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
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
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
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
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
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
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 eindtrap.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.
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 eindtrap.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.
Hi, you will find everything here: Philips AG9015 | Philips AG9015 AG9018 tube amplifier modification tuning
Hi BigBulb,
See page 86 of this book: http://www.introni.it/pdf/Rodenhuis%20-%20HiFi%20Circuits.pdf
The AG9015 does not contain the AD9025 double chokes as mentioned in the book but the specifications of the choke windings in the AG9015 probably come close to that of the AD9025 double choke.
If you want to build your amplifier as a pure otl amplifier, you could wind, of have somebody wind, the double chokes according to the specifications in the book. Or try to get your hands on two AD9025's.
Greetings,
Robert
See page 86 of this book: http://www.introni.it/pdf/Rodenhuis%20-%20HiFi%20Circuits.pdf
The AG9015 does not contain the AD9025 double chokes as mentioned in the book but the specifications of the choke windings in the AG9015 probably come close to that of the AD9025 double choke.
If you want to build your amplifier as a pure otl amplifier, you could wind, of have somebody wind, the double chokes according to the specifications in the book. Or try to get your hands on two AD9025's.
Greetings,
Robert
Several Rodenhuis book's schematics are pulled straight from Philips DIY kits (bouwdozen) . As example, the 3W ECL86 amplifier described at page 37 is almost exactly identical to the Philips V30S bouwdozen. The EL86 schematic at page 86 is the same as the Philips HF303 bouwdozen. Each Philips kits had a complete building guide with component drawings and detailed explanations - a dutch equivalent of Heathkit. I believe that Philips only sold bouwdozen on the domestic market, because I never found any of them on sale in Italy or Germany and the language is dutch only. This is the only building guide I have managed to found: http://uk.filejumble.com/HF302.pdf
It is the HF302 kit, basically the 2xEL86 power stage paired with a preamp section. This is the 1965 Philips lineup for DIY Hi-Fi amplifiers: http://uk.filejumble.com/Bouwdozen_voor_HiFi.pdf . It is a partial list, and it does not lists the earlier products such as the V30S amplifier. I am very interested on the building guides; I hope that someone here could find more of them. They seems to be a high quality job. I have built a V30S clone (with a different output transformer and no tone controls) and it works just fine.
The suggestion about the purchase of a used AG9014 / AG9015 / AG9018 would have been spot-on for the original poster (it does non seems to post anymore on this forum). Today, 15 years later, working amplifiers have collector prices well above the components cost.
It is the HF302 kit, basically the 2xEL86 power stage paired with a preamp section. This is the 1965 Philips lineup for DIY Hi-Fi amplifiers: http://uk.filejumble.com/Bouwdozen_voor_HiFi.pdf . It is a partial list, and it does not lists the earlier products such as the V30S amplifier. I am very interested on the building guides; I hope that someone here could find more of them. They seems to be a high quality job. I have built a V30S clone (with a different output transformer and no tone controls) and it works just fine.
The suggestion about the purchase of a used AG9014 / AG9015 / AG9018 would have been spot-on for the original poster (it does non seems to post anymore on this forum). Today, 15 years later, working amplifiers have collector prices well above the components cost.
Interesting material, thanks. As side note, a stereo 800 ohm EL86 OTL amplifier, paired wit two 12 inches 800 ohm full range speakers rated up to 15 KHz, is built inside the second generation of Philips Philicorda home electronic organs (the one with two manuals and built-in pedals), such as 22BM755. I often see them listed at trift stores as "parts or repair" because the transistorized tone generator goes bad, at 100 euro or less.
Everything here Philips AG9015 | Everything about it
Check Rodenhuis book, about the transformer: Found.it interesting, thatbthe design is "experimental"
Check Rodenhuis book, about the transformer: Found.it interesting, thatbthe design is "experimental"
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