>we have had trouble getting the transformers
>to misbehave except when they are are working
>in complete units.
Then you assemble the amps here ?
(I was thinking you had the whole package made in China)
Assuming your test jig is basically a 'whole unit', perhaps
the problem is other than with the xfmrs themselves, but
something else in the circuit or assembly that in the end
manifests through the xfmr.
>to misbehave except when they are are working
>in complete units.
Then you assemble the amps here ?
(I was thinking you had the whole package made in China)
Assuming your test jig is basically a 'whole unit', perhaps
the problem is other than with the xfmrs themselves, but
something else in the circuit or assembly that in the end
manifests through the xfmr.
scott wurcer said:
Well, at least your car gets to be mildly demagnetized on a regular basis. Just drive away really slow.....
Are they mounted on a metal case? Did you consider to put insulators under the transformer and under bolts/nuts grounding a single leg only?
> Alas, the times that 'Made In USA' or 'Made In West Germany' really ment something are long bygone...
I can share with you what our experiences were with transformers a couple of years ago.
We were sourcing 1500VA toroidals for 100W Class A monoblocks, and started off with a couple of well known (West) German suppliers. Either they were simply not interested in doing quantities below 100, or they were not particularly interested in all special requirements such as shields, bifilar winds, ...... We did get a pair made eventually, but they were not particularly brilliant.
Problem with Chinese suppliers is not that they don't have the know-how. Quite the contrary. They are also only interested in production quantities (preferrably in thousands), and you need to find the right supplier, as quality varies a lot (I guess same as everywhere else).
In the end we settled for a East European supplier. They were good, but not perfect (simple wiring mistakes, wrong labelling, ....). The transformers performed almost spot on according to spec, which is what it counts in the end, I guess.
Patrick
I can share with you what our experiences were with transformers a couple of years ago.
We were sourcing 1500VA toroidals for 100W Class A monoblocks, and started off with a couple of well known (West) German suppliers. Either they were simply not interested in doing quantities below 100, or they were not particularly interested in all special requirements such as shields, bifilar winds, ...... We did get a pair made eventually, but they were not particularly brilliant.
Problem with Chinese suppliers is not that they don't have the know-how. Quite the contrary. They are also only interested in production quantities (preferrably in thousands), and you need to find the right supplier, as quality varies a lot (I guess same as everywhere else).
In the end we settled for a East European supplier. They were good, but not perfect (simple wiring mistakes, wrong labelling, ....). The transformers performed almost spot on according to spec, which is what it counts in the end, I guess.
Patrick
john curl said:
Innaresting cast of characters...
It's always educational to learn that things aren't always what they seem; It just makes me want to go take a second look at what had been so cleverly put into question. At least I got the devices back.
Happy trails.
Sorry Scott, I thought you were talking about this Sat nite, after AES. SY says that you meant the 18th or so, for Burning Amp. Mike, I have no idea of what you are talking about.
john curl said:
Yes Saturday the 18th, even with the losses of last week I'm still up for it but I am only comming in Saturday at 9:30 AM and leaving Monday at 8:30AM.
PMA, the next generation of JC-1 will probably have 2 followers. It was recommended years ago, but I vetoed it in order to keep the stage count at a minimum. Then I used single ended input for my home systems and considered single ended a more optimum way to drive the amp. With the CTC Blowtorch, however, I now use the balanced input on the power amp, so I now am more concerned with optimum, low noise input, rather than stage count. The next headache, is finding fet dual pairs that are affordable in production.
> Then I used single ended input for my home systems and considered single ended a more optimum way to drive the amp.
Would you care to elaborate why ?
What are the disadvantages of the complementary buffer BUFF2 ?
(other than the obvious one -- higher input capacitance)
Patrick
Would you care to elaborate why ?
What are the disadvantages of the complementary buffer BUFF2 ?
(other than the obvious one -- higher input capacitance)
Patrick
Wavebourn, if I took 16 of the largest Edcor power transformers and paralleled them together, I would get the rating of what we are using now (1.9KW) in the JC-1, and it would cost over $500 for each group. Plitron would cost about the same for an equivalent low noise transformer. This would, at least, add $1000 to the retail price of the amplifier.
Single ended did not require ANY buffers in the input and therefore less stuff to go through. There is a switch that removes the buffer from the audio circuit on the back of the amp.
Patrick,
probably misunderstanding, John meant single ended input of the power amp. You and I mean to compare single ended CCS biased buffer (BUFF1) with single ended complementary buffer (BUFF2). I believe that we all agree here that the BUFF2 is a better option, provided we have appropriate complementary JFETs available.
probably misunderstanding, John meant single ended input of the power amp. You and I mean to compare single ended CCS biased buffer (BUFF1) with single ended complementary buffer (BUFF2). I believe that we all agree here that the BUFF2 is a better option, provided we have appropriate complementary JFETs available.
PMA, now I see. Of course, the complementary buffer is better for drive and distortion, BUT it is much harder to get matched complementary jfets, and the resulting offset will affect the servos. It is possible however.
Thank you Pavel for clarifying for us. You read John's mind much better than I can.
😉
We all agree that the complementary is better for drive and distortion, but it has much higher input capacitance because of the P-JFET. Also the typical 2SJ74 is not a true complementary to 2SK170, the former having a higher transconductance at the same bias.
In the link below which I posted here once, I tried to address the above issue with a few variations.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=128571
I sincerely hope John could take a few minutes to have a critical look and comment.
(Pls read the article in post #2.)
Patrick
😉
We all agree that the complementary is better for drive and distortion, but it has much higher input capacitance because of the P-JFET. Also the typical 2SJ74 is not a true complementary to 2SK170, the former having a higher transconductance at the same bias.
In the link below which I posted here once, I tried to address the above issue with a few variations.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=128571
I sincerely hope John could take a few minutes to have a critical look and comment.
(Pls read the article in post #2.)
Patrick
Hi,
in PMA's buf2, can R3 and/or R4 be trimmed to adjust the parameters of slightly dissimilar P & N complements?
in PMA's buf2, can R3 and/or R4 be trimmed to adjust the parameters of slightly dissimilar P & N complements?
At a bias current of say 6-8mA, 2SK170V has a typical transconductance of 33mS, and 2SJ74 40mS. So you are correct in that the current contributions of the K device and the J device can be balanced by using a source resistor for the 2SJ74 which is 5 ohm higher than that of the 2SK170. But that does not mean that this guarantees optimal cancellation of (even order) distortions.
And of course, the Idss of the devices should be so chosen to give the same bias current with their corresponding source resistors. This means that their Idss should be different by a defined amount, depending on the value of the source resistors chosen.
So a simple 2-transistor circuit is not that simple after all.
Patrick
And of course, the Idss of the devices should be so chosen to give the same bias current with their corresponding source resistors. This means that their Idss should be different by a defined amount, depending on the value of the source resistors chosen.
So a simple 2-transistor circuit is not that simple after all.
Patrick
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