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Best 300B SE OPT?

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#803
The F3CC0125 core would be the one to make a proper 300B OPT without many limitations and would need 4C core for 38 mm x 35 mm core area. At those prices the Monolith SA-9 is cheaper!
The other 2 available are way too small. The F3CC0040 could be used for SE IT transformers or small PP OPT.
But also the others that are not stocked. The other problem with nanocores is their poor stacking factor. The 38 x 35 would be physically 13.3 cm^2 but the effective area is 10.38 cm^2 (i.e. only 78% vs 90-95% of FeSi and Nickel). That is.....
Looks like the only way is to buy directly from factories.
 
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#805
Grid01 said:
Hi jedibones, seems you have been reading a great deal about transformer cores and their influence on sound .
After a long journey through just about everything I settled on parafeed Nickel 78% (Mu Metal ) !

To me Amorphous from NP Acoustics ( not sure if they are still going ) and the Monster AMCC100 from Ongowoski sounded revealing but more Hifi than music and was more happier with M3 C core's than Amorphous , Nanocrystalline ( Metglass ) from General Transformers ( was Noguchi ) Japan was hyper detailed like a Naim SS amp on steroids and lacked bass both the FW24WS & FM=10WS-3525 are the models I used , the detail was immense but in the end not natural enough ie true to the original recording . Nickel seems very natural sounding to me preserving both the Timbre and voice of the original music .
I did try Permalloy Double C cores with pure Silver wire primary and secondary and parefeed %78 Nickle / copper wire both of these had the most natural sound for me both in correct timbre and dynamics .
The Silver Permalloy were expensive but nothing like Kondo Japan prices AKA Ongaku or the A/N UK custom price both very overpriced quick frankly and the 2A3 with efficient speakers much preferable to 1000v / DC trying to etch out decent Audio from a 211 transmission tube , we ditched ours years ago .
All the Japanese ones from Hashimoto and Tamura I tried let go in the lower registers ie Tamura F-913A and Hashimoto H-20-3,5U neither were flat to 20Hz and the H203S the bottom register was completely missing in action and yet a reviewer remarked on its good bass , go figure !
Ongowoski make a M23 Cold Rolled Silicon Steel transformer some call Super or Ultra HiB its a 3kg Double C core monster and had it custom wound , now this is a doozy and am more satisfied with it's sound than most other stuff I have tried other that parafeed Nickel or C core Silver and much cheaper than Audio Note for their offerings .
EI core HiB M23 I also like its a bit warmer in the
Grid01 said:
Hi jedibones, seems you have been reading a great deal about transformer cores and their influence on sound .
After a long journey through just about everything I settled on parafeed Nickel 78% (Mu Metal ) !

To me Amorphous from NP Acoustics ( not sure if they are still going ) and the Monster AMCC100 from Ongowoski sounded revealing but more Hifi than music and was more happier with M3 C core's than Amorphous , Nanocrystalline ( Metglass ) from General Transformers ( was Noguchi ) Japan was hyper detailed like a Naim SS amp on steroids and lacked bass both the FW24WS & FM=10WS-3525 are the models I used , the detail was immense but in the end not natural enough ie true to the original recording . Nickel seems very natural sounding to me preserving both the Timbre and voice of the original music .
I did try Permalloy Double C cores with pure Silver wire primary and secondary and parefeed %78 Nickle / copper wire both of these had the most natural sound for me both in correct timbre and dynamics .
The Silver Permalloy were expensive but nothing like Kondo Japan prices AKA Ongaku or the A/N UK custom price both very overpriced quick frankly and the 2A3 with efficient speakers much preferable to 1000v / DC trying to etch out decent Audio from a 211 transmission tube , we ditched ours years ago .
All the Japanese ones from Hashimoto and Tamura I tried let go in the lower registers ie Tamura F-913A and Hashimoto H-20-3,5U neither were flat to 20Hz and the H203S the bottom register was completely missing in action and yet a reviewer remarked on its good bass , go figure !
Ongowoski make a M23 Cold Rolled Silicon Steel transformer some call Super or Ultra HiB its a 3kg Double C core monster and had it custom wound , now this is a doozy and am more satisfied with it's sound than most other stuff I have tried other that parafeed Nickel or C core Silver and much cheaper than Audio Note for their offerings .
EI core HiB M23 I also like its a bit warmer in the mids than C cores which I found a tad cold in this department .
I have given up now on most of the Exotic metals now as a fad and an expensive one .
I spent many years in professional broadcasting , monitoring live audio on transmission and being recorded, including many live musicians in the field on Nagra's and Studer 870's has given me a little bit of an edge IMHO to correct timbre and dynamics of live and replayed audio and music .

