Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Quicksand => Topic started by: aleman on October 12, 2014, 10:49:19 PM

Title: Quicksand That Sinking Feeling
Post by: aleman on October 12, 2014, 10:49:19 PM
My Quicksand finally arrived  decided to build mine modified from the outset and change some the components to my favourites. as you will see from the pictures,as bottlehead design good circuits from the outset dent straight for the modifications. Sound quality is very good treble light and airy with good definition  bass solid tuneful informative midrange detailed balanced and even handed the sound of this little amplifier is extremely good.,i do use fostex 206e in a solo206 horn cabinets and have done so for at least ten yearswith these speakers there is a little too much midrange emphasis the quicksand seems to have tamed this somewhat resulting in a lovely listen .Imuzt temper these observations as the components will have to break in especially the Russian Teflon bypass caps and the wima poly props capacitors I have used also the battery pack has not been used as prefer to use  car or sla battery as well as trichord  never connected power supply .Anyway that's all for now going to listen to some more music.again thanks to the bottlehead crew for bringing fantastic gear to the impoverished among us .
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 13, 2014, 07:17:38 AM
There are some reasons for the capacitor choices on the Quicksand PCB, especially C5/C6.  Did you listen to the Wimas vs. the Tantalum caps? 
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 13, 2014, 08:26:34 AM
Iam not an engineer I go with what I have used before if it does not breach  any trade secrets could please enlighten me as to why they were preferred  so that I may learn for future reference . the amp still sounds very good to my ears I must confess I did not listen prior to installing the caps.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 13, 2014, 04:42:10 PM
The datasheet for the chip itself calls for a tantalum or ceramic cap for C5, and that would be the one place where I wouldn't mess around too much.  Other selections may or may not lead to a noisier amplifier with additional distortion that wouldn't otherwise be there.

The other recommendations in the application sheet tend to make some assumptions (in my opinion at least) that the power supply available is marginal, so experiments with the power supply caps dotting the PCB should be harmless and fun to experiment with.  The cap at C5 functions in a more isolated fashion with respect to the power supply, so I deferred to TI's recommendations in its selection. 

Another thing you could try is making C2/C8 much, much larger, or considerably smaller.

-PB
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 13, 2014, 11:47:12 PM
Thanks for the reply I suppose I should google the chip and specs and have a good read ,changing the caps value of c2 /c8 what would the effects be I had considered some sanyo oscons low esr types however the voltages seem to be limited any advice on the lowest voltages for c2/c8 I could get away with as well as upper and lower values as guidance .look forward to your reply.
Title: Re: Quicksand That Sinking Feeling
Post by: Natural Sound on October 14, 2014, 04:55:13 AM
I know that to some of you this is beating a dead horse but... It is recommended to build these kits with the supplied parts first. Listen for a while to get a baseline and then experiment away. The only other thing to add would be to only make one change at a time. If you change a bunch of parts at once and something goes wrong you won't know where to start troubleshooting. I know from years of experience that some "upgrades" make things worse. Always start with a stock build first.
Title: Re: Quicksand That Sinking Feeling
Post by: mcandmar on October 14, 2014, 05:37:00 AM
For reasons i don't fully understand ceramic/tantalum caps are far better at decoupling high frequencys then poly caps so personally i would leave those ones alone.  The electrolytics i would change for Wimas, assuming those are MKP series and not MKS.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 14, 2014, 05:45:24 AM
any advice on the lowest voltages for c2/c8 I could get away with as well as upper and lower values as guidance

I wouldn't go below 20V.  For C2/C8, try 100uF caps, then maybe 10,000uF.

-PB
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 14, 2014, 09:14:14 AM
This is a truly fascinating hobby and one will always learn something new will take on board what has been discussed withn regard to the cap choices despite all that the amplifier sounds very good thanks for the advice.
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 15, 2014, 12:01:15 PM
C5 replaced with original ceramic capacitor sat with wife to listen amplifier sounded in my wifes word oh very nice fronted of course by the unmodified quickie  preamp looks like TI were right  have changed nothing else further listening required, also to allow the components to run in.Have acquired some lowther dx3 drive units refurbished with receipt's for work done would like to use with this amplifier but due to switch on thump unlikely to use unless anyone has any suggestions for getting around this problem.Advice appreciated.thanks
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 15, 2014, 12:21:01 PM
Is the thump actually louder than the music played through the amp?
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 15, 2014, 12:45:09 PM
The switch on thump is loud thus  I would fear using lowthers with this amp which is a shame .
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 15, 2014, 05:43:20 PM
But is it louder than something like a large drum playing through your system? 

