Makes sense. I usually divide the transformer VA by the line voltage as well but have found a small fudge factor is involved and sometimes some upsizing especially if no softstart is used. So 400VA/120V = 3.3 A. So I try 3A. If that blows then 4A. But I would look to make sure there isn’t a short in the circuit I’m building!
I didn’t know that about the neutral fuse value. So in example, probably shoot for 6A.
For identifying the proper fuse locations, I would recommend double checking with a DMM.
Thanks Ben!
Best,
Anand.
I didn’t know that about the neutral fuse value. So in example, probably shoot for 6A.
For identifying the proper fuse locations, I would recommend double checking with a DMM.
Thanks Ben!
Best,
Anand.
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I checked with bulb tester this morning.
When I plug with bulb tester,both LED(pico's mod) are on
But without,no led lights on.
PSU voltage is ok +/-25V.
There are no smoke and every resistors looks working with multimeter.
Checked VGS, Q1 was 0.3V, Q2 was more than 2V so I turned off.
So probably P1,P2 wiper problem?
When I plug with bulb tester,both LED(pico's mod) are on
But without,no led lights on.
PSU voltage is ok +/-25V.
There are no smoke and every resistors looks working with multimeter.
Checked VGS, Q1 was 0.3V, Q2 was more than 2V so I turned off.
So probably P1,P2 wiper problem?
Thank you Anand & Ben Mah, I had what I thought was a pair of fuses for the AC receptacle but was unsure of whether they were appropriate. Both are 5mm X 20mm 250V slow blow with one 2.5A and the other being 10A.
What Ben suggested makes sense and I will use the 10A on the neutral side and the 2.5A on the hot side.
Anand, I will look at suggested page to get myself further acquainted.
Thank you both.
What Ben suggested makes sense and I will use the 10A on the neutral side and the 2.5A on the hot side.
Anand, I will look at suggested page to get myself further acquainted.
Thank you both.
Is it big enough?
First off, apologies if this is the wrong thread. I am going to be jumping into my first DIY amp build very soon and considering the f6. But for the past few weeks I have been a bit anxious on the power output. 25watts, is it big enough? So this is what i have. Dali zensor7 + Dali zensor3 on each side and my listening room is 27m2.
Currently they are powered from a very old Yamaha dsp-ex750se with the pre being my Marantz AV7703. I have a 12" tapped horn and a 10" sealed sub which are both powered from a separate amp.
Now I don't listen to my music mega loud but just enough for it to be "nice" if that makes sense.
So... Is the f6 big enough? Please forgive me if this has been asked a thousand times (I did do a search) I realize its a hard question to answer but hopefully just a rough estimate, I think my Yamaha amp maybe reaches 50% on "loud volume", I refuse to put it louder and don't want it louder. The speakers have a sensitivity of around 90db for the zensor7's.
First off, apologies if this is the wrong thread. I am going to be jumping into my first DIY amp build very soon and considering the f6. But for the past few weeks I have been a bit anxious on the power output. 25watts, is it big enough? So this is what i have. Dali zensor7 + Dali zensor3 on each side and my listening room is 27m2.
Currently they are powered from a very old Yamaha dsp-ex750se with the pre being my Marantz AV7703. I have a 12" tapped horn and a 10" sealed sub which are both powered from a separate amp.
Now I don't listen to my music mega loud but just enough for it to be "nice" if that makes sense.
So... Is the f6 big enough? Please forgive me if this has been asked a thousand times (I did do a search) I realize its a hard question to answer but hopefully just a rough estimate, I think my Yamaha amp maybe reaches 50% on "loud volume", I refuse to put it louder and don't want it louder. The speakers have a sensitivity of around 90db for the zensor7's.
Since you already have a setup that works, perhaps it's worth making this test to put your mind at ease?
A Test. How much Voltage (power) do your speakers need?
