Relating to this thread https://www.diyaudio.com/forums/ana...-tonearm-linn-lp12-cartridge-suggestions.html
I may move from MM / Mi to a LOMC
I would therefore require a SUT to feed an all valve amplifier chain to get to 3-5mv
Budget perhaps £250 - £500 used but have no experience of SUTs to guide me.
Thanks Rob
I may move from MM / Mi to a LOMC
I would therefore require a SUT to feed an all valve amplifier chain to get to 3-5mv
Budget perhaps £250 - £500 used but have no experience of SUTs to guide me.
Thanks Rob
Rather than offer specific product recommendations, let me discuss a few considerations to keep in mind when selecting a stepup transformer (SUT).
It is sometimes said that an SUT should be matched to the cartridge (or the other way around).
The reason typically given is the need to have an appropriate amount of SUT gain to bring the cartridge's output up to a level that is comfortable for the chosen phono stage.
However, there is another less-known but equally important reason, which is that the low frequency bandwidth and phase response of the SUT depend on both the inductance of the SUT's primary windings, and the net impedance that the primary windings will see, according to the following formula:
f = Z/(2*Pi*L)
where f is the frequency where the amplitude is 3dB down compared to higher frequencies,
L (in henries) is the inductance of the SUT's primary windings
Z (in ohms) is the net impedance
The inductance of the SUT's primary windings should be measured with the secondary windings left open. (Note that a completed SUT may contain internal load resistors across the secondary windings, therefore it is risky to assume that simply because the SUT is not connected to a phono stage, the secondary windings are truly open.)
"Net impedance" in this particular situation means the phono cartridge's source (self) impedance, in parallel with the impedance that is reflected back from the SUT's secondary windings (when connected to a suitable phono stage). Usually the net impedance will be dominated by the cartridge's source impedance.
The mathematical formula tells us that in order to improve the low-frequency capabilities our options are to lower the source impedance (choose a cartridge with less self-impedance), increase the primary inductance of the SUT (increase the number of transformer windings, increase the dimensions of the transformer core, or use a higher-permeability material for the transformer core).}
In a nutshell, the larger the self-impedance of a cartridge, the more primary inductance will be required from the transformer in order to keep the same low-frequency extension or phase response.
Conversely, if the cartridge has small self-impedance, less primary inductance will be needed for sufficient low-frequency extension or phase response.
Although the target frequency for "f" in the formula above could conceivably be set to the lowest frequency expected to be reproduced, adding good phase linearity to the list of goals will require a considerably lower target frequency.
It should be possible to obtain primary inductance data from any company that winds its own transformers; Sowter, Ypsilon, Lundahl, Jensen, Cinemag, Intact Audio, Hashimoto etc. And even when the manufacturer does not wind the transformer units itself, they should be able to obtain the primary inductance data from their transformer supplier, or measure the value directly by placing an inductance meter across the au naturale transformer unit.
Caveat: although good low-frequency performance from a transformer requires sufficient primary inductance, since high inductance (in the form of more turns, or more wire length per turn, or higher-permeability core materials) tends to cause obstacles for high-frequency performance, single-mindedly selecting a transformer with as much primary inductance as possible, isn't recommended either.
Quick summary: When choosing an SUT, be sure that the gain is appropriate for the output level your phono cartridge.
Also be sure that the SUT's primary inductance is suitable for the coil impedance of your cartridge.
When connecting a SUT and phono stage together, try to choose as low-capacitance cable as possible, using as short lengths as possible, even if doing so means increased length of cable from tonearm to SUT.
Pairing SUTs with low-impedance cartridges results in increased bandwidth and will generally deliver better results than using higher-impedance cartridges.
hth, jonathan
It is sometimes said that an SUT should be matched to the cartridge (or the other way around).
The reason typically given is the need to have an appropriate amount of SUT gain to bring the cartridge's output up to a level that is comfortable for the chosen phono stage.
However, there is another less-known but equally important reason, which is that the low frequency bandwidth and phase response of the SUT depend on both the inductance of the SUT's primary windings, and the net impedance that the primary windings will see, according to the following formula:
f = Z/(2*Pi*L)
where f is the frequency where the amplitude is 3dB down compared to higher frequencies,
L (in henries) is the inductance of the SUT's primary windings
Z (in ohms) is the net impedance
The inductance of the SUT's primary windings should be measured with the secondary windings left open. (Note that a completed SUT may contain internal load resistors across the secondary windings, therefore it is risky to assume that simply because the SUT is not connected to a phono stage, the secondary windings are truly open.)
