Since the DCR is pretty similar to the Technics (14 ohm), it was a drop-in replacement; no retuning at the step-up secondary needed. Still dead quiet.
I've got mixed feelings (though mostly positive) about the 103R- there's more of the "classic MC" coloration than I'd like (slight upper midrange dip, rising top octave), and it took a few mechanical mods to optimize it. All in all, it's pretty good. I think that the Audio Technica 150MLX with my new preamp (Equal Opportunity) is better, and a low-hours Technics EPC100C Mk4 that I snagged is better yet, but the Denon is excellent for the money and very easy to listen to.
I've got mixed feelings (though mostly positive) about the 103R- there's more of the "classic MC" coloration than I'd like (slight upper midrange dip, rising top octave), and it took a few mechanical mods to optimize it. All in all, it's pretty good. I think that the Audio Technica 150MLX with my new preamp (Equal Opportunity) is better, and a low-hours Technics EPC100C Mk4 that I snagged is better yet, but the Denon is excellent for the money and very easy to listen to.
I drilled a couple small holes in the cartridge body and filled the space with a filled viscoelastic polymer. I see that other people actually pull off the body and replace it, which scared me a little bit.
The trick (besides a steady hand with the Dremel and drill bit and knowing where to drill) is propping the cartridge up on its pins before injecting the uncured resin (which has to be low viscosity). Since I run a chem lab, I was able, cough, cough, to have one of the guys formulate a suitable epoxy. I filled the epoxy with some powdered high damping elastomer that I had cryoground before injection.
This sounds involved, and I guess it is, but it's easier for a chemist to pull off in lieu of precision machining a new headshell. A skilled machinist with a good Bridgeport could bypass all of this and just fabricate a tight-fitting shell.
The differences were not night and day, but my uncontrolled perception was a bit more "tidiness" to the midrange sound.
Actually, I think the 103R could be a very nice match for LS3/5A.
The trick (besides a steady hand with the Dremel and drill bit and knowing where to drill) is propping the cartridge up on its pins before injecting the uncured resin (which has to be low viscosity). Since I run a chem lab, I was able, cough, cough, to have one of the guys formulate a suitable epoxy. I filled the epoxy with some powdered high damping elastomer that I had cryoground before injection.This sounds involved, and I guess it is, but it's easier for a chemist to pull off in lieu of precision machining a new headshell. A skilled machinist with a good Bridgeport could bypass all of this and just fabricate a tight-fitting shell.
The differences were not night and day, but my uncontrolled perception was a bit more "tidiness" to the midrange sound.
Actually, I think the 103R could be a very nice match for LS3/5A.
Hi Sy, the article still stands as very worthy IMO. Thought to return a comment since the extent to which noise has been considered seems comprehensive yet there is one aspect which I recently became aware of which seems relevent and I can't see covered.
Series resistance of the the primary winding of the SU tx appears at the tx secondary output multiplied by (turns ratio)^2 as a noise source. In series with the resistance of the secondary winding itself, which might also be significant as a noise source. In the grand scheme of things when other noise sources have been reduced to the limit, intrinsic noise within the SU transformer remains potentially significant in principle I think, and should be considered as a selection criteria for the SU transformer - particularly if the SU (turns) ratio is high.
Series resistance of the the primary winding of the SU tx appears at the tx secondary output multiplied by (turns ratio)^2 as a noise source. In series with the resistance of the secondary winding itself, which might also be significant as a noise source. In the grand scheme of things when other noise sources have been reduced to the limit, intrinsic noise within the SU transformer remains potentially significant in principle I think, and should be considered as a selection criteria for the SU transformer - particularly if the SU (turns) ratio is high.
Absolutely true in theory. But let's put some numbers in: the Sowter I used has a primary DCR of 0R72. Compare that with the cartridge DCR (~15R) and it's pretty well buried. Likewise, the secondary DCR is about 100R, which is negligible compared to the reflected impedance of the cartridge (1k5).
But your point is valid- if we use a cartridge with a low DCR, we'll want to choose a transformer with a low primary resistance in comparison. Because the noises add in quadrature, a transformer resistance less than 1/3 that of the cartridge will be pretty negligible.
