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| sahko123:
|O ok then, ive started designing a tube amp and I need to know this. is it a good idea to drive higher impedance loads say 64 ohms for a set of headphones with an output impedance of 8 or 16 ohms from an output transformer? ive googled it and I cant find a concise answer would there be big discrepancies in volume/voltage or problems with efficiency? |
| iMo:
https://www.diyaudio.com/forums/tubes-valves/264623-output-transformer-impedance-matching.html |
| T3sl4co1l:
Impedance matching doesn't mean much when you need mW from a multiple-W amplifier. ;) More important will be output voltage stability and frequency response, which often depends on load impedance. Tim |
| spec:
--- Quote from: sahko123 on November 03, 2018, 05:13:51 pm --- |O ok then, ive started designing a tube amp and I need to know this. is it a good idea to drive higher impedance loads say 64 ohms for a set of headphones with an output impedance of 8 or 16 ohms from an output transformer? i've googled it and I cant find a concise answer would there be big discrepancies in volume/voltage or problems with efficiency? --- End quote --- You would probably get away with it, but there is a danger of damaging the output transformer insulation. Best not to take a chance and fit a resistor, equal to the specified output impedance, across one of the transformer outputs. Then connect your phones across any of the outputs (16 Ohm output will be louder). Take it easy on the volume and check if the phones are excessively loud. If so, you would need to fit an attenuator for the phones to protect the phones and your ears. A 20W or higher power resistor should have enough power handling capacity for amps up to 50W. There are a few valve addicts on EEV so don't be shy about posting details of your amp build ::) |
| sahko123:
Thanks for the multiple responses I was thinking would be able to put a resistive load in parallel or series with the headphones so the transformer sees the desired resistance or does the impedance of the headphones vary enough through the frequency ranges that this would be a bad idea? I want to know as much as possible before putting any thing together and blowing something. for those who want to know the headphones are 55ohm Akg K240's and the tubes are 6550s with preamp tubes to be decided. |
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