The ohm-meter measurements are:
16swg 500g 0r24
1.8mm 1000g 0r17
2.12mm 500g 0r07
The mega 328 DCR results are codswallop.
However, I did measure some other inductors last night and they were within 15% of my results using resistor+inductor with sig gen, frequency counter & Dmm.
16swg 500g 0r24
1.8mm 1000g 0r17
2.12mm 500g 0r07
The mega 328 DCR results are codswallop.
However, I did measure some other inductors last night and they were within 15% of my results using resistor+inductor with sig gen, frequency counter & Dmm.
That's more like it. Thanks. Not sure when I will get round to getting the inductors sorted, in the next few weeks. Ill post results then.
Your inductors really should have a laminated or gapped cut-core to keep the DCR down and the inductance up . Do you just need a single choke of a few mH ? I may have a few orphan chokes suitable , I can only use in pairs
316a
316a
It was my original mistaken thinking I needed an AC choke. What is actually needed is 4 DC filters, large enough not to saturate from the DC current. The Hammond 159zl seems like it would be ideal, I have seen others recommend Erse inductors, and Jantzen air core.
But at $100-200 for a set of 4 for these options, I can wind my own for around $50 in copper wire. The down side being it will be larger, but my chassis has room, and slightly higher DCR which in this case, shouldn't be an issue other than a little voltage drop.
But at $100-200 for a set of 4 for these options, I can wind my own for around $50 in copper wire. The down side being it will be larger, but my chassis has room, and slightly higher DCR which in this case, shouldn't be an issue other than a little voltage drop.
You choose your DCR by selecting the copper wire diameter appropriately.
An air core inductor does not need to be higher DCR.
An air core inductor does not need to be higher DCR.
Many years ago during the Zen V1-4, I had to much hummmm. As I recall it was something like 40mV. Mostly due to skimping on Parts quality and $$$ values. I stepped up to something like 39mf-39mf big blue computer grade caps, .1ohm, and another bank of 39mf-39mf. That got the majority of the hum but, I needed it quieter. It might have been 15mV if I remember. I tried a 2.2mH air core 14 or 16Ga L in place of the R and was surprised to find very little improvement? I tried a .25ohm in place of the L and the hum dropped down to maybe 5mV or less. But, it started to eat up rail voltage a few volts? I looked for a real inductor and found a Hammond 195M10 Hammond Mfg. - Chokes & Reactors - Heavy Current (195 - 196 Series) used and reasonable on Ebay, I do not remember what that number was but, I had to spend the same amount to ship 10lbs(22kg), and I think it was still very reasonable compared to mfg listed $. With the 39,000uF||39,000uF>20mH>39,000uF||39,000uF, I could not measure the ripple on my scope!
Later I built a ZenV4 with the reg and I don't believe it was better. I liked the sound of the first one. I swapped supplies and the supply made that much difference to either amp!
The 20mH 10A L is a little over the edge but the results were great! I still have that supply even though other people are enjoying those Zen amps (with the cap mult reg).
It pays off to experiment with your components and operating conditions in the power supply. Your input signal is not the only source in your system. The power supply is one also. 😀
Later I built a ZenV4 with the reg and I don't believe it was better. I liked the sound of the first one. I swapped supplies and the supply made that much difference to either amp!
The 20mH 10A L is a little over the edge but the results were great! I still have that supply even though other people are enjoying those Zen amps (with the cap mult reg).
It pays off to experiment with your components and operating conditions in the power supply. Your input signal is not the only source in your system. The power supply is one also. 😀
Indeed, which is why I had settled on around 14awg as a good balance of power handling, size, cost and DCR.
This is my first amplifier build. Having spent 5 years living in Florida and now back in the UK, I can tell you the availability of such thing is much less. There is one of those chokes you mention on ebay in the USA for $30 or so, if I could just get 4 of those for that price I probably would.
I have one amplifier up and running with CRC, 45000uf-0.22ohm-45000uf. Using the balanced input I have no hum on my 99db sensitivity bass driver, and a little hiss on my 105db or so horn. I have no way of measuring it as I don't have a scope, but I'm happy with the current performance, I will be interesting to compare when I get round to adding the inductors.
0.023v AC on the negative rail.
0.030v AC on the positive rail.
No reading on the speaker terminals in AC, 0.027v in offset DC.
0.030v AC on the positive rail.
No reading on the speaker terminals in AC, 0.027v in offset DC.
This looks like it confirms your DMM set to AC voltage does not read the DC voltage bias on the AC signal you want to measure.
I have 4 DMM from ultra cheap (<£3) to a Bench type and all 4 ignore the DC voltage when measuring AC.
The AC ripple on your supply is very approximately 3 times the AC reading you have measured.
i.e. you measured 0.023Vac = 23mVac and that is ~ 70mVpp ripple.
Try to buy a DMM that has an AC scale that reads 199.9mVac. They do not need to be expensive. My <£3 and my £9 versions both have these more sensitive scales.
My meter has the 200mV setting, which is what I used. It read 23 and 30 respectively. This was on the 34v rails, I had assumed it would ignore any DC.
I'm not sure I have anyway to improve this beyond adding the inductors, or if it even needs improvement, all of this is rather new to me. At least I have a baseline measurement to compare with future changes.
