I tend to think 'shade', but I suspect it is 'shard' as in a shard of glass.
Since Otto H. Schade was German, the correct way to pronounce his surname would be the way Germans pronounce it I suppose (incidentally there's a noun 'schade' in German language, you really ought to check out what it means
). It's "shar-deh" (trailing letter of each syllable is silent).
Schade merely explained to the engineering world the new RCA 6L6.
He may even have designed the darn thing, I don't know...
Somehow in the process, he accidentally or purposely explained the
physical causes and effects that create a Triode's internal property
of Mu. And how to fake it externally for a Pentode strapped Pentode.
The man was pure genius.
He may even have designed the darn thing, I don't know...
Somehow in the process, he accidentally or purposely explained the
physical causes and effects that create a Triode's internal property
of Mu. And how to fake it externally for a Pentode strapped Pentode.
The man was pure genius.
Do you mean he invented an inverting amplifier with parallel feedback by voltage?
Speaking of 6L6 and successors, they are good for PP, but for SE even Shade can't help them. But DIYers continue stepping on the same rakes again and again...
Like Sade?
An externally hosted image should be here but it was not working when we last tested it.
Why is it a pity? Do you prefer degeneration or 2 stage feedback?richwalters said:
Shade is a nice way of doing single stage feedback without adding another capacitor, although in hindsight it's a simple concept (but one to implement carefully).
Sure, why not?
But in case of "plate to plate" there will be 2 devices in a FB loop path; in case of "plate to cathode" there will be 3 of them. Beauty of Shade is in the shortest path in parallel with existing Miller's one, as I explained before in my message.
So this discussion went to Schadeland. Maybe this after all is the best way to "triode-strap"
.
Apologies for diverting the thread to Schade, I merely wanted to bring up another (cheaper) option.
(I got originally interested in Schade after reading about Alex Kitic's RH84 and later the RH807 but he stated another reason for sounding good: the magnetic delay introduced in the output transformer).
I like the Schade FB very much because it seems that tube rolling of the output tube has not the major impact that it has in other designs. The different designs (EL84, 6V6, 6L6, KT66) all have a similar sonic performance as reported by users.
Therefor relative cheap tubes can be used.The 6L6GC-STR is a very tough tube (same as the 807) and it is no surprise that it has survived this long (IIRC since 1934 or 1936) and that the guitar players like it: Those people continiously overdrive their tubes to get some particular distortion that they fancy.
Hope the thread goes back on track. I have never tried it but as a pentode I found the 6146B extreemly linear in amateur radio service (especially when run at 900 - 1050V whcih are quite dangerous voltages). Unfortunately it suffers from a fragile g1: RCA had to downrate the grid current to 1.5mA.
Have read somewhere on some Australian website that you can bias a 6V6 in such a way that it will sound like the 300B (but with a lot more power). I do remember it involved some ordinary transistor on the input (and I did not want silicon in a tube amp) but that may be another avenue to follow up on.
Hope you find the answers that you are looking for,
AM
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Pete Milletts magical red board seems to work well using sweep tubes and Schade. I have succesfully achieved over 10 times the power output that Pete intended with good numbers and good sound. And yes I sky wired mosfets in between the driver and output stages for an experiment. I noted that the unmodified red board was already dipping into A2 before I added the mosfets (output grids went to +15 volts). The initial experiment revealed more power output at low B+ voltages (400 volts), but the amp broke into oscillation as I cranked the power supply blasting the mosfets into next week, ending the experiment. No further experiments have been performed on my red board (other than restoring its life), but I have recently acquired a bunch of 35LR6's for more experiments.
There has been considerable debate about the use of triodes VS pentodes with Schade feedback. Petes red board was intended for 6CB6 pentode drivers. Fortunately for us adventuresome experimenters there tubes available with from 1 to 5 grids in them that all share a compatible pinout. Of course I have stuffed about 20 different driver tubes and a dozen different output tubes through my board. Yes there were a few outstanding combinations that worked great, but the trends were NOT in favor of triode or tetrode drivers. Pentodes were generally better, but what is in my board now? A BEAM HEXODE, the 6GU5 has been in the board since I stuck it in there. Lower measured distortion, and live dynamic sound follows the driver tube regardless of which output tube is used. Why? I dunno!
