Hi,
Do you happen to have the model # for those xformers?
Either way, 14V is fine.
No need for a center tap, it needs to be capable of supplying about 500mA.
If it should have a CT just leave it unconnected.
The 7812 comes in a TO220 package, I usually go for the 1A version even if I don't need to supply that amount of current.
The cap behind the 7812 reg. doesn't have to be that big either but must be an electrolytic type.
Use one xformer per channel.
The 1K resistor and (green) LED aren't necessary either. They just serve as a visual clue for when the unit is on in case the chassis is closed and tubes aren't visible.
Here's a sample diagram:
Cheers,😉
Do you happen to have the model # for those xformers?
Either way, 14V is fine.
No need for a center tap, it needs to be capable of supplying about 500mA.
If it should have a CT just leave it unconnected.
The 7812 comes in a TO220 package, I usually go for the 1A version even if I don't need to supply that amount of current.
The cap behind the 7812 reg. doesn't have to be that big either but must be an electrolytic type.
Use one xformer per channel.
The 1K resistor and (green) LED aren't necessary either. They just serve as a visual clue for when the unit is on in case the chassis is closed and tubes aren't visible.
Here's a sample diagram:
Cheers,😉
Attachments
6SN7 from a friend...
Frank,
A friend of mine will be giving me his spare 6SN7s and would love to build your preamp. I know the 5U4G is overkill but that is what I already have and wanted to use it if possible. I also have a trafo with 300-0-300 200mA, 0-5 3A, 6-0-6 2A secondaries.
Is this schematic still the latest? I ask because you may have changed part values and all. I know the 0.033 should read 0.33uf part. 🙂
What are the wattage of the resistors?
Frank,
A friend of mine will be giving me his spare 6SN7s and would love to build your preamp. I know the 5U4G is overkill but that is what I already have and wanted to use it if possible. I also have a trafo with 300-0-300 200mA, 0-5 3A, 6-0-6 2A secondaries.
Is this schematic still the latest? I ask because you may have changed part values and all. I know the 0.033 should read 0.33uf part. 🙂
What are the wattage of the resistors?
Attachments
Hi,
Actually, the 0.033µF cap should be fine already. I had completely overlooked the feedback mechanism of the CF making the input impedance much higher than the resistor values suggest.
Eiher way the bigger one won't hurt either and to make ordering components easier you can just as well use the same value as the cap on the input of the circuit, namely 0.047µF.
If you're using an attenuator iso of the volpot you can ommit the input cap. Just be sure the source connected to it has no DC offset.
For best soundquality I'd recommend 2W metalfilm, the 1M gridleaks can ofcourse be 1/4 Watt, they don't see any current to speak of.
Cheers, 😉
Actually, the 0.033µF cap should be fine already. I had completely overlooked the feedback mechanism of the CF making the input impedance much higher than the resistor values suggest.
Eiher way the bigger one won't hurt either and to make ordering components easier you can just as well use the same value as the cap on the input of the circuit, namely 0.047µF.
If you're using an attenuator iso of the volpot you can ommit the input cap. Just be sure the source connected to it has no DC offset.
For best soundquality I'd recommend 2W metalfilm, the 1M gridleaks can ofcourse be 1/4 Watt, they don't see any current to speak of.
Cheers, 😉
Thanks for your time Frank!
Can I not regulate the HT supply? I will use 2 30H chokes to make a CLCLCRC supply. Also I will regulate my heaters (it seems I'm good at regulating heaters 😀 ).
The only high quality 2W resistors available in this side of the earth are Rikens. Also, I already have 4 pcs of 0.47uf mkp caps (those yellow ones like auricaps) and can I use them for the input and coupling caps? I also have the tube sockets just like what you suggest on another thread. I also plan on including some personal touches.
I'm pretty excited with this project and since this has been titled your "ultimate" preamp, I would like to take it slow and make this my "ultimate" preamp build. 😀
Can I not regulate the HT supply? I will use 2 30H chokes to make a CLCLCRC supply. Also I will regulate my heaters (it seems I'm good at regulating heaters 😀 ).
