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MCA - Son of ZCA
http://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=3942
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Author:  mwhouston [ 20 Jul 2012, 00:05 ]
Post subject:  Re: MCA - Son of ZCA

Take a look at the improvement in the SQR wave @10khz with the input cap reduced to 0.1uf. Use a very good quality cap here it is in the critical signal path. Green is original input signal and yellow the output. Remember this is at 1W close to the amp max output with little distortion.
Attachment:
10Khz1W0_1ufcapII.JPG

Author:  redsky [ 20 Jul 2012, 09:19 ]
Post subject:  Re: MCA - Son of ZCA

dtsup1 wrote:
mwhouston wrote:
From what I can hear I think the MCA out performs the ZCA!!


OMG :hot: :confused: :up:

I wish I could build one right now. Hopefully Kramme will get around to building it =)
How about testing them on your Osborns? :lildevil:


:bawling: :bawling: :bawling: I can't go without ZCA :(

But you're Rock Mark !!! :thumbsup:

Author:  KrammeAcoustics [ 20 Jul 2012, 13:35 ]
Post subject:  Re: MCA - Son of ZCA

redsky wrote:

:bawling: :bawling: :bawling: I can't go without ZCA :(

But you're Rock Mark !!! :thumbsup:


You should know that the A, in ZCA stands for Addicted. Image

Author:  KrammeAcoustics [ 20 Jul 2012, 13:44 ]
Post subject:  Re: MCA - Son of ZCA

mwhouston wrote:
From what I can hear I think the MCA out performs the ZCA!!

That's a good reason to try it ...thanks. :up:
dtsup1 wrote:
I wish I could build one right now. Hopefully Kramme will get around to building it =)
How about testing them on your Osborns? :lildevil:

I will ...this weekend. :wine:
I've got everything for this build including the 2N3055 ( mine are in TO-3 housing ) ...except 2SK170, so i have to look what i've got in stock of other Fet's, to do the job. I'll find something ...i know. 8-)

Author:  KrammeAcoustics [ 20 Jul 2012, 13:53 ]
Post subject:  Re: MCA - Son of ZCA

I've got four 2N3055 from some past scrapped late 70' amplifier. I can see they are very different in HFE measurements. I chosed T2 &T3 for the MCA.

HFE:
T1. 15
T2. 67
T3. 70
T4. 112

Author:  KrammeAcoustics [ 20 Jul 2012, 17:48 ]
Post subject:  Re: MCA - Son of ZCA

KrammeAcoustics wrote:
I've got everything for this build including the 2N3055 ( mine are in TO-3 housing ) ...except 2SK170, so i have to look what i've got in stock of other Fet's, to do the job. I'll find something ...i know. 8-)


Hmm, it seems the only components i've got in stock is BS170 and PN4302 ...both N-channel's.

http://pdf1.alldatasheet.com/datasheet- ... BS170.html

http://pdf1.alldatasheet.com/datasheet- ... N4302.html

Author:  mwhouston [ 20 Jul 2012, 19:16 ]
Post subject:  Re: MCA - Son of ZCA

Its good to see you all like the ZCA so much. It's so simple and works so well. I can't comment on the other Fets I have only used the 2SK170 BL - dead quiet and good gain. You can match the Fets too. In fact you should. I have only built one channel and mixed the two channel to give mono. But from what I heard I think it is a better performer than the ZCA. It tests much, much better than the ZCA.

My 2N3055, with 1A passing through it, stays very cool. You may only need a very small heatsink. The two 8.2ohm 10W resistors (in series to make roughly 15ohms) for the load get extremely hot. The 1ohm emitter resistor also gets very hot. I used a 0.1uf cap on the input (quality cap) and 3300uf 63V cap on the output. My B+ was 28V. I slowly brought up the bias (very easy to control) until I had 14V across the load. The bias control is very manageable with the 100K pot and 100uf cap. Just make sure you start with 0 volts bias voltage first and bring it up slowly. There is a slight lag as you adjust the bias due to the 100uf cap holding the setting. So turn slowly.

I have a couple more design ideas up my sleeve (with my arm). Let's see how well this one goes first.

Author:  redsky [ 21 Jul 2012, 11:12 ]
Post subject:  Re: MCA - Son of ZCA

mwhouston wrote:
Its good to see you all like the ZCA so much. It's so simple and works so well. I can't comment on the other Fets I have only used the 2SK170 BL - dead quiet and good gain. You can match the Fets too. In fact you should. I have only built one channel and mixed the two channel to give mono. But from what I heard I think it is a better performer than the ZCA. It tests much, much better than the ZCA.


Hi Mark,

For my interpretation on the ZCA concept. The simplicity is to avoid any noise from the component. To get the purest sounds. Is that right ?

So, I think we can start to make a fairly comparable about the ZCA.I don't know how. But I think, you all is had an good experience with high end system.

On MCA you are using 2N3055, why not using SK1058 ? I think each Fets has a specific sounds charateristic. Why not using different transistor in the same configuration ? With the same configuration, the same cable, and the same speaker it is fairly comparable if you make a conclusion about the final results.

Author:  dtsup1 [ 21 Jul 2012, 12:14 ]
Post subject:  Re: MCA - Son of ZCA

Arie, the 2N3055 is a silicon NPN bipolar transistor, while the 2sk1058 is silicon N-channel MOSFET. These are 2 totally different components. One of the aims of the MCA is to improve on the already pleasant sounding ZCA, and this is what Mark has achieved.

Author:  redsky [ 21 Jul 2012, 14:33 ]
Post subject:  Re: MCA - Son of ZCA

dtsup1 wrote:
Arie, the 2N3055 is a silicon NPN bipolar transistor, while the 2sk1058 is silicon N-channel MOSFET. These are 2 totally different components. One of the aims of the MCA is to improve on the already pleasant sounding ZCA, and this is what Mark has achieved.


:) Sorry Dinesh,Mark for OOT. I just curious how can we determine the best performance of the ZCA amp configuration. :confused: I think when we define the basic ZCA concept, we must stand for it. :eek:

People in here was conform the ZCA formula is :
• Pure resistive load
• Fashion one out of bipolar transistors
• Source connected directly to ground
• Fixed Bias

So, why not make a comparable base on that formula ??? In my opinion, the ZCA with SK1058 its must be different with a kind of resistive load ? How about to using LOT, Choke, or Lamp ? :beerchug:

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