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ECC99 line preamp

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#2
Well, since the ECC99 is a double triode I suppose you could call Raven a one-tube preamp, even though it uses both triode halves of the tube. It is supposed to be very good, but it won´t be very cheap wid ´dem chokes, input and output transformers. On the other hand, it can drive headphones and you get a balanced out.
 
#3
I notice that the raven preamp has a stereo volume control per channel. this is just crappy design.

A single pot wired across the phase and antiphase lines, with the wiper taken to one side is all that is required.

the PSU is also a bit on the complex side for a simple class A amp. As the current take is relatively light, a simple two stage RC coupled PSU filter is all that is required.

kind regards

bill
 
#4
Hi,

If it is just for a line pre-amp with no gain (just as a buffer) it will perform excellent as a cathode follower with a bias current between 5 and 10 mA. Dig through this forum and you will find many examples and discussions.

Cheers 😉
 
#5
Hello

you have me beaten with your comments.

The amp has gain, it is not a cathode follower, it is a balanced line stage using a transformer to split then recombine the phases.

The point that I was making is that the volume control is wrong.

That's all.

I don't understand the connection between my post and yours. care to enlighten me?

thanks

bill
 
#6
Hey Bill, dont be such a Bull! Pjotr is answering kooltubes, not you! The subject i using a ECC99 in a line stage.
BTW. Using a single pot between the phases is not a good idea since you load the source at low settngs. I think the Raven design is better than what you suggest. Take that...
Best regards, and Semper Fi!

:bigeyes:
 
#8
Hi,

I notice that the raven preamp has a stereo volume control per channel. this is just crappy design.
Click to expand...

Actually. if you look at the xformer preceding the attenuators you'll notice the grounded CT, the two att. make sure that each winding is loaded properly at all times.

Anything simpler? The far I can go is tube-rectified PSU and output transformers...I just want to listen to music...lol
Click to expand...

There are much more possibilities if you're willing to go higher on the B+.
I'll post some diagrams later tonight.

Cheers, 😉
 
#9
LATER THAT NIGHT....LES SUGGESTIONS DU CHEF.

Hi,

Here are a few diagrams for you to toy with:

Cheers,😉
 

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#15
Here's one more possibility. Although it needs a negative supply, if you're using SS, both supplies are very easy to make. The bias point is a little light on the current (2mA per section), but this is easy to fix so long as you are willing to beef up the supply.

With the values shown, the gain should be about 4 (12db) and the Zo around 200R. It does not invert the phase. Distortion should be very good. The drawback is the NFB. Many will object, but you can eliminate it by replacing the 24K resistor with a wire and the 100K resistor with 1M. The gain will go up and so will THD.
 

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#16
Hi,

Many will object, but you can eliminate it by replacing the 24K resistor with a wire and the 100K resistor with 1M. The gain will go up and so will THD.
Click to expand...

Nice circuit...I quite like it.

Re feedback: The only way to make anyone actually build something is to not mention the words cathode follower and feedback in the same sentence...😀

Which reminds me: won't the output impedance increase as well when the NFB is removed?

Cheers,😉
 
#17
won't the output impedance increase as well when the NFB is removed?
Click to expand...

yes indeed, i forgot to mention that. 🙂 approximately 850R with no NFB.

this particular topology is used in Transcendent Sound's GG preamp, but I don't think it is original with TS. The component values here are not the values in the GG preamp. it uses 12au7s.

since i only violated half the rule, perhaps someone will try this. 😀 i've used this particular stage very successfully in some headphone amp designs.
 
#18
Nice to see that circuit Runeigt 🙂 Im working on almost exactly that circuit for my new pre-amp but instead of a tube I am using a Fet cascode for the Mu follower, -15V neg supp. with a SS CCS. However stability is a bit tricky, it is quite wideband.

So Frank I hope some people will survive this post:

A cathode follower driving a stage with feedback that uses SS.

😀 😀 😀 😉
 
#19
Great. I sure would like to know how it comes out.

Although the follower portion of this is an SRPP topology, it could be replaced with a tube mu follower. It would take a little more B+ to do that, but theoretically the performance would improve some. Maybe not enough, however, to be worth the trouble or to sound better than a fet version.

The CCS on the tail is definitely a good idea and relieves the negative supply considerably.
 
#20
Hi,

A cathode follower driving a stage with feedback that uses SS.
Click to expand...

I've never really understood this masochistic streak in people...:xeye:

but theoretically the performance would improve some
Click to expand...

On paper certainly...Give it a try but from past experience_not just my own_ the SRPP circuit, with all it's theoretical shortcomings, is often the more musically convincing of the two.

The CCS on the tail is definitely a good idea and relieves the negative supply considerably.
Click to expand...

This one does get my endorsement...I'd stick a tube under those LTP cathodes but you all know my vices by now, don't you? 😀

Cheers, 😉
 
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