jkeny said:
I've got everything I need to put together a prototype, but I'm trying to hold off. Problem is, I've got a number of non-audio related projects I need to get rolling and if I get started on this one, I probably won't be able to keep my hands off it. I may have to try the prototype just to satisfy my curiosity, but it's a slippery slope from there. Oh, what to do?
You?
Sheldon
a couple of output transformers...
On your search, I came across this Crowhurst article.
I'm not an expert in this area, but does this look at a similar subject - ie combining less expensive output iron for better and hopefully cheaper results?
And how well would this strategy work? I have a fair number of smaller output transformers...
http://www.audioxpress.com/magsdirx/ax/addenda/media/1960crowhurst.pdf
Ted.
On your search, I came across this Crowhurst article.
I'm not an expert in this area, but does this look at a similar subject - ie combining less expensive output iron for better and hopefully cheaper results?
And how well would this strategy work? I have a fair number of smaller output transformers...
http://www.audioxpress.com/magsdirx/ax/addenda/media/1960crowhurst.pdf
Ted.
Hi Andy,
As my memory goes if the output impedance is equal to Ra, that gives the highest efficiency but also maximum distortion. (I take it that by optimum performance you mean lowest distortion.) You will usually find that for triodes the load impedance is many times the Ra, whereas for pentodes it is much lower, to get away from the "being equal" point. But tubes do not have fixed Ra under large signal conditions; the scene is more involved there. Minimum distortion points also differ depending on which harmonic you look at. Best is to stick somewhere close to published data, especially where graphs for measured distortion/Ra/Rl is available, e.g. with the EL34 and 6L6, but also others.
Regards.
As my memory goes if the output impedance is equal to Ra, that gives the highest efficiency but also maximum distortion. (I take it that by optimum performance you mean lowest distortion.) You will usually find that for triodes the load impedance is many times the Ra, whereas for pentodes it is much lower, to get away from the "being equal" point. But tubes do not have fixed Ra under large signal conditions; the scene is more involved there. Minimum distortion points also differ depending on which harmonic you look at. Best is to stick somewhere close to published data, especially where graphs for measured distortion/Ra/Rl is available, e.g. with the EL34 and 6L6, but also others.
Regards.
I've not done anything but think about it so far. To busy with finding a car and finishing my homebrew oil boiler.
I am running a toroidal on a 807 amp with voltages of 350V without issue. I would think they will take 500V without issue.
As far as I know the standard mains toroidals are not bifilar, but wound in lairs. The reason they perform relatively well despite of this is because the coils completely enclose the core and so prevent leakage inductance, which is a major issue with EI's. Interwinding capacitance can be an issue, so I wouldn't recommend their use with pentodes where output impedance is high. They seem to work best if wired in one direction over the other (on the primary) and can ring because of their high bandwidth. A scope would be advised to tune them in use.
Shoog
I am running a toroidal on a 807 amp with voltages of 350V without issue. I would think they will take 500V without issue.
As far as I know the standard mains toroidals are not bifilar, but wound in lairs. The reason they perform relatively well despite of this is because the coils completely enclose the core and so prevent leakage inductance, which is a major issue with EI's. Interwinding capacitance can be an issue, so I wouldn't recommend their use with pentodes where output impedance is high. They seem to work best if wired in one direction over the other (on the primary) and can ring because of their high bandwidth. A scope would be advised to tune them in use.
Shoog
I have unwound a few secondaries in my time. The winding is quite complex - but i'am not certain I would call it bifilar. Can't say anything about the primaries as I have never touched them on mine.
Hows your plans progressing ?
The great thing about using cheap unfamiliar parts is that you can lash something together cheaply to see how it sounds. I have seen people study components for months and spend endless amounts of money on their first project. Truth is most of the sound is in the circuit and the chances of building a top flight circuit first time is not great. Much better to experiment on the cheap and when you understand something a little better you can start to make the right decisions about where to spend your money. All my projects have tended to cost less than what most people would spend on one output transformer, but I would say I am a lot further along the path to "ideal" than the one off builders. I would say that my next project will be just as cheap but even better sounding. Most of the bits will come from a 1930's transmitter which I pulled out of the local recycling centre.
Expect to build at least four amps before you settle back in your armchair and say you have arrived. Thats a hell of a lot of money in boutique parts along the way. Having spent the time you'll be pleasantly surprised at how much you will have learned along the way.
Shoog
Hows your plans progressing ?
