Hey
I was up in landfills, where I bought a pair of used speakers in their hand shop.
The speakers are damaged but there was a transformer at each speaker box.
After I have googlet a little I found out it was 100 V types from PRO-signal.
I found a data sheet here: http://www.farnell.com/datasheets/483955.pdf type is PO38A.
How do I measure the primary impedance so I can use them in a little tube amp.
Benny
I was up in landfills, where I bought a pair of used speakers in their hand shop.
The speakers are damaged but there was a transformer at each speaker box.
After I have googlet a little I found out it was 100 V types from PRO-signal.
I found a data sheet here: http://www.farnell.com/datasheets/483955.pdf type is PO38A.
How do I measure the primary impedance so I can use them in a little tube amp.
Benny
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Let's calculate an example based on the specification you linked.
We know that there is constant voltage 100 V at the primary.
If we select the primary taps for 1.25 W and 8 ohms secondary.
We can now calculate the voltage across the secondary.
This is: U = √ P x R, which is √ 1,25 W x 8 ohms = 3,16 V.
Then we can determine the transforming ratio
µ = ( Uin / Uout) = 100 V / 3,16 V = 31,6.
The impedance ratio is µ2 = 1000 and finally the reflected impedance from 8 ohms secondary to 1.25 W primary = 1000 x 8 ohms = 8 kilo ohms.
For 2.5 W primary, the reflected impedance is 4 k and for 5 W primary it is 2 k. etc.
We know that there is constant voltage 100 V at the primary.
If we select the primary taps for 1.25 W and 8 ohms secondary.
We can now calculate the voltage across the secondary.
This is: U = √ P x R, which is √ 1,25 W x 8 ohms = 3,16 V.
Then we can determine the transforming ratio
µ = ( Uin / Uout) = 100 V / 3,16 V = 31,6.
The impedance ratio is µ2 = 1000 and finally the reflected impedance from 8 ohms secondary to 1.25 W primary = 1000 x 8 ohms = 8 kilo ohms.
For 2.5 W primary, the reflected impedance is 4 k and for 5 W primary it is 2 k. etc.
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Put a 16 ohm speaker on them and use a couple of EL86's for around 25W. Or double up the output and 50W into 8 ohms, going to need a 1:1 power transformer with a decent amount of current as the tubes run in the 170-250V range.
http://www.hifitubes.nl/weblog/wp-content/general-electric-6cw5.pdf
http://www.hifitubes.nl/weblog/wp-content/general-electric-6cw5.pdf
Hi
"Using 40 watt as B+ and COM and 10W for plate connections"
I meant: Using "40 watt" tap as B+ and the two taps "COM" and "10Watt" as plate connections. This gives Raa at 1k and the impedance from B+ to "COM" and "10 Watt" are indentical.
Yes I know that they are not designed for use in tube amplifiers, but there are a number of articles showing that they can be used.
See the link in your first post. Unfortunately mine is not as useful as other types.
I have 15-20 used EL86/PL84 tubes. Then I can use a PPP solution to eleminate the low impedance.
Benny
"Using 40 watt as B+ and COM and 10W for plate connections"
I meant: Using "40 watt" tap as B+ and the two taps "COM" and "10Watt" as plate connections. This gives Raa at 1k and the impedance from B+ to "COM" and "10 Watt" are indentical.
Yes I know that they are not designed for use in tube amplifiers, but there are a number of articles showing that they can be used.
See the link in your first post. Unfortunately mine is not as useful as other types.
I have 15-20 used EL86/PL84 tubes. Then I can use a PPP solution to eleminate the low impedance.
Benny
Appologies - I misinterpreted your post and thought you had a 5W tapping.
Philips made many PA amps using 6CM5/EL36 - they have a relatively low PP impedance requirement - which could probably allow 1k PP with B+ and screen around 200-230V, from a quick peruse of the datasheet. I have a restored quad 6CM5 amp, which worked out quite well.
Ciao, Tim
Philips made many PA amps using 6CM5/EL36 - they have a relatively low PP impedance requirement - which could probably allow 1k PP with B+ and screen around 200-230V, from a quick peruse of the datasheet. I have a restored quad 6CM5 amp, which worked out quite well.
Ciao, Tim
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