• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Elektor Claus Byrith 4-30

The reason I ask is that the Byrith version uses Lundahl 1663 OTs whereas the Elektor version uses much more expensive 1620s. Does anyone know why? And are there any other makes of transformer I can use? I’m on a budget and the 1663s are a stretch - the 1620s are out of range for me.
 
A link to schematic and other info maybe?
Lundahl LL1663 is US$145 each, approx. 100 quid in Blighty? Sowters would likely be more. Primary Windings in the UK have this one for the 5-20: 25W 6600 Ohms Ultra Linear Push Pull Output transformer – Primary Windings
74 to 85 quid each depending on mounting style. Buy 2 or more trannies from them and get 10% off.
Don't think you'll get anything decent for less. Don't even think of eBay stuff from the Orient.

Steve
 
This is part two.

I might go with the Primary Windings TXs or the Lundahl 1663s then. I just wasn't sure why the Elektor version uses the Lundahl 1620s. Is it just for more output headroom?
 

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  • Valve Final Amp (2) Part 2_ printed circuit boards and construction.pdf
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The reason I ask is that the Byrith version uses Lundahl 1663 OTs whereas the Elektor version uses much more expensive 1620s. Does anyone know why? And are there any other makes of transformer I can use? I’m on a budget and the 1663s are a stretch - the 1620s are out of range for me.

The 5-20 is less fussy about the output transformer than (f.ex) the Williamson, especially when the EF86 is run in triode mode. You should be fine with any semi-decent (not guitar) output transformer.
There was also the Maplin Millennium version:
Index of /millennium
 
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The Elektor build suggest the following resistors.

"All fixed resistors: metal film, Beyschlag type MBE0414 or BC Components type PR-02, dim. 4x12 mm."

Can anyone please suggest a supplier of these parts in the UK? I just checked the Farnell site and the voltage rating on the Vishay metal film resistors is only 350v. Any alternative resistor suggestions gratefully received.
 
Where are you buying them, Kei?
I usually buy them from mouser or digikey as they tend to be similar prise wise to RS in the UK even when factoring in shipping. The 1W PRP metal film items listed on hificollective are also rated for 500V. There aren't many metal film resistors rated above 500V in sub 2W ratings. It may be worth switching to carbon film or metal oxide in the places which demand 450V+.
 
Can anyone see any problems with this layout? Is the toroidal PT and PSU PCB far enough away from the EF86 and ECC83? They're the two smaller circles on the amp PCBs towards the bottom of the pic.

An externally hosted image should be here but it was not working when we last tested it.


<blockquote class="imgur-embed-pub" lang="en" data-id="a/xxzg8mQ"><a href="//imgur.com/xxzg8mQ">Claus Byrith 4-30 hi fi amp layout</a></blockquote><script async src="//s.imgur.com/min/embed.js" charset="utf-8"></script>
 
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