I did my tests and on my 88db sensible speakers, I measured that for my 4Ohm ones I need minimum 15Watts, and for my 8Ohm ones I need minimum 9Watts.
You can test yourself (in the second post there is a quick-and-dirty way of transforming the volts you measured into watts, just square the value).
That would perhaps give you a real hint of what 25 Watts will mean in your system?
For what is worth, I think that if they are trully 90db efficient speakers, you are probably good to go!
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I ran my AJ (also similar wattage) on a pair of Overnight Sensations which I think clock in at 83 dB, and they were surprisingly loud. I now use them on a pair of Blumenstein Thrashers (a lot like their current Tritons, which are supposedly 95 dB/w). About 1.5m away, it gets *very, very* loud. HTH
Some power on testing today, power supply is good putting out -23.1vdc and +22.9vdc.
Rigged up a light bulb tester and using a 25W bulb powered up each individual side of the amps and they both seemed ok.
The bulb comes on with the power rush then dims and goes out in about 2-3 seconds.
Then I came to the conclusion that I do not know which is the ".47 ohm source resistor". Studying the schematic produced some possibilities but the only .47 ohm resistors are maybe R1 and R2. I have installed a .56 ohm resistor in both boards R1 position, and a .47 ohm resistor in both boards R2 position.
Assuming that R1 is the "source resistor" and using a meter and adjusting the BIAS pot P2, I eventually achieved .505 vdc.
Then I checked the offset and it was about .5 vdc which is clearly needing adjustment of P1. Power down, turn P1 pot counter-clockwise 10 full turns. Power up, wait for things to stabilize, and the offset has barely moved. I powered down again then turned P1 another 10 turns and powered back up. And the offset is still no better.
And now I am wondering if I haven't maybe got something wrong either in which is the source resistor, or have I installed something, maybe the P1 and/or P2 pots incorrectly?
I installed the pots in all 4 locations with the adjuster screw at the opposite end from the directional arrow. There was no pin 1 showing so perhaps it does not matter. ???
After a number of hours today trying to troubleshoot this I remain uncertain about the source resistor and therefor, everything after that is doubtful.
Looking at the schematic has not helped me much, the source of voltage would appear to be perhaps R5, but that is not a .47 ohm resistor.
So I am less sure now than I was this morning.
Suggestions needed . . . Thank you much.
Rigged up a light bulb tester and using a 25W bulb powered up each individual side of the amps and they both seemed ok.
The bulb comes on with the power rush then dims and goes out in about 2-3 seconds.
Then I came to the conclusion that I do not know which is the ".47 ohm source resistor". Studying the schematic produced some possibilities but the only .47 ohm resistors are maybe R1 and R2. I have installed a .56 ohm resistor in both boards R1 position, and a .47 ohm resistor in both boards R2 position.
Assuming that R1 is the "source resistor" and using a meter and adjusting the BIAS pot P2, I eventually achieved .505 vdc.
Then I checked the offset and it was about .5 vdc which is clearly needing adjustment of P1. Power down, turn P1 pot counter-clockwise 10 full turns. Power up, wait for things to stabilize, and the offset has barely moved. I powered down again then turned P1 another 10 turns and powered back up. And the offset is still no better.
And now I am wondering if I haven't maybe got something wrong either in which is the source resistor, or have I installed something, maybe the P1 and/or P2 pots incorrectly?
I installed the pots in all 4 locations with the adjuster screw at the opposite end from the directional arrow. There was no pin 1 showing so perhaps it does not matter. ???
After a number of hours today trying to troubleshoot this I remain uncertain about the source resistor and therefor, everything after that is doubtful.
Looking at the schematic has not helped me much, the source of voltage would appear to be perhaps R5, but that is not a .47 ohm resistor.
So I am less sure now than I was this morning.
Suggestions needed . . . Thank you much.
R2 is the source resistor across which you measure voltage when setting bias.
