Attempting to understand the Loading on a Cartridge

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JohnG
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Attempting to understand the Loading on a Cartridge

Post by JohnG » Sat Apr 04, 2020 3:07 pm

As requested by Nick,
I will put my heart on my sleeve, with my recent chain of thoughts on how 'I am thinking' what is required to create a improved interface from Cartridge to the Phonostages output.

As most who know my posts, will be aware, I am a non EE minded individual, mathematical equations are painful for me, so much of what I decipher is from explanations.

As I have recently made a investment in a Phonostage, that has come in at more than a price tag I usually lean toward,
and as a result of the impression this Phonostage has made on me.
I have started investigating the science that is attached to LOMC's and trying to work out what is the Requirement to produce the usual referred to 100 Ohms Capacitance, I would also like the option to introduce other cables to alter the 100 Ohm setting.

As the Phonostage I am now using is not a multi adjustable design, it was seeming to me that I will have to gain knowledge of the Cartridge Output, Tag Wires Pf, Tonearm Wires Pf, and Phono Cable Pf to try and gather all the information to identify a overall capacitance.

That is where I am at with the thought pattern on what is required.

As I also intend on bringing in another Cartridge to undergo a rebuild, to produce similar to my K'b rebuild experience rebuild,
I was also looking into the matching of my HM-3 SUT for either Cartridge, and it would appear the 1:10 setting it is set on is ideal.

Running Parallel with my intention to achieve a 'ideal for me' interface between Cartridge and the Phonostage Output.
I have purchased a pair of Cinemag 1245 Transformers, which will be produced to a working 1:10 ratio SUT, these are now delayed as COVID 19 has impacted on production.

This is a whole new area of thought from me, I have only ever seen discussions on Cartridge Loading and never thought about how my system is in relation to it, I've used on many occasions adjustable MC Phonostages and adjusted a few DIP Switches.

At present my set up is a Ortofon K'b, > Audio Technica PCOCC Tag Wires,> Kabusa Tonearm Wire, >
0.75 mtr of Yannis Tome Silver PCOCC Phono Cable > Hashimoto HM-3 > 1mtr Audio Technica PCOCC > 'Seraphim' Phonostage.

My old set up was as the above, with the DIGNA Phonostage in place instead of the 'Seraphim'.

The DIGNA is a multi adjustable Phonostage, and by using these adjustment options, I do feel I could produce audible changes that were a improvement on how my ears perceived the presentation.

I do not get the opportunity to make immediate changes with my present set up, and am of the opinion, it will be different
Cables Pf measurements that will produce changes, which seems to be the Crux of my new investigations, bringing in new cables with different Pf measurements.

Up until recently, I have settled for a Hum Free Vinyl Front End as the Goal, and have fell short on achieving this as well.

This is where my thinking is at this moment, I am happy to be steered to a better understanding.

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Nick
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Re: Attempting to understand the Loading on a Cartridge

Post by Nick » Sat Apr 04, 2020 5:24 pm

Generally LOMC have a low internal resistance so capacitor loading has far less effect on them than a moving magnet. The reflected resistive loading will have more effect. Loading the secondary or primary of the step up are options, though personally I have never got on with primary loading, but I know Andrew is a fan. There is also potential merit of fitting a zobel on the step up secondary, but again I remember hearing mixed results. Where cable in input capacitance will make a difference is on the secondary side of the step up as thats a higher impedance system.

Whats the input capacitance of your phono stage?
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Re: Attempting to understand the Loading on a Cartridge

Post by JohnG » Sat Apr 04, 2020 5:28 pm

Hi Nick
Thank you for the contribution.
I will make an enquiry about the Phon's, input capacitance and report back.

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Re: Attempting to understand the Loading on a Cartridge

Post by JohnG » Sun Apr 05, 2020 11:49 am

Hello Nick
I have been informed that the Phonostage is adjustable, but at present it is set at 39pF.

When you refer to the Secondary Side of the Step Up.
Are you referring to the Cable used between the SUT Output and the Phon's Input ?

I am not familiar enough or Consider myself Savvy to discuss resistors placed in the Signal Path, but if this was to be a option to be worked with, then I would feel that the there would be variants of the reported findings, if the used resistor would be off different build qualities, probably a bad example, but say Carbon or Z Foil would potentially have noticeable effects on the SQ.

