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Old 22nd February 2013, 03:45 PM   #231
ncg2013 is offline ncg2013  United Kingdom
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ditto - almost - going to make the chassis....
I was up until the wee hours of the morning last night sifting though Mouser datasheets but eventually managed to press buy.
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Old 23rd February 2013, 12:53 AM   #232
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Default Help!

Ok - this is my first post - so please be gentle!
I too have recently ordered a bunch of PCBs (two honeybear boards, 1 psu - I wasn't thinking and should've ordered two so I'm gonna order another, the soft start and speaker protection board), and am at a loss where to start. It seems that the amount of capacitance required for the PSU is dependent on the transformer that I've chosen as well as the type of speakers I plan on using with said amplifier. So here comes a bunch of questions (with I'm sure many more to follow)...

1) Using the Antek AN-8445, if I calculated correctly, will put out 63.64VDC - and although I notice that Jojo's build used the same transformer and 63V caps, I really should be using caps rated a bit higher - and finding 30mm 80v caps is getting to be difficult. Best I can find are 6800μF, 80v, 30mm Cornell Dubilier caps - so if I use 8 per board - is 54,400μF enough? Or am I still 'safe' using 63v caps with 10-12000μF?

2) For the speaker protection PCB I assume that the 12v secondary will be used, I will need 6v relay coils for K1 and K2. Is there a reason / advantage to using the 18v secondary and two 12v relay coils instead?

Any other ideas / suggestions? I plan on driving a pair of Paradigm Reference Studio 60 v.4s, and although they're relatively efficient at 91db, they really do like to suck back power - hence with the AN-8445 I'm really hoping to get as much out of this amp as possible!

Thanks for the help (any input is greatly appreciated!)

David

Last edited by davidvoss; 23rd February 2013 at 01:07 AM.
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Old 23rd February 2013, 09:12 AM   #233
bkevin is offline bkevin  United Kingdom
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Default Is this the right amp for me?

Hi all
A fresh one here needing guidance and advice. Having spent some time reading this excellent thread I thought the HB power amp was just what i needed to drive my fairly power hungry 4 ohm stereo (2 way) speakers -so i was just about to start costing things up and ordering parts when I came across PSU recommendations for 4 ohm loads and realised that getting what i want maybe isn't as simple as bunging in a nice fat 45-0-45 torroidal (as i'd planned!)
Ideally i'm looking to get around 250W (speakers say they want 230W) but having read the postings on this subject I'm now unsure whether the prescribed max. 35-0-35 transformer (for 4 ohm loads) is really going to produce much more than i currently get from my Arcam integrated which is about 170W.
I'm clever enough to build one but not clever enough go down the route of design change so I guess need advice on whether the HB power amp in it's standard form is really going to improve what I've currently got - a very good amp but one which runs out of puff when driven too hard (and risks damaging my nice speakers!).
Many thanks folks!
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Old 23rd February 2013, 01:28 PM   #234
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Default Re : Is this the right amp for me?

Quote:
Originally Posted by bkevin View Post
Hi all
A fresh one here needing guidance and advice. Having spent some time reading this excellent thread I thought the HB power amp was just what i needed to drive my fairly power hungry 4 ohm stereo (2 way) speakers -so i was just about to start costing things up and ordering parts when I came across PSU recommendations for 4 ohm loads and realised that getting what i want maybe isn't as simple as bunging in a nice fat 45-0-45 torroidal (as i'd planned!)
Ideally i'm looking to get around 250W (speakers say they want 230W) but having read the postings on this subject I'm now unsure whether the prescribed max. 35-0-35 transformer (for 4 ohm loads) is really going to produce much more than i currently get from my Arcam integrated which is about 170W.
I'm clever enough to build one but not clever enough go down the route of design change so I guess need advice on whether the HB power amp in it's standard form is really going to improve what I've currently got - a very good amp but one which runs out of puff when driven too hard (and risks damaging my nice speakers!).
Many thanks folks!
If you are trying to build an amp better than Arcam, your amp building skill is very critical.

Please noted that the build guide gives you very good info of how to make it sound and how to make it stable.

However, it did not specify exactly what transistor combo and what capacitor combo to use. That will be up to your skill to fine tune the sound. The wiring choice also affect the sound.

By the way, do you really need 250 W ? When listening to the music at max volume that you ever use, can you monitor the output and see how much you are really using ?

Lou
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Old 23rd February 2013, 05:58 PM   #235
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Default Re : Help !

Quote:
Originally Posted by davidvoss View Post
Ok - this is my first post - so please be gentle!
I too have recently ordered a bunch of PCBs (two honeybear boards, 1 psu - I wasn't thinking and should've ordered two so I'm gonna order another, the soft start and speaker protection board), and am at a loss where to start. It seems that the amount of capacitance required for the PSU is dependent on the transformer that I've chosen as well as the type of speakers I plan on using with said amplifier. So here comes a bunch of questions (with I'm sure many more to follow)...

1) Using the Antek AN-8445, if I calculated correctly, will put out 63.64VDC - and although I notice that Jojo's build used the same transformer and 63V caps, I really should be using caps rated a bit higher - and finding 30mm 80v caps is getting to be difficult. Best I can find are 6800μF, 80v, 30mm Cornell Dubilier caps - so if I use 8 per board - is 54,400μF enough? Or am I still 'safe' using 63v caps with 10-12000μF?

----------------->

If you look at the AnTek web site for the 8445 SPEC, towards to the end :

Load Test (operation test):
TEST CONDITION: Input 120VAC 60Hz to the primary coils :
@ 0A, the output is 46.9V
@ 9A, the output is 45.6V

So during the quiet passage, your capacitor will take 1.414 * 46.9 = 66.31V
The 63V cap may or may not survive very long.