"Net impedance" in this particular situation means the phono cartridge's source (self) impedance, in parallel with the impedance that is reflected back from the SUT's secondary windings (when connected to a suitable phono stage). Usually the net impedance will be dominated by the cartridge's source impedance.
The mathematical formula tells us that in order to improve the low-frequency capabilities our options are to lower the source impedance (choose a cartridge with less self-impedance), increase the primary inductance of the SUT (increase the number of transformer windings, increase the dimensions of the transformer core, or use a higher-permeability material for the transformer core).}
In a nutshell, the larger the self-impedance of a cartridge, the more primary inductance will be required from the transformer in order to keep the same low-frequency extension or phase response.
Conversely, if the cartridge has small self-impedance, less primary inductance will be needed for sufficient low-frequency extension or phase response.
Although the target frequency for "f" in the formula above could conceivably be set to the lowest frequency expected to be reproduced, adding good phase linearity to the list of goals will require a considerably lower target frequency.
It should be possible to obtain primary inductance data from any company that winds its own transformers; Sowter, Ypsilon, Lundahl, Jensen, Cinemag, Intact Audio, Hashimoto etc. And even when the manufacturer does not wind the transformer units itself, they should be able to obtain the primary inductance data from their transformer supplier, or measure the value directly by placing an inductance meter across the au naturale transformer unit.
Caveat: although good low-frequency performance from a transformer requires sufficient primary inductance, since high inductance (in the form of more turns, or more wire length per turn, or higher-permeability core materials) tends to cause obstacles for high-frequency performance, single-mindedly selecting a transformer with as much primary inductance as possible, isn't recommended either.
Quick summary: When choosing an SUT, be sure that the gain is appropriate for the output level your phono cartridge.
Also be sure that the SUT's primary inductance is suitable for the coil impedance of your cartridge.
When connecting a SUT and phono stage together, try to choose as low-capacitance cable as possible, using as short lengths as possible, even if doing so means increased length of cable from tonearm to SUT.
Pairing SUTs with low-impedance cartridges results in increased bandwidth and will generally deliver better results than using higher-impedance cartridges.
hth, jonathan
Jonathan,
Thank you for the time taken to detail this.
As a general guide what is considered a low impedance value for an MC ?
Much appreciated Rob
Thank you for the time taken to detail this.
As a general guide what is considered a low impedance value for an MC ?
Much appreciated Rob
In case of Lundahl (which I use myself as MC step-up transformer) they specify the stray inductance but not the main field inductance. We can assume their line of MC SUTs is suitable for cartridges with up to 100 ohms impedance. I use a pair of LL1678 in 1:16 connection with a Denon DL-103 having 40 ohms impedance, and they are a good match.
Choose the cartridge that you would like to use and see what other folks have used successfully for a matching SUT is always an easy option. I use a Denon DL-103 so I picked up a used Denon AU-320 and it works fantastic. Figured Denon built both cartridges and SUT's so they should know what works best. Compare the specs like bandwidth to other SUT and you can see just how good the Denon really is.
BillWojo
BillWojo
Doing a bit more digging to see what carts folk like with the slightly unusual arm then hope to try that approach also.👍
Ok, I ordered a AT33SA
Also ordered a set of Partridge 973a transformers
and the bits i need to case mount with a switch for earthing.
So if I got this about right.
Cart is 10ohms and 0.4mv
SUT 1.16
Change my phono amp load resistors from
The 75k I am current running to 33k and that should be
Good?
Also ordered a set of Partridge 973a transformers
and the bits i need to case mount with a switch for earthing.
So if I got this about right.
Cart is 10ohms and 0.4mv
SUT 1.16
Change my phono amp load resistors from
The 75k I am current running to 33k and that should be
Good?
I know one of the Quadratic guys, so I'm not unbiased on this topic. Maybe worth reading a review though: The Quadratic MC-1 Step Up Transformer - Cartridge Dude