alisomay said:
I am wondering also, fortunately i will try soon i guess.
What do you plan to build??
You probably know that OEP are now owned by the Carnhill Group. Not sure what that means for OEP.
Anyway, as a rule you gets what you pays for. Most transformer manufacturers are rather vague about their sepcs. The bass response depends on your source impedance and the inductance of the primary winding. Top end depends on leakage inductance and inter-winding capacitance. Distortion depends on core size and core material as others have already mentioned.
If you compare the size of many OEP input transformers with those from Carnhill, Jensen, Cinemag and Sowter of the same type, you will find the OEP ones tend to be smaller. If you compare the primary inductance of these transformers you will find it is also lower. SO they often have smaller cores and fewer turns both of which save money but bass response and distortion will suffer.
However, OEP do have some good transformers. I have recently been comparing several different 10K:10K transformers of theirs in an attempt to find a lower cost good quality line input transformer.. To give OEP their due, I asked them for specific parameters of these transformers and they have been able to provide most of them. They have offered to measure any that are missing.
The transformers I am looking at are:
A187A13C which costs £25
K30A06C which costs £40
Z21807C which costs £15?? (£24)
Z3002E which costs £27 (£39.50)
The Z21807C price is from Canford. When I asked OEP for a price they said it was £24 for 10 or more. I told OEP about Canford having three in stock at £15 and they recommended I buy them all quickly so I did. All the transformers have mu metal screens except the Z2003E but you can buy a mu metal screening can for it for £12.50 which makes its comparable price £39.50.
I have attached the table of additional data supplied to me by OEP which shows the core material, primary inductance, maximum operating level and low frequency high level distortion. As you will see, the best ones are the K30A06C and the Z3002E both of which cost about£40 and they also have cores that are much larger than the other two.
Cheers
Ian