Grampian head with a Rek-o-kut amplifier - will this work?

[OPP]

Hey fellow trolls -

Will a rek-o-kut R-8a aka the Challenger amplifier section satisfactorily amplify a Grampian 16 ohm head? The Rek-o-kut apparently outputs 13.5 watts, and has a tap for 16 ohms.

Thanks!

[markrob]

Hi,

It will work, but 13.5 watts is quite a bit under powered for this head. I would use a 50-150 Watts amp for best results. As long as you don't expect to cut at very hot levels, you can use this amp. Give it a try and see.

Mark

[OPP]

Thanks very much Mark. What confounds me with the old amplifiers is the output rating. The Presto 90a is 10watts but is supposed to pair with a 1c or 1d head. How is this possible, or were people cutting at really low levels back then?

[markrob]

Hi,

A combination. The 1D and C don't need very much drive and with much above 20 Watts, you are into the high distortion range for this head. Remember, back in the day, 20 Watts was a bigger sized amp. When the Grampian was released, the feedback amp along with the head was sold as a turnkey system (either the RA7 or Gotham PFB-150). The PFB-150 used a pair of 811-A triodes typically used for RF power amp applications. The Grampian doesn't require much drive either (spec is 1.26 watts at 1Khz for 7cm/sec peak recorded velocity), but it can take more drive without distortion (hotter cutting levels). Note that going from 13 Watts to 150 Watts is only an increase of about 11 db. Neither head can handle 150 Watts on a continuous basis. Finally, given the wider bandwidth of the Grampian (should get close to 20 Khz), you need more peak reserve power to make the head move at these frequency extremes. Hope this makes sense.

Mark

[OPP]

Thanks very much for the information Mark - really really appreciated!
Owen