If it's a ton louder, then you can just pop off the speaker connections while you switch the amp on.  If the thump is consistent with loud transients in the source material you listen to, there's nothing to worry about. 

If you had super high efficiency horns and wanted to run the Quicksand directly to the horn with no blocking cap, that would be the kind of situation where the turn on thump could cause a problem.
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 16, 2014, 03:46:26 AM
I aim wondering if putting a switch in the positive  line of the cables going to the speakers then switching them on after preamp and. quicksand would work .any advice  appreciated.thanks
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 16, 2014, 07:25:06 AM
It's probably easiest to have a switch that shorts the + outputs of the Quicksand to ground.  (No harm done)

That way, once the Quicksand is on, you can open the switch and let it play, and the switch will be out of the signal path.

-PB
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 16, 2014, 08:57:38 AM
Would it be possible for you to sketch a quick diagram for the technically challenged to implement this as this looks like an ideal solution to my particular problem with regard to using my lowther drivers all I will have to do now is find a suitable small horn cabinets to build as space is limited any pointers would be useful. thanks a lot
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 16, 2014, 12:02:06 PM
Here's a quick and dirty set of instructions for you.  When the toggle lever is away from A, B, C, and D, the mute will be active. 
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 20, 2014, 12:51:58 AM
Thanks a lot will try this out later this week as trying to get some info on cabinet for this pair of lowther dx3 drivers I have acquired.
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 21, 2014, 11:55:11 AM
Have to admit unable to fathom out how to wire this into the quicksand amplifier. Therefore aim stuck step by step instructions would be helpful.thanks a lot.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 21, 2014, 05:27:28 PM
Have to admit unable to fathom out how to wire this into the quicksand amplifier. Therefore aim stuck step by step instructions would be helpful.thanks a lot.

Run a wire from left positive speaker terminal to terminal A on the switch.

Run a wire from right positive speaker terminal to terminal B on the switch.

Run a wire from one of the negative speaker terminals to C and D on the switch.

-PB
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 22, 2014, 04:58:49 AM
Thanks a lot saved my blushes will implement this as soon as possible.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 22, 2014, 08:21:27 AM
I forgot the most important step - drill a 1/4" hole in the chassis plate.

To do this, you must have a piece of scrap wood behind the plate where you will be drilling, or the plate will crack. 

It will also go a lot better if you have a bit for drilling plastics, but I use the higher grade of acrylic for these plates (cast), so machining is not as dicey as it could be.

-PB
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 22, 2014, 09:59:32 AM
Thanks for your help implemented as instructed including the hole in top plate works just fine my fostex speakers  now do not jump out of their baskets when being switched on  such a simple thing overthought it thus my difficulties glad I asked for help as would  still be pondering how to implement this. Will post  a picture when phone has recharged to show in in situ .Again my thanks .
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 23, 2014, 07:33:51 AM
As promised pictures of mute switch and reinstalled c5 capacitor amplifier works like a charm sounding better each day .thanks a lot.
Title: Re: Quicksand That Sinking Feeling
Post by: aragorn723 on October 24, 2014, 03:30:09 PM
Hi,

Out of curiosity, how do you power the quicksand?  I see the power jack between the speaker outputs. 

Dave
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 25, 2014, 02:11:33 PM
Oh, yeah, I didn't notice that.

If you're going to power the  Quicksand from a wall wart or other switching supply, capacitor selection on the PC board will be critical in more locations.

