Hi Jens & Terry,
the impedance of 470uF at 60 Hz will be too high for a DC blocker. You are looking for a peak voltage drop after start up of below 1volt. This will depend on the current draw of your transformer when the amp is working as normal (hard or gentle depending on your preference). Most of the start up current passes through the parallel diodes and as the start up peak current drops, the diodes switch off.
At a guess I think you will probably need about 2m2F to 10mF back to back.
Do some calcs or supply info & I will post the calcs & answers on the thread.
the impedance of 470uF at 60 Hz will be too high for a DC blocker. You are looking for a peak voltage drop after start up of below 1volt. This will depend on the current draw of your transformer when the amp is working as normal (hard or gentle depending on your preference). Most of the start up current passes through the parallel diodes and as the start up peak current drops, the diodes switch off.
At a guess I think you will probably need about 2m2F to 10mF back to back.
Do some calcs or supply info & I will post the calcs & answers on the thread.
Upupa Epops said:
Hi Upupa,
I probably shouldn’t have posted this here because the Leach doesn't do it. It is my Krells and AlephX that seem to have the problem. If I have any two of those on at the same time I get a noticeable buzzing sound.
You say DC on the Mains but how would I go about fixing that? How would I check for it?
I used a single CL-60 Thermistor on the mains in each of the amps for a soft start. Could that have anything to do with it? It only seems to be with the Class A amps. The Leach and the P101 don't do it.
Thanks, Terry
Can you make a little drawing for that so I get it right?
Thanks, Terry
Hi Bremen,
Thanks for the links. So, can I just use the first portion of the circuit, D1-4 and C1 & C2? Probably good for the amp anyway huh?
Blessings, Terry
Thanks for the links. So, can I just use the first portion of the circuit, D1-4 and C1 & C2? Probably good for the amp anyway huh?
Blessings, Terry
Hi Terry & Jens,
I just found feb 2004 post#61 by Jens
which is correct?
I just found feb 2004 post#61 by Jens
there is a factor of ten difference.
which is correct?
Hi Jens,
can you please confirm that this is relating to C7 and C12, should they be 470uF or 4700uF?
Do you guys think my 52 0 52 V transformer is too high for this amp?
Im expecting 72V rails. What I was thinking was putting some CRC in and having the R at about 5 Ohm so when its pulling 2 amps I get a 10Volt drop across the resistor. Is this flawed?
seeya ab
BTW thanks for all your effort Jens. Great work.
can you please confirm that this is relating to C7 and C12, should they be 470uF or 4700uF?
Do you guys think my 52 0 52 V transformer is too high for this amp?
Im expecting 72V rails. What I was thinking was putting some CRC in and having the R at about 5 Ohm so when its pulling 2 amps I get a 10Volt drop across the resistor. Is this flawed?
seeya ab
BTW thanks for all your effort Jens. Great work.
Luke said:
Luke,
No we were talking about DC on the mains and how to get rid of it.
72V rails is a bit high IMO, and even more so if you plan to use speakers with lower impedance than 8 Ohm.
For 8Ohm 68V rails is the maximum IMO (depending on X-over type and impedance curve)
For 4 Ohm I would not go higher than 60V rails
A lot will depend on your bias current and heat sink as temperature will be a major factor to consider.
I hope this helps
\Jens
With some changes the basic Leach can do anything.
I have one that has been running on ±80V into 1 ohm for the last 15 years. It has 10 pairs of MJ15024/25 for outputs, and another pair as drivers.
The Crown VZ5000 output stage is a triple EF like the Leach, and bridged. It uses 4 pair of MJ15024/25 per half of the bridge(8 pair per channel)with A1302/C3281 as drivers, and delivers 2.5KW into 2 ohms from about ±83V. The two channels may then be bridged again to deliver 5KW into 4 ohms.
The devil is in the details(so to speak). The easiest thing to do is stay within ±40V~±60V or so.
I have one that has been running on ±80V into 1 ohm for the last 15 years. It has 10 pairs of MJ15024/25 for outputs, and another pair as drivers.
The Crown VZ5000 output stage is a triple EF like the Leach, and bridged. It uses 4 pair of MJ15024/25 per half of the bridge(8 pair per channel)with A1302/C3281 as drivers, and delivers 2.5KW into 2 ohms from about ±83V. The two channels may then be bridged again to deliver 5KW into 4 ohms.
The devil is in the details(so to speak). The easiest thing to do is stay within ±40V~±60V or so.
