tubetvr said:
With respect to measurement conditions, I know for a fact James quote their specs at 4v p-p RMS, this is a rather standard practice used by most transformer manufacturers, (I believe) including Tamura.
The test report at sactthailand says it uses 18v RMS! which may explain the ultra bad performance by Hammond.
Keith
Just to add another choice of priceworth but real good german trannys:
http://www.roehrentechnik.de/html/ausgangstrafos.html
Give them a try!
Franz
http://www.roehrentechnik.de/html/ausgangstrafos.html
Give them a try!
Franz
I have seen 2V, 4V Primary voltage and many manufacturers where the voltage is not specified. if James use 4V why do they not say so on their WEB site?
Sactthailand tested all transformers using the same voltage, 18V RMS Secondary voltage equal to 5W so the test is valid, this is still well below max power, shouldn't you expect that a transformer works well even at full power?
As the performance of Hammond is bad at high frequencies which are less affected by the applied voltage I would not expect that it would be much better at lower voltage, I think it is well known that Hammond is not the high frequency champion.
It is a pity that manufacturers dont give full measurement conditions so it would be possible to compare performance, most manufacturers dont give any information about measurement conditions at all.
Among the manufacturers I have found Tango and Plitron that give quite extensive data but others seem to be reluctant to show the full performance.
Regards Hans
tubetvr said:
James publish their test conditions in a separate spec sheet that comes with their transformers. A copy of these can be found on Pete Millett's website. http://www.pmillett.addr.com/images/js6123hs.PDF
You will see a 4V RMS is applied at the primary, and yes, you were right that I mixed up the 4v @ pri and 18v @ secondary part ...
Other important info such as pri inductance is also in the spec sheet, why they dont publish more data on their website beats me too.
Keith
so finally whats the answer to the original question ? James or Hammond ?
What's it gonna be, Ashok ?
What's it gonna be, Ashok ?
Hi Percy,
I pondered a lot and finally decided to buy the James transformer(6123HS). One of the reasons ( not the most important one )
was that it was much lighter than the Hammond transformer. Just two of these weighed 7kilos and my suitcase eventually weighed 37 Kilos ! Caused a lot of trouble eventually !
The trafos are still lying on my table. It' sgoing to take a whole lot of effort to build this thing. I also bought some 845 tubes !
Since the trafo has different taps I can use different tubes with the same unit. I'll build it as simple as possible so that I can decide which tube I want to settle for before splurging on an expensive chassis.
The response graphs included with each transformer look pretty decent. I will however test them myself before putting them into an amp. It has taps for 5k, 3.5K and 2.5K.
I have an old Scott amp to compare with.
Thanks to everybody for all their opinions.
Cheers,
Ashok.
I pondered a lot and finally decided to buy the James transformer(6123HS). One of the reasons ( not the most important one )
was that it was much lighter than the Hammond transformer. Just two of these weighed 7kilos and my suitcase eventually weighed 37 Kilos ! Caused a lot of trouble eventually !
The trafos are still lying on my table. It' sgoing to take a whole lot of effort to build this thing. I also bought some 845 tubes !
Since the trafo has different taps I can use different tubes with the same unit. I'll build it as simple as possible so that I can decide which tube I want to settle for before splurging on an expensive chassis.
The response graphs included with each transformer look pretty decent. I will however test them myself before putting them into an amp. It has taps for 5k, 3.5K and 2.5K.
I have an old Scott amp to compare with.
Thanks to everybody for all their opinions.
Cheers,
Ashok.
Test methodology and fallacies
I know it is a wee bit late to add some information into this thread.
However, as it keeps showing up in Internet searches on the James JS-6123HS, I deem it sensible to point out a few facts:
(1) The SAC Thailand Test, if really carried out at 18Vrms on the secondary, is equivalent to an AC power of 20,25W into 16 Ohms, 40,5 W into 8 Ohms and 81W into 4 Ohms - this is not really suitable for most of the devices under their test.
(2) The measurement method for some of the transformer parameters, using a cheap LRC-meter for the purpose, is very error-prone - such measurements are heavily dependent on the resonance frequency of the primary and secondary of the transformer. One can see that nicely in some of the test results, which show values for stray and main reactance which are not in line with the results of other tests shown in the report - one example being the listed stray and main inductances of the James JS-6123HS, which bear no relationship with the ones properly measured in circuit.
