Yepp got it ....stupid really.
Theres just so many posts, hard to keep track of all details
.
Like said why can't my preamp change the phase of the signal??
Very true.
Guess it's up to the listening test. Ordered 4 samples from national, hopefully they will come eventually.
Been thinking about the aluminium design. I can get a hold of the same material i think, can probably cut it at work.
Hopefully it will give me enough cooling if I run it with +-24V.
question: Isn't the offset just measured between output and ground??
The gymnasium classes are slowly comming back
Patrik
Theres just so many posts, hard to keep track of all details
.Like said why can't my preamp change the phase of the signal??
Very true.
Guess it's up to the listening test. Ordered 4 samples from national, hopefully they will come eventually.
Been thinking about the aluminium design. I can get a hold of the same material i think, can probably cut it at work.
Hopefully it will give me enough cooling if I run it with +-24V.
question: Isn't the offset just measured between output and ground??
The gymnasium classes are slowly comming back
Patrik
Thanks for the protos quote.
I'm the kind of guy who changes his mind all the time...like the wind blows. Have now made new plans since I put up my question a few hours ago.
I'll go for a four channel version now using propably two 300VA toroids. Four channels give me more flexibility than three channels, surround speakers, biwired centerspeaker or two centerspeakers, center + small effecient sub...etc
Also I'll make an external case for toroids and bridges.
I found a beautiful rear panel from an old Tube preamp that I'll use for RCAs and Speaker terminals, and I'll use four small black sinks as sides for the case.
But first I'll test out with one 300VA trafo for all four channels to see how it rocks. If Protos succeed in doing two channels with 120VA, then why shouldn't I be able to do four channels with one 300VA.... If I like it then I do not install an additional 300VA.
It's getting late and I'm twaddling now....
I'm the kind of guy who changes his mind all the time...like the wind blows. Have now made new plans since I put up my question a few hours ago.
I'll go for a four channel version now using propably two 300VA toroids. Four channels give me more flexibility than three channels, surround speakers, biwired centerspeaker or two centerspeakers, center + small effecient sub...etc
Also I'll make an external case for toroids and bridges.
I found a beautiful rear panel from an old Tube preamp that I'll use for RCAs and Speaker terminals, and I'll use four small black sinks as sides for the case.
But first I'll test out with one 300VA trafo for all four channels to see how it rocks. If Protos succeed in doing two channels with 120VA, then why shouldn't I be able to do four channels with one 300VA.... If I like it then I do not install an additional 300VA.
It's getting late and I'm twaddling now....
Attachments
2Bak said:
Looks good, I was thinking of doing something similar, but wasn't sure how to manufacture the front, back, top and bottom... Plus, I wanted "raw" heatsinks and aliminium pannels, how can I remove the black from a heatsink?
I really want to make one of these.... I can use the metal working tools at school.. Yeah, yours looks great.. Peter, I also switched to 50K audio pot but a dual layer one. I got tired of walking out of the "hot zone" back over to the amp to get the balance on. Unfortunately I didn't get a precision one so at some volume levels the balance is off anyway. You get what you pay for. I took the 1.5k back off the -V to the output. Your right, the amp is much more dynamic. I also sketched out a PCB the other night and I am going to imprint them this weekend.
One of the white papers TI has published on op amp design talked about putting the ground on the back side of the board from the signals paths. It is supposed to avoid inducing stray capacitance and impedance in the circuit. Can someone explain this to me as I would think it would be just the opposite.
One of the white papers TI has published on op amp design talked about putting the ground on the back side of the board from the signals paths. It is supposed to avoid inducing stray capacitance and impedance in the circuit. Can someone explain this to me as I would think it would be just the opposite.
Skinnyboy[/i] [B]Looks good said:Skinnyboy,
black is better than "naked" metall as the heat conductivity is greater when the sink is blak
/Peter
The heat conductivity should be the same or very close. There is a slight difference in heat emmission and absorbtion but it is so small that it doesn't matter. You should go for the look you want and not worry about the colour of the sinks, IMHO. Usually the GC will not produce that much heat anyway so the slight performance edge of the black anodized sinks will not matter that much. If you decide to strip of the black from your sinks than the surface smoothness is far more important. It should be smooth.
UrSv said:
Hi,
I am not sure what a "slight difference" means here, but the actual difference is about 11%, for anyone who would like to know, with the black finish being more effective.
Also, it is incorrect to suggest that a 'smooth' finish is better for heat transference with heat-exchangers.
With a rough surface, the surface area exposed to the air is slightly greater as a result of all the small 'hills and valleys' (with say a sand-blasted finish, it could be almost doubled), and this will tend to marginally improve heat transference, especially with 'forced' cooling by fan.
