UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Pre-amp for Golden ears

Synchrodyne · 12th Mar 2018, 6:56 am

Is it necessary to use an RF double triode? The ECC83 has been used in AF cascode circuits. And Rogers used the ECC808 for the cascode input stage of its Master Mk II control unit. I think that the ECC807 was also specified for cascode applications.

Amongst the RF double triodes, I don’t think that low microphonics was a specific property of the 6BQ7. Apparently the 12AT7 did have low microphonics by RF standards; GE designed it for use as an FM and VHF TV mixer-oscillator; for the FM and split-sound TV applications, low microphony was highly desirable, and in this regard it was said to be noticeably better than the 6J6.

Would a cascode input stage – presumably with shunt feedback – be any quieter than say a series-feedback triode pair with DC heating?

Cheers,

12th Mar 2018, 6:56 am	#4
Synchrodyne Nonode Join Date: Jan 2009 Location: Papamoa Beach, Bay of Plenty, New Zealand Posts: 2,944	Re: Pre-amp for Golden ears Is it necessary to use an RF double triode? The ECC83 has been used in AF cascode circuits. And Rogers used the ECC808 for the cascode input stage of its Master Mk II control unit. I think that the ECC807 was also specified for cascode applications. Amongst the RF double triodes, I don’t think that low microphonics was a specific property of the 6BQ7. Apparently the 12AT7 did have low microphonics by RF standards; GE designed it for use as an FM and VHF TV mixer-oscillator; for the FM and split-sound TV applications, low microphony was highly desirable, and in this regard it was said to be noticeably better than the 6J6. Would a cascode input stage – presumably with shunt feedback – be any quieter than say a series-feedback triode pair with DC heating? Cheers,