Hi guys,
Thanks for taking the time to work this out, though I'm not sure what the final outcome is.
This is what I did, just to try some things. I had some 670ohm 1/2W resistors so I wired them in parallel. This gave me a little under 100V at the fan. I can still hear it just slightly but I can live with it. They do get a bit warm however so I think maybe I should go with a higher watt resistor. What I'm thinking of doing is to get two thermal switches of different heat ratings that would by-pass two 150ohm resistors one at time to increase fan speed if the heatsink becomes too hot. I ran the amp for two hours last night and the heatsink temp never reached 45c so I think there is enough air now. This might mean that I could go with even a lower fan speed thereby reducing the noise even further. Perhaps I should try two 200ohm resistors in series and see if that still gives enough air.
Do any of you know where I could get the necessary thermal switches and give me an idea of what values they should be to work for what I'm trying to do?
Another thing. Earlier I asked about the different models of outputs for this amp. Can someone who is experienced with these make a suggestion?
Thanks for taking the time to work this out, though I'm not sure what the final outcome is.
This is what I did, just to try some things. I had some 670ohm 1/2W resistors so I wired them in parallel. This gave me a little under 100V at the fan. I can still hear it just slightly but I can live with it. They do get a bit warm however so I think maybe I should go with a higher watt resistor. What I'm thinking of doing is to get two thermal switches of different heat ratings that would by-pass two 150ohm resistors one at time to increase fan speed if the heatsink becomes too hot. I ran the amp for two hours last night and the heatsink temp never reached 45c so I think there is enough air now. This might mean that I could go with even a lower fan speed thereby reducing the noise even further. Perhaps I should try two 200ohm resistors in series and see if that still gives enough air.
Do any of you know where I could get the necessary thermal switches and give me an idea of what values they should be to work for what I'm trying to do?
Another thing. Earlier I asked about the different models of outputs for this amp. Can someone who is experienced with these make a suggestion?
output transistors
Terry,
Using the specifications of the transistors as a guide I think it's clear the 4281/4203 are the 'best'. However, they are quite a lot higher bandwidth transistors than the 15003/4 originally used, so there is at least a little potential for instability.
If you are willing to experiment I'd try them because they are really good transistors, if not, go with the 21193/4, they have better gain linearity, ie lower distortion, than the originals, but are still modest in their Ft.
The 3281/1302 are similar the the 4281, just a prior version if you like, and IIRC Pinkouse tried and liked them better than the 15003/4.
HTH
Stuart
Terry,
Using the specifications of the transistors as a guide I think it's clear the 4281/4203 are the 'best'. However, they are quite a lot higher bandwidth transistors than the 15003/4 originally used, so there is at least a little potential for instability.
If you are willing to experiment I'd try them because they are really good transistors, if not, go with the 21193/4, they have better gain linearity, ie lower distortion, than the originals, but are still modest in their Ft.
The 3281/1302 are similar the the 4281, just a prior version if you like, and IIRC Pinkouse tried and liked them better than the 15003/4.
HTH
Stuart
AndrewT said:
Bernouilli's Equation for incompressible viscous fluids works for fan air flow :
without extracted power and/or differences in height, flow is proportional with speed.
http://www.engineeringtoolbox.com/bernouilli-equation-21_183.html
If you measure the static resistance of a fan coil, it's often like a 5th of the dynamic resistance based on voltagedrop and current.
The phase speed is a factor too, power consumption of a fan motor at 60 Hz is lower than with 50 Hz operation.
I've found using Ohms law for determining series resistor power rating an easy approximation.
Re: output transistors
Hi Stuart,
Thanks for the info.
I used 4281/4203 in the Leach Low TIM is just built. That amp is very articulate. I just didn't know if there was a reason to use the lower rated transistors for some reason. Since I already own enough of each type I thought I'd ask. I think I'll stick with the 4281/4203 then.
As far as the fan goes, is 2w sufficient then for the resistors? Should I just go ahead and use 5w? I already have them.
Do any of you guys know what would be a good temperature to have a thermal switch kick in? Have any of you used them?
Thanks, Terry
Stuart Easson said:
Hi Stuart,
Thanks for the info.
