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bikerhifinut · 25th Oct 2015, 9:33 pm

I don't know how they were cut, The chassis were spotted at the February audiojumble in Tonbridge by a friend and kindly bought and stored for me.(thanks terry

) If anybody knows who the guy was I would be grateful. They had all the holes cut that I needed.
The transformers are Danburys, obtained from another contact on an audio forum. Pretty much the set that's still marketed for the 5-20 circuit. The mains transformer has enough reserve to run a 5U4 rectifier, this was confirmed by Danbury themselves when i spoke on the phone. The caveat is to reduce the 6.3 draw by an amp, this isnt a problem as its a 5A s winding and a couple of EL34n ECC81 and an EF86/40 draw a total of 3.5A keeping me under the self imposed 4A limit.
The output trannie according to Danbury's blurb is good up to 50W from a pair of KT88 in UL/tetrode so its running nicely under for 20 or so watts from the EL34. I like the idea of under running wound components.
I originally did consider the all Octal route as I had a set of Chassis cut out for Octal valves. Another member has them now and I look forward to seeing his take on the EL34 power amp. To that end i laid in a stock of 6SJ7 Russian and NOS RCA US made which are pretty much the same as EF37/40/86 as far as I can ascertain. But no top cap and a lot cheaper than EF37's, an advantage in both cases as far as I am concerned. I also got a couple of NOS Sylvania 6SL7 for the LTP on the basis that they were nearer to the ECC81 than a 6SN7 is. I will hang on to them as I have some preamp ideas that can make good use of those octals.
I am fairly agnostic about brands and country of origin of valves, so the makes of those mentioned are for information rather than a recommendation. They do seem better value than the NOS B9A stuff................. so far. I got a batch of RFT ECC81 for the project for a very good price which shows there is still value to be had if you shop around.
I would have put the EL34's further back if the holes weren't already there, but in fairness there isn't a very long run to the output transformer and there's so much room I can have a nice spacious "logical" layout I hope.

Andy.

25th Oct 2015, 9:33 pm	#18
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: EL34 power amp project I don't know how they were cut, The chassis were spotted at the February audiojumble in Tonbridge by a friend and kindly bought and stored for me.(thanks terry ) If anybody knows who the guy was I would be grateful. They had all the holes cut that I needed. The transformers are Danburys, obtained from another contact on an audio forum. Pretty much the set that's still marketed for the 5-20 circuit. The mains transformer has enough reserve to run a 5U4 rectifier, this was confirmed by Danbury themselves when i spoke on the phone. The caveat is to reduce the 6.3 draw by an amp, this isnt a problem as its a 5A s winding and a couple of EL34n ECC81 and an EF86/40 draw a total of 3.5A keeping me under the self imposed 4A limit. The output trannie according to Danbury's blurb is good up to 50W from a pair of KT88 in UL/tetrode so its running nicely under for 20 or so watts from the EL34. I like the idea of under running wound components. I originally did consider the all Octal route as I had a set of Chassis cut out for Octal valves. Another member has them now and I look forward to seeing his take on the EL34 power amp. To that end i laid in a stock of 6SJ7 Russian and NOS RCA US made which are pretty much the same as EF37/40/86 as far as I can ascertain. But no top cap and a lot cheaper than EF37's, an advantage in both cases as far as I am concerned. I also got a couple of NOS Sylvania 6SL7 for the LTP on the basis that they were nearer to the ECC81 than a 6SN7 is. I will hang on to them as I have some preamp ideas that can make good use of those octals. I am fairly agnostic about brands and country of origin of valves, so the makes of those mentioned are for information rather than a recommendation. They do seem better value than the NOS B9A stuff................. so far. I got a batch of RFT ECC81 for the project for a very good price which shows there is still value to be had if you shop around. I would have put the EL34's further back if the holes weren't already there, but in fairness there isn't a very long run to the output transformer and there's so much room I can have a nice spacious "logical" layout I hope. Andy.