It must have been, yes.
Do you perhaps know which one I mean?
Not even I would dream of a 25W SE OTL.😀
Do you perhaps know which one I mean?
Not even I would dream of a 25W SE OTL.😀
Hi,
A Futterman H3 with PL/EL519s as built by Aitos would come close.
Otherwise if you'd replace the 6AS7Gs in the BR GA OTL with 519s that would be similar as well.
If 25W is the target power I'd rather opt for a pait of 6C33-Cs but that's just me...
Cheers,😉
A Futterman H3 with PL/EL519s as built by Aitos would come close.
Otherwise if you'd replace the 6AS7Gs in the BR GA OTL with 519s that would be similar as well.
If 25W is the target power I'd rather opt for a pait of 6C33-Cs but that's just me...
Cheers,😉
Ok, thanks!
I´ll search for info on those as soon as I get some time.
My main target is low price, anything from a couple of watts and up would be fine.
Remember that this is just for fun, I´m only trying to introduce myself to the OTL world🙂
I´ll probably build something big and nasty when I have the time and money.
I´ll search for info on those as soon as I get some time.
My main target is low price, anything from a couple of watts and up would be fine.
Remember that this is just for fun, I´m only trying to introduce myself to the OTL world🙂
I´ll probably build something big and nasty when I have the time and money.
Tube matching ?
If I needed to run a pair of 6c33c-b tubes in parallel. How would
I go about matching the tubes? or would a pot with the wiper
connected to the b+ and the plates connected to each end of the
pot be an acceptible way to ballence the tubes. Or if I wanted
to run 12 6c19pi tubes in parallel is there some way to use unmatched tubes? In the case of the 12 6c19pi tubes could
I just use a 100 ohm cathode resistor on each tube.
Thanks,
Woody
If I needed to run a pair of 6c33c-b tubes in parallel. How would
I go about matching the tubes? or would a pot with the wiper
connected to the b+ and the plates connected to each end of the
pot be an acceptible way to ballence the tubes. Or if I wanted
to run 12 6c19pi tubes in parallel is there some way to use unmatched tubes? In the case of the 12 6c19pi tubes could
I just use a 100 ohm cathode resistor on each tube.
Thanks,
Woody
Frank,
I was reading another thread where you had a bit of an argument with another member (which was funny at some stages) where you see to imply that you prefer the GA BR circuit than the T8 (and now the ciuffoli 8.2). Care to comment on this?
I guess this follows the conversation we had before. I would really want to learn from your experience why you prefer the 8.2 than the t8?
this questions applies to any other members which may wish to comment.
I was reading another thread where you had a bit of an argument with another member (which was funny at some stages) where you see to imply that you prefer the GA BR circuit than the T8 (and now the ciuffoli 8.2). Care to comment on this?
I guess this follows the conversation we had before. I would really want to learn from your experience why you prefer the 8.2 than the t8?
this questions applies to any other members which may wish to comment.
Tube bias
using a res in the cathode of each valve would increase the output impedence.
The best way would be separate adjustable bias supplies to each O/P valve G1, and set for correct bias after half hour running.
This doesnt help with unmatched valves that may have slight differences in gain however, as only the standing current will be trimmed in.
using a res in the cathode of each valve would increase the output impedence.
The best way would be separate adjustable bias supplies to each O/P valve G1, and set for correct bias after half hour running.
This doesnt help with unmatched valves that may have slight differences in gain however, as only the standing current will be trimmed in.
Hi,
What I regret in the T8 is the lack of a tubed voltage regulator for the input/driver stages.
This can be added of course if you feel inclined to do so.
Also, I'm still not 100% convinced on how this Zener stack trick in the T8 actually works but that's probably more due to my lack of knowledge than anything else...😀
Other than that, I felt the monoblock 60W version I built on a par sonically with my own OTLs which I consider quite a compliment...
Beauty is in the eye of the beholder, n'est-ce pas?
While I had my doubts about the 8.2, having helped a couple of members with their problems forced me to look at it more closely.
It's both elegant and simple with a minimum of tubes in the output; less can be more it seems.
However, I'd recommend using individual bias for the output tubes as it's easy to implement and with such high transconductance valves such as the 6C33-C you're bound to have rather wide dispersions between them; this solves that problem to an extend.
Another problem solved is the output impedance, the achilles heel of all OTLs, which the crosscoupled phase splitter cuts to acceptable levels; again elegant and simple.
Moreover, since Tubetvr opted for the same solution after years of experimenting and still feels happy with his choice, I feel it's worth endorsing.
Cheers,😉
What I regret in the T8 is the lack of a tubed voltage regulator for the input/driver stages.
This can be added of course if you feel inclined to do so.
Also, I'm still not 100% convinced on how this Zener stack trick in the T8 actually works but that's probably more due to my lack of knowledge than anything else...😀
Other than that, I felt the monoblock 60W version I built on a par sonically with my own OTLs which I consider quite a compliment...
Beauty is in the eye of the beholder, n'est-ce pas?