The only high quality 2W resistors available in this side of the earth are Rikens. Also, I already have 4 pcs of 0.47uf mkp caps (those yellow ones like auricaps) and can I use them for the input and coupling caps? I also have the tube sockets just like what you suggest on another thread. I also plan on including some personal touches.
I'm pretty excited with this project and since this has been titled your "ultimate" preamp, I would like to take it slow and make this my "ultimate" preamp build. 😀
Hi,
You certainly can.
If you have only two chokes available I suggest building something similar to what I advised here:
SEMI DUAL MONO PS
By doing so each channel will see its own filtered and choke regulated supply. The VR tubes are an option but you'll need to keep in mind that you'll need to drop some volts in order to make the VRs work.
Instead of a CLC supply I'd recommend a LC supply, a small cap after the tube rectifier (assuming you'll be using one) can be used to fine tune the exact voltage you'll need by either making the cap smaller or larger as needed.
Those are excellent resistors but if you need to cut costs you can use a 2W Riken for the plate R of the first tube only. Others can be 1W, either metalfilm or carbon film for as long as their leadout wires are non-magnetic you'd be fine.
Certainly. Just make sure their insulation is rated for about 400VDC to be safe.
Cheers,😉
You certainly can.
If you have only two chokes available I suggest building something similar to what I advised here:
SEMI DUAL MONO PS
By doing so each channel will see its own filtered and choke regulated supply. The VR tubes are an option but you'll need to keep in mind that you'll need to drop some volts in order to make the VRs work.
Instead of a CLC supply I'd recommend a LC supply, a small cap after the tube rectifier (assuming you'll be using one) can be used to fine tune the exact voltage you'll need by either making the cap smaller or larger as needed.
Those are excellent resistors but if you need to cut costs you can use a 2W Riken for the plate R of the first tube only. Others can be 1W, either metalfilm or carbon film for as long as their leadout wires are non-magnetic you'd be fine.
Certainly. Just make sure their insulation is rated for about 400VDC to be safe.
Cheers,😉
Thanks Frank!
Very quick response indeed! The Rikens cost about US$1.50 here. I have skipped enough meals to save for Rikens (I've been planning on building your ultimate pre for months), I'll just use 1/4W metalfilm resistors on the 1M resistors you recommend.
So my Riken resistor lists should be...
47K - 2pcs
1.5K - 2pcs
220K - 2pcs
820R - 2pcs
10K - 2pcs
and
4pcs 1M-1/4W metalfilm resistors
Oh the 0.47uf are 630V types so are safe for use.
Very quick response indeed! The Rikens cost about US$1.50 here. I have skipped enough meals to save for Rikens (I've been planning on building your ultimate pre for months), I'll just use 1/4W metalfilm resistors on the 1M resistors you recommend.
So my Riken resistor lists should be...
47K - 2pcs
1.5K - 2pcs
220K - 2pcs
820R - 2pcs
10K - 2pcs
and
4pcs 1M-1/4W metalfilm resistors
Oh the 0.47uf are 630V types so are safe for use.
Hi,
If it pays for another meal 😉 these resistors can be 1/4W metalfilm as well:
220K - 2pcs
Cheers,😉
If it pays for another meal 😉 these resistors can be 1/4W metalfilm as well:
220K - 2pcs
Cheers,😉
Frank,
Guess I'll be using other resistors for 1.5K and 820R because no Rikens available for that values. Only 1K, 680R are available values that are close for the Riken.
Also the 47K Riken is only 1W
Available 2W Rikens are 24K, 27K, and 68K only.
Guess I'll be using other resistors for 1.5K and 820R because no Rikens available for that values. Only 1K, 680R are available values that are close for the Riken.
Also the 47K Riken is only 1W
Available 2W Rikens are 24K, 27K, and 68K only.Frank could you tell me which transformer from the link above is suitable. Also, what value fuse would i need for each psu for 120V AC?
Hi,
From the Hammond catalogue the 167N14 seems the best suited for your needs.
Overkill actually, but probably the easiest way to go for you.
On the mains side a 1.5 A slowblow fuse should do nicely.
