Ok
We have the perfect starter preamp circuit here. Lets assume we want to build it ti the hilt. What parts where and why would you do so. Lets assume we are going to use a 360-0-360 transformer and a 5R4GYA rect tube.
I'm going to build this one up with a slight variation .. I'm going to use 1 12ay7 tube for each side and a Red Base 6SN7 (5692) tubes. One side I will build up with cheap .50 ea resistors(metalfilm) and the other side I will use Riken at 3.50 ea. One side gets cheap caps the other gets better(remember I can't afford caps at $100.00 ea here).
I would like the suggestions that you may have to build the other side to suite your taste.
I will then listen to it and test it to see if I can hear a difference. I will then assemble a group of individuals to listen and compare without disclosure of parts used. I think this might be a fair way to test. I would even ship this to different individuals for their evaluation.
Joe
We have the perfect starter preamp circuit here. Lets assume we want to build it ti the hilt. What parts where and why would you do so. Lets assume we are going to use a 360-0-360 transformer and a 5R4GYA rect tube.
I'm going to build this one up with a slight variation .. I'm going to use 1 12ay7 tube for each side and a Red Base 6SN7 (5692) tubes. One side I will build up with cheap .50 ea resistors(metalfilm) and the other side I will use Riken at 3.50 ea. One side gets cheap caps the other gets better(remember I can't afford caps at $100.00 ea here).
I would like the suggestions that you may have to build the other side to suite your taste.
I will then listen to it and test it to see if I can hear a difference. I will then assemble a group of individuals to listen and compare without disclosure of parts used. I think this might be a fair way to test. I would even ship this to different individuals for their evaluation.
Joe
PREAMP+PARTS
Hi,
Joe,I would advise against that.It would be a waste of time IMO.
Why not build with off the shelf components at first,get to know the sound of the preamp and later on change some components.
For example:first change the coupling caps,later on some resistors and take it from there if you like what you're hearing.
You can then build several samples with several stages of changed components if you like and have people listen to that.
Cheers,
Hi,
Joe,I would advise against that.It would be a waste of time IMO.
Why not build with off the shelf components at first,get to know the sound of the preamp and later on change some components.
For example:first change the coupling caps,later on some resistors and take it from there if you like what you're hearing.
You can then build several samples with several stages of changed components if you like and have people listen to that.
Cheers,
With the following changes to Joels original power supply what would my output voltage be?
Transformer changed to 360-0-360
First resistor changed to 1k (before the 100mfd cap)
Rectifier tube changed to a 5AR4
Granted the current draw for the tubes will be 20ma for each 5692 tube and 8ma for each of the two 12ay7 tubes for a total of 56ma.
Second
Transformer still 360-0-360
1ft resistor still 1k
Rectifier tube changed to 5R4GYA
Why the stupid questions?
Because I don't know what the voltage difference will be between the different tubes.
Why the 360-0-360 transformer? Because I got it cheap and that meant I could spend more money on the tubes.
Why not follow the given directions? Because I wouldn't learn from it.
Joe
Joe
Transformer changed to 360-0-360
First resistor changed to 1k (before the 100mfd cap)
Rectifier tube changed to a 5AR4
Granted the current draw for the tubes will be 20ma for each 5692 tube and 8ma for each of the two 12ay7 tubes for a total of 56ma.
Second
Transformer still 360-0-360
1ft resistor still 1k
Rectifier tube changed to 5R4GYA
Why the stupid questions?
Because I don't know what the voltage difference will be between the different tubes.
Why the 360-0-360 transformer? Because I got it cheap and that meant I could spend more money on the tubes.
Why not follow the given directions? Because I wouldn't learn from it.
Joe
Joe
Joe,
If you have a tube manual handy they have graphs of the voltage drops for each condition - ie. capacitor input, or choke input filters, etc. There's no easy way to figure the numbers, as each circuit draws different amounts of current. Why the high powered rectifiers?
ps. 5AR4's are expensive!
If you have a tube manual handy they have graphs of the voltage drops for each condition - ie. capacitor input, or choke input filters, etc. There's no easy way to figure the numbers, as each circuit draws different amounts of current. Why the high powered rectifiers?
ps. 5AR4's are expensive!
Joel
Santa never brought me a tube manual like I requested so I don't have the graphs and information in which to look the info up.
Secondly, I just happen to bring home several large boxes full of tubes and I happen to find 5Ar4's and 5R4GYA tubes. That is what I have for rectifier tubes at the moment. My first thought was to use what I happen to have. I just thought since you guys deal with tubes all the time that you might have a ballpark idea what I might expect for voltage and hince I could order the correct resistors. Never mind I will wire it up and run it up on the variac and monitor voltages as I go.
