Source Files download
The picture below shows the max Output voltage before soft clipping in OTL mode under 220 Ohm load per channel, reaching 43 Vrms for 8.3 wattsper channel.
If you are not sure which tube you need, please look at the circuit board and see what is written there (PCL805), or ECL85 (6F5P).
In mid-2015 it has been changed from PCL805 to ECL85 that affects the models of all RKV, Luminare and Solaris.
Description of some technical details ...
The output impedance of Luminare with negative feedback (physical concept: closed loop) is defined as follows.
The control is based on the principle of negative feedback of the open loop gain ( 133 dB ) of the amplifier.
However, since there is a closed loop. Dynamically because the amplifier tries to keep active voltage at the output losses in upright because he
continuously compares its actual value (feedback) to the desired value (signal) and continuously re-adjusts addition, through the entire range.
Example: The OTL mode provides Luminare 1V without load resistance and 0.998 V at 60 ohm load resistor.
From these data it can be calculated easily, that the output impedance of the amplifier for this load resistance 0.12 ohm.
The fact of wanting to determine the output impedance by incorporating the tubes, is simply nonsense.
It's not the tube determines the output impedance, but the overall OTL concept.
This applies to RKV 2 + 3 and Luminare.
The output transformer is not the part of its gain loop.
If you are interested in the circuit design, read the patent in 1982 below.
Tube Rolling is simply stupid in the models RKV, Luminare and Solaris. You can convince yourself by knocking on the tubes, and you will not hear any knocking sounds in the headphones.
Inside the power inlet a fuse can be found as a protection against overload.
For the 117 V version the value of the fuse should be 1 Ampere Slow.
For the 235 V version the fuse is 0,63 Ampere Slow.
In the end I found what I was looking for at Jogi's tube booth , where there is a circuit with two PCL805s (per channel) in push-pull operation (see under Amplifier - PCL 805-Headphone-Amp).
The advantages of this circuit:
Very high output power (mei, as a rocker you just need pressure)
Proven design (originally by Helmut Becker)
No output transformer
Except for the mains transformer and tubes, only standard components
ATTENTION !!
If you want to build and operate this power amplifier, you should know exactly what you are doing. The mains voltage as well as the anode voltage for the output stage tubes (375V) are freely conducted in the device. Improper handling is life-threatening! Even after switching off, you must wait until the electrolytic capacitors are discharged (check with a multimeter) before continuing to work on the device! I am not responsible for any damage caused by the replica!
First construction - we iron a layout!
The schematic was quickly nailed up in Target3001 and turned into a layout.
But stupid: Just when it was time to create the circuit board, I noticed that I had overestimated the capacity of my circuit board store: There were no photo-positive coated circuit boards in the right size. Damn! However, I still had copper-coated circuit boards WITHOUT photoresist, and it occurred to me that I had once read about the "toner transfer method".
The layout is printed out with a laser printer and ironed onto the copper of the circuit board with an iron. Then carefully rub the paper with washing-up liquid and the toner covers the tracks that should remain in place during the etching.
Thomas Pfeifer , for example, has more information on this on his website. What can I say: It worked! Even if the edge sharpness is not the very best and I had to repair one or the other membrane afterwards - it wasn't bad at all for the first time.
Power hungry
The first switch-on - still without the anode voltage connected - went well, the heating of the tubes began to glow, all voltages were within tolerance, so after switching off I activated the anode voltage and switched it on again. Not without an ammeter in between - I probably suspected it: As soon as the tubes come up to temperature, the anode current continues to rise ... So quickly switched off the whole moped again. Then something is probably wrong.
Lo and behold, as soon as the capacitor was installed, the circuit ran, the anode current remained within its limit. To be on the safe side, one last test, signal generator to the input, 330 ohm load resistor and oscillator to the output, and see what the amp does.