But your point is valid- if we use a cartridge with a low DCR, we'll want to choose a transformer with a low primary resistance in comparison. Because the noises add in quadrature, a transformer resistance less than 1/3 that of the cartridge will be pretty negligible.
Sy, yes your choice of SU tx looks spot on, and I agree in that case it's not significant. Worth noting that not all SU tx are equal, and certainly not if one subs in tx not devised for the job I think. Aside, leakage inductance of the primary also appears ^2 in series with the secondary, and that's another story and rarely specified for SU tx. Just to comment that I think these things are worth noting if subbing an alternate tx perhaps.
It's not that the non-permeable former MC carts don't play well with transformers, (most commonly the Denons) but that most transformers are optimized for a much lower coil inductance.
Really low primary transformers is difficult to wind and to get to couple, and so need to be used in the range they are designed for. To high coil impedance, and they get funky response.
Conversely, if the cartridge inductance and coli inductance is mated properly, all becomes happy. (And incidentally the SUT are actually much easier to make.)
I have a set of Electra-Print SUT that are centered on a nominal 40R cartridge coil. My plan was to use a Denon of some sort, either a hot-rodded DL103 or a DL-S1.
It will also be good with my medium output Benz (50R coils)
Really low primary transformers is difficult to wind and to get to couple, and so need to be used in the range they are designed for. To high coil impedance, and they get funky response.
Conversely, if the cartridge inductance and coli inductance is mated properly, all becomes happy. (And incidentally the SUT are actually much easier to make.)
I have a set of Electra-Print SUT that are centered on a nominal 40R cartridge coil. My plan was to use a Denon of some sort, either a hot-rodded DL103 or a DL-S1.
It will also be good with my medium output Benz (50R coils)
It's pretty high, a few hundred pF. If your cartridge is happy with that (plus the 100-150pF or so of the interconnects), you can use the circuit minus the input transformer. You do lose the advantage of balanced input, though. That's why I designed the Equal Opportunity for MM use; I'm a firm believer in balanced operation of phono cartridges.
Thx SY !
I have too many carts around here , usualy not happy with a couple hundred pf load . Is there another way to get the circuit more versatile for a large range of MM / MI carts ? I know there's some math involved here .. but would a sort of 1:1 or small ratio step up isolation transformer solve things for MM/MI ?
For MC's I have a pair of Lundahl LL9206 suts laying around here , also a pair of LL1676 Mic / line amourphe inp xfrs that may be usefull
THX
Paul
I have too many carts around here , usualy not happy with a couple hundred pf load . Is there another way to get the circuit more versatile for a large range of MM / MI carts ? I know there's some math involved here .. but would a sort of 1:1 or small ratio step up isolation transformer solve things for MM/MI ?
For MC's I have a pair of Lundahl LL9206 suts laying around here , also a pair of LL1676 Mic / line amourphe inp xfrs that may be usefull
THX
Paul
Excuse me SY , I have missed the other circuit meant for MM use . but all clear now
So here another thought of mine . suppose I would use the circuit with resistive 47K or 100K load at the input grid for MM carts ( I do realize the noise penalty ) , but using the 1:1 amorphous core input xfr ( thus with the resistive grid load across the primary ) ... will there still be a benefit due to the isolation from circuit ground ??
TIA
Paul
So here another thought of mine . suppose I would use the circuit with resistive 47K or 100K load at the input grid for MM carts ( I do realize the noise penalty ) , but using the 1:1 amorphous core input xfr ( thus with the resistive grid load across the primary ) ... will there still be a benefit due to the isolation from circuit ground ??
TIA
Paul
You might want to consider going to the linear audio website and purchasing both articles pertaining to the Equal Opportunity phono preamplifier. I too was inching my way towards building the HMN (for MC duty) but also like the idea of having a preamp suitable for balanced operation of both MM and MC. Adding a SUT to the Equal Opportunity accomplishes this so I have thusly changed course.
That's been the most commonly asked question in this thread. The answer is sorta, but it's not a great option. You lose the advantage of balanced in (and thus common-mode rejection) and the input capacitance is quite high, a problem with many MMs. This is what led to the development of the Equal Opportunity preamp, optimized for MM. It was published in Linear Audio (volumes | Linear Audio) where the PCB files and layout are also hosted.