Looks like another approach might be to just use a 1:1 transformer to preserve the balanced nature of the input (and provide for a future change to a MC setup...
How do I deal with the relative input impedances?
The Jensen line input 1:1 transformers have 10K:10K impedance ratios. If I need 47K would I put two 18.5K resistors in each input leg, and 10K (or 47K?) across the outputs?
How do I deal with the relative input impedances?
The Jensen line input 1:1 transformers have 10K:10K impedance ratios. If I need 47K would I put two 18.5K resistors in each input leg, and 10K (or 47K?) across the outputs?
My concern is really the range of choices.
This may not be a perfect rationale, but the price range for MC cartridges has an average around $2K, which means at $200, you are looking at the bottom end of the offerings in that technology. MCs are hard to make, and harder to make well, which is why the average price is so high. In contrast, MM and MI cartridges are much easier, and so the midpoint of that technology is around $500. Some purists will probably argue that you get what you pay for, and nothing beats a $5K MC cartridge..but...
If you find that you don't really like the Denon, or other bottom end MC offerings, then your options are to sell your car and buy a MC cartridge made by a Japanese National Treasure artisan (preferably with a housing made from ancient cedar trees that were blessed by a Shinto priest), or build a different preamp. I am not knocking MCs, but personally, I'd rather have as many options as possible within the constraints of my budget.
My 2 cents..
If you, or anyone else want the Eagle CAD (schematic and board layout) files for the HMN (with untested board layouts) I'll be happy to post them.
I am intrigued by the EO preamp. When I was wondering how I might tweak the HMN design for a MM application realized that a differential input would probably be a good approach, But Stuart seems to have taken that to an entirely different level!
Scott
This may not be a perfect rationale, but the price range for MC cartridges has an average around $2K, which means at $200, you are looking at the bottom end of the offerings in that technology. MCs are hard to make, and harder to make well, which is why the average price is so high. In contrast, MM and MI cartridges are much easier, and so the midpoint of that technology is around $500. Some purists will probably argue that you get what you pay for, and nothing beats a $5K MC cartridge..but...
If you find that you don't really like the Denon, or other bottom end MC offerings, then your options are to sell your car and buy a MC cartridge made by a Japanese National Treasure artisan (preferably with a housing made from ancient cedar trees that were blessed by a Shinto priest), or build a different preamp. I am not knocking MCs, but personally, I'd rather have as many options as possible within the constraints of my budget.
My 2 cents..
If you, or anyone else want the Eagle CAD (schematic and board layout) files for the HMN (with untested board layouts) I'll be happy to post them.
I am intrigued by the EO preamp. When I was wondering how I might tweak the HMN design for a MM application realized that a differential input would probably be a good approach, But Stuart seems to have taken that to an entirely different level!
Scott
The DL-103 is a very competent cartridge, price be hanged. MC carts have turned into high-end jewelry with price tags to match.
Things to know about the DL-103 -
1) It's very high compliance, I.E., the suspension is pretty hard. It's made for heavier arms, so if you've got a lightweight it's not going to match well. Many arms have the ability to add weight to the head and the counterweight, that's a perfectly good solution.
2) It has a fairly high (for a MC) coil impedance, meaning you need to have an input transformer that will load it properly. I had Jack Elliano of Electra-Print make me a set for 40ohm and about 1:30, I'd need to look exactly. Not particularly expensive and it works perfectly.
Things to know about the DL-103 -
1) It's very high compliance, I.E., the suspension is pretty hard. It's made for heavier arms, so if you've got a lightweight it's not going to match well. Many arms have the ability to add weight to the head and the counterweight, that's a perfectly good solution.
2) It has a fairly high (for a MC) coil impedance, meaning you need to have an input transformer that will load it properly. I had Jack Elliano of Electra-Print make me a set for 40ohm and about 1:30, I'd need to look exactly. Not particularly expensive and it works perfectly.
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For an MM cartridge you can abandon balanced mode and load the grid of the D3a with ~47k.
I have the Denon DL-103, and scratch my head when I see reviewers wax poetic about carts which cost kilobucks. Your better off sticking with the Denon and investing the balance in tickets to live music.
I have the Denon DL-103, and scratch my head when I see reviewers wax poetic about carts which cost kilobucks. Your better off sticking with the Denon and investing the balance in tickets to live music.
Scott, thanks for the files. I just downloaded Eagle.
6L6, I have a Linn LP-12 with the Ittok LVII tonearm. I just looked up the specs, the Ittok has an effective mass of 11.5g, and accepts carts of 2-10g. Is this considered "low mass"? Sorry if this is simplistic...I'm just getting back into audio after a kid-raising hiatus.
Andy
6L6, I have a Linn LP-12 with the Ittok LVII tonearm. I just looked up the specs, the Ittok has an effective mass of 11.5g, and accepts carts of 2-10g. Is this considered "low mass"? Sorry if this is simplistic...I'm just getting back into audio after a kid-raising hiatus.
Andy
Hi Sy,
great Thread, thank you.
you wrote:
I'd run the first stage at 10mA, the second two at 4mA. The original values work fine, but dropping the current will extend tube life and reduce heat at no performance penalty.
How can i adjust this operating points? Need to change the CSS?
best regards Frank
great Thread, thank you.
you wrote:
I'd run the first stage at 10mA, the second two at 4mA. The original values work fine, but dropping the current will extend tube life and reduce heat at no performance penalty.
How can i adjust this operating points? Need to change the CSS?
best regards Frank
I have a couple (or so) of questions about the power transformers.
1. Main tx, is there any reason i shouldnt use a single wound secondary with just 1x250v (or whatever) on it and use a full bridge rectifier? ( i get why you need the centre tap to use just 2 diodes). Are there any advantages (apart form saving 2 diodes!) to using the centre tapped 250v-0-250v (which i think is a presumably more costly 500vct tx).
2. The article says more voltage on the raw supply is better leaving a 25v to 40v buffer for the regulators. How high is too high?
3. With regard to applying the voltage to the centre tap of the 18vct heater supply. It looks like this would produce rails of 60v+12.7v and 60v-12.7v to feed in to the heater regs.
Is this essentially a 2x9v transformer?
Im not quite sure how you would wire this.
Va
0V
Vb
0v
For a dual rail supply you would tie 0v and vb together to give ground. Is this the same as a centre tap and so you can do all the usual tricks with it?
1. Main tx, is there any reason i shouldnt use a single wound secondary with just 1x250v (or whatever) on it and use a full bridge rectifier? ( i get why you need the centre tap to use just 2 diodes). Are there any advantages (apart form saving 2 diodes!) to using the centre tapped 250v-0-250v (which i think is a presumably more costly 500vct tx).
2. The article says more voltage on the raw supply is better leaving a 25v to 40v buffer for the regulators. How high is too high?
3. With regard to applying the voltage to the centre tap of the 18vct heater supply. It looks like this would produce rails of 60v+12.7v and 60v-12.7v to feed in to the heater regs.
Is this essentially a 2x9v transformer?
Im not quite sure how you would wire this.
Va
0V
Vb
0v
For a dual rail supply you would tie 0v and vb together to give ground. Is this the same as a centre tap and so you can do all the usual tricks with it?
I sent out for some boards -- $10 for a pair. Shipping in the US $6, ROW $9. In respect of SY's IP, these are essentially being sold at cost.
They measure 8" x 2". The transformers will have to be mounted off the board -- because there are so many different varieties.
I also have some very nice Cinemag MC step up transformers.
They measure 8" x 2". The transformers will have to be mounted off the board -- because there are so many different varieties.
I also have some very nice Cinemag MC step up transformers.
