| alexmoose |
| Does anyone know of a good tube phono pre-amp that is DIY? and preferably cheap? because I am going to try and build a stereo that is transistorless! and it is only possible if i get a tube phono preamp. Any help is extremly welcome |
|
|
| arnoldc |
| Find Kuei Yang Wang's post on El Cheapo phono stage. A couple of member have built it. |
|
|
| Miniwatt |
This one's supposed to be pretty good:
To be found on www.triodedick.com (Dutch only -check 'projects') |
|
|
| SRMcGee |
Alexmoose:
Bottlehead offers the Seduction phono preamp. I don't have one, but their Foreplay preamp was a terrific project and sounds too good to be true.
Regards,
Scott |
|
|
| audiohead |
| The cathode resistor of the first mu follower stage is missing! |
|
|
| Shoog |
"Find Kuei Yang Wang's post on El Cheapo phono stage. A couple of member have built it."
I built this and its great.
Shoog |
|
|
| alexmoose |
| quote: | Originally posted by Shoog
"Find Kuei Yang Wang's post on El Cheapo phono stage. A couple of member have built it."
I built this and its great.
Shoog |
I think I found it
http://www.diyaudio.com/forums/show...p?postid=335624
Here
This is the schematic
is this the illustrious "El Cheapo phono stage"? |
|
|
| KevinTams |
| quote: | Originally posted by alexmoose
is this the illustrious "El Cheapo phono stage"? |
It's the valve El Cheapo, there is an opamp El Cheapo version.
I've built the valve El Cheapo and am well pleased with it. There is another thread started by Kofi Anan with a lot of detail on the build particularly the earthing. I found that I needed to build the psu separate from the stage as there was too much noise, but I am using a v.low output cartridge.
Kev |
|
|
| arnoldc |
| That's it alex, on my way to build mine too. |
|
|
| alexmoose |
Okay, I have identified the "El cheapo" (whoever dubded it that needs a metal) However being a nube to tubes, I of course have some questions that will make me look like an idiot.
What does the number mean after the resistor value in some of the resitors for example 51k1 (bottom left corner) does this imply 1 watt? resistor with a value of 51k ohms?
How much current do you think this needs? because the Hammond 269 JX provides 250v (the B+ on the schem) at 60ma for a modest $33.95 from Tubes and more is this enough?
What does the capacitor labeled "2u(mew)2" (middle right) mean? I understand way by which capacitors are rated, but what does that mean?
What does "MKP" mean?
What does "KP-SN" mean? |
|
|
| arnoldc |
| quote: | Originally posted by alexmoose
Okay, I have identified the "El cheapo" (whoever dubded it that needs a metal) However being a nube to tubes, I of course have some questions that will make me look like an idiot.
What does the number mean after the resistor value in some of the resitors for example 51k1 (bottom left corner) does this imply 1 watt? resistor with a value of 51k ohms?
How much current do you think this needs? because the Hammond 269 JX provides 250v (the B+ on the schem) at 60ma for a modest $33.95 from Tubes and more is this enough?
What does the capacitor labeled "2u(mew)2" (middle right) mean? I understand way by which capacitors are rated, but what does that mean?
What does "MKP" mean?
What does "KP-SN" mean? |
Hi Alex,
51k1 = 51.1K resistor
2u2 = 2.2uF capacitor
MKP is a type of film capacitor, Polypropelene, like Vishay, Epcos, or the more exotic ones.
KP-SN is a type of film capacitor, Tin Foil, like Audyn-Cap
I'm posting the PSU that KYW suggests, below
I'm going to use the cheap Illinois Caps for mine, except for the 2.2uF (2u2) in which I'll use Mundorf Supreme (because they're relatively cheap here in the Philippines). Farnell and RS Components pricing here is unbelievable, more expensive than botique parts such as Jensen, AuriCap, MultiCap. |
|
|
| J Epstein |
??What does the number mean after the resistor value in some of the resitors for example 51k1 (bottom left corner) does this imply 1 watt? resistor with a value of 51k ohms???
51.1 k (put the decimal point in the place of the order of magnitude signifier). The history behind this practice is that, back in the days before digital copying was the norm, decimal points often disappeared from a photocopy, but letters usually didn't.
??How much current do you think this needs? because the Hammond 269 JX provides 250v (the B+ on the schem) at 60ma for a modest $33.95 from Tubes and more is this enough? ??
60 mA is plenty for this phono preamp: each triode section would draw in the single digits of mA, the whole thing should draw less than 25 mA from the B+ rail.
??What does the capacitor labeled "2u(mew)2" (middle right) mean? I understand way by which capacitors are rated, but what does that mean???
2.2 uF (2.2 microFarads).
??What does "MKP" mean? What does "KP-SN" mean? ??
These are designators for capacitor types, MKP = metallized polypropylene film, KP-SN = polypropylene and tin foil. |
|
|
| alexmoose |
What does the data mean on your attatchment? it looks like something useful, and pretty **** cool |
|
|
| arnoldc |
By the way Alex, not to confuse you but, I found the suggested rectifier, the 6X4 noisy on my 12B4 preamp. I replaced it with 5Y3 and it's silent. However, I don't like the huge voltage drop with the 5Y3.