The great thing about using cheap unfamiliar parts is that you can lash something together cheaply to see how it sounds. I have seen people study components for months and spend endless amounts of money on their first project. Truth is most of the sound is in the circuit and the chances of building a top flight circuit first time is not great. Much better to experiment on the cheap and when you understand something a little better you can start to make the right decisions about where to spend your money. All my projects have tended to cost less than what most people would spend on one output transformer, but I would say I am a lot further along the path to "ideal" than the one off builders. I would say that my next project will be just as cheap but even better sounding. Most of the bits will come from a 1930's transmitter which I pulled out of the local recycling centre.
Expect to build at least four amps before you settle back in your armchair and say you have arrived. Thats a hell of a lot of money in boutique parts along the way. Having spent the time you'll be pleasantly surprised at how much you will have learned along the way.
Shoog
Wise words Shoog,
I like the path your audio venture has taken and would be similar in approach myself although not as experienced as you.
Praise be to recycling centres - I have retrieved so much from them it makes me wonder what gems I'm missing by not visiting them more often.
I have nearly rebuilt the power stage of the Rogers Cadet ala "Baby Huey" circuit - should be plugging in soon.
Interesting to hear what you say about toroid windings - I must check again to see if it was the primary that was wound bifilar.
John
I like the path your audio venture has taken and would be similar in approach myself although not as experienced as you.
Praise be to recycling centres - I have retrieved so much from them it makes me wonder what gems I'm missing by not visiting them more often.
I have nearly rebuilt the power stage of the Rogers Cadet ala "Baby Huey" circuit - should be plugging in soon.
Interesting to hear what you say about toroid windings - I must check again to see if it was the primary that was wound bifilar.
John
While we are on toroids, I noticed that there are some output transformers of that kind available. A Dutch gentleman named Van der Veen makes them amongst others.
My question is how on earth do I design for low (or a particular) leakage reactance, p-s capacitance etc. The classic Crowhurst graphs as per Radio Designer's Handbook cannot work because of the different topology and difficulty to wind in defineable layers. How many secondaries etc? Or does one just have it wound with say one secondary and it will be at least better than classic ones? I can understand that it is more efficient etc, but not how to design to specific specs. Trial-and-error? - and if one found the right design, how consistent would duplicates be considering lack of normal defineable single layers?
Anyone out there know (articles, references, etc.)?
Regards.
My question is how on earth do I design for low (or a particular) leakage reactance, p-s capacitance etc. The classic Crowhurst graphs as per Radio Designer's Handbook cannot work because of the different topology and difficulty to wind in defineable layers. How many secondaries etc? Or does one just have it wound with say one secondary and it will be at least better than classic ones? I can understand that it is more efficient etc, but not how to design to specific specs. Trial-and-error? - and if one found the right design, how consistent would duplicates be considering lack of normal defineable single layers?
Anyone out there know (articles, references, etc.)?
Regards.
Shoog,
Here's something which might appeal to your frugophile nature
http://www.diyaudio.com/forums/showthread.php?s=&threadid=96084
John
Here's something which might appeal to your frugophile nature
http://www.diyaudio.com/forums/showthread.php?s=&threadid=96084
John
Hi Shoog,
I plugged in my "Baby Huey" rebuild of Rogers Cadet amp and even though it needs a few kinks ironed out it appears to be stunning - much, much better than the Cadet output stage it replaced. And that's using the same trafos, both PS & output as was used in the Cadet - just shows the importance of circuit as opposed to exotic parts. Well worth a try.
Having said that, I will probably chase the last drop of improvement I can squeeze out of this circuit with battery/LED biasing of output stage, toroid OPTs, maybe SMPS supply as per referenced thread above.
Let the experimenting begin.
John
I plugged in my "Baby Huey" rebuild of Rogers Cadet amp and even though it needs a few kinks ironed out it appears to be stunning - much, much better than the Cadet output stage it replaced. And that's using the same trafos, both PS & output as was used in the Cadet - just shows the importance of circuit as opposed to exotic parts. Well worth a try.
Having said that, I will probably chase the last drop of improvement I can squeeze out of this circuit with battery/LED biasing of output stage, toroid OPTs, maybe SMPS supply as per referenced thread above.
Let the experimenting begin.
John
Good to hear you've got a result. Its important to get a result fast in order to maintain the excitement.
Circuit Circuit every time.
I would try the LED biasing or if you do try the toroidals, the CCS biasing.
I like the idea of converting a SMPS for HV, but I have certain reservations. My understanding of SMPS is that they are extremely sensitive to circuit layout and component choice. Lots of potential for expensive mistakes.
Shoog
Circuit Circuit every time.
I would try the LED biasing or if you do try the toroidals, the CCS biasing.
I like the idea of converting a SMPS for HV, but I have certain reservations. My understanding of SMPS is that they are extremely sensitive to circuit layout and component choice. Lots of potential for expensive mistakes.
Shoog
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