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Anode choke question

Tonu,
I do not have extensive experience with choke loads. I used it only once in a DC coupled design. The choke gave a good account of itself but I preferred a simple load resistor. This is because my brain tells me that the load impedance of a choke varies with frequency and so I developed a prejudice.

I know that capacitors also have resonant frequencies. But I do not view them with such prejudice. Perhaps, it is the cost factor. Why spend more than a few dollars for a good high stability anode resistor?

Now you know that my views are not unbiased.

Mohan
 
Tonu,

the Lundahl anode chokes are 1st choice. The value you have chosen should do fine.
My buddy Thomas Mayer (Vinylsavor) uses them and is very happy and i decided to use 4 of them in my fully differential preamp.

They do one thing: they present a very high, almost infinite load to the anode. So the tube runs at gain=µ. They do another thing: DC-wise they almost short the anode to its supply. In a differential circuit this makes enormous sense as you can get DC-coupling almost for free and not even the PS cap acts as hidden coupling cap. The well-defined DC potential of the anode gives a very stable biasing of the following stage's grid.

The first thing can be accomplished using a CCS, the 2nd not.

Sonically an anode choke has much of an OPT and seems to sound friendlier than a CCS.

My sonic prejudices are exactly inverse to Mohan's :), i have done much cap testing and listening and much more prefer how chokes and trannies influence sonics.
 

Brett

Member
2002-01-07 6:02 pm
D'oh

I only saw them again late last night when I was 'thought experimenting' a couple of projects, and really should have been in bed. I do recall thinking how do they get 4000H out of them?

Sorry. Consciuosness before posting next time :D
 
Brett and all,

i frequently read concerns about Lundahl prices. IMO the price/quality relation of the Lundahl stuff is unbeatable.

I am not affiliated with Lundahl however, just convicend about their products.

There are some model numbers from Lundahl however which work not as terrific as the best ones ( best ones being LL1667/8, LL1660, LL1635, LL7901/2/3).
 

Brett

Member
2002-01-07 6:02 pm
Hi Bernhard,

I have used Lundahl transformers before from their Pro range, mic and some line drivers, and have no doubts about recommending them. Very fine product at an excellent price, better than all the alternatives I've looked at such as Hammond, Bartolucci ($$$), Plitron ($$$), Handwound and the Japanese (big $$$) iron. They are even cheaper then the local winders can do. My mistake re the choke, the S&B being half the money but not equivalent, was merely a suggestion for Tonu perhaps to save some money. I find most diy-ers want the best, but try to do it as cheaply as possible.

What got me back into tubes after a long hiatus, was Lynn Olson's Amity: such an elegant cicuit, but it's high performance is very dependent on the transformers. I have all the tubes and parts for them, but not the Lundahls, as I can't see the point in having 20W with 105dB+ speakers. I'm now building something smaller based on triode 6BQ5s, but unfiortunately I will have to slum it :)D :D) and use Magnequests as Lundahl do nothing suitable. Pity, they were my preference. The other amp I looked at was Allen Wright's PP1, as I am part way throught an RTP, using LL1663's. Again, no need for 12W, and I like 6BQ5s better than 6CA7s. Allen is a great designer who's recognition nowhere near matches his ability.

Cheers
 
Brett,

concerning Japanese Tango and Lundahl,
there is a vital common technical property.
Both use C-cores with 0.1mm thick sheet metal for the core.

Tango pots, Lundahl not. Tango is $$$$$$. Lundahl is $$.

Why not ask Per Lundahl if he could provide a 8k:8Ohms PP OPT? maybe he agrees, i certainly would join the order as i want to try out an amp using EL84 / 6BQ5 myself; I estimate this tube as one of the best output tubes ever made. And it han be bought cheap.

Amity:
great design. From listening experineces made with other IST-coupled amps, i would tend to prefer it to Allen's amp. I listened to Allen's amp at his place, at Aarhus 2000 and i also had it borrowed from him for 1 or 2 weeks. This amp had a more advanced circuitry that his PP1C schematic describes and if you have read my other posts conmcerning PP power amps, you can guess what that imporovement was. It is a wonderful amp.

However, i decided to combine that improvement with IST coupling and certainly not a cascode as amplifier/driver stage. A super-beefy differential pair of 6900 as input amplifier, a differential pair of 71A driving a differential pair of AD1 via an LL 1635. And the OPT is a Tango XE-45-5. Let's see how this comes out and whether i can handle the noise problem created by using DHTs and whether my transformer-loaded junk can compete with Allen's "elegant design". :)
 

tõnu

Member
2002-01-07 11:52 pm
thaks to all +load question

OK.I go on Lundahl LL 1668/25mA 100H.

I plan with LL 1668/25mA 100H loaded 5842,
AN 2,2uf copper foil paper in oil (have pair)in output drive Sovtek 2A3 in ´´pseudo´´45 condition.
What will be the ideal load for this driver stage?
Is it good idea try grid choke for that? If yes, then what value is the best?

Tõnu