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Old 19th March 2013, 10:37 AM   #1851
Telstar is offline Telstar  Italy
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Very nice! Can you try that on the 4400A too?
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
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Old 19th March 2013, 06:52 PM   #1852
RNMarsh is offline RNMarsh  United States
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Default AD797 osc for KH4402B -

here is what the opamp change produced -->

The noise is lower as compared to previous plots I've shown and the higher harmonics are uncovered. The ref level peak on the left is -110dB. The 2H and 3H are about a little more than 20dB below reference. The higher harmonics are more than -140dB. The noise floor shown is at -145dB. [1KHz 7v p-p; 400Hz and 100KHz filter In]

KH4402B 797.jpg

Thx-RNMarsh

Last edited by RNMarsh; 19th March 2013 at 06:56 PM.
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Old 19th March 2013, 07:22 PM   #1853
davada is offline davada  Canada
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Default SVO boards

My long awaited PCBs have arrived from China.

These are development boards for my SVO design.
I panelized them to save on setup charges.

Now I have a back log of projects to catch up on since all the boards I ordered have arrived at once from various parts of the world.

Cheers,
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Old 19th March 2013, 09:17 PM   #1854
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Quote:
Originally Posted by RNMarsh View Post
The lowered noise floor is now showing me junk I had not seen before (like ps harmonics so i beefed up the filtering on the ps) and allows me to see the individual harmonics better.
You might wish to consider swapping out the 7815/7915 for 317/337 with 10uF on the adjust pin. This will knock down the noise again. (My 4402 was inexpensive compared to the ones you see on EBay as the positive regulator had failed.)

The NE5534 on my 4402B are not socketed, so mine is pretty much stock.
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Old 20th March 2013, 04:55 AM   #1855
davada is offline davada  Canada
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Quote:
Originally Posted by RNMarsh View Post
here is what the opamp change produced -->

The noise is lower as compared to previous plots I've shown and the higher harmonics are uncovered. The ref level peak on the left is -110dB. The 2H and 3H are about a little more than 20dB below reference. The higher harmonics are more than -140dB. The noise floor shown is at -145dB. [1KHz 7v p-p; 400Hz and 100KHz filter In]

Attachment 337099

Thx-RNMarsh

Hi Rick,

Can you throw up some of the previous plots along with this one for comparison?
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Old 20th March 2013, 05:40 AM   #1856
RNMarsh is offline RNMarsh  United States
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Today i tried the AD797 in two other makes/models. I got mixed results. In the KH4400, it did not reduce the THD+N. I think the circuit Z's and other elemnets are dominating . But the numbers are still pretty good --- typically .00035% using the LT1468.

Then i tried the AD797 in the HP 339A 's oscillator's opamp and retuned. I went back and forth a few times as the tuning of 3 seperate pots/trim interact and there is some compromise over the range of 1KHz -10KHz. But all in all the LT1468 is staying in as osc. The AD797 with these circuit impedances caused the THD to be higher. Splitting the THD+N with the adjustments leaves me with .00025% at 1KHz and .00065% at 10KHz. If tuning for best THD numbers at 1KHz, you can get under .0001%... but then at 10KHz it is much higher.
Note both the 339A and the 4400 use the jFEt as a control element. The 4402B does not use a jFET.

Thx-RNmarsh
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Old 20th March 2013, 05:48 AM   #1857
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by jackinnj View Post
You might wish to consider swapping out the 7815/7915 for 317/337 with 10uF on the adjust pin. This will knock down the noise again. (My 4402 was inexpensive compared to the ones you see on EBay as the positive regulator had failed.)

The NE5534 on my 4402B are not socketed, so mine is pretty much stock.
I have only tried adding more filter caps and a .47mfd bridge cap. Slightly (1-2dB noise improvement only). I have not tried changing the IC regulators.
BTW - what opamp is being used in your 4402 oscillator? Have you tried changing it, if it is still a 318?
I got .00015% with the LT1468. Lower now with the change to AD797....To just under .0001% THD+N.



-Richard

Last edited by RNMarsh; 20th March 2013 at 05:56 AM.
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Old 20th March 2013, 05:50 AM   #1858
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by davada View Post
My long awaited PCBs have arrived from China.

These are development boards for my SVO design.
I panelized them to save on setup charges.

Now I have a back log of projects to catch up on since all the boards I ordered have arrived at once from various parts of the world.

Cheers,
Thats great news. Looking forward to the results.

-Richard
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Old 20th March 2013, 06:39 AM   #1859
1audio is offline 1audio  United States
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Getting the AD797 to work in the output circuit of the KH4400 (replace the LM318) with the 50 pF wrapped around to cancel the output distortion would be the neat trick. Getting it stable would take some care.

What does the KH4403 use for AGC?
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Old 20th March 2013, 11:45 AM   #1860
PChi is offline PChi  United Kingdom
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Quote:
Originally Posted by davada View Post
My long awaited PCBs have arrived from China.

These are development boards for my SVO design.
I panelized them to save on setup charges.

Now I have a back log of projects to catch up on since all the boards I ordered have arrived at once from various parts of the world.

Cheers,
Thanks for posting the picture of the PCB. I can appreciate the effort involved in the design. I am interested in how the frequency range switching is achieved. I can see what looks like pads for the connections in the middle of the PCB so would like to see pictures of the assembled board.
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