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- MQ on S-240-A

- Dr. Jean-Francois

2A3 SETH S-240 Monoblock
Parts List
beauty of economy

R1 Two Dale metal film 100 ohms 1/4W in parallel
(one end to each grid pin on the tube socket)
R2 Holco metal film 43.5ohms 1/2W
R3 Mills Wirewound 4.02K 12W
R4 Mills Wirewound 12W 1K in parallel with
Mills Wirewound 12W 750 ohm
C1 Black Gate "FK" 100uF /16V
C2 Solen 6.8uF/630V (Or Preference)
C3 Black Gate "FK" 100 uF/100V
C4 Solen 1.5 uF/630V
C5a,b Cerafine 47uF+47uF/500V(Or Preference)
T1 MagneQuest "Peerless" S-240-A (used permalloy)
T2 Hammond 374BX 375V-0-375V 175 mA
(MQ MQR-060 excellent sub - C4 value to 1.8uF or 2.0uF)
T3 Hammond 166Q2 2.5V CT 6A
L1 MagneQuest BCP16 GC (Used permalloy version)
L2 MagneQuest EXO-173 PPS (Used permalloy version)
L3 Hammond 193H 5H 200mA 65ohms
(MagneQuest MQ 04-002 excellent substitute)
L4 Hammond 193H 5H 200mA 65ohms
(MagneQuest MQ 04-002 excellent substitute)

See the 2A3 SETH Circuit What strikes you right off the bat about this design is the MINIMAL parts per monoblock. This is simplicity exemplified, especially for a push-pull design. Parts cost is very reasonable with sonics a major reward. Possible subs might be Tantalum resistors (keeping Mills) and your coupling cap of choice as long as you are willing to part with the ducats for a 6.8uf! Go for the BG WKZ if you can find them and you have the funds.

But the heart and soul of this beast is the EXCELLENT MagneQuest "Peerless" S-240-A output iron, this featuring the all Permalloy version (the M6 is no slouch either). Ditto for the MQ EXO-173 - This is simply an excellent phase splitting device. And while the Hammond 300 series PT is very nice and much better than the 200 series, the MagneQuest MQ MQR-060 is a helluva power trans and step up in capability. Throw in some custom designed MQ 04-002 chokes for the PS and things are looking even better.

And yes, this is a stellar amp; Jeff seemed to be REALLY impressed with the low end punch, imaging detail without bloat, and speed, all without a loss of musicality - but he had to admit that adding the MQ BCP16 NiGC grid choke put some more icing on the cake.

And right now, Mikey is offering the SETH IRON PACKAGE deal with cost savings for the whole iron option from MagneQuest.

JFL & kh

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