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Old 19th October 2012, 10:04 PM   #1
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Default ecc99 preamp into an amp

Hi, my first here.

I know its probably a typical newbie question, but it hunts me for some time.

I've completed a ecc99 preamp (1x ez81 into 1x ecc99) and since i use high sensitivity speakers for near-field listening only, i'm ok with ~ 400mW pc.

Is it possible to drive 6-8 Ohm speakers directly just by changing the output stage for transformer-type ?

If yes, are there any recommendations for OT ?

Is it possible to stay running in SE mode then ?

For now i'd like to stay as simple as it can be, not to fall in to searching and spending for power triodes, building a whole amp etc.

Thanks for any opinions and patience.

nice weekend,
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Old 19th October 2012, 10:09 PM   #2
tinitus is offline tinitus  Europe
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with a few more ecc99

if you could make you preamp with balanced out, it might be easier to build a ecc99 'power buffer'
but then, might be better to think twice and use a better tube

I remember now, I think there is a guitar amp with a single ecc99, somewhere
might have high distortion tho, I dont know

also seen a very simple and cheap EL84-EL84
SE EL84, does it need a driver at all ? I dont know
or just a crazy thought, SE 6V6-6V6
I know, too much crazyness
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Old 20th October 2012, 10:54 AM   #3
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You can get 300mW from an ECC99 working as an SRPP. Check out Pete Millets headphone amp design for details.


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Old 21st October 2012, 08:40 PM   #4
tinitus is offline tinitus  Europe
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Originally Posted by misok View Post
..... near-field listening only, i'm ok with ~ 400mW pc.

For now i'd like to stay as simple as it can be.......
you can try this with a battery
sorry its not a tube thing
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Old 22nd October 2012, 06:15 PM   #5
tomchr is offline tomchr  Canada
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You'll need a low output impedance. A handful of ECC99s in parallel in a OTL configuration with some global negative feedback should be able to get you there.

If you want the OPT in there, I suggest grabbing RDH4 or Morgan Jones' book and draw some load lines. The ECC99 is a very linear tube. You shouldn't have any trouble finding an operating point that'll work. Ra is a bit on the high side compared to power tubes, so you'll probably end up with an OPT in the 10 kOhm range. That's my guess anyway.

Modulus-86: 40W/8Ω @ 0.000061% THD. HP-1: 3W/20Ω, 450mW/300Ω @ 0.000032% THD. DG300B and Other Tube Circuits.
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Old 22nd October 2012, 08:52 PM   #6
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many thanks for all reactions.

1. i know i have to study much more to have a sufficiently complex overview. it is in (some) progress

2. i admit i tend to think like 'i have to go SET since that is the essence of tube charisma' ..too biased i guess, i see a p-p scheme and i run away..things like that. I read odes on DHTs and dream like a little boy..'if im going to throw myself into building something, it has to be something 'real' and so on. 2a3 and 45 are out of my range but look, here i have a dual triode on my shelf, lets try to squeeze some mWs.

in the ecc99 datasheet i rode '4x ecc99 - 10w' and i thought great, there should be way to get at least 0.5w from one. but i see the impedance would be another obstacle.

i may forget messing with this preamp, use it with my ta2024 based power amp and search for a simple SET charlize-like schematics based on non-mainstream triodes.

all the best,
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