Thanks Greg I don't have permission to message you at this stage apparently.Can i send my email address?or perhaps you PM me. Thanks again.
Greg,
I'm an owner of an Apt Holman preamp. I bought it used in 1982 and have had it reworked in the last year. I also have an MC board for it, but its Molex connector is broken - brass connectors not applying any spring force against the pins of the motherboard. I'm interested in one of your boards, too. Can you tell me more about it and if I might buy one from you? I'm new to diyAudio, so I'm not sure what I'm allowed to do with respect to messaging.
In case this is a 'build-your-own-board' situation: I have an engineering background, but my odds of building a MC preamp well on the first try or so are small. I have created my own circuit boards of less complicated circuits successfully.
Thanks,
Dave
I'm an owner of an Apt Holman preamp. I bought it used in 1982 and have had it reworked in the last year. I also have an MC board for it, but its Molex connector is broken - brass connectors not applying any spring force against the pins of the motherboard. I'm interested in one of your boards, too. Can you tell me more about it and if I might buy one from you? I'm new to diyAudio, so I'm not sure what I'm allowed to do with respect to messaging.
In case this is a 'build-your-own-board' situation: I have an engineering background, but my odds of building a MC preamp well on the first try or so are small. I have created my own circuit boards of less complicated circuits successfully.
Thanks,
Dave
Hello, Dave,
At this point, I'm not sure this is a viable project. Sean has been dealing with health issues, and I've yet had time to verify the parts in the BOM are all still available.
Your best bet might be to build an external MC head amp or use an SUT and feed that into the Apt MM circuit, or get an MM/MC RIAA phono preamp and plug it into one of the AUX inputs.
Cheers,
Greg
At this point, I'm not sure this is a viable project. Sean has been dealing with health issues, and I've yet had time to verify the parts in the BOM are all still available.
Your best bet might be to build an external MC head amp or use an SUT and feed that into the Apt MM circuit, or get an MM/MC RIAA phono preamp and plug it into one of the AUX inputs.
Cheers,
Greg
Thank you Greg for your response. I hope Sean fells better soon.
I'll assume this is not a viable way to go for now. If, however, I can be of help in resurrecting the project I would be willing. Please feel free to contact me.
Regards,
Dave
I'll assume this is not a viable way to go for now. If, however, I can be of help in resurrecting the project I would be willing. Please feel free to contact me.
Regards,
Dave
Dave, Greg, Moe:
The boards are still available at OSHPark:
https://oshpark.com/shared_projects/WRZMphUH
... or you can send the gerber files off to China for a little less cost.
All original parts are still available at Mouser, but it's not necessary to use the exact same parts I did. I've included a couple of BOMs with current pricing in the download (one w/premium parts, one w/more reasonable parts), but feel free to use whatever brand/model of parts you prefer, it's not critical, as long as values/voltages/tolerances etc. are the same.
Files are too big to attach here, so download at:
https://www.nulltime.com/DIYAudio/Apt/MCv2/Apt_MC-v2_files.zip
The boards are still available at OSHPark:
https://oshpark.com/shared_projects/WRZMphUH
... or you can send the gerber files off to China for a little less cost.
All original parts are still available at Mouser, but it's not necessary to use the exact same parts I did. I've included a couple of BOMs with current pricing in the download (one w/premium parts, one w/more reasonable parts), but feel free to use whatever brand/model of parts you prefer, it's not critical, as long as values/voltages/tolerances etc. are the same.
Files are too big to attach here, so download at:
https://www.nulltime.com/DIYAudio/Apt/MCv2/Apt_MC-v2_files.zip
Hi Sean,
Is there a chance you have the Gerber files for the through-hole version? I am a rudimentary solderer, but surface-mount soldering is a new trick I doubt this old dog can master.
Thanks in advance,
Pete
Is there a chance you have the Gerber files for the through-hole version? I am a rudimentary solderer, but surface-mount soldering is a new trick I doubt this old dog can master.
Thanks in advance,
Pete
Pete
Not a snowballs chance in hell! But let me explain... I NEVER had gerber files to begin with. The PCB fab house I use doesn't need them.
When I got the original boards and realized my omission and error, I immediately set about to correct the schematic and layout, so I don't even have the original files to generate gerbers from anymore. And I set it aside before done in order to concentrate on the v2 SMD board.
