Studio Reference Amplifier

[shravanth]

apex sir R24 - 10k is started getting heat at test voltage 24-0-24 VDC

 

[shravanth]

Shr,
have you calculated currents for that relay driver circuit?

The tip is supposed to be a switch. How much base current does it need to become saturated, so that it can act as a switch?

The BC transistors will have a Vce that is very low.
Again, have you looked at what base current the detector transistors need to operate with low Vce?

Yep.. sorry i dont know how to calculate

plz share a link for speaker protection

 

[AndrewT]

What current does the relay need when supplied with 12V?
What hFE does the transistor switch work at, when it is saturated?
What is the base current required to saturate the switcher?

It is all very simple.

 

[apexaudio]

apex sir R24 - 10k is started getting heat at test voltage 24-0-24 VDC

R24 must be hot, use 1W or 2W resistor.

 

[Walkalone]

I'm attach my amp, X250MkIV with cascoded IPS & VAS by JFET.
The lasted schematic like this pic, but Vas's current mirror is compensation transistor type (sorry, i'm using a computer which can't get the picture).
The sound is very good, more than my Goldmund clone, very clear...

I can't use LTSpice to simulation this schema. I want know THD, SR. Any one can help me and suggest me for this amp to better?

 

[apexaudio]

Yep.. sorry i dont know how to calculate

plz share a link for speaker protection

Post #28 http://www.diyaudio.com/forums/solid-state/235892-1000w-simple-pa-amplifier-3.html

 

[rsavas]

I can't use LTSpice to simulation this schema. I want know THD, SR. Any one can help me and suggest me for this amp to better?

Should start your own thread first.

 

[shravanth]

R24 must be hot, use 1W or 2W resistor.

ok sir. can i replace zobel and o/p resister with 10ohm 5w

 

[Walkalone]

Should start your own thread first.

LTSpice is strangely in my country, mainly are OrCAD & Multisim. I've used multisim and feel it is not good. I don't know, i'm trying to learn use LTSpice.

//However, the amp in real life is very good, one of my best in current.

SR100 & SR200 can use tantalum caps in input & feedback. This's can get better sound. I used Vishay 150D 10uF & 100uF/20V paralled with 1uF MKT caps.

 

[apexaudio]

ok sir. can i replace zobel and o/p resister with 10ohm 5w

Yes but 2W will be ok.

 

[shravanth]

Apex sir at what voltage that relay will turn off in that speaker protection from Post #28 1000W Simple PA Amplifier. , and what is pro LED.

 

[JOHN BALI]

Apex sir at what voltage that relay will turn off in that speaker protection from Post #28 1000W Simple PA Amplifier. , and what is pro LED.

Hi Shravanth, please post it in the right thread.
If you post here it is off topic & can make us confuse.
Pro led used to indicate that our amp is in trouble, blink when something not good happen.
My SR200 not use relay & no thump when switch on or off
so we don't need any relay here.

I use only SR800 pcb for all SR amplifiers, and DC protect with triac was integrated on it also zobel network and fuses. FET instead BJT for LTP can be used without changes, I suggest 2SK117.

Ok, thanks Sir Apex
I will try to find 2SK117, if not available I will try 2SK170 (I have few left)

Regards

 

[apexaudio]

Ok, thanks Sir Apex
I will try to find 2SK117, if not available I will try 2SK170 (I have few left)

Regards

Only SR800 can use fet input pair instead bjt, it use npn input pair biased with 3mA, SR50,100,200 use pnp input pair biased with 1mA.
Regards

 

[carlmart]

OK, where can I find schematic and/or pcb depiction for Apex SR800?

 

[thimios]

sr800

OK, where can I find schematic and/or pcb depiction for Apex SR800?

I ask many times but no answer yet.

 

[carlmart]

I think Apex does not share that schematic.

Apex, can we use Walkalone fet arrangement for LTP then?

Edit: sorry, I'm talking rubbish. To use that arrangement all transistors after the LTP would have to change too, from NPN to PNP and viceversa.

The right way would be to use the 2SK170 complementary: two 2SJ74 or a dual 2SJ109 (if available). Would they work biasing for 3mA?

 

[chithanh2507]

Hi Apex. I have not found LF411. I can replace it with TL071 or TL081?
Sorry for my english is bad.

 

[AndrewT]

Look for a FET input opamp that has low temperature variation offset and low absolute offset.

 

[apexaudio]

I think Apex does not share that schematic.

Apex, can we use Walkalone fet arrangement for LTP then?

Edit: sorry, I'm talking rubbish. To use that arrangement all transistors after the LTP would have to change too, from NPN to PNP and viceversa.

The right way would be to use the 2SK170 complementary: two 2SJ74 or a dual 2SJ109 (if available). Would they work biasing for 3mA?

I will share schematics of my new amplifiers HD50, HD150 and HD300 with J fets in LTP...

 

[JOHN BALI]

Only SR800 can use fet input pair instead bjt, it use npn input pair biased with 3mA, SR50,100,200 use pnp input pair biased with 1mA.
Regards

Ok, thanks...

Edit: sorry, I'm talking rubbish. To use that arrangement all transistors after the LTP would have to change too, from NPN to PNP and viceversa.

The right way would be to use the 2SK170 complementary: two 2SJ74 or a dual 2SJ109 (if available). Would they work biasing for 3mA?

So use the p-ch j-fet, but the fet is not available here & also they must be matched too

Hi Apex. I have not found LF411. I can replace it with TL071 or TL081?
Sorry for my english is bad.

Yes, you can use TL071.
I use TL071 at my first SR200 next one I use LF411(get it online from my friend)

I will share schematics of my new amplifiers HD50, HD150 and HD300 with J fets in LTP...

Yes... this is what we waiting,
but with layout or no?

Regards