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ectobia 7th October 2007 01:02 AM

build 805 or 845 se for ~$1000
what's the feasability of building a 805 or 845 single ended tube amplifier for around $1000? thanks

ak_47_boy 7th October 2007 06:47 PM

Depends on the iron.

soulmerchant 7th October 2007 08:23 PM

good luck. I would start by changing it to a GM-70 project. Russian triodes similar to the 845 but cost much less...

Read this:


"The GM70 has a mu of 6.9 and Rp of 1800 and best part can be run at below 1KV"
"Max plate Dissapation is 125Watt"
"48 Watts Single ended"

And my favourite quote:
" use the beast to drive my Fostex 206 and really make it into a party animal now"

crazy... I gotta get me some.


ectobia 7th October 2007 11:49 PM

That tube looks sweet
and I bet it sounds magical, Too bad I don't have experience working on high voltage tube amps yet.

kevinkr 8th October 2007 01:50 AM

Re: gm-70

Originally posted by ectobia
That tube looks sweet
and I bet it sounds magical, Too bad I don't have experience working on high voltage tube amps yet.

If you don't have the experience to deal with a GM-70 I am confused as to how you think that this is particularly different than building an amp around the 845 which generally requires a minimum of 900V for good performance? :xeye:

You should start by reading the safety and newbie threads, and believe me if you feel intimidated by the GM-70 you should NOT be considering an 845 amp by any stretch of the imagination.

Good iron for an amplifier like this is going to eat almost your entire budget, so you might want to consider a safer low voltage design like the Simple SE from tubelab from both a safety and budgetary point of view - it's good, uses voltages that are a little less lethal than an 845 and sounds very good. Using KT88s powers in excess of 10Wrms per channel could be within reach of your budget. (With a little more work you could use 6C33 to get 15Wrms, using tubelab's board with outboard sockets for the 6C33.)

soulmerchant 8th October 2007 01:02 PM

kevinkr is very right. Make your first amp something small and easy. Preferably one that is tried and true. Preferably with a printed circuit board.

Study the circuit and ask silly questions about why, how and what it does. Search this forum and read a lot. Buy yourself a good book Like Morgan Jones' Building Valve Amplifiers and read it through.

Then try to build a decent single ended amp. Single ended circuits look simple, but they are actually more difficult. Wire it up point to point yourself. You will learn many things...

Once you get the basics down for how to build a good SE then start thinking about broadcast triods. That is roughly where I am now.

But PLEASE read those safety threads all the way through first. Your life depends on it.

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