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Dirt Cheap Stax Amp DIY - new schematic updated! - Page 7

post #91 of 103

while according to the Tube Cad articles the name SRPP is a recent invention - with ambiguous interpertations - I don't think it can be stretched to cover the present circuit

 

you have "feedforward" push-pull - the bias/pull down current is modulated by the amplified signal V, scaled by a R and current mirror

 

there is no connection to the load current demand - it could be helpful if it "lined up" with the load demand - but with ES headphones being a fair capacitor it doesn't happen here


Edited by jcx - 4/13/13 at 9:40am
post #92 of 103
Thread Starter 
Quote:
Originally Posted by jcx View Post

while according to the Tube Cad articles the name SRPP is a recent invention - with ambiguous interpertations - I don't think it can be stretched to cover the present circuit

 

you have "feedforward" push-pull - the bias/pull down current is modulated by the amplified signal V, scaled by a R and current mirror

 

there is no connection to the load current demand - it could be helpful if it "lined up" with the load demand - but with ES headphones being a fair capacitor it doesn't happen here

I agree, while I was testing the output wave form, I found out even though this circuit has overall flatter FR, but I also tried loading the upper two transistors with resistors or CCS load. and resistor load clips very clean and smooth, sounds like a triode, CCS is a little harsh when clipping, while this SRPP thing clips very harsh. I will try to play with higher idle current once I received the heat sinks I ordered a while ago. 

 

I think a CCS loaded emitter follower can do what you were describing here. emitter follower makes sure the voltage is right and CCS is making sure the current is there when demanded by the C load, especially when output voltage is at max, when current is 0 or when voltage is at 0 and output current is at max. 


Edited by wdiabc - 4/13/13 at 10:01am
post #93 of 103
Sorry if this is gravedigging...
I'm probably going to end up building my own stax amp and don't even know where to start xD
If someone could help me, that'd be awesome
post #94 of 103

Go to the other site.........

post #95 of 103
Just start with the T2. Live hard or die trying.
post #96 of 103

Yeah, there site would be good and also what you'd want to build (tube, SS etc.).  Since I just posted it in the Stax thread, this is quite cheap:

 

 

Not really done for high performance and more for being odd.  smily_headphones1.gif

post #97 of 103

Sorry, stupid impulse post. When i stopped and think abut it i realized it is a dangerous, stupid idea.

 

Hi

 

I needd a Stax amp quick for testing purposes and this seems to fit the bill pefectly! Just one question, I live in Sweden we have 230v. Thats about 330v retified. Some cleaning and a simple regulator could take it down to 300. Same goes for the bias supply. Do i need a transformer at all?

 

Best Regards Christian


Edited by ervstil - 5/27/14 at 9:02am
post #98 of 103

For safety sake, yes you need a transformer. 

post #99 of 103
This is quite interesting.. Suitable for a first 'real' project?
post #100 of 103

I am interested in having a go at the updated circuit in post #1. I have a couple of questions please.

 

1. Is the OP still watching?

 

2. The ‘final circuit’ in post #1 shows 2N3904’s, but text below refers to MPSA42’s — which it then says are replaced by TIP500’s (what’s that?).  So, OK, what are the final-choice transistors that I should use?

 

3. I cannot see a PSU schematic in the thread. What should it look like? Including the 580V bias feed to the stator?

post #101 of 103
Quote:
Originally Posted by T N Args View Post
 

I am interested in having a go at the updated circuit in post #1. I have a couple of questions please.

 

1. Is the OP still watching?

 

2. The ‘final circuit’ in post #1 shows 2N3904’s, but text below refers to MPSA42’s — which it then says are replaced by TIP500’s (what’s that?).  So, OK, what are the final-choice transistors that I should use?

 

3. I cannot see a PSU schematic in the thread. What should it look like? Including the 580V bias feed to the stator?


Bumping my own post after 6 days, hope that's okay. Maybe others have the answers? Tho OP looks to have left.

post #102 of 103

hi chinasettAWONG, do you think it might be possible to build stators like the srl700 or sr009?? I might try and buid them, or my friend whohas a cnc is going to be doing a set for me to retrofit in a set of 507s I see the plates are like nb lambda ones in that they have smaller holes closer together we will be milling them from brass plate and it shall be exiting to hear the outcome .. might take about 3;4 weeks il keep you posted .p.s...have you made any esoteric stator designs?? I personally think the more rigid the stator, the better the sound will be .. cheers.

post #103 of 103

spritzer where can I find the schematic of the small pcb you have pictured with 8 small valves?

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