Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on December 15, 2012, 04:41:08 am
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Hi guy's, Got a BEHRINGER V-AMP PRO that i want to put to good use as well as some bits and pieces of parts for an amp build.
I got a pair of ECL85s that i want to use,but not much info on amp builds for these tubes, this is what i found http://www.cigarboxnation.com/group/amps/forum/topics/the-smoke-screamer-tube-amp?commentId=2592684%3AComment%3A551349&xg_source=activity&groupId=2592684%3AGroup%3A909 (http://www.cigarboxnation.com/group/amps/forum/topics/the-smoke-screamer-tube-amp?commentId=2592684%3AComment%3A551349&xg_source=activity&groupId=2592684%3AGroup%3A909) that might help with biasing for two tubes (500r for one tube)so i would halve for two tubes,YES.
I looked at DOUG's stereo pre amp for help with the input and the bias is as he has it (trying to keep it as low gain and as clean as possible)
The V-AMP has an UNBALANCE ANALOG stereo output and in the specs says that they have an output impedance of about 680 ohms and max level of +20dBu. So would i be able to glug it straight into a 12A_7 V1. Any thoyghts would be great :icon_biggrin:
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Took a look at the Smoke Screamer, the bias and load line (5k) seem odd to me: (https://dl.dropbox.com/u/1326040/ECL85_P%20170V%20LL.gif)
V-Amp Pro output of 20dbu = 7.75Vrms, which is way more than you need to drive the PI (I calculated about 500mVrms to get un-clipped output of 8W in AB1).
Jaz