no it wasn't..
...but apparently my reply was...
Post #4001 : ...been travelling, and planning a couple of wedding receptions. What can I say, I am really bad at doing more than a couple of things at a time...
Patience
Stuart
...but apparently my reply was...
Post #4001 : ...been travelling, and planning a couple of wedding receptions. What can I say, I am really bad at doing more than a couple of things at a time...
Patience
Stuart
Terry,
The only thing about wirewounds to watch out for is excessive inductance but those resistors specs show very low inductance so they ought to work well. I was able to find some 1% non- inductive current shunt resistors for that spot and they have worked out nice for use in those pt.#'s.
Mark
The only thing about wirewounds to watch out for is excessive inductance but those resistors specs show very low inductance so they ought to work well. I was able to find some 1% non- inductive current shunt resistors for that spot and they have worked out nice for use in those pt.#'s.
Mark
Hi Guys,
If you were building one of these as a dual mono amp and your choices were two 25-0-25VAC 400vA or two 28-0-28VAC transformers, which would you use? Much difference?
Thanks, Terry
If you were building one of these as a dual mono amp and your choices were two 25-0-25VAC 400vA or two 28-0-28VAC transformers, which would you use? Much difference?
Thanks, Terry
Terry,
I bet you're referring to the toroids on E-Bay that the Par-Metal guy is selling.. A friend just bought two 400 va 28-0-28 volt trannies off of him and they were BARELY passable... but work. He had ordered the 500 va jobs but the seller slipped up and sent the 400 VA instead. They provided +/- 36 volts with 400mv Class-A bias. The seller did offer to exchange them!! I would think they'd need to be 30-0-30 volts AC at that size in order to end up at +/- 37.5 volts DC under load.
Mark
I bet you're referring to the toroids on E-Bay that the Par-Metal guy is selling.. A friend just bought two 400 va 28-0-28 volt trannies off of him and they were BARELY passable... but work. He had ordered the 500 va jobs but the seller slipped up and sent the 400 VA instead. They provided +/- 36 volts with 400mv Class-A bias. The seller did offer to exchange them!! I would think they'd need to be 30-0-30 volts AC at that size in order to end up at +/- 37.5 volts DC under load.
Mark
Hi Mark,
I don't know who Par-Metal is. These are from this guy.
I have bought from him before and didn't have any trouble with the transformers I got. I don't know how to check the vA but they both put out the voltage that was stated. One is running in my P101 and it works fine.
He shows test reports on the individual product pages.
Blessings, Terry
I don't know who Par-Metal is. These are from this guy.
I have bought from him before and didn't have any trouble with the transformers I got. I don't know how to check the vA but they both put out the voltage that was stated. One is running in my P101 and it works fine.
He shows test reports on the individual product pages.
Blessings, Terry
Thats the guy Terry. The transforners seem to be of pretty high qulaity and have very flexible leads.
Mark
Mark
For those of us not so good with transformer math - going dual mono with 400VA or 500VA toroids what kind of secondaries are needed?
Thanks,
Brad
Thanks,
Brad
Mark A. Gulbrandsen said:
I wonder. Are the Krell transformers rated at 37.5VDC or is that what they produce under load? Seems that they would list the rating rather that what they actually do.
How important is it that it actually sees 37.5V? I know I got a bit of guff from folks because mine was a 30-0-30 500vA. Does two or three volts really make that much difference?
Blessings, Terry
googler said:
I was always told to use the square route of 2 (1.414) for figuring DC from AC. 37.5VDC / 1.414 = 26.5VAC. There is some loss from the bridge so I think the optimum number is more like 27-0-27VAC. The real guys can probably explain it better.
Blessings, Terry
still4given said:
I think Krell wanted the KSA50 to do at least 50 in 8, 100 in 4, 200 in 2 Ohms.
That it does, at 78 watts continuous power in 8 Ohms Krell was very conservative.
With a few volts less you'll loose something like a 1/2 dB, if you can hear the difference it means you have very sensitive hearing, Terry.
With a 10% voltage variation the amplifier will not function worse, though not exactly in the optimum of maximum bandwidth versus current noise of the devices.
Thats how I've always done it too Terry, There are just differences from brand of transformer to other brands. Losses, efficiency, etc and every brand is going to be different. You'd need that KRell KSA-50 that you were gong to bid on E-Bay and disconnect the tranny and measure it no-load and then under load to see exactly what they were doing and using. As far as the power output difference between 36 and 37.5 volts rails its insignificent but the 400 VA that we got leaves very little margin. I would call it border line ok. In theory the 500 VA toroid's voltage wold be a bit stiffer on the voltage rating under load and not collapse as much. I'm using 700 VA units and running the rails run at +/- 39 volts under400mv of Class A bias. The other thing to consider is if you want to really double the P.O. each time you halve the impedecne which the KSA-50 should do eaily down to 4 ohms. I don't think the original was really rated to do 2 ohms and would probably blow its fuse if asked to do so for very long. I remember someone saying on this thread(good luck finding it though) that the KSA-50 didn't get along well with Apogees.
