Safe Voltage for one pair of Sanken SA 1216 and SC 2922 - diyAudio
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Old 30th October 2011, 05:27 AM   #1
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Default Safe Voltage for one pair of Sanken SA 1216 and SC 2922

Hi can anybody tell me if it is safe to operate ONE PAIR Sanken 1216 ,2922 on a +/- 55 VDC supply ?
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Old 30th October 2011, 08:17 AM   #2
jitter is offline jitter  Netherlands
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Why not? Their absolute maximum ratings for Vceo and Vebo are -180 V and 180 V.
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Old 30th October 2011, 12:29 PM   #3
Bensen is offline Bensen  Belgium
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It all depents on the load. I've done a quick simulation.
With a 100% resistive 8Ohm load it would go with 1pair. But in practice with a reactieve load, things are completely different.

See the picture, it's simulated with:
- 55vDC rails
- 1 pair SC2922 at 60°C
- reactive load (phase shift 8Ohm = 35degrees, 4Ohm = 30deg, 3Ohm = 20deg)

If the goal is to drive 4 ohm speakers ==> I would go for 4pairs.
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File Type: jpg SOA 1pair 2SC2922 - 55V.JPG (187.4 KB, 204 views)
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Old 30th October 2011, 12:32 PM   #4
AndrewT is offline AndrewT  Scotland
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Cold Vce0 values tell one almost nothing of any useful value for designing the output stages of an amplifier.

Look at Bensen's sim.
The 180Vce0 line way off at bottom right does not get anywhere near the peak locus of operating conditions for any reactive load shown in the example.

BTW,
that 8ohm 35degree of phase loading represent a very moderate speaker load. A severe reactance speaker will take the loading locus even further (a lot further) outside the temperature de-rated SOAR.
1pair on +-55Vdc cannot be recommended for reliable powering of a severe reactance 8ohm speaker.

I would use 60degrees of phase loading in assessing device/heatsink suitability for severe reactance and use 45 degrees for simulating moderate reactance.
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Last edited by AndrewT; 30th October 2011 at 12:38 PM.
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Old 30th October 2011, 12:51 PM   #5
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Thumbs up Ups !

I was afraid of that. The constructor Uses 2 pair for 55 VDC. I just bought this second hand with trafoes ( Some old Scott Electronics ) It impossible to figure out how to change the Output fro them. Think I have to try different possibilities.
My Heatsink should be big enough for Class A operation this must help ? Finally it should be ok to use it for driving a midrange and tweeter in a 3 way system ?

Thank you very much for answers !
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Old 2nd November 2011, 03:53 PM   #6
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Default Cheap Toroids

Lucky me ... bought 6 x 500 VA 2x30 V toroids never used for 500 Dk.kr. It is ca. 100 AUD.
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Old 2nd November 2011, 05:28 PM   #7
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Besides SOAR concerns, adding extra pairs of output device helps performance by keeping currents below the point where the dreaded beta droop sets in.

The graph below from the 1216 datasheet shows how hfe starts to drop away at about 5A.
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File Type: jpeg 2sa1216_hfe.jpeg (49.6 KB, 150 views)
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Old 2nd November 2011, 05:46 PM   #8
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Quote:
Originally Posted by ingenieus View Post
Besides SOAR concerns, adding extra pairs of output device helps performance by keeping currents below the point where the dreaded beta droop sets in.

The graph below from the 1216 datasheet shows how hfe starts to drop away at about 5A.
Thank You ! But I just bought this old non feedback diy construction because it was very cheap second hand . As I could not use the Scott Transformers it was not cheap after all. I have a newer version of this with 4 output sets ( 5 was to much). I also have Coldamp Sonora 250 with a line stage and Coldamp Sonora 750 monobloks with 2200 W toroids and 140.000 uf for the output stage. The input stage have 4 RC stages and a discret regulator for 1/2 AD 8620.

This one we discuss ( LC Audio " The End MK 3 " ) could be only for Treble and Midrange or I will just sell it.

But it is nice to learn something new .
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Old 2nd November 2011, 07:37 PM   #9
sajti is offline sajti  Hungary
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The Marantz PM11S1 use single pair of 2292/1216 with +/-65V

Sajti
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Old 2nd November 2011, 07:39 PM   #10
AndrewT is offline AndrewT  Scotland
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I wonder what protection and/or limiting Marantz incorporate?
I wonder what the warranty claims are like for that model?

Or is it a ClassXYZ that lightly stresses the output devices?
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