value of R3 end R20 (0,01 ohm or 20mm jump 05mm wire) create an "modest" Output Impedence of the bridge.
The LM318 controlling all over close loop.
This architecture it's very complex for tuning, but I the have chosen on account of the fantastic integration with the loudspeakers, end the modest "load invariant" propriety.
The close loop stability It's controlled on dominant pole (C33 end C34) end C31 C32 (0-3p3) not used for this configurations.
In the schematic 2 view a simple Power ON speaker delay (2sec) plus -+ DC protections, and power supply. The transformer It's 225 VA 240/25+25Vac, and Diode (Bridge D1, D5) 5A 250V C5000/3300
to attach the preliminary test of my (1 years old) prototype.
Ciao
I add other technical explanations:
The zobel network doesn't exist intentionally.
The phase shift for RCL network create additional problem of stability,
and not have a positive influence on complex speaker load (I drive loudspeaker, not industrial motors).
This OP-amp "nesting" structure not it's a news.
I have testing various configuration, to optimize the "sound"(and tec. performance).
The circuit to has been tuning with long listenings, not only on laboratory tools.
(various preamp,B&W CM2, DYnaudio Audience52, KEF102 Ref. speaker, ecc...)
to attach the second part of testing (high freq. dissipated perplexity)
ciao
Mauro Penasa
The zobel network doesn't exist intentionally.
The phase shift for RCL network create additional problem of stability,
and not have a positive influence on complex speaker load (I drive loudspeaker, not industrial motors).
This OP-amp "nesting" structure not it's a news.
I have testing various configuration, to optimize the "sound"(and tec. performance).
The circuit to has been tuning with long listenings, not only on laboratory tools.
(various preamp,B&W CM2, DYnaudio Audience52, KEF102 Ref. speaker, ecc...)
to attach the second part of testing (high freq. dissipated perplexity)
ciao
Mauro Penasa
Hi Mauro,
did you choose the LM318 by purpose or it was just what you had in stock?
What are the advantages of such a topoogy over the "regular" one?
You mention a intrinsic tuning difficulty of this amp, any suggestion on how to implement it in case someone wants to try it?
Cheers
andrea
did you choose the LM318 by purpose or it was just what you had in stock?
What are the advantages of such a topoogy over the "regular" one?
You mention a intrinsic tuning difficulty of this amp, any suggestion on how to implement it in case someone wants to try it?
Cheers
andrea
This is the most original design that I have ever seen on this forum. This forum needs more innovation like this; the last thing that we got excited about was putting a freakin' snubber in the power supply (like nobody has ever done that before).
Hi Andypairo,
The LM318 choice it's extremely determinant (for my). I have tested various OP-amp (NE5534, OP27, TL081, TL071 ecc...), but the audio performance (compareted a class A amplifier) are superior.
An other motivation is that the slew-rate of this OPAMP is suited to this application (or all final amplifier device )🙄
I am not able to explain shortly the theme of the topology ( in English ).
eventually if find the time, I will do a little relationship and will translate you.
In brief, say that this type of amplifiers "feelses" the load that in minimum departs comes to be part of the feedback network, on account of the presence of the bridge in exit (or an other high impedance current driver).
No tuning problem (for you, and this schematic).
The recommendation it's a good bypass and short length of
a input network on LM3886 . I have built all the circuit a 100*160mm card, (as in the photo), and abundant stagnated all power copper track.
If have a oscillations problem, increase C33,C34 on 110 or 120 pF.
If to is not enough, added C31,c32 sperimentaly, (1- 3,3 pF).
ciao
Mauro Penasa
The LM318 choice it's extremely determinant (for my). I have tested various OP-amp (NE5534, OP27, TL081, TL071 ecc...), but the audio performance (compareted a class A amplifier) are superior.
An other motivation is that the slew-rate of this OPAMP is suited to this application (or all final amplifier device )🙄
I am not able to explain shortly the theme of the topology ( in English ).
eventually if find the time, I will do a little relationship and will translate you.
In brief, say that this type of amplifiers "feelses" the load that in minimum departs comes to be part of the feedback network, on account of the presence of the bridge in exit (or an other high impedance current driver).
No tuning problem (for you, and this schematic).
The recommendation it's a good bypass and short length of
a input network on LM3886 . I have built all the circuit a 100*160mm card, (as in the photo), and abundant stagnated all power copper track.
If have a oscillations problem, increase C33,C34 on 110 or 120 pF.
If to is not enough, added C31,c32 sperimentaly, (1- 3,3 pF).
ciao
Mauro Penasa
Thank you, macboy
this is the beautiful thing to behaviour this things for "audiophile" passion and not for money.
Mauro
this is the beautiful thing to behaviour this things for "audiophile" passion and not for money.
Mauro
oopss,
I have seen that *.zip files lose the extension during the download. Enough renames the files with .zip final and all works.
Good weekend
Mauro
I have seen that *.zip files lose the extension during the download. Enough renames the files with .zip final and all works.
Good weekend
Mauro