If you're REALLY hell-bent on building from scratch, it wouldn't take much to finish the corrected thru-hole layout. Otherwise, I might be willing to part with my original, warts 'n all. It's not being used, just a momento now.
Biggest issue with thru-hole is the need to tap into the main board to get -18v, there's no real convenient place. The specialty regulators to produce dual polarity voltages are all surface mount, so it is what it is.
I've got a couple of other ideas for updated cards, but they also require SMD parts.
Not a snowballs chance in hell! But let me explain... I NEVER had gerber files to begin with. The PCB fab house I use doesn't need them.
When I got the original boards and realized my omission and error, I immediately set about to correct the schematic and layout, so I don't even have the original files to generate gerbers from anymore. And I set it aside before done in order to concentrate on the v2 SMD board.
If you're REALLY hell-bent on building from scratch, it wouldn't take much to finish the corrected thru-hole layout. Otherwise, I might be willing to part with my original, warts 'n all. It's not being used, just a momento now.
Biggest issue with thru-hole is the need to tap into the main board to get -18v, there's no real convenient place. The specialty regulators to produce dual polarity voltages are all surface mount, so it is what it is.
I've got a couple of other ideas for updated cards, but they also require SMD parts.
Sean, thanks for the reply and the explanation. I guess I've either got to get with the times (SMDs are everywhere) or get some help. Or just use an external headamp or transformer for MC.
And thanks for continuing to work with the AptHolman! I had my first one, with amp, in about 1980, including the card for my Dynavector Ruby. Got the bug to get something else, and regretted it, so I've replaced them in recent years, but without the MC card.
One nice thing about the Apt Holman preamp is that it has a very good MM section built-in. As you noted, you can use an SUT, or an MC head amp (though those are not as common these days, so I built my own, again designed by Sean). You can also use a standalone RIAA MC/MM phono preamp, which are much more common as both DIY and commercial products. That could be an even better integrated approach, since that unit would be designed to perform all tasks, and simply plugged into one of your available inputs.
When I am testing my various phono preamps or SUTs, I use the Apt as a test bed by plugging one into every available input, then comparing to our MC card/onboard MM stage. It is very informative.
Another nice thing is that the Apt can be updated to perform better than originally designed and produced.
When I am testing my various phono preamps or SUTs, I use the Apt as a test bed by plugging one into every available input, then comparing to our MC card/onboard MM stage. It is very informative.
Another nice thing is that the Apt can be updated to perform better than originally designed and produced.
Pete:
A snowball survived hell! While rummaging for other parts yesterday, I found a blank 1st version PCB. I thought I had given them all away, my mistake.
So if ya want to build it, it's yours. Or, you can but my prototype (the board pictured in the first post here), for say $50 shipped? (basically cost of 2 AD797 chips).
It ain't pretty with the warts of a prototype, but 100% functional. It could serve you until you find or build a better alternative.
You still using the Dynavector? Board is set up for an Ortofon MC-20 at 34dB gain, but changing a couple of resistors would bring it back to what's needed for the Dynavector.
Sean,
That’s a hardy snowball! Wow, that’s great.
I’d be happy with the prototype, unless you’d prefer me to build up the blank board instead.
The Dynavector is long gone- I’m looking to set up for a Denon DL 103.
Thank you! I appreciate your efforts and thinking of me.
Pete
That’s a hardy snowball! Wow, that’s great.
I’d be happy with the prototype, unless you’d prefer me to build up the blank board instead.
The Dynavector is long gone- I’m looking to set up for a Denon DL 103.
Thank you! I appreciate your efforts and thinking of me.
Pete
for you folks that still have and use your APT preamps, did your volume control ever get noisy? If so, what did you do about it?
I have 3 and one developed a noisy volume control years ago. It is actually a gain control, not a volume attenuator, so when you notice static or scratchy noise using the pot, it is usually the electrolytics drying up, potentially passing DC, or the op amp getting flaky. Using cleaner/lubricant won't solve the problem. If yours has never been serviced/recapped, it is probably time.
Doubt its an opamp getting flaky, more likely to be the choice of a bipolar opamp rather than FET opamp - and routing the opamp's bias current through the wiper contact of the pot. Either use FET opamp or put a capacitor on the wiper and provide a separate path for bias current.