No more 60 Hz hum in a PL2000 preamp.
- Thread starter George S.
- Start date
The popping of the preamp into the amp is a bona fide signal going from the preamp into the amp which had been powered up prior (recommend reversing that power up order since the amp has a DCP or leave your preamp on all the time). It is not power switch noise at all. It is due to the unsettled nature of the op amp behavior as the power supplies increase from zero to +/-15V. The op amps will not regulate their output until there is at least +/- 5VDC if you are using RC4136 op amps or +/- 2.5VDC if you are using OPA2134 op amps. That means that during that region below that minimum voltage the op amp is free to misbehave all it likes. Simple to understand.
I have been off the grid for a couple days with Christmas festivities that required my full attention to enjoy with the grandkids. I see that a lot of chatter has occurred.
It is pretty simple guys.
A 10uF blocking cap has an impedance of 1592 ohms at 10Hz, 159.2 ohms at 100Hz, 15.92 ohms at 1000Hz, 1.592 ohms at 10KHz and so on.
If you have 2 2.2uF caps in series to act as a non-polar cap, you really have a 1.1uF non-polar blocking cap.
A 1.1uF blocking cap has an impedance of 14468 ohms at 10Hz, 1446.8 ohms at 100Hz, 144.68 ohms at 1000Hz, 14.468 ohms at 10KHz and so on.
If you are happy with your preamp having an output impedance of >14K ohms at 10Hz then party on. I would not be because it is compromising all that low frequency output.
Bigger is definitely better. Why don't all manufacturers use whomping big caps? Because they cheap out. Big film caps are expensive and take up a lot of room.
Hope this explanation helps. Merry Christmas.
It is pretty simple guys.
A 10uF blocking cap has an impedance of 1592 ohms at 10Hz, 159.2 ohms at 100Hz, 15.92 ohms at 1000Hz, 1.592 ohms at 10KHz and so on.
If you have 2 2.2uF caps in series to act as a non-polar cap, you really have a 1.1uF non-polar blocking cap.
A 1.1uF blocking cap has an impedance of 14468 ohms at 10Hz, 1446.8 ohms at 100Hz, 144.68 ohms at 1000Hz, 14.468 ohms at 10KHz and so on.
If you are happy with your preamp having an output impedance of >14K ohms at 10Hz then party on. I would not be because it is compromising all that low frequency output.
Bigger is definitely better. Why don't all manufacturers use whomping big caps? Because they cheap out. Big film caps are expensive and take up a lot of room.
Hope this explanation helps. Merry Christmas.
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I still think using a power conditioner & sequencer, with amplifiers turned on last/shut off first with delay prior to turning off other peripherals, is the way to go. I have been very happy with this used Panamax M4315-PRO off ebay for < $100 shipped&taxes. Outlets 7&8 are used for the amplifier(s) here.
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Question below all for not. A non polar nichicon se series with 470uf measures 484if so replacing a 470uf polar cap will not change anything. Answered my own question. Pretty good Yeh!. And yes I did measure two polar caps with negs bonded and they measured 50% of value.
Final question is if I replace a directional cap in the sound path with a non polar of equal rating I in fact have reduce it overal capacitance by
50% and should at least double it when doing this change right? I have always thought electrolytic non polar caps are better in the sound path than regular electrolytic caps. im Going to measure a non polar and compare against to back to back of same rating
Final question is if I replace a directional cap in the sound path with a non polar of equal rating I in fact have reduce it overal capacitance by
50% and should at least double it when doing this change right? I have always thought electrolytic non polar caps are better in the sound path than regular electrolytic caps. im Going to measure a non polar and compare against to back to back of same rating
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Glenn, why are you using electrolytics. Thought film was preferred.
for electrolytic capacitors, capacitance and ESR both exhibit a strong frequency dependency [1], while film capacitors show almost constant capacitance and ESR values across the technically interesting frequency range from 100 Hz ~ 200 kHz
for electrolytic capacitors, capacitance and ESR both exhibit a strong frequency dependency [1], while film capacitors show almost constant capacitance and ESR values across the technically interesting frequency range from 100 Hz ~ 200 kHz
A non-polar electrolytic cap is just 2 polar caps packaged back to back in the same case.
A non-polar electrolytic capacitor is never superior to a non-polar film cap of equal value in any audio path application except for size and cost. Smaller and lower cost...
A non-polar electrolytic will perform similarly for low frequencies to the non-polar film cap but will suffer at high frequencies when compared to the film cap equivalent.
A non-polar electrolytic capacitor is never superior to a non-polar film cap of equal value in any audio path application except for size and cost. Smaller and lower cost...
A non-polar electrolytic will perform similarly for low frequencies to the non-polar film cap but will suffer at high frequencies when compared to the film cap equivalent.
George that is what is in the Carvers. I guess this opens up what to do about it as the pin out is only 3.5 mm or 5 mm adding longer legs to caps is not good in sound path. As you can see there are four caps in each sound path of concern 1 each phono mc and mm outputs. Two more after the main amplifier ic and the last at the main outputs. All are electrolytic of which I change to non polar of same value. From what Joe has said these need to all be film caps. I’ll look for the smallest package for 22uf in film but don’t have my hopes up. These are circled in red
If they are 22 uF you'll never find a film with a small lead spacing like that. They're just too big. But the crimped lead caps allow some easy adjustment. This is a Panasonic ECW 4.75 uF 250 V with crimped leads. Would have used a smaller voltage and physically smaller version if I could have found it stocked. About 18 mm lead spacing on this one, it replaced a axial, guess your dealing with radials. Bummer, use audio grade electrolytics, not much choice.
