AudioSector-chip amp kits, dacs, chassis - Page 77 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Audio Sector

Audio Sector Kits & PC boards from AudioSector

Reply
 
Thread Tools Search this Thread
Old 8th February 2006, 07:21 PM   #761
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Yes, it seems to be correct.

You will usually get more on secondaries than specified, as the rating includes regulation margin and the voltage is given for maximum current draw, which when you masure is not applied. Also, you need to allow for mains voltage fluctuation.

The voltage you are currently getting from transformers is still within limits for LM4780 chip.
__________________
www.audiosector.com
Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it. - JC
  Reply With Quote
Old 8th February 2006, 07:31 PM   #762
diyAudio Member
 
Join Date: Jan 2004
Location: Terengganu, Malaysia
Send a message via AIM to safetyman Send a message via MSN to safetyman Send a message via Yahoo to safetyman
Quote:
Originally posted by Peter Daniel
Yes, it seems to be correct.

You will usually get more on secondaries than specified, as the rating includes regulation margin and the voltage is given for maximum current draw, which when you masure is not applied. Also, you need to allow for mains voltage fluctuation.

The voltage you are currently getting from transformers is still within limits for LM4780 chip.
Thanks Peter, I am relieved and more confident now. How do I look for the voltage to work with in the LM4780 datasheet? I mean which is the section that has this information?
__________________
Shehzad
Aleph 3 - Diehard fan
  Reply With Quote
Old 8th February 2006, 07:55 PM   #763
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
That would be:

Operating Ratings (Notes 1, 2)
Supply Voltage |V+| + | | 20V VTOTAL 84V

http://www.national.com/ds/LM/LM4780.pdf
__________________
www.audiosector.com
Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it. - JC
  Reply With Quote
Old 9th February 2006, 06:20 AM   #764
diyAudio Member
 
Join Date: Jan 2004
Location: Terengganu, Malaysia
Send a message via AIM to safetyman Send a message via MSN to safetyman Send a message via Yahoo to safetyman
Quote:
Originally posted by Peter Daniel
That would be:

Operating Ratings (Notes 1, 2)
Supply Voltage |V+| + | | 20V VTOTAL 84V

http://www.national.com/ds/LM/LM4780.pdf
Peter, does this mean I am operating at very close to the max allowable?

Are there any downside to this? Like I need a bigger heatsink or something? I am deliberating to mount each chip to the side of the amp wall which is a flat piece of aluminium 0.5" thick and 4" in height and about 10" long. One side is exposed to the ambient but has no fins. Would this be good enough?

Thanks.
__________________
Shehzad
Aleph 3 - Diehard fan
  Reply With Quote
Old 9th February 2006, 06:45 AM   #765
karma is offline karma  Canada
diyAudio Member
 
karma's Avatar
 
Join Date: Feb 2003
Location: hamilton,ontario
you making a toaster oven


ya 84v is the maximum im runing half that and my amp gets hot.


|V+|+|V-| = 80V
Supply Voltage |V+|+|V-| 20V = VTOTAL = 84V

Differential Input Voltage (Note 13) 60V

Output Current Internally Limited
Power Dissipation (Note 3) 125W Note: Operation is guaranteed up to 84V; however, distortion
may be introduced from SPiKe protection circuitry if

ESD Susceptability (Note 4) 3.0kV

proper thermal considerations are not taken into account.
ESD Susceptability (Note 5) 200V Refer to the Thermal Considerations section for more
Junction Temperature (TJMAX) (Note 9) 150C information.
Attached Images
File Type: jpg mvc-164s.jpg (55.8 KB, 1248 views)
  Reply With Quote
Old 9th February 2006, 09:53 AM   #766
sangram is offline sangram  India
diyAudio Member
 
Join Date: Sep 2002
Location: India
I don't think the chips will work properly with such low heatsinking, even if you are within the normal limits for voltage. I have my 4780s mounted to 5" Alu profile of 4 mm thickness and flower finning and extrusion. I estimate around 1.5 C/W for the heatsinks, and they do get quite toasty. Not enough to burn but not comfortable to hold. I'd say around 60 degrees C. And my DC voltage is just 32 volts (22VAC oversized transformers so as to not sag under load).

You should be fine with the voltages though, as long as your load is around 8 ohms. I'd say you drop a volt or two once you load up the secondary, and you should get a DC voltage of about 37-38 Volts per rail. Though high, it should be OK.