The thread was about a "most linear triode strapped pentode". As we saw early on there are many different opinions on this, but we have also learned that there other ways to achieve this than simply wiring the screen to the plate. For many tubes (like sweep tubes) the screen = plate connection is simply not an option. Trust me I have blown up enough of them to understand this. Schade is a viable and worthwhile option, if not the only option with some tubes. If nothing else, this opens up a wider choice of "triodes" with more power capability for a low price. We may still disagree about how to wire things up, but that will always be the case in this hobby.
This is sorta what I was goin' on about earlier.
Nother StOOpid way to abuse Schaded Mu=1?
OK, no Pentodes today. Special exception... why?
I tell you my deranged probably wrong thinking...
Keep screen current out split maybe mo important.
Bases leak current too, but not so much as screens.
Low phase shift in the loop mo import than having
insulated gate. J1 + M1 not in loop, gates here OK.
Keeping Schade FB current out the split important
too. V2a heater-cath might be kinda high, Q2 better.
Nother StOOpid way to abuse Schaded Mu=1?
OK, no Pentodes today. Special exception... why?
I tell you my deranged probably wrong thinking...
Keep screen current out split maybe mo important.
Bases leak current too, but not so much as screens.
Low phase shift in the loop mo import than having
insulated gate. J1 + M1 not in loop, gates here OK.
Keeping Schade FB current out the split important
too. V2a heater-cath might be kinda high, Q2 better.
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No indication Schade ever took credit for that.
In that "white paper" / advert for the 6L6, the impression is that he was being a bit sly, in advocating the use of local NFB. While the 6L6/807 boasts some impressive THD figures, what isn't mentioned is the high level of h3 and higher order harmonics. In a PP final, these can sound quite nasty when running open loop. Feeding back the 10% Schade mentions helps clean up that nastiness.
I've also found that 6BQ6GTBs, though putting out more THD (2.9% v. 1.8% for the 807) it's mostly h3 with a trace of h5. Open loop, 6BQ6s tend to sound overly "aggressive" or "edgy", but without the same pentode nastiness. The design I did with 6BQ6s didn't include local NFB, just gNFB to take the edge off.
Hey Amadeus,
Don´t know why you took my remark as critique? Had nothing to do with you, it was about the interesting discussion that came up after you post.
It might after all be like I stated, that Schade is better than triode-strapping.
If you by Schade mean RH I get your point as they all have the same unsuitable driver. This is probably coloring so much, making everything sound the same.
So go ahead and build a real Schade, you´ve got the tools. Good luck!
Don´t know why you took my remark as critique
? Had nothing to do with you, it was about the interesting discussion that came up after you post. It might after all be like I stated, that Schade is better than triode-strapping.
If you by Schade mean RH I get your point as they all have the same unsuitable driver. This is probably coloring so much, making everything sound the same.
So go ahead and build a real Schade, you´ve got the tools. Good luck
!
Thanks Lars - I googled 01N100 and found this one:
N-Channel, Enhancement Mode
what a difference a little D makes
N-Channel, Enhancement Mode
what a difference a little D makes
triode-strapped pentode
The terms Simple and Simplistic have been trademarked. “Cheap Basic SET” is trademarked by DualTriode.
If the goal is not to achieve the absolute maximum watts but to build a “Cheap Basic SET” can we push the plate voltage (also cathode current) of a triode-strapped pentode above the published 12 watts of a 6BQ6GTB? I too have a boatload.
Crowhurst wrote about pushing The G2 voltage for audio application as audio is easier duty than TV sweep.
I am thinking of output watts in the 2 to 3 watt range. We do not need to let out the magic smoke. This could be cheap DIY fun with an amplifier in the power output range of a RCA 45.
DualTriode
All just for Fun!
The terms Simple and Simplistic have been trademarked. “Cheap Basic SET” is trademarked by DualTriode.
If the goal is not to achieve the absolute maximum watts but to build a “Cheap Basic SET” can we push the plate voltage (also cathode current) of a triode-strapped pentode above the published 12 watts of a 6BQ6GTB? I too have a boatload.
Crowhurst wrote about pushing The G2 voltage for audio application as audio is easier duty than TV sweep.
I am thinking of output watts in the 2 to 3 watt range. We do not need to let out the magic smoke. This could be cheap DIY fun with an amplifier in the power output range of a RCA 45.
DualTriode
All just for Fun!
there's something I do not understand here. According to some datasheet I've found, it's Va(max) is "only" 750V. How could you run it at 1050V?
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