While I had my doubts about the 8.2, having helped a couple of members with their problems forced me to look at it more closely.
It's both elegant and simple with a minimum of tubes in the output; less can be more it seems.
However, I'd recommend using individual bias for the output tubes as it's easy to implement and with such high transconductance valves such as the 6C33-C you're bound to have rather wide dispersions between them; this solves that problem to an extend.
Another problem solved is the output impedance, the achilles heel of all OTLs, which the crosscoupled phase splitter cuts to acceptable levels; again elegant and simple.
Moreover, since Tubetvr opted for the same solution after years of experimenting and still feels happy with his choice, I feel it's worth endorsing.
Cheers,😉
Nicos, Have you seen the comments from John Broskie and others to the BR patented circuit?, (That it doesn't solve the problem it is supposed to solve?)
My comment is: maybe it is even so that the problem that the BR circuit is supposed to solve can be solved, (or to a large extent eliminated) in other simple ways? Maybe in that case there could be other circuits that are better suited to solve other inherent OTL amplifier problems, (like reliability)?
Regards Hans
Frank and Hans thanks.
Frank, which circuit did you use for the 60w amp, the GA or the T8? In any case it is evident that BR on the t8 does try to cut some corners, perhaps to the detriment of sound quality.
Hans,
Where can I find Broskey's article?
Moreover, do you have any advice to offer on improving the ciuffoli, in addition to Frank’s brilliant individual tube biasing which has already been implemented by myself?
Frank, which circuit did you use for the 60w amp, the GA or the T8? In any case it is evident that BR on the t8 does try to cut some corners, perhaps to the detriment of sound quality.
Hans,
Where can I find Broskey's article?
Moreover, do you have any advice to offer on improving the ciuffoli, in addition to Frank’s brilliant individual tube biasing which has already been implemented by myself?
1)
Dear Sir,
I would submit that
1) until such time as you have actually built a pair of T8s and
2) auditioned them extensively
you are talking through your hat when speaking of "cutting corners" and "detriment of sound quality"! The "corner cutting" that BR employs (in actuality a series of very sensible circuit design parameters) is to insure longevity and safe operating points of the output tubes (valves), and to provide adequate headroom and output capability, all of which have a direct positive impact on sound quality. And, I might add, these measures also mean that the T8 does not have that nasty little tendency of destroying one's speakers at a moment's notice, as so many other OTL designs do.
This is unquestionably the finest pair of amplifiers I have had in my system, and I've been doing the "audiophile thing" for nearly forty years now. And I'm not the only one who thinks so--Stereophile gave the commercial version of the T8 a "Class A" rating for two years in a row.😀
Dear Sir,
I would submit that
1) until such time as you have actually built a pair of T8s and
2) auditioned them extensively
you are talking through your hat when speaking of "cutting corners" and "detriment of sound quality"! The "corner cutting" that BR employs (in actuality a series of very sensible circuit design parameters) is to insure longevity and safe operating points of the output tubes (valves), and to provide adequate headroom and output capability, all of which have a direct positive impact on sound quality. And, I might add, these measures also mean that the T8 does not have that nasty little tendency of destroying one's speakers at a moment's notice, as so many other OTL designs do.
This is unquestionably the finest pair of amplifiers I have had in my system, and I've been doing the "audiophile thing" for nearly forty years now. And I'm not the only one who thinks so--Stereophile gave the commercial version of the T8 a "Class A" rating for two years in a row.😀
THREE CORNERED HAT....
Hi,
Such as?
Seriously, an OTL amp is topologically not that different from 85% of all transistor amps out there.
If you feel paranoid about this you can always add a DC servo but I wouldn't.
Accidents can and do happen, OTL or not.
Oh, I fail to see any precautions in the T8 other than a pair of fuses against this imaginary tendency so I guess it ain't all that bad anyway...
As DIYers we can pretty much build what we like and how we like it...
This now ends the horror story....let's move on:
It was based on the GA design, the few changes to turn it into a monoblock with more than twice the output power are described in this thread...somewhere.
Found some pics taken by the proud owner:
Note the four corners in their full glory.😀
1)
Hi,
Such as?
Seriously, an OTL amp is topologically not that different from 85% of all transistor amps out there.
If you feel paranoid about this you can always add a DC servo but I wouldn't.
Accidents can and do happen, OTL or not.
Oh, I fail to see any precautions in the T8 other than a pair of fuses against this imaginary tendency so I guess it ain't all that bad anyway...
As DIYers we can pretty much build what we like and how we like it...
This now ends the horror story....let's move on:
It was based on the GA design, the few changes to turn it into a monoblock with more than twice the output power are described in this thread...somewhere.
Found some pics taken by the proud owner:
Note the four corners in their full glory.😀
1)
Attachments
His analysis of the BR patented circuit was in a response of an E-mail sent from a reader. http://www.tubecad.com/april_may2001/page33.html
It is my opinion that the Ciuffoli circuit is not optimised and the performance could therefore be improved by using other component values.