Looking at the lack of appraisal of the measurements in the test, SAC Thailands' report does not pay attention to flawed test procedure...and should be taken with more than just one grain of salt - like soo many other test reports - which is a pity, their iron is not bad - only it does not perform soo much superiour to other run-off-the-mill transformers as the test promises.
Best regards,
mb-de
=->
I know it is a wee bit late to add some information into this thread.
However, as it keeps showing up in Internet searches on the James JS-6123HS, I deem it sensible to point out a few facts:
(1) The SAC Thailand Test, if really carried out at 18Vrms on the secondary, is equivalent to an AC power of 20,25W into 16 Ohms, 40,5 W into 8 Ohms and 81W into 4 Ohms - this is not really suitable for most of the devices under their test.
(2) The measurement method for some of the transformer parameters, using a cheap LRC-meter for the purpose, is very error-prone - such measurements are heavily dependent on the resonance frequency of the primary and secondary of the transformer. One can see that nicely in some of the test results, which show values for stray and main reactance which are not in line with the results of other tests shown in the report - one example being the listed stray and main inductances of the James JS-6123HS, which bear no relationship with the ones properly measured in circuit.
Looking at the lack of appraisal of the measurements in the test, SAC Thailands' report does not pay attention to flawed test procedure...and should be taken with more than just one grain of salt - like soo many other test reports - which is a pity, their iron is not bad - only it does not perform soo much superiour to other run-off-the-mill transformers as the test promises.
Best regards,
mb-de
=->
It's about 5 years since the trafo's were bought. They are lying safe in the original box !
Initially the project was delayed due to lack of some components. Then those were bought and only the power transformer and chassis were left. Now I have the transformer but still no chassis.
I will try really hard to get it completed soon. I'm still debating if I should use a MOSFET ( buffer) driver for the 300B. I think SY (?) had mentioned this somewhere. Anyone tried this kind of a circuit?
Cheers.
Initially the project was delayed due to lack of some components. Then those were bought and only the power transformer and chassis were left. Now I have the transformer but still no chassis.
I will try really hard to get it completed soon. I'm still debating if I should use a MOSFET ( buffer) driver for the 300B. I think SY (?) had mentioned this somewhere. Anyone tried this kind of a circuit?
Cheers.
ashok said:
I would use a MOSFET source follower there. A lot of complaints regarding disappointing results from the 300B seem to be related to inadequate grid drive. These big triodes also tend to start pulling grid current even before Vgk actually goes positive. Also, having the capability to slip a bit into Class *2 operation also improves clip behaviour during transient over drive.
I tried the 300B with Lundahl 1623 SE 60mA OPT.
Even though it has a little less wide bandwidth as Plitron, sounds even better than Plitron's toroid 3035 OPT.
Lundahl looks a bit odd but it sounds great!!!!!
Johnny
Even though it has a little less wide bandwidth as Plitron, sounds even better than Plitron's toroid 3035 OPT.
Lundahl looks a bit odd but it sounds great!!!!!
Johnny
The LL1623 is a very good transformer.
I have done some experimentation with various versions of it lately.
One interesting option is to use the push-pull version in parafeed configuration, combined with a suitable anode (plate) choke - a value of 120..150 Henry at 80 mA is sensible for the 300B.
With chokes sourced from Aquablue in Antwerpen/BE I for once could find an (as well measurable advantage) in the LL1623AM-PP over the LL1623PP - and both were significantly superior to the versions airgapped for single end operation with 60...90 ma.
Unconvincing I found the amorphous core versions airgapped for single end operations - they saturated too early in the low frequeny domain, and produced more distortion already at medium excitation....
Best regards,
mb-de
===
I have done some experimentation with various versions of it lately.
One interesting option is to use the push-pull version in parafeed configuration, combined with a suitable anode (plate) choke - a value of 120..150 Henry at 80 mA is sensible for the 300B.
With chokes sourced from Aquablue in Antwerpen/BE I for once could find an (as well measurable advantage) in the LL1623AM-PP over the LL1623PP - and both were significantly superior to the versions airgapped for single end operation with 60...90 ma.
Unconvincing I found the amorphous core versions airgapped for single end operations - they saturated too early in the low frequeny domain, and produced more distortion already at medium excitation....
Best regards,
mb-de
===
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