"My amp is not as a version of the ciufioli 8.2 the only similarity is that is uses a output stage connected the same way, the performance of these 2 amps are quite different as what I understand."
Aha! That was the source of my confusion (I think) - I assumed that your amp was basically the same as the 8.2 because of the schema with voltages on it. I thought I remembered reading that
the 8.2 wasn't sonically satisfying to at least one guy who built it.
Is your schema available with component values?
mgreene@bnl.gov
Thanks
Mike
Aha! That was the source of my confusion (I think) - I assumed that your amp was basically the same as the 8.2 because of the schema with voltages on it. I thought I remembered reading that
the 8.2 wasn't sonically satisfying to at least one guy who built it.
Is your schema available with component values?
mgreene@bnl.gov
Thanks
Mike
Hi,
To my mind and with the restrictions of all SE OTLs, this is a far better idea than say the SRPP stage used by Philips for their 800 Ohm speaker.
Naturally all the gain has to come from the previous stage but that can't be a major problem.
In fact I think it was me suggesting the idea of using the WCF as an SE OTL output stage in this thread in the first place.
What appeals to me is that you can get reasonable power and low Zout with just a few tubes.
Cheers, 😉
To my mind and with the restrictions of all SE OTLs, this is a far better idea than say the SRPP stage used by Philips for their 800 Ohm speaker.
Naturally all the gain has to come from the previous stage but that can't be a major problem.
In fact I think it was me suggesting the idea of using the WCF as an SE OTL output stage in this thread in the first place.
What appeals to me is that you can get reasonable power and low Zout with just a few tubes.
Cheers, 😉
Hi,
Absolutely, Tubetvr and myself were asked for advice on the 8.2 by a couple of members and they built it successfully.
As far as I'm concerned the crossfed outputstage is an elegant way to reduce Zo and would be a good idea to pursue in OTL design.
The main problem with the Circlotron is that you need twice the amount of components and PS to arrive at a workable result and the Zout still is too high compared to other topologies.
Cheers,😉
Absolutely, Tubetvr and myself were asked for advice on the 8.2 by a couple of members and they built it successfully.
As far as I'm concerned the crossfed outputstage is an elegant way to reduce Zo and would be a good idea to pursue in OTL design.
The main problem with the Circlotron is that you need twice the amount of components and PS to arrive at a workable result and the Zout still is too high compared to other topologies.
Cheers,😉
Hi Frank,
"The main problem with the Circlotron is that you need twice the amount of components and PS to arrive at a workable result and the Zout still is too high compared to other topologies."
But what about the comparative sound? Noting that I have never heard 6C33 OTL.
Mike
"The main problem with the Circlotron is that you need twice the amount of components and PS to arrive at a workable result and the Zout still is too high compared to other topologies."
But what about the comparative sound? Noting that I have never heard 6C33 OTL.
Mike
Hi,
I think good sound can be had from a Circlotron but on paper at least it presents some major disadvantages that seriously work against it when facing real world speakers.
I never heard a 6C33-C OTL myself but having toyed with 6336As I think the 6C33-C are:
a) best suited for OTL of all available tubes.
b) too cheap to pass on considering they cost as much as a 6AS7G except for the odd sockets.
c) If I were to build a new OTL I'd use the 6C33-C without a doubt in my mind.
Cheers,😉
I think good sound can be had from a Circlotron but on paper at least it presents some major disadvantages that seriously work against it when facing real world speakers.
I never heard a 6C33-C OTL myself but having toyed with 6336As I think the 6C33-C are:
a) best suited for OTL of all available tubes.
b) too cheap to pass on considering they cost as much as a 6AS7G except for the odd sockets.
c) If I were to build a new OTL I'd use the 6C33-C without a doubt in my mind.
Cheers,😉
Does anyone know whether Bruce's design the T8 is based on futterman's design since I am a bi confused here, and if yes, can one implement the technik's variation ie cross feeding the power stage as in other designs to achieve lower impedence ?🙁
Hi,
Yes, it is.
No, you can't just do that. You'll need a redesign of the frontend of the amp for that at the very least.
If I were you, I'd either build the T8 as is or go for the cross fed Ciuffoli with individual bias supplies.
Just my 2 cents, 😉
Yes, it is.
No, you can't just do that. You'll need a redesign of the frontend of the amp for that at the very least.
If I were you, I'd either build the T8 as is or go for the cross fed Ciuffoli with individual bias supplies.
Just my 2 cents, 😉
OTL but not OCL!
Here´s a conceptual schematic of what I´m rambling about.
IF I´m going to build something like this (likely, since I have most of the parts in the junkbox) it will be for the purpose of driving the mid/high section in my dipoles.
Because of this the output coupling caps can be quite small, so film types or PiO´s are not out of question.