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IslandPink
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Re: Attempting to understand the Loading on a Cartridge

Post by IslandPink » Sun Apr 05, 2020 12:55 pm

You would normally have a resistor placed across the step-up transformer secondary winding, for an MC cartridge. If this S.U.T. is feeding the input to a valve first stage, this resistor is usually also the grid-leak resistor ( grid to ground ) for the first valve.
This is the way I do it and most others would, using a valve phono. The resistance across the secondary is set by some knowledge of what the cartridge requires, then the value can be adjusted up or down depending on personal taste and the system context.

The only bit of maths required is that the recommended loading value for the cartridge needs to be multiplied by the square of the step-up value to get the resistance you'd put on the secondary .
As an example with my Denon 103R , the recommended loading is about 100 ohms. I Use 1:10 step-up transformers, so this means we need 100 x 10 x 10 ( = 10,000 ohms ) across the transformer secondary. I just put a quality resistor ( Vishay bulk foil ) of this value as my grid-leak on the first valve.

What is your cartridge and what does it typically need for loading ?
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Re: Attempting to understand the Loading on a Cartridge

Post by JohnG » Sun Apr 05, 2020 2:07 pm

Well this is off interest to me, as I am using a Hashimoto HM-3 that was produced to be used with a Sansui SS Integrated Amp's
MM Stage.

When I received the HM-3, I had used it with the MM Stage on a Hybrid Phono Stage called the DIGNA.
The SUT gave the impression of a little more meat on the bones than the inbuilt MC Channel, but that was when the Phon' had about 30 hours playtime from new, the comparison if carried out today could be different, as the Phon' has few hundred hours playtime and has been modified to receive alternate valves, of which the E88CC/ECC88 family are producing a much improved presentation beyond the stock ECC8100 .


Now the HM-3, is being used with a Valve Input/Valve Output Phono Stage.

Your reference to a addition of a resistor has got my attention, as without making a further enquiry, I am not aware of any components in the SUT's other than the Tranx, even the 1:10 /1:20 switch was removed by the builder to keep it as clean on the signal path as possible.

Now with the way I am using the HM-3's into the Valve Phon' your suggestion for a resistor is a new idea to work with.
Am I correct in saying if this method is used, the best quality resistor, will be the better choice ?

My Cartridge is a Rebuilt Ortofon Kontrapunkt B, that has a recommended 100 Ohms Loading.

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IslandPink
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Re: Attempting to understand the Loading on a Cartridge

Post by IslandPink » Sun Apr 05, 2020 2:32 pm

OK, well I think you need to ask your phono builder two questions :
1. What did he set the HM-3 step-up to deliver - 10x or 20x ?
2. What grid-leak or secondary resistor did he choose - ie. what is across the transformer secondary in the circuit ?

It may be he made an attempt to get the values correct, if he knew what cartridge you'd be using - but it's worth checking.
Certainly a good quality resistor here is worthwhile.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Attempting to understand the Loading on a Cartridge

Post by JohnG » Sun Apr 05, 2020 3:37 pm

The next information required will take a little longer to gather, but I could be proved wrong.
The HM-3 SUT replaced the Builders Modified Denon HA-500,
the HM-3 was used with a Ortofon Vienna when I bought it, and the Cartridge in use by the builder before the Vienna was a K'b.
A Ortofon ST-?? was the replacement SUT for the HM-3.

I feel confident the HM-3 is set at 1:10, but that can be confirmed by the builder.
That's the history of this HM-3 laid out

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Re: Attempting to understand the Loading on a Cartridge

Post by Neal » Sun Apr 05, 2020 8:08 pm

I also like primary loading of a SUT. Secondary loading balances the need to present the correct load to the cartridge against dampening of the SUT losing output level in the process. After a lot of trials I got good results having selectable primary loading with a secondary zonel to dampen the SUT. The advantage to me was not only better sound quality but also selectable cartridge loading that is independent of the damping on the SUT.
Only the Sith deal in absolutes.

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Re: Attempting to understand the Loading on a Cartridge

Post by Neal » Sun Apr 05, 2020 8:15 pm

More reading here: http://www.rothwellaudioproducts.co.uk/ ... xplai.html

One often overlooked aspect of cartridge loading is effects on tip resonance, for instance on the Kontra B I prefer the sound not at the suggested 100ohm but at 47ohm. This damps the tip more and to my ears give a more controlled presentation. 100ohms follows the rule of thumb for the load to be x10 the cartridge output impedance, it’s not set in stone and depending on your system and ears may be better set to something else.
Only the Sith deal in absolutes.

