Well, not having measured it you may be right. But the diagram in the assembly manual shows a 470K resistor across the output connectors' to signal ground (RCA), with a 2.2 uF cap for blocking DC behind it (and that's what I installed) ... 
Granted when connected to the above diagram, 470K in parallel with the 33K input of the op-amp would indicate ~ 30K overall impedence ... No? (The manual also indicates the expected load is to be a tube amp with approximately a 30K ohm input impedence.)
Granted when connected to the above diagram, 470K in parallel with the 33K input of the op-amp would indicate ~ 30K overall impedence ... No? (The manual also indicates the expected load is to be a tube amp with approximately a 30K ohm input impedence.)
Thanks bjorno ... obviously I should not have the low pass in the feedback loop = silly me.
Probably just have to go with a passive filter between the summing op-amp and the input of the input of the power amp. ... Oh well, the best laid plans, etc ...
New drawing to follow ... after I read up in an op-amp cookbook ...
Probably just have to go with a passive filter between the summing op-amp and the input of the input of the power amp. ... Oh well, the best laid plans, etc ...
New drawing to follow ... after I read up in an op-amp cookbook ...
Hi Andrew,
Correct, Thank you Andrew for observing the 5534:s are not unity gain stable and a mistake to use for the followers.
The sub circuit models where put together in an old Electronic Workbench program with different opamps for each module but the global setting changed all to 5534 for unknown reason.
E.g. the original phase control used TL072 and the unity gain buffers where all LM833.
I’ve changed all to LM833. See the plot result.
Any low noise unity gain stable op-amp can be used as the signals are at line levels and not critical at all, my friend will use the OPA2134 for all.
b
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I've been looking forward to build a similar circuit but with discrete
components, transistors. I don't really like the sound of IC's so I'm
asking...
Even the best IC's available now have this veiled sound that gives
me this unpleasant characteristic.
In the past there were several designs with transistors, actually
they must be easy to design even though I don't know how to.
Emitter followers all through. Anybody?
Thanks
components, transistors. I don't really like the sound of IC's so I'm
asking...
Even the best IC's available now have this veiled sound that gives
me this unpleasant characteristic.
In the past there were several designs with transistors, actually
they must be easy to design even though I don't know how to.
Emitter followers all through. Anybody?
Thanks
" ... Even the best IC's available now have this veiled sound that gives me this unpleasant characteristic. ..."
You are not completely alone in these feelings ... the new AussieAmplifiers.com "Synergy" series of modular MOSFET amplifiers are made completely discrete FET transistors ... and this is apparently what their quite selective customers want. I use these amp modules and have no complaints, "golden ear" audio wise ... as voltage followers with gain from a tube pre-amp = ...
... But I'm not prepred to design a complete "summing" pre-amp with low pass filter of discrete transistors as yet.
You are not completely alone in these feelings ... the new AussieAmplifiers.com "Synergy" series of modular MOSFET amplifiers are made completely discrete FET transistors ... and this is apparently what their quite selective customers want. I use these amp modules and have no complaints, "golden ear" audio wise ... as voltage followers with gain from a tube pre-amp =
...... But I'm not prepred to design a complete "summing" pre-amp with low pass filter of discrete transistors as yet.
4fun: " ... http://www.lcaudio.com/index.php?page=13 ..."
Wow, thanks a bunch. From this online calculator I see the that caps and resistors (C1 & R1 in my drawing) may be way outta whack ... should be more like 45 nF and 22K Ohms for corner freq of ~ 150 Htz. ... No?
juergenk: " ... is it still about subwoofers? The type of amplifier shouldn't matter. ..."
Yes. (in the linked excercise above I only inserted the target low pass freq. and ignored the high pass circuit results = C103 & C104 = 45 nF + the 22K resistors. ... maybe)
And yes, the output amp does not really matter. The one used is simply for illustration as it has a 1.0 uF DC blocking cap on the amp module board and has an input impedence of 33.2K Ohms (from board specs and confirmed on the backside of the cap) ... Of course just about any power amp is possible here and I would hope that the eventual circuit would work with any sub woofer amp that has similar characteristics ... (This is looking more and more like an exercise that has been undertaken many times before.) Purpose = learn and build a single channel sub woofer from both left and right sources =
Wow, thanks a bunch. From this online calculator I see the that caps and resistors (C1 & R1 in my drawing) may be way outta whack ... should be more like 45 nF and 22K Ohms for corner freq of ~ 150 Htz. ... No?
juergenk: " ... is it still about subwoofers? The type of amplifier shouldn't matter. ..."
Yes. (in the linked excercise above I only inserted the target low pass freq. and ignored the high pass circuit results = C103 & C104 = 45 nF + the 22K resistors. ... maybe)
And yes, the output amp does not really matter. The one used is simply for illustration as it has a 1.0 uF DC blocking cap on the amp module board and has an input impedence of 33.2K Ohms (from board specs and confirmed on the backside of the cap) ... Of course just about any power amp is possible here and I would hope that the eventual circuit would work with any sub woofer amp that has similar characteristics ... (This is looking more and more like an exercise that has been undertaken many times before.) Purpose = learn and build a single channel sub woofer from both left and right sources =
Agree 100%.
FastEddy,
There is no electric or psycho acoustic quality that is improved with your circuit compared with standard virtual earth mixing and by using Sallen & Key filters when using todays standard low noise opamps though its possible to make your ever changing trial circuit work only if the right components are used.
b
1(1)
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borjno & 4fun: Your clarifications are really appreciated. And thanks for going to all this trouble.
I see that borjo treated the output amp as a simple load of 1uF capacitor & 33K Ohm resistor = which clarifies my drawing significantly. Are these cap. values closer to the corner freq of 150 Htz.? ... New drawing ...
(Should the test points for the graph generation be at the output of either left or right channel ?? ... or do the op-amps have an effect on the software calculations?)
I see that borjo treated the output amp as a simple load of 1uF capacitor & 33K Ohm resistor = which clarifies my drawing significantly. Are these cap. values closer to the corner freq of 150 Htz.? ... New drawing ...
(Should the test points for the graph generation be at the output of either left or right channel ?? ... or do the op-amps have an effect on the software calculations?)
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