Sankes is good... On-Semiconductor?

Danyele82 · 27th April 2004, 06:17 AM

What we you think about the transistors of On-Semiconductor (MJL3281/MJL1302) in place of Sanken (2SA1295/2SC3264) in the output stage of this amplifiers?

And About the ON (MJE15030/MJE15031) in place of Q3 and Q4?

The oueput transistor are 2 pair (not 1 pair like the image)!!!

JonMarsh · 27th April 2004, 10:15 PM

While there's not quite enough information on your schematic to make a real "design review",

and you haven't stated your desired load impedance, I think it's safe to say that one could respond with a resounding "maybe".

Seriously, you must consider that the On Semi transistors are fairly wideband, and in my experience, using them in the circuit you have shown "Exactly as drawn" could be problematic, because there are no base stopper resistors or other methods for controlling local oscillation. Wideband amplifiers can change into high frequency oscillators under a variety of conditions. I'd expect any of the faster extended beta Sanken's to behave the same way, as well as the Toshiba's.

Is this a published design with a PCB layout? Capacitor coupled output, too? Not the best way to go; check Douglas Self's book about the details regarding output capacitor LF distortion.

If you are enamored of the possibility of a vacuum tube plus solid state amp you can build, Hawk Audio in NL has a nice kit with a vacuum tube front end, MOSFET output stage, and direct coupled at the outputs. Also, it is a non loop feedback design.

Regards,

Jon

Danyele82 · 27th April 2004, 10:28 PM

This is the schematic that i won't to use!!

Danyele82 · 28th April 2004, 11:13 AM

This is the layout of the original version:

janneman · 28th April 2004, 11:46 AM

There is no DC reference for the output stage, the output DC is undefined. So, unless you somehow ground-reference the SS part like with resistors from Q1, Q2 base to ground, your speaker will be short lived.

Jan Didden

Andypairo · 28th April 2004, 12:10 PM

The amp Daniele is referring to is the GY-50 by Bartolomeo Aloia, who is a very good designer.
This is a project I could have been interested into, if I hadn't bought a bunch of Mullard ECC88s

I think that the MJL3281/1302 can be just fine (better MJL4381 and 4302), check the SOA if you plan to use them on tough loads.
The drivers can be the 15030/31 (or the more recent 15033/34).. after all it is, IIRC, a 50W amp....

Cheers

Andrea

PS Daniele, where do you buy the HT trafos?

Edit: the amp is made for single supply, so don't modify it unless you really know what you're doing!

Danyele82 · 28th April 2004, 12:52 PM

Quote:

Originally posted by Andypairo
Edit: the amp is made for single supply, so don't modify it unless you really know what you're doing!

The amplifiers is for car use!
The power supply is a SMPS.

Charles Hansen · 28th April 2004, 02:12 PM

Quote:

Originally posted by janneman
There is no DC reference for the output stage, the output DC is undefined. So, unless you somehow ground-reference the SS part like with resistors from Q1, Q2 base to ground, your speaker will be short lived.

Actually, as long as the supply rails are driven by a transformer with an accurate center tap (bi-filar winding), you won't have any problem. You will also want to use 1% values for the resistors connecting the bias circuit to the supply rails.

Danyele82 · 28th April 2004, 04:16 PM

all the resistances that I will use are to 1% and all the transistors will be select to

K-amps · 28th April 2004, 07:57 PM

I'd use an extra output pair just for the extra headroom.

The drivers you suggest are good too.

27th April 2004, 06:17 AM	#1
Danyele82 diyAudio Member Join Date: Mar 2004 Location: Como	Sankes is good... On-Semiconductor? What we you think about the transistors of On-Semiconductor (MJL3281/MJL1302) in place of Sanken (2SA1295/2SC3264) in the output stage of this amplifiers? And About the ON (MJE15030/MJE15031) in place of Q3 and Q4? The oueput transistor are 2 pair (not 1 pair like the image)!!!

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27th April 2004, 10:15 PM	#2
JonMarsh diyAudio Member Join Date: Jan 2002 Location: Livermore, CA	While there's not quite enough information on your schematic to make a real "design review", and you haven't stated your desired load impedance, I think it's safe to say that one could respond with a resounding "maybe". Seriously, you must consider that the On Semi transistors are fairly wideband, and in my experience, using them in the circuit you have shown "Exactly as drawn" could be problematic, because there are no base stopper resistors or other methods for controlling local oscillation. Wideband amplifiers can change into high frequency oscillators under a variety of conditions. I'd expect any of the faster extended beta Sanken's to behave the same way, as well as the Toshiba's. Is this a published design with a PCB layout? Capacitor coupled output, too? Not the best way to go; check Douglas Self's book about the details regarding output capacitor LF distortion. If you are enamored of the possibility of a vacuum tube plus solid state amp you can build, Hawk Audio in NL has a nice kit with a vacuum tube front end, MOSFET output stage, and direct coupled at the outputs. Also, it is a non loop feedback design. Regards, Jon

27th April 2004, 10:28 PM	#3
Danyele82 diyAudio Member Join Date: Mar 2004 Location: Como	This is the schematic that i won't to use!!

28th April 2004, 11:13 AM	#4
Danyele82 diyAudio Member Join Date: Mar 2004 Location: Como	This is the layout of the original version:

28th April 2004, 11:46 AM	#5
janneman diyAudio Member Join Date: May 2002 Location: Where Germany, The Netherlands and Belgium meet Blog Entries: 6	There is no DC reference for the output stage, the output DC is undefined. So, unless you somehow ground-reference the SS part like with resistors from Q1, Q2 base to ground, your speaker will be short lived. Jan Didden

28th April 2004, 12:10 PM	#6
Andypairo diyAudio Member Join Date: Sep 2002 Location: near Milano , Italy	The amp Daniele is referring to is the GY-50 by Bartolomeo Aloia, who is a very good designer. This is a project I could have been interested into, if I hadn't bought a bunch of Mullard ECC88s I think that the MJL3281/1302 can be just fine (better MJL4381 and 4302), check the SOA if you plan to use them on tough loads. The drivers can be the 15030/31 (or the more recent 15033/34).. after all it is, IIRC, a 50W amp.... Cheers Andrea PS Daniele, where do you buy the HT trafos? Edit: the amp is made for single supply, so don't modify it unless you really know what you're doing!

28th April 2004, 04:16 PM	#9
Danyele82 diyAudio Member Join Date: Mar 2004 Location: Como	all the resistances that I will use are to 1% and all the transistors will be select to

28th April 2004, 07:57 PM	#10
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	I'd use an extra output pair just for the extra headroom. The drivers you suggest are good too.

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