transformer for Philips AG9015

bigbulb · 20th November 2005, 07:34 AM

Greetings!

I wanted to build Philips AG9015 SEPP OTL amplifier. By quick search on google, I only manage to get the manual with schematic, but without any choke/ transformer infomation.

Someone says the ratio is 1:1:1 between two g2 choke and the output matching trans and 60-Henry.

IMHO, the choke can't be 60 Henry if the ratio is 1:1:1, The load is 800ohm for the primary, and we only need 6.36 Henry to get down to 20Hz of frequency response by calculation, and that small trannies can't get that high inductance I think.

Anyone have more info about this transformer? I need to know the inductance of the g2 choke, and also the DC resistance if possible, I can wind my own transformer but need the infomation about it.

Regards,
BigBulb

dhaen · 20th November 2005, 08:47 AM

Here's a link to the schematic :
AG9015

bigbulb · 20th November 2005, 08:51 AM

Hi,

Yeah Thanks for the link, I have that copy of manual+ schematic, I need the transformer info so that I can build a clone version

Thanks,
BigBulb

honinbou · 27th April 2006, 06:13 AM

That double choke you are talking about:

On my Philips AG9014: it's a 1:1 EI choke, no air gap. 3rd coil on the secondary of the choke measured ~69 ohms if memory serves and parallels with the 800 ohm speaker.

I used to own a 9015 too. The amp has a C core 1:1 choke, 1 coil paralleling with the 800 ohm speaker + 1 autotransformer for 8/16 ohm speakers. At that time I don't have 800 ohm speakers. And that amp was really terrible with my 8 ohm speakers.

I recommend you clone the Philips HF303 instead, an 800 ohm power amplifier using EL86s and a double choke. The power amp portion of my AG9014 is ok but the preamp portion is really bad - those who own one the 9014, 9015, or 9018 would know the noise level of the PU section is absolutely pathetic.

Off topic: For the 9014, one way to get the highs back is to get rid of the coil paralleling the 800 ohm speaker. This mod might also work with the 9015 and 9018.

honinbou

max29 · 18th May 2008, 08:04 PM

Off topic: For the 9014, one way to get the highs back is to get rid of the coil paralleling the 800 ohm speaker. This mod might also work with the 9015 and 9018.

Have a 9015 Like the soun but as you said the highs are really poor.

Can i just desolder the wiring to coil paralelling the 800ohm sp.
Have 8 ohm speakers on them

Must be a reason mid- and low-freq. is pure in sound but highs are poor.

Thanks

honinbou · 7th June 2008, 07:19 AM

do this at your own risk...

on my 9014 that winding was part of the protection circuit for overheated 800 ohm speakers. in 9015/9018 I think that coil was part of the 800 ohm:8/16 ohm transformer. But S7-S8 could be an autotransformer winding... and if it's the latter then you strike gold...

Well you could try to open up you 9015/9018 then detach the wire from tag of coil S5 (connected to 100uF blocking capacitors or pin 2 of the 800 ohm speaker). Leave the tag connected to ground as is. see this schematic for details: http://welther.nl/hugo/fotos/ag9018%20eindtrap.JPG. If there is no sound then sorry the 9014 mod could not work on later models.

Also you could get more high notes back when you disable the built in loudness control. This could be done by simply detaching the capacitor and the resistor from the loudness tap on the volume control.

If you don't like the sound you could solder the wires back.

Let me know how it goes.

20th November 2005, 07:34 AM	#1
bigbulb diyAudio Member Join Date: Aug 2004 Location: klamazoo	transformer for Philips AG9015 Greetings! I wanted to build Philips AG9015 SEPP OTL amplifier. By quick search on google, I only manage to get the manual with schematic, but without any choke/ transformer infomation. Someone says the ratio is 1:1:1 between two g2 choke and the output matching trans and 60-Henry. IMHO, the choke can't be 60 Henry if the ratio is 1:1:1, The load is 800ohm for the primary, and we only need 6.36 Henry to get down to 20Hz of frequency response by calculation, and that small trannies can't get that high inductance I think. Anyone have more info about this transformer? I need to know the inductance of the g2 choke, and also the DC resistance if possible, I can wind my own transformer but need the infomation about it. Regards, BigBulb

18th May 2008, 08:04 PM	#5
max29 diyAudio Member Join Date: Nov 2005 Location: oosterhout	get the high frequencies btter Off topic: For the 9014, one way to get the highs back is to get rid of the coil paralleling the 800 ohm speaker. This mod might also work with the 9015 and 9018. Have a 9015 Like the soun but as you said the highs are really poor. Can i just desolder the wiring to coil paralelling the 800ohm sp. Have 8 ohm speakers on them Must be a reason mid- and low-freq. is pure in sound but highs are poor. Thanks

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20th November 2005, 08:47 AM	#2
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	Here's a link to the schematic : AG9015

20th November 2005, 08:51 AM	#3
bigbulb diyAudio Member Join Date: Aug 2004 Location: klamazoo	Hi, Yeah Thanks for the link, I have that copy of manual+ schematic, I need the transformer info so that I can build a clone version Thanks, BigBulb

27th April 2006, 06:13 AM	#4
honinbou diyAudio Member Join Date: Oct 2004	That double choke you are talking about: On my Philips AG9014: it's a 1:1 EI choke, no air gap. 3rd coil on the secondary of the choke measured ~69 ohms if memory serves and parallels with the 800 ohm speaker. I used to own a 9015 too. The amp has a C core 1:1 choke, 1 coil paralleling with the 800 ohm speaker + 1 autotransformer for 8/16 ohm speakers. At that time I don't have 800 ohm speakers. And that amp was really terrible with my 8 ohm speakers. I recommend you clone the Philips HF303 instead, an 800 ohm power amplifier using EL86s and a double choke. The power amp portion of my AG9014 is ok but the preamp portion is really bad - those who own one the 9014, 9015, or 9018 would know the noise level of the PU section is absolutely pathetic. Off topic: For the 9014, one way to get the highs back is to get rid of the coil paralleling the 800 ohm speaker. This mod might also work with the 9015 and 9018. honinbou

7th June 2008, 07:19 AM	#6
honinbou diyAudio Member Join Date: Oct 2004	do this at your own risk... on my 9014 that winding was part of the protection circuit for overheated 800 ohm speakers. in 9015/9018 I think that coil was part of the 800 ohm:8/16 ohm transformer. But S7-S8 could be an autotransformer winding... and if it's the latter then you strike gold... Well you could try to open up you 9015/9018 then detach the wire from tag of coil S5 (connected to 100uF blocking capacitors or pin 2 of the 800 ohm speaker). Leave the tag connected to ground as is. see this schematic for details: http://welther.nl/hugo/fotos/ag9018%20eindtrap.JPG. If there is no sound then sorry the 9014 mod could not work on later models. Also you could get more high notes back when you disable the built in loudness control. This could be done by simply detaching the capacitor and the resistor from the loudness tap on the volume control. If you don't like the sound you could solder the wires back. Let me know how it goes.

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