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Heptode audio preamp? ECH83
Heptode audio preamp? ECH83
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Old 31st March 2007, 01:56 PM   #21
Cursor is offline Cursor  United Kingdom
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Join Date: Mar 2007
Hi Ulibub

Many thanks for your reply. Comments about cathode resistors in the Sopht amps duely noted.

Until I find an output transformer or two I'm stuck with experimenting with preamps anyway - I'll let you know how my ECH83 experiments go.
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Old 31st March 2007, 06:06 PM   #22
Cursor is offline Cursor  United Kingdom
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ooh, sorry, and thanks to engels for the design
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Old 13th April 2007, 02:11 PM   #23
Cursor is offline Cursor  United Kingdom
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HOLY CRAP - this sounds AWESOME for guitar!

I've just built it as per your original schematic with all caps .0473 and omitting the 100K resistor before the heptode grid (so just the coupling cap and the 1M grid resistor). The output goes into a 100K lin pot then to a TDA2030A power amp. I've started a thread to document the progress of this amp - but engels, if you haven't built your design yet, it's well worth it!
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Old 28th November 2012, 09:42 PM   #24
engels is offline engels  Israel
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Join Date: Jan 2007
Location: Jerusalem, Israel
Default build

I've got one ECH83 pre finished. The scheme goes like this -

Click the image to open in full size.

and it works wonderfully on guitar. It has a midrange boost and some low cut, so it's not a hi-fi or bass adventure.

I've posted it now for sale on ebay because I've had a lot of fun with it in a process, satisfied myself and now I'm aiming at different projects.

Check it owt =
Unique ECH83 tube valve instrument guitar preamplifier | eBay

and i've got a video:

ECH83 low voltage valve preamp - YouTube

Generally speaking, this is a recommended beginner project. Low voltages also keep noise at minimum and it's really quiet.
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