SE-OTL

[Ali Tait]

Do not some valves use the anode as the getter?

[Andrew]

I wonder if they are self gettering then?

[Nick]

Yep, maybe that's the case, 6s22s doesn't have a getter flash visible either.

[Mike H]

Have you seen the schematic?

Er, no.

Yes the output is capacitor coupled, Bruce's argument being that it is 'a thousand times less damaging than output transformers'.

Ummm ~ I would have thought better than DC coupled

Don't get DC with transformers either so don't quite understand that

 

[Will]

I spy a getter its above the anode under the pip unless its a flying-saucer

.

[Ali Tait]

Yes,saw that too.Wonder if it's the top of the anode that's the getter.

[Ray P]

Have you seen the schematic?

Er, no.

Yes the output is capacitor coupled, Bruce's argument being that it is 'a thousand times less damaging than output transformers'.

Ummm ~ I would have thought better than DC coupled

Don't get DC with transformers either so don't quite understand that

Mike, I'll have to think of a way to share the principles of the schematic; I'm not sure it is appropriate to just post it as it is Bruce's IPR and the source of part of his livelihood.

With respect to the output capacitor, there has been some discussion on this on the TS discussion board. One of the key tenets of OTL designs is to avoid the compromises to the signal (music) created by any output transformer, however, with the SE-OTL the nature of the design requires a cap to protect your speakers but that this compromses the signal less than a transformer, best of all would be direct coupled. I think there is a certain irony that in the discussions people jump to negative conclusions about having an output capacitor but don't seem to have any concerns about having one between the stages of their amplifiers. As I say, the proof of the pudding will be in the eating.

Oweston is really difficult for me given my location but if I could make it along I would be happy to bring the SE-OTL along, though whether 1.5watts is realistic in that environment I'm unsure.

Ray

[Ali Tait]

It would be fine on, say, Steve's very sensitive OB's.We've had amps of less output than that rattling the windows! Great if you could make it,I'd be interested in hearing the amp.

[Andrew]

I spy a getter its above the anode under the pip unless its a flying-saucer

.

OK, I can buy that, but why no flash

[Nick]

Maybe by staying on the plate, the heat from the anode is conducted to it activating it?

[Mike H]

@ Ray I totally understand about the schematic, no you shouldn't post it if the guy wants it kept secret (That's the problem with kits! The world and his dog are off to brew their own rather than get the kit if they get a hint of how it's wired up )

From the desciption it sounds like 4 x valves in parallel, as cathode followers? then "something else" underneath to complete the circuit, a current source?


The second thing is just about the phrase used, "thousand times less damaging to your speakers than a transformer", which seems such a bizarre thing to say.

I'm just looking at it purely from the 'electrical safety of speakers' point of view, not what it sounds like


 

[Ray P]

Mike, maybe if I could make Oweston I could bring the manual with me so you can check out the schematic. I'm visiting the hospital in around 10days and hope to get the OK to resume driving soon so if physio goes well I might manage the long journey.

I was paraphrasing Bruce Rozenblit's 'thousand times' statement from memory so may have got it a little wrong but the context was purely about sound quality, apologies if I didn't provide that context.

Ray

[Mike H]

In which case, that would make more sense

Okey-dokey then.


Sure nuff if you can make it to Owston I'd be interested to have a look.

[Nick]

Without truing to be too agumental:

Bruce's argument being that it is 'a thousand times less damaging than output transformers

He does have a bit of a habit of making sets of proclamations about what is good or not, and they always seem to match exactly what he is selling though.

I guess you have to weigh up the damage done by the transformer against the result of asking a valve to work into a load that is entirely against its design. And then you have to question the effect of all the additional work that needs to be done to make a valve drive a 8 ohm load.

I think both sides have merit. It could all be a lot simpler if someone would make a 200 ohm loudspeaker though

Hope you get a chance to bring it Ray, I have heard a couple of the BR amps, and they both were very good.

Is this amp using this sort of shape output stage?

[Mike H]