Pentode in UL mode
Aleksandre,
during the development of your RH84 did your try to combine the output pentode in UL mode and to compare the results!?
You will also get a little NFB through UL tap! I am asking you this because I sometimes prefer to listen the UL tap than the triode or pentode mode on my PP 6CA7 amp(output T/X is purchased from Maplin),depending of what kind of music I am listening to! There are SE output T/X at the market with UL tap at 43% windings,IIRC. They are little more expensive than the ordinary SE but I think they are worth to try.
Regards,
Yugovitz
Aleksandre,
during the development of your RH84 did your try to combine the output pentode in UL mode and to compare the results!?
You will also get a little NFB through UL tap! I am asking you this because I sometimes prefer to listen the UL tap than the triode or pentode mode on my PP 6CA7 amp(output T/X is purchased from Maplin),depending of what kind of music I am listening to! There are SE output T/X at the market with UL tap at 43% windings,IIRC. They are little more expensive than the ordinary SE but I think they are worth to try.
Regards,
Yugovitz
RH84 vs. the Zen: further comments
First of all, let me apologise if my previous comment was a
little hasty -- maybe I have overreacted, but when it comes
to that, I might be a little touchy. On one hand, I live
where I live and my life in the last 15 years has not been
milk and honey, in a sense that most western democracies'
citizens cannot quite imagine. On the other, it is a sad
truth that "no one is a messiah in his own village" -- far
from the notion that I would want to be considered a
messiah or guru!
Let me comment the other, more important issues here. The
last, but very crucial question, came from Yugo. No, I did
not try it in UL mode, and aside the fact that I have no UL
tapped transformers at hand, it would not serve any
particular purpose. Because, as I see it, we are not
talking here about pentodes/tetrodes and the way to use
them, but about a quite different circuit topology which
actually exploits what a pentode can give us, where the
pentode itself is not to be viewed as a pentode, but as a
tube of "such and such charactheristics".
The concept of using a pentode as a current/voltage
converter has been explained in the already linked John
Broskie article. But, why I say that the circuit is a
different pair of shoes can be seen by reviewing the pages
a little more carefully, and paying particular attention
after page 8. The problem with reading those articles is
the fact that they were split as html pages in a not so
orderly manner, and quite long to read -- you had to print
them to read them carefully. Most probably that is why the
author started converting his new articles in .pdf files.
Until page 8, all notions are very general, to say the
least. In fact, you could use them as ideas to develop your
own concepts, but most readers do not have enough knowledge
or immagination to venture on such a journey. From page 8,
a more direct approach begins, with a 300B tube and a
driver to be chosen (in the end, it is a 5965). And, this
circuit which is proposed, while being quite interesting,
especially for further refinements, has little to do with
the RH series of amps, except for the fact that they do
resemble in the manner the tubes are used. A similar issue
is obvious when we speak about Loftin-White amps: they come
in two flavours -- one (which I maybe wrongly consider to
be the "true" one) is when the current draw of the driver
thru the anode resistor is directly used to bias the output
tube, since the driver is beneath the tube itself; the
other is when the driver directly biases the output tube,
but is not restrained to working beneath the output tube,
but gets it's HT from the B+ rail, thus allowing it higher
voltage swings.
Now that we mention the famous "Darling" amps, I recall
there is a Loftin-White variety of Darling, which is just
like the second type I mentioned. And, just like these two
topologies actually have in common only the fact that the
driver is directly coupled to the output tube, my RH amps
and the amp described by John Broskie have little in
common.
To make a digression, the Darling amps somehow came to be
famous -- and I never understood why. Aside the fact that
the available power in one SE tube mode is quite lowish,
maybe the 1626 is a very common tube on the American
continent... but in Europe, you would better look for a 10Y
since it is easier to find. And, I would not compare the
two neither as price nor as charisma.
Now to the point of my reaction -- simplification of
concepts. Maybe it is that you i.e. need some knowledge to
be able to see all aspects of a design, and that is why
people do not immediately see those differences -- which I
can understand when it is about nuances.
1.Choke-filtered power supply in RH84
This is a huge difference, you know?! Not that it is or
should be original, but it is "the most sound way" to deal
with an SE amp power supply. The fact that chokes cost more
than sand resistors is not to be condoned here, since
no-one said it had to be a 100H/100mA choke wound with
silver and gold threads, costing xy thousand US$! A quite
simple and cheap choke would do a great deal of good to the
design, yet it was ommitted for more than obvious
cost/profit reasons.
2.Pentode mode operation in RH84
As I already said, pentode mode operation is not the true
definition here. And, if said with that formulation, it
immediately implies a lesser design. On the other hand, we
are talking about the same tube used in the Zen amp...
using it in triode mode still leaves us with a pentode,
since aside the fact that between the grid and anode you
still get two grids, you cannot alleviate the fact that the
electrons do not get to g2, g3 and a in a different
fraction of time -- since g3 remains at the potential of
the cathode (it does not have a separate pin -- and
furthermore, the opion of using the pin which as I recall
exists on the SV83 is not used in the Zen!).
On the other hand, pentode mode means more power, where the
PMPO chepo rating of the Zen becomes a more realistic
figure, making it quite useful for ordinary people with
ordinary 86dB/W/m speakers.
Finally, when I said "almost identical sound" I said that
on purpose, but in marketing terms I should have said
"identical". Because, I will not fool myself that there is
not difference in sound, both because I can hear it on my
equipment with my ears, and since theoretically there
should be some difference. But, the difference is so slight
that we can call it "almost identical" -- to tell the
truth, it has more power and more attack and better
definition (to all who have listened to it) in the "pentode
mode" or "RH mode" as would be more appropriate.
3.different input/driver valve
Actually, although I stressed the difference between
valves, the issue here is more like "incorrect operating
point vs. correct operating point". If we just correct the
operating point in the Zen amp, it WILL sound much better.
The reason why an incorrect operating point is employed,
and why a second even worse is offered to the user, remains
unclear. The current to be consumed is most certainly not
an issue here, since the power transformer and the
rectifier are more than capable of supplying it... and the
filtering caps are not that small not to be able to give an
adequate ripple characterstic to the B+ supply with
increased current. I will not fall in the trap of making
conclusions by myself, although, like with the PMPO rating,
I would expect the author to write an essay on "how
specially selected tubes by especially knowledgeable people
can give discerning sound qualities to the illuminati"
(oops, I did it too: that was sarcasm, but at least it does
not give anyone a liable case).
4.individual bypassed cathode resistors
Well, since we are talking about stereo, not dual-mono... I
consider that a "sine qua non" condition. Darling or no
darling, it is both logical and straight-forward. And, it
is usually done with sand resistors, so it costs so little
one must not mind. The fact that in the Zen a special
resistor with cooler is used does not do the trick of
making me believe that it is about the price of components.
