25W Single Ended Hammond 193V Choke Loaded 2SK180 L'Amp

[analog_sa]

There seems to be a pronounced vacuum of high quality chokes for this type of currents. Using a dubious PS grade choke appears optimistic.

 

[nicoch58]

lundahl can be good ,I'm sure Per can do a custom work on amorphous core too

 

[jotom750]

Would these not be suitable ?
www.farnell.com/datasheets/2625615.pdf
Air cores are nicer, but much more expensive.
Maybe speaker crossover parts is an option.

 

[analog_sa]

Not sure if Lundahl has a choke with a sufficient current rating. Their amorhous chokes are on pitifully small cores, so this is probably not a good option. It is my belief that all things being equal an amorphous core needs to be substantially larger.

 

[analog_sa]

Air cores will certainly dissipate a substantial amount of heat, be large, weigh a ton and be very expensive. A layered custom wound choke on a good core seems the best option.

 

[analog_sa]

Of course, if one is prepared to go all out with a custom choke it will make more sense to go for a step down transformer, get rid of the coupling cap and obtain a decent damping factor.

 

[jotom750]

I made five of these a few years ago for the PS of my Aleph 5.
3.2mh 0.65 Ohm
I would buy off the shelf items today though as it was a bit of a chore to do. The ones I pointed to earlier are about £15 each.

 

[analog_sa]

I made five of these a few years ago for the PS of my Aleph 5.
3.2mh 0.65 Ohm

Around 50mH seems to be the minimum for a full range amp. 100mH is better.

 

[jotom750]

I'm talking about a CLC PSU. I now no longer know what you are referring to.
Anyway, good luck with your chosen option.

PASS LABS CLONE - Aleph-5 PS-X2 Amplifier Power Supply PCB

 

[analog_sa]

I'm talking about a CLC PSU. I now no longer know what you are referring to.

Post #120 raised the question whether a resistor may be preferable to a choke as a load.

 

[Itsmee]

HI Gen you preferred R to choke ?

I was going to ask Ben & generg the same question regarding a constant current load

 

[Ben Mah]

Ben, have you tried comparing THF-51 vs 2SK180 and Hammond 193V common drain amplifiers?

No.

With common source, I don't think I noticed much difference between the two. I would guess it would be the same with common drain.

The noticeable difference was between common source and common drain.

 

[Ben Mah]

17dB is a gain of a little over 7 ....

You're right, my mistake. I confused voltage gain with power gain.

 

[Ben Mah]

I was going to ask Ben & generg the same question regarding a constant current load

I have listened to my BAF2015 THF-51S (CCS/Mu follower/common source) and the choke loaded common source 2SK180/THF-51S and I did not notice any of what I would consider significant difference in sound. But that is me, and someone else may notice differences.

One practical disadvantage of the CCS/Mu follower is the much higher V+ required. That means higher voltage power supply with higher voltage capacitors and transformer, and higher power dissipation necessitating much more heat sinking.

On another note, I was thinking of a name for the follower version since it is a keeper for me. Along the lines of the Michael Rothacher's MoFo, it could be a ToFo. But then it could be "A Fokin Amp".

To end this on a sunny but cool morning, here is my favorite Mr. Rogers interview:

Mr Rogers interviews a bass player - YouTube

 

[GnuB]

Around 50mH seems to be the minimum for a full range amp. 100mH is better.

Hammond has some offerings that might work:
Part No. Inductance mH D.C. Current Resistance Weight
(Millihenries) (Amps) (Ohms) (lbs.)
195R10 50 10 0.165 26 ~$177
195S4 70 4 0.6 - ~$68 each
195T10 100 10 0.42 35 ~$300 each

Looks like a comparison of the 193V and the 195S4 could be interesting.

Ben, if you think it might be worthwhile and you're up for testing, measuring, and your wonderful reporting, I'll split the cost of a 195S4 (including shipping) with you.

 

[GnuB]

(Sorry about the lousy formatting)

 

[analog_sa]

The Hammonds are wound without any regard towards minimising parasitic capacitance and on the cheapest cores money can buy. I have a fair idea of the the quality of their tube transformers and chokes and would be very surprised if the high current parts are much better.

The Lundahl PS chokes otoh are made using the same winding geometry as their plate chokes.

 

[pinholer]

I, too, like the sound of the my 2SJ28 source follower amp compared its previous iteration in common source mode. It is CCS loaded, not choke though, but it is driven by a Hammond choke loaded 2SK82 voltage amp.

Like Ben said, the sound to me is cleaner, yet still sweet. I also use a Luminaria preamp, so it has enough 2nd order harmonics and the source follower amp's low harmonics adds a little bit, but not too much as compared to the common source amp.

I think that the low impedance of the SITs allow the use of lower inductance chokes and their capacitances do not affect the signal as much.


I just started building a Hammond choke loaded 2SK180 follower amp and that will provide more data.

 

[plasnu]

The size of choke really matters for low frequency response. More information is here.

Small Choke
All SIT 50W+ Single Ended Amp (beta)

195T
All SIT 50W+ Single Ended Amp (beta)

 

[Ben Mah]

Hi GnuB,

I am not up to taking my amp apart to try a different choke. Sorry.

Looking at the numbers, the 193V is 150mH, 3A, 1.0 Ohm DCR for $89 whereas the 195S4 is 70mH, 4A, 0.6 Ohm DCR for $68.

The higher inductance of the 193V will result in better low frequency response and lower distortion. Perhaps in real life it may not be noticeable. But in diy, I would go with the 193V for the extra $21 each.