Inter stage iron in High End

[Jaime]

You think Interstage iron is good in High End ?

The Seth amplifier in the Magnequest forum is very popular.
http://www.magnequest.com/diy_lessard_2a3pp.htm

best regards Jaime

[analog_sa]

Yup. I think it's also good in low end. This Seth amp bears remarkable similarity to this

[Jaime]

What happens with your PP 2A3? In 2004 you are happy.
But now...” I think it's also good in low end” .....
¿low end? Please...explain.
Best regards Jaime

[analog_sa]

Sorry Jaime. Still happy. Meant 'low end' as bass frequencies

I think i've tried all types of phase splitters and none can touch a good transformer sonically. In a zero nfb circuit of course.

[Jaime]

I had understood “low end” as opposed to High End !!!.
Now is all right. I like this idea very much.
Other question :
You have two PS, one in the driver stage and the other in the output.
This is monoblocks or can be an stereo?
I think you have good sensibility for an integrated.
Best regards
Jaime

[analog_sa]

It is stereo at present. I find separating PS for input/driver/output stages more beneficial than separating left/right. It is not a very widely accepted concept

[Gluca]

Ciao Analog!

I made somethig very similar to you amp ... I just used 6H30 (and 6N6P) instead of 6C45P.

In the very first try, it was PP to PP using LL1660PP. I changed the driver stage after a month or so. I made it SE to PP (LL1660PP can take up to 10mA DC); later I made it choke loaded and cap coupled to the IT, after i rewired 6H30 as a SRPP and later on I used a mu-follower (EF84 on top) still cap coupled to the LL1660PP.

I preferred SRRP and mu-follower (signal taken from the lower anode and not the upper cathode as usual). SRPP is actually much more simple. I'd suggest you to give it a try ... you wont be disappointed.

I was happy with that amp ... and one day I tried a pair of MQ's EXO173PPS (ni lams) ... WHAT A DIFFERENCE! Much better. Sound was a bit "dull and dark" with LL and more "clear and open" (whatever it means) with EXO173. Now my LL1660 are stored somewhere in a box. To be honest those LLs can do a great job, but I found the sound again "dull and dark" when I used them in a preamp: I switched to a ni tranny at the output of that preamp and I was really pleased with the results.

On the whole it was really pleased by that 2A3 PP amp, but the IT did really changed the sound more than the driver.

Ciao
Gianluca

[analog_sa]

Now my LL1660 are stored somewhere in a box.

he, he. A great and very informative post Gianluca. I am very much aware that the LL1660/18mA is not the most suitable transformer for splitting phase. Big gap and not very symmetrical at high frequencies. Obviously more suitable as a 1:4.5 than 1:1+1. Still, i have never found it lacking sparkle.

How do you find the low end with the EXO173? I should probably get a pair anyway. And will try your suggestions about the driver -thanks.

So, you didn't like the PP to PP? What transformer did you use at the input?

[Gluca]

Big gap and not very symmetrical at high frequencies. Obviously more suitable as a 1:4.5 than 1:1+1. Still, i have never found it lacking sparkle.

Mine is PP, so it comes with a minimal gap to allow some current imbalance as the datasheet suggests. I used it as 1+1:1+1, 1:1+1 and 4.5:1 and I did find the same results at all configs. A 40/50kHz +3dB bump and a hi freq ringing at the square waves. Not a problem anyway, its quite typical for interstages. Sonically the music was as I said ... "a little bit boomy and dull ... bass seemed to came from a grotto". But it is such a flexible tranny that I decided to save it for future experimentations. And it is quite cheap. Maybe amorphous lams make it sing ... but it is really expensive! In the same amp I used a LL1623PP at the output and it was really great. I sold it as I am not planning to build amps where it can be used. It was really great.

How do you find the low end with the EXO173?

No problem at all. Bass is rich and detailed. I have been using EXO173 (nickel lams) in a number of projects as splitter, step-up and step-down interstage iron and I liked the results. A not coming back solution IMHO. And I like parafeed amps so that added cap is not hurting me at all.

So, you didn't like the PP to PP? What transformer did you use at the input?

I'd say I preferred the other topologies I described and the nickel interstage as I have no objections against PP. One day I'll build again a PP to PP amp (thats why I saved the LL1660 ).
I used a cinemag 15/15B tranny at the input. Great value for little money. Still using them.

Those are just my impressions after having used the LL1660 for one year or two and compared to other trannies. Probably yours would be different.

Ciao
Gianluca

[Jaime]

Hi Analog_sa and Gluca

The inductor EXO-173 (nickel) look nice, but is very expensive for my pocket !!! Another possibility?

You never made an experimental “forced fully balanced” with a CCS at cathodes? Many people said it is a lot over the SETs

Best regards Jaime