Putting the pots in "backwards" would just change the direction you need to turn them for a particular effect, though ideally you want to to start with them with 0 resistance between R10 and the negative rail (for P2) and R9 and ground (for P1). Failing that, at the very least, set them halfway through their entire range to avoid starting at maximum bias.
And you do not need to power down to adjust DC offset, though the usual safety warnings about sticking your hand in a live amplifier do apply.
Putting the pots in "backwards" would just change the direction you need to turn them for a particular effect, though ideally you want to to start with them with 0 resistance between R10 and the negative rail (for P2) and R9 and ground (for P1). Failing that, at the very least, set them halfway through their entire range to avoid starting at maximum bias.
And you do not need to power down to adjust DC offset, though the usual safety warnings about sticking your hand in a live amplifier do apply.
It is the balance between P1 and P2 that affects offset.
You need to be adjusting both of them while monitoring both offset and voltage across R2.
Ensure that the voltage across R2 does not climb too high, while slowly adjusting P1 & P2 to minimise offset.
Adjusting by 10 turns while switched off is very risky, you can easily fry somemthing doing that!
You need to be adjusting both of them while monitoring both offset and voltage across R2.
Ensure that the voltage across R2 does not climb too high, while slowly adjusting P1 & P2 to minimise offset.
Adjusting by 10 turns while switched off is very risky, you can easily fry somemthing doing that!
I can see that it will be a bit of a juggling act, where turning one will affect both results and so I will need to carefully be adjusting both while watching both.
When I engaged in ten turns I felt reasonably confident that no disasters would ensue because results were not moving at all.
I have been involved with other equipment that needed multiple adjustments while watching multiple results to achieve the required balance. I am feeling a wee bit more confident now about several things.
When I engaged in ten turns I felt reasonably confident that no disasters would ensue because results were not moving at all.
I have been involved with other equipment that needed multiple adjustments while watching multiple results to achieve the required balance. I am feeling a wee bit more confident now about several things.
From the 1st page of the thread:
Understand that keeping the dim bulb tester in place, you will never be able to achieve maximum bias and/or correct DC offset. It's really only for initial testing. Also, understand that the changes in both bias and DC offset will happen slowly due to the capacitors ( C1 & C2 ) in the circuit.
Best,
Anand.
Understand that keeping the dim bulb tester in place, you will never be able to achieve maximum bias and/or correct DC offset. It's really only for initial testing. Also, understand that the changes in both bias and DC offset will happen slowly due to the capacitors ( C1 & C2 ) in the circuit.
Best,
Anand.
Thank you RafaPolit & lonepine510.
I have ran my tests which believe it or not seem to measure 0.8volts. I have rounded it up a bit (doubled it).
So 1.6v x 1.6v = 2.56watts. Think i'm safe!!
F6 build will be starting very soon.
Thanks for the tips and advice.
I have ran my tests which believe it or not seem to measure 0.8volts. I have rounded it up a bit (doubled it).
So 1.6v x 1.6v = 2.56watts. Think i'm safe!!
F6 build will be starting very soon.
Thanks for the tips and advice.
I did these tests today and got some unexpected results, so I am again unsure about what I should do next.
I did set the BIAS pot P2 by measuring and adjusting for 0 resistance between R10 and the negative rail. I achieved this on both boards.
I attempted to set the OFFSET pot P1 by measuring and adjusting for 0 resistance between R9 and Ground.
I did NOT achieve this but did manage to obtain 14 ohms of resistance from both boards.
Regarding the .47 ohm resistor R2, I get very unexpected results suggesting a bit of mixup here.
I think that: R1 could be a .47 ohm resistor because I get more expected results when checking R1.
The build guide suggests that R1 can be a .47ohm or .56ohm resistor, I have used a .56ohm resistor. ???
For R1 I see .778 vdc on the left board, and -.774 vdc on the right board.
For R2 In see -20.1 vdc on both boards, clearly not what I would expect.
