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Removing MJE1503x in an Output Triple
Removing MJE1503x in an Output Triple
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Old 23rd February 2021, 11:15 AM   #31
Bonsai is online now Bonsai  Europe
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Removing MJE1503x in an Output Triple
Quote:
Originally Posted by jaycee View Post
AS long as you dont mind another device on the BOM, perhaps look at KSC2690/KSA1220
This is what I’m using in my EF3’s, followed by 15033/33 then NJW’s (6 pairs). The VAS uses the usual 3503 and 1381

Here Ovation High Fidelity - Model 1721
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Last edited by Bonsai; 23rd February 2021 at 11:18 AM.
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Old 23rd February 2021, 01:49 PM   #32
zergxia is offline zergxia  China
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Quote:
Originally Posted by BesPav View Post
Don't be scared, yes, i fully agree!
Just design EF3 with proper understanding like this one:
The YAP Output Stage

Sadly such an analysis aren't usual here at Diyaudio.

Dear friend, thank you for your valuable sharing.

Many medium power tubes have a higher FT than high power tubes. When the driver stage uses a high-power tube, it is slower than the frequently used medium-power tube.
I thought before that the speed of the driver stage should be fast enough to avoid becoming a bottleneck. So I tried to increase the quiescent current of the driver stage to make the speed of drives and outputs as same as possible. But the reality seems to be different~

It seems that I should connect a small capacitor in parallel between the B/C of the drive to appropriately limit the speed.

Will this cause a decrease in usable gain and deterioration of distortion performance?

Thanks again:p
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Old 23rd February 2021, 03:00 PM   #33
BesPav is offline BesPav  Russian Federation
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Quote:
Originally Posted by zergxia View Post
Dear friend, thank you for your valuable sharing.
You are welcome!

Quote:
Originally Posted by zergxia View Post
tube
Quote:
Originally Posted by zergxia View Post
B/C
Hmmm...
You meant vacuum tube? Or base-collector junction of bipolar transistor?
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Old 23rd February 2021, 03:22 PM   #34
zergxia is offline zergxia  China
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Is BJT
base-collector junction of bipolar transistor

There seems to be some small problems in translation~
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Old 23rd February 2021, 03:42 PM   #35
BesPav is offline BesPav  Russian Federation
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Quote:
Originally Posted by zergxia View Post
Is BJT
Ok

Quote:
Originally Posted by zergxia View Post
I thought before that the speed of the driver stage should be fast enough to avoid becoming a bottleneck.
Any medium power stage will be an order or two faster than audio amplifier need. So it will not become a bottleneck.

Quote:
Originally Posted by zergxia View Post
Will this cause a decrease in usable gain and deterioration of distortion performance?
Yes and no simultaneosly.
No - slowering will not nor decrease gain, nor add distortion.
Yes - slowering (based on speed of the last output transistors) will limit effective bandwidth of the output stage. Because of this you will be limited in unity gain frequency and feedback depth at higher audio frequencies, say 10-20 kHz, without complicated high-order frequency correction methods.
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