Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: joralieu on November 30, 2022, 09:37:11 AM
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I have an Eros 2 on order. I have Denon DL-S1 moving coil cart. I inquired about this cart earlier and was told that this would not be a good match with the eros 2. I noticed the chart on the sowter website that shows a 9570 transformer would work with the DL-S1. Really like the DL-S1, been using it with a Channel D Lino that has computer based software to rip vinyl to my computer. Pretty much done with that and want to go to an all analog rig. Any advice would be appreciated. Love building these things.
Thanks
Joe
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I wrote a few different responses to this but ended up deleting them all.
The DL-S1 has both high internal impedance and very low output. I would not recommend using this with a tube preamp/step-up transformer combination.
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Okay DL-S1 is out, what about a Denon 103 ?
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A 103 or a 103R?
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actually a zu 103
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The 103R is worth the stretch if you can, as it will work happily with your garden variety 1:20 step-up transformer.
The 103 has double the output of the DL-S1, but still the same wonky high impedance. I helped a local customer setup his Eros for a DL-103, and we used a pair of these transformers:
https://www.parts-express.com/Jensen-JT-DB-E-Premium-Direct-Box-Transformer-121-246-0101?quantity=1 (https://www.parts-express.com/Jensen-JT-DB-E-Premium-Direct-Box-Transformer-121-246-0101?quantity=1)
You'll need to carefully drill the hole pattern into the Eros top plate, but otherwise they worked really well and he's very happy with his setup. I believe I also changed the 47K loading resistors to 100K to keep the cartridge happier.
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I tried to find enough technical information to make sense of this question, and discovered instead that both Denon and Sowter web sites seem have issues. I think Sowter has many obsolete web pages and not all the links have been updated yet; Denon only lists a few of their cartridges - perhaps the others are no longer in production? Anyhow, I'll dive into the technology in case anyone is interested:
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Basically, you want two things - the stepup ratio to make 3mV-5mV at the Eros input, and enough impedance to maximize the cartridge performance. That last one is the killer - transformer makers say one thing, cartridge makers say another, and the internet says all kinds of things ...
Usually the load resistance is made to be much larger than the cartridge resistance (usually more than 10 times greater) which means the cart is nearly unloaded. Loading the cartridge with a smaller resistance reduces the signal voltage and damps stylus resonance(s). Some people use that damping to optimize the load on the cartridge, but 1) the decreased output voltage is severe, and 2) the damping may compensate for other high frequency problems, such as the tweeter in the speaker being used, or the listener's hearing. So everybody's result is different, especially on the internet ... :^)
For example, 10:1 stepup presents a load of 470 ohms (into the 47K preamp input). That's more than 10 times the DL-S1's 40 ohms, but the output is still reduced to 1.35mV.
With a 20:1 stepup feeding a 47Kohm Eros input, the load presented is about 120 ohms, and the voltage losses reduce the ratio to 14 for a net output of 2.1mV to the Eros, still not ideal.
You might think that a 30:1 transformer would be the answer, but that gives a cartridge load of 52 ohms and a net stepup of 17 and 2.5mV - not much improvement at all (and probably way too much damping).
Now, some say the optimum for DL-S1 is a 100 ohm load, so you might be OK with a 20:1 ratio - Eros will be a little hissy with tube rush, though it's probably masked when music is playing. But you lose the option of trying less damping, which is often recommended on the internet.
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On the other question, the DL-103 has twice the voltage (0.3mV) at the same 40-ohm resistance, so it is better suited to a 10:1 stepup, net output 2.7mV. Still a little low though. With 20:1 you'd get 4.1mV, in the sweet spot but still with a maximum 120-ohm load on the cartridge.
DL-103R has a lower resistance of 14 ohms and nearly the same output - 0.30mV (Sowter) or 0.25mV (Denon). That would reduce the losses, but won't make a big difference.
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Thanks for the detailed explanation, I will look for a more compatible cartridge. Maybe go back to MM cartridge for this project.
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IMHO, it makes sense to set up with a higher output cartridge and get yourself situated. From there you can try a lower level cartridge and whether you need to explore transformer options.
There are a lot of variables best to divide and conquer...John
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Well stated John.
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Okay, any recomendations on what cart to use with a stock eros2 ? I had a shure v15mr that I liked but sold it awhile back. Like to hear what other eros 2 owners are using.
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I would look at adding the Sowter 1990 step-up transformers which would work with the widest variety of moving coil cartridges possible.