I think that obtaining the low resistance readings is setting the P2 pot at the minimum state of it's range so I am unsure how I would lower the .778vdc to .500vdc, except that maybe a few changes maybe needed?
So I am still messed up about this and will now ponder my next move.
For what is worth, measuring bellow 1ohm requires very fine equipment. So I wouldn't be too worried that your .56 reads .47 in the multimeter.
On the other hand... do you have access to a second multimeter? I don't think you can do the pot adjustment by adjusting one, checking only one value, moving the other, checking the other value... this is more like adjusting balls on a pivot in order to get them leveled. You cannot adjust one ball, then start moving the other and expect the system to be balanced. You have to grab both and move them a bit at a time and checking the system is still balanced.
On the other hand... do you have access to a second multimeter? I don't think you can do the pot adjustment by adjusting one, checking only one value, moving the other, checking the other value... this is more like adjusting balls on a pivot in order to get them leveled. You cannot adjust one ball, then start moving the other and expect the system to be balanced. You have to grab both and move them a bit at a time and checking the system is still balanced.
I do have other meters and even have them involved with this build. Currently two meters, one at each speaker port. And a third, my best/newest meter with the best probes being used to measure results from BIAS adjustments.
I understand that it's a balancing act between P1 & P2. My problem is not seeing values I am anticipating, and not seeing movement when there should be some.
I think what I may need to be doing is adjusting both, more-or-less, at the same time, then wait a bit to check the results then adjust again.
I will keep at it,
I understand that it's a balancing act between P1 & P2. My problem is not seeing values I am anticipating, and not seeing movement when there should be some.
I think what I may need to be doing is adjusting both, more-or-less, at the same time, then wait a bit to check the results then adjust again.
I will keep at it,
AudGuy,
Are Q1 and Q2 MOSFETS warming up? Because if you are getting -20V ish across R2, that's pretty close to the rail voltage so that brings up questions about whether Q2 is working/conducting. You may have a cold solder joint somewhere too.
Did you make sure that Q3 and Q4 are soldered in the right spots? They are in different locations on each board so it is easy to flip a K170 for a J74 by mistake.
Please post detailed pics of your build, along with where your test leads are for the measurements of the bias and offset.
Rafapolit is right that measuring resistors below 1 ohm requires more expensive equipment, specifically bench LCR meters. I have one which I use to make these measurements in addition to subtracting the resistance in the wire leads themselves. A Kelvin 4 wire testing setup would be best. That being said, you don't have to be that precise for these Class A amp builds. So whether you have a 0.47 ohm resistor or 0.56 ohm resistor makes a small difference (about 15% or so) during the setup phase. The 0.56 ohm resistor was chosen by Nelson Pass to adjust the phase of the second harmonic distortion spectra. This was done for an aural benefit.
Best,
Anand.
Are Q1 and Q2 MOSFETS warming up? Because if you are getting -20V ish across R2, that's pretty close to the rail voltage so that brings up questions about whether Q2 is working/conducting. You may have a cold solder joint somewhere too.
Did you make sure that Q3 and Q4 are soldered in the right spots? They are in different locations on each board so it is easy to flip a K170 for a J74 by mistake.
Please post detailed pics of your build, along with where your test leads are for the measurements of the bias and offset.
Rafapolit is right that measuring resistors below 1 ohm requires more expensive equipment, specifically bench LCR meters. I have one which I use to make these measurements in addition to subtracting the resistance in the wire leads themselves. A Kelvin 4 wire testing setup would be best. That being said, you don't have to be that precise for these Class A amp builds. So whether you have a 0.47 ohm resistor or 0.56 ohm resistor makes a small difference (about 15% or so) during the setup phase. The 0.56 ohm resistor was chosen by Nelson Pass to adjust the phase of the second harmonic distortion spectra. This was done for an aural benefit.
Best,
Anand.
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AudGuy,
Please verify all part values and can you please post some well lit and in focus photos of your build?
