10 hours ago, metal beat said:

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?

 

Hi Shane,

 

The original (aluminium) chassis had the 2 motors offboard, bolted to plates attached to the top of some machined, brass 'motor pods' - see here:

 

 

 

This is theoretically ideal as:

a.  it means the only way motor vibration can enter the platter is via the silicon belts, and

b.  the motor pods are heavy; they don't sit on the perspex base of the TT but on the bench that the perspex base rests on - and their weight makes them a vibration sink.

 

The circles cut into the perspex base for the motor pods are slightly larger than the pod diameter - so the pods don't touch the perspex base and to allow for some 'play' ... to enable me to get the distance from each pulley to the spindle, the same.

 

I had to go through this measurement process each time I took the outer platter off, when I wanted to make an adjustment - which was an annoyance.  So I thought if the motors could be bolted to 'wings' front and back (see the earlier pic of the Panzerholtz chassis) ... this would make TT setup much easier.  

 

Andy

 

3 months since my last post and not much has changed (I'm still waiting for my 12" Univector arm to be returned with:

• a new headshell
• and arm wiring that goes back to the phono stage.)

So I listen to vinyl via my 9" Magnepan Unitrac arm and Stanton WOS CS100 MM cart.  Unfortunately, with a Hagerman 'Euphonia' phono stage (rather than my own Muse) - which has an annoying mains buzz.  

 

But today my nephew came over - who plays (and teaches) guitar.  So - with music ranging from 'Fat Freddy's Drop' through 'Carmina Burana' to 'Rodrigo y Gabriela', we tried out several of the stored configurations in my nanoDIGI.  I have 4 stored - having different XO points between my mains and subs.  I'm using 24dB BW slopes - so have the XO "@frequencies" spread slightly, to get a flatter FR around the XO point:

• #1:  80Hz bass LP / 100Hz mains HP
• #2:  100Hz bass LP / 120Hz mains HP
• #3:  120Hz bass LP / 140Hz mains HP
• #4:  140Hz bass LP / 160Hz mains HP.

The result is as follows - so it is very useful to have on-the-fly XO changes   :

*  with light-on bass music (like 'Rodrigo y Gabriela'), the best sound is with config #1 - so letting the SB Acoustics Satori 'Textreme' drivers handle the bass (there's not much to trigger the subs into life, with this music!)  

*  but with bass-heavy music like FFD ... the bass delivery is better with a higher XO point:

• #1 had the "clip LEDs" on my 40w Class A amps flicking on regularly - so not ideal
• #4 seemed to be a bit sloppy in the bass (after all - although the subs are sealed ... they have 15" drivers, compared to the 6 1/2" Satori drivers)
• but #3 was the "Goldilocks" selection.

In a future listening session, I will see where #2 fits into the picture.  

 

Andy

 

 

A pic to show a couple of recent additions to the 'heart' of my system:

 

 

 

The 4 small devices on the top are:

*  3x Topping E30 DACs for my 6 channels of amplification.

*  an all-digital (miniDSP) nanoDIGI - which provides:

• the XOs for my 3-way active system (tweeters, mid/bass and subs)
• EQ to compensate for the spkrs having no baffles
• some room EQ
• and time delay (as my subs are about 1.5m further away from my ears than the 'mains').

Then comes the "Solid State Tube Buffer" - a circuit designed by Hugh Dean to add H2 to the signal (to "add a special something" to an all-ss system).  It doesn't add as much as a tube buffer would - but it's dead silent!    It's driven by a 24v AC garden lighting step-down transformer - and contains a rectifier and regulator, to deliver 18v DC to all 6 filter circuits.

 

At the bottom of a stack is a box containing filters for the DC output of the 6x Meanwell SMPSs I have powering my digital devices.  This is a passive device.

 

If anyone is interested in trying out either:

• the Solid State Tube Buffer, or
• an SMPS filter

... please get in touch.  They deliver a very subtle benefit so it is essential that people try one out, before making their decision to buy.    You merely have to commit to paying postage both ways, if you don't think it delivers anything.

 

Andy

 

At last - after 4 months - I was able to set up my SkeletaLinn's new Panzerholtz chassis.

