Low-distortion Audio-range Oscillator - Page 350 - diyAudio
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Old 28th January 2014, 08:08 PM   #3491
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Quote:
Originally Posted by davada View Post
Thanks Dirkwright.

Are these all 19" wide? Do they do smaller enclosures?
No time look at the moment. Just home for lunch break.
Yes, they have a desktop series. We use those for our boxes right now, but we want to start making our own.
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Old 29th January 2014, 05:40 AM   #3492
1audio is online now 1audio  United States
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Default Update on ADC efforts-

I made changes to the EMU 1212 and it got a little better but its still not stable and not near what I can get from the AK5394A. I will abandon that direction and boot the stuff back out eBay, chalking it all up to experience (unless someone wants a modded emu 1212).

Below is what I can get using one of Viktor's oscillators. I get similar from the modded KH4400. Somehow I'm getting better results than AKM has been able to. I need to find a way to make sure what I'm seeing is not some distortion cancellation.

At this level even a small nonlinearity on the input Z creates measurable distortion. Probably affects the oscillators as well.

I'm working on an upgrade board for the Juli@. I have most of the details worked out now. I'll be assembling the schematic shortly. The actual layout may take a while (unless some volunteer with time steps up).
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Old 1st February 2014, 01:06 PM   #3493
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For what it's worth, I was directed to a small company called Ross Martin:
More Ear Gear

They make ADC's, DAC's and other interfaces for not a lot of money. For the ADC they use the PCM4222 and the DAC uses the PCM1794a. I have no relation to their business. I'm only planning getting some of their gear because it's reasonably priced for what you get and I thought I'd share.
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Old 2nd February 2014, 09:45 AM   #3494
hahfran is offline hahfran  Germany
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Quote:
Originally Posted by coluke View Post
I think the answer is definitely... no. The distortion products you see in the spectrum I've posted are mainly (or entirely) due to the peak detector, whose time constant is zero - no filtering at all means very low settling time (which is good), buy the price you have to pay is that all the harmonics produced by the full wave rectifier are injected in the level control loop, i.e. in the output signal. In order to lower the output THD you have to set up an integrating loop - maybe you can try the one from the JLH's original design:
Attachment 263922
it's a Wien Bridge ring-topology (in order to get rid of the opamp common-mode THD), and the amplitude control loop is based on a canonical peak-detector/integrator chain (whose time constant you'll have the to tailor in order to suite your needs - ie freq range and output amplitude).

L.
The desired time constant can be achieved simpler, replace the LED with an incandescent lamp. That requires an additional transistor for driving.
Further I used instead of a rotary switch 5 inexpensive surplus dual reed relays and a simple TTL "logic" 1 of 5 that drives the relay coils and the range
indicator rectangular LEDs. However one should not attempt to save any cost regarding the caps and the dual ganged pot.
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Old 3rd February 2014, 05:29 PM   #3495
RNMarsh is offline RNMarsh  United States
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Will need a brick-wall filter at 20KHz to be applied to remove out of band junk? Like the AES standard?

Thx-RNMarsh
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Old 3rd February 2014, 07:51 PM   #3496
coluke is offline coluke  Italy
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Quote:
Originally Posted by hahfran View Post
The desired time constant can be achieved simpler, replace the LED with an incandescent lamp.
Right - did you measure generator's THD with the lamp based AGC loop?

L.
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Old 18th February 2014, 01:05 AM   #3497
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Quote:
Originally Posted by davada View Post
Thanks Dirkwright.

Are these all 19" wide? Do they do smaller enclosures?
No time look at the moment. Just home for lunch break.
Here:
Par-Metal

I get them without vent holes. I recommend either clear or gold alodine finish, since it's conductive. Alodine is also good primer for paint, if you choose. They also make custom sizes.
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Old 20th February 2014, 06:28 AM   #3498
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Quote:
Originally Posted by RNMarsh View Post
Pls do design one... PLS !! We need one. You'll get plenty of help. Many of us are in the final quarter of the game before the buzzer. Getting down our experience is something important... Now we have the world watching and listening via the WWW/Internet. A once in a life-time opportunity.
:-)

Thx-RNMarsh
Ya know, when I was younger, I always wanted to learn about electronics.

Now, I'm older and trying to learn and have come a long long way; and,
I know too that I'm on the 3 period of the game and appreciate all that
everyone has to offer, I watch, listen, and learn, and hope you don't mind
if I ask a bunch of questions with "obvious" answers...

or

Just enjoy interacting because I appreciate your efforts too.

Sync
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Old 20th February 2014, 01:35 PM   #3499
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Quote:
Originally Posted by 1audio View Post
I made changes to the EMU 1212 and it got a little better but its still not stable and not near what I can get from the AK5394A. I will abandon that direction and boot the stuff back out eBay, chalking it all up to experience (unless someone wants a modded emu 1212).

Below is what I can get using one of Viktor's oscillators. I get similar from the modded KH4400. Somehow I'm getting better results than AKM has been able to. I need to find a way to make sure what I'm seeing is not some distortion cancellation.

At this level even a small nonlinearity on the input Z creates measurable distortion. Probably affects the oscillators as well.

I'm working on an upgrade board for the Juli@. I have most of the details worked out now. I'll be assembling the schematic shortly. The actual layout may take a while (unless some volunteer with time steps up).
The EMU 1212M is NLA apparently. Anything similar that is as good?
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Old 25th February 2014, 05:31 PM   #3500
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by SyncTronX View Post
Ya know, when I was younger, I always wanted to learn about electronics.

Now, I'm older and trying to learn and have come a long long way; and,
I know too that I'm on the 3 period of the game and appreciate all that
everyone has to offer, I watch, listen, and learn, and hope you don't mind
if I ask a bunch of questions with "obvious" answers...

or

Just enjoy interacting because I appreciate your efforts too.

Sync
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