I used 4281/4203 in the Leach Low TIM is just built. That amp is very articulate. I just didn't know if there was a reason to use the lower rated transistors for some reason. Since I already own enough of each type I thought I'd ask. I think I'll stick with the 4281/4203 then.
As far as the fan goes, is 2w sufficient then for the resistors? Should I just go ahead and use 5w? I already have them.
Do any of you guys know what would be a good temperature to have a thermal switch kick in? Have any of you used them?
Thanks, Terry
Al, Did you get my e-mail?
Also I shipped out a large batch of boards over the weekend so some will finally start to receive them over the next week or so. The remainder will be sent out as soon as I get back from Rock Springs. I know a few of you are getting impatient and I don't blame you but work has to come before hobbies.... unfortunately.....
Also I shipped out a large batch of boards over the weekend so some will finally start to receive them over the next week or so. The remainder will be sent out as soon as I get back from Rock Springs. I know a few of you are getting impatient and I don't blame you but work has to come before hobbies.... unfortunately.....
Mark A. Gulbrandsen said:
Please tell me that mine were in that batch.
It's going to be a lonely weekend with the family gone and no amp to build.🙁
Based on this statement;
I hurried and ordered all of my parts. I'll keep my fingers crossed.
Blessings, Terry
still4given said:
Well if your not, maybe you could swap out the transistors in your current ksa-50 and let us know which you like better? 😎
~Brad
Alright I'll do it...
I ordered the different output transistor candidates today. After I get my boards, parts, powersupply components, and just about everything else together - I'll try each of them out. If I find a notable difference I will report it here.
~Brad
I ordered the different output transistor candidates today. After I get my boards, parts, powersupply components, and just about everything else together - I'll try each of them out. If I find a notable difference I will report it here.
~Brad
Hi All-
I know I asked this before, but now I'm putting out money so I want to double check.
How long does this extrusion have to be to support 1 channel? That is both the +V AND - V sides.
http://www.mmmetals.com/extrusions/drawings/mm10332.jpg
Extrusion Part Number = MM10332
Width = 8.350
Height = 2.000
Base Thickness = 0.250
Weight = 5.906
Rq oC/W = 1.0
Surface Area (sq"/1") = 57.648
I would like to just use 1 heat sink per side, but will use 2 if REQUIRED. the amp will be 8 inches tall.
I have some 16" long x 8" wide sections of these and will have them cut into 8" x 8" squares and place 2 per side and make the following style chassis. I will have 4-5 of the chassis made if anyone is intrested in one. I will see if I can post the pictures of my last chassis I had made for my little GC..
http://www.diyaudio.com/forums/showthread.php?s=&threadid=40755
I know I asked this before, but now I'm putting out money so I want to double check.
How long does this extrusion have to be to support 1 channel? That is both the +V AND - V sides.
http://www.mmmetals.com/extrusions/drawings/mm10332.jpg
Extrusion Part Number = MM10332
Width = 8.350
Height = 2.000
Base Thickness = 0.250
Weight = 5.906
Rq oC/W = 1.0
Surface Area (sq"/1") = 57.648
I would like to just use 1 heat sink per side, but will use 2 if REQUIRED. the amp will be 8 inches tall.
I have some 16" long x 8" wide sections of these and will have them cut into 8" x 8" squares and place 2 per side and make the following style chassis. I will have 4-5 of the chassis made if anyone is intrested in one. I will see if I can post the pictures of my last chassis I had made for my little GC..
http://www.diyaudio.com/forums/showthread.php?s=&threadid=40755
Attachments
Torroid Trannies
Terry,
Mark told me you were considering purchasing some trannies from that ebay guy. My advice is to NOT do it. I purchased two weeks ago, and they sent my correct trannies to someone in San Francisco, and I got shorted with the incorrect ones.
I ordered the 500 VA, and they sent the 400. I have sent several emails telling them to correct this and they have been so slow in responding, and giving lame excuses that tomorrow, I am going through the PIA process of securing their phone number from ebay and calling and the hassles. So my Krell gets put off for another couple of weeks. I guess I'll go back and work on my 5 year ProAc clone project...sigh...