 

Mark Doehmann had taken on the task of:

• mounting a new fixed headshell on the end of my 12" 'Univector' arm
• which involved re-wiring it - so now the arm wires are continuous back to the phono stage.  (Waiting for this wire loom to arrive was the bulk of the time!   )

See pic:

 

 

 

From the pic a couple up, you can see how the headshell used to be connected to the arm stub with a knurled finger-bolt; this was great for being able to adjust the offset angle ... but meant the headshell assembly wasn't as rigid as in the new setup.  (And headshell rigidity is a key issue!)

 

Mark also fixed what he thought was a problem with the way the arm wires were dressed, when they came out of the top of the UP housing - which must've affected anti-skate (which I agree with).  So now, rather than the am wires coming out of the top of the UP housing ... then being enclosed in a silicone tube which loops sideways, down to the terminal block (see previous arm pic), there is a 'wire guide' to route the wires to the centre of the UP housing - then the wires go up and flow down to a clamp-block screwed to the TT base, which is where the shields and wire-protection start, for the journey back to the phono stage.  A wire guide (which you can see sticking up from the perspex base) supports the arm wires just above the UP housing.

 

And, yes, those with keen eyes who know the LP12 will see that I am not using Linn springs under the chassis.    I had some made up about 30% stiffer than Linn springs - to counter the fact that there is more total weight on the springs than with a standard LP12.

 

How does it sound ... wonderful!  

 

Andy

PS: Mark made up some additional 'wire guides' - so will be very happy to do the same mod to other Univector owners ... and rewire them, if requested.  It may not be possible to have your headshell replaced, though - due to headshell supply!  I may have a source for them, if anyone is interested.

 

Edited January 22, 20224 yr by andyr

Looks good. Coincidentally I sold a BBQ and had a good chat with Mark yesterday. He was rather happy to be able to discuss HiFi in a BBQ joint...small world.

On 22/01/2022 at 5:58 PM, tubularbells said:

Looks good. Coincidentally I sold a BBQ and had a good chat with Mark yesterday. He was rather happy to be able to discuss HiFi in a BBQ joint...small world.

And really happy to discuss BBQ in a Hifi World too 😉 Thanks for the amazing SNS Kettle Grill with Mallee Root and Maple/Hickory Smoker. There's a whole new world of subjective assessments in store I'm certain. Kind suits a vinyl head like me!

Well, an update from a month ago.  

 

After the listening session a month ago that @tubularbells and @Mark Doehmann attended, I had a conversation with Mark about the issue that had become apparent - which was: with the motors now mounted on the chassis, I was hearing a LF noise through the subs when I had:

*  removed the belts from the 2 motors - so the platter wouldn't turn when I switched on the motors

*  put an LP on the platter with the stylus resting in a groove

*  then switched on the motors.

 

Whereas there was no such LF noise when the motors were switched off.  (It would seem motor vibration is getting to the bearing - and then the stylus - iow, Panzerholtz is not as good a vibration-absorbing material as I had thought!   )

 

Mark suggested I should cut off the 'wings' - front & back - that had previously supported the motors and instead mount them on a 'sandwich' made from stiff/heavy plates interspersed with something flexible - double-sided foam tape being ideal.

 

So I had a mate who owns a metal-work business, cut the following pieces of steel for me:

 

 

 

Then I assembled them using black double-sided tape, to give this (Sorry the pic is upside down - I tried to correct this - but I can't  😞

 

 

 

Having recently acquired a Karousel bearing ( @Tasebass ), this fits nicely into the rebate in the chassis where the Cirkus bearing had been, previously.  The next step was to attach the "motor bracket" to the underside of the Panzerholts chassis (with 4x ss screws).  This leads to where I am now (and this pic is the right way up!):

 

 

 

Tomorrow's tasks are to turn the above - plus these pieces below:

 

 

 

... back into a working TT!    This involves:

• mounting the 2 arms
• filling the Karousel with oil and dropping in the new inner platter
• mounting the motor controller components and connecting wires
• sitting the chassis on the springs
• and repeating the "motor noise test".

Hopefully ... the metal/tape sandwich construction that the motors are now bolted to will have attenuated the motor noise that I can hear from the subs.

