Excellent work, proud of you my man.
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Show posts MenuQuote from: phatt on January 15, 2009, 09:31:52 AMQuote from: Boprikov on January 15, 2009, 05:32:52 AM
http://www.vintagehofner.co.uk/selmer/schematic/ssmerc.html
This is an interesting vintage design. If i understand correctly, the primary of the output transformer must stand 400 mA. I have no idea what the impedance ratio should be. Is it possible to somehow estimate it? And what should the power supply voltage be? I think 10-20 Volts is not enough as efficiency is poor in class A.
Sorry my english... but i´m quite interested about what type of output transformer was used at those SS Selmers.
Is that a "70V" line transformer? You think about 400ma bias idle current is through primary? That is about 30w to dissipate at idle with 35v supply.
Hi Boprikov,
I searched years back trying to find such a circuit and you found one,, Good find.
Here is one I built some years back similar in concept to Selmer Mercury.
I never went on to complete it because of the bass issue but insanely loud even though it was driving a small 100mm speaker.
I have no idea where the OT came from, just found it in some trash.
The output Tr has to be a fairly high voltage as the collector voltage can get quite high when using transformer coupling.
Q3 only needs a clip-on heat sink as it only runs lukewarm.
Jfetter, I do wonder about Exotic transistors and all that heat ,, my thoughts are go with transfomer coupling as it puts a lot less heat into the Amp,,heck line transformers are easy found. Teemu is on the mark there,,
just my take on it.
Phil, Nambour Australia
Quote from: dsmnoisemaker on January 22, 2009, 01:48:55 PMQuote from: jfetter on January 22, 2009, 11:42:59 AM
I attempted to use them but found they were difficult to obtain. They also did not seem stable as far as future availability.
Well here in chile seems to be plenty of them and they are pretty cheap..in fact LM3886/4780 are very hard to get, and they cost the same or more than a STK chip of the same power..
It seems that the main reason for not using STK is availability..and not quality..but i´m not planning to make them massively..just 1 or 2 of them..
Quote from: dsmnoisemaker on January 22, 2009, 01:48:55 PMQuote from: jfetter on January 22, 2009, 11:42:59 AM
I attempted to use them but found they were difficult to obtain. They also did not seem stable as far as future availability.
Well here in chile seems to be plenty of them and they are pretty cheap..in fact LM3886/4780 are very hard to get, and they cost the same or more than a STK chip of the same power..
It seems that the main reason for not using STK is availability..and not quality..but i´m not planning to make them massively..just 1 or 2 of them..
Quote from: Boprikov on January 15, 2009, 05:32:52 AM
http://www.vintagehofner.co.uk/selmer/schematic/ssmerc.html
This is an interesting vintage design. If i understand correctly, the primary of the output transformer must stand 400 mA. I have no idea what the impedance ratio should be. Is it possible to somehow estimate it? And what should the power supply voltage be? I think 10-20 Volts is not enough as efficiency is poor in class A.
Sorry my english... but i´m quite interested about what type of output transformer was used at those SS Selmers.