300b version with magnequest rh-60 compatibility

2nd harmonics for the masses

300b version with magnequest rh-60 compatibility

Postby chopdr230 » Fri Aug 29, 2008 7:21 pm

I am gathering parts to finally build my get set go . I want to run 300b's and i just ordered rh-60 transformers will these work well together if i do the standard 300b mod ? Has anybody used this configuration and if so how dose it sound ? I plan to run a pair of vintage jbl 15in with horns . Thanks AL
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Postby SDS-PAGE » Fri Aug 29, 2008 10:25 pm

They should work just fine. I see that their primary is 5k. You might lose some output power, but it will not be noticeable. You will probably get more linearity and less distortion with the setup. I built a 300B GSG w/ 10W 3k Trascendar and I liked it. You will probably get around 4.5 wpc with 385 VDC on the plate. You can always push the 300B for more juice. -Min
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Postby EWBrown » Sat Aug 30, 2008 12:12 pm

I've used the RH-60s in two 6B4G G*S*G amps with excellent results.
One set of the RH-60s is the "open frame" version, and the second is a "custom" RH-60 with bell ends, and no UL tap. Mike had a run of these these on "special" several months ago. The RH-60s sound beyond excellent, the 5K primary means a tad lower output power, butr the upside is that the 2HD and 3HD is much reduced. FWIW, the open frame RH-60s are fairly large - I don't have my amps in NH so I Can't measure them, so plan for their dimensions...

I fit everything nicely on 12 X 10 X 2 inch black powder-coated Hammond chassis. THis also included space for two chokes under the chassis, mounted at the front "corners". I used an extra choke in place of the two paralleled 180 ohm resistors in the PSU string.

FWIW, all the Robin Hood series open frame trannies are the same size. The bell end versions were more like Z565s and the black oxide bel ends look great on the black powder-coated chassis.

The RH80 might be a better (higher power) 300B match, that depends on your 300Bs' plate current, just keep it at 60 mA or below and the RH60s will be good to go! The RH80s do have less primary inductance than the RH60s, thicker wire, less turns, in order to fit onto the "standard" size bobbin and core.

I asked Mike about their current handling capabilities, and he replied that they can run at 60 mA continuously - they are rated somewhat conservatively, as are most of his trannies.

/ed B
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