Recently, I've had very good successes with solid state :smash: (i know, i know) recitification on my preamps. They are silent, way cooler, smaller (i like nice, small chassis). I'm planning to use the attached schema which I pulled out from HeadWize. Just ignore the relay stuff...
EDIT: Sorry, haven't had morning coffee yet. The suggested rectifier is EZ80 and *not* 6X4 as I posted. |
|
|
| arnoldc |
| quote: | Originally posted by alexmoose
What does the data mean on your attatchment? it looks like something useful, and pretty **** cool |
Hi Alex,
that's the simulation result from the PSU Designer II software, which most of use use to prototype power supplies.
It shows the voltages along each stage of the power supply. If you have the software, you can check the "ripple" (noise) by zooming in on one of the lines. |
|
|
| alexmoose |
I have no inhabition toward using a SS recitfier, it just seems a little more practical. Is there any real advantage using a tube rectifier? other than the fact that alot of them look really cool?
Arnoldc, could you explain the data thats in the attatchment from the previous post? the graph, showing the suggested power supply, I am very close to understanding it, however I am not sure, please enlighten me |
|
|
| alexmoose |
haha, hows that for bad timing!
so the graph shows the voltage vs time graph of the various stages of the Power supply right? so depending on what capacitor you place your lead into B+ next to, you get a different voltage? |
|
|
| arnoldc |
The numeric results on the left pane shows the simulated voltages at each stage - "Max" column.
I really like this software so much, and the simulated values are always close to the real world values. I use it in all my projects, whether SS or tube rectification. ;)
EDIT:
he he, you're fast... :D
Changing the capacitance does not change the voltage but will have an effect on the ripple. If you want to play around with the resulting voltage, you can change the R.
Another EDIT:
The 10uF first capacitor is sized according to the maximum capacitance limit of the tube rectifier, the EZ80 in this case. Each tube rectifier will have a different capacitance limit for a cap-input supply, like this.
I ditched, the EZ80 and 10uF, replaced it with FR107 and power transformer is 280V I think, in one of my projects. |
|
|
| alexmoose |
I have now downloaded, it, and I am having a good time playing with it (when its in the computer, I can't shock myself and die!)
| quote: | | EDIT: Sorry, haven't had morning coffee yet. The suggested rectifier is EZ80 and *not* 6X4 as I posted. |
Its okay, I had my morning coffee 13 hours ago! |
|
|
| alexmoose |
| How much ripple am I aloud to have in the power supply for this preamp? in percentage |
|
|
| arnoldc |
| Ripple is measured in milliVolts, and you should be aiming for as low as possible. Thorsten aka KYW suggested it will be 0.1mV IIRC. |
|
|
| Shoog |
I have 5 stages of RC filtering and still have residual hum, its just not bad enough to track down.
Shoog |
|
|
| reinhard |
5 stages of RC says nothing. What Rīs, what Cīs.
bridge rectifier? How much current?
Buy Morgan Jones "Valve amplifiers", ther are simple formulas
to get the ripple down with RC stages,
Reinhard |
|
|
| knubie |
Morgan Jones shows several examples among them a 4 stage RC circuit, where he uses a total of 2k in resistors aka 4 X 500ohms.
What I didn't understand is how he got that number, what seems to be a default or recommended value of the value of resistors in RC filtering. Of course the higher the value, the better ripple rejection but also higher voltage drop and higher output resistance. MJ doesn't discuss this....
Phono stages could probably use more resistance, but how about a output stage?
Knubie |
|
|
| Shoog |
"5 stages of RC says nothing. What Rīs, what Cīs.
bridge rectifier? How much current?
Buy Morgan Jones "Valve amplifiers", ther are simple formulas
to get the ripple down with RC stages,"
El Cheapo Valve phone.
100uf, 100R, 100uf, 100R, 100uf, 100R 100uf, 100R, 100uf, 100R 100uf 1uf
The 5 stages are adequate for the job. On phono stages tiny things can cause significant hum issues - after a certain point though it becomes more and more difficult to track down the last little bit of hum, and the effort just isn't worth it. I can live with the small amount of residual hum, its only really an issue when listening on headphones.
Another user may think any hum unacceptable.
Shoog |
|
|
| alexmoose |
What is the advantage of using a Bridge rectifier (four diodes) v a full-wave rectifier (two diodes)? I ask this because the change in cost from one to the other is nill and if one is far superior i'll use that one.
This project is more or less on the back burner of my DIY stove (The amplifier being front, and center) However, I deeply value all of the advice, and the knowladge that I have learned through this thread. |
|
|
| kevinkr |
Just one of several conventions for labeling parts commonly used here and abroad.
The multiplier takes the place of the "." in the component value.
For example:
51K1 is equivalent to 51.1K which is a standard 1% value in the E96 range.
For values below 1K substitute R instead, so 10.0 ohms for example becomes 10R0, while 100 ohms becomes 100R.
