OT impedence tolerences

[txbluesboy]

Does anyone check the impedence of new transformers against the factory specs? I have access through my day job to a high dollar transformer turn to turn measuring device. I just bought a Dynaco A-470 of the internet (new) and wanted to see how it measured. On the 4 ohm tap I got a turns ratio of 32.640 which in my calculations works out to be 4261 ohms primary impedence, at the 8 ohm tap I got aTTR of 24.389 which is 4758 ohms on the primary, at the 16 ohm tap I got a TTR of 16.319 which woul be 4260 ohms at the primary. Is this acceptable/normal tolerence? I think the amp would sound a lot different on the 8 ohm tap than it would on the 4 or 16 ohm tap. I can't decide whether to send it back or just use this information when trying different speaker vs tone combinations. I then checked my Heyboer TW 5200 OT, it measured at 6700 ohms within 7% at each tap, its suposed to be 5200 ohms. Whats up????? Terry

[Andy Le Blanc]

I often find that the published rateings are off a bit...... it varies with testing methods
core losses..... frequency..... etc.....
keep in mind that its a dynamic impeadance and not a static resistance...
variations can be compensated for with an eye toward loading and feedback
it is nice to have strict tolerances but its not rocket science
the place I think it will really matter is if its a hi-fi application where a strong
emphasis on the resulting distortion figures may force your choices