But you definitely need better heatsinking. 0.5" Aluminium is definitely too slim of a margin (pun intended). At best Spike circuitry may cut in in a few minutes.
  Reply With Quote
Old 9th February 2006, 03:53 PM   #767
diyAudio Member
 
Join Date: Jan 2004
Location: Terengganu, Malaysia
Send a message via AIM to safetyman Send a message via MSN to safetyman Send a message via Yahoo to safetyman
Quote:
Originally posted by karma
you making a toaster oven


ya 84v is the maximum im runing half that and my amp gets hot.


|V+|+|V-| = 80V
Supply Voltage |V+|+|V-| 20V = VTOTAL = 84V

Differential Input Voltage (Note 13) 60V

Output Current Internally Limited
Power Dissipation (Note 3) 125W Note: Operation is guaranteed up to 84V; however, distortion
may be introduced from SPiKe protection circuitry if

ESD Susceptability (Note 4) 3.0kV

proper thermal considerations are not taken into account.
ESD Susceptability (Note 5) 200V Refer to the Thermal Considerations section for more
Junction Temperature (TJMAX) (Note 9) 150C information.
karma, the problem is that the torroids available here have either 18V secondaries or 25V secondaries. !@#$ Don't tell me I wasted 2 new transformers.


Quote:
Originally posted by sangram
I don't think the chips will work properly with such low heatsinking, even if you are within the normal limits for voltage. I have my 4780s mounted to 5" Alu profile of 4 mm thickness and flower finning and extrusion. I estimate around 1.5 C/W for the heatsinks, and they do get quite toasty. Not enough to burn but not comfortable to hold. I'd say around 60 degrees C. And my DC voltage is just 32 volts (22VAC oversized transformers so as to not sag under load).

You should be fine with the voltages though, as long as your load is around 8 ohms. I'd say you drop a volt or two once you load up the secondary, and you should get a DC voltage of about 37-38 Volts per rail. Though high, it should be OK.

But you definitely need better heatsinking. 0.5" Aluminium is definitely too slim of a margin (pun intended). At best Spike circuitry may cut in in a few minutes.
What if I attach fins to outside of the 2 flat side panels? Would that work? This LM4780 is in a parallel configuration? And BTW, what value resistors do you use to place across the output during the running in period?

Thanks guys.........Opinion most welcome.
__________________
Shehzad
Aleph 3 - Diehard fan
  Reply With Quote
Old 9th February 2006, 07:44 PM   #768
diyAudio Member
 
Join Date: Dec 2005
Location: italy
Send a message via MSN to mcamolin
Hi Peter, you think work fine your kit dual mono xlm3875x with a transformer x300VAx that have secondaries 25 0 25.
Thanks
  Reply With Quote
Old 9th February 2006, 08:20 PM   #769
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
2 x 25V, 300VA transformer will work fine (providing the speakers are easy load). It is my observation that the higher the voltage, the better the sound.

If amp runs too hot, just encrease the heatsinks (adding fins is fine), but even temperatures of 50-60 deg C are OK (Yes the chip amp can run that hot if pushed).
__________________
www.audiosector.com
Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it. - JC
  Reply With Quote
Old 10th February 2006, 05:22 AM   #770
diyAudio Member
 
Join Date: Jan 2004
Location: Terengganu, Malaysia
Send a message via AIM to safetyman Send a message via MSN to safetyman Send a message via Yahoo to safetyman
Quote:
Originally posted by Peter Daniel
2 x 25V, 300VA transformer will work fine (providing the speakers are easy load). It is my observation that the higher the voltage, the better the sound.

If amp runs too hot, just encrease the heatsinks (adding fins is fine), but even temperatures of 50-60 deg C are OK (Yes the chip amp can run that hot if pushed).
Peter, thanks for your response. Actually, my casing will be aluminum on all 4 sides. The left and right side where the amp is going to be attached to is 4" (H) X 8.5" (D) X 0.5" (thick), and the front and back is 4" (H) X 11.5" (W) X 0.25" (thick). I would rather not add fins if possible. The bottom will be a piece of wood off a nice chopping board and to show your beautiful PCB, the top will probably be acrylic.

My speakers are a pair of Epos ES11 which I believe they are about 87-88 dB sensitivity. No idea on impedance though, but I guess it will depend on the music played too.
__________________
Shehzad
Aleph 3 - Diehard fan
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 02:49 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2