My new amplifier

Paco · 8th November 2005, 05:23 PM

Hi all,

I finished my new amp and preamp a couple of weeks ago. It’s a 250W single ended mosfet design (not my design). It took me more than two months to finish the amp, since I started sourcing the parts, thinking about how to build the housing and asking the designer how to implement it until I finally had music from it! I’m very happy with the results!

I wanted a high power amplifier that was able to move my 3 way loudspeakers, and a partner top quality preamplifier. I decided to use monophonic high quality PSUs in both the power amplifier and the preamplifier. RCA are WBT NextGen AG and the binding posts are made of gold platted pure copper.

Each channel PSU consist in a 1000VA 50+50V toroidal transformer, 6 Mundorf Mlytic-HC 47000uF caps and one rectifier bridge made with 12 IR HFA15TB60 HEXFREDs in a custom made PCB (I had to triplicate the diodes because with such large capacitors banks –about 0.3F per channel- and due to their very low impedance, even double could explode). You can here some photos.
Regards,
Paco

darkfenriz · 8th November 2005, 07:23 PM

Very nice !!
I especially like 4th photo. Your fireplace gives not enough heat ?
cheers

Paco · 9th November 2005, 06:21 AM

Well, in fact the fireplace here in Cordoba useless during most of the year. Right now we have about 15ºC and during the day we will reach 25ºC. With those temperatures the heatsinks of my amp are enought to keep the house warm, they reach about 50ºC after 3-4 hours of work

Upupa Epops · 9th November 2005, 06:37 AM

Paco, diodes in rectifier are in parallel ?

Paco · 9th November 2005, 07:28 AM

Hi Upupa Epops. Yes, they are: 3 units paralleled, each one with a smoothing capacitor.

Upupa Epops · 9th November 2005, 07:53 AM

You have any equalization of current by each diode ? They haven't quite the same characteristic in forward direction....

Paco · 9th November 2005, 10:12 AM

Quote:

You have any equalization of current by each diode ? They haven't quite the same characteristic in forward direction....

None at all. I've measured +71,3V in one channel and +71.4 in the other. I don't know if the effect that you mention could be audible in some way but I haven't heard anything strange.
Regards,
Paco

Christer · 9th November 2005, 10:22 AM

What Upupa means is that you cannot just parallel diodes and hope that they will share the current equally. Diodes are individuals and their characteristics will differ. That means that one diode may take almost all the current, and you gained nothing from using three diodes instead of one. Maybe it could work if you match the diodes very closely, but I don't know if that would be safe either. Perhaps one could use small resistors in series with each diode, but I have never seen that solution. Perhaps Upupa has some magic trick?

Upupa Epops · 9th November 2005, 10:25 AM

It is different problem, Paco. I am talking about correct ( the same ) current by each parallel diode. By this simply connection isn't the same....

Upupa Epops · 9th November 2005, 10:28 AM

Trick not exist, only serial resistors with each diode...

8th November 2005, 05:23 PM	#1
Paco diyAudio Member Join Date: Aug 2003 Location: Cordoba	My new amplifier Hi all, I finished my new amp and preamp a couple of weeks ago. It’s a 250W single ended mosfet design (not my design). It took me more than two months to finish the amp, since I started sourcing the parts, thinking about how to build the housing and asking the designer how to implement it until I finally had music from it! I’m very happy with the results! I wanted a high power amplifier that was able to move my 3 way loudspeakers, and a partner top quality preamplifier. I decided to use monophonic high quality PSUs in both the power amplifier and the preamplifier. RCA are WBT NextGen AG and the binding posts are made of gold platted pure copper. Each channel PSU consist in a 1000VA 50+50V toroidal transformer, 6 Mundorf Mlytic-HC 47000uF caps and one rectifier bridge made with 12 IR HFA15TB60 HEXFREDs in a custom made PCB (I had to triplicate the diodes because with such large capacitors banks –about 0.3F per channel- and due to their very low impedance, even double could explode). You can here some photos. Regards, Paco

9th November 2005, 06:21 AM	#3
Paco diyAudio Member Join Date: Aug 2003 Location: Cordoba	Fireplace Well, in fact the fireplace here in Cordoba useless during most of the year. Right now we have about 15ºC and during the day we will reach 25ºC. With those temperatures the heatsinks of my amp are enought to keep the house warm, they reach about 50ºC after 3-4 hours of work

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8th November 2005, 07:23 PM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	Very nice !! I especially like 4th photo. Your fireplace gives not enough heat ? cheers

9th November 2005, 06:37 AM	#4
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Paco, diodes in rectifier are in parallel ?

9th November 2005, 07:28 AM	#5
Paco diyAudio Member Join Date: Aug 2003 Location: Cordoba	Hi Upupa Epops. Yes, they are: 3 units paralleled, each one with a smoothing capacitor.

9th November 2005, 07:53 AM	#6
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	You have any equalization of current by each diode ? They haven't quite the same characteristic in forward direction....

9th November 2005, 10:22 AM	#8
Christer diyAudio Member Join Date: Sep 2002 Location: Sweden	What Upupa means is that you cannot just parallel diodes and hope that they will share the current equally. Diodes are individuals and their characteristics will differ. That means that one diode may take almost all the current, and you gained nothing from using three diodes instead of one. Maybe it could work if you match the diodes very closely, but I don't know if that would be safe either. Perhaps one could use small resistors in series with each diode, but I have never seen that solution. Perhaps Upupa has some magic trick?

9th November 2005, 10:25 AM	#9
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	It is different problem, Paco. I am talking about correct ( the same ) current by each parallel diode. By this simply connection isn't the same....

9th November 2005, 10:28 AM	#10
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Trick not exist, only serial resistors with each diode...

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