Joe
Santa never brought me a tube manual like I requested so I don't have the graphs and information in which to look the info up.
Secondly, I just happen to bring home several large boxes full of tubes and I happen to find 5Ar4's and 5R4GYA tubes. That is what I have for rectifier tubes at the moment. My first thought was to use what I happen to have. I just thought since you guys deal with tubes all the time that you might have a ballpark idea what I might expect for voltage and hince I could order the correct resistors. Never mind I will wire it up and run it up on the variac and monitor voltages as I go.
Joe
I am still gathering parts to build this project. I have managed a set of RCA 5692 JAN tubes and I am wondering if the safe plate voltage on these is less than that of a normal 6SN7. I happened to read an article on a 6SN7 that mentioned that if using the 5692 to limit the plate voltage to 275V.
The markings on these tubes are JAN CRC-5692 RCA S C
1768
Joe
The markings on these tubes are JAN CRC-5692 RCA S C
1768
Joe
Tube manuals
Burnedfingers,
Sorry to hear that Santa didn't bring you what you wanted
You can get away without manuals these days; though it's nice to have them.
I don't know about the 5692, but it is lisited in TDSL, available from: http://www.duncanamps.com/
It's free, and contains many links to more detailed data.
Concerning maximum anode (plate) voltage; there is more to it than just reading the figures off the page. In many cases, the valve can be used with an inductive load (choke or transformer) at that voltage. Therefore for a resistive load, that voltage can be doubled.
Of course that doesn't mean that those are optimum working conditions, just that it's safe (as long as maximum dissapation is not exceeded).
Cheers,
Burnedfingers,
Sorry to hear that Santa didn't bring you what you wanted
You can get away without manuals these days; though it's nice to have them.
I don't know about the 5692, but it is lisited in TDSL, available from: http://www.duncanamps.com/
It's free, and contains many links to more detailed data.
Concerning maximum anode (plate) voltage; there is more to it than just reading the figures off the page. In many cases, the valve can be used with an inductive load (choke or transformer) at that voltage. Therefore for a resistive load, that voltage can be doubled.
Of course that doesn't mean that those are optimum working conditions, just that it's safe (as long as maximum dissapation is not exceeded).
Cheers,
5692
Hi,
That is the maximum voltage measured directly at the plate.
If you need a datasheet for the Red October range :
http://www.audiohot.com/frank/sheets/084/5/5691.pdf
For a bog standard 6SN7 that would be 300V max on the plate.
Cheers,
Hi,
That is the maximum voltage measured directly at the plate.
If you need a datasheet for the Red October
range :http://www.audiohot.com/frank/sheets/084/5/5691.pdf
For a bog standard 6SN7 that would be 300V max on the plate.
Cheers,
(with respect to other electrodes)
I was just going to clarify /qualify my original post when I saw Frank's comments.
When I mentioned maximum voltage, I meant supply voltage.
Most resistor loaded circuits operate with the anode at half rail voltage.
Well, this is more of a grey area.
What valves are we talking about here?
Voltage amplifer valves? Power output valves?
I said most, and IMO it is most that can safely run with double voltage on signal peaks.
I finished the preamp last night about midnight. The clarity is out of this world. When used with my garage amp( Marantz M-240 may god forgive me) it resulted in a very pleasing sound. I do have a small problem, for some reason I seem to have a humming Bast**d. I used 2 12AY7 tubes, half for each channel and I used a 360-0-360 transformer which I had to adjust voltage drop in order to achieve slightly less than 250V at the plate of the 6SN7(soon to be 5692 when the bugs are ironed out). I had to use a ground bar to get all the grounds on instead of one star point, is this where my problem is?
Joe
Joe
Hi Frank
The heaters are AC for the 12AY7's and 6SN7's. The input and output RCA jacks are isolated from the chassis and have a ground connection coming from the ground bus. The heater wires are kept close to the chassis and away from signal wires. On turn on the voltage surges above the 300v mark until the tube/heaters warm up? The plate voltage is then stable at around 245 at the plate. Chassis is grounded at one end.
Joe
The heaters are AC for the 12AY7's and 6SN7's. The input and output RCA jacks are isolated from the chassis and have a ground connection coming from the ground bus. The heater wires are kept close to the chassis and away from signal wires. On turn on the voltage surges above the 300v mark until the tube/heaters warm up? The plate voltage is then stable at around 245 at the plate. Chassis is grounded at one end.
Joe