Choked Singing Bush ..... special one for Purists and Masochists

[Zen Mod]

OK, this one long in making
I mean - have pcb files and everything for some time, basic functions confirmed but - as is my nature - never working by plan

Anyway - why Purists and Masochists?

List of reasons:

1. you really need properly made high quality choke; 100mH, no more than 0R5 winding resistance, declared for 3A5dc (big Tokin) or 2A5dc (small Tokin)

2. PSU - bummer - heavy filtration; CLC, or C then cap multiplier followed with heacy C cell, or fat switcher ..... most likely also followed (by choice or necessity) with some sort of high-pass filter and followed with fat C cell

3. this time ( even if evidently intended as option) - no Schade Mos Puck; simply too high Rout of part itself (even if normally or even heavy Schaded), resulting in uberfunny transfer function and THD way too high; now - with all my crummy chokes (yes, Plethora of them but all crummy) that's the situation; there is a possibility that Schaded option is viable and worthy if adequate quality choke is used, but that I can't confirm, nor I intend to purchase it, in any way or arrangement

4. looking at all above - simply - cost; you gain something with lesser volts involved (vs. say "regular" Singing Bush) thus lesser heat and lesser Donut and lesser voltage caps and lesser Aluminum in sinks...... but then main choke, PSU choke, yadayada....

5. yes, OPT is an option, for both shown iteration ( Big Tokin, small Tokin), don't have it, easy to try if you have one; same conditions as with choke - do not even try with cheaply made Iron

there are few more reasons, worthy of this list, but I'm lazy to think now .....

Anyway, usual set of introductory eye-pleasing files:

 

[Zen Mod]

dunno is that age or what, but in last time I'm often forgetting to take phone (cam) with me in workshop, so again no proof is in da pooding pics; meaning - No Porn, No Glory for Mighty ZM, but whatever

at least these few pics I have from assembling pcbs, few days ago

will take few pics of small version tomorrow and post

 

[Zen Mod]

and, just to amuse you - pic of worthy switcher;

at least that I have

good enough for small version ( small Tokin), in case that I ever stumble on pair of worthy chokes

 

[Zen Mod]

now, graphs

Big Tokin iteration, THF 51S used

rail 32Vdc-ish
Iq 3A2, rock-ooking-stable in entire power range; current mirror approach works as charm

crummy choke - 80mH, Rdc is 0R75, biiiig chunk of EI Iron, but there is no gap in core; few microwave xformers I have butchered to choke duty are even worse, by measurements

for 1W@8R, means 2V83rms, input signal is 285mV; thus gain is roughly 10V/V, 20db

load is 8R, didn't even tried 4R load, no go with this choke

again - weed down is due to used choke (no gap, lousy wound, even if thingie is originaly hospital grade mains autoformer (230 to 115, 1KW5)

anomaly around 20K is due to ...... well, really need to resort to proper connectors on in/outs of my interface box

conclusion - don't look too much on numbers - ignore weed, look at Spectra and compare different levels; if you follow list from post #1, both iterations of this amp are Full Bliss candidats - not FiFi realm, but Best Ganja Around realm

had one channel in listening today ...... heck - even if I find just one proper choke, will make one channel for Mono System :cown:

 

[Zen Mod]

small Tokin iteration, 2SK2087C used

rail 26Vdc-ish
Iq 2A1, rock-ooking-stable in entire power range

same crummy choke

for 1W@8R, means 2V83rms, input signal is 244mV; thus gain is roughly 11.6V/V, 21.28db

load is 8R, didn't even tried 4R load

same conclusion from post above applies

 

[Zen Mod]

forgot to say - AntiBigBadaBoom relay circuit works as a charm - practically xeroxed approach from Papa's recent concoctions ( relay shorting speaker while output cap is charged or discharged)

during power up sequence relay is normally shorted and action is delayed by few secs; during power off sequence, relay is immediately closed

 

[rickmcinnis]

The gigantic HAMMOND 195T10 meets your requirements. Only weights 35 pounds. I would not think it is wound like a plate choke. Could something like this work? One would hope it might work well at $347.00.

Two tantalizing evolution. Thanks.

 

[SPWONG]

How about HAMMOND 195T5? It is much cheaper but the winding resistance is 0.64 Ohm. Thanks.

 

[SPWONG]

Also LUNDAHL LL2773/3.5A, it has 95mH with 3.5A capacity and the winding resistance is 0.22 Ohm. Thanks.

 

[analog_sa]

Also LUNDAHL LL2773/3.5A, it has 95mH with 3.5A capacity and the winding resistance is 0.22 Ohm. Thanks.

Winding resistance for 95mH is 0.44ohm.

 

[Zen Mod]

one thing is certain - every decent choke will work, better than those crummy I have

though, physics is physics - regarding bass extension - see graphs and just crunch some numbers ..... more mH, linearly better bass than shown

 

[rickmcinnis]

This one proves just how much a purist/masochist one might be. It is intriguing as hell but I think Lazy is more within my purist/masochist envelope.

 

[flocchini]

I'm a masochist.

 

[von Ah]

I sit squarely on the Lazy side when daydreaming about the Cambrian explosion of ZM projects of late. If only there was one with 2SK2087C, no pricey chokes or input Tx, and no SMDs...

 

[Zen Mod]

existence of modern Toshiba smd JFets specifically made for audio, is one of factors allowing these amps to be made

I'm personally sitting on small stash of old Toshibas and then some more of non-Toshibas, but that quantity is nowhere enough for even mild interest of Greedy Boyz

however.... in case that I was going to make any amp for my personal use only (hardly, have already too many of them), be sure it would be made with toobz as dominant parts


anyhow, level of my fun is much greater this way - I enjoy making them, even if I will end with just few

good thing is - it seems I already made ones without input Tx, also ones without need for pricey chokes .......... and if you want one even without smd ...... just wait for me getting bored (enough)***

in a meantime, knowing that all, if gotten from me, are having all smds already soldered

I prefer that way, easier than packing small bugz in plastic bagz and sending

***bummer is - I'm getting used on smd - so using them for some other convenient positions ........

 

[von Ah]

good thing is - it seems I already made ones without input Tx, also ones without need for pricey chokes .......... and if you want one even without smd ...... just wait for me getting bored (enough)***

in a meantime, knowing that all, if gotten from me, are having all smds already soldered

 

[Zen Mod]

 

[claudio52]

The THF 51S common source graphs and the THF 51S Warbler common driver graphs appear to show more triode-like behavior in the CS. In that case just before clipping (2H = 3H), the power is 35W /8R versus 10W/8R in the CD. As with triodes, clipping never seems to occur.

 

[Ben Mah]

THF-51S common drain is capable of more than 10W/8R at clipping. As ZM had mentioned, his testing was limited by the limits of his test setup. Common drain has no voltage gain so the test signal needs to be high voltage to test the amplifier to its limit. The THF-51S Warbler 10W/8R test may have been pushing the limit of the test signal, not the limit of the amplifier being tested.

 

[Zen Mod]

yup