DIY Audio Projects Forum

MCA - Son of ZCA
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Author:  mwhouston [ 07 Feb 2018, 22:07 ]
Post subject:  Re: MCA - Son of ZCA

Provide some images and listening notes. Did you stick 100% to the component suggestions?

Author:  ILoveHiFi [ 27 Feb 2018, 04:49 ]
Post subject:  Re: MCA - Son of ZCA

bugeyes wrote:
with an 8 ohm 10w resistor across the binding post I get 0.0mv :wine:
thanks so much for the help, onto stabilizing the bias

Wihout load seeing 14v at outpu is normal.
The proper way of fixing this is to connect a resistor 1M ohm at the output. I would recomend any 1/4w resistor or larger with 100k to 1m resisance.

Without any resistors connected to ground at the output, the output is floating and the voltage will be unkown.

I've seen this plorbem with one of my pre amps, during testing no resistors are connected at input, the input goes through capactor to amp. I was seeing a few volts I thought something was wrong.
Once I connected a 470k at intput instantly fixed the plorbem

Author:  Gerti [ 20 Jun 2019, 13:15 ]
Post subject:  Conversion from ZCA to MCA not successful

Today I tried to convert my ZCA to MCA.
All worked well, voltage adjusted at 12V, speaker hooked up and:

The hearing impression was terrible.

I switched between the the 3055 and the 2sk1058 for 5-6 times (Fixing screws, voltage adj............)
Nothing got better, harsh cymbals, harsh saxophone.
The smoothness, softness of the ZCA was lost.

I added some images of the parts u use.
Do they look counterfeit? The 3050 sideview looks mysterious...

I have no idea what is happening here.


Author:  mwhouston [ 20 Jun 2019, 18:43 ]
Post subject:  Re: MCA - Son of ZCA

Not sure what the problem is here. I only made a rough prototype and thought it sounded OK. I don’t think that even if the parts were counterfeit that it would explain the poor performance.

Did you put it on the CRO to see if the signal is clean?

Author:  Gerti [ 21 Jun 2019, 04:52 ]
Post subject:  Re: MCA - Son of ZCA

Monday at work I have access to a CRO.
Otherwise I would buy 3055 from different sources and have a try...........
Only the 2sk170 was difficult to get.
Any Ideas for a replacement?


Author:  ILoveHiFi [ 21 Jun 2019, 04:54 ]
Post subject:  Re: MCA - Son of ZCA

Fake transitors don't make any diffrence. Not enough for you to say "smoothness, softness of the ZCA was lost"

RS components only sells 100% geniune components all the time and gaurnanteed. They also offer free shipping even if you buy a single 1/4w resistor.
The k170 looks very geniune don't waste your time

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