 

Andy

 

Edited February 28, 20224 yr by andyr

Well, today I finished re-assembling my SkeletaLinn - including installing a Karousel bearing in place of the Cirkus bearing.

 

With some trepidation ... I then performed the "motor vibration" test - ie:

1. take the belts off the motors - so the platter does't turn when the motors are switched on
2. put an LP on the platter and rest the stylus in the groove
3. put my ear to a spkr, to find out whether I could hear any LF noise
4. then turn on the motors and again put my ear to the spkr - to see if there was now some noise.

 

I'm happy to be able to report that I couldn't hear a noise difference between #3 and #4!  

 

So thank you, @Mark Doehmann, for your most excellent design for a vibration-absorbing motor-support bracket!  (Which, in case anyone missed it in my earlier post, is a stack of steel plates stuck together with double-sided foam tape.)

 

Now back to listening!  

 

Andy

 

Edited March 2, 20224 yr by andyr

23 hours ago, andyr said:

Well, today I finished re-assembling my SkeletaLinn - including installing a Karousel bearing in place of the Cirkus bearing.

 

With some trepidation ... I then performed the "motor vibration" test - ie:

1. take the belts off the motors - so the platter does't turn when the motors are switched on
2. put an LP on the platter and rest the stylus in the groove
3. put my ear to a spkr, to find out whether I could hear any LF noise
4. then turn on the motors and again put my ear to the spkr - to see if there was now some noise.

 

I'm happy to be able to report that I couldn't hear a noise difference between #3 and #4!  

 

So thank you, @Mark Doehmann, for your most excellent design for a vibration-absorbing motor-support bracket!  (Which, in case anyone missed it in my earlier post, is a stack of steel plates stuck together with double-sided foam tape.)

 

Now back to listening!  

 

Andy

 

Not only sounding good, it Looks great, very elegant!

23 hours ago, andyr said:

Well, today I finished re-assembling my SkeletaLinn - including installing a Karousel bearing in place of the Cirkus bearing.

 

With some trepidation ... I then performed the "motor vibration" test - ie:

1. take the belts off the motors - so the platter does't turn when the motors are switched on
2. put an LP on the platter and rest the stylus in the groove
3. put my ear to a spkr, to find out whether I could hear any LF noise
4. then turn on the motors and again put my ear to the spkr - to see if there was now some noise.

 

I'm happy to be able to report that I couldn't hear a noise difference between #3 and #4!  

 

So thank you, @Mark Doehmann, for your most excellent design for a vibration-absorbing motor-support bracket!  (Which, in case anyone missed it in my earlier post, is a stack of steel plates stuck together with double-sided foam tape.)

 

Now back to listening!  

 

Andy

 

 

Well done Andy.  Personally I would swap out the clear acrylic. 

 

It is now about twice the size of a LP12.

  Obviously size does matter 👍

10 minutes ago, metal beat said:

 

Well done Andy.  Personally I would swap out the clear acrylic. 

 

It is now about twice the size of a LP12.

  Obviously size does matter 👍

 

Thanks, Shane ... but not twice the size - maybe 50% more in each direction.  

 

Yes, that acrylic base is ruined by the holes that I had cut for the original chassis - which had the motors mounted off-board, on brass pods.

 

What do you think would look nice / sound nice, instead of acrylic?

 

Andy

 

On 03/03/2022 at 3:58 PM, andyr said:

maybe 50% more in each direction

1.5 x 1.5 = 2.25 times bigger then. 😅

8 minutes ago, TS23 said:

1.5 x 1.5 = 2.25 times bigger then. 😅

 

True - that's one way of looking at what Shane said!  

 

But I would never have thought I'd ever get a lesson in arithmetic ... from a Kiwi!  

 

Andy

 

On 03/03/2022 at 1:58 PM, andyr said:

 

Thanks, Shane ... but not twice the size - maybe 50% more in each direction.  

 

Yes, that acrylic base is ruined by the holes that I had cut for the original chassis - which had the motors mounted off-board, on brass pods.

 

What do you think would look nice / sound nice, instead of acrylic?

 

Andy

 

 

Birch Ply, stain it the same as the skeletal chassis

4 hours ago, Tweaky said:

Birch Ply, stain it the same as the skeletal chassis

 

Thanks, Tweaky.

