Well, I did a little experiment this morning - that IMO confirms that my new Delrin 'SkeletaLinn' chassis has achieved what I hoped it would. 

 

Mounting the 2 motors on the 'wings' front & back - instead of off-board, on brass motor pods - made the TT easier to set up (and cheaper to make, for any future punters, as brass motor pods don't have to be machined   ).  However, doing this allowed the possibility of motor vibrations getting to the bearing and up into the platter.  I was hoping that Delrin would be sufficiently self-damped to kill any residual vibration that was left over after using the 'Number9' speed controller to optimise the phase difference between the two pairs of motor wires (which minimises motor vibrations) - and this seems to be the case.  

 

I removed the belts from the motors and put a blank LP side on the platter (45rpm sets sometimes have these).

 

Resting the stylus on the blank LP and listening at a normal level - dead silence!  (As it should be.   )

 

Then turning the motors on ... again - dead silence!

 

Andy

 

Edited January 9, 20215 yr by andyr

Well, another update is due.  

 

I had posted under "DIY" that I had been building a pair of Class A amps for over a year ... unfortunately, a wrong initial choice in terms of the layout of the various parts of the amp in the case, caused a problem that delayed me getting to a successful conclusion by several months.  The decision to rearrange the layout was quite expensive - as I had to:

*  order new back panels from Modushop (as the amp PCBs are now mounted on the bottom panel - not the back panel)

*  and get my 'metal man' to cut:

• large slots at the front of the case, either side, to allow the power traffos to be mounted vertically (sinking down into the slots by 10mm, so they didn't foul the top of the case)
• new holes in the bottom panel, for the fans which cool the CPU cooler heatsinks (which the mosfets are bolted to)
• and 4 brackets, to hold the power traffos vertical

As well, it caused me a lot of work - including drilling lots of bolt holes in the new bottom panels.  

 

So this:

 

 

 

became this:

 

 

 

... which solved the problems I had been having.  

 

So I have been happily listening to them for the last few weeks, (driving the mid panels & ribbons of my Maggies).

 

The amps sound better than the NAKSA 80s I had been using before ... but they do have a downside!  Heat!!    (240w of heat for each amp is quite a lot of heatload for the room, on a summer's day.)

 

Andy

 

Andy, tight squeeze for everything!  Which way do the fans cool the heatsinks? Fans under the heatsinks pushing air out through the top cover?

Gotta keep that heat away from other components especially electrolytic caps!

regards Ian

Those CPU coolers look nifty! No fan noise? What brand did you source? Many look like a much cheaper alernative to monster heatsinks that can't dissipate that kind of heat! Maybe in a tunnel configuration your amp could take on double duties in winter!

regards Ian

7 minutes ago, Ian McP said:

Andy, tight squeeze for everything! 

 

Indeedy, Ian!  

 

Quote

Which way do the fans cool the heatsinks? Fans under the heatsinks pushing air out through the top cover?

Gotta keep that heat away from other components especially electrolytic caps!

regards Ian

 

Yes, holes cut into the bottom panel - with the fans positioned on top of these holes and the heatsink fins above the fans.

 

Seems to work quite well - yesterday the room temp was 26 deg ... and the heatsinks measured 47 deg.

 

1 minute ago, Ian McP said:

Those CPU coolers look nifty! No fan noise? What brand did you source? Many look like a much cheaper alernative to monster heatsinks that can't dissipate that kind of heat! Maybe in a tunnel configuration your amp could take on double duties in winter!

regards Ian

 

 

Noctua, slim-line fans.  A bit more noise than I had hoped - but basically not heard at the listening position.

 

Andy

 

Edited April 7, 20214 yr by andyr

Hey Andy 

 

Just reading the thread, whats happening with the Turntable, it's a striped back Linn? With a skeleton plinth someone has made?

 

Whats the idea behind this? Is it sounding as good as the normal Linn?

 

Just thinking I have a Thorens I could apply the same theory to if it works.

Thanks for any advice.

 

Russell

12 minutes ago, russell66 said:

Hey Andy 

 

Just reading the thread, whats happening with the Turntable, it's a striped back Linn? With a skeleton plinth someone has made?

 

Whats the idea behind this? Is it sounding as good as the normal Linn?

 

Just thinking I have a Thorens I could apply the same theory to if it works.

Thanks for any advice.

 

Russell

 

Yes, indeed, Russell - it's a stripped back LP12!    The "idea behind it" was ... I fell in love with a 12" arm which wouldn't fit on my LP12.  So I took the things that are core to an LP12 (the bearing, the springs and belt drive) and came up with something that keeps these core items ... but allows me to have the 12" arm (Duc's Univector).

