DIY Audio Projects Forum

"Lacewood" Amp V2.0
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Author:  john55 [ 04 Sep 2018, 02:02 ]
Post subject:  Re: "Lacewood" Amp V2.0

Quick question.... I've used Log, but which is correct. Lin or Log for bass and treble controls?

Author:  Suncalc [ 04 Sep 2018, 18:25 ]
Post subject:  Re: "Lacewood" Amp V2.0

john55 wrote:
I've used Log, but which is correct. Lin or Log for bass and treble controls?
It depends on the style of tone stack. A Baxandall tone stack requires 'Log B' taper pots (i.e. 10% total resistance at 50% shaft setting) for both the Bass and Treble controls.

Author:  Woodo [ 16 Oct 2018, 17:37 ]
Post subject:  Re: "Lacewood" Amp V2.0

Slightly off topic but worth a mention. In my neck of the woods Brisbane Aust it's been a good year for the flowering of a number of trees but in particular I don't remember seeing so many flowers on the Silky Oaks. i understand it's one of a number of trees whose timber has the characteristic lacewood pattern. The pic probably doesn't do it justice but quite pretty nonetheless.

Author:  john55 [ 08 Nov 2018, 06:52 ]
Post subject:  Re: "Lacewood" Amp V2.0

I first built the Lacewood V.2 15 months ago. I rehoused it 3 months ago. In both builds I used a stepped attenuator bought from China. It looks beautiful. Surface mount resistors and a good, not too stiff mechanical action. During the last week I've been listening to ever increasing noise on the system, so today I swapped it out for an Alps Blue Velvet which I've used in my other builds. Instant success. Everything sounding good again. I'm not sure if the surface mount resistors are breaking down or the contacts are corroding. Whatever the problem, it goes to show that something has to give when spending €30.00 when every other attenuator I had found was in the €100.00+ price range. Or was I just unlucky.
Has anyone else had problems with cheap attenuators?

Author:  mwhouston [ 08 Nov 2018, 16:33 ]
Post subject:  Re: "Lacewood" Amp V2.0

Ive used a few from EIZZ, 100K and 250K and never had a problem. About $80. Thier shafts are isolated. I've now bought the premium version, a lot more expensive. We'll see how that goes.

Author:  harrydutt [ 09 Nov 2018, 17:04 ]
Post subject:  Re: "Lacewood" Amp V2.0

I've been using Alps Blue Velvet pots for years now and never had a problem. I enjoy my music with these pots in my amps.
I don't care to buy expensive pots so I wouldn't know whether an expensive pot will help me enjoy my music more.

Author:  mwhouston [ 09 Nov 2018, 17:11 ]
Post subject:  Re: "Lacewood" Amp V2.0

The steppers are something I just tried and liked. I don't use them in all my builds but lately most. I used them in my Grace preamp and now builder a more expensive version thought I'd go for the ore expensive stepper. Only two resistors on cct. at any one time. So should be low noise.

Author:  laurie54 [ 09 Nov 2018, 21:00 ]
Post subject:  Re: "Lacewood" Amp V2.0

The fact is every pot made will eventually fail due to mechanical usage. In the case of regular single turn pots if they come from a reputable company that specializes in manufacturing pots as one of their products you would get a product that would be sure to last many years before going bad. They are a carbon track which is tapped at some point along it's length by way of a piece of metal sliding on the surface of the carbon as the shaft is rotated. The thickness of the carbon trace, the metal used for the wiper, the type and amount of grease used to lubricate and protect the metal from oxidation, and the amount of pressure the wiper has on the carbon track are all factors leading to why the pot might fail. The humidity factor in the area one lives is another factor in the longevity of a pot. The drier the area the longer it will not suffer from oxidation but may suffer more from electrolysis. Having said that I live in a rain forest and have open case pots bought for a dollar which are as good as the day i bought them. I also have a top of the line hermetically sealed pot from Bourns which was so bad out of the package I could not use it for anything. The manufacturing of multi ganged pots is not precise enough to guarantee both pots will give the same value when set at the same position by the shaft's rotation. They are for the most part very close but we audiophiles are a fussy bunch. Enough years have passed by now there are proven products from known companies which can be relied upon to give decent results such as the blue velvet etc.

A rotary switch with hard wired resistors from position to position will give a more accurate reading at any given position as the res can be 1% or even 0.1% tolerance. Thereby providing set points of 1, 2, or 3db steps in volume per position and ensuring each "pot" connected by the shaft will be within same tolerance of all of the other gangsw's on the same shaft. The theory and practice is sound, however even though a rotatory switch can have close tolerance res on it there is still the moving metal wipers making connection between each position. They will be better IMO than a standard pot as the mechanical link is between metal to metal rather than metal to carbon trace and therefore be more robust in mechanical longevity. But these rotary switches are still subject to mechanical wear, corrosion, oxidization, and electrolysis at the contact points.
Back in the day, a 23 position rotary switch was 2" to 3" in diameter making their usage subject to the available space for a device that size. Many still are but now days with comp precision and SMD parts the same can be much smaller in diameter but the market place is still one of buyer be ware and informed. You could luck out but in general we still get what we pay for. That is one of the best aspects of this form, the wisdom of age and experience.

Author:  laurie54 [ 09 Nov 2018, 23:05 ]
Post subject:  Re: "Lacewood" Amp V2.0

So in short. I see the majority using Blue Velvet for a reason. They are not cheep but saving to purchase one is worth
the investment especially when building one's own piece. That is not to say lower priced pots wouldn't all stand up as well.

For the more refined pots using rotary switching I look to people who have used them, as a measure of which to purchase.
Mark builds amps like my gram made bread and it's wonderful to see. It's good to know the end result of turning from one
position to the next is smooth. The refining and mixing of various metals, the ability to work more freely at a microscopic
level to shape and contour the mating contact surfaces to ensure a strong positive connection at each position and less
friction between steps is nice. Also worth mentioning is that rotary switches have two contact surfaces with the moving
wiper were as the carbon pots have only one.

Suncalc solved that problem using a massive knob on the front. He didn't have to even put
the word volume on it. Screams I am control central.

Then again how many high end amps DIY and commercial have two independent volume controls. Just try and match
4.67Kohm and 4.67Kohm using two knobs 6" apart with with no markings other than the words Left and Right.
How many people have left and right ears that hear with 100% equal amplitude, equalization of the frequencies due
to differing shaped ears, head, bone structure, body mass, intoxication level, and current music genera being played
at current location.

I'll shut up now and back to my coding.

Author:  lowhifi [ 16 Nov 2018, 01:41 ]
Post subject:  Re: "Lacewood" Amp V2.0

I will like to build the Electra-Print audio 45 amp using the power supply of the Lacewood 2.0
Any worries.

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