 

The benchtop is actually made of birch ply - and I have a sheet of it, only 20mm thick.

 

But are you suggesting it because of looks ... or you reckon it would impart a better sound (than the perspex)?

 

Andy

 

4 hours ago, andyr said:

 

Thanks, Tweaky.

 

The benchtop is actually made of birch ply - and I have a sheet of it, only 20mm thick.

 

But are you suggesting it because of looks ... or you reckon it would impart a better sound (than the perspex)?

 

Andy

 

 

It's rigid and light and easy to machine, 40mm seems the optimum thickness

I was reading up on Birch Ply when I was looking at get a Larvadin Amp, they make stands out of it and give the reasons why not to choose various other materials.......They also charge a small fortune for them

http://www.lavardin.com/lavardin-krakE.html

Edited March 6, 20224 yr by Tweaky

Aah, thanks @Tweaky.  

 

I will have to find someone who can CNC a wood sheet.

 

Andy

 

On 6/3/2022 at 9:37 PM, andyr said:

Aah, thanks @Tweaky.  

 

I will have to find someone who can CNC a wood sheet.

 

Andy

 

@andyr What do you need CNC’d? Would you have/be able to do a clear vector drawing or dimensioned sketch?

 

Cheers,

 

SS

5 hours ago, Sub Sonic said:

@andyr What do you need CNC’d? Would you have/be able to do a clear vector drawing or dimensioned sketch?

 

Cheers,

 

SS

 

Hi SS,

 

I would be able to provide dwgs with dimensions.

 

Andy

 

13 minutes ago, andyr said:

 

Hi SS,

 

I would be able to provide dwgs with dimensions.

 

Andy

 

I’d be happy to do a trial cut in MDF on the CNC and see how it looks to you if you like?

6 hours ago, Sub Sonic said:

I’d be happy to do a trial cut in MDF on the CNC and see how it looks to you if you like?

 

That sounds great - I will PM you, later, SS.

 

Thanks,

Andy

 

Well, a looong job is now behind me - playing with the EQ on the L&R channels of my 4x miniDSP configs, after changing the slopes of the mid/bass-to-sub XO to 48dB (to try and sort out a bass issue which Doug - @tubularbells - identified when he brought over an LP he knows well, a few weeks ago)!  

 

It's taken most of 2 weeks (after several mistakes along the way which caused me to have to repeat some measurements).  I also wasted 2 days because I didn't know that if the spkr icon at the bottom R of the Windows screen is used to mute the PC's spkrs ... it also mutes the output from an external audio interface which is plugged into the PC!  

 

Anyway, I think the issue brought out by Doug's LP was that previously ... I had a phase problem in the mid/bass-sub XO region.  So:

• changing the slopes from 24dB to 48dB
• inverting the subs in the miniDSP
• and changing the main spkr delay to only the amount required by the added distance the subs are away from my ears

... produced a much higher bass output below the XO point - showing that the drivers were now working in sync. 

 

But I had to reduce this ... as my Bob Marley records now had bloated bass.  

 

After a lot of tweaking. I now have the 4x L channel FRs pretty much the same (1/1 smoothing):

 

 

 

... as well as the 4x R channels:

 

 

 

Interestingly enough ... I had avoided using 48dB slopes initially - as 'folk lore' says this will increase Group Delay at LFs.  But the REW GD graphs didn't show much difference!    Unfortunately, though - I don't know how to combine the 24dB & 48dB GD graphs into one display, to show you.  

 

So, Doug - maybe time for a repeat visit?  

 

Andy

Andy

 

One day you might just sit and enjoy what you have for a while 👍

1 hour ago, metal beat said:

Andy

 

One day you might just sit and enjoy what you have for a while 👍

 

You mean ... and stop tweaking, Shane?

 

Never!  

 

Andy

 

@andyr what does the group delay plot look like? can you post it.

 

I built another new pair of speakers (yes it's your fault after I heard yours LOL) and it took me a while to get the GD flat but this makes a huge improvement in clarity and tonal accuracy. From my measurements and listening flat GD is more important than absolutely flat on axis FR.