Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Instruments and Amps Everything that makes music, Especially including instrument amps.

Behringer A500 as a DIY project
Behringer A500 as a DIY project
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th November 2019, 07:55 PM   #221
Turbowatch2 is offline Turbowatch2  Germany
diyAudio Member
 
Join Date: Aug 2013
Location: Northern germany
Many amps are made this way. In this case, by using the RCA, you would make the signal pass one OP-amp stage less. Probably you will not hear this, if you do and it is not due to a different level, it might just as well be the coupling 50uF capacitor. These are a cheap solution and any modder would change them at first sight. But adding some 4700uF caps to the power supply should have a more audible impact, IMO, if the amp is used full range or for bass reproduction. 3300uF seem a bit on the lean side for an amp with more than 100 Watt.
  Reply With Quote
Old 7th November 2019, 08:14 AM   #222
ginetto61 is offline ginetto61  Italy
diyAudio Member
 
Join Date: Sep 2009
Location: Milano
Quote:
Originally Posted by Turbowatch2 View Post
Many amps are made this way. In this case, by using the RCA, you would make the signal pass one OP-amp stage less. Probably you will not hear this, if you do and it is not due to a different level, it might just as well be the coupling 50uF capacitor. These are a cheap solution and any modder would change them at first sight
Thanks for the very valuable advice. Do you think that some electrolytics can be tolerated also in series with the signal ? i read somewhere that at Millennia they use to put small plastic caps in parallel with bigger electrolytics in their mic preamps ... and they preamps are top notch from what i understand.
Even a 10uF plastic is big ... and the better the quality the bigger it is.

Quote:
But adding some 4700uF caps to the power supply should have a more audible impact, IMO, if the amp is used full range or for bass reproduction.
3300uF seem a bit on the lean side for an amp with more than 100 Watt
thanks and yes ... that i have noticed also myself and i have to check the space but i could try even to place 10mF parts if space allows
I am a fan of very big caps ... they are like the lungs for a human
I have done some silly recapping in the past on old amps ... i am in the camp that the more uF the better Of course i needed to replace the diodes in the bridge with some monster bridge. And i used big cables as well.
Often especially with cheap amps i have the feeling that both uF and quality of the ps caps is very suspicious and inadequate. And the transformer as well.
Another thing i noticed is that they leave very little space to increase uF ... like they put constraints for modding
__________________
“Without music, life would be a mistake” ― Friedrich Nietzsche

Last edited by ginetto61; 7th November 2019 at 08:17 AM.
  Reply With Quote
Old 8th November 2019, 12:58 AM   #223
wg_ski is online now wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
The required capacitance has little to do with the amplifier wattage. It has to do with the load impedance. 10,000 uf caps on each channel would be about right for an amplifier capable of 4 ohms. To go down to 2 ohms you need to double it, for 8 ohms only you might get away with half (which would be 10,000 uf for both channels combined - about the minimum you see for any “real” amplifier). To really belt out the bass you would run enough capacitance for 2 ohms, but run your load higher to keep that voltage stiff. But you really don’t want to go much higher. Going a lot larger (say 100,000 uf) is bad too, for other reasons.
  Reply With Quote
Old 8th November 2019, 07:31 AM   #224
ginetto61 is offline ginetto61  Italy
diyAudio Member
 
Join Date: Sep 2009
Location: Milano
Quote:
Originally Posted by wg_ski View Post
The required capacitance has little to do with the amplifier wattage. It has to do with the load impedance. 10,000 uf caps on each channel would be about right for an amplifier capable of 4 ohms. To go down to 2 ohms you need to double it, for 8 ohms only you might get away with half (which would be 10,000 uf for both channels combined - about the minimum you see for any “real” amplifier). To really belt out the bass you would run enough capacitance for 2 ohms, but run your load higher to keep that voltage stiff. But you really don’t want to go much higher.
Thank you for the very useful advice. Looking at amps i see 4700uF/rail*channel a very common value. Personally i like 10,000uF but this usually fights with space available on board to place bigger caps. It seems that manufacturers do no like the idea ... i wonder why they space parts so closely ... weird It is not a personal computer ... it is a power amp
In power amps i would love to see high section cables for the high current paths Even in power transistors i would like to see bigger pins for power supply and output than input signal In the end Ohm law is valid also for power amp from what i understand

Quote:
Going a lot larger (say 100,000 uf) is bad too, for other reasons.
So indeed there can be issues with too large capacitance in the power supply ? this i do not understand. Could you elaborate please ?
Better ... is there an optimal value for capacitance in a power supply ? a formula to calculate that ?
__________________
“Without music, life would be a mistake” ― Friedrich Nietzsche
  Reply With Quote
Old 8th November 2019, 11:06 AM   #225
wg_ski is online now wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
The bigger the capacitor, the higher the RMS secondary current, fir a given DC load. Power factor due to harmonics gets progressively worse (and so do turn-on surges). The only question is where you cry ‘uncle’ and stop. And after it gets big enough there is little benefit anyway.

As to an optimum value, the power supply cap and load impedance form a low frequency pole, just as if you had an output coupling cap. It is inside the feedback, so it is of little consequence closed-loop. But you lose power capability if the pole frequency is too high. And you get poor clipping behavior at low frequencies to boot. You want that pole frequency to be lower than the one created by your input coupling cap. How low do you want? Single digit Hz for sure. And remember the load impedance is both channels in parallel, and the caps are in series across the supply. 10,000 uf and 4 ohms is effectively 8 Hz when you look at the total series parallel circuit.
  Reply With Quote
Old 11th November 2019, 10:32 AM   #226
ginetto61 is offline ginetto61  Italy
diyAudio Member
 
Join Date: Sep 2009
Location: Milano
Quote:
Originally Posted by wg_ski View Post
The bigger the capacitor, the higher the RMS secondary current, fir a given DC load. Power factor due to harmonics gets progressively worse (and so do turn-on surges). The only question is where you cry ‘uncle’ and stop. And after it gets big enough there is little benefit anyway.
Hi thanks and that is a good news because big and high grade caps are insanely expensive Probably some specific applications need them

Quote:
As to an optimum value, the power supply cap and load impedance form a low frequency pole, just as if you had an output coupling cap. It is inside the feedback, so it is of little consequence closed-loop. But you lose power capability if the pole frequency is too high. And you get poor clipping behavior at low frequencies to boot. You want that pole frequency to be lower than the one created by your input coupling cap. How low do you want? Single digit Hz for sure. And remember the load impedance is both channels in parallel, and the caps are in series across the supply.
10,000 uf and 4 ohms is effectively 8 Hz when you look at the total series parallel circuit
this is very technical and i am not sure to get it right. However i will keep the value of 10mF/channel rail in mind. That would be 20mF per two when feeding both channels ... good ! thank you very much again.
__________________
“Without music, life would be a mistake” ― Friedrich Nietzsche
  Reply With Quote

Reply


Behringer A500 as a DIY projectHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Behringer A500 power amp problem, please help? emperor Instruments and Amps 37 25th August 2015 07:56 PM
Upgrading Behringer BCD2000 project, need help/advice Bonthouse Parts 4 15th July 2011 11:20 PM
Phonic Max250 or Behringer A500 for speakers 93db?? Brit01 Instruments and Amps 13 29th July 2008 08:54 PM
Which soundcard for KX Project and measuring speakers with a Behringer ECM8000? mazeroth Multi-Way 1 28th March 2006 09:22 AM


New To Site? Need Help?

All times are GMT. The time now is 12:15 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki