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MCA SP1 Mod/upgrade PICS!
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Mustang Martigan
audio school graduate


Joined: 08 Jan 2017
Posts: 22
Location: BOSTON, MA

PostPosted: Fri Apr 07, 2017 11:45 am    Post subject: Re: MCA SP1 Mod/upgrade PICS! Reply with quote

Jim Williams wrote:
I have found no salvation for the MCA SP-1 capsule, it's that bad. Replace it and you too will understand.


Ya, I 100% understand that the stock capsule is beyond saving, and that it NEEDS to be replaced to get the real benefits from any SP1 mod.
My question is if it's still worth the trouble of preforming the mod, since I already bought the three replacement caps, C3, C4 and C13, for my pair (of SP1's).
I remember you mentioning that the SP1 can become harsher than it's stock tone when upgrading the circuit, and leaving the stock capsule in place. From all the reviews I've listen here, and read elsewhere, this small mod seems like it'd only have a positive impact.

Thanks,
Adam
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Mustang Martigan
audio school graduate


Joined: 08 Jan 2017
Posts: 22
Location: BOSTON, MA

PostPosted: Mon May 15, 2017 6:24 am    Post subject: Re: MCA SP1 Mod/upgrade PICS! Reply with quote

Jim Williams wrote:
I have found no salvation for the MCA SP-1 capsule, it's that bad. Replace it and you too will understand.


I was cleaning out my bookmarks and rediscovered this thread. I've been sidetracked with other projects and haven't had a chance to mess around with the SP1. We spoke on another forum recently about replacing the stock capsule with one from Mic-Parts.

Do you think that instead of buying one of the Mic-Parts circuit upgrades, I could get away with just buying a capsule from them and using the 3 capacitor mod mentioned above? I'm assuming Mic-Parts circuit mods are made to work well with their capsules. Also, I'm not sure if the 3 capacitor mod was designed for the stock capsule. Especially since one of the cap replacements is for the capsule.

Does that make sense? I'm not a tech in the least, so I might be making some unintentional assumptions. I just don't have much cash, and if I could get away without having to drop $300 on a pair of new circuits, my landlord would be happy.

Thanks.
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Jim Williams
tinnitus


Joined: 03 Jun 2006
Posts: 1133
Location: beautiful Carlsbad, CA

PostPosted: Mon May 15, 2017 11:43 am    Post subject: Re: MCA SP1 Mod/upgrade PICS! Reply with quote

The polarization voltage in the MCA is around 42 volts, pretty low and not enough to properly charge a 1" diaphram. Those need 60 volts.

The output resistance of 22 ohms is too low to stabilize the output drive transistors. The jfet bias may not be correct for the device.

All of those issues are worked out on the replacement pcb's and design.
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Jim Williams
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Mustang Martigan
audio school graduate


Joined: 08 Jan 2017
Posts: 22
Location: BOSTON, MA

PostPosted: Sun May 28, 2017 6:16 pm    Post subject: Re: MCA SP1 Mod/upgrade PICS! Reply with quote

Jim Williams wrote:
The polarization voltage in the MCA is around 42 volts, pretty low and not enough to properly charge a 1" diaphram. Those need 60 volts.

The output resistance of 22 ohms is too low to stabilize the output drive transistors. The jfet bias may not be correct for the device.

All of those issues are worked out on the replacement pcb's and design.


Is the 42 volt polarization voltage the stock value? As well as the 22 ohm output resistance?

Do either of the three capacitor upgrades that come the with mod avail on eBay (the one I keep mentioning), fix the two values you just mentioned?

I remember you saying that just changing the circuit and not the capsule can end up making the stock capsule sound worse. Is this also the case with the mode available on eBay, do they actually enhance the sound of the mic (w/o a capsule replacement)?

Here's the link to the eBay auction: http://r.ebay.com/PSs2tL

Thanks,
-Adam
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