Hi Suresh,
From memory the dissipation of a 4R ALPHA will be around 100W, and this is a substantial heatsink but it really should be 300mm rather than 215mm.
I would expect the rating around 0.4C/W from those dimensions. So it could run at 40C above ambient. This is a bit high; if your room temp is 25C, that's on the limit at 65C.
Ciao,
Hugh
From memory the dissipation of a 4R ALPHA will be around 100W, and this is a substantial heatsink but it really should be 300mm rather than 215mm.
I would expect the rating around 0.4C/W from those dimensions. So it could run at 40C above ambient. This is a bit high; if your room temp is 25C, that's on the limit at 65C.
Ciao,
Hugh
I recall a conversation with Vimal that a 275mm tall x 300mm deep x 40mm fin sink was needed per channel for 100w. The 200mm x 215mm will probably need a fan.
Hello Suresh,
Please look at this link to get a 300mm x 83mm fin.
HS205-215-300 | Akashheatsink.com
Thanks
Balaji
Please look at this link to get a 300mm x 83mm fin.
HS205-215-300 | Akashheatsink.com
Thanks
Balaji
Finally spent some time listening to my Alpha 20w today. I have to say it sounds very nice from what I can hear. Unfortunately I have a hum that I can’t get rid of. I’ll list what’s happening and what I’ve tried in hopes anyone has some ideas.
- Only present with source plugged in to inputs
- Hum does not change with any source i’ve tried: iPhone, laptop w/ Sabre DAC, AKSA Lender Preamp with CD player.
- Does not change with change in volume
- Is equal between both speakers
- Did not change with a change in my grounding scheme
- Grounding Scheme 1 - star ground all grounds to CL60 thermistor, thermistor to case
- Grounding Scheme 2 - star ground all except PSU ground to case. PSU to thermistor. Thermistor to case at star ground.
- Tried switching transformer primaries. No change in hum.
- Tried a different outlet. No change in hum.
- Only present with source plugged in to inputs
- Hum does not change with any source i’ve tried: iPhone, laptop w/ Sabre DAC, AKSA Lender Preamp with CD player.
- Does not change with change in volume
- Is equal between both speakers
- Did not change with a change in my grounding scheme
- Grounding Scheme 1 - star ground all grounds to CL60 thermistor, thermistor to case
- Grounding Scheme 2 - star ground all except PSU ground to case. PSU to thermistor. Thermistor to case at star ground.
- Tried switching transformer primaries. No change in hum.
- Tried a different outlet. No change in hum.
Does the hum disappear when you ground the input HOT pin?
If no, you may have insufficient ripple rejection, so you need either bigger C or bigger R between or both.
If yes, you have an earth loop between source and amp via preamp.
Fixing hum issues on audio amps is a black art and easily the most issue of building your own system.
HD
If no, you may have insufficient ripple rejection, so you need either bigger C or bigger R between or both.
If yes, you have an earth loop between source and amp via preamp.
Fixing hum issues on audio amps is a black art and easily the most issue of building your own system.
HD
Jwjarch,
Sorry to hear about the hum issue. What power supply are you using? I suspect you have a single transformer with dual secondaries forming the dual rails shared between the two channels? Does hum go away if you unplug one of the input RCAsl for one of the channels? If so, that’s a ground loop that’s hard to get rid of without resorting to dual trafos and monoblock design.
Sorry to hear about the hum issue. What power supply are you using? I suspect you have a single transformer with dual secondaries forming the dual rails shared between the two channels? Does hum go away if you unplug one of the input RCAsl for one of the channels? If so, that’s a ground loop that’s hard to get rid of without resorting to dual trafos and monoblock design.
I had to do ground lift resistor to Alpha 20 to get it quiet, and do it right with lifting one capacitor leg also out from pcb and wire it behind resistor. Where this wire travels makes difference also, because it seems to pick interference easily. I can check that connection later. B.B. have build in ground lifting resistor if remember right?
Earth loop should be around 10R; 100R is a little high.
The signal Earth should include fb shunt resistor, input ground leak, and the LP filter cap. The float resistor should run from the precise center of the power ground, which is normally a track connecting negative of positive rail and positive of negative rail. This point also connects to the cold speaker connector.
Hope this helps,
Hugh
The signal Earth should include fb shunt resistor, input ground leak, and the LP filter cap. The float resistor should run from the precise center of the power ground, which is normally a track connecting negative of positive rail and positive of negative rail. This point also connects to the cold speaker connector.
