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TRACE ELLIOT BLX-80:- minimum speaker load?

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46 minutes ago, Chienmortbb said:

I asked Celestion and this was their reply

"I don't have the specifications to hand, I'm afraid. But I can tell you that the modern day TF1020 would be very close to this model."

https://www.lean-business.co.uk/eshop/celestion-tf-1020-8ohm-10-pa-speaker-p-112.html?zenid=c6qbfblsnadkqcftj8lth660c0

Yes, that's the 'like for like' replacement i.e. same 8 ohm and 150 watts as the originals.

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The AH-100 links are for manufacturing to use this PCB assy. with a different model.

 

This amp, from the photo, uses a single pair of output MOSFETS. Depending on the power supply (rail) voltages, it may very well be rated for 8 ohms minimum load only. Especially because it has a single speaker jack in what was a combo, and because Celestion confirmed that it was an 8 ohm driver.

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1 hour ago, agedhorse said:

The AH-100 links are for manufacturing to use this PCB assy. with a different model.

 

This amp, from the photo, uses a single pair of output MOSFETS. Depending on the power supply (rail) voltages, it may very well be rated for 8 ohms minimum load only. Especially because it has a single speaker jack in what was a combo, and because Celestion confirmed that it was an 8 ohm driver.

Yes I had the BLX130 and it had two mosfets and spaces for two more plus a few resistors. That suggested to me  that the PCB was used for 130W upwards. Of course the speaker was 8  ohms so it was still 80 watts without an extension cab.

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On 03/10/2019 at 09:06, Chienmortbb said:

Yes I had the BLX130 and it had two mosfets and spaces for two more plus a few resistors. That suggested to me  that the PCB was used for 130W upwards. Of course the speaker was 8  ohms so it was still 80 watts without an extension cab.

With all 4 MOSFETs, it was capable of greater power into both 8 ohm and 4 ohm loads. There were many versions of these amps that used a similar output section, but it depends on the power transformer (thus the rail voltage) also. If the rail voltage gets too high (to achieve greater power into 8 ohms), then 4 output transistors may not be enough for the resulting higher power into 4 ohms. There were also different MOSFETS used throughout the production history, including special "double-die" parts. 

 

Over the years, there were some output stage applications that weren't all that reliable, and sometimes incorrect transformers were fitted in order to ship amps. Many of these unrelaiblities could be traced back to the liberal build philosophy rather than the circuits themselves. 

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