Do you see the correct rail voltages on the pcbs? What parts are you using for Z1 and Z2, R7 and R8? What voltages do you measure across Z1 and Z2.
What did you mean when you said you saw certain voltages at R1 and R2? Did you measure across R1 /R2? (20V across R2 should cause R2 to fail.)
Please verify all part values and can you please post some well lit and in focus photos of your build?
Do you see the correct rail voltages on the pcbs? What parts are you using for Z1 and Z2, R7 and R8? What voltages do you measure across Z1 and Z2.
What did you mean when you said you saw certain voltages at R1 and R2? Did you measure across R1 /R2? (20V across R2 should cause R2 to fail.)
Poseidonsvoice,
Are Q1 & Q2 warming up . . . well, I would say that, NO, they are not. I have not finger detected or measured anything above ambient so far.
I was careful during construction and checked everything closely as I went along, but there could be a cold joint. I will look again.
Are Q3 & Q4 in the right spots . . . of this I am somewhat unsure. The BOM called for Q3-2SK170BL or LSK170B and Q4-2SJ74BL or LSJ74B however, what I received from the DIY store was 4 X LSK170F. I confirmed that all 4 devices were LSK170F and because of where I got them, assumed that these were suitable. This may of been a mistake.
On my behalf, I think this all started with me being unsure exactly what the "source resistor" would be. Studying the schematic did not answer my question. At this point, it was suggested as being R2 but my measurements tended to point at R1 (for whatever reason) so I am confused.
I will post pictures and details of how I am configured later this evening.
thankyou Anand
Are Q1 & Q2 warming up . . . well, I would say that, NO, they are not. I have not finger detected or measured anything above ambient so far.
I was careful during construction and checked everything closely as I went along, but there could be a cold joint. I will look again.
Are Q3 & Q4 in the right spots . . . of this I am somewhat unsure. The BOM called for Q3-2SK170BL or LSK170B and Q4-2SJ74BL or LSJ74B however, what I received from the DIY store was 4 X LSK170F. I confirmed that all 4 devices were LSK170F and because of where I got them, assumed that these were suitable. This may of been a mistake.
On my behalf, I think this all started with me being unsure exactly what the "source resistor" would be. Studying the schematic did not answer my question. At this point, it was suggested as being R2 but my measurements tended to point at R1 (for whatever reason) so I am confused.
I will post pictures and details of how I am configured later this evening.
thankyou Anand
Dennis Hui,
Pictures will be posted a little later this evening.
Z1 & Z2 were IN4733 5.1v devices. Or at least I have ticked them off on my BOM indicating as there being 4 of them. I will confirm from the packing slip.
R7 & R8 were 2026J/1002F devices according to notes I made on my BOM.
I must admit that the term "measure across" is for me, a little bit unsure making.
Does this mean to measure from both end of the measured device, or to measure between one end of the device and ground? I measured between the end of the R1 resistor and ground and see .776vdc on the left and -.774vdc on the right. R2 on both boards measure as about -20.1vdc.
I was able to achieve 0 or near 0 resistance between R10 & Neg.Rail for BIAS and 14 ohms for R9 to ground for OFFSET.
Thanks Dennis,
Pictures will be posted a little later this evening.
Z1 & Z2 were IN4733 5.1v devices. Or at least I have ticked them off on my BOM indicating as there being 4 of them. I will confirm from the packing slip.
R7 & R8 were 2026J/1002F devices according to notes I made on my BOM.
I must admit that the term "measure across" is for me, a little bit unsure making.
Does this mean to measure from both end of the measured device, or to measure between one end of the device and ground? I measured between the end of the R1 resistor and ground and see .776vdc on the left and -.774vdc on the right. R2 on both boards measure as about -20.1vdc.
I was able to achieve 0 or near 0 resistance between R10 & Neg.Rail for BIAS and 14 ohms for R9 to ground for OFFSET.
Thanks Dennis,