Dartzeel amp schematic - build this?

[Erlend Sæterdal]

Dual mono two transformers - one enclosure. 2.2 kohm 100 nf and antiparralel rectifiers between the gnd's.

 

[Erlend Sæterdal]

So disappointed this evening in Copenhagen. With signal -not shorted- as earlier there is huge hum. So have to work with it. Sound is to the dark side. One little speaker only wich I always try before using my expensive Duelund speakers.

One channel with no signal there is no hum. So maybe 4.7 - 10 ohm on the ground inputs.

With the resistors it got worse. Maybe because there is Transformers at output in my PS Audio dac. Will try a buffer between.

 

[Erlend Sæterdal]

Got to take this out again I think.

 

[marigno]

In this amplifier, the hum is very loud when the input is not connected. Once you short the input with 1KOhm or connect it to a source, the hum disappears. With or without the ground coupler.

 

[dmarget5]

Today I measured HFE at 20 pieces of MJE 15032g (most of them have a gain of 46) and 20 pieces of MJE15033g (most of them have a gain of 150).

Does anyone have transistors with similar values (for any) so he could pair them more accurately?

 

[Paroxod4]

Probably you are measuring with a Chinese tester, if you measure at a base current of 10 ma, you will get an excellent result.

 

[dmarget5]

No, with Metex M-3800 my old multimeter.

 

[dmarget5]

Probably you are measuring with a Chinese tester, if you measure at a base current of 10 ma, you will get an excellent result.

Can I do this like this:


What are the values of the 10 mA base current resistor?

 

[Paroxod4]

Dear dmarget5 when I measure with my dy294 tester these transistors for a base current of 10 ma they show 5 percent

 

[dmarget5]

With what base current should output transistors be measured? Is a 15V voltage OK?

 

[dmarget5]

Dear dmarget5 when I measure with my dy294 tester these transistors for a base current of 10 ma they show 5 percent

DUOYI DY294 Digital Transistor Tester Semiconductor Tester Multimeter Tester Electrical Instrument - Multi Testers - Amazon.com

This tester?

 

[analog_sa]

Probably you are measuring with a Chinese tester, if you measure at a base current of 10 ma, you will get an excellent result.

Why would he want to match them @10mA Ib when in the circuit they work at less than 1mA?

 

[Paroxod4]

DUOYI DY294 Digital Transistor Tester Semiconductor Tester Multimeter Tester Electrical Instrument - Multi Testers - Amazon.com

This tester?

yes

 

[Erlend Sæterdal]

Still have a Hum problem when using two channel input. I use seperate transformers for each channel and separate capacitor banks. Should I mount earth common as soon as possible after the rectifiers maybe? Get more grey hair from this.

 

[marigno]

I would suggest this cabling schema. The only common point point between the two channels is after the ground coupler.
It is intended to be a physical schema, do not move any joint.
With this cabling, I never had hum problems.

 

[K-amps]

Here in the US, I wonder if the neutral and the ground are tied together up the home distribution box, in such a case, the transformer center tap might have a voltage difference with respect to ground. Should this be a concern?

 

[marigno]

I'm in Utah. I opened the distribution box some days ago, without paying too much attention to the cabling, and I think you're right, neutral and ground are connected together. I'm using a 3KVA auto-transformer because, coming from Italy, all my stuff works with 230Vac. I see we have 230Vac also but it is used only for the stove and I don't want to do the job of extending the cabling. So my audio set is working with mixed voltages (all sources work with 115Vac) but I don't see any problem.

 

[K-amps]

Yes, our home is split 2 phase (center tapped) with each 115vac phase out by 180 degrees. You can connect across 2 AC socket lives to get your 230vac

 

[marigno]

That is a very good clue! I didn't know. Thank you!
I'll open the distribution box again to better understand the cabling and, If I can find two outlets, close to the audio set, having different cablig, hopefully thier phases could be inverted. If so, I could disconnect the auto-transformer that, being chinese, runs hot.

 

[Miros]

Still have a Hum problem when using two channel input. I use seperate transformers for each channel and separate capacitor banks. Should I mount earth common as soon as possible after the rectifiers maybe? Get more grey hair from this.

I’m using the same coupling as “marigno” no hum.
As the GND coupler I’m using two CL-60.
It works for me every time.