Quicksilver 300b monoblock (KT88 conversion)

eleakist · 17th June 2007, 11:05 AM

Any guidance re biasing early Quicksilver KT88 monoblocks converted to 300b? Only info available is that bias is to be 80ma, not 120ma as indicated on chassis near phono plug bias point. The conversion was done in Vancouver, Canada, but tech apparently has disappeared and did not supply a drawing. I see internet references to a bias meter supplied with QS amps when meter was not on-board, but any supplied with this amp is long gone. Chinese 300b tubes are only running @60%, but are matched, so wish to experiment with these before installing new 300b tubes. I rigged a mono phono plug with leads for autometer. Simply blows fuse, Need your insights and experience.

BTW - even as set-up (or not) these are quite remarkable for the price.

Regards,

Barry

Original Burnedfingers · 18th June 2007, 02:06 AM

Never seen the conversion. Can you draw the schematic?

eleakist · 18th June 2007, 08:19 AM

re Quicksilver 300b monoblock (KT88 conversion) - thanks for the response. Sounds like I may have no choice but to sketch the redesign. It may, however, be easier to comment on the changes. Does anyone have a schematic for the original KT88 monoblocks?

Original Burnedfingers · 18th June 2007, 10:22 AM

The KT88 should be about the same as this.

eleakist · 18th June 2007, 11:50 AM

Thanks for the schema. Seems these are quite different. Preamp and drivers are marked on chassis 12FQ7 and 12FQ7or !2BH7. Output tubes are marked KT88 on chassis, but have been converted to 300B, with a corresponding increase in resistor and caps, as well as filtering with 5 large multicaps on top deck. Will sketch schema or note changes from yours and recall then post. Thanks, again.

17th June 2007, 11:05 AM	#1
eleakist diyAudio Member Join Date: Mar 2006 Location: Ottawa, Canada	Quicksilver 300b monoblock (KT88 conversion) Any guidance re biasing early Quicksilver KT88 monoblocks converted to 300b? Only info available is that bias is to be 80ma, not 120ma as indicated on chassis near phono plug bias point. The conversion was done in Vancouver, Canada, but tech apparently has disappeared and did not supply a drawing. I see internet references to a bias meter supplied with QS amps when meter was not on-board, but any supplied with this amp is long gone. Chinese 300b tubes are only running @60%, but are matched, so wish to experiment with these before installing new 300b tubes. I rigged a mono phono plug with leads for autometer. Simply blows fuse, Need your insights and experience. BTW - even as set-up (or not) these are quite remarkable for the price. Regards, Barry

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18th June 2007, 02:06 AM	#2
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Never seen the conversion. Can you draw the schematic?

18th June 2007, 08:19 AM	#3
eleakist diyAudio Member Join Date: Mar 2006 Location: Ottawa, Canada	re Quicksilver 300b monoblock (KT88 conversion) - thanks for the response. Sounds like I may have no choice but to sketch the redesign. It may, however, be easier to comment on the changes. Does anyone have a schematic for the original KT88 monoblocks?

18th June 2007, 11:50 AM	#5
eleakist diyAudio Member Join Date: Mar 2006 Location: Ottawa, Canada	Thanks for the schema. Seems these are quite different. Preamp and drivers are marked on chassis 12FQ7 and 12FQ7or !2BH7. Output tubes are marked KT88 on chassis, but have been converted to 300B, with a corresponding increase in resistor and caps, as well as filtering with 5 large multicaps on top deck. Will sketch schema or note changes from yours and recall then post. Thanks, again.

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