 

I think ... in its current form - with 2 motors and a 'Number9' motor controller - it's on a par with a top-spec LP12 (ie. Keeled and Radikalised)!  

 

Yes, you could do the same to a sprung Thorens.

 

Andy

 

 

 

Just to update this thread with some pics of my new spkrs (now installed in place of my Maggies):

 

 

 

 

 

 

 

Andy

 

Edited May 20, 20214 yr by andyr

Wow quite the change there Andy. One thing id be acutely aware of in such a radical change as this is that "wall of sound" collapsing into more pinpoint (and perhaps smaller overall presentation) than you would have experienced in the past. Has this been an issue?

 

In addition are you finding seating position more critical than before and that "headlock" effect whereby moving your head slightly collapses the image?

 

That said the new arrangement certainly makes the room look bigger than it did previously. 👍

9 minutes ago, Tubularbells said:

Wow quite the change there Andy. One thing id be acutely aware of in such a radical change as this is that "wall of sound" collapsing into more pinpoint (and perhaps smaller overall presentation) than you would have experienced in the past. Has this been an issue?

 

Thanks.  

 

I'm still getting a 'wall of sound' - with a massive centre-fill ... but, yes, I guess the soundstage is not so tall as the Maggies produced.

 

But the location of individual voices/instruments is sensational ... with what seems to be a more dynamic presentation than before!

 

9 minutes ago, Tubularbells said:

In addition are you finding seating position more critical than before and that "headlock" effect whereby moving your head slightly collapses the image?

 

Not at all, Doug.  I have a 3-seater couch for listeners; because I have the spkrs pointed at my knees when I'm in the central position (not my ears) ... the soundstage is still there when you sit at either end of the couch.

 

9 minutes ago, Tubularbells said:

That said the new arrangement certainly makes the room look bigger than it did previously. 👍

 

It certainly does!    A lot bigger.

 

Andy

 

Andy, 

 

I think it will be interesting to see where you stand with the sound after 6 months given the length of time you were accustomed to the Maggie signature. 

 

I suppose right nuw you could say "it's different" when making a comparison. Do you feel overall it's been a positive change at this stage? 

1 hour ago, ghost4man said:

Do you feel overall it's been a positive change at this stage? 

 

I certainly do, Ozzie.  

 

Andy

 

Are they the new Satori carbon woofers?

28 minutes ago, Steever said:

Are they the new Satori carbon woofers?

 

Yes, I think so.  They are the Satori 'Textreme' woofers.

 

Andy

 

Well, today I’ve finally solved a problem which had been bugging me for a number of weeks!  Yay!  

I had always been getting a slight hash noise from the mid/bass drivers on both channels - and had thought it must be that the interconnects which go into the amps must be passing too close to the amps' power cords. So I experimented with shielded power cords - and this cured the problem in one channel ... but not the other! 

The noise was not loud (you couldn't hear it from the listening position) but it bugged me.  

Anyway, this arvo I swapped the amps around - and afterwards ... I found the hash was coming out of the right channel (not the left)! So it was intrinsic to the amp - nothing to do with interconnects!

Now, the way I laid out these DIY amps was - so as to have the shortest possible input & output wire lengths:

• the amp PCBs are located at the back of the case
• and their PS PCBs are located at the front
• with the power transformers mounted vertically in the front corners.

So, the mains power going to the power traffos runs up the centre line of the case, from the power switch on the back panel. And either side of the centre line are the PS PCBs (one per channel), mounted vertically.

There is a pair of off-board power transistors in each PS, mounted on a heatsink attached to each side of the case. So there are 2 sets of 3 wires going from each PS PCB to the transistor pair.

I saw that the front-to-back mains wires were closer to these 3-wire sets on one side of the ‘noisy’ amp ... than the other. And the side where the mains wires were closer ... was the side driving the mid/bass drivers (where the hash noise was coming from)!

So I moved the 3-wire sets on this side, slightly away from the central mains wires ... and the hash noise went away!  Yay!  Perfect silence out of each channel, now.  

 

Andy

 

Congrats on your new Kyronesgue speakers Andy!

 

When I get out of detention, I would love to revisit and hear them.

 

Cheers

 

David

6 minutes ago, dcathro said:

Congrats on your new Kyronesgue speakers Andy!

 

When I get out of detention, I would love to revisit and hear them.

 

Cheers

 

David

 

Absolutely - it would be a pleasure, David.

 

Andy

 

Looking forward to being able to install my latest TT upgrade.  

