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Old 27th March 2010, 07:38 PM   #3131
udailey is offline udailey  United States
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I have built several of BrianGT's LM3886 boards. I love them. So simple so cheap so nice to listen to. I especially like to use his Mini A power supply with the chipamp boards.
The MyRef does blow it away. I used the B1 with the MyRef and I also used my Lightspeed with the MyRef. Both were good, using the Lightspeed is incredible.
This is a Howland Current Pump. Its been almost exactly a year since I listened to the MyRef. I broke it in our move to Texas. Will be building it again in less than a month. I have had the BrianGT going since the MyRef broke so I will be able to directly compare. cant wait to build it again. It really is the top of the line using LM3886.
That Howland Current Pump is the big difference.
Uriah
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Old 27th March 2010, 08:01 PM   #3132
troystg is offline troystg  United States
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What he said.. :-)
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Old 30th March 2010, 08:22 AM   #3133
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I will be feeding my MyRef_C with a Salas DCB1 and aLightspeed attenuator. The DCB1 is amongst the best pre's that exist now. Is active but has no gain, so it acts as a buffer, matching impedances to avoid frecuency rolloffs.
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Old 1st April 2010, 01:56 AM   #3134
matt09 is offline matt09  United Kingdom
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How many volts rms in does my ref need for full output?

thanks
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Old 1st April 2010, 02:12 AM   #3135
udailey is offline udailey  United States
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Around 35 max.
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Old 1st April 2010, 08:20 AM   #3136
UnixMan is offline UnixMan  Europe
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Uh? +-35Vdc is about the supply rails... the actual max output voltage is somewhere around 60Vpp. But regiregi22 asked about input voltage for max output, that is sensibility.

Gain is about 30dB, less than 1Vrms input is enough for full power. Thus, with modern sources the my_ref does not really need any extra gain. But it likes a lot (almost "requires" to) being driven by a low and constant impedance, so for best performance a low output-Z active preamp or buffer is highly recommended.
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Old 1st April 2010, 10:25 AM   #3137
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Quote:
Originally Posted by UnixMan View Post
Uh? +-35Vdc is about the supply rails... the actual max output voltage is somewhere around 60Vpp. But regiregi22 asked about input voltage for max output, that is sensibility.

Gain is about 30dB, less than 1Vrms input is enough for full power. Thus, with modern sources the my_ref does not really need any extra gain. But it likes a lot (almost "requires" to) being driven by a low and constant impedance, so for best performance a low output-Z active preamp or buffer is highly recommended.
In fact, I didn't, It was Matt
BTW, I have read in this thread that gain is not 30dB, it it 30x. 1v in gives you 30v out. Correct me if I am wrong, please.

Your full output voltage will be defined by the clipping point of the amplifier with a given load. You will have different clipping points depending if using 4 or 8 Ohm, so sensibility will be different.
To measure, you have to attach a high wattage load resistor, and looking at the scope, you up the input voltage until the voltage out clips. That's your sensibility input voltage.
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Old 1st April 2010, 12:43 PM   #3138
UnixMan is offline UnixMan  Europe
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The gain is about 30dB. Incidentally, 20 * Log(30) ~= 30 dB

And 1 Vrms ~= 2.82 Vpp x 30 = 84.6 Vpp out, much more than what the my_ref can do.

Current limit is (obviously) defined by the LM3886 capabilities. National claim that's over 10A (11.5A, if I remember correctly). So +-10A * 4ohm = +-40Vp (80 Vpp), again much more than what the my_ref can do.

Though some people think that's an overoptimistic figure and that with +-35Vdc supply the "SpiKE" SOA protection jumps in way before that limit is reached. According to them, something like 5 - 6 amps seems to be a more realistic limit. In such a case, on 4 ohm a (really weird!) current-induced clipping would occur already at 20 - 24 Vp (40 - 48 Vpp).
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Old 1st April 2010, 12:46 PM   #3139
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Thanks for your response Unixman, now I see it clear
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Old 1st April 2010, 03:51 PM   #3140
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Default Blown my original MyRef A

Help needed!

I had the old version connected to neither an input or output. It was connected to power and the relais started to rattle. Afterwards it did not "amplify", the relais did not connect anymore. Probably blown the op-amp LM318 or the power-amp 3886.

Am I right?

How to analyze the fault and then solve this?

Thanks in advance
Michiel
(earsandeyes)
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