When it comes to the point of mimicking AC ground, I would
at least bypass. If you have a cathode biased SE amp at
hand, try removing the bypass caps from the output tube's
cathode resistors, and then see for yourself whether the
amp still has the same gain: if it has, then I am wrong...
if it has not, then you are wrong in assuming that the case
of mimicking AC ground can be applied to this instance. On
the other hand, bypassing the "common cathode resistor"
might prove useful.
As you can see for yourselves from this lengthy "essay",
the differences are not subtle at all -- and while to those
who have not noticed by themselves what I have just written
the previous short-definition of differences might sound
correct, I hope that once they read this further
explanation it will become if not obvious, then at least
"more interesting, as something to think about next time".
Regards to all, and Merry Christmas!
Aleksandar
First of all, let me apologise if my previous comment was a
little hasty -- maybe I have overreacted, but when it comes
to that, I might be a little touchy. On one hand, I live
where I live and my life in the last 15 years has not been
milk and honey, in a sense that most western democracies'
citizens cannot quite imagine. On the other, it is a sad
truth that "no one is a messiah in his own village" -- far
from the notion that I would want to be considered a
messiah or guru!
Let me comment the other, more important issues here. The
last, but very crucial question, came from Yugo. No, I did
not try it in UL mode, and aside the fact that I have no UL
tapped transformers at hand, it would not serve any
particular purpose. Because, as I see it, we are not
talking here about pentodes/tetrodes and the way to use
them, but about a quite different circuit topology which
actually exploits what a pentode can give us, where the
pentode itself is not to be viewed as a pentode, but as a
tube of "such and such charactheristics".
The concept of using a pentode as a current/voltage
converter has been explained in the already linked John
Broskie article. But, why I say that the circuit is a
different pair of shoes can be seen by reviewing the pages
a little more carefully, and paying particular attention
after page 8. The problem with reading those articles is
the fact that they were split as html pages in a not so
orderly manner, and quite long to read -- you had to print
them to read them carefully. Most probably that is why the
author started converting his new articles in .pdf files.
Until page 8, all notions are very general, to say the
least. In fact, you could use them as ideas to develop your
own concepts, but most readers do not have enough knowledge
or immagination to venture on such a journey. From page 8,
a more direct approach begins, with a 300B tube and a
driver to be chosen (in the end, it is a 5965). And, this
circuit which is proposed, while being quite interesting,
especially for further refinements, has little to do with
the RH series of amps, except for the fact that they do
resemble in the manner the tubes are used. A similar issue
is obvious when we speak about Loftin-White amps: they come
in two flavours -- one (which I maybe wrongly consider to
be the "true" one) is when the current draw of the driver
thru the anode resistor is directly used to bias the output
tube, since the driver is beneath the tube itself; the
other is when the driver directly biases the output tube,
but is not restrained to working beneath the output tube,
but gets it's HT from the B+ rail, thus allowing it higher
voltage swings.
Now that we mention the famous "Darling" amps, I recall
there is a Loftin-White variety of Darling, which is just
like the second type I mentioned. And, just like these two
topologies actually have in common only the fact that the
driver is directly coupled to the output tube, my RH amps
and the amp described by John Broskie have little in
common.
To make a digression, the Darling amps somehow came to be
famous -- and I never understood why. Aside the fact that
the available power in one SE tube mode is quite lowish,
maybe the 1626 is a very common tube on the American
continent... but in Europe, you would better look for a 10Y
since it is easier to find. And, I would not compare the
two neither as price nor as charisma.
Now to the point of my reaction -- simplification of
concepts. Maybe it is that you i.e. need some knowledge to
be able to see all aspects of a design, and that is why
people do not immediately see those differences -- which I
can understand when it is about nuances.
1.Choke-filtered power supply in RH84
This is a huge difference, you know?! Not that it is or
should be original, but it is "the most sound way" to deal
with an SE amp power supply. The fact that chokes cost more
than sand resistors is not to be condoned here, since
no-one said it had to be a 100H/100mA choke wound with
silver and gold threads, costing xy thousand US$! A quite
simple and cheap choke would do a great deal of good to the
design, yet it was ommitted for more than obvious
cost/profit reasons.
2.Pentode mode operation in RH84
As I already said, pentode mode operation is not the true
definition here. And, if said with that formulation, it
immediately implies a lesser design. On the other hand, we
are talking about the same tube used in the Zen amp...
using it in triode mode still leaves us with a pentode,
since aside the fact that between the grid and anode you
still get two grids, you cannot alleviate the fact that the
electrons do not get to g2, g3 and a in a different
fraction of time -- since g3 remains at the potential of
the cathode (it does not have a separate pin -- and
furthermore, the opion of using the pin which as I recall
exists on the SV83 is not used in the Zen!).
On the other hand, pentode mode means more power, where the
PMPO chepo rating of the Zen becomes a more realistic
figure, making it quite useful for ordinary people with
ordinary 86dB/W/m speakers.
Finally, when I said "almost identical sound" I said that
on purpose, but in marketing terms I should have said
"identical". Because, I will not fool myself that there is
not difference in sound, both because I can hear it on my
equipment with my ears, and since theoretically there
should be some difference. But, the difference is so slight
that we can call it "almost identical" -- to tell the
truth, it has more power and more attack and better
definition (to all who have listened to it) in the "pentode
mode" or "RH mode" as would be more appropriate.
3.different input/driver valve
Actually, although I stressed the difference between
valves, the issue here is more like "incorrect operating
point vs. correct operating point". If we just correct the
operating point in the Zen amp, it WILL sound much better.
The reason why an incorrect operating point is employed,
and why a second even worse is offered to the user, remains
unclear. The current to be consumed is most certainly not
an issue here, since the power transformer and the
rectifier are more than capable of supplying it... and the
filtering caps are not that small not to be able to give an
adequate ripple characterstic to the B+ supply with
increased current. I will not fall in the trap of making
conclusions by myself, although, like with the PMPO rating,
I would expect the author to write an essay on "how
specially selected tubes by especially knowledgeable people
can give discerning sound qualities to the illuminati"
(oops, I did it too: that was sarcasm, but at least it does
not give anyone a liable case).
4.individual bypassed cathode resistors
Well, since we are talking about stereo, not dual-mono... I
consider that a "sine qua non" condition. Darling or no
darling, it is both logical and straight-forward. And, it
is usually done with sand resistors, so it costs so little
one must not mind. The fact that in the Zen a special
resistor with cooler is used does not do the trick of
making me believe that it is about the price of components.
When it comes to the point of mimicking AC ground, I would
at least bypass. If you have a cathode biased SE amp at
hand, try removing the bypass caps from the output tube's
cathode resistors, and then see for yourself whether the
amp still has the same gain: if it has, then I am wrong...
if it has not, then you are wrong in assuming that the case
of mimicking AC ground can be applied to this instance. On
the other hand, bypassing the "common cathode resistor"
might prove useful.
As you can see for yourselves from this lengthy "essay",
the differences are not subtle at all -- and while to those
who have not noticed by themselves what I have just written
the previous short-definition of differences might sound
correct, I hope that once they read this further
explanation it will become if not obvious, then at least
"more interesting, as something to think about next time".
