mechanical resonance in MMs

You give the impression to be the inventor of the balanced Aurak preamp, not being happy that your design has been transferred to TP.

Anybody may claim or use anything that I have published so far, but please do not give the impression that I misused your ideas.

Hans

Hans,
Please review what I wrote as I made no claims of ownership or authorship and praised what you have done with it. I don’t know how you could have interpreted what I wrote as otherwise. Regardless, the confusion created was mine and for that I apologize. Again, your work has obviously improved the circuit remarkably and I never meant to understate your generosity in doing so. Thank you very much.

My intention was simply to proactively restate the provenance of a circuit in the public domain, not step on anybody’s toes. If you had been following the drama at the VE forum that also spilled over to AK, you might find understand why I would think such a measure would be prudent.

Fair comment, but IMO calling it the 'TP' Aurak is valid as it is based on ready to buy boards from TP and using their servo. This is not optimal from a number of standpoints and was only to get a couple of balanced boards into the wild, which have been delayed for other reasons (she turns 1 tomorrow in my case).

The 'TP' is just one variant, not the one true solution :)

I absolutely understand Bill. As I stated above, I wanted to clarify things for any lurkers out there. I was also hoping Hans and LuckyDog might get some PCBs gratis as a way of saying thank you, which is more likely from an open project at a fab house.
 
Sorry Brink,

You are right, this has been a very collaborative design, didn't mean to drive any biz to anyone, just using the TP to clarify which circuit I was speaking of.

I'm imagining that the params set up, in the latest schema by Hans, for R1 and R2:

R1=9.9k
R2= 87k9-R1

So R2 is = 78K?


Thanks
 
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Sorry Brink,

You are right, this has been a very collaborative design, didn't mean to drive any biz to anyone, just using the TP to clarify which circuit I was speaking of.

No need to apologize. My concern was that it was no longer clear that LD was sharing freely, I was sharing freely and Hans has been sharing freely, and without any commercial affiliation. I think the point has been made so I will retreat again to lurk mode.
 
I'm imagining that the params set up, in the latest schema by Hans, for R1 and R2:

R1=9.9k and R2= 87k9-R1, so R2 is = 78K?
yep.

And to avoid any further confusion, I have made a subcircuit of the OPA1632 and inserted this in the Circuit diagram, just to make it identical to the TP diagram.
Note that I have replaced C11 by a short circuit and removed R22 and R23, using the names as they are called in the TP diagram.

Hans
 

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With that board what 'I' would do is use what Bob Cordell calls 'damped' loading. You load to give a pole at 8kHz and then put a zero in the RIAA eq. This gives u the benefit of removing the resonance without having to make two many mods to an existing board.


Bill,


I'm still reading up on this, I absolutely think that handling as much of this as possible prior to the ADC is a good idea. I just wonder how doing this might effect recordings made prior to riaa? Some of what I will be ripping will include older records. Which is one advantage of having a fully flat phono. I'll download and read the Bob Cordell article and see if I can figure out how to get this in front of my WK flat phono, at least for riaa material.
 
Well 78s in particular might be very different eq wise. I'm certainly not an expert, there is a ton of variation just within the 78s. I will primarily focus on collecting LPs, much of that could be compatible with 'damped loading', even though it is prior to riaa? I really need to download and read Bob's article.
 
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My point was that 78s are in the main not having FR much over 10kHz and often need some fairly heavy EQ. that is a different case from a normal MM setup where you are trying to avoid the bit HF hump you can get with the resonance formed betwen cartridge, cable and preamp. There are many potential solutions to this, but internet lore was that a major cause of this was mechanical resonances, so we have been discussing MM phono stages that explicitly bypass any electrical resonances to see what we are left with.



If you want to do the full Mark Obert-Thorn thing then one of Waynes flat preamps stuck behind the TT may be the best way. A proper mono only cartridge might be helpful too. Oh and a full DAW suite for doing the cleanup and editing. It really depends where you want to compromise.
 
Gotcha, and when it comes to the mechanical we are mainly speaking of cantilever materials and stylus profile? So yes the pre riaa LP/45 stuff will probably still benefit from some sort of damped loading prior to the flat pre. 78s may have to be eq'd only in the digital, where I'm planning to use PureVinyl. The cart I expect to handle all of this is the grace f-8c, using replacement styli from the shure v15 iii, there are 78, mono, E, HE and SAS to choose from, heck I even have a 78-E.
 
Ah, ok. Thanks

That article is a bit confusing. So by loading lower than normal and using no capacitance
I will be improving the electrical resonance part of this prior to the flat phono, making less work for the ADC, right? And this is mainly for RIAA curve material? Easy enough to try this and see. Better than a Capacifier, lol
 
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Not really. Let's take a step back. Read this as saves me making mistakes with rushed typing Hagerman Technology LLC: Cartridge Loading. You only need to get as far as the first graph. This shows the electrical resonant peaking you can get. If everything is right you just get a flat response then a roll off with normal loading. But rarely is everything just right. Then you move into the more advanced methods of doing this which are off piste as regards RIAA specs on phono stages. One is damped loading, the other is the Aurak (there are others as well). These roll off early first order instead of second order for traditional loading.



As to whether this helps the ADC the answer is probably not. Read this http://www.channld.com/aes123.pdf which has a really good analysis of the problem.



At the end of the day it really is picking what you like and optimising it. Spreading yourself too thin and trying everything does cause madness!
 
Yes I agree with that channeld paper, there are other theories out there that suggest maybe better bit utility from an approach like damped loading, though the channeld paper seems to suggest differently.

Thanks for that Hagerman site, a lot there to mess with. Looks like I made some good choices in carts, cantilevers to get both electrical and mechanical resonances out of the audible band.


I will try the damped loading in front of the flat phono, I can always change it when it isn't helpful via a switch.

As far as going insane with choices? Too late for me, I'm building three balanced phono
circuits for three different carts, so I'm officially there already :-0