The Hana SL with the 1990s set for 1:10 would be a nice combination, and I have two local Eros users in the area using this exact combination happily. (Oddly enough the guy with the DL-103R bought a second, older Eros 1 and also has an Eros 2 with 1990s that he uses with the SL).
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Would the Hana SL be a good match with a technics 1200 G turntable?
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The specs for that arm look to work quite nicely with the SL.
http://korfaudio.com/calculator (http://korfaudio.com/calculator)
That is typically the calculator I use to check on this.
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Would a Hana SH work without the transformers?
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HOMC carts with the Eros will work, but there will be a fair amount of tube rush since the signal coming into the Eros is 8dB or so lower than optimal.
The Sowter 1090 works to bump up those middle of the road HOMC carts to a more appropriate output, but then you're stuck with 2-3mV HOMC options.
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Paul, thanks for posting the link to the calculator. So much info on this website, what a great find.
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It just dawned on me that I could run the DL-S1 out of the Channel D straight into the Eros 2. The Channel D Lino I have is flat output (no riaa) so I think that might work. It is balanced XLR though so not sure how to connect it to the Eros 2. What do you think?
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The Lino has about as much gain as an RIAA preamp, so if you feed that into the Eros you will likely overdrive the Eros.
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Finished my Eros 2 running it with my Denon Dl-S1 thru my Channel D Lino set to the lowest gain setting (43db). Doesn't sound to bad. The channel D has options to set impedance from lowest 60 ohms highest 2000 ohms some levels in between. What would be an appropriate setting? The board in the Lino also has sockets for adding capacitors to change impedance.
Thank you
Joe
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Assuming it's the transresistance input preamp, I can't tell what Channel D means by gain or impedance. You would do best by asking Channel D and/or Denon.
I do see that Denon recommends 100 ohms or more for the load on the cartridge, but of course the transresistance input impedance is nearly zero since it's a current-input circuit.
Hmmm ... I wonder if we could make a tubed transresistance MC stepup? :^)
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I talked to Channel D they didn't recommend using it this way. I have a AT WM95E going try, probably sound better then this goofy setup
Thanks
Joe
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So, how would a Denon DL-S1 cartridge with a Denon AU-S1 transformer work in front of the EROS 2? Supposedly that transformer was the mate for the DL-S1.
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The DL-S1 is 0.15mV with a recommended loading impedance of over 100 ohms. The AU-S1 is a 1:13 step-up, so you're going to get that to just under 2mV. This is on the low side for the Eros, but I would expect surface noise on the LP to be more present than the noise floor of the SUT/Eros.
A 1:20 SUT (Sowter 9990) with the DL-S1 will still present more than 100 ohms of loading impedance to the cartridge but get the level up a bit more.
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Hmmm ... I wonder if we could make a tubed transresistance MC stepup? :^)
Paul — transimpedance phonostages are all the rage these days, so there should be customer interest. I for one would be interested in such a front end for my Eros2.
As for carts to use with the stock Eros2, the Ortofon 2M Black LVB250 is superb. A famous nearby tonearm designer agrees ….
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MM carts with the Eros 2 ... I'm quite happy with my Ortofon 2M Bronze.
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Bobs devices says a Sky 30 will work fine with the DL-S1 and the eros. What do you think?
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The DL-S1 has around 0.15mV of output, which is super low, so I'd want something like a set of1:30 step-ups. The recommended loading impedance is 100 Ohms or greater, so you could use a 1:30 step-up into the Eros and load each secondary with a 100K resistor and it would look OK on paper but it's the performance of a 1:30 transformer with that loading is unlikely to be optimal. The actual impedance of the DL-S1 is also really high at 40 ohms, so that recommended loading impedance of 100 ohms seems very low.
The Sowter 1590 is a 1:30 SUT that can be ordered with threaded grommets that will mount right into an Eros 2, so instead of spending $1400 on external Cinemags, you could spend $350 to integrate them into the phono preamp.
If you were planning on spending $1400, you could get a different cartridge and a more typical set of step-ups to not have to deal with these issues.
This was covered about a year ago here: https://forum.bottlehead.com/index.php?topic=14306.msg130351#msg130351 (https://forum.bottlehead.com/index.php?topic=14306.msg130351#msg130351)
The circumstances have not changed since then.
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I realize this is late to the party, but here is a link http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html (http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html) to what appears to be an excellent explanation of transformer and cartridge matching. I don't understand a fair amount but the basics are easy enough to wrap one's head around.