Bravo mayday! I lake the wooden front.
I just received the chasis so this weekend I finish my Amp.
I'm using OPA2134 and AD744 but at the moment I haven't decided.
I just received the chasis so this weekend I finish my Amp.
I'm using OPA2134 and AD744 but at the moment I haven't decided.
My half cent.😀
Lehmann BCL Rebuild, measurement of beta version of my own PCB.🙂
Lehmann BCL Rebuild, measurement of beta version of my own PCB.🙂
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Hi blackdod,
Very nice enclosure (6mm or 8mm front panel ?), where did you get it?
It´s a good idea to have the mains switch on the front.
Which transformer do you use?
Very nice enclosure (6mm or 8mm front panel ?), where did you get it?
It´s a good idea to have the mains switch on the front.
Which transformer do you use?
An impressive THD figure, do you think this is the result of the increased BIAS current of 175mA ( the orig. circuit is 40 - 50mA BIAS)?
Is the quiescent point stable with 175mA? , have you changed the value of the emitter resistors (10R)?
Thanks but is easy to do. 😱
You can buy the chassis on ebay and the R-core too.
This chassis is for Lehmann clones so is easy work with him. You only need do some holes on the floor. Front pannel is 8mm and have all holes.
R-core is a 15-0 volt X2. I prefer a r-core because It is quieter that a toroid.
I used aluminum feet too for a "luxury look" 😛😛
About emiter resistors, it´s an interesting mod. It would be interesting replaced by 5 Ohm but I think that the hot on MOSFET would be a problem... if you use the original PCB.
You can buy the chassis on ebay and the R-core too.
This chassis is for Lehmann clones so is easy work with him. You only need do some holes on the floor. Front pannel is 8mm and have all holes.
R-core is a 15-0 volt X2. I prefer a r-core because It is quieter that a toroid.
I used aluminum feet too for a "luxury look" 😛😛
About emiter resistors, it´s an interesting mod. It would be interesting replaced by 5 Ohm but I think that the hot on MOSFET would be a problem... if you use the original PCB.
Thanks for the hint about R-core transformers. I never used one, but I had a closer look to them right now. It seems that they indeed have some advantages in comparison with toroidals. I think I will give it a try in one of my next projects.
When you say quieter, do you mean less mechanical vibrations or lower stray magnetic fields?
I wonder why R-cores are rarely used in commercial audio products, are they more expensive?
When you say quieter, do you mean less mechanical vibrations or lower stray magnetic fields?
I wonder why R-cores are rarely used in commercial audio products, are they more expensive?
I've got both, the R-Core 2x15Vac 30VA is to be used in a modular DAC I'm building, unless I swap them...using the Toroid in the DAC as that will have a separate enclosure for the transformers anyway.
Yes, I always use r-core when I want to use only one enclosure because R-core has less mechanical vibrations and lower stray magnetic fields (HUM noise).
Other example on my Pass HA:
http://www.diyaudio.com/forums/pass...-your-diy-pass-amplifier-355.html#post4699302
The problem is that the r-core is more expensive and you have less volt for choose vs a toroid.
Other example on my Pass HA:
http://www.diyaudio.com/forums/pass...-your-diy-pass-amplifier-355.html#post4699302
The problem is that the r-core is more expensive and you have less volt for choose vs a toroid.
Thanks for the info.
I had a look to the pics. of your Pass headamp. I have to say that I like the way of your wiring, very clear and tidy
I had a look to the pics. of your Pass headamp. I have to say that I like the way of your wiring, very clear and tidy
Yes and no. I had some tries with different BIAS currents on my test setup (breadboard).
In one case BIAS ran away till transistors started to smoke. I don´t know what happened, probably a mistake in my setup? I had a debate about that with damon1983 (via PM) and he stated that it´s no problem to increase BIAS up to 500mA.
In the moment I can´t give any instrutcions, because I don´t see clear regarding this topic.
In one case BIAS ran away till transistors started to smoke. I don´t know what happened, probably a mistake in my setup? I had a debate about that with damon1983 (via PM) and he stated that it´s no problem to increase BIAS up to 500mA.
In the moment I can´t give any instrutcions, because I don´t see clear regarding this topic.
Ok, thanks Andreas.
It's A interesting mod. I will waiting your comments but 500mA BIAS is not a little aggressive for this amp?
It's A interesting mod. I will waiting your comments but 500mA BIAS is not a little aggressive for this amp?
Yes you are right, 500mA BIAS is overkill for a headamp.
But anyway, higher BIAS requires bigger heatsinks. I´m not sure if original heatsinks are sufficient.
But anyway, higher BIAS requires bigger heatsinks. I´m not sure if original heatsinks are sufficient.
And original stock heatsinks are not heatsink, it's like a scary joke.😡
I don't know, why they made bias 40 mA for discrete's class A. If needed low power amp - THS4062 (as example) will be enough.🙂
2V RMS to 4R+0,47uF measurements. (THD 1 kHz=0,46%) (BIAS=175 mA)