Regards to all, and Merry Christmas!
Aleksandar
Re: RH84 vs. the Zen: further comments
That's ok. No offence taken
I see what you mean now. Thanks for the explanation.
Same thing here. Not particularly cheap (but nowhere as expensive as 10Y). I think you can get them for something like 10 for US$29 from Fair Radio or something (haven't checked in a while), so that's probably why they're popular. Rather non-linear valves too... and as you've said, a paltry amount of output power... but that's an argument for another day.
I see the differences clearly. I was listing some of them to hopefully open some discussion about your amplifier design. In any case, your explanation of the differences will be most informative to any who wish to build the RH84 (or Zen) and see the differences, and the reasons for which they are different. It's nice to see someone spending the time to make things clear
Sorry, I thought the cathode resistors were bypassed on the Zen (I should have checked the facts before I opened my mouth
)
Of course the gain will drop with the cathode resistors unbypassed, if it didn't, quite a few textbooks would have to be rewritten (and perhaps a few laws of physics). Hmm.... the Zen is a stranger design than I thought... purposely making a circuit to allow channel mixing
Merry Christmas and a Happy New Year to you too.
Alex Kitic said:
That's ok. No offence taken
Alex Kitic said:
I see what you mean now. Thanks for the explanation.
Alex Kitic said:
Same thing here. Not particularly cheap (but nowhere as expensive as 10Y). I think you can get them for something like 10 for US$29 from Fair Radio or something (haven't checked in a while), so that's probably why they're popular. Rather non-linear valves too... and as you've said, a paltry amount of output power... but that's an argument for another day.
Alex Kitic said:
I see the differences clearly. I was listing some of them to hopefully open some discussion about your amplifier design. In any case, your explanation of the differences will be most informative to any who wish to build the RH84 (or Zen) and see the differences, and the reasons for which they are different. It's nice to see someone spending the time to make things clear
Alex Kitic said:
Sorry, I thought the cathode resistors were bypassed on the Zen (I should have checked the facts before I opened my mouth
) Of course the gain will drop with the cathode resistors unbypassed, if it didn't, quite a few textbooks would have to be rewritten (and perhaps a few laws of physics). Hmm.... the Zen is a stranger design than I thought... purposely making a circuit to allow channel mixing
Alex Kitic said:
Merry Christmas and a Happy New Year to you too.
I built a revised version of the little Zen amp using a 5687 as the input tube. It was a very nice sounding and involving amp. I feel the EL84 is the best Pentode or tetrode to use in triode mode soundwise but you are limited in the voltage swing you can apply to the grid ( unless you exceed its maximum rated plate voltage) and it will clip during a powerful passage because of the limited grid bias voltage headroom available without frying the tube. They sound wonderful for light Jazz and female vocalist. There are a couple of Diana Krall songs with such over emphasized mids and mid highs that they will cause the little guys (the EL84s) to clip unless you are listening at a lower than desirable level. Of course there's no pint in listening at that point. While it's sound is more articulate and airy it's bias voltage and power limitations make the EL34 a far better tube for a good solid all around tube amp. Anyway, the schematic for the sweet little EL84 SE amp (my first and arguably most enjoyable amp with the right music) is posted below. If you build it, enjoy.
G
G
Attachments
Gavin's Amp
Hi, Gavin...
Nice little elaboration of the Zen-amp. Nice little power supply. I do not have the time at the moment to review the operating point of your driver, although it does seem to me that it is drawing very little current.
Did you actually take a peak at the site previously mentioned and read the last few pages of the thread? Nice as your amp is, the whole post looks to me like an anti-climax. After some discussion on design principles, you just cool us off with nice-little-Zen-revisited and a story about EL84 vs. EL34.
Did you consider that the EL84 can overcome those subtle deficiencies you mention just by being operated differently than in triode mode (1.8W max) -- for instance, in RH mode ?
Regards,
Aleksandar
Hi, Gavin...
Nice little elaboration of the Zen-amp. Nice little power supply. I do not have the time at the moment to review the operating point of your driver, although it does seem to me that it is drawing very little current.
Did you actually take a peak at the site previously mentioned and read the last few pages of the thread? Nice as your amp is, the whole post looks to me like an anti-climax. After some discussion on design principles, you just cool us off with nice-little-Zen-revisited and a story about EL84 vs. EL34.
Did you consider that the EL84 can overcome those subtle deficiencies you mention just by being operated differently than in triode mode (1.8W max) -- for instance, in RH mode ?
Regards,
Aleksandar
Actually all I meant to add tto the thread was that the linearity and output impedance of the input stage makes a pronounced impact on the overall sound of the amp regardless of the topology of the power stage. I have not read far enough into the thread to appreciate the differences between a good old SE triode mode and RH mode. When I have the time to give it a thorough read I will. I was just putting out a design that while simple is probably the best sounding amp i have heard (subjectively speaking of course) except for a Parafeed 300B amp I heard through a pair of very efficient Altec horn loaded loudspeakers in a well treated very acoustically nuetral room. That sound and level of enjoyment has been a personal benchmark for me. I'm certainly not the most learned member in this forum and I am certainly not qualified to argue the virtues and shortcomings of one topology versus another. AC analysis except on the most basic level is not my cup of tea. I suppose that if I was dissatisfied with the sound of a Pseudo triode single ended output stage then I would be more versed in design theory and more qualified to have an opinion one way or another. I am very satified and content with the sound of SE amps in triode mode but dislike the sound of Class A in pentode mode and have not felt the need to experiment with ultralinear mode as I don't think the result will be worth the sacrifice of my very limited free time. I just enjoy listening in ignorant bliss. I put my version of a SE EL84 amp out as a easy to build, inexpensive rewarding option for a project.
SE pseudo triode vs. RH pentode
Gavin (mostly),
sorry if you feel offended -- but sometimes you should read a thread (just like sometimes I need to...) before you post.
Since the thread was named EL84SE design recommendations, and my name was mentioned, I felt the urge to see what was it all about... and, there we were again, with old fashioned, maybe it would be better to say market fashioned -- pseudo triode amps.
Not that pseudo triode does not have it's merits -- it's the easiest way to use a pentode/tetrode tube in any amp. BUT what I am trying to do is convice everyone to try to let go of old stereotypes and try something different, if not new.
When I was thinking that at least in this thread we were finished with the market-minded simple Zen amp (and what a name, at that), here you come with "Zen revisited". I did not do any calculus on your driver's operating point... and there is no need for that. Just review the last few pages of posts carefully, maybe read some of the linked articles and review the linked sites.
Regards,
Aleksandar
Gavin (mostly),
sorry if you feel offended -- but sometimes you should read a thread (just like sometimes I need to...) before you post.
Since the thread was named EL84SE design recommendations, and my name was mentioned, I felt the urge to see what was it all about... and, there we were again, with old fashioned, maybe it would be better to say market fashioned -- pseudo triode amps.