2u2 is the same as 2.2uF
MKP is simply a type of film capacitor. You can use any film type you like as long as tolerance, value, and voltage are suitable.
Etc. |
|
|
| Kuei Yang Wang |
Konnichiwa,
| quote: | Originally posted by Shoog
El Cheapo Valve phone.
100uf, 100R, 100uf, 100R, 100uf, 100R 100uf, 100R, 100uf, 100R 100uf 1uf
The 5 stages are adequate for the job. On phono stages tiny things can cause significant hum issues - after a certain point though it becomes more and more difficult to track down the last little bit of hum, and the effort just isn't worth it. I can live with the small amount of residual hum, its only really an issue when listening on headphones. |
Using a 100R resistor instead of my originally specified 1K moves the "Corner" frequency for each RC cell up a decade. Each 1K & 100u RC cell will have a corner frequency of < 2Hz, so 20Hz will be reduced by 20db and 100Hz by 34db, per cell.
Using 100R/100u moves the corner frequency to around 20Hz and at 100Hz only by around 16db. So in 5 cells you loose around 90db filtering at 100Hz compared to my original circuit.
With 10u input capacitor the ripple is in the region of 10V. Your circuit will attenuate this by a factor of 10,000 to around 1mV, my original one will (theoretically) kill the 10V ripple by a factor of 40,000,000,000,000, in other words any junk from the mains and hum will be theoretically dropped well into the picovolt range (three orders of magnitude lower).
With real capacitors the amount of attenuation is less due to parasitic resistive and inductive behaviour so we probably "only" get noise down into fractional milli to microvolt, which I think is good enough for government work.
So, see if you can find yourself some extra volts on that transformer of yours and up the resistors, increasing the capacitor values will also help, you could go 330R/330u and have the same filtering as 1K/100u for 1/3rd of the voltage loss. Or you could stick a choke into the first stage, many options.
I find 100u/450V and 1K resistors exceedingly cheap and hard to mess up....
Sayonara |
|
|
| arnoldc |
I actually used the 1K/100u route posted by Thorsten for my headphone amp and I can tell you I'm pretty surprised at the result. AC feeding the filaments of the tubes, and I get just nearly audible hum (when you're all alone in a very silent room) with this method, volume control at any position.
Makes me think twice about DC heating and my planned MOSFET high voltage regulation for the B+.
I also used the same scheme for mt 12B4 preamp and at 0 volume, it's dead silent (by ear from listening position). I have a problem with my ALPS though as it sort of buzzes a bit at 10 o'clock, 1 o'clock, 3 o'clock positions. |
|
|
| Shoog |
I forgot to mention that I also have a quite large choke as the second stage. The transformer can't supply any more voltage so a new transformer would be the only way to kill that last bit of supply hum. My main point though is that there are other sources of hum and sometimes nothing short of a complete rebuild will nail those.
I'am real anti DC heaters. Its a rare circuit that really needs them. A phono amp is one of those rare instances. There are enough anicdotes out there saying that AC sounds better to pay attention. These things are designed for AC so why some audiobuff thinks it needs DC is beyond me. There are some valves that are prone to heater hum pickup (5687 springs to mind) and there DC heaters are called for.
Shoog |
|
|
| fred76 |
Hi,
I reduced the caps to 50uF in my sim and have an LC after the input cap (reduced to 6.8uF). I'm not sure if this will decrease ripple rejection by much even if the R's are now sliglty higher at 1.2k. |
|
|
| Giaime |
| quote: | Originally posted by arnoldc
Makes me think twice about DC heating and my planned MOSFET high voltage regulation for the B+.
|
Already done ;)
http://giaime.altervista.org/mypreamp.html
scroll down the page for a Mosfet regulated B+, a nice phono stage and a nice linestage. |
|
|
| arnoldc |
| Hi Giaime, I actually visit your site from time to time and I've considered that design of yours. What component values do I have to change for output other than 220V? The other one I'm considering used a string of zeners to set the output voltage which to me is easier (I'm lazy :smash: ) |
|
|
| EC8010 |
| Giame, some of your horizontal lines don't show up on my computer! |
|
|
| SY |
| quote: | Originally posted by EC8010
Giame, some of your horizontal lines don't show up on my computer! |
I found that true for the thumbnails, but clicking on the pictures to view full-sized cured all. |
|
|
| Giaime |
| quote: | Originally posted by arnoldc
Hi Giaime, I actually visit your site from time to time and I've considered that design of yours. What component values do I have to change for output other than 220V? The other one I'm considering used a string of zeners to set the output voltage which to me is easier (I'm lazy :smash: ) |
Hello, thank you very much for the interest ;)
You have to change R7. Watch out for dissipation!!!! Don't put a trimmer there, it will burn. Try with fixed resistors of at least 2W rated dissipation. I'm using 3 1/2W resistors and they get very hot.
And... a note for everybody: not ALL of the circuits posted in my website sound good. All works, but they're not great. As you can see, I'm developing better circuits :D Last ones are my definitive, they sound so good especially the linestage. |
|
|
|
