Hello all.
I am trying to make use of 10 nos ef86 tubes I have.I also have 2 ecc82.
I have built a valve phono stage,so I want to make a preamp at line level.
I don't need tone control
Can anyone recomend a schematic
many thanks
I am trying to make use of 10 nos ef86 tubes I have.I also have 2 ecc82.
I have built a valve phono stage,so I want to make a preamp at line level.
I don't need tone control
Can anyone recomend a schematic
many thanks
Check out Mullard's preamp section:
An externally hosted image should be here but it was not working when we last tested it.
Funky with C1 and R3 across the anode load on V1. Looks like they may have had some issues with RF oscillations on the input stage. Or didn't want such oscillations to return in issues in the field.
Just an observation....
~Tom
Just an observation....
~Tom
I think you meant C1, R1... By funky, you meant classic, right? 😀
"A CR network (C1, R1) shunting the anode load produces an advance in phase which increases the stability of the amplifier at high frequencies."
More here >> Mullard 5-10
I was referring to the schematic linked on my second post - it turns out it's different from the earlier schematic I posted, sorry about that... Same idea though, R1 & C1 refer to this Mullard schematic:
An externally hosted image should be here but it was not working when we last tested it.
Jaz
I can't think of any situation where the gain of a ef86 in a preamp would be anything but a disadvantage. It then requires copious amounts of negative feedback to kill the gain - and a preamp is definiately one of those situations where there is little need for feedback.
This tube has no other place than a phono preamp in my opinion.
Shoog
This tube has no other place than a phono preamp in my opinion.
Shoog
I would look into the quite interesting radford ( a vondeful amp by the way )
There is some papers for taming the high gain somewhere ( cant locate it right now ) and a great 2 vol article by Radford explaining the way it works.
An externally hosted image should be here but it was not working when we last tested it.
There is some papers for taming the high gain somewhere ( cant locate it right now ) and a great 2 vol article by Radford explaining the way it works.
I would agree (or a Mic or tapehead preamp) and even then It will be noisier than a decent ECC83 stage.
Why not strap it as a triode to reduce the gain?
The OP was asking about preamps, so why post circuits for power amps?
The network at the anode of the EF86 is to stop feedback loop instability (typically in the low ultrasonic region); the input stage itself is very unlikely to suffer from RF instability.
The EF86 has no place in a modern line stage, as it has far too much gain. Keep a few as spares (for your phono preamp?) and sell the rest so you can buy more suitable valves.
The network at the anode of the EF86 is to stop feedback loop instability (typically in the low ultrasonic region); the input stage itself is very unlikely to suffer from RF instability.
The EF86 has no place in a modern line stage, as it has far too much gain. Keep a few as spares (for your phono preamp?) and sell the rest so you can buy more suitable valves.
Try this, it is really good.
6th Street Bridge: Triode Connected EF86 linestage and headphone amplifier
6th Street Bridge: Triode Connected EF86 linestage and headphone amplifier
I have used this one from Svetlana as a preamp in my headphone amplifier, and it works very well.
even triode connected, a voltage gain of 25 is terribly high with modern digital sources. Perhaps the additional gain would be nice for a HOMC. I would also suggest some *gasp* local and/or loop feedback to reduce the total gain.
Triode connected EF86 has gain comparable to any medium mu triode and thus can be used easily with some NFB, which improves the linearity as well.
It is possible to achieve vanishingly small distortion in a preamp stage without any negative feedback - so why would you use it.
Any of the more appropriate line amp tubes such as the ECC99 or 5687 can deliver orders of magnitude more current drive which will address far more problems than using a weedy EF86.
Shoog
Thanks everyone,you have all given me some great advice.I just wanted to use ef86 as they are mullards and new. I may need to get some ecc83 from russia or china then as I have used my stock up!
Any one recommend new ones that are mullard like?
Any one recommend new ones that are mullard like?
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