I am using Avel transformer and my output per rail is 137V/2= 68.5V during idle. In class B bias setting, you have almost no load.

2) For the speaker protection PCB I assume that the 12v secondary will be used, I will need 6v relay coils for K1 and K2. Is there a reason / advantage to using the 18v secondary and two 12v relay coils instead?

Any other ideas / suggestions? I plan on driving a pair of Paradigm Reference Studio 60 v.4s, and although they're relatively efficient at 91db, they really do like to suck back power - hence with the AN-8445 I'm really hoping to get as much out of this amp as possible!

Thanks for the help (any input is greatly appreciated!)

David
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Old 24th February 2013, 11:49 AM   #236
bkevin is offline bkevin  United Kingdom
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Wink Re : Is this the right amp for me?

[QUOTE=kclusa@yahoo.co;3382734]If you are trying to build an amp better than Arcam, your amp building skill is very critical. Please noted that the build guide gives you very good info of how to make it sound and how to make it stable.
However, it did not specify exactly what transistor combo and what capacitor combo to use. That will be up to your skill to fine tune the sound. The wiring choice also affect the sound.


Thanks for you reply Lou - noted. That much I do realise but I'm still willing to give it a go :-)


By the way, do you really need 250 W ?
Yes! I firmly believe there is no substitute for power and you can never have too much (judiciously used off course!).

When listening to the music at max volume that you ever use, can you monitor the output and see how much you are really using ?
I guess you mean can I measure how much current (power if you prefer) the amp is able to deliver when driven hard? Well no I can't and that kinda leads me back to my point. Your question got me thinking so I looked a little deeper into the specs for my amp and discovered that is rated at 100W into 8ohm but only 140W into 4 ohm (not 170 as I first thought). Does that tell you something? it sure did for me so I dug yet deeper and found that it uses a 280VA transformer wound to 35V with 10Kuf smoothing for each rail, driving both channels. I can't claim a whole lotta expertise but something tells me there's no way this amp can deliver nearly the power I need with such a small PSU. Don't get me wrong, I love my Arcam but In basic terms (and really testing my past, very dormant electronics skills) I think a Class B amp would need around 300VA PSU (absolute minimum!) per channel to deliver anything near 250W into 4ohm. Having worked that out, for the HB I guess I can calculate that with 35V rails it should be able to deliver 250W @4ohm providing the PSU can supply enough current - by my reckoning around 9A so at least a 800VA torridal if driving both channels. And with that I hope i've answered my own question :-) But anyone want to tell me I got this completely wrong please do! And help me out at the same time -ok ;-)
Thanks!
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Old 25th February 2013, 03:12 AM   #237
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Grossly approximate for class AB: VA*0.6=Watts
That is assuming 60% efficiency and most other factors disregarded.

But we might also want to look at audiometrics--"kclusa@yahoo.co" reduced bottleneck by upgrading nfb-shunt cap size for bigger deeper clearer high-resolution bass. He used a Panasonic FC 220u for C3 and an identical Panasonic FC 220u for C4, resulting in a super low loss 440u sized NFB-Shunt cap. This is twice as big and allows bigger lowest bass notes to get through the amp. You might also want to check your Arcam.
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Old 27th February 2013, 07:50 AM   #238
bkevin is offline bkevin  United Kingdom
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Default Taking the plunge

Hello everyone (is there really anyone out there?)
Iíve decided to go ahead with the build Ė wish me luck! One problem Iíve bumped into is matching Q10,11 and 12. Best I can get for Q10 is SA1381E but for Q11 &12 (and Q13) is SC3503D. In other words they canít be gain matched as far as I can see, or if they can it would be at a relatively lowly hfe of 100-120 (with a lot of luck thrown in finding matches!). I read that MJE340/350 could be a suitable alternative, and they seem to have a potentially better gain? Can anyone confirm or advise how to overcome this problem?
Many thanks in advance
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Old 28th February 2013, 12:46 PM   #239
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Default Re : Taking the plunge

Quote:
Originally Posted by bkevin View Post
Hello everyone (is there really anyone out there?)
Iíve decided to go ahead with the build Ė wish me luck! One problem Iíve bumped into is matching Q10,11 and 12. Best I can get for Q10 is SA1381E but for Q11 &12 (and Q13) is SC3503D. In other words they canít be gain matched as far as I can see, or if they can it would be at a relatively lowly hfe of 100-120 (with a lot of luck thrown in finding matches!). I read that MJE340/350 could be a suitable alternative, and they seem to have a potentially better gain? Can anyone confirm or advise how to overcome this problem?
Many thanks in advance
I don't do match at all.
How do you perform match ?
Hfe changes on bias, temperature and even frequency.
If you are using the hfe function on simple DMM, That only match one point at that temperature at that current.

Lou
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Old 28th February 2013, 02:57 PM   #240
bkevin is offline bkevin  United Kingdom
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Quote:
Originally Posted by kclusa@yahoo.co View Post
I don't do match at all.
How do you perform match ?
Hfe changes on bias, temperature and even frequency.
If you are using the hfe function on simple DMM, That only match one point at that temperature at that current.

Lou
Well thatís one way of overcoming the problem I suppose. I canít do much better than a simple DMM test, but to my mind if they at least match at the same temp and current thereís a better chance they will match later on, and hopefully better than no matching at all. The point I was making and hence my request for help is that SA1381E is a different gain rating to SC3503D. In other words the gain match is inherently bad to begin with.
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