Here´s a conceptual schematic of what I´m rambling about.
IF I´m going to build something like this (likely, since I have most of the parts in the junkbox) it will be for the purpose of driving the mid/high section in my dipoles.
Because of this the output coupling caps can be quite small, so film types or PiO´s are not out of question.
Attachments
Hi,
That should work.
Have you calculated the Zout?
Personally I'd use both sections of the 6AS7G iso the FET, but that may require some matching to balance nicely.
This type of circuit could also do away with the coupling cap at the output but the feedback cap will have to stay.
So that may just as well remain an exercise of theoretical application.
Cheers,😉
That should work.
Have you calculated the Zout?
Personally I'd use both sections of the 6AS7G iso the FET, but that may require some matching to balance nicely.
This type of circuit could also do away with the coupling cap at the output but the feedback cap will have to stay.
So that may just as well remain an exercise of theoretical application.
Cheers,😉
No calculations, just a conceptual schematic.
I think the Fet might be a good idea, (unless someone´s allergic to silicon😀 ) since it requires a lot less input signal compared to a 6AS7, which means we can use a smaller resistor on top of the cathode follower. Correct me if I´m wrong here.
A bot of NFB might be useful to tame the output impedance, but OTOH; open baffles might like a bit of output impedance?!?
I think the Fet might be a good idea, (unless someone´s allergic to silicon😀 ) since it requires a lot less input signal compared to a 6AS7, which means we can use a smaller resistor on top of the cathode follower. Correct me if I´m wrong here.
A bot of NFB might be useful to tame the output impedance, but OTOH; open baffles might like a bit of output impedance?!?
Hi, fuling -
Perhaps you could get enough in phase gain by cathode driving a, say, miniature triode from near the +150 and a higher supply to allow a more reasonable value for the WF upper plate resistor so as to lose the MOSFET. Maybe you could even manage the grid bias connection for the gain tube by splitting the WF upper plate resistor and filtering the signal component out.
I'm afraid I'll have to get shots now for audio silicosis
Perhaps you could get enough in phase gain by cathode driving a, say, miniature triode from near the +150 and a higher supply to allow a more reasonable value for the WF upper plate resistor so as to lose the MOSFET. Maybe you could even manage the grid bias connection for the gain tube by splitting the WF upper plate resistor and filtering the signal component out.
I'm afraid I'll have to get shots now for audio silicosis
Let´s see if I got this one straight:
The ECC88 amplifies the signal that develops across the current sensing resistor so it can drive the lower 6AS7, right?
Clever, I must say.
Still, this means I have to double up the number of output tubes since half of them gets "lost" in the active load.
Since I´m not "afraid" of Mosfets I think I´ll go for one in the lower position, partly because I have only four 6AS7´s at home and my filament transformer can´t handle anymore.
So far this is only a "for fun" project and I don´t want to spend any money until I´ve seen some positive results.
Who knows what it develops into?
All I need now is a rainy day🙂
The ECC88 amplifies the signal that develops across the current sensing resistor so it can drive the lower 6AS7, right?
Clever, I must say.
Still, this means I have to double up the number of output tubes since half of them gets "lost" in the active load.
Since I´m not "afraid" of Mosfets I think I´ll go for one in the lower position, partly because I have only four 6AS7´s at home and my filament transformer can´t handle anymore.
So far this is only a "for fun" project and I don´t want to spend any money until I´ve seen some positive results.
Who knows what it develops into?
All I need now is a rainy day🙂
Hi, Fuling -
That's correct. The output z trim might allow you to possibly achieve a damping factor more comparable to some global feedback amps, also. Don't know this for sure since I just sketched it up, but I don't know why it wouldn't work that way. If only half the miniature dual triode is needed for this (adjust plate resistor to match), perhaps the other half is all the input and driver stage you'd need. Could maybe even be a global feedbackless two tube (or three tube, if 6C33C's used) OTL then, if only one PP class a 6AS7G or 6336 meets the power requirement at hand😎
That's correct. The output z trim might allow you to possibly achieve a damping factor more comparable to some global feedback amps, also. Don't know this for sure since I just sketched it up, but I don't know why it wouldn't work that way. If only half the miniature dual triode is needed for this (adjust plate resistor to match), perhaps the other half is all the input and driver stage you'd need. Could maybe even be a global feedbackless two tube (or three tube, if 6C33C's used) OTL then, if only one PP class a 6AS7G or 6336 meets the power requirement at hand😎
Anybody interested in a low power dc coupled OTL using a WF output? It would have loop feedback and roll off to unity gain at dc.
Well, I was going to throw a schematic on line but it looks like that'll have to wait a while because one of our servers is down. Most of our SW licenses are networked and IT does a horseshit job of maintaining the servers here. Maybe I can do it from home over the weekend. Sorry.
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