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Re: Attempting to understand the Loading on a Cartridge

Post by JohnG » Mon Apr 06, 2020 7:25 am

Neal
Thank you for your adding to the thread.
I will be finding out more about resistor loading, anything that references a improved SQ, will become better understood on how to achieve the set up.
I am on side with your not using the 100 Ohm with the K'b.
With the DIGNA Phon' I recall my selected settings were not producing the recommended 100 Ohm, but I can't recall the settings for the choice that was in use.

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Re: Attempting to understand the Loading on a Cartridge

Post by JohnG » Fri Apr 10, 2020 12:11 pm

Before this Thread started, I asked the builder of the HM-3 a few questions and sent a link to a Web Page.
I have received a response, and the pasted a paragraph of the reply to this post.
My assumption of 1:10 has been incorrect.
I'm still yet to ask about any other build info, as Cinemag have Joined in the Lock Down
in the USA, it may be a minimum of 12 Weeks before a initial batch is released for the Group Buy.
Another opportunity to sit tight and let this situation pass through.
I will update on this when Liberty is seeming more likely to become available to interact face to face with others once more.
As this will enable any additional works that might appear to be beneficial to be undertaken, put in place by the builder.


The Hashimotos and the Ortofon ST-80se have 1:20 ratios, so the voltage step-up is 20, giving 9.4 mV (high but not ridiculous) and a load of 47000/(20 x 20) which equals 117.5 ohms, closer to the target value.

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Re: Attempting to understand the Loading on a Cartridge

Post by JohnG » Sun May 03, 2020 1:40 pm

There has been positive news supplied, that the owner of Cinemag has personally produced the Group Buy 30 units of the SUT's.
They are expected to be shipped to all GB Members from next week.

One of my local group members is producing a SUT as well, so hopefully another group agenda to be undertaken post Lock Down.
It is looking like, the five completed versions of the B1 Korg will become the priority.
I know the very recently new produced DAC is yet to be unveiled and a to all, and this will be put out against a few models already in use, I have enjoyed the positive reporting from the builder, and look forward to the audition.
As well as the SUT's that are becoming available and the Albums that are being discovered as a result of all the available free time,
it looks like the post Lock Down will have a few good get together sessions for the local group to be enjoyed.

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Re: Attempting to understand the Loading on a Cartridge

Post by little eddy » Thu May 14, 2020 5:46 pm

Nick wrote:
Sat Apr 04, 2020 5:24 pm
Loading the secondary or primary of the step up are options, though personally I have never got on with primary loading, but I know Andrew is a fan. There is also potential merit of fitting a zobel on the step up secondary, but again I remember hearing mixed results.
Well just tried primary loading and I'm an instant convert. Of all the tweaks I have done, this has to be one of the most successful for not a lot of effort.

Over the last months, when listening to some vinyl recordings, many tracks/records seemed to be edgy and I had thought this may have been down to the recording/pressing. Well I sat down, (read I did 2 hours of ironing), and just enjoyed listening to 4 full sides of music, something I don't think the daughter has ever done with me. Everything was so much more musical and was not 'distracted' by trying to pick up particular nuances and detail of a particular recording.

I used resistors I had to hand, Takman carbon 47k and Takman metal 75R for the primary. I had initially thought that the prior edginess may have been due to resonance/ringing, hence my recent investigations in to a secondary Zobel network. But this may have been a red herring as I did this without the Zobel, (but I now think the benefit of a Zobel increases as the phono stage input capacitance reduces - mine's quite high at around 400pF).

At 75R loading, this is lower than my previous secondary set-up at an effective 50R. I had expected that the edginess would still be there, if not worse. But to the contrary I am now thinking of trying 100R or even 150R, (my MC25FL has an Rdc of 6Ohm and recommended load is >20). By reducing the loading I may be able to get more sparkle without sacrificing the musicality.
TD-125/RB250/MC25FL & 'Snail' phono, NAS/SBT with CS4398 DAC, 41MP pre & MoFo Power, still messing with OBs.

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