Hope this helps,
Hugh
No more hum!!! After trying a few more different grounding schemes I have success. I used a loop breaker type scheme based on this image that I found in the chip amp forum. There is still some barely audible noise when I put my ear up to the speaker but I’m hoping my final wiring cleanup will help bring that down even more. So excited to have solved this issue!!!
So on to the listening! I currently have this amp powering a pair of Betsy drivers on 18”x18” 1/2” foam core open baffles. Not exactly a final system but my impressions are really good nonetheless. The sound is fairly neutral, possibly bordering on warm. Detail is excellent as is stereo image and soundstage. I’m “seeing” performers in the room more than any system I’ve put together yet. I’ll be listening to this amp for a while.
Edit: Oh! I almost forgot to mention I was only driving the Amp with my iPhone 7 and playing songs off of Amazon Music. Hardly the best source material. I’ll have to hook up my AKSA Lender Pre and get some CDs going soon.
So on to the listening! I currently have this amp powering a pair of Betsy drivers on 18”x18” 1/2” foam core open baffles. Not exactly a final system but my impressions are really good nonetheless. The sound is fairly neutral, possibly bordering on warm. Detail is excellent as is stereo image and soundstage. I’m “seeing” performers in the room more than any system I’ve put together yet. I’ll be listening to this amp for a while.
Edit: Oh! I almost forgot to mention I was only driving the Amp with my iPhone 7 and playing songs off of Amazon Music. Hardly the best source material. I’ll have to hook up my AKSA Lender Pre and get some CDs going soon.
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Wonderful results, JW, and a great idea by adding the earth float resistor and the input RCA caps to chassis! That schem you supply is excellent, thank you for finding it.
I'm a little pushy, but I don't believe you will hear a better sound with this Class A ALPHA. Much of the benefit is NP's brilliant active CCS at the output stage, but it really is psychoacoustically 'correct' when linked to the AKSA/Lender front end.
HD
I'm a little pushy, but I don't believe you will hear a better sound with this Class A ALPHA. Much of the benefit is NP's brilliant active CCS at the output stage, but it really is psychoacoustically 'correct' when linked to the AKSA/Lender front end.
HD
Thanks everyone for the guidance and suggestions. I’m finding that if you keep searching, the answers for almost any question are somewhere on diyAudio.
Just did some more cleanup on my wiring. I may have brought a bit of hum back into the system, mostly in the left channel, but it’s still pretty good. Going through my CD collection today with my AKSA Lender Preamp in the system. Sounds SO good!
X, I do enjoy the quality of Amazon streaming in general. Just trying to squeeze a little more out with CD quality. I have a slowing growing collection of hi-res audio on my computer as well.
Just did some more cleanup on my wiring. I may have brought a bit of hum back into the system, mostly in the left channel, but it’s still pretty good. Going through my CD collection today with my AKSA Lender Preamp in the system. Sounds SO good!
X, I do enjoy the quality of Amazon streaming in general. Just trying to squeeze a little more out with CD quality. I have a slowing growing collection of hi-res audio on my computer as well.
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Thanks for the suggestion Steve. That is some talent! Unbelievable to watch on youtube as well. And Adrian is right in my own backyard here is California.
In anyone has any other suggestions, I’m interested in listening to all genres of music. I have Fleetwood Mac, Rumors playing right now but also had Nirvana, Lang Lang, Miles Davis, Nancy Wilson, Horace Silver, and Oscar Peterson, among others, playing today.
In anyone has any other suggestions, I’m interested in listening to all genres of music. I have Fleetwood Mac, Rumors playing right now but also had Nirvana, Lang Lang, Miles Davis, Nancy Wilson, Horace Silver, and Oscar Peterson, among others, playing today.
jwjarch,
yes Fleetwood Mac- Rumors is following since my youth in late 70is.
I like the voice of that nice girl: Rebecca Pidgeon.
Chesky has produced with
any very good artists too.
In tonality this Chesky productions has its own quality.
YouTube
Enjoy.
A little pre...listen from Telecats albumhttps://www.allmusic.com/album/telecats-i-mw0000602987
yes Fleetwood Mac- Rumors is following since my youth in late 70is.
I like the voice of that nice girl: Rebecca Pidgeon.
Chesky has produced withany very good artists too.
In tonality this Chesky productions has its own quality.
YouTube
Enjoy.
A little pre...listen from Telecats albumhttps://www.allmusic.com/album/telecats-i-mw0000602987