Hi there and thanks for stopping by.
I built a phono pre using 5842 tubes designed by Joe Tritschler. I'm using it with a Yamaha MC-1s cartridge and a SUT I also built using some Shure audio transformers. It sounds very good. Quiet, revealing, and steady through most all of the frequency response except that it lacks some bass authority. It does not lack much at all and I am wondering if using the step up transformers would change the loading the cartridge wants. Without plugging in numbers, can anyone tell me if this is a credible theory and maybe give me a little bit of theory I could use to figure out possible adjustments?
Thanks to anyone who might take the time to help.
I built a phono pre using 5842 tubes designed by Joe Tritschler. I'm using it with a Yamaha MC-1s cartridge and a SUT I also built using some Shure audio transformers. It sounds very good. Quiet, revealing, and steady through most all of the frequency response except that it lacks some bass authority. It does not lack much at all and I am wondering if using the step up transformers would change the loading the cartridge wants. Without plugging in numbers, can anyone tell me if this is a credible theory and maybe give me a little bit of theory I could use to figure out possible adjustments?
Thanks to anyone who might take the time to help.
Do you know the ratio of the Shures? They might not have the ideal ratio for a MC cart. (The ratio might be too high.) Have a look at this link. It's a bit intimidating at first but read it through a few times. You might need to load the Shure's secondaries a bit with some resistance.
http://www.kandkaudio.com/applications-guide/
Cheers, S.
http://www.kandkaudio.com/applications-guide/
Cheers, S.
Hou much is the ratio of step up? Which type is?
The load seen frm MC il the Z strictly related to a load connected to the secondary of step up and his ratio
The reflected impedance is given from the formual Zin phono / ratio x ratio.
P.e. 47.000 ohm ( standard load for phono) / 100 ( if the ratio is 10) = 470 ohm
This is theoric bcause at low frequency the Z of the trafo tend to go low ( loss of bass) and at high frequency is possible to have a resonance peak on audible frequencies (trebele increase) .
The MC-1 ha 30 ohm of internal impedance so if we consider 10 times the ratio for a good load , the ipothetic 470 ohm is fine.
But if the trafo has 1:15 the reflected is 47.000/225 = 208 ohm. Sufficent probably ad mid frequencies
If the trafo hasn't a proper impedance at low frequency the bass response can be poor
Of course the trimming of the load on secondary is a good way to fix the right value ( within a certain range) for a better results.
This as general info.
Walter
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One more information.
Regarding the Capacitance in input that is in parallel to the Rload of the step up and it is strictly related ot the tube spec; with 5842 you have 1,8 pF with a gain of 40 ( just an example) you have around 70 pF
Plus the capacitance of the cable connection if you use a separate box.
The total value can have an impact on high frequencies response of the trafo
Regarding the Capacitance in input that is in parallel to the Rload of the step up and it is strictly related ot the tube spec; with 5842 you have 1,8 pF with a gain of 40 ( just an example) you have around 70 pF
Plus the capacitance of the cable connection if you use a separate box.
The total value can have an impact on high frequencies response of the trafo
So, Here's some numbers for you, thanks for the reply...
The transformers are 1:15
The Phono stage had a 100K load resistor
I changed the resistors out to 68K so ZIN Phono/ratio^2=68000/225=302=30ohms*10
Are my calculations right?
Whether or not what I did made a real difference, it really sounds pretty nice. That is the point, right?