Vintage Saba opt in SE-headphone amp

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After having finished a very good sounding Aikido with parafeed output transformers I wanted to try a true SE headphone amp with output transformers. I breadboarded the amplifier and am currently using E810F wired as triode with LED bias (orange ones at around 21mA/1.9Vish) and fully regulated supplies.
As output transformers I was given a nice pair of Saba opt's out of the old famous radios (dunno which tube compliment). Those have three taps with two of them making a nice 6K:300R output transformer. I was able to confirm this by using a small 6V print transformer and measuring the respective voltages.

Q: Since the transformers don't have any markings of the taps I keep wondering how to correctly hook up the wires... I just hooked it up and it plays music nicely :p , but does it matter which way around I hook things up and how prim. and sec. are hooked up in respect to each other? Hope I could make myself clear enough in terms of language...:ashamed:

Please see attached image -->


Edit. Tubes in picture of course are not E810F! To test things I didn't want to run the risk of toasting the "precious" pentodes but used "cheap" 6N6P instead (wired correctly ;-))...
 

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Thank you Blade!

My Sennheiser headphones are 300 ohm which is why I was trying the Saba opt's. To be honest I don't now how sensititive a headphone amplifier is in terms of correct load of the plate... but I tried to achieve something like a 6K load.
I might also try the 6N6P's...only issue I am having here is that my regulated heater supply needs way more heatsinking to supply the needed 1500mA :)
 
HF performance will be different because Fres of the OT will be lower when the primary is reversed. I noticed it the other day with an amorphous core. Although it happens at a supersonic frequency, the effect on the audio band can be heard. Don't know if the effects will be noticable when the OT has more / stronger shortcomings.
 
HF performance will be different because Fres of the OT will be lower when the primary is reversed. I noticed it the other day with an amorphous core. Although it happens at a supersonic frequency, the effect on the audio band can be heard. Don't know if the effects will be noticable when the OT has more / stronger shortcomings.

This is true of the toroidal transformers I have used, but you want the orientation which produces the more rolled off frequency at the top end. This is because the rising response is due to a resonance between the leakage inductance and capacitance and with all the toroidals I have used usually peaks at about 60khz. Over time this makes for very fatiguing listening. Peaking can be as much as 6db. I also found that if the transformer was ringing - it also distorted the lowest frequencies the transformer could produce.

Shoog
 
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