Not that pseudo triode does not have it's merits -- it's the easiest way to use a pentode/tetrode tube in any amp. BUT what I am trying to do is convice everyone to try to let go of old stereotypes and try something different, if not new.
When I was thinking that at least in this thread we were finished with the market-minded simple Zen amp (and what a name, at that), here you come with "Zen revisited". I did not do any calculus on your driver's operating point... and there is no need for that. Just review the last few pages of posts carefully, maybe read some of the linked articles and review the linked sites.
Regards,
Aleksandar
Alex I don't think you owe me an apology but some might frown on the fact that you have taken someone else's thread and used it as your personal soap box. What type of "sound " pleases each of us is different and for the most part has nothing to do with complexity or technical excellence. It is a subjective opinion in which logic does not play the lead role. You can expound on the virtues of a design but don't expect everyone to take your opinion as fact or to agree with you. I was offering a SE EL84 design to the originator of the thread which is what he wanted in the first place. I look at DIY electronics as productive and enjoyable way to spend some of my free time. I think you might be looking for more than that and I wish you luck. I fear though that you may be dissapointed when reality doesn't quite meet your expectations.
The more designs the better... Alex, your design is very interesting, and i'll certainly get around to building it... but i will also build some Mulligan inspired versions too. The ECC81 up front seems a bit pedestrian (i do have some nice ones, but even more ECC85s). Have you tried any other input tubes?
dave
dave
STOLEN THREAD AND VARIOUS TUBES
Well, now it seems that I have stolen the thread. I still do not think so. The thread is about EL84SE design recommendations -- and I think since I was mentioned in the first place, and secondly offered my design to whoever wants it, it is quite natural that I should now stick to it, both defending my design and trying to prove that it is the best available There is nothing bad about it, I think.
I do not know what to think of that. Yes, it is true that I am looking for more than that -- let us call it exploring and experimenting, only maybe on a more technically advanced level than might be customary in contemporary DIY circles.
When it comes to the part of being dissapointed, well I am not at all dissapointed with what I got so far with my designs -- on the other hand, I tend to be dissapointed with most people... some will negate obvious things (for a whole variety of reasons) while others might be reluctand to try the offered solution, maybe out of not understanding what it implies, or just because of the fact that they have already made up their mind about things (or their mind has been made up for them). But that goes way beyond DIY audio, it's mostly been like that all my life.
Let us get back to constructive issues... planet10 and different valves at the input/driver position.
Of course, the configuration can be designed for a different input tube, involving a different calculus of operating point and resistor values etc. I presume you asked about whether some other tubes might be inserted in the socket and tried "right out" -- and of course (were would else the experimenting be) they were.
ECC83/12AX7 types can be inserted in the driver socket, and drive the power tube to full power -- the operating point will be correct, although a little unusual, with low voltage across the tube and quite a lot of current (ECC83s are usually applied more voltage and much less current) -- but correct after all and not harmful to the tube. Good sound, somewhat mellower, might be a better "tweaking solution" to some.
5965 and E180CC are a second solution that works, maybe even better than the ECC81/12AT7. The transconductance of the tube is higher, so it makes up for the loss of amplification factor, and the amp is obviously driven to full power. Very good sound, maybe even better than the tube it was designed for (although a little "faster" than some might like).
ECC82/12AU7 and xSN7 types cannot be used "directly" (of course, the octal types will need another socket to be fitted), because their amplification factor is not high enough, therefore the amp is never driven to full power. The sound? Nothing special.
6SL7 and similia cannot be used either -- the amplification factor would be high enough, but the transconductance is too low to make it work, and they just cannot drive the output tube to full power.
Does this improve anything? Well, those who try it can speak for themselves, and give opinions...
Well, maybe that is the problem with this design... the ECCxx series seems a bit pedestrian! If it were octal tubes, maybe it would attract more interest? If you ask me, there is hardly any tube more "pedestrian" than EL84 -- but I still like it.
The amp was not meant to be expensive or exotic -- yet to perform and sound very well, even with normal speakers. Something of an eye opener for people who think only amps with 300Bs and similia are worth building and listening to!
If the story is about pedestrian tubes... well, why the thread then? I am working (actually waiting for inspiration and time) to do some work on a less pedestrian RH amp, with 307A/VT225 tubes. Directly Heated Pentode in RH mode... less pedestrian, ha? Eventually, some exotic driver? But that would be abusing the thread, wouldn't it?
Let me know...
Aleksandar
Well, now it seems that I have stolen the thread. I still do not think so. The thread is about EL84SE design recommendations -- and I think since I was mentioned in the first place, and secondly offered my design to whoever wants it, it is quite natural that I should now stick to it, both defending my design and trying to prove that it is the best available
There is nothing bad about it, I think.I do not know what to think of that. Yes, it is true that I am looking for more than that -- let us call it exploring and experimenting, only maybe on a more technically advanced level than might be customary in contemporary DIY circles.
When it comes to the part of being dissapointed, well I am not at all dissapointed with what I got so far with my designs -- on the other hand, I tend to be dissapointed with most people... some will negate obvious things (for a whole variety of reasons) while others might be reluctand to try the offered solution, maybe out of not understanding what it implies, or just because of the fact that they have already made up their mind about things (or their mind has been made up for them). But that goes way beyond DIY audio, it's mostly been like that all my life.
Let us get back to constructive issues... planet10 and different valves at the input/driver position.
Of course, the configuration can be designed for a different input tube, involving a different calculus of operating point and resistor values etc. I presume you asked about whether some other tubes might be inserted in the socket and tried "right out" -- and of course (were would else the experimenting be) they were.
ECC83/12AX7 types can be inserted in the driver socket, and drive the power tube to full power -- the operating point will be correct, although a little unusual, with low voltage across the tube and quite a lot of current (ECC83s are usually applied more voltage and much less current) -- but correct after all and not harmful to the tube. Good sound, somewhat mellower, might be a better "tweaking solution" to some.
5965 and E180CC are a second solution that works, maybe even better than the ECC81/12AT7. The transconductance of the tube is higher, so it makes up for the loss of amplification factor, and the amp is obviously driven to full power. Very good sound, maybe even better than the tube it was designed for (although a little "faster" than some might like).
ECC82/12AU7 and xSN7 types cannot be used "directly" (of course, the octal types will need another socket to be fitted), because their amplification factor is not high enough, therefore the amp is never driven to full power. The sound? Nothing special.
6SL7 and similia cannot be used either -- the amplification factor would be high enough, but the transconductance is too low to make it work, and they just cannot drive the output tube to full power.
Does this improve anything? Well, those who try it can speak for themselves, and give opinions...
Well, maybe that is the problem with this design... the ECCxx series seems a bit pedestrian! If it were octal tubes, maybe it would attract more interest? If you ask me, there is hardly any tube more "pedestrian" than EL84 -- but I still like it.
The amp was not meant to be expensive or exotic -- yet to perform and sound very well, even with normal speakers. Something of an eye opener for people who think only amps with 300Bs and similia are worth building and listening to!
