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Post by bluegrassdan on Aug 7, 2017 21:47:54 GMT -6
Digging a bit deeper tonight... I don't have an example to show, but without the resistor there were all sorts of ringing anomalies throughout the sweep. It seems clear, as Doug pointed out, that the resistor is helpful in stabilizing the input transformer. So, here are the frequency responses of the current prototype. The first photo shows the reference signal compared to the right and left channels of the preamp. The second photo shows the low shelf RC networks in action. I plan to adjust the medium shelf a bit lower. (Or maybe I won't. Need to play around with various instruments.) The graph can be visually deceiving, as the maximum cut is only 5.5 dB at 50Hz. Thoughts?
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Post by bluegrassdan on Aug 6, 2017 23:39:32 GMT -6
Bluegrass is a medium gauge world.
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Post by bluegrassdan on Aug 6, 2017 12:23:27 GMT -6
My recording colleague notices pronounced energy in the 3k neighborhood with the resistor in place. This is subdued with the resistor removed.
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Post by bluegrassdan on Aug 6, 2017 12:11:17 GMT -6
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Post by bluegrassdan on Aug 2, 2017 13:51:23 GMT -6
Thanks for the input. I'm trying to learn as much as I can about all this stuff. Seems like it may take many lifetimes to accumulate the knowledge that many of you guys have.
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Post by bluegrassdan on Aug 2, 2017 8:35:02 GMT -6
Here's a little video I did demonstrating the effect on ribbon mics when removing the input transformer secondary resistor. RCA specified for their tube preamps not to have a secondary resistor, and rather for the signal to go straight to the first tube grid. My limited understanding is this is common on nearly all of the tube preamps of yesteryear.
I'm curious to get input from those of you who are more knowledgable on the subject.
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Post by bluegrassdan on Aug 1, 2017 11:12:06 GMT -6
Most 47-style mics have pretty high output. Sounds like something ain't right.
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Post by bluegrassdan on Jul 13, 2017 10:20:25 GMT -6
Point taken. Thanks so much for the input, Svart!
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Post by bluegrassdan on Jul 12, 2017 7:28:31 GMT -6
All this expertise that we notice and care about and 99% of the audio people just say digital modeling is close enough bahaw... I'll put my hand-built LA2A up against the UA plugin any day of the week.
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Post by bluegrassdan on Jul 12, 2017 1:02:37 GMT -6
Hi Svart,
These photos were more of hype to put on Facebook for some of my engineer friends. To be honest, I'm quite a newb at building gear, although I have been playing music professionally for 30 years.
To cut to the chase, our studio has owned this ADL 600 for several years and my colleagues and I never have liked it. It's harsh in the top end, mushy in the lows, and it never made sense to us what was going on with it. Tube swapping didn't really help much. It's odd because the designers are reputable guys, but the preamp just doesn't sound so great - for whatever reason.
I only recently have been getting into learning the oscilloscope, and I need to learn much more about how to properly measure specific devices. I attempted to measure from the same points in the circuits with the same settings. Measurement leads were calibrated, although I did break a cord the other day and needed to use an unloaded cable between the function generator and the preamps. I agree that this is the cause of the slight overshoot/ringing.
(I admit again - I don't know a whole lot about the subject and hope to learn more.)
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Post by bluegrassdan on Jul 11, 2017 16:05:02 GMT -6
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Post by bluegrassdan on Jul 2, 2017 14:55:23 GMT -6
Thanks, Chase. Our goal at ETSU is to offer recording curriculum "for musicians," different from what some of the larger recording programs offer. By taking on the role of an engineer or producer, students learn to use the recording studio in ways that support their craft. They are always focused on the music and artistic development while in the studio. After all, microphones, whether great or bad, cheap or expensive, just sit there and dare you to play something into them.
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Post by bluegrassdan on Jul 2, 2017 8:40:40 GMT -6
AKG 701
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Post by bluegrassdan on Jun 30, 2017 9:31:49 GMT -6
Thanks for the thoughts so far.
The Thompson has a more immediate response with tighter bass. It's a lot louder too. The Sumi's low end can be a bit mushy, but it has more sparkle.
I can't wait until the Thompson gets a few years on it!
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Post by bluegrassdan on Jun 29, 2017 22:46:50 GMT -6
Just watch the video. You'll know what to do!
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Post by bluegrassdan on Jun 5, 2017 0:04:56 GMT -6
Nice looking preamp! I bet that sounds huge with that combination of transformers.
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Post by bluegrassdan on May 29, 2017 16:25:19 GMT -6
There's no room to move the 1/4" jack down. It's all squeezed in pretty close.
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Post by bluegrassdan on May 28, 2017 23:56:37 GMT -6
We have a pair of M30s that are used for a few purposes. Schnider disk room mics, sometimes on fiddle, and it can work really well wrapped in foam and tucked between the bridge feet of an upright bass.
They're pretty useful if you have a full studio and need diversity. Certainly not a desert island mic. (That would go to my KM84s or Flea 47.)
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Post by bluegrassdan on May 28, 2017 23:43:53 GMT -6
The main reason for not centering is because there is no extra room to move the stepped gain attenuators down. There's a big PIO 2.2uf capacitor in the way. (But I'm gonna stick with the photo framing artistic answer!) Here is the design I finalized with actual RAL colors. Dan Duerloo is working his magic on making it a reality.
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Post by bluegrassdan on May 12, 2017 19:01:42 GMT -6
Would be nice to hear the real Neves through some better converters vs the UA stuff. THEN you would hear an even bigger difference.
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Post by bluegrassdan on May 12, 2017 18:54:48 GMT -6
I highly recommend open back headphones for vocalists. They can monitor lower and hear themselves better. My AKG701s go to every session.
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Post by bluegrassdan on May 12, 2017 18:32:49 GMT -6
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Post by bluegrassdan on May 12, 2017 18:10:09 GMT -6
Invest in a good cue system (we have Aviom). All the best mics and preamps in the world won't matter if the musicians are frustrated with an inadequate headphone system.
That includes decent headphones too. Your singers will sing better, non-fretted instruments will be better in tune, and it will take less time.
(I love great mics and gear, too. But a bad cue will ruin you.)
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Post by bluegrassdan on Apr 27, 2017 11:10:54 GMT -6
Gotta start with a good singer who can work a mic and enunciate. Also, you would need a dynamic and thoughtful band to stay clear of the subtle vocal nuances.
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Post by bluegrassdan on Apr 18, 2017 22:41:56 GMT -6
Had to make some changes. Which version is better now? The one with "Gain" or without? Attachments:
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