Sy,
So the basic approach would be to set up an attenuator circuit ala your figure 2, but can't I get petty close by comparing the datasheets of softer and lundahl? i am not sure how to adjust the 6k8 resistor, by comparing the two, any suggestions?
After thinking about it a bit, I think i get the floating balanced input from the tonearm, I have a nice old denon 103, but would like to accommodate a denon 103r as well or even better.
I am in, if someone wants to have some boards made, including Sy's regulators would be my preference.
The 21' maida's seem like really nice but maybe a bit too much for my budget, anyway I could go either way, with or w/out the regs on the board. I will probably build a tubed rectifier HV supply since i already have the parts.
Instead of over spending on the regs I'd like to consider spending too much on an LCR passive network, has anyone tried this the tango/hashimoto's for example? wouldn't there be a some objective advantages maybe, greater accuracy? I guess i not sure about the functioning of R1 in the eq circuit.
So the basic approach would be to set up an attenuator circuit ala your figure 2, but can't I get petty close by comparing the datasheets of softer and lundahl? i am not sure how to adjust the 6k8 resistor, by comparing the two, any suggestions?
After thinking about it a bit, I think i get the floating balanced input from the tonearm, I have a nice old denon 103, but would like to accommodate a denon 103r as well or even better.
I am in, if someone wants to have some boards made, including Sy's regulators would be my preference.
The 21' maida's seem like really nice but maybe a bit too much for my budget, anyway I could go either way, with or w/out the regs on the board. I will probably build a tubed rectifier HV supply since i already have the parts.
Instead of over spending on the regs I'd like to consider spending too much on an LCR passive network, has anyone tried this the tango/hashimoto's for example? wouldn't there be a some objective advantages maybe, greater accuracy? I guess i not sure about the functioning of R1 in the eq circuit.
The data sheet will not get you far. Adjusting it properly isn't very hard and only takes a generator and scope, from start to finish, just a few minutes. Make sure you either use a 10x probe or if you use a 1x, take its capacitance into account. You can use a potentiometer to stand in for the fixed resistor to determine optimum value. There's a really nice treatment of this on Sowter's 8055 web page.
I'm used a modified 103R with this preamp and got excellent results. The 103 is harder to get to play nicely with step up transformers.
Like I said, the regulators aren't critical, you can go either way, whatever's easier.
There is absolutely no engineering advantage to using LCR instead of plain old RC. Spend the money on music.
I'm used a modified 103R with this preamp and got excellent results. The 103 is harder to get to play nicely with step up transformers.
Like I said, the regulators aren't critical, you can go either way, whatever's easier.
There is absolutely no engineering advantage to using LCR instead of plain old RC. Spend the money on music.
SY said......
SY said:
"In light of Merlin Blencowe's excellent JAES paper on tube noise, I'll be lowering the plate currents of the first and second stages. It won't change the performance significantly, but it will reduce heat and probably extend tube life."
I'm just getting back to completing Jack's boards after a long (long) hiatus so are there any suggestions to new lower current operating points for the first and second stages that I can incorporate at this belated building stage?
Thanks
tim
PS Thank you Jack for the PCBs
SY said:
"In light of Merlin Blencowe's excellent JAES paper on tube noise, I'll be lowering the plate currents of the first and second stages. It won't change the performance significantly, but it will reduce heat and probably extend tube life."
I'm just getting back to completing Jack's boards after a long (long) hiatus so are there any suggestions to new lower current operating points for the first and second stages that I can incorporate at this belated building stage?
Thanks
tim
PS Thank you Jack for the PCBs
Just an update, Sowter has ceased production of the 8055 step-up transformer and replaced it with the 1480. The data sheet is here:Sowter Type 1480 Studio cartridge transformer
Note that with this new model, the winding resistance has dropped on both the primary and secondary. It is now spec'd at .29 and 60 Ohms, respectively vs the .72 & 102 Ohms of the 8055 model.
Note that with this new model, the winding resistance has dropped on both the primary and secondary. It is now spec'd at .29 and 60 Ohms, respectively vs the .72 & 102 Ohms of the 8055 model.
SY:
I need 15 feet of XLR cable between output of HMN and input of Impasse Preamp. Choices are:
1. Mogami 2534
http://www.mogamicable.com/category/bulk/microphone/quad/
2. Belden 1800F (low capacitance)
http://www.belden.com/techdatas/metric/1800F.pdf
3. Canare L-4e6s "star quad" (higher capacitance, higher noise rejection)
http://www.canare.com/ProductItemDisplay.aspx?productItemID=53
4. Other?
What should I be looking for when choosing a cable?
I need 15 feet of XLR cable between output of HMN and input of Impasse Preamp. Choices are:
1. Mogami 2534
http://www.mogamicable.com/category/bulk/microphone/quad/
2. Belden 1800F (low capacitance)
http://www.belden.com/techdatas/metric/1800F.pdf
3. Canare L-4e6s "star quad" (higher capacitance, higher noise rejection)
http://www.canare.com/ProductItemDisplay.aspx?productItemID=53
4. Other?
What should I be looking for when choosing a cable?
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For a short 15 foot cable almost any Shielded Twisted Pair (STP) will do. For longer cables (say approaching 300 feet) you want a cable made by a major bulk cable manufacture. The two signal conductors need to remain symmetrical in respect to the shield for the length of the cable. (it's about Shield Current Induced Noise)(SCIN).
Mogami, Belden & Canare are all good major bulk cable manufactures.
Star Quad cables are good in harsh electrical noise environments. (think theater lighting systems)
Mogami, Belden & Canare are all good major bulk cable manufactures.
Star Quad cables are good in harsh electrical noise environments. (think theater lighting systems)
I had about 50 of the big boards made up over 6 years ago. These include two regulated power supplies, the DC heater/lifter and transformers all on one. They were somewhat expensive, and i didn't like the necessity of cutting them by hand with a tile cutter or band saw.
Here's an idea for a board which just encompasses the input and buffer circuits. Will cost me about $4.80 each including shipping and fees if I have 100 made. You'll have to mount the input transformer separately.