​

Click to expand...
One Caveat the 5K Tamura used in Ultra Linear Mode with a KT series of tubes will get down to 20Hz as Global Feedback enters the equation ,with a few tweaks .
Click to expand...
 
#806
45 said:
Looks like the only way is to buy directly from factories.
Click to expand...
I bought a LOT from China via marketplaces like Aliexpress/Alibaba, or just straight, even from bizarre supplier, which had no web site, never responding phone number, only generic e-mail on 123456789@qq.cn domain. My custom-sized amorphous / nano cores are from Anhui Lizhi Magnetic Material. On Alibaba you have buyer protection, you can check a feedback from other buyers, shipment tracking. In short, I see no problems whatsoever to order something straight from Chinese companies.
 
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#809
45 said:
The F3CC0125 core would be the one to make a proper 300B OPT without many limitations and would need 4C core for 38 mm x 35 mm core area. At those prices the Monolith SA-9 is cheaper!
The other 2 available are way too small. The F3CC0040 could be used for SE IT transformers or small PP OPT.
But also the others that are not stocked. The other problem with nanocores is their poor stacking factor. The 38 x 35 would be physically 13.3 cm^2 but the effective area is 10.38 cm^2 (i.e. only 78% vs 90-95% of FeSi and Nickel). That is.....
Looks like the only way is to buy directly from factories.
Click to expand...
Monolith Magnetics , Amorphous , Metglas nanocrysalline and Summit M6 range are probably the best of type you are likely to encounter commercially anywhere on the planet today .
 
#810
Jaap said:
Nobody likes toroids ?
Click to expand...

I also wonder Jaap. The toroid trannies I have seen have cores that are too small. However, I would certainly
be a fan of one built with sufficient core size. See next paragraph.

An important point is any OPT must have a balanced frequency response (FR). Maybe I missed it, but
I have not yet to read an actual test of an OPT for accurate, balanced frequency response.

If interested, build a circuit, without any global negative feedback, and with large coupling capacitors(s), that checks
the frequency response, by listening as well as measurements. It does not have to be absolutely perfect,
but one/some will be more accurate than others.

cheers

pos
 
#812
https://www.ogonowski.eu/transformers/single-ended/
This Guy will wind with giant AMCC 100 cores or large Ultra / Super HiB M3 Double C cores or EI cores M3 , they do sound very nice to my ears the Amorphous is HiFi sounding to me but others may prefer hearing every pin drop rather than the ebb and flow of an evening's listening , his Ultra/Super HiB are superb and quite frankly 20 watt outclass the Hashimoto I tried certainly in the bass region by a country mile , flat to 20Hz will not be an issue or -3dB at 10 Hz this is real and not just tested with a 600 ohm load and no tube in circuit , the HF is 60KHz -3dB but you can request custom winds.
As for Nickel you will have to custom wind this stuff , Sowter do a mixed Nickel parafeed transformer not pure Nickel but a mix with M6 metal similar to Magnequest pinstripe offering who seems to have retired .
I have inclosed a picture of the large Amorphous from Edis Ongowoski , this is a very large unit as this much Amorphous is needed to get down to 20Hz at 8 -10 watts , his metal is sourced from Germany from memory not china , and comes with transformer covers , FEDEX only .
 

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#816
andyjevans said:
i looked at the Ogonowski website and the cheapest SE OPT is quite reasonable, $109. Says 2.5K so I'll ask about 3.5K and 5K.

https://www.ogonowski.eu/transformers/single-ended/lo-se25-5/
Click to expand...
(Try his Double C core M3 LO SE25-3 for 2a3 or 300b , $ 175 3K primary 30H a custom wind will cost a bit more .
look closely as some are double C core and others , EI are also nice 0.3 lams are M5 and cheaper , Hashimoto 3.5K H-20-3.5S can only manage 13H at 2.5K and 18H at 3.5K flat to 40Hz and the 5K/7K H -20 -7U 23H at 5K only flat to 40Hz according to the spec sheet so these 20 watt models do not have -1dB at 20 Hz response from what I can see on the spec sheets.
So quite a few reviewers don't seem to know what -20Hz @ 1dB actually means and just wax lyrical about excellent bass response go figure .
 
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#817
18H driven with a 800R gives an unloaded low frequency cutoff @ 7Hz. At loaded secondary it is even lower.
So the causes of misunderstanding between primary inductance and frequency response might be:
-They're measuring the FR at higher generator impedance (unspecified in the datasheet)
-They have measured the peak inductance at higher flux density, while the FR due to low core excitation results into lower inductance
-Related to possibility No.2, a high unlinearity from the core assembly. High hysteresis loss cores with little airgap cause this.
 
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