If the story is about pedestrian tubes... well, why the thread then? I am working (actually waiting for inspiration and time) to do some work on a less pedestrian RH amp, with 307A/VT225 tubes. Directly Heated Pentode in RH mode... less pedestrian, ha? Eventually, some exotic driver? But that would be abusing the thread, wouldn't it?
Let me know...
Aleksandar
OH, guys, you are impossible!
Hey, guys, is it possible? The moment I say VTxxx someone is interested!!!
Well, in a spirit of cooperation, and since I owe this amp anyway to quite a lot of people who cared to supply me with datasheets (at the time, not available on tdsl), even with tubes... I am inclined to sharing ideas on this.
I only think that for this topic another thread should be created. Who is going to indulge on that? I think I've been maybe too prominent during the last few days, so I might attract some negative toughts...
So, create a thread (i.e. generic, like "307A SE amp recommandations...), and I will join!
Regards,
Aleksandar
Hey, guys, is it possible? The moment I say VTxxx someone is interested!!!
Well, in a spirit of cooperation, and since I owe this amp anyway to quite a lot of people who cared to supply me with datasheets (at the time, not available on tdsl), even with tubes... I am inclined to sharing ideas on this.
I only think that for this topic another thread should be created. Who is going to indulge on that? I think I've been maybe too prominent during the last few days, so I might attract some negative toughts...
So, create a thread (i.e. generic, like "307A SE amp recommandations...), and I will join!
Regards,
Aleksandar
Re: STOLEN THREAD AND VARIOUS TUBES
There is no need to defend your design. No one is attacking it, just looking at it and asking questions. There is a difference.
You said yourself somewhere that the output stage in "RH" mode is run as an I/V convertor. As such, a pentode input stage (and its inherently high Zout) may improve performance. At the very least, it will give a different sound. Of course, pentodes are less linear and all of that.... The high Zout shouldn't mess up the HF performance too much anyway since Rfb shunts the milleramplified Cgp of the output valve, which creates a HF pole, hence limiting response. (I admit this is arguable, the grid of a pentode presents an inherently low capacitance - in comparison with triodes.)
To those wanting Alex to use "Less pedestrian tubes" The EL84 and ECC81 are boring, I admit. That doesn't mean that they are poor performers, though. (Said by someone who rarely uses "pedestrian tubes" himself)
Alex, to get more people interested, why not try something like "RH mode" 813? That'll get people interested with its glowing filament! Or if you're not going to build a 1kV+ power supply, try something with KTxx valves. They tend to get people excited (look at all the new types given a KT designation, KT90, KT100 etc). If you're not looking to spend too much money, the KT33/KT33C is cheap. No one seems to want them.
Alex Kitic said:The thread is about EL84SE design recommendations -- and I think since I was mentioned in the first place, and secondly offered my design to whoever wants it, it is quite natural that I should now stick to it, both defending my design and trying to prove that it is the best available
There is no need to defend your design. No one is attacking it, just looking at it and asking questions. There is a difference.
Alex Kitic said:
You said yourself somewhere that the output stage in "RH" mode is run as an I/V convertor. As such, a pentode input stage (and its inherently high Zout) may improve performance. At the very least, it will give a different sound. Of course, pentodes are less linear and all of that.... The high Zout shouldn't mess up the HF performance too much anyway since Rfb shunts the milleramplified Cgp of the output valve, which creates a HF pole, hence limiting response. (I admit this is arguable, the grid of a pentode presents an inherently low capacitance - in comparison with triodes.)
To those wanting Alex to use "Less pedestrian tubes" The EL84 and ECC81 are boring, I admit. That doesn't mean that they are poor performers, though. (Said by someone who rarely uses "pedestrian tubes" himself)
Alex, to get more people interested, why not try something like "RH mode" 813? That'll get people interested with its glowing filament! Or if you're not going to build a 1kV+ power supply, try something with KTxx valves. They tend to get people excited (look at all the new types given a KT designation, KT90, KT100 etc). If you're not looking to spend too much money, the KT33/KT33C is cheap. No one seems to want them.
answers...
A relatively short answer, for starters...
1) Defending my design
This is an obviously bad choice of words (command of the english language or not, I still speak some other language at home ). I should have said ADVOCATING -- does that sound better?
2) Pedestrian tubes
I agree that people should not regard ANY tube as plain pedestrian (OK, xCL86 xCL82 and similia might truly be pedestrian tubes... but that does not make tham uninteresting, since people have differing needs, possibilities and get satisfaction from building i.e. small amplifiers in the physical sense of the word).
On the other hand, those not interested in pedestrian tubes should immediately skip a forum on EL84 design... and go for some 300B alternatives, as I belive there are some. But, what is worth and feasible for an EL84, can be applied generally to any tetrode/pentode tube of higher interest, like KT90 or 6550... whatever.
3) RH mode 813 and similia
Well, when it comes to 813, we get to another set of cards. This tube can deliver very very much on its own, "without help of any RH concoction" -- just wire it in triode mode, and you will immediately get the goods, like high power output etc. But this is what I like to call "an EHV tube" -- extremely high voltage tube, where by extremely high voltage I assume everything a garden variety instrument cannot measure directly (like 700V DC). Most sites tend to stress the issue of danger, and I regard it as a necessity -- but at EHV levels (EHV in terms of audio applications, of course), I think that i.e. 1000V DC is dangerous to most.
4) What tubes need it?
I did some RH circuitry simulations for KT90 -- a long time ago, and I will try to find the files since I've recently been given some 6550's (the good variety, ST shaped, without holes in the anodes) and would like to try it, especially since at the time I called it "second generation RH". The same is true of i.e. 300B -- application of the same "second generation RH" circuitry did give some extremely interesting results when simulating. But the results I am talking about are numbers, like 9W with 1% distortion, as compared to the usual 9W 5% distortion advertised for 300B SE circuitry. How would it sound with triodes? Is it truly needed? You can easily get 6W of power from a KT90/6550/KT88 in triode mode, thus surpassing the 5W limit I believe to be
"the real world goal" for volksamplifiers in the sense that most people will find the power level to their listening satisfaction with ordinary "mid efficiency speakers" found in most homes.
What I want to say is that generally, I was never interested in simulating circuits (and designing them -- as some people here find to be un ugly and offensive term) if I did not have the tube at hand. Cost was never an issue for that, since I rarely paid "internet prices" for any tube I've stashed in my "collection").
Application of "RH circuitry" (if I am allowed to call it that) to whatever tube might be possible -- but just like the previously in this thread mentioned "promise of solid state", sometimes it might not make sense. The sound of a tetrode/pentode is more than obviously inferior to the sound of a triode -- if used conventionally.