-PB
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 26, 2014, 07:31:26 AM
Sorry for the late reply ,been away from the computer the power supply comprises of a car battery 12 volt dc 68 amps or  9 volt dc   never connected supply in stand alone box from trichord research this was originally to power  the trichord clock3 on my teac t1 transport  now unused but still in fine fettle. Thus  I decided to use a separate socket for attaching power cord to the quicksand.not actually using any wall wart or switching supplies albeit that I have a few   belonging to variouse Beresford dacs in my possession but the dac is also dc from a 12 volt dc car battery.one thing of note powered up briefly with lowther dx3 attached still loud thump  disconnected lowthers fostex  206e woked fine ,connected lowthers to my ladyday 300b amplifiers with quickie preamp and source speakers fine no switch on thump puzzled but as lowthers  very expensive no further experiments with quicksand for now until I can ascertain the problem when using the lowthers but with fostex 206e sound very good .will have to suck it and see any suggestions appreciated.
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 26, 2014, 07:46:43 AM
Ps forgot to add  I have ordered from china a 30 volt  dc analogue meter to check batteries a bit like the finial amps of yore. will post pictures when I have fitted it as coming from china this may take some time.
Title: Re: Quicksand That Sinking Feeling
Post by: 2wo on October 26, 2014, 07:52:51 AM
I thought you had added a shorting switch to the outputs? With that closed, there should be no start up thump...John 
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 27, 2014, 05:34:23 AM
All problems sorted with lowthers reconnected the lowthers in the early hours followed the exact order of switching on source quickie and quicksand with mute switch on left  15 seconds approx. very low plop sound through with mute switch on nothing to trouble the lowthers or any other speaker after which came forth music bearing in mind  lowthers no boxes sounded not to bad.lowthers put away until I can decide which horns to build mute switch fine therefore the error must be mine ,inadvertently pushed switch in wrong order.thanks for all the help quicksand working as it should mute switch and all.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 27, 2014, 08:47:17 AM
Ah, yes, I could imagine that the turn on thump would be a bit more troubling if the driver wasn't mounted into any kind of enclosure.
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 29, 2014, 12:23:15 PM
Have completed all I wanted to do to the the quicksand now the volt meter has arrived fitted today fairly straight forward but no template .Works  as it should  will rebuild quickie preamp next year to incorporate these meters as an indicator of batteries running out.Now back to the music.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on October 29, 2014, 05:15:52 PM
That's pretty cool!  You'll end up having the most analog looking digital amp out there.
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 30, 2014, 12:50:34 AM
Must admit had not given any thought to that aspect of things.The amplifier continues to improve I cannot believe the sound quality for the money superb ,from what I have read the parts to burn in last will be the Russian Teflon bypass caps I have used so the sound may change again slightly over time  must have about  80 hrs on the amplifier so I will see.
Title: Re: Quicksand That Sinking Feeling
Post by: aragorn723 on October 30, 2014, 10:40:31 AM
Hi,

Someone might have asked this already, but what kind of wire did you use?  Also, where did the voltage meter come from?

Dave
Title: Re: Quicksand That Sinking Feeling
Post by: aleman on October 31, 2014, 02:49:47 AM
Wire used is 0.5mm pure silver as had some spare on a reel from about 10 years  wire with Teflon insulation Teflon used as does not melt so readily when in contact with soldering iron,there is some debate as to which insulation to use but I find this works for me a now middle aged and hands not as steady as once were . The meter was from this seller on ebay sellerbible price was around £3.21p cheap and works well given coming from china delivery was quicker than expected.Hope this helps also  there other sellers on ebay selling these analogue meters if hey should run out of stock.
Title: Re: Quicksand That Sinking Feeling
Post by: badman on December 15, 2014, 10:21:17 AM
Does the chip mute when shorted on the output?  I saw nothing in the application notes to indicate this as a recommended mute function, in fact, there's a 0-2v mute logic pin included for that purpose, and it's generally poor practice to short output terminals, though being chip based it may simply enter protect mode- I just want to confirm before I drill in my switch hole for the build.

Thanks.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on December 15, 2014, 10:29:14 AM
No, the shorted output is just to soak up the turn-on transient.  If you left the outputs shorted (and played music through the amp for a long time), the chip may enter protect mode.  With no signal going into the amp, it will not see the short at the output.
Title: Re: Quicksand That Sinking Feeling
Post by: Grainger49 on December 15, 2014, 12:17:01 PM
"You never close your eyes any more when I kiss your lips.... You've got that sinking feeling.... That Quicksand sinking feeling."

Couldn't help it.

Title: Re: Quicksand That Sinking Feeling
Post by: badman on December 15, 2014, 04:15:04 PM
No, the shorted output is just to soak up the turn-on transient.  If you left the outputs shorted (and played music through the amp for a long time), the chip may enter protect mode.  With no signal going into the amp, it will not see the short at the output.

OK, I guess proof in the pudding, I was just wondering, as switching residual or other fun goodies could be an issue in some class D designs with a shorted output.  I'll throw an extra switch back there in any case.
Title: Re: Quicksand That Sinking Feeling
Post by: Paul Birkeland on December 16, 2014, 10:56:29 AM
You could also "short" the amp with a pair of 1 Ohm 1W resistors.  The turn on thump will be absorbed well by them, but playing a lot of music into them would open them up.