[Jan Meier]

Dear Headfellows,

I just updated the article on the DIY-headamp on my homepage with the schematics of the HA-1 MkII.

http://home.t-online.de/home/meier-audio/headamp.htm

Enjoy!

Jan

 

[Voodoochile]

That's very generous of you, Jan. I am sure many here will both appreciate and respect that.

 

[00940]

Hi Jan, thanks a lot for this

A few questions :

* we can see what looks like a 1W resistor at the back of the transformer, is this one of the 0.22R resistors in the PS ?

* you're using little yellow caps (I assume MKT ??) except for two big blue ones (MKP ?). Which caps need a better quality ? I'd guess the 100nF in the crossfeed ?

* In the PS, you have five 220nF caps going from rail to rail, what are they for ?

 

[Wodgy]

Thanks so much Jan!

One question: is there any reason you chose to use a simple resistor to V- as your technique for biasing the amp into class A, as opposed to a CRD or JFET cascode?

 

[Jan Meier]

* we can see what looks like a 1W resistor at the back of the transformer, is this one of the 0.22R resistors in the PS ?

No, it's the 4.7 Ohm resistor of the ground-loop breaker.

* you're using little yellow caps (I assume MKT ??) except for two big blue ones (MKP ?). Which caps need a better quality ? I'd guess the 100nF in the crossfeed ?

The yellow caps are the 220 nF polyester caps from the powersupply. The blue ones are the 100nF polypropylen from the crossfeed.

* In the PS, you have five 220nF caps going from rail to rail, what are they for ?

4 are placed directly to the opamps. The fifth is placed near the 2 BUF634 output buffers.

"is there any reason you chose to use a simple resistor to V- as your technique for biasing the amp into class A, as opposed to a CRD or JFET cascode?

Costs! The HA-1 MkII is the entry-model of the CORDA range. In the other models (HA-2, PREHEAD) I use current sources. As I do have to protect some commercial interests I will not make the schematics of these amps public. I'm sure you will understand.

Cheers,

Jan

 

[the_villain]

Great. I already ordered the parts for corda ha1 but that's ok. Thanks Jan. You remind me about the Linux community- it's always good to share. Thanks again.

 

[ITZBITZ]

This looks pretty sweet. Is there a place to order PCB's or a kit?

 

[the_villain]

Hi again, Jan. I have already ordered 10VA torroidal transformer for Corda Ha 1. Would it be OK for Ha1 MkII. Thanks .

 

[Jan Meier]

> Is there a place to order PCB's or a kit?

I'm sorry, but for (commercial) reasons I do not sell single PCB's. Please understand.

> I have already ordered 10VA torroidal transformer for Corda Ha 1. Would it be OK for Ha1 MkII.

That would be very fine, but it might be that you have to increase the values of the fuses as the in-rush current will be increased.

Have fun building.

Jan

 

[ITZBITZ]

Quote:

Originally posted by Jan Meier > Is there a place to order PCB's or a kit? I'm sorry, but for (commercial) reasons I do not sell single PCB's. Please understand. Jan

Ok. I just thought I read in the old headwize article that you could but a kit to build the amplifier (including the PCB and the case).

 

[lini]

ITZBITZ: That kit was for the original, bigger and simpler HA-1 only. Afair, Jan thought the MkII required more soldering skill than usually available in average diy Joes - and thus decided not to offer the MkII in a kit version at all. Better than dealing with a horde of disappointed diy newbies, who'd probably fail in assembling a complicated kit, I guess...

Greetings from Munich!

Manfred / lini

 

[A3rd.Zero]

Wow. This is not a unique post but just the same. Thank you. I was on your website a little while ago and I said to myself. "Boy its really sweet that he gives the schems for the basic amp, which I love , and then sells the upgraded version". Then I got mad, at myself, for being as selfish as to think that maybe he would post the schems for one of the upgraded amps, and now you go and do it! Boy I am so happy, and humbled.

Thank you again,

Milo