[Winston O'Boogie]

Thanks Andreas 
I struggle with translating German for all but basic stuff but it looks like a good book/article.  What is the title?

Edited out as PRR has looked at the V241 so 

[Winston O'Boogie]

> without damping, some possibly quite big peaking to occur there yes?

If we are still looking at V241..... The ECC85/12AT7 is triode and lowish rp. Also the DC choke shows 70V drop from B+ so has like 10k dead resistance inside. Assuming the OT is similar, we get -1dB @ 50Hz and -3dB @ 26Hz, with 6dB/oct slope at first then steepening below 3Hz. All hardly affected by load/no-load. This neglects the NFB around the ECC85, so it may be flatter at 50Hz and more-bump at 3Hz, but can't be much NFB so won't be a big bump. Seems good to me.

OK, you posted while I was.  And you were less lazy than me so, yep, looks good enough for Rock 'n' Roll

[PRR]

Voltage across the first coil dips 9dB @ 4Hz, reducing core saturation. Tube current rises of course (coil action) to about 4Hz and then falls. That for a flat input. In good German broadcast practice there will not be huge LF power in the line.

I think the Old Guys knew what they were doing.. 

[Winston O'Boogie]

I think the Old Guys knew what they were doing.. 

Like I said earlier, I've yet to see a German broadcast amplifier (either old East or West) not be anything but very well executed for the task. 
So yep, they knew a thing or two 

[Tubetec]

The chokes might be similar to the  type found in TeleV series ie sectionalised with the bobbin partitioned into two,three or more . There isnt much of a selection of anode load chokes out there by the looks , or not that I can find anyway.

[Winston O'Boogie]

The chokes might be similar to the  type found in TeleV series ie sectionalised with the bobbin partitioned into two,three or more . There isnt much of a selection of anode load chokes out there by the looks , or not that I can find anyway.

Yes.  The V72 choke is a three section. 
I did modern recreations of the V72 and V76 for a manufacturing company around 13 years ago and had Cinemag wind the chokes.  These were designed by Tom Reichenbach based on specs I gave him and he did them in 2 sections, they worked well.
Not sure if they're up on the Cinemag site but they do still make them.

I haven't tried the Sowter myself but I do know there are some nice anode chokes from Lundahl that work well.  At  least the one I tried anyway.

Edit: Cinemag chokes internal pic added.

[Tubetec]

Lundahl Anode choke, LL1667/8 might be a reasonable  choice ,

https://www.lundahltransformers.com/chokes/

[Winston O'Boogie]

Lundahl Anode choke, LL1667/8 might be a reasonable  choice ,
https://www.lundahltransformers.com/chokes/

Yes LL1667 is the one.  It doesn't show it on the pdf spec sheet but you can specify current and, if gapped for 7mA, inductance is over 700H if memory serves.

Edit: OK I found the spec.  Gapped for 5mA = 810H and for 7mA (about right for a V72/V241) = 580H.  DCR is 2400 in both cases.

[JShaffer]

Curious, did you ever get your v41 builds going? I'd love to learn anything you learned or alternatively offer a soft landing place for the OPTs if you ran out of time. Thanks!

Justin

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