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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 21 Sep 2018, 22:13 
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Comments back from Dave the music amp tech were that the amp sounds fine, 300b biasing could be improved, heater voltages were ok, and safe to use and connect up.

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PostPosted: 22 Sep 2018, 03:47 
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Hi, carefully put in the tubes and connected some satellite speakers and the iphone. decides to play fleetwood mac “dreams” as the first song and voila beautiful music is flowing at last. it’s early days and my speakers have a limited range but i can’t get over how good it sounds. i haven’t chased or heard any hum yet. hope to settle in for some listening tonight.

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PostPosted: 22 Sep 2018, 03:53 
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First listen


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PostPosted: 23 Sep 2018, 21:56 
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I don't hear any hum or hiss from the little speakers (b & w m1) but when I swapped out the 6sn7 gtb for the taller 6h8c there was a low frequency hum in the left channel. I'll try and return those and get a backup set of 6sn7 s. there is a bit of a hum like noise from the chassis but this is not detectable from more than half a metre away.

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PostPosted: 23 Sep 2018, 22:08 
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Barring any emerging problems I might call this thread a wrap and the admin can consign it to the archives if of any use for posterity. Apart from enjoying the music I am thinking about a 6as7 amp fronted by a 6sn7 4S preamp if that is possible. By all reports of @markhouston and @thehoj the 6as7 is a nice sounding amplifier and the valves are more reasonably priced compared to the 300b s. @suncalc has raised the possibility with a few tweaks of a merger of these two projects so looking forward to that.

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PostPosted: 25 Sep 2018, 21:59 
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Hi John, the amp looks great. Congrats. You really need to try the SE 300B with a pair of higher sensitivity (>92dB) speakers to get the most out of the amp. The m1 are only 85dB. With higher sensitivity drivers any hiss and hum will be more evident.

6as7 is even lower power and will require high sensitivity speakers. What speakers do you plan to use the tube amps to drive?

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PostPosted: 26 Sep 2018, 02:28 
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Thanks Gio. I am detecting hum in both channels at about half a metre. Not too loud though. So I have some more work to do. I have connected up the b&w 706 s2 from memory now. They are about the same efficiency as the m1. They both seem mighty loud in the room that I have but agree higher efficiency is needed. I like the idea of building a set of 6.5 inch fostex horns but haven't listened to them to see if I like them. I will do some research first.

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PostPosted: 26 Sep 2018, 04:37 
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And thanks again Gio for for help and advice.

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PostPosted: 01 Oct 2018, 20:51 
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No problem. I have a pair of the 8 inch fostex in backhorn enclosures. They match very well with low power SE tube amps. The 6.5 inch would also work well.

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PostPosted: 03 Oct 2018, 17:32 
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I see you built some AudioNirvana driven speakers too. How do they compare?

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