I have built my OTL using the same output coupling as Ciuffoli but have chosen to use a somewhat different driver arrangement, another difference is that I don't use any chokes in the output stage anode voltage supply but my amplifier is dead quiet anyway, (0.4mV hum and noise Pk-Pk) it took me quite a long time to get it right by arranging the grounding scheme and using good quality lytics in the power supply.
Regards Hans
Frank and Hans,
thanks
cbrodersen
1) When BR needs an attorney to speak/write on his behalf he will choose a real one. FYI he even admits cutting some corners in his book, AR when you take the time to read it.
2) When you read the whole thread then you will realise that I went through "your" arguments one by one and was indicated otherwise by more experienced DIYers, whom I appreciate their views more, being openminded.
3) the Stereophile argument does not make any sense to me and I would value the opinion of experienced DIYers more who have no commercial benefit out of all this.
4) Just because you have built the T8 that does not mean that it is the best sounding unit on earth, there is always room for improvement.
5) The value of this thread is to learn something, not to try to impose narrowminded views on the rest.
5) Frank has replied to the rest.
thanks
cbrodersen
1) When BR needs an attorney to speak/write on his behalf he will choose a real one. FYI he even admits cutting some corners in his book, AR when you take the time to read it.
2) When you read the whole thread then you will realise that I went through "your" arguments one by one and was indicated otherwise by more experienced DIYers, whom I appreciate their views more, being openminded.
3) the Stereophile argument does not make any sense to me and I would value the opinion of experienced DIYers more who have no commercial benefit out of all this.
4) Just because you have built the T8 that does not mean that it is the best sounding unit on earth, there is always room for improvement.
5) The value of this thread is to learn something, not to try to impose narrowminded views on the rest.
5) Frank has replied to the rest.
T8 OTL
I have read it, but evidently you haven't, or you need to read it again. He "admits" not to corner-cutting, but to several very sensible provisions in the circuit that protect against possible faults, such as the 2 ohm cathode resistor, or the 100k grid resistors. Instead of using separate, active circuitry with a reaction time (as many OTLs do), BR uses discreet componentry that "reacts" instantaneously, because it is integral to the circuit. I prefer this approach not only for the reliability, for also for the relative simplicity of the build. But to call this kind of well-thought-out design "cutting corners" is simply wrong and misleading, IMO.
As much as I am turned off by much of what Stereophile stands for, I think their Class A rating is revealing because Transcendent Sound is a factory-direct company who has never advertised in Stereophile, and in many ways stands in direct opposition to the "ultra-high-end" represented by Stereophile, The Absolute Sound, and others.
I never said that it was "the best sounding unit on earth", only the best-sounding in my system, so far. And while I won't disagree with you that there is always room for improvement, I believe it is important to build the stock unit first, without mods. Only after careful listening and evaluation should one consider making modifications.
Funny--"narrowminded" is exactly what I thought of your speculations about the T8, especially since you have never built one, or possibly even heard one! If you had built one and were comparing it with other OTLs, then I would indeed be willing to "learn something", but that doesn't seem to be the case.🙂
OK cbrodersen , I'll take your word for it. If you are happy with the T8 then by all means this is very good for you.
Personally I am very much inclined to listen to past experiences of trustful others. I have found this is a more efficient and expeditious way of proceeding, in all walks of life. Therefore, if more than one, of the highly knowledgeable members, indicate something empirically, I am very much willing to listen to it, without wasting time building something which eventually and more probably would prove right what the others noted.
Then again these are my views.....
FYI I very much value BR's circuits and BR as a person, and even offered to assist him (BR) to register his Patent in Europe.
Personally I am very much inclined to listen to past experiences of trustful others. I have found this is a more efficient and expeditious way of proceeding, in all walks of life. Therefore, if more than one, of the highly knowledgeable members, indicate something empirically, I am very much willing to listen to it, without wasting time building something which eventually and more probably would prove right what the others noted.
Then again these are my views.....
FYI I very much value BR's circuits and BR as a person, and even offered to assist him (BR) to register his Patent in Europe.
I picked up a few 6c19pi tubes and now need to match a few pair.
I have a EMC 213 tester but it shure has no listing for this tube.
I also have a EICO 635 that I need a manual for any help there would be more than welcome.
One last question, I saw one old OTL designe that used a push
pull cathode follower using 8 6as7`s for 6.8w into 16 ohm.
What output could I get from just 1 pair of 6c33c-b biased at
300ma ? Wouldn`t my output be limited to 300ma? I know
this would be a verry ineffecent use of a pair of these tubes
but it would lend itself to the application of super semmetry
feedback....
Woody:
I have a EMC 213 tester but it shure has no listing for this tube.
I also have a EICO 635 that I need a manual for any help there would be more than welcome.
One last question, I saw one old OTL designe that used a push
pull cathode follower using 8 6as7`s for 6.8w into 16 ohm.
What output could I get from just 1 pair of 6c33c-b biased at
300ma ? Wouldn`t my output be limited to 300ma? I know
this would be a verry ineffecent use of a pair of these tubes
but it would lend itself to the application of super semmetry
feedback....
Woody:
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