Do you plan on using two physically separate PSUs, each having a dedicated powercord?
Cheers, 😉
From the Hammond catalogue the 167N14 seems the best suited for your needs.
Overkill actually, but probably the easiest way to go for you.
On the mains side a 1.5 A slowblow fuse should do nicely.
Do you plan on using two physically separate PSUs, each having a dedicated powercord?
Cheers, 😉
Either way will work for the power chords. If i wanted a true monoblock, i may go with two. Do you think it matters much?
Hi Frank,
If one is building the ecl85 version regulated supply, what is the max current that this can supply, I was thinking of building another cd ouput stage using that circuit, and just wanted to know what kind of current draw I'm limited to?
Thanks
Raja
If one is building the ecl85 version regulated supply, what is the max current that this can supply, I was thinking of building another cd ouput stage using that circuit, and just wanted to know what kind of current draw I'm limited to?
Thanks
Raja
Hi,
You'd be cruising at about 50mA per regulator easy.
Far more than you'd need for CD outputstage I suppose.
Cheers,😉
You'd be cruising at about 50mA per regulator easy.
Far more than you'd need for CD outputstage I suppose.
Cheers,😉
Cheers Frank,
Well I've searched the tube database for alternatives to the 3a5's, which I used before. Though I'm not sure I can better them in any way. I used remco's cd enhancer II, and managaed to completeley remvove the passives from the stage and ended up with a very pleasing sound. The 3a5's had enough input resistence for the dac's to drive directly. Plus the opt's have enough roll-off to offer filtering at 100khz. So Frank do you know of any other interesting triodes, that could be used? Obviously one or 2 changes may be needed, I have considered 6922 or 6h30pi, but I don't know what the plate resistence is........
I have emailed Remco also to see what he can offer, on his site it did say he was considering 5657, but looking at the specs that doesn't seem too different from the 3a5's.
Failing all this I'm very happy just to live with the 3a5's if nothing alternative shows up........
Thanks
Raja
Well I've searched the tube database for alternatives to the 3a5's, which I used before. Though I'm not sure I can better them in any way. I used remco's cd enhancer II, and managaed to completeley remvove the passives from the stage and ended up with a very pleasing sound. The 3a5's had enough input resistence for the dac's to drive directly. Plus the opt's have enough roll-off to offer filtering at 100khz. So Frank do you know of any other interesting triodes, that could be used? Obviously one or 2 changes may be needed, I have considered 6922 or 6h30pi, but I don't know what the plate resistence is........
I have emailed Remco also to see what he can offer, on his site it did say he was considering 5657, but looking at the specs that doesn't seem too different from the 3a5's.
Failing all this I'm very happy just to live with the 3a5's if nothing alternative shows up........
Thanks
Raja
Hi,
Raja,
If you're happy with the improvement the valve outputstage I'd leave it as it is and rather look at improving the DAC itself:
Perhaps a few tweaks could lift it to a new level?
I'm thinking about better caps, Oscon, Black Gate come to mind and maybe a better clock a la Guido Tent's XO2 to reduce jitter....
Knowing the designer of your DAC by reputation and a couple of e-mail exchanges I think he already extracted 99% of the performance improvement such an add-on stage can bring.
Changing it to take a different type of valve will require a total redesign, bring a different sonic fingerprint with it, one that may or may not be symbiotic with your current system and personal taste.
What circuit is it you have in mind exactly anyway?
Cheers, 😉
Raja,
If you're happy with the improvement the valve outputstage I'd leave it as it is and rather look at improving the DAC itself:
Perhaps a few tweaks could lift it to a new level?
I'm thinking about better caps, Oscon, Black Gate come to mind and maybe a better clock a la Guido Tent's XO2 to reduce jitter....
Knowing the designer of your DAC by reputation and a couple of e-mail exchanges I think he already extracted 99% of the performance improvement such an add-on stage can bring.
Changing it to take a different type of valve will require a total redesign, bring a different sonic fingerprint with it, one that may or may not be symbiotic with your current system and personal taste.
What circuit is it you have in mind exactly anyway?
Cheers, 😉