You should pick one or the other.
The 300B is going to work better with more voltage than a 2A3 would need. The 300B will also tend to run a little more plate current, which is a factor in the design of the output transformer.
The whole nano-crystalline core thing is a brand of a product from Hitachi as far as I can tell.
Some thoughts
Usually a larger core is needed to handle more bass, but maybe less sweet for the midrange and treble. Something to consider is that often we use SET amps for midrange and treble, and use another amp and separate speakers for the bass. Thus, maybe a larger transformer would be less desirable.
Another issue is what impedance core to use. 300B tubes love 5k or so for lowest distortion. One of the best ways to have the flexibility for this is to get an OPT with 16 ohm, 8 ohm and 4 ohm taps. Then if you want a higher impedance (i.e., ~5k ohms), you can run 8 ohm speakers on the 4 ohm tap, and easily change with a flip of a knob to the lower impedance for higher output, with higher distortion.
It seems that you are fixed on series feed from your diagram. But you should consider parallel feed as well, which can be run as an autoformer if the windings are capable of higher voltage. This permits smaller transformers and makes the best metallurgy more affordable (i.e., permalloy - very high permeability).
Retsel
"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."
Usually a larger core is needed to handle more bass, but maybe less sweet for the midrange and treble. Something to consider is that often we use SET amps for midrange and treble, and use another amp and separate speakers for the bass. Thus, maybe a larger transformer would be less desirable.
Another issue is what impedance core to use. 300B tubes love 5k or so for lowest distortion. One of the best ways to have the flexibility for this is to get an OPT with 16 ohm, 8 ohm and 4 ohm taps. Then if you want a higher impedance (i.e., ~5k ohms), you can run 8 ohm speakers on the 4 ohm tap, and easily change with a flip of a knob to the lower impedance for higher output, with higher distortion.
It seems that you are fixed on series feed from your diagram. But you should consider parallel feed as well, which can be run as an autoformer if the windings are capable of higher voltage. This permits smaller transformers and makes the best metallurgy more affordable (i.e., permalloy - very high permeability).
Retsel
"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."
Single Ended Output Transformer Choices
So Many Choices, Electra-Print EI core , Perfectusaudio M3 GOSS & Double C Core ,Amorphous Double C core , ISO ( Tango) FC20s Orient C C core
So Many Choices, Electra-Print EI core , Perfectusaudio M3 GOSS & Double C Core ,Amorphous Double C core , ISO ( Tango) FC20s Orient C C core
Attachments
Hi Walter,
I agree with your comment to a certain degree , that is why I test my amplifiers with a Tektronix TM515 with the OPT in circuit rather than (Rp=Zp, -2dB) fed of the 600 ohm tap
This process in rather time consuming but a much more accurate measurement of real life performance . The Tango's still outperform the Electra-Print and all the other EI cores I have come across.
The bass response is a strong point of the Electra- Print's but the frequency response above 25kHz of the ISO puts it in a class of its own. My own Amorphous cores have great mids and top end but still don't have the bass response of the M3 GOSS Double C cores or Electra-Prints, however the very low insertion loss of the ISO Tango and the Cut C Core HiB GOSS makes for a very revealing piece of iron
Cimemag EI core M6 CM13111 are excellent performers (as in the latest Eddy Current Amp ) but one must generally purchase in orders of the magnitude of 10+
Nanocrystaline cores produce wonerfull mids and top end but bass is MIA unless cores are massive ... HiB M3 .23mm C cores really work well with Single Ended Amplifiers as do Nippon HiB steel C cores ISO Tango use , Radiometal 50% Nickel need to be quite large and expensive, buying this metal is difficult in small quantities and quite frankly IMHO stick with HiB M3 laminations as you will still get the very high frequency extension and low insertion loss with out having to build large chassis to accommodate the C core sizes required for Radiometal or Nano because of its problems with DC saturation
Amorphous and Nano are well suited to Full range drivers like Lowthers etc where sub 30Hz is MIA IMHO
I agree with your comment to a certain degree , that is why I test my amplifiers with a Tektronix TM515 with the OPT in circuit rather than (Rp=Zp, -2dB) fed of the 600 ohm tap
This process in rather time consuming but a much more accurate measurement of real life performance . The Tango's still outperform the Electra-Print and all the other EI cores I have come across.
The bass response is a strong point of the Electra- Print's but the frequency response above 25kHz of the ISO puts it in a class of its own. My own Amorphous cores have great mids and top end but still don't have the bass response of the M3 GOSS Double C cores or Electra-Prints, however the very low insertion loss of the ISO Tango and the Cut C Core HiB GOSS makes for a very revealing piece of iron
Cimemag EI core M6 CM13111 are excellent performers (as in the latest Eddy Current Amp ) but one must generally purchase in orders of the magnitude of 10+
Nanocrystaline cores produce wonerfull mids and top end but bass is MIA unless cores are massive ... HiB M3 .23mm C cores really work well with Single Ended Amplifiers as do Nippon HiB steel C cores ISO Tango use , Radiometal 50% Nickel need to be quite large and expensive, buying this metal is difficult in small quantities and quite frankly IMHO stick with HiB M3 laminations as you will still get the very high frequency extension and low insertion loss with out having to build large chassis to accommodate the C core sizes required for Radiometal or Nano because of its problems with DC saturation
Amorphous and Nano are well suited to Full range drivers like Lowthers etc where sub 30Hz is MIA IMHO
Is the data sheet for that transformer saying it will be 2dB down at 2W/35Hz on the 5K tap?
The inductance specs, though somewhat hard to decipher, would seem to support the notion that these are not great transformers for low frequency reproduction.
The FC-30-10S is going to be worth the extra money.
I noticed one of your amplifiers uses a Cinemag OPT in a 2A3 circuit, presumably a custom. Any comments on the performance?
Hi Walter, looks fine but in the end measuring the amp while under load suits me with the TM 515 ,even if it takes time to join all the dots , Peter Millet has a card option for measuring complete freq response , nice price also ,with a decent sound card in your computer , have a look at his page PM Millet google him
Hi Walter,
Will post plots when this is up and running as the TM515 is very good but requires many plots and then transposed onto XL
This devise from PM Millet will make life easier to post results on my website with test data etc
Soundcard Interface
Will post plots when this is up and running as the TM515 is very good but requires many plots and then transposed onto XL
This devise from PM Millet will make life easier to post results on my website with test data etc
Soundcard Interface
I'm buying OPT's for my next amp and I'm having a hard time making up my mind. Short list is Hashimoto (H-20-3.5U), Monolith or AE Europe. Specs look similar as are prices.
I can't find a lot on AE, but they are local so easy to deal with, as are Monolith. I like having the two taps (2.5k and 3.5k) like on the Hashimoto.
Any advice on how to make a decision? Any experience with AE OPT's?
Thanks
I can't find a lot on AE, but they are local so easy to deal with, as are Monolith. I like having the two taps (2.5k and 3.5k) like on the Hashimoto.
Any advice on how to make a decision? Any experience with AE OPT's?
Thanks
AE is Pieter who posts often here. Good quality of course - not sure of waiting times but I don't think they're off the shelf. I may be wrong. Monolith is excellent if you have the cash. I'm guessing better than Hashimoto, but no first hand experience. If you want something very good and good value I'd continue to recommend NP Acoustics in Vietnam for their amorphous core OPTs. Very nice people too. I use them and love their amorphous core plate chokes as well.