 

I reported earlier in this thread that the new CNC'd Delrin chassis for my SkeletaLinn (to replace the original aluminium chassis constructed from bolted-together C-section) turned out to be a disappointment as:

1. Delrin is not stiff enough - the weight at the bearing housing (in the middle between the 3 springs) has caused the chassis to bow, slightly.
2. and it is not as damped a material as I had thought it would be.

So I bought a 20mm slab of 'Panzerholtz' - which is a birch ply impregnated under pressure with resin.  This material is:

1. very stiff
2. and has a much higher damping modulus than Delrin or Aluminium - 0.7 vs. about 0.13 for Delrin and 0.11 for aluminium.

 

I've just heard that the machining is done    So now I just have to wait until the 5km limit goes away, so I can collect it.  Pics are:

 

 

 

 

Can't wait!  

 

Andy

 

Looks really good, Andy.
And the really fantastic thing is you won’t have to put up with any more jokes about your meccano set TT. 

3 minutes ago, buddyev said:

Looks really good, Andy.

 

Thanks, Russ.  

 

3 minutes ago, buddyev said:

And the really fantastic thing is you won’t have to put up with any more jokes about your meccano set TT. 

 

Haha - that's true ... it now can be said to be "classy", don'tcha think?  

 

But as Linn no longer run their Forum ... I'm no longer able to post about it, anyway!  

 

Andy

 

1 minute ago, andyr said:

 

Thanks, Russ.  

 

 

Haha - that's true ... it now can be said to be "classy", don'tcha think?  

 

But as Linn no longer run their Forum ... I'm no longer able to post about it, anyway!  

 

Andy

 

Their loss 

On 07/09/2021 at 7:29 PM, andyr said:

Looking forward to being able to install my latest TT upgrade.  

 

I reported earlier in this thread that the new CNC'd Delrin chassis for my SkeletaLinn (to replace the original aluminium chassis constructed from bolted-together C-section) turned out to be a disappointment as:

1. Delrin is not stiff enough - the weight at the bearing housing (in the middle between the 3 springs) has caused the chassis to bow, slightly.
2. and it is not as damped a material as I had thought it would be.

So I bought a 20mm slab of 'Panzerholtz' - which is a birch ply impregnated under pressure with resin.  This material is:

1. very stiff
2. and has a much higher damping modulus than Delrin or Aluminium - 0.7 vs. about 0.13 for Delrin and 0.11 for aluminium.

 

I've just heard that the machining is done    So now I just have to wait until the 5km limit goes away, so I can collect it.  Pics are:

 

 

 

 

Can't wait!  

 

Andy

 

 

Excellent Andy!

 

Where did you get the Panzerholz?

 

Who did the machining?

 

Cheers

 

David

58 minutes ago, dcathro said:

Excellent Andy!

 

Where did you get the Panzerholz?

 

Who did the machining?

 

Cheers

David

 

Thanks, David.  

 

I bought the Panzerholtz from a place in Nunawading - I can retrieve the name if you want to buy some.

 

Kevin here on SNA did the machining.  If you want to know who it is, I'll ask him for permission to PM you.

 

Andy

 

1 hour ago, andyr said:

 

Thanks, David.  

 

I bought the Panzerholtz from a place in Nunawading - I can retrieve the name if you want to buy some.

 

Kevin here on SNA did the machining.  If you want to know who it is, I'll ask him for permission to PM you.

 

Andy

 

 

Thanks Andy,

 

I am interested to have a play with this material.

 

Will be interested to see how your TT turns out.

 

Must get over to hear your new speakers (without the $5542 entry fee 😮 )

 

Cheers

 

David

On 07/09/2021 at 7:29 PM, andyr said:

Looking forward to being able to install my latest TT upgrade.  

 

I reported earlier in this thread that the new CNC'd Delrin chassis for my SkeletaLinn (to replace the original aluminium chassis constructed from bolted-together C-section) turned out to be a disappointment as:

1. Delrin is not stiff enough - the weight at the bearing housing (in the middle between the 3 springs) has caused the chassis to bow, slightly.
2. and it is not as damped a material as I had thought it would be.

So I bought a 20mm slab of 'Panzerholtz' - which is a birch ply impregnated under pressure with resin.  This material is:

1. very stiff
2. and has a much higher damping modulus than Delrin or Aluminium - 0.7 vs. about 0.13 for Delrin and 0.11 for aluminium.

 

I've just heard that the machining is done    So now I just have to wait until the 5km limit goes away, so I can collect it.  Pics are:

 

 

 

 

Can't wait!  

 

Andy

 

 

Andy

 

That will certainly be interesting compared to the aluminium chassis.

 

 What are you looking for the new chassis to do that the aluminium chassis isn't doing?