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Old 18th March 2009, 12:20 PM   #1501
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Default Ot

Quote:
Originally posted by bvan
hyperacusis in one ear
HI bvan,same unlucky but my analog stuff and fullrange solved this problem, probabily I have all dinamic that I need, at low pressure

If I remenber well, John Curl speaks about one AES study found that digital music can do problem ....
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Old 18th March 2009, 12:33 PM   #1502
bvan is offline bvan  Denmark
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The First Watt does look promising on paper. Thanks for that.

Interesting what you say about hyperacusis and vinyl. I'm having a GTG at my place on the weekend and might for the first time ever get to hear vinyl playing in my home A bit worried to find out what I might have been missing (and what I cant yet afford)
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Old 18th March 2009, 04:13 PM   #1503
bvan is offline bvan  Denmark
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Just wondering about the current-source First Watt amps, seems from the FR graphs to bring down the mid-treble region, which is a useful flattening out of most fullragers. But if the fullranger were to be flattish to begin with, could this cause an unwanted roll off towards the top?
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Old 18th March 2009, 09:12 PM   #1504
kmaier is offline kmaier  United States
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Default 16 ohm taps

Just in case a few folks forgot....

OPTs simply reflect the load from one winding to the other. If you have an OPT with a 5K primary impedance and an 8 ohm secondary, loading the secondary with an 8 ohm load results in a 5K primary impedance. Drop the secondary load to 4 ohms and the primary drops to ~2.5K, raise the secondary load to 16 ohms and the primary increases to ~10K.

As a result, not having the proper matching of load to OPT can offset the loading by a large amount and alter the operating specs of the amp by a fair amount. Having a 20 ohm secondary will result in a "lower than rated" primary impedance with the Feastrex drivers (and vary somewhat as the actual impedance of the Feastrex driver does versus frequency). You can also get much less power in a tube amp when the matching is off and distortion can suffer quite a bit.

For what little it's worth, I've done extensive testing with the 45 and 2A3 (over 100 samples). My preferred loads for these are 5K and 3.5K respectively. With good driver circuitry and proper operating voltage/bias, I generally get 2.25-watts from the 45 and 4.5-watts from the 2A3 with very low distortion and very good linearity.

Regards, KM

PS - the EL84 is not specifically a guitar amp tube... nor are any others that I'm aware of... they're popular of course.... as are 6L6GCs in guitar amps.
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Old 18th March 2009, 09:39 PM   #1505
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Default Re: 16 ohm taps

Quote:
Originally posted by kmaier
For what little it's worth, I've done extensive testing with the 45 and 2A3 (over 100 samples). My preferred loads for these are 5K and 3.5K respectively. With good driver circuitry and proper operating voltage/bias, I generally get 2.25-watts from the 45 and 4.5-watts from the 2A3 with very low distortion and very good linearity.
OT - I really appreciate your sharing of knowledge and experience on the various forums. I'd like to know more about your testing, chosen operating points, and preferred sonics. If you have the time and inclination, would it be possible to start a thread in Tubes or PM me? Thank you.

Now, back to regular programming.
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Old 18th March 2009, 09:56 PM   #1506
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Quote:
Originally posted by bvan
The First Watt does look promising on paper. Thanks for that.

Interesting what you say about hyperacusis and vinyl. I'm having a GTG at my place on the weekend and might for the first time ever get to hear vinyl playing in my home A bit worried to find out what I might have been missing (and what I cant yet afford)
Until you've heard The Monkies on vinyl you haven't lived.
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Old 20th March 2009, 11:35 AM   #1507
bvan is offline bvan  Denmark
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Anyone got a FR graph of D5nf they could send me?

Cheer
B
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Old 20th March 2009, 01:27 PM   #1508
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I have to admit, I'd be intrigued to see one myself. As Feastrex don't appear to measure the electrical / mechanical parameters of their drivers however, one assumes that they don't take an FR curve either. Exactly what one is supposed to make of that, I don't know. I can think of five possible reasons, but which is / are correct is open to question.
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Old 20th March 2009, 01:45 PM   #1509
bvan is offline bvan  Denmark
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Yeah, I'm hoping someone has taken some at home, pref out in the garden.

They sound flat enough to my ear, but I'm about to try digitally high pass them with a DEQ2496 (upstream of my dac) so I figured I might try correcting whatever irregularities the driver might have and see if its an improvement.

(if the above sounds like an impossible setup it's not too far off - plan is to high pass the entire signal, 80hz 2nd order, and from the DEQ feed SPDIF to dac to SET amp to D5nf, and at the same time from DEQ to DCX to SS amp to subs. In the DCX I'll dial back the missing bass with a 24db bump at 20hz. Volume control via DEQ. I'm guessing there could be some loss of low freq resolution by attenuating in the digital realm, and maybe excessive phase shift. It seems a better bet than using only the DCX and its inbuild dacs, or using passive components, or running D5nf unfiltered in OB. We'll see...)
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Old 20th March 2009, 01:52 PM   #1510
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Quote:
Originally posted by Scottmoose
. . . Feastrex don't appear to measure the . . . FR curve . . . Exactly what one is supposed to make of that, I don't know. I can think of five possible reasons, but which is / are correct is open to question.
If it's any help, I would venture to say that whichever of those five possible reasons is the most charitable, that's the one that is probably closest to the truth.

-- Chris
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