Lyndon
Terry,
Mark told me you were considering purchasing some trannies from that ebay guy. My advice is to NOT do it. I purchased two weeks ago, and they sent my correct trannies to someone in San Francisco, and I got shorted with the incorrect ones.
I ordered the 500 VA, and they sent the 400. I have sent several emails telling them to correct this and they have been so slow in responding, and giving lame excuses that tomorrow, I am going through the PIA process of securing their phone number from ebay and calling and the hassles. So my Krell gets put off for another couple of weeks. I guess I'll go back and work on my 5 year ProAc clone project...sigh...
Lyndon
rabstg said:
Let me be the 1st to say that I'm interested in one of those. When you get the final dimensions down, please post. Also, it looks like from the prior one your heat sinks match very nicely so can you include them?
Cant wait to see some of these other amps.
googler said:
Hi Brad,
I'm not trying to be difficult but I used TO-3 outputs. I would have to go through some contortions to test TO-264 devices. I'm trying to learn to leave well enough alone. 😀
Hi Lyndon,
Sorry to hear of you trouble. I have bought from him twice before and both times with favorable results. I hope they make it right. I may send an email on your behalf and let them know how important a good review on the DIYaudio forum is to someone like them. My two trannies are already on thier way to my house so I hope they got it right. Thanks for caring enough to warn me.
Blessings, Terry
lgreen said:
I'll be the second to say that I too am interested in one of those
still4given said:
No worries - I'd like to listen to each of them anyway so that if and when I speak about output transistors, it will be from experience .
~Brad
lgreen said:
googler said:
Well first of all I need to find out how long the extrusion needs to be to support a single channel ofthe KSA-50 clone.
I would like the amp to produce the full 50 watts in class-A into 8 ohms.
rabstg said:
May I ask if you are using fans?
I asked a couple of days ago about my heatsinks which are 8" x 12 1/2" and was told that they wouldn't be close to being enough for this amp without fans. I wanted to go without them due to noise. If you look back just a couple of pages you'll see where they did the calcs.
Blessings, Terry
I don't remember whom it was who built one of the first amps with the gold sinks mounted horizontally but they were the same sinks I have here.
When I originally posted about these sinks I was told that 6 inches would be adequate but 8 was the safe bet.
I will see if I can find the builders thread that was started some time ago.
Edit: Found
http://www.diyaudio.com/forums/showthread.php?s=&threadid=53160&highlight=
Same heat sinks only mounted vertically NOT horizonally.
Natural convection should help out tremendously.
When I originally posted about these sinks I was told that 6 inches would be adequate but 8 was the safe bet.
I will see if I can find the builders thread that was started some time ago.
Edit: Found
http://www.diyaudio.com/forums/showthread.php?s=&threadid=53160&highlight=
Same heat sinks only mounted vertically NOT horizonally.
Natural convection should help out tremendously.
Trannies
Terry,
I am sure your transformers will be fine. I called Mark long distance, because I did get an answer from the ebay guy, and I am going to trade the trannies I have for the 500 VA 31-0-31V models. Better to unwrap than to wind I always say.
The build quality on these if very good, close to my Victoria Magnetics in the Pass Aleph 3.
Can anybody tell me in this epic thread if anyone has come up with some good looking chassis ideas? Where are those hearty few inspired by Peter Daniel? Maybe he can shrink the Krell Klone into a Krell Chipamp, or GRollins and BrianGT can come up with a Krell Mini-A?
Let's see someone come up with something fresh, rather than the basic chassis, or a Theta Miles ho-hum computer tower in black.
Lyndon
Terry,
I am sure your transformers will be fine. I called Mark long distance, because I did get an answer from the ebay guy, and I am going to trade the trannies I have for the 500 VA 31-0-31V models. Better to unwrap than to wind I always say.
The build quality on these if very good, close to my Victoria Magnetics in the Pass Aleph 3.
Can anybody tell me in this epic thread if anyone has come up with some good looking chassis ideas? Where are those hearty few inspired by Peter Daniel? Maybe he can shrink the Krell Klone into a Krell Chipamp, or GRollins and BrianGT can come up with a Krell Mini-A?
Let's see someone come up with something fresh, rather than the basic chassis, or a Theta Miles ho-hum computer tower in black.
Lyndon