What sort of frequencies are you considering the "bottom end"? I posted some simulations here that show a moderate drop in output impedance above 100hz when 22mF is added to the output of the Gtose CapMx. Based on the sims, I'm going to have equal capacitance before and after a CapMx in my PSU. Could this contribute to the effect you observe/hear?
Brother, remember you are talking to a board stuffer, and at this point a stuffer with a couple of Irish whiskeys in him.
I barely know CFP= what.. Complimentary Feedback Pair? Are you talking about where C21 and C22 are now? Feel free to explain to me like I'm a 8yr old.
Preferably with pictures hahah.
Yes CFP = Complementary Feedback Pair
The easiest way to add the extra caps would be to use screw terminal can types connected to the extra V+, GND and V- spade lugs on the output of the SLB boards. Or you could use snap in terminal caps wired directly to the SLB boards. Leave the 220 uF caps at C21 and C22 in place. The big caps end up in parallel with these.
The easiest way to add the extra caps would be to use screw terminal can types connected to the extra V+, GND and V- spade lugs on the output of the SLB boards. Or you could use snap in terminal caps wired directly to the SLB boards. Leave the 220 uF caps at C21 and C22 in place. The big caps end up in parallel with these.
Yes CFP = Complementary Feedback Pair
The easiest way to add the extra caps would be to use screw terminal can types connected to the extra V+, GND and V- spade lugs on the output of the SLB boards. Or you could use snap in terminal caps wired directly to the SLB boards. Leave the 220 uF caps at C21 and C22 in place. The big caps end up in parallel with these.
Okay, do you have a preference in caps?
@TungstenAudio / Thompsontechs and others -
I've read with interest about the use of "Motor Run" caps etc. Similarly, I'm a board stuffer trying to learn a bit more about what I've been building.
Are caps in this application similar? I have similar speakers to JT's, so we may be after some of the same characteristics. Is the basic idea to have a bit more instantly available oooomph in layperson's terms? I've seen the sizes range from what TA recommends on up to some physically massive parts. Different FW amps seem to perform very differently in terms of how I perceive the bass. If it goes back to the PSU - I'd welcome trying some changes.
JT - I can't remember, did you build the Austin boards? FWIW, they had (to my ears) a pretty nifty effect on the spatial presentation of the music.
I've read with interest about the use of "Motor Run" caps etc. Similarly, I'm a board stuffer trying to learn a bit more about what I've been building.
Are caps in this application similar? I have similar speakers to JT's, so we may be after some of the same characteristics. Is the basic idea to have a bit more instantly available oooomph in layperson's terms? I've seen the sizes range from what TA recommends on up to some physically massive parts. Different FW amps seem to perform very differently in terms of how I perceive the bass. If it goes back to the PSU - I'd welcome trying some changes.
JT - I can't remember, did you build the Austin boards? FWIW, they had (to my ears) a pretty nifty effect on the spatial presentation of the music.
MH,
I just built the Pass version of it.
I understand what TA is saying, I don't know the numbers, but do understand. A good analogy might be when you using air tools. If you have a small tank the motor compressor is always fighting to keep up and losing. If I have a 100 gallon tank, I can use the tool harder longer before the compressor ever kicks in. Most of the time, the load is reduced or gone by the time the compressor kicks on and it can top off under a smaller load.
I am also wondering if the AN might benefit from this as well. I have the same supply in that as well. I'm going to give this a listen and decide if it's worth another $60.
I just built the Pass version of it.
I understand what TA is saying, I don't know the numbers, but do understand. A good analogy might be when you using air tools. If you have a small tank the motor compressor is always fighting to keep up and losing. If I have a 100 gallon tank, I can use the tool harder longer before the compressor ever kicks in. Most of the time, the load is reduced or gone by the time the compressor kicks on and it can top off under a smaller load.
I am also wondering if the AN might benefit from this as well. I have the same supply in that as well. I'm going to give this a listen and decide if it's worth another $60.
That's a very good question, class A is running wide open at all times, but I would submit that wide open with and without load are a different animal especially with regard to impedance's. Also with mains voltage fluctuations to be considered as well.
Anyway, thanks for making me think, I'm curious what some of the others who have more knowledge than I, have to say.
I did a lot of reading about this question. This article by Rod Elliott is helpful: Class-A Amplifiers explained
But also
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spice test
Here's a quick test with LTSpice I ran with a BA-2 output stage, which should correlate to the M2. "Ampl" is the input to the OS in volts, and the waveform is the current drawn from the positive rail. Looking at the waveform through the source resistors, it remains in class A (the FETs pass a clean sine wave without flattening).
Nelson's comment makes sense - in a balanced amplifier, the out-of-phase variations would cancel, presenting a relatively constant load.
EDIT: Balanced sim added just for fun. "Ampl" is input to the front end this time. The current through the positive rail has much less variation.
Here's a quick test with LTSpice I ran with a BA-2 output stage, which should correlate to the M2. "Ampl" is the input to the OS in volts, and the waveform is the current drawn from the positive rail. Looking at the waveform through the source resistors, it remains in class A (the FETs pass a clean sine wave without flattening).
Nelson's comment makes sense - in a balanced amplifier, the out-of-phase variations would cancel, presenting a relatively constant load.
EDIT: Balanced sim added just for fun. "Ampl" is input to the front end this time. The current through the positive rail has much less variation.
Attachments
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