During time, several application strategies were developped for tetrode/pentode tubes to bridge the gap between higher efficiency and inferior sound, like ultra-linear taps. Consider my "circuitry" as one such approach -- and it does deliver the goods, in the sense that the sound is much improved, as I previously said "almost identical to the triode connected tube in the same circuit". And almost identical can also mean "better". But it does need to have a reason for applying. A 300B with same power and less distortion (I did not try that one as for sound) does not necessarily mean "better than the usual" (just like the promise of solid state) -- on the other hand, 4-5W with less distortion and better sound compared with 1.5W with more distortion and lesser sound (from an EL84) seems to me a legitimate goal.
5) Pentode drivers
Yes, in theory a pentode driver might "do the trick" even better, since it has higher output impedance than triodes. With current sources, a high output impedance is very welcome (unless I got that wrong, and I sincerely believe I did not). The only reason why I did not try that one is given by the fact that a) the triodes mentioned above, which are mostly "garden variety" pedestrian types (easy for everyone to get hold) do the job quite well;
b) my "collection of suitable pentode drivers" is very low; c) exchanging the driver ECC81 i.e. garden variety type with some "better sounding NOS tube of the same or similar type" does give rewards in terms of better sound (i.e. Ei ECC81 vs. Telefunken ECC81, or Philips 6201, or "you-name-it-highly-regarded-NOS") -- that might implicate that "sonically inferior pentode tubes" might actually give lesser results in the particular application -- and their contribution in efficiency terms is not necessary for the task.
Finally, one issue should be considered, which most of those who tend to dismiss others with punctuation marks obviously overlook in their might -- whatever you want to do, takes time and effort. In order to design a circuit (i.e. 307A RH mode) I need to have spice models at hand. If I do not (and in 90% of the cases such models are not readily available) I have to "write" the model on my own, which is not that difficult as it looks, but takes some time and effort. Once the model is ready and inserted in the circuit, there is more work, thinking, and knowledge to be applied, in order to get some result. Therefore, the "collection" of RH circuits is relatively limited -- I did only what was interesting to me, or requested by friends -- and of course, when I had the time to do it.
Regards to all,
Aleksandar
A relatively short answer, for starters...
1) Defending my design
This is an obviously bad choice of words (command of the english language or not, I still speak some other language at home
). I should have said ADVOCATING -- does that sound better?2) Pedestrian tubes
I agree that people should not regard ANY tube as plain pedestrian (OK, xCL86 xCL82 and similia might truly be pedestrian tubes... but that does not make tham uninteresting, since people have differing needs, possibilities and get satisfaction from building i.e. small amplifiers in the physical sense of the word).
On the other hand, those not interested in pedestrian tubes should immediately skip a forum on EL84 design... and go for some 300B alternatives, as I belive there are some. But, what is worth and feasible for an EL84, can be applied generally to any tetrode/pentode tube of higher interest, like KT90 or 6550... whatever.
3) RH mode 813 and similia
Well, when it comes to 813, we get to another set of cards. This tube can deliver very very much on its own, "without help of any RH concoction" -- just wire it in triode mode, and you will immediately get the goods, like high power output etc. But this is what I like to call "an EHV tube" -- extremely high voltage tube, where by extremely high voltage I assume everything a garden variety instrument cannot measure directly (like 700V DC). Most sites tend to stress the issue of danger, and I regard it as a necessity -- but at EHV levels (EHV in terms of audio applications, of course), I think that i.e. 1000V DC is dangerous to most.
4) What tubes need it?
I did some RH circuitry simulations for KT90 -- a long time ago, and I will try to find the files since I've recently been given some 6550's (the good variety, ST shaped, without holes in the anodes) and would like to try it, especially since at the time I called it "second generation RH". The same is true of i.e. 300B -- application of the same "second generation RH" circuitry did give some extremely interesting results when simulating. But the results I am talking about are numbers, like 9W with 1% distortion, as compared to the usual 9W 5% distortion advertised for 300B SE circuitry. How would it sound with triodes? Is it truly needed? You can easily get 6W of power from a KT90/6550/KT88 in triode mode, thus surpassing the 5W limit I believe to be
"the real world goal" for volksamplifiers in the sense that most people will find the power level to their listening satisfaction with ordinary "mid efficiency speakers" found in most homes.
What I want to say is that generally, I was never interested in simulating circuits (and designing them -- as some people here find to be un ugly and offensive term) if I did not have the tube at hand. Cost was never an issue for that, since I rarely paid "internet prices" for any tube I've stashed in my "collection").
Application of "RH circuitry" (if I am allowed to call it that) to whatever tube might be possible -- but just like the previously in this thread mentioned "promise of solid state", sometimes it might not make sense. The sound of a tetrode/pentode is more than obviously inferior to the sound of a triode -- if used conventionally.
During time, several application strategies were developped for tetrode/pentode tubes to bridge the gap between higher efficiency and inferior sound, like ultra-linear taps. Consider my "circuitry" as one such approach -- and it does deliver the goods, in the sense that the sound is much improved, as I previously said "almost identical to the triode connected tube in the same circuit". And almost identical can also mean "better". But it does need to have a reason for applying. A 300B with same power and less distortion (I did not try that one as for sound) does not necessarily mean "better than the usual" (just like the promise of solid state) -- on the other hand, 4-5W with less distortion and better sound compared with 1.5W with more distortion and lesser sound (from an EL84) seems to me a legitimate goal.
5) Pentode drivers
Yes, in theory a pentode driver might "do the trick" even better, since it has higher output impedance than triodes. With current sources, a high output impedance is very welcome (unless I got that wrong, and I sincerely believe I did not). The only reason why I did not try that one is given by the fact that a) the triodes mentioned above, which are mostly "garden variety" pedestrian types (easy for everyone to get hold) do the job quite well;
b) my "collection of suitable pentode drivers" is very low; c) exchanging the driver ECC81 i.e. garden variety type with some "better sounding NOS tube of the same or similar type" does give rewards in terms of better sound (i.e. Ei ECC81 vs. Telefunken ECC81, or Philips 6201, or "you-name-it-highly-regarded-NOS") -- that might implicate that "sonically inferior pentode tubes" might actually give lesser results in the particular application -- and their contribution in efficiency terms is not necessary for the task.
Finally, one issue should be considered, which most of those who tend to dismiss others with punctuation marks obviously overlook in their might -- whatever you want to do, takes time and effort. In order to design a circuit (i.e. 307A RH mode) I need to have spice models at hand. If I do not (and in 90% of the cases such models are not readily available) I have to "write" the model on my own, which is not that difficult as it looks, but takes some time and effort. Once the model is ready and inserted in the circuit, there is more work, thinking, and knowledge to be applied, in order to get some result. Therefore, the "collection" of RH circuits is relatively limited -- I did only what was interesting to me, or requested by friends -- and of course, when I had the time to do it.
Regards to all,
Aleksandar
Hello Aleksandar,
Thank you for your interesting posts and please keep them coming. You seem to think differently to many people with regard to circuits / tubes. I will be trying the RH84 within the next week if I can find the parts in the junk box which I should be able to.
I have questions for you though. What are your thoughts on fixed bias in this circuit? Is it a waste of time? Did you try it?