I think Luke was talking about the 6 transistor PCB - Luke?
The rails that I mentioned are chosen so that the protection circuit only is needed for short circuit protection at never is used under normal load conditions.
I have analyzed the output as per Self and Slone and the numbers are adhering from this analysis so I have not just posted some standard numbers….. The analysis is on my website but is not yet done, as I have a lot going on in my life at the moment.
I'm sorry if this was unclear.
\Jens
The rails that I mentioned are chosen so that the protection circuit only is needed for short circuit protection at never is used under normal load conditions.
I have analyzed the output as per Self and Slone and the numbers are adhering from this analysis so I have not just posted some standard numbers….. The analysis is on my website but is not yet done, as I have a lot going on in my life at the moment.
I'm sorry if this was unclear.
\Jens
hi Jens,
yes I was talking about the 6 transistor version.
I have an old amplifier chassis I was going to put it in. It has power supply in tact and was just going to add heatsinks and boards. However this is seeming harder all the time. The sinks I am using are very small and transformer too big. Im thinking its not ideal and may have to try something different.
I have another transformer thats 500va 40 0 40 which is perfect. But I will probably need to make or buy a chassis for it.
For now I will have a rethink.
yes I was talking about the 6 transistor version.
I have an old amplifier chassis I was going to put it in. It has power supply in tact and was just going to add heatsinks and boards. However this is seeming harder all the time. The sinks I am using are very small and transformer too big. Im thinking its not ideal and may have to try something different.
I have another transformer thats 500va 40 0 40 which is perfect. But I will probably need to make or buy a chassis for it.
For now I will have a rethink.
Hi,
you are right, 500VA 40Vac+40Vac is perfect for a stereo 8ohm amplifier.
If you intend using 4ohm speakers then spend a bit of time deciding how to beef up the PSU to cope with domestic level music into bass loads. Maybe a small adjustment to capacitors?
you are right, 500VA 40Vac+40Vac is perfect for a stereo 8ohm amplifier.
If you intend using 4ohm speakers then spend a bit of time deciding how to beef up the PSU to cope with domestic level music into bass loads. Maybe a small adjustment to capacitors?
I am also going to retrofit an old amp chassis with a pair of these. I will be running the front end at 63V and the outputs at 58.4V (existing config). The trafo is 650VA. Shoudl be a perfect match.
Today I finally had som time to do some DIY stuff....
I drilled 2 heat sinks and cut threads in all holes, now I just need som screws...... too bad the shops are closed untill monday 🙂
Anyway here is a pic of the 10 transistor version of my project sitting on heatsinks from Conrad
\Jens
I drilled 2 heat sinks and cut threads in all holes, now I just need som screws...... too bad the shops are closed untill monday 🙂
Anyway here is a pic of the 10 transistor version of my project sitting on heatsinks from Conrad
\Jens
Attachments
BrianDonegan said:
Hi Brian,
Yes that would work....sorry for the delay.
Tony said:
This is the 30 cm wide version called MF30-151.5.
It is cheaper for me to buy heatsinks in Australia and import it to Denmark compared to buying heatsinks from a local vendor.
\Jens
Hi Jens,
The pictures look great. Just how I am laying out my amp. One question though. What value are your filter caps in 6 transistor version? and what brand make etc are they?
They look very nice and compact for their value. I wouldn't mind getting hold of some of them myself. It seems very hard to locate correct value to place on board down here in New Zealand.
Cheers
Ian
The pictures look great. Just how I am laying out my amp. One question though. What value are your filter caps in 6 transistor version? and what brand make etc are they?
They look very nice and compact for their value. I wouldn't mind getting hold of some of them myself. It seems very hard to locate correct value to place on board down here in New Zealand.
Cheers
Ian
Heatsinks from Conrad
I had a look at their site and was very impressed - nice looking parts and much cheaper than anything I could find in England.
I wonder if anyone in the UK/EU fancies a group buy, even if we don't meet the price-break (15% off 10 pieces of the same part) we could save on shipping.
JensRasmussen said:
I had a look at their site and was very impressed - nice looking parts and much cheaper than anything I could find in England.
I wonder if anyone in the UK/EU fancies a group buy, even if we don't meet the price-break (15% off 10 pieces of the same part) we could save on shipping.
By all reports, the shipping prices are amazingly reasonable. Try getting a quote from them. I haven't ordered from them myself, but have heard many peopel rave about them, including the inexpensive shipping.
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