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Preamp schematic check
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=80774&th=19918#msg_80774
Anyway, it's a BEZ Q4B preamp that comes from China, point to point wiring handbuilt by the designer, and has gotten some pretty good reviews from the people who have bought it over the last 10-12 years. It's simple, I can kinda follow a schematic, but I always layout a wiring diagram to help me visualize. Actual layout I can do, just the wiring bit helps me not screw up. So here's a few photos of one of the preamps, it's innards I could find, the schematic, and my little diagram. IF anybody has the time to check my wiring diagram I'd appreciate it.
]]>Shane2014-10-31T23:23:50-00:00Re: Preamp schematic check
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=80775&th=19918#msg_80775
EDIT: I notice that there is no provision to protect the tube from high heater to cathode voltage. my experience is that without it the tubes do fail....rather dramatically as well with major noise going toward the amps. I always raise the heaters off the ground by about 60-80 volts DC. There is a side benefit as well as the S/N is improved slightly. The way to do this is not ground the CT of the heater trannie and instead make a voltage divider with about a 220K and 100K from a clean B+ source (only one is needed for all the tubes). At the tap attach a 2-5 us poly to the signal ground and the the tap goes to the CT of the heater circuit. If there is no CT then either leg seems to be nearly as good. I attached schematics of a similar design. There have been a few minor changes since the schematic was drawn, but they are not required for excellent performance.
]]>gofar992014-11-01T23:10:02-00:00Re: Preamp schematic check
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=80784&th=19918#msg_80784
I think the VR tubes can be a noise maker if not implemented properly. I've seen a nice, supposedly quiet VR implementation where a CCS was used before the VR tubes to give them the best mA. Decware uses them in their Torii amp, fwiw, so I'm thinking implementation (and good tubes) is key.
I'd love to build a Forewatt, but it's just out of my price range right now. I bought most of the compnents to build a Hagerman Clarinet, minus the iron, he discontinued the boards at the same time. Should have ordered the board first. Guess I could go p2p on it if I really wanted.
I don't really need a preamp, just want to build something that isn't going to cost as much as an amp I tend to cycle on my hobbies and I'm back to audio again.
I could build an Aikido and use it for a headphone amp as well.
So many possibilities.]]>Shane2014-11-03T23:12:09-00:00Re: Preamp schematic check
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=88478&th=19918#msg_88478
Do any of you design your own layouts, or do you always work from schematics?
Can I ask a question? What does a pre-amp do that an amp doesn't do?]]>JazzHog2018-07-21T12:38:10-00:00Re: Preamp schematic check
https://audioroundtable.com/forum/index.phpindex.php?t=rview&goto=88482&th=19918#msg_88482
gofar992018-07-21T22:26:45-00:00