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Old 6th October 2007, 09:30 PM   #1
JandG is offline JandG  United States
diyAudio Member
 
Join Date: Jan 2005
Location: Washington State
Default Built a quick 26 pre yesterday..nice so far,,

The preamp has a seperate PS chassis & the front 2 sockets are for 27's & used the rear pair for a 26 circuit,. Only have to change B+ on internal terminal block to switch between the 2, I have a DPDT switch installed in chassis , just have to hook it up. Filaments are ran with a nice old lab supply. It is dead quiet on 98-99 db Calrad 12AE's in open baffle. no microphonics eaither which I think the very solid oak chassis help in that. Amp pictured is a 6sn7/6sn7 amp, so not much power or gain, but for bedroom use with the fairlly high efficient Calrads 12AE's it is perfect. I would say the 26 has a sweeter top end than 27, but 27 is still very nice in this very simple cap coupled jobbie. Very low plate voltage of about 80v on the 26 plates, w/ 4.8v of battery bias NiMH. 22k plate load, I use 2- 6w4's for rect..& 2-OA3's for shunt reg. also CLCL using nice old chokes & ASC oilers for caps. I think I will try to find a schemtic for a 26 or 27/45 amp build for a small bedroom amp. Click the image to open in full size.
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