The posts on OPT characterization have been moved here:OPT Characterization
Please use this thread to discuss OPT's for 300B as the thread's title suggests.
With respect to the Hammonds, they used to be called 1627SE and
1630SE. I remember there being a manufacturing issue with one of these older SE labelled transformers, and a lot of bad reviews and comments due to this issue. Hammond then released the SEA labelled OPTs that were improved. There is very little comment on these new Hammonds. I would be very interested to know if anyone has tried one of these new Hammonds and other quality OPTs in the same 300B circuit and has any comments on them. I believe that Tubelab has done comparisons with the SE version of the Hammonds and a number of other less expensive OPTs, but has not made comment on the quality of the SEA versions.
1630SE. I remember there being a manufacturing issue with one of these older SE labelled transformers, and a lot of bad reviews and comments due to this issue. Hammond then released the SEA labelled OPTs that were improved. There is very little comment on these new Hammonds. I would be very interested to know if anyone has tried one of these new Hammonds and other quality OPTs in the same 300B circuit and has any comments on them. I believe that Tubelab has done comparisons with the SE version of the Hammonds and a number of other less expensive OPTs, but has not made comment on the quality of the SEA versions.
If I remember correctly, the issue was with some of the 1628SE and it caused there to be a hole in the response at 10K or so. This is from memory. Please donchime in members if you know more. I don't think it affected your model. It did give Hammond some bad press for awhile. I want to know more about the newer SEA versions though, as they are different and improved apparently.
I believe Slagle uses high nickel and a special winding technique.
Monolith Magnetics has 4 different types, amorphous being one of them
No way I can swap these out as the topology is different. I think Dave prefers to wind the lower voltage cores and won’t entertain boat anchor builders(unless under 1k). There’s no comparison on either of these to a Hammond SEA among a couple others I won’t mention. I have compared to a few commercial amps and I haven’t come across one yet that does as well. I’d like to think it was my circuit but over the years have attributed 75% of it to be the transformer.
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I just found this, Hammond is the last in the row and has a link to a FR which shows the hole. You have got a good memory!
Erik
In my opinion these test from SAC are surely interesting but are limited. For example there isn't a THD vs frequency test that is very important.
There isn't the type of tube they used ( I don't see any spec) , it seems a triode (from schematic).
Last, these test are for entire circuit, tube + trafo.
Walter
There isn't the type of tube they used ( I don't see any spec) , it seems a triode (from schematic).
Last, these test are for entire circuit, tube + trafo.
Walter
Thanks for the link. This test is on the 1628SE, a transformer with the issue I mentioned. This was a manufacturing defect that the folks doing the SAC comparison may not have been aware of. They probably thought it was a normal example of the transformer and not a manufacturing defect. I think the issue was only with the 8 Ohm tap as well. At any rate, it's not the 1628SEA. The 1628SEA is supposed to be an improved new version of the 1628SE. As far as I know, you can't even buy a 1628SE anymore. It's been several years now that the SEA versions have been produced, but I haven't seen much of anything on them. This may be due to the bad press caused by the defective 1628SE. Input on any of the SEA models would be great.
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In attach some tests I sent in a E88CC thread.
It is a Hammond 1627SE with a KT150, configured UL.
Fig.15 = freq. answer at 1 w , feedback 6 db
Fig.16 = freq. answer at 10 w , feedback 6 dB
Fig.17 = Thd vs freq at 1 w , feedback 6 dB
The results are good, in my opinion; of course the feedback helpsbut it moderate.
Walter
It is a Hammond 1627SE with a KT150, configured UL.
Fig.15 = freq. answer at 1 w , feedback 6 db
Fig.16 = freq. answer at 10 w , feedback 6 dB
Fig.17 = Thd vs freq at 1 w , feedback 6 dB
The results are good, in my opinion; of course the feedback helpsbut it moderate.
Walter
Attachments
They look good. Did you try them Triode connected with the KT150? That is actually an intended upcoming project. Now I'm trying to sort out the OPTs for the 300B. Thanks for the charts. Do you feel that they are an indication of what might be expected from a 300B circuit connected Triode and without feedback?
to tizman
please look here
why not E88C
post 60
there is a tests on circuit with E88C + 300B and three trafos
Regarding the triode connection with KT150 it is fine; I used UL because Hamoond has this option.
For KT150 this is another my project:
Fab Four: 4 x KT150 monoblock
Walter
please look here
why not E88C
post 60
there is a tests on circuit with E88C + 300B and three trafos
Regarding the triode connection with KT150 it is fine; I used UL because Hamoond has this option.
For KT150 this is another my project:
Fab Four: 4 x KT150 monoblock
Walter
I just finished this bad boy using SAC outputs. He custom wound these at 3K with 4 and 8 ohm taps. Rated to run 200mA to max of 400mA. I should have time for listening test to compare the Hammond to the SAC next week. They were $450.00USD/ea shipping was $150.00 very well packed. ~9.5Kg each. I would seriously check his price for a 300B output transformer.
Attachments
MelB, the amp looks great! I am also in Canada, and I can get the Hammonds locally with no shipping required for about $360 CAD all in. Even if the SAC 300B transformers were two thirds the price, at $600 USD a pair, with shipping it would be $750 USD. That's around $970 CAD, and doesn't include tariffs or taxes once it gets to me across the border. Realistically, they would cost at least $1100 CAD. The Hammonds are around a third of the cost, based upon the arbitrary estimate of two thirds the price for SAC 300B OPTs. Which is why I would love good news about the Hammonds. I look forward to your comparison.
I want to build a 300b SE amplifier with 6SN7 as input and I would like to know what are the OPT transformer parameters and I can get it with Nano crystalline core and as some of the earlier replies over the thread stating about big OPT delivering big sound. I don`t mind building a oversized OPT. Please give me the spec. I want to make use of the provision for both 2A3 and 300b. Please suggest me the transformer parameters.
We need to know the circuit and operating parameters, the transformer must be carefully considered, it isn't really a "one size fits all" type of component...
