JE Labs 300B SET Amps

JE Labs 300B SET Amplifier with James 6123HS OPTs

Custom ordered

Completed on 2/25/08

This was by far the simplest amp that I've wired so far. It helped to have all the big components mounted on top and to have all that space underneath. The only thing that I would have done differently is to have the OPT where the choke is. Steve Chu, my customer, wanted it this way for looks and I just had to make it work. Well, customers are always right. When I first fired the amp up, I noticed that there was clicking noises coming from the bypass cap for 6SN7. Apparently, the voltage handling on the cap was a bit low and was working to its limit. I replaced them with 47uF 160VDC and the clicking went away.

Under the hood with everything mounted on the top plate. Notice the octopus of wires coming out of those holes off of power tranny.

Voila! The finished amps. I thought my Dynaco MKIIIs were big. They are puny compared to those 300B monoblocks!

Yep, all those irons for glorious 9 watts of SET audio.

These monoblocks weigh at least 40 lbs each.

Size comparison of James 6137HS iron to 6113HS. The 6137HSs are SE 30W 7K primary and 4, 8, 16 ohms secondary taps. I am putting 8 ohms loads to 16 ohms taps to lower the primary Z to 3.5 k for 300Bs. It's all about ratio when it comes to trannies.

How does it sound? I am very happy with these amps. They really groove to the music when listening to rock or pop music. Great textural rendition and rhythmic integrity when listening to complex ensemble. 9 wpc is plenty for my listening level and the efficiency of my speakers, but it's still just 9 watts. They do seem struggle a tiny bit when I try to push the full power of orchestra through them. All in all, their dynamic performance is amazing for most music I have CDs, mp3, and records for.

Will I build these for myself? Probably not, mostly because of its size and the cost of construction. I think the same caliber of sound can be achieved using other designs in stereo at 3/4 of cost or less.