Author Topic: Initial Test Questions

May 13, 2021, 01:48:53 PM
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Buffstuffbuddha

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Just to clarify, should measurement of the source sign wave be verified between tip and ring (pin 2 and 3)? For example, the 1khz sign wave should measure .4v between tip and ring before going into the unit?

All output measurements are also done between tip and ring (xlr pin 2 and 3)?

Is every test measured in output bypass?

My units appear to be functioning correctly but the output is incredibly low even with the output at 10. When running a track through them 9out of pro tools) I need to come out of the tape sim into another preamp just to get it back to a useful level. I want to make sure nothing is messed up or I didn't accidentally calibrate the meter wrong. 

Performing test 1 (1khz at .4v) I get .38v after all 3 settings. If I engage the unit engaged (not in bypass) I have:
tape left -10.84
tape center -  8.58
tape right - 7.86


Test 2 with unit engaged (not in bypass) I have:
30 ips - 7.4 v
15 ips - 8.98v
7.5 ips - 9.9v

I ran out of time to continue testing this morning but I at least wanted to get this thread started. I feel though as something may be wrong here. I am testing 2 of these units simultaneously as they were built together.

May 13, 2021, 02:12:41 PM
Reply #1

Buffstuffbuddha

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The more I think about it I have a feeling that I messed up and calibrated the meters too low as both units are identical. I will have to verify later.
« Last Edit: May 13, 2021, 02:18:13 PM by Buffstuffbuddha »

May 14, 2021, 01:10:33 AM
Reply #2

Buffstuffbuddha

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Test 3 with unit engaged:
7.5 ips - 7.23v
15 ips - 9.17v
30 ips - 8.35

Test 4 with unit engaged:
7.5 ips - 5.19v
15 ips - 7.66v
30 ips - 8.8v
bias on right - 6.08v

Test 5 with unit engaged:

7.5 ips - 2.53v
15 ips - 5.03
30 ips - 7.73
7.5 ips with bias right - 7.81

After performing all tests on both modules the second module's reading are within +/-0.5v of the results listed. They are generally much less than 0.5v difference.

May 14, 2021, 01:36:27 AM
Reply #3

Buffstuffbuddha

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I have also double checked the meter calibration and it appears to be correct. A 1 khz sine wave at 1v just barely lighting the last LED (the one at the very top of the meter) gives me about 6.5v between points 0v and TP2. Apparently everything is working as intended and I'm just crazy. I just thought there would be more gain coming out of the unit. On a mix bus being sent to these units staying at about the top of the green meter with the output at 10 I still have to crank my line inputs back into Pro Tools to get any useable level.

May 17, 2021, 09:13:05 AM
Reply #4

JPK

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Quote
Just to clarify, should measurement of the source sign wave be verified between tip and ring (pin 2 and 3)? For example, the 1khz sign wave should measure .4v between tip and ring before going into the unit?
All output measurements are also done between tip and ring (xlr pin 2 and 3)?
Yes correct.
Quote
Is every test measured in output bypass?
No, output must be ON.
Quote
A 1 khz sine wave at 1v just barely lighting the last LED
A 1Vrms sine on input should light up the red clip LED when the DRIVE pot is around 8-9.
But this is only true if the TAPE SAT switch is on -.
If it is on ~ or + the output is lower.
JPK

May 25, 2021, 02:25:33 AM
Reply #5

Buffstuffbuddha

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1 khz at 1 Vrms lights up the last (top) red LED when Drive knob is set to 8 and Tape Sat set to -. With Tape Sat set to + it never lights last LED even with Drive knob at 10. With Tape Sat set to ~ the last LED lights up with Drive knob at about 8.5. All of that makes sense based on your description. Can you just verify it seems to be working as intended?

May 25, 2021, 03:09:36 AM
Reply #6

Buffstuffbuddha

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Is there a way I can measure the output level to make sure everything is fine on that end?

May 25, 2021, 10:25:53 AM
Reply #7

JPK

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Quote
1 khz at 1 Vrms lights up the last (top) red LED when Drive knob is set to 8 and Tape Sat set to -. With Tape Sat set to + it never lights last LED even with Drive knob at 10. With Tape Sat set to ~ the last LED lights up with Drive knob at about 8.5. All of that makes sense based on your description. Can you just verify it seems to be working as intended?
All this is correct.


Quote
After performing all tests on both modules the second module's reading are within +/-0.5v of the results listed. They are generally much less than 0.5v difference.
This means your units are working.
JPK

May 25, 2021, 10:55:23 AM
Reply #8

Buffstuffbuddha

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Awesome, thank you.