Mark
Mark
Thanks guys,
I didn't think a couple of volts would matter that much but I thought I'd ask to be sure. Mine is running on 30-0-30 500vA just fine. As a matter of fact I ran it yesterday for quite a while on 2 ohms and didn't notice any ill effects. I checked the temps a few times and it was fine. Sure didn't blow any fuses.
This amp plays plenty loud for anything I need. I can't imagine needing to double the PO every time I dropped in ohms.
On the wiki it says that the original used 400vA tranformers. Why would I need to go bigger. Those amps cost a fortune. I don't suppose they would still be popular if they didn't perform.
Blessings, Terry
I didn't think a couple of volts would matter that much but I thought I'd ask to be sure. Mine is running on 30-0-30 500vA just fine. As a matter of fact I ran it yesterday for quite a while on 2 ohms and didn't notice any ill effects. I checked the temps a few times and it was fine. Sure didn't blow any fuses.
This amp plays plenty loud for anything I need. I can't imagine needing to double the PO every time I dropped in ohms.
On the wiki it says that the original used 400vA tranformers. Why would I need to go bigger. Those amps cost a fortune. I don't suppose they would still be popular if they didn't perform.
Blessings, Terry
Hi Still4given,
in my opinion moving the fan to become a pusher will make it more efficient not less efficient. Remember to check the fan blade curve is pulling /pushing the correct way. The input edge of the fan blade should point in the direction of rotation not towards the incoming air, the exit edge of the blade should point towards the output end ( towards the sink). So the blade has an angle and a curve. A good fan blade will have both and the angle will change(twist) along the length of the blade, some will even have a width change as well. All these angles and curves and twists and tapers will have a narrow optimum band for flow rate vs speed to get the maximum efficiency from electricity consumed and minimise wasted energy producing noise. I do not have the expertise to guide you on selecting the optimum speed.
I also think a low voltage (12V or 24V) fan motor will be quieter than a mains driven motor. A big fan turning slowly will be quieter than a small fan turning faster even at the same flow rate.
Do you have a facility to apply only 90Vac or 100Vac to your fan motor? If so, temporarily reduce your Iq to about 1.4A to 1.6A and run the amp in classAB with reduced fan speed to assess the noise problem.
Back to your proposed passively cooled sinks. One 8 by 12 has no hope of cooling your KSA requiring a dissipation of 140watts. Two 8 by 6 sinks will get nowhere near your requirement either.
Your Leach has a similar setup;- one tall sink per channel? It is running classAB and gets pretty warm. Try an experiment to see what temp you can push the Leach to by increasing the output stage Iq. Then measure the dissipation (Vrail times Iq times 2) to see how it compares to your required 140/160/180watts dissipation. While the output stage is temp stressed like this DO NOT apply any drive voltage to the tested channel, use that input shorting link.
Are you getting close to my prediction in the quality stakes;- Krell is best, Leach is close behind and ESP is well behind? Did you arrange for ALL your amps to have the same gain? This becomes quite important when wanting to swap equipment around and even more so if you start bi-amping or consider going active. It will remove your problem of matching levels and mixing preamps. Many manufacturers sell a range of amps with different output powers and they generally choose a gain for the whole range to ensure compatability. I recommend you do the same.
in my opinion moving the fan to become a pusher will make it more efficient not less efficient. Remember to check the fan blade curve is pulling /pushing the correct way. The input edge of the fan blade should point in the direction of rotation not towards the incoming air, the exit edge of the blade should point towards the output end ( towards the sink). So the blade has an angle and a curve. A good fan blade will have both and the angle will change(twist) along the length of the blade, some will even have a width change as well. All these angles and curves and twists and tapers will have a narrow optimum band for flow rate vs speed to get the maximum efficiency from electricity consumed and minimise wasted energy producing noise. I do not have the expertise to guide you on selecting the optimum speed.
I also think a low voltage (12V or 24V) fan motor will be quieter than a mains driven motor. A big fan turning slowly will be quieter than a small fan turning faster even at the same flow rate.
Do you have a facility to apply only 90Vac or 100Vac to your fan motor? If so, temporarily reduce your Iq to about 1.4A to 1.6A and run the amp in classAB with reduced fan speed to assess the noise problem.
Back to your proposed passively cooled sinks. One 8 by 12 has no hope of cooling your KSA requiring a dissipation of 140watts. Two 8 by 6 sinks will get nowhere near your requirement either.
