Resistance check after SUT install

[Chris H]

Finally receieved Sowter 1990s this week and installed in my Eros.
Everything has been working fine, albeit requiring huge gain on my LOMC cart.
All resistances check out except to left and right input centre pins where reading is now 2.5 ohms on both (47.5k expected)
I figured this might be something to do with the SUT so took a reading at 2 and 17 which would be the 'new' input after the transformer.

Readings are 1.267k and 1.272k.
This is precisely the reading if I measure across the 47.5k loading resistor.

The two sets of readings (2.5 and 1.3k) correspond to the resistance of the primary and seconday in the SUT (2.5 and 1500 approx is spec).

I wanted to check whether this is expected or if I have done something wrong before powering up and proceeding to voltage checks.
Picture of one channel attached.  Other channel is exactly the same, and has same readings, so any issue I will assume has been replicated.

I am also now left wondering whether I have the correct loading resistor (0.35mV Rega Apheta, 10ohm internal).

Any advice, corrections, explanation much appreciated.

[Paul Joppa]

This is as expected.

The loading impedance is 47K divided by the turns ratio squared, i.e. 470 ohms at 10:1, or 117.5 ohms at 20:1.

[Chris H]

Many thanks Paul.
And thank you for confirming impedance.  I had calculated 117.5 (recommended 100 for that cartridge) but was unsure if the 1.3k in the SUT was a factor.
On with voltage checks and, all being well, some listening.

Kind Regards
Chris

[Larpy]

I'm glad PJ answered your question, because I have no advice but a question for you.  Did you order you 1990s directly from Sowter?  If so, when did you place your order?  I have a pair on order and it's been 3 months now: i understand that COVID has messed with their delivery times but I don't know by how much. 

Looking forward to reading your impressions of how the Eros sounds with the Sowters.  Even without them, my Eros sounds really good, and I have a LOMC also: .28mV.

[Paul Birkeland]

I ordered a pair at the end of August and they showed up last week.

[Larpy]

Looks like I'll need to be patient and wait another 2 months.

[Chris H]

Hi Larry,

It may depend where you are.  I am in UK so shipping within UK.
I ordered 13th October.  They emailed same day to say lead time is 12 weeks (15th Jan I think I expected).
I spoke with them earlier this month just to check on status and they said they had been having staffing issues at the same time as being very busy.
They are working to clear a backlog and have taken on 3 extra staff so expect the delay to reduce as they get through back orders and I can expect my order this month.
Came on Wednesday so not much longer than their original 12 week estimate.

All voltage checks complete and everything checks out. 
I too have been using without SUTs and already liked what I heard so I am looking forward to listening now it is complete.  I will report back with impressions.

Just in time too.  Received notification today that my S.E.X. has arrived at my local post office.