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Reviews Categories | Filters, Audio: (DSP and others) | Mizuho AP-1D Audio Processor Help

Reviews Summary for Mizuho AP-1D Audio Processor
Mizuho AP-1D Audio Processor Reviews: 1 Average rating: 5.0/5 MSRP: $99.50 in 1983
Description: Analog audio filter with notch, peak, and bandpass filters
Product is in production.
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KU4QD Rating: 5/5 Apr 22, 2003 14:26 Send this review to a friend
Compares favorable with Autek and Datong filters. Very nice.  Time owned: 3 to 6 months
The Mizuho AP-1D audio filter is a 1980s vintage analog filter which was meant to compete with such products as the Autek QF-1A. It is, without question, one of the best of the older audio filters out there. No, it doesn't compare with a modern DSP unit like a JPS NIR-12, and it does no noise reduction. It also has no digital products which produce some pretty annoying sound common in DSP units when you try and process heavily.

The AP-1D has three filter functions. The notch filter can be adjusted both for frequency and for "Notch Dip", or the depth of the notch. The peak filter is also adjustable. The narrow bandpass filter is not adjustable, but workes very well both on CW and SSB. It makes a great extra narrow SSB filter for older rigs that just don't have one. I've found it particularly good when working SSB stations between the broadcasters on 40m at night using my '80s vintage NCG 7/21/50 QRP rig.

I've found the notch filter to be as effective or more effective than the ones built into some newer (but still pre-DSP) radios. The peak filter is just too narrow for SSB but is absolutely brilliant on CW. I've already complimented the bandpass filter.

One really nice touch on the Mizuho AP-1D is the fact that it has dual inputs, so you can connect it to two radios and switch between them at the flip of a switch. The output is two terminal screws, so you can use the Mizuho filter with a single stereo speaker or most ham speakers.

I use this filter regularly (as in almost every day) with my vintage QRP gear, both NCG and Mizuho. I've used both Autek and Datong filters in the past, and the Mizuho compares favorably to both. The AP-1D was sold in the US by Ace Communications for at least a short while, but they seem to be fairly rare here. I picked mine up for a rather small price on eBay. I think most hams just don't know these so they don't hold their value like an Autek filter.

If you have modern DSP equipment or a very good DSP unit you don't need an AP-1D. If you prefer an analog audio filter and are using vintage equipment the AP-1D is about the best out there.

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