I have a few lm1875 chips in my drawer for quite some time, and would like to make a simple p2p amp. The power supply needs to be dual, if I want it to sound okay, and I just saw I have some EI transformers at work that could possibly be okay.
https://www.botter.com/pdf/Trasformatori TB Line omologati UL-CSA Insulation System.pdf
This is the link to the technical data. I have TBTMS01024 and I can get them for fairly cheap.
Is this 12-0-12 the correct configuration?
https://www.botter.com/pdf/Trasformatori TB Line omologati UL-CSA Insulation System.pdf
This is the link to the technical data. I have TBTMS01024 and I can get them for fairly cheap.
Is this 12-0-12 the correct configuration?
You can use a 12-0-12 Vac transformer (the TBTMS01024) for the LM1875. When you rectify 12-0-12 Vac, you get some +/-16-17 Vdc in idle mode. That will not use the LM1875 to its full capacity. But, LM1875 anyway is difficult with self-oscillations for supply voltages above 25V (+/-).
Supply voltages of 20-22V (+/-) is better.
The E/I type transformer will do well. With a good size transformer core, the leakage field will be little and you will hardly experience differences how you turn the transformer.
Toroidal transformers are known to have less magnetic leakage field.
Supply voltages of 20-22V (+/-) is better.
The E/I type transformer will do well. With a good size transformer core, the leakage field will be little and you will hardly experience differences how you turn the transformer.
Toroidal transformers are known to have less magnetic leakage field.
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NO!
24-0-24 Vac will leave you with some +/-33-34V when rectified and with little load. The LM1875 can max. take +/- 30V and then you may even have high frequency instability.
What would be better is a 15-0-15 Vac or 16-0-16 Vac transformer. The "01048" is simply too much.
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I assume "0-230-400" means the transformer can be used with either a single phase system (including a null conductor) or operated from two phases of a three phase system.
If you put 230V on the "0-400" winding you get a reduced output voltage at the secondary windings. The reduction factor is 230/400.
The "I measure 15VAC across -12/+12" I don't understand?
If you put 230V on the "0-400" winding you get a reduced output voltage at the secondary windings. The reduction factor is 230/400.
The "I measure 15VAC across -12/+12" I don't understand?
These are "control transformers".
You have a big system (heating, air conditioning, factory motors) run on 240V or 400V. Such a system may also have control circuits: thermostats, timers, cut-offs.
240/400V wiring needs extra insulation and protection against the high available power. The control systems may all be low power, just controlling relays which do the heavy work. These are traditionally wired with 24V power, through a "small" transformer. Shock and fire risk is low.
Most US homes have a 24V 40VA transformer for the furnace and A/C. The thermostat makes/breaks the 24V. Relays downstairs make/break the 120V or 240V to furnace blowers, A/C compressor, electric heating.
While the plain 120V:24V 40VA transformer is sold by the millions for domestic HVAC controls, larger systems may need more power, different secondary voltages, or may have only higher line voltage handy.
That series of transformers takes either of the two main EU line voltages (230 400) and delivers the secondary voltages listed.
Yes, if you feed 230V to the 400V winding you get (as FF says) 230/400 or 57% of the indicated voltage. So "12V+12V" (24V) now gives 13.8V (or a bit more measured no-load). The "problem" is that a 100VA rated transformer now can only deliver about 100VA*(230/400) or 57VA. You are paying 74% more than you need to.
OTOH, those control transformers are sold in large quantity and thus much less expensive than most other types. And at an extreme, sometimes you find a pile of salvaged transformers at a furnace repair shop cheap or free.
Also under-feeding the nominal ratings may be less stray flux off the transformer.
2*24VAC, but with 230V on the "400V" winding, may be an OK choice. It gets you +/-20V DC, which is enough to get good sound from LM1875, without being close to blow-up.
You have a big system (heating, air conditioning, factory motors) run on 240V or 400V. Such a system may also have control circuits: thermostats, timers, cut-offs.
240/400V wiring needs extra insulation and protection against the high available power. The control systems may all be low power, just controlling relays which do the heavy work. These are traditionally wired with 24V power, through a "small" transformer. Shock and fire risk is low.
Most US homes have a 24V 40VA transformer for the furnace and A/C. The thermostat makes/breaks the 24V. Relays downstairs make/break the 120V or 240V to furnace blowers, A/C compressor, electric heating.
While the plain 120V:24V 40VA transformer is sold by the millions for domestic HVAC controls, larger systems may need more power, different secondary voltages, or may have only higher line voltage handy.
That series of transformers takes either of the two main EU line voltages (230 400) and delivers the secondary voltages listed.
Yes, if you feed 230V to the 400V winding you get (as FF says) 230/400 or 57% of the indicated voltage. So "12V+12V" (24V) now gives 13.8V (or a bit more measured no-load). The "problem" is that a 100VA rated transformer now can only deliver about 100VA*(230/400) or 57VA. You are paying 74% more than you need to.
OTOH, those control transformers are sold in large quantity and thus much less expensive than most other types. And at an extreme, sometimes you find a pile of salvaged transformers at a furnace repair shop cheap or free.
Also under-feeding the nominal ratings may be less stray flux off the transformer.
2*24VAC, but with 230V on the "400V" winding, may be an OK choice. It gets you +/-20V DC, which is enough to get good sound from LM1875, without being close to blow-up.
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