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Interesting Audio circuits

 
Nuvistor
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I found this about Single Ended Push pull amplifiers in a Philips publication, not had chance to study it properly but looks an interesting read.

https://americanradiohistory.com/Archive-Philips-Technical-Review/50s/Philips-Technical-Review-1957.pdf

Is about page 42 in a 360 page document, about 10 pages in length, there are lots of other topics in the document.

 

 

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Topic starter Posted : 29/11/2019 4:05 pm
PYE625 and ntscuser liked
Sundog
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Philips used the EL86 arrangement shown in fig. 3 with their own high impedance loudspeakers.

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Posted : 22/11/2021 4:06 pm
sideband
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Yes Philips seemed to like this arrangement. I had the pleasure of restoring one of their 'Bi-Ampli' radio's some years ago...the first time I had actually seen one in the flesh so to speak. The one I did had an EL84 and EL86, the EL86 being the 'top' valve and designed for this circuit having a high heater/cathode insulation since the cathode was at roughly half HT. There have been numerous variations and one I've seen is a record player using an EL84 and a UL84, the UL84 being the 'top' valve again because of the high heater/cathode insulation required. Another variation used PL81's.....! Seemed to be much more popular with their continental designs.

The thing is, they all sounded superb.

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Posted : 22/11/2021 10:35 pm
Nuvistor
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@sideband 

Philips designed some interesting circuits that went against what was considered  standard practice but usually worked extremely well. 

 

 

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Topic starter Posted : 23/11/2021 9:13 am
ntscuser
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Our German-built Philips radio had a strange arrangement of a forward facing woofer and upward facing tweeter fed by a separate transformer. I only know that because a circuit-diagram was sellotaped to the inside of the rear cover.

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Posted : 24/11/2021 6:32 am