However, far more importantly, any 'polished' metal surface will reflect heat both ways, outwards from external sources, *and inwards* from within the metal sink, which results in the surface temperature of the sink being lower, and consequently reduces the heat being transferred to the air surrounding it.
The problem I see here is in effectively removing a 'hard anodised' finish, which most heatsinks are, unless the fins or whatever are few, and not very deep.
The anodising, whilst being quite shallow, is very much harder than the substrate, and any abrasion or acid etching attempted, is not likely to be very effective.
In practice, once the hard surface is broken through (and this occurs unevenly with highly-contoured heat-sinks) the exposed substrate is so relatively soft that it is then eroded at a vastly quicker rate than any remaining anodised finish, and the end result is usually a mess!
Sandblasting some sinks which are not highly-contoured, can be effective, but from my experiences, I would leave well alone if you care about the appearance of equipment. It is too easy to erode the thin heatsink fins away and destroy their otherwise 'uniform' appearance.
Regards,
Well, according to the japanese heatsink manufacturer Alpha
there is no clear answer that black is always better/worse.
(from http://www.micforg.co.jp/en/faqe.html)
Unless we use a fan I would guess it would be very rare to
get higher air velocities, so with no fan and no other heat sources
close to the amp, black is probably best.
there is no clear answer that black is always better/worse.
(from http://www.micforg.co.jp/en/faqe.html)
Unless we use a fan I would guess it would be very rare to
get higher air velocities, so with no fan and no other heat sources
close to the amp, black is probably best.
Christer said:
Hi,
I am sorry to appear pedantic here, but you seem to be rather misinterpreting what Alpha say in this quote, and for the sake of others, I will clear this up.
They clearly state "When air velocity is low" (i.e. non-forced air by fan, for example) "black anodised is *better*."
As I said above, it is generally 11% better, I can assure you. Whether or not this is significantly different, I haven't passed any opinion on.
What they also go on to say agrees entirely with what I have indicated, in that the black sinks *transfer* heat better *both ways* i.e. they 'get rid' of heat, but also 'pick up' heat from any external source better, as do rough finished sinks, compared with polished ones.
In the usual cases we are concerned with in audio, and certainly with these 'external to air heatsinks' on the outside of equipment, the ambient temperature will (should be!) much lower than that of the sink, so the heat will be transferred away from the amp better with black sinks than with silver.
What Alpha are referring to here is a situation (perhaps inside an amp) where a closely-located heatsink running at a much higher temperature, is *giving off* heat which is then picked up by the heatsink we are concerned with, and in such a case (because of the higher heat transfer of black sinks) the heatsink under discussion will pick up *more* heat than otherwise.
As they say, "the choice must be made depending on the environment" i.e whether the ambient temperature is lower (normally) or higher, but it has nothing to do with the *efficiency* of heat transfer, either way, which is related to whether the sink is black or plain silver, and to some extent its surface finish, as I said.
I hope this is now clear.
Regards,
Bobken said:
Hi,
I am not sure what a "slight difference" means here, but the actual difference is about 11%, for anyone who would like to know, with the black finish being more effective.
Also, it is incorrect to suggest that a 'smooth' finish is better for heat transference with heat-exchangers.
With a rough surface, the surface area exposed to the air is slightly greater as a result of all the small 'hills and valleys' (with say a sand-blasted finish, it could be almost doubled), and this will tend to marginally improve heat transference, especially with 'forced' cooling by fan.
However, far more importantly, any 'polished' metal surface will reflect heat both ways, outwards from external sources, *and inwards* from within the metal sink, which results in the surface temperature of the sink being lower, and consequently reduces the heat being transferred to the air surrounding it.
-snip-
Regards,
Thanks for the 11% number. I have never been able to find that number. As far as I understand that would be for a flat surface and the difference in radiation. That is not the same as heatsink with fins and the difference AFAIK (numbers given to me by two different heatsink engineers - I tend to believe them) is in the region of 3-5 % which in this case, IMHO, as well as a possible 11 % is to small to worry about.
As for the smooth surface I would say that there is a big difference for convection compared to forced cooling. Generally the uneven surface benefit is true but only for large surface variations. When we are talking, as you mentioned, sand-blasted surfaces the contrary happens and molecules of air get stuck in the uneven surface and effectively act as insulation. That is why turbulence in forced cooling increases efficiency a lot as that breaks up the insulating layer (laminar as mentioned earlier).
For the purpose of this example and DIY amplifiers in general I still maintain that the colour is not that important.
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