Akitika PR101 Preamp by Dan Joffe

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I built it. To me, it was my "preamp dream come true". Remote control, lots of inputs, tone controls with defeat, two channels only. No nonsense design. I did not get the optional phono input.

Very, very quiet and musical and great value for the money as well. A "engineer's preamp" IMHO.
 
dual op amps

Yes I've built it...it sounds great...phono preamp, too! But then, I'm biased...I'm the designer!

I got a couple of questions:
1. why did you use dual opamps rather than single ones (eg LME49710) and dual mono approach? Cost increase would be small and probably meaningless for users as when building diy preamps the most important part is the case - especially front and back panels.

2 Why not regulated PS allowing users to choose preferred voltage? I like to run op-amps close to their limit. LMEs run very well on +/-17V.

When it comes to the front panel I'd spread pots a bit more and I'd use a bigger volume pot knob, while the other three would be of the same size as your current volume and balance knobs. Face plate would look a bit more balanced but that is largely cosmetics.

cheers,
 
Great questions...I'm honored that you've taken the time to look it over so carefully!

In meeting a price and complexity point, everything involves trade-offs and compromises. Dual opamps versus singles saves some space. The only compromise is a bit of left-right crosstalk. Going to dual mono would unfortunately increase the cost a bunch. It's amazing how quickly it adds up, and how a little change can have large ripple effects!

Preferred voltage? It all comes back to those pesky compromises. If the output voltage were high enough to allow 15 volt or 17 volt rails, we'd need more raw output, then a bigger power transformer, and probably bigger heatsinks, and the cascade of cost continues. Now, having said that, there's probably enough extra room that you could swap the 12 volt regulators for 15 volt regulators...but probably not enough to go higher. Of course, you could opt for a switcher, but the noise is hard to deal with.

As to the front panel layout...more of those compromises! I agree that the spread out pots would probably look better, but it wouldn't leave as much room for option cards, or it would make it much harder to poke around and trouble-shoot the preamp, or add other enhancements.

So...in some cases, I think we have the same priorities...low distortion, quiet circuits, very low crosstalk between inputs...and perhaps some of the details of the choices are a bit different...

Thanks for taking the time to review things give me the feedback...

All the best...

Dan
 
Great questions...I'm honored that you've taken the time to look it over so carefully!

In meeting a price and complexity point, everything involves trade-offs and compromises. Dual opamps versus singles saves some space. The only compromise is a bit of left-right crosstalk. Going to dual mono would unfortunately increase the cost a bunch. It's amazing how quickly it adds up, and how a little change can have large ripple effects!

Preferred voltage? It all comes back to those pesky compromises. If the output voltage were high enough to allow 15 volt or 17 volt rails, we'd need more raw output, then a bigger power transformer, and probably bigger heatsinks, and the cascade of cost continues. Now, having said that, there's probably enough extra room that you could swap the 12 volt regulators for 15 volt regulators...but probably not enough to go higher. Of course, you could opt for a switcher, but the noise is hard to deal with.

As to the front panel layout...more of those compromises! I agree that the spread out pots would probably look better, but it wouldn't leave as much room for option cards, or it would make it much harder to poke around and trouble-shoot the preamp, or add other enhancements.

So...in some cases, I think we have the same priorities...low distortion, quiet circuits, very low crosstalk between inputs...and perhaps some of the details of the choices are a bit different...

Thanks for taking the time to review things give me the feedback...

All the best...

Dan

Thanks Dan for your explanations.

Looking at the preamp kit from an economic perspective (I'm economist plus...) it seems to me that you took exactly the same approach as most kit makers. But there is an alternative. Offer at least three options.

The first one is to offer the full kit as you have it;
the second one is just the case plus bare boards with pots, switches, motors and other essentials specific to your project;
the third option allows the customer to choose a mixture of modules (boards with parts) and bare boards. There would be no problem to have a regulated PS board rather that the fixed voltage one. Douglas Self used to offer such options on his projects.

If you followed the "options path" you could even allow for one more option, namely a choice of dual mono or dual opamp versions (minimum space option you have at the moment).

Taking that path might attract more customers as the case plus boards and essential items would be much cheaper to them and you would make more money if more were attracted. If not still you would not miss a cent.

In a way it would be sort of minimum marginal cost version to them as most DIY guys have boxes of goodies from which they choose what they need. They bought these parts on various specials or bought larger quantities minimizing item price knowing that they will be building more amps or whatever in the future. On top of it, transformer adds to shipping costs, especially for overseas customers.

As I said before, the case (front and back panels) is the most important part when one builds a preamp for obvious reasons. If you make it both attractive and cheap (the whole work is finding some optimum compromise) you will maximize your sales and profits.

As as a fifth option you could offer just a nice case.

My personal choice would be a nice case, boards plus essentials (pots, switches, motors and possibly input selector and controller modules with gold plated sockets).

As there is enough space on your back plate to accommodate another
pair of output sockets I'd add these to run separately my sub and the main system.

cheers,
 
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Dan, he must not have read your answer very closely. I look forward to building one of these soon to go with my hand built White Oak Phase Linear 700 Series II Clair Bros special. I scored some of these amps and have been building them for some of my friends. Been looking for a preamp I can put together to go with it. Maybe I'll offer them as a "Pair".
 

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Hmm so I've been casually on the lookout for a good preamp to go with my MyRef RevC amp I built several years back (9 years ago! holy crap where is the time going?!).

This PR-101 looks like a winner. When I look at the GT-102 it reminds me a lot of the Mauro Penesa LM3886 designs. Is it similar? Just wondering if it's worth considering the GT-102 also if I've already got a MyRef RevC?
 
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