Tube with Power IC Output Stage - JLTi

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#681
Originally posted by Franz G

I will compare this afternoon the updated Joe Rasmussen Clone with the regulated version (CarlosFM Clone).

Franz
Click to expand...

I did the T-network to one of the JLTi's here. I like it, only had a brief listen, but I like it.

Also fitted, courtesy of a lend from a friend, a pair of cryo'ed Amperex 'Buggle Boy' 6DJ8, and it's everything, and more, than I expected.

These two added together... WOW!

Hey Terry, if you are reading this, I told Steve he isn't getting the Buggle Boys back. If he turn up to collect, he will be persona non grata. :devilr:

Joe R.
 
#685
Nice!

Just one part more than before...

Let's resume:

Instead of Rf > 500K a lower feedback resistor (T-network) shows more advantages than a really short feedbackpath.

True or not?

Franz

P.S.
I like to experiment with speakers, as they produce more differences soundwise than amps.

Look here:
http://www.audiodiskussion.de/foren/hoerner/msg.php?idx=12053
or here:
http://www.audiodiskussion.de/foren/fullrange/msg.php?idx=14080
or here:
http://www.audiodiskussion.de/foren/fullrange/msg.php?idx=14116
last but not least, don't miss this
http://www.audiodiskussion.de/foren/fullrange/msg.php?idx=14082
 
#686
Hi,
I like this "T" network idea, and think it has the real potential to achieve a "great leap forward" in Gainclone design. What do you feel is its applicability to none buffered Gainclones and Opamp buffered gainclones. I know that the buffer impedence has an effect on the feedback loop, but don't understand it well enough to work it out myself.

Thanks
Shoog
 
#687
It works absolutely great, this T-network, for every inverted gainclone.

For noninverted to, but there the problem is not the same, as you can use low values for the feedback path. But with the inverted version, this is a valuable way to achieve high input impedance and very low feedback resistance.

The only reason I had some transient intermodulations TIM with a square wave signal, was the high resistance in the feedback path, what is much worse than a "longer" feedback path!

Maybe, you remarked, that I have four or five different versions of chipclones.

And I prefer tube amps. Single Ends, Class A. I own diy 300B, EL84 and so on.

But the last three days, I really missed my T-network chipclone, a la Joe Rasmussen, as I lend it to a friend.

Now, it is here back, playing again.

All my tube amps are something of "tired", compared to this amp! And no bass control...

Cesaria Evora is singing with full feelings and everything, I never heard before!

Wauuuu!

Franz

P.S.
great leap forward in Gainclone Design
Click to expand...
Thanks! I feel the same and hope, many people will enjoy this evolution of the gainclone.
 
#689
Nuuk

here, back in this thread, I already offered an excel sheet to calculate the gain and the equivalent resistance:

http://www.diyaudio.com/forums/showthread.php?postid=467094#post467094

And add a resistor between +input and ground with the value R2+R3, approximate.

Should I open an new thread about "t-network feedback for inverted gainclones" and resume the results?

Franz

P.S.
Edith Piaf is singing "non, je ne regrette rien" like never before, actually, recorded with tubes, replayed with the latest chipclone 🙂 🙂 🙂 🙂
 
#693
Yes, of course, it is not my "invention".

But I never seen before a schematics of a gainclone, using this technique.

Just try it. Reduce the resistance of your feedback path and enjoy the result.

Franz

__________
BTW: Lou Reed, take a walk on the wild side...
 
#695
Franz G said:
But with the inverted version, this is a valuable way to achieve high input impedance and very low feedback resistance.
Click to expand...

That's the point, and it's a good idea.:angel:
But in my oppinion, inverted always needs a NI buffer.
It sounds better anyway.😀

Franz G said:
Cesaria Evora is singing with full feelings and everything, I never heard before!
Click to expand...

As you have good taste😉 , listen to Madredeus and cry.😀
 
#696
But in my oppinion, inverted always needs a NI buffer.
Click to expand...

When the NI buffer is a tube, then the output impedance of the buffer is 10k and the input impedance must be >10k.

Thats why the t-network is specially interesting for tube buffered gainclones.

BTW: maybe the tube is the better buffer than an opamp😎 ?

Franz
 
#699
You guys work/post much later into the night than I can! :dead:

Yes, I was working with the values posted in the circuit diagram but it was Joe's circuit that I was looking at. :xeye:

I will shortly be putting my true class A buffered IGC into the main system and taking out the VBIGC for modification with a T-network. 😉
 
#700
Nuuk said:
You guys work/post much later into the night than I can! :dead:

Yes, I was working with the values posted in the circuit diagram but it was Joe's circuit that I was looking at. :xeye:

I will shortly be putting my true class A buffered IGC into the main system and taking out the VBIGC for modification with a T-network. 😉
Click to expand...

Joe's circuit has a gain of 44.9.

Cheers,

Terry

PS: I disregarded the OP Z of 6DJ8 which would be around
100 ohms 🙂
 
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