I have sets of EL84's and also 5V6's and while I will build it initially with EL84's I also plan on trying the 5V6's.
Thanks
Andrew
Thank you for your interesting posts and please keep them coming. You seem to think differently to many people with regard to circuits / tubes. I will be trying the RH84 within the next week if I can find the parts in the junk box which I should be able to.
I have questions for you though. What are your thoughts on fixed bias in this circuit? Is it a waste of time? Did you try it?
I have sets of EL84's and also 5V6's and while I will build it initially with EL84's I also plan on trying the 5V6's.
Thanks
Andrew
Re: SE pseudo triode vs. RH pentode
That would depend on your definition of very little. The current through the driver is around 10-12 mA.
After having read the rest of the thread, as you suggested, I can see you are coming from.
I would indeed wouldn't it? How about a older yet still available tube like the 807. I was going to build a SE 807 amp but did not when I realized how little rms power I was going to get out of the circuit. Perhaps you can explain how the feedback resistor is calculated for a given input/output tube combination? Also I suspect that using a UL connection to the output tube in a "RH mode" amp would make the sound of the circuit differ from that of a pentode connection as was previously suggested in this thread.
Alex Kitic said:
That would depend on your definition of very little. The current through the driver is around 10-12 mA.
After having read the rest of the thread, as you suggested, I can see you are coming from.
Did you consider that the EL84 can overcome those subtle deficiencies you mention just by being operated differently than in triode mode (1.8W max) -- for instance, in RH mode ?
I would indeed wouldn't it? How about a older yet still available tube like the 807. I was going to build a SE 807 amp but did not when I realized how little rms power I was going to get out of the circuit. Perhaps you can explain how the feedback resistor is calculated for a given input/output tube combination? Also I suspect that using a UL connection to the output tube in a "RH mode" amp would make the sound of the circuit differ from that of a pentode connection as was previously suggested in this thread.
Additional
Gavin:
To start with the current drawn thru 5687, as I said, I was not going to do any calculus on that -- if not directly understood, I was actually sorry for being too dismissive. If it is 10-12mA, which seems quite a good operating point for the 5687, than there is no question whether it does sound a lot better than the original Zen.
807 -- although not quite the same topic (the thread is about EL84) -- you must have seen the RH807 amp on my site. This one was indeed built in a variety of versions, including an "integrated" one. And, as on the published schematics, it has quite "enough" power -- if some 5W as compared to the meagre amount in triode mode would be enough for you.
Furthermore, the 807 topic can be extended by either increasing the B+ (no changes in the circuit needed) just taking care about the Rk of the output tube, and the R before g2, in order not to surpass anode dissipation and g2 voltage ratings -- and it will give even more power. Alternatively, exchanging the 807 for a little more powerful members of the same family, like 6L6 specials, or 7027A, you can get up to almost 10W.
The calculation of the resistor seems to be 1:5 approximately, meaning that the Rfb is actually up to 5x larger than the Ra of the driver tube... it's a mix of current from the B+ rail, and current from above the anode of the output tube (and indeed some feedback) that does the trick. Actually, once that basics are established, there is a lot of trials by simulation and some thinking to be done. Not being a scientist, I have never given it a serious tought to make some exact rules on calculus.
UL taps would obviously do something with the sound -- as I said, I did not try that one, among other reasons because I did not and do not have at hand transformers with UL taps. It might improve the sound -- and it might decrease the power, as well? In order to give a serious answer that would not cause eventual ridicule, I must think a little more about it. It did not matter to me, in principle -- so I never dismissed that idea completely, nor gave it any particular consideration.
Andrewbee:
Great! Finally someone is going to give it a try (I mean, counting the people who were reading about it lately in the forum)! Just go ahead, and if you have any questions or problems, just send me an e-mail.
About fixed bias -- well, I think that would not work, you know... it is important for the circuit to have a Rk below the output tube -- just as it is important for the Rk of the driver tube not to be bypassed by a cap. Both cases invalidate the previous results in simulation tests. Theoretical reasons -- well, I would have to take another look in various texts (and try to recollect the toughts I had while working on the RH circuit).
6V6 (5V6 is a 6V6 with different filament requirements, or am I wrong?) -- the results would be similar. I think the same schematics for the RH84 can be applied to 6V6, since those tubes are quite similar (anode dissipation, etc.). If the drive requirements are different (relative -Ug) than maybe it would not work that well without "revisiting" the values. But, since noone has tried 6V6 in the circuit so far, I am very interested to know whether it satisfies.
Regards,
Aleksandar
Gavin:
To start with the current drawn thru 5687, as I said, I was not going to do any calculus on that -- if not directly understood, I was actually sorry for being too dismissive. If it is 10-12mA, which seems quite a good operating point for the 5687, than there is no question whether it does sound a lot better than the original Zen.
807 -- although not quite the same topic (the thread is about EL84) -- you must have seen the RH807 amp on my site. This one was indeed built in a variety of versions, including an "integrated" one. And, as on the published schematics, it has quite "enough" power -- if some 5W as compared to the meagre amount in triode mode would be enough for you.
Furthermore, the 807 topic can be extended by either increasing the B+ (no changes in the circuit needed) just taking care about the Rk of the output tube, and the R before g2, in order not to surpass anode dissipation and g2 voltage ratings -- and it will give even more power. Alternatively, exchanging the 807 for a little more powerful members of the same family, like 6L6 specials, or 7027A, you can get up to almost 10W.
The calculation of the resistor seems to be 1:5 approximately, meaning that the Rfb is actually up to 5x larger than the Ra of the driver tube... it's a mix of current from the B+ rail, and current from above the anode of the output tube (and indeed some feedback) that does the trick. Actually, once that basics are established, there is a lot of trials by simulation and some thinking to be done. Not being a scientist, I have never given it a serious tought to make some exact rules on calculus.
UL taps would obviously do something with the sound -- as I said, I did not try that one, among other reasons because I did not and do not have at hand transformers with UL taps. It might improve the sound -- and it might decrease the power, as well? In order to give a serious answer that would not cause eventual ridicule, I must think a little more about it. It did not matter to me, in principle -- so I never dismissed that idea completely, nor gave it any particular consideration.
Andrewbee:
Great! Finally someone is going to give it a try (I mean, counting the people who were reading about it lately in the forum)! Just go ahead, and if you have any questions or problems, just send me an e-mail.
About fixed bias -- well, I think that would not work, you know... it is important for the circuit to have a Rk below the output tube -- just as it is important for the Rk of the driver tube not to be bypassed by a cap. Both cases invalidate the previous results in simulation tests. Theoretical reasons -- well, I would have to take another look in various texts (and try to recollect the toughts I had while working on the RH circuit).
6V6 (5V6 is a 6V6 with different filament requirements, or am I wrong?) -- the results would be similar. I think the same schematics for the RH84 can be applied to 6V6, since those tubes are quite similar (anode dissipation, etc.). If the drive requirements are different (relative -Ug) than maybe it would not work that well without "revisiting" the values. But, since noone has tried 6V6 in the circuit so far, I am very interested to know whether it satisfies.
