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 Post subject: Re: MCA - Son of ZCA
PostPosted: 10 Dec 2014, 17:23 
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Joined: 09 Apr 2013, 02:59
Posts: 48
Location: Germany
Yes, I do like to Play around with the Input and Output caps also.
The SCR in parallel with the electrolytic ones works fine with the ZCA. I will try the Output caps only with the MCA.

For Input caps i have the choice of orange Drops, Wima, Roederstein and SoZo mustard caps. I will have a listen to all of them ;)

regards
Stefan

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 Post subject: Re: MCA - Son of ZCA
PostPosted: 10 Dec 2014, 17:25 
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Joined: 31 Dec 2008, 15:34
Posts: 441
max130 wrote:
It is 4.4 V over 4.7 Ohm so a Little less than 1A for each resistor in my calculation.
The resistors are 17W types so theoratically no danger.
But I would have not expected the Rs getting that hot with that underrated load.

My concern when changing to CLC (getting rid of the Rs) is that the voltage would be at 32 to 33 V then which might be too high (see my post last page).
So the reason for having those Rs is dropping the voltage rather than filtering in my case.

Regards
Stefan


17 W = no problem then !

As i said earlier, 30 - 35 VDC is no problem for this build. You should go for bigger capacity and also if it's possible a bigger choke ( 100 mH ~ 2 H ). If you can't afford it make some yourself of scrap. I've made my own, which can be done by converting old transformers to chokes. viewtopic.php?f=5&t=5018


Last edited by KrammeAcoustics on 10 Dec 2014, 17:30, edited 2 times in total.

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 Post subject: Re: MCA - Son of ZCA
PostPosted: 10 Dec 2014, 17:27 
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Joined: 31 Dec 2008, 15:34
Posts: 441
max130 wrote:
Yes, I do like to Play around with the Input and Output caps also.
The SCR in parallel with the electrolytic ones works fine with the ZCA. I will try the Output caps only with the MCA.

For Input caps i have the choice of orange Drops, Wima, Roederstein and SoZo mustard caps. I will have a listen to all of them ;)

regards
Stefan


I will wait for your results 8-)


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 11 Dec 2014, 12:50 
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Joined: 09 Apr 2013, 02:59
Posts: 48
Location: Germany
Kramme
you were right with removing the SCR poly caps at the output, heights are sounding the right amount less aggresive.
Still very detailed and fast.
I will stay with this setup a while to get familiar with the sound and then I will start with chosing the input caps.

It was the right decision to start with the MCA, it's pleasure to explore :)

Regards

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 Post subject: Re: MCA - Son of ZCA
PostPosted: 11 Dec 2014, 13:16 
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Joined: 31 Dec 2008, 15:34
Posts: 441
max130 wrote:
Kramme
you were right with removing the SCR poly caps at the output, heights are sounding the right amount less aggresive.
Still very detailed and fast.
I will stay with this setup a while to get familiar with the sound and then I will start with chosing the input caps.

It was the right decision to start with the MCA, it's pleasure to explore :)

Regards


Hi max130

It's weird because it's normally known as a benefit with poly capacitor around an electrolytic capacitor in a PS. But when it comes to output on an amplifier, in some situations it seems problematic with aggresive, hiss and distorted sound ( these bipolar poly's and the electrolytics must disturb eachother in some way ). Anyway, nice to hear about your improvement. :thumbsup:

Then it's just the PS you have to upgrade
don't you have an old damaged amplifier or some other electronic where you can take some good electrolytics from ? or even better a diy choke from a transformer.

I've made some test now and i'm actually able to make a ripplefree CLC PS, with only 2 x 4700 uF - 2H choke - 2 x 4700 uF. Amazing what difference a good heavy choke can do ! :wizard:

2H choke = 5 V voltagedrop


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 11 Dec 2014, 18:10 
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Joined: 06 Jun 2008, 18:23
Posts: 5151
Location: Australia
Glad to hear you like the MCA. The MCA and ZCA were always meant to have choked PSs. It's part of the Sound and not just there for filtering. Also I always snubbers my large output caps for better HF response.

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 Post subject: Re: MCA - Son of ZCA
PostPosted: 14 Jan 2015, 08:26 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
While listening to my super expensive DIY 300B amp and reading through the previous posts, I have come up with some sousins of MCA.

Lookout for a prototype.

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 Post subject: Re: MCA - Son of ZCA
PostPosted: 14 Jan 2015, 08:29 
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Location: Australia
So what should we call them; Cousins of Minimal Coponent Amplifiers-CMCA?

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 Post subject: Re: MCA - Son of ZCA
PostPosted: 22 Feb 2015, 18:25 
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Joined: 20 Feb 2015, 21:22
Posts: 21
Location: Central Scotland, UK
gyrene wrote:
checked the gate of 170 to ground 1.5 volts
checked the source of 170 to ground 1.5
checked the drain of 170 to ground 12.0 volts

so did i blow the 2n3055?
something is hooked up incorrectly?
ground?

do these numbers mean anything to the coherent?
any help?


Did you ever get your amp working gyrene, you seem to have dropped of the radar? Shouldn't the source of the jfet be at a lower voltage than the gate? Maybe the jfet is faulty.

I'm very interested in this design, though will probably try the ZCA first as I've bought the 2sk1058 and a big heatsink for that, got a used heatsink on eBay for a great price. :D

@Mark Houston, some questions re the ZCA and the MCA:

power supplies; Is there any argument against using a linear regulated supply, over the suggested CLC arrangement, as I will be powering from a bench PSU during the prototyping stage?

Would Wima MKP10's be a good choice for input coupling capacitors? I also have some of those orange Phillips caps. Also would a j201 or a 2n3819 be a good choice for the jfet in the MCA?


I plan on trying out various options in prototype form before committing to a permanent build.

Any help would be greatly appreciated. :idea:


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 Post subject: Re: MCA - Son of ZCA
PostPosted: 23 Feb 2015, 12:38 
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Joined: 06 Jun 2008, 18:23
Posts: 5151
Location: Australia
gasboss775 wrote:
gyrene wrote:
checked the gate of 170 to ground 1.5 volts
checked the source of 170 to ground 1.5
checked the drain of 170 to ground 12.0 volts

so did i blow the 2n3055?
something is hooked up incorrectly?
ground?

do these numbers mean anything to the coherent?
any help?


Did you ever get your amp working gyrene, you seem to have dropped of the radar? Shouldn't the source of the jfet be at a lower voltage than the gate? Maybe the jfet is faulty.

I'm very interested in this design, though will probably try the ZCA first as I've bought the 2sk1058 and a big heatsink for that, got a used heatsink on eBay for a great price. :D

@Mark Houston, some questions re the ZCA and the MCA:

power supplies; Is there any argument against using a linear regulated supply, over the suggested CLC arrangement, as I will be powering from a bench PSU during the prototyping stage?

Would Wima MKP10's be a good choice for input coupling capacitors? I also have some of those orange Phillips caps. Also would a j201 or a 2n3819 be a good choice for the jfet in the MCA?


I plan on trying out various options in prototype form before committing to a permanent build.

Any help would be greatly appreciated. :idea:

The bench PS should be fine for testing but part of the secret of the sound of this amp is the choked PS. Not many SS amps have a choked PS. From the original MCA I chnaged the input cap to 0.1uf for some great improvements. Any poly cap will do just use 0.1uf. Not sure about your jFETs??

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