I plan to get a dummy load and at least use my pc and a software scope/rightmark to at least check there is nothing terribly wrong.
For ClassAB and/or other low current amps (pre-amps) the supply ripple after the smoothing is usually low, expect 5mVpp to 20mVpp.
When a ClassA amplifier is connected to a ClassAB type PSU the high current increases the ripple to enormous levels.
Expect 100mVpp to 500mVpp.
One must use a ClassA style PSU.
This is designed specifically to reduce mains ripple while very high currents are being passed to the amplifier.
That is why you see rC type PSU on ClassAB, but this changes to rCCCCC or rCRCC or rCRCRC. These are attempts to attenuate the ripple. The little r is the resistance of the secondary and wiring upto the PSU.
Better is rCL+rC or rCL+rCL+rC The next little r is the DCR of the inductor.
More section of LC or RC attenuate the mains ripple a bit more.
amplifiers with a poor or very poor PSSR need very low ripple supplies.
You see this in Valve/Tube regularly. Simple single-ended SS amplifiers also benefit from well filtered PSUs if PSSR is poor.
If you have 0.0mVac of hum at the output of your amplifier then you may not need any more filtering.
This will depend on how sensitive your speakers are. 0.0mVac on a DMM measuring 199.9mVac actually means <0.05mVac. It could be as high as 0.049mVac
That level of hum fed into a "normal" speaker with sensitivity of 82dB to 89dB will sound "silent".
Into your 99dB bass speaker, you would need hum levels of ~ 10dB less than 0.049mVac ie ~<0.015mVac.
Many Members try to measure speaker hum with their ears. They describe hum levels upto 1mVac as "completely silent".
If they would just use a DMM set to 199.9mVac, they could be much more informative and more knowledgeable.
When a ClassA amplifier is connected to a ClassAB type PSU the high current increases the ripple to enormous levels.
Expect 100mVpp to 500mVpp.
One must use a ClassA style PSU.
This is designed specifically to reduce mains ripple while very high currents are being passed to the amplifier.
That is why you see rC type PSU on ClassAB, but this changes to rCCCCC or rCRCC or rCRCRC. These are attempts to attenuate the ripple. The little r is the resistance of the secondary and wiring upto the PSU.
Better is rCL+rC or rCL+rCL+rC The next little r is the DCR of the inductor.
More section of LC or RC attenuate the mains ripple a bit more.
amplifiers with a poor or very poor PSSR need very low ripple supplies.
You see this in Valve/Tube regularly. Simple single-ended SS amplifiers also benefit from well filtered PSUs if PSSR is poor.
If you have 0.0mVac of hum at the output of your amplifier then you may not need any more filtering.
This will depend on how sensitive your speakers are. 0.0mVac on a DMM measuring 199.9mVac actually means <0.05mVac. It could be as high as 0.049mVac
That level of hum fed into a "normal" speaker with sensitivity of 82dB to 89dB will sound "silent".
Into your 99dB bass speaker, you would need hum levels of ~ 10dB less than 0.049mVac ie ~<0.015mVac.
Many Members try to measure speaker hum with their ears. They describe hum levels upto 1mVac as "completely silent".
If they would just use a DMM set to 199.9mVac, they could be much more informative and more knowledgeable.
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Thanks for that, I was mostly familiar with the power supplies in class ab, and small scale regulated supplies, but these class A amplifiers are new to me.
I am limited by the tools I have available, of course trying to judge with the ear is fairly useless. The amps are to drive my horns in a 3 way active setup, the horns are around 105db efficient, I can only hear a low level of hiss. I am happy enough with the current performance.
I do have access to a decent fluke meter, I might borrow it to compare.
I'm going to need a scope, then I can measure things to my hearts desire.
A scope cannot measure very low voltages.
1mV/div is about the most sensitive without enormous expense.
I have used 2mV/div 100MHz, 5mV/div 50MHz and 20mV/div 20MHz (it was a dual beam, dual channel (4 traces) valve model. Beautiful build, but it expired on one beam).
Each increase in sensitivity and bandwidth was a nice feature, at a cost.
For a 105dB speaker you do not need much power and you should strive for an ultra low noise target.
for 115dB @ 1m you need only 10W
But noise needs to be at least 80dB below your average listening level. That will give you a very low target.
1mV/div is about the most sensitive without enormous expense.
I have used 2mV/div 100MHz, 5mV/div 50MHz and 20mV/div 20MHz (it was a dual beam, dual channel (4 traces) valve model. Beautiful build, but it expired on one beam).
Each increase in sensitivity and bandwidth was a nice feature, at a cost.
For a 105dB speaker you do not need much power and you should strive for an ultra low noise target.
for 115dB @ 1m you need only 10W
But noise needs to be at least 80dB below your average listening level. That will give you a very low target.
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Well If I cant measure it on a scope, I will probably have to call it adequate.
Well, such is the down side of high efficiency speakers. A simple first order filter at say 600hz wont harm, and would help reduce any 50-100hz hum.
I listen on average 75-80dbc, of course of that 1300hz and up is a small portion. I don't think 0db is a realistic target given the average background noise of my listening room is 40-50db. Either way, I will experiment for the sake of it, no harm in getting it as low as I can.
They make less noise than the amplifier they have replaced, so it is already an improvement.
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