Regards,
Aleksandar
Re: RH84 vs. the Zen: further comments
The reason is very simple: they sound absolutely wonderful.
Incidentally, in my experience the shared cathode resistor tends to improve the soundstage, not shrink it. But, this is simply a matter of taste.
What I suggest is that you take a cliplead and connect the cathodes on one of your own amps to listen for yourself. It's a very simple experiment. Different amps tend to respond differently. Sharing the cathodes on an input stage will have a different effect than an output stage, &tc.
These are the kinds of things that are difficult to predict ahead of time by pure theorizing. One of my favorite pastimes is trying to explain the effect afterwards (so that we might predict in the future), but deciding what will sound best without listening is what has lead to a commercial wasteland of mediocre, flat sounding equipment. The stuff might be 'well engineered.' It might measure well and the circuits might be easy to defend, but they don't necessarily present the music well.
I think that creating a successful design requires a balance of theorizing and believing your ears. I don't think it is enough to rely completely on one or the other, but that is just my opinion!!
I suppose I could summarize my entire rant by saying that I would have to listen to both a mulligan and an rh84 before I could form an authoritative opinion about one being better than the other.
-- Dave Cigna
Alex Kitic said:
The reason is very simple: they sound absolutely wonderful.
Incidentally, in my experience the shared cathode resistor tends to improve the soundstage, not shrink it. But, this is simply a matter of taste.
What I suggest is that you take a cliplead and connect the cathodes on one of your own amps to listen for yourself. It's a very simple experiment. Different amps tend to respond differently. Sharing the cathodes on an input stage will have a different effect than an output stage, &tc.
These are the kinds of things that are difficult to predict ahead of time by pure theorizing. One of my favorite pastimes is trying to explain the effect afterwards (so that we might predict in the future), but deciding what will sound best without listening is what has lead to a commercial wasteland of mediocre, flat sounding equipment. The stuff might be 'well engineered.' It might measure well and the circuits might be easy to defend, but they don't necessarily present the music well.
I think that creating a successful design requires a balance of theorizing and believing your ears. I don't think it is enough to rely completely on one or the other, but that is just my opinion!!
I suppose I could summarize my entire rant by saying that I would have to listen to both a mulligan and an rh84 before I could form an authoritative opinion about one being better than the other.
-- Dave Cigna
DARLING AND Rk
When it comes to the Darling amps, I am inclined to believe they must have something goog going on, since so many people have built them, and there seems to be a general agreement that they sound well indeed.
I recall downloading and reading with great interest a text about various Darling amps being listened to in public by a group of enthusiasts. While the 1626 is not something I might find in some tube stash in my surroundings -- what actually struck me was that people tend to live better lives. They seemed to be able to gather in numbers and enjoy their hobby together -- which is far from possible in reality where I live (the country being both small and low-income).
Well, while it seems that most Darling amps had common cathode resistors below the output tube (even below the driver tube), NONE of these, as I recall, was UNBYPASSED. It is important to stress this issue, since there is quite a difference between using a common resistor which is bypassed by an adequately sized cap (therefore in AC terms it should be like if the caps were not common at all, since there should be no or little signal interaction) -- and using a common resistor which is not bypassed, with obvious signal interaction.
Clipping the Rk's together -- not that I am really willing to open an amp and try that... but it might be a good idea, just for the sake of trying. Since Rk's are usually bypassed (in my case), I do not think that there would be much of a difference. Doing it with unbypassed caps... well, it would certainly give a flavour to the sound.
I also recall reading a letter posted to Sound Practices about the sonic merits of "blonde monsters" -- the hi-fi of yesteryear. The point was that some people prefer (and are obviously entitled to it) sound which is maybe not that true to the source, but suitable to their palats. And, there is no universal truth...
Finally, when it comes to "Mulligans" (why the name?) vs. RH84 -- probably like most of the others, I am waiting for someone to try it. It was tried once, a few years ago -- a friend's friend who built an RH84 (his RH84 can be seen on my web-site as "built by M.S.") has had the opportunity to compare it to a Zen clone built by a friend of his. I even have a picture of the two amps -- but it is somewhere in "old mail" and I would have to go to great lengths to find it (mail archive database, not active). I cannot vouch for any of the amps, since I have not seen them (except on a photo) nor heard them, and I recall the Zen clone to be built with an AZ50 rectifier (which obviously does not sound the same as 5U4G) -- but I recall that the Zen clone owner decided that he should remake his Zen clone into an RH84. This may sound inflamatory to some, but you can just consider it as an invitation to try -- with no hidden second toughts.
Regards to all,
Aleksandar
When it comes to the Darling amps, I am inclined to believe they must have something goog going on, since so many people have built them, and there seems to be a general agreement that they sound well indeed.
I recall downloading and reading with great interest a text about various Darling amps being listened to in public by a group of enthusiasts. While the 1626 is not something I might find in some tube stash in my surroundings -- what actually struck me was that people tend to live better lives
. They seemed to be able to gather in numbers and enjoy their hobby together -- which is far from possible in reality where I live (the country being both small and low-income).Well, while it seems that most Darling amps had common cathode resistors below the output tube (even below the driver tube), NONE of these, as I recall, was UNBYPASSED. It is important to stress this issue, since there is quite a difference between using a common resistor which is bypassed by an adequately sized cap (therefore in AC terms it should be like if the caps were not common at all, since there should be no or little signal interaction) -- and using a common resistor which is not bypassed, with obvious signal interaction.
Clipping the Rk's together -- not that I am really willing to open an amp and try that... but it might be a good idea, just for the sake of trying. Since Rk's are usually bypassed (in my case), I do not think that there would be much of a difference. Doing it with unbypassed caps... well, it would certainly give a flavour to the sound.
I also recall reading a letter posted to Sound Practices about the sonic merits of "blonde monsters" -- the hi-fi of yesteryear. The point was that some people prefer (and are obviously entitled to it) sound which is maybe not that true to the source, but suitable to their palats. And, there is no universal truth...
Finally, when it comes to "Mulligans" (why the name?) vs. RH84 -- probably like most of the others, I am waiting for someone to try it. It was tried once, a few years ago -- a friend's friend who built an RH84 (his RH84 can be seen on my web-site as "built by M.S.") has had the opportunity to compare it to a Zen clone built by a friend of his. I even have a picture of the two amps -- but it is somewhere in "old mail" and I would have to go to great lengths to find it (mail archive database, not active). I cannot vouch for any of the amps, since I have not seen them (except on a photo) nor heard them, and I recall the Zen clone to be built with an AZ50 rectifier (which obviously does not sound the same as 5U4G) -- but I recall that the Zen clone owner decided that he should remake his Zen clone into an RH84. This may sound inflamatory to some, but you can just consider it as an invitation to try -- with no hidden second toughts.
Regards to all,
Aleksandar
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