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Pre Amp http://diyaudioprojects.com/Forum/viewtopic.php?f=6&t=6697 |
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Author: | simo [ 12 Jan 2020, 00:07 ] |
Post subject: | Pre Amp |
I am building my second "DIY SE KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier" http://diyaudioprojects.com/Tubes/KT88/ The first version of this amp I built, I used a separate tube pre amp with a 12AX7 tube and it worked fine. However, on this unit I want to build the pre-amp into the same unit. The max plate voltage on the 12ax7 is 300 volts and this amp has a B+ of around 400 volts. I am trying to avoid running two transformers and power supplies in the one unit. The other option is to use a pre amp with a higher plate voltage. Any suggestions on this would be helpful. John |
Author: | Suncalc [ 12 Jan 2020, 10:54 ] |
Post subject: | Re: Pre Amp |
simo wrote: The max plate voltage on the 12ax7 is 300 volts and this amp has a B+ of around 400 volts. Maximum plate voltage and maximum B+ are two separate entities. The maximum working plate voltage (plate-to-cathode- differential) of a 12AX7 is 330vdc. The maximum zero current plate voltage (i.e. B+) is 450vdc. You'll be fine with a 400v B+.
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Author: | simo [ 12 Jan 2020, 16:12 ] |
Post subject: | Re: Pre Amp |
Thanks for your help. I was confused on the plate voltage and B+ but that explains it. Thank you |
Author: | simo [ 15 Jan 2020, 01:48 ] |
Post subject: | Re: Pre Amp |
I also want to add the facility for the preamp to accept a phono (pickup head) as well as other inputs. The schematic I am using has a 470k Ohm resistor on the grid input to ground and a 10k resistor in line to the grid. http://diyaudioprojects.com/Tubes/Unive ... amplifier/ I want to be able to switch the following input devices - Tuner, Ipad, Phono, CD player. Any advice on the most efficient way to achieve this would be great. Regards, John |
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