Your Leach has a similar setup;- one tall sink per channel? It is running classAB and gets pretty warm. Try an experiment to see what temp you can push the Leach to by increasing the output stage Iq. Then measure the dissipation (Vrail times Iq times 2) to see how it compares to your required 140/160/180watts dissipation. While the output stage is temp stressed like this DO NOT apply any drive voltage to the tested channel, use that input shorting link.
Are you getting close to my prediction in the quality stakes;- Krell is best, Leach is close behind and ESP is well behind? Did you arrange for ALL your amps to have the same gain? This becomes quite important when wanting to swap equipment around and even more so if you start bi-amping or consider going active. It will remove your problem of matching levels and mixing preamps. Many manufacturers sell a range of amps with different output powers and they generally choose a gain for the whole range to ensure compatability. I recommend you do the same.
AndrewT said:
Hi Andrew,
I believe that moving the fan to the inside will provide enough air to cool the heatsink. The fan I presently have was quiet enough when first installed. It has become noisy over time. I believe that even though they claim that it is OK at 70c that it is not. It has developed a rattle like it is out of balance slightly and the bearing is getting loose. I should have bought a better fan me thinks. I like the way everything works with the fan between the heatsink and the back panel. If I swap the fan and heatsink I will have to move the outputs on the back panel. They currently reside below the fan.
Why do you think a DC motor is quieter than an AC fan?
I tried running the fan on lower voltage. It quiets it some but now that it has developed a rattle, nothing is going to help it. I will have to replace it. That is why I asked for suggestions for a fan that might live OK where I have this one, since I need to replace it anyway I thought I'd try to find one that doesn't mind the heat.
AndrewT said:
I'll take your word for it on the size of the sinks. I'm not going to do any more experiments on that Leach for now. That was a nightmare getting it going again and cost me several devices while I was at it. It is playing wonderfully now and I intend to leave it that way.
AndrewT said:
I'm not sure what you have against the ESP P101. Have you built one? I am developing a fondness for the Krell now that I have the proper caps installed. It has a very musical sound. It is still not as open as the Leach or the P101 but it is not as harsh on some things either. IMHO, the P101 is not "far behind" anything. Both the Leach and the P101 have a very clear and open sound. They both have that SS sound however, more so than the Krell. I think they are both more fatiguing to listen to for an extended period of time than the Krell. I like the Krell well enough now that I plan to build another with Al's boards. I going to spend the money to get good part this time and see if I can really make it shine. If it does, I might replace the parts in the one already have. I doubt I'll build another Low TIM with the extra boards I have. I have a friend who wants to get into the hobby and I may hook him up with the Leach boards. I think that would be a good place for him to start.
Blessings, Terry
Re: no it wasn't..
gah stuart my man you're killing me
no prob... patience is a virtue! sry I missed your post BTW
Stuart Easson said:
gah stuart my man you're killing me
no prob... patience is a virtue! sry I missed your post BTW
At the beginning of the 20est century Allen Beranek made a formule to calculate the soundproduction of a fan.
It learns that besides of motornoise, only the airquantity (m3/s) and the total pressure difference (Pa) of the fan are responseble of the soundproduction,
only for a fan efficientie > 70% and with a margin of 4 dB (becouse off differences in airbladeshape).
So select a fan with the following specifications: lowspeed, very high efficientie.
For the airnoise there is no difference between a DC and AC motor; For the motornoise there is. AC motor makes more noise than a DC motor.
It learns that besides of motornoise, only the airquantity (m3/s) and the total pressure difference (Pa) of the fan are responseble of the soundproduction,
only for a fan efficientie > 70% and with a margin of 4 dB (becouse off differences in airbladeshape).
So select a fan with the following specifications: lowspeed, very high efficientie.
For the airnoise there is no difference between a DC and AC motor; For the motornoise there is. AC motor makes more noise than a DC motor.
Mark A. Gulbrandsen said:Eugenio,
I just tease you a little
___________________________________
Terry and all, we SCORED on these boards big time!
Mark
Hi Mark,
Not to be a pest, but how close are they to being in our hands?
Blessings, Terry
Actually I thought I'd check in since I'm about to dismantle and move my computer. I do have my lap top but won't be checkin gin as often over the next few days. I started moving last Thursday and I only got a few boards shipped out on Saturday because of long lines at the Post Office. I just moved the table and all the order doo-doo over to the new house and have that all set back up. So the remainder of those that ordered only KSA-50 boards will have theirs shipped out on Monday Morning. I will be out of town all that week on an install over in Wyoming so those that ordered both Power Supply AND KSA-50 boards boards will have them shipped the following week. Sorry for the dealy in shiipping but thats the best I can do at the moment with all the mayhem... I was supposed to move over a week ago!!! Stupid reality people..... I also have to be out of this house by tommrrow morning and have at least several more hours of work to do here.
Then I plan on checking onto the local Morgue for a long rest.....
Mark
Then I plan on checking onto the local Morgue for a long rest.....
Mark