KiCAD
To anticipate: it took me some time to get used to the KiCAD version of that time (from 2005) ... First the usual training hurdles until one understood the philosophy of the program, and then there was also the one or other bug that made life difficult for you.
After setting up the amplifier and checking the equipment (the tubes are not yet fitted!)
The circuit board in detail.
Thomas Pfeifer , for example, has more information on this on his website. What can I say: It worked! Even if the edge sharpness is not the very best and I had to repair one or the other membrane afterwards - it wasn't bad at all for the first time.
Power hungry
The first switch-on - still without the anode voltage connected - went well, the heating of the tubes began to glow, all voltages were within tolerance, so after switching off I activated the anode voltage and switched it on again. Not without an ammeter in between - I probably suspected it: As soon as the tubes come up to temperature, the anode current continues to rise ... So quickly switched off the whole moped again. Then something is probably wrong.
The troubleshooting took a lot of nerves, I kept checking the structure, comparing it with the circuit diagram ... nothing!
Everything as it should be.
After another week I was on the verge of giving up the project, but as a last, desperate step I looked at the original layout on Jogi's side and reproduced it with the circuit diagram -
HUPS, there is a capacitor where there is none in the circuit diagram!
Yes, of course, without it the lower tube is at the wrong working point in terms of DC voltage and is fully open!
You could have seen that on the circuit diagram, but sometimes you can't see the forest for the trees ...
Here is the original scheme from Jogi's site with my correction:
Here is the original scheme from Jogi's site with my correction:
In principle it looks good, the signal comes out nicely amplified, but there is a clear hum. This is confirmed by the hearing test with MP3 player and headphones - it works, but it buzzes like a bag of bumblebees ...
Growl
So what to do
We wanted a two-sided layout, with a thick ground plane on one side. Because my guess was that it is a pure mass problem. In addition, the heating cables should be completely removed from the circuit board and wired freely in order to avoid voltage drops across the ground.
Growl
So what to do
We wanted a two-sided layout, with a thick ground plane on one side. Because my guess was that it is a pure mass problem. In addition, the heating cables should be completely removed from the circuit board and wired freely in order to avoid voltage drops across the ground.
The implementation of the layout was not so easy, however: I had to have a two-sided board made, the self-etching was too tricky for me, because the board is quite large and so the congruence of the two layers is difficult.
Since it was the PCBPool Edition, I could only use Target3001 in conjunction with the PCBPool , and the guys are not cheap ...
So I decided to try KiCAD , a free CAD program for circuit board development published under the GPL license.
So I decided to try KiCAD , a free CAD program for circuit board development published under the GPL license.
Circuit board size practically unlimited, lots of free libraries from other users, that sounds really good, doesn't it?
KiCAD
To anticipate: it took me some time to get used to the KiCAD version of that time (from 2005) ... First the usual training hurdles until one understood the philosophy of the program, and then there was also the one or other bug that made life difficult for you.
Fortunately, a lot has happened in the meantime, and today I only use KiCAD in my private life. You have no restrictions with regard to the number of pins, etc., you can generate Gerber files directly and are therefore not tied to a circuit board manufacturer.
Back to the topic - somehow I got the circuit board strapped and after three weeks of waiting it was in my mailbox. I ordered them from LeitOn , which made a good impression and, according to the online calculator , had one of the cheapest prices.
Lo and behold, after "moving" the components from the old circuit board to the new one and running through the commissioning tests again, the first hearing test followed, and the humming was significantly reduced, but unfortunately still not completely gone ...
The breakthrough
The real breakthrough came with a tip from Helmut Weigl , who - independently of me - also shared a replica of the amplifier and also stumbled upon the problem with the missing capacitors.
Back to the topic - somehow I got the circuit board strapped and after three weeks of waiting it was in my mailbox. I ordered them from LeitOn , which made a good impression and, according to the online calculator , had one of the cheapest prices.
Lo and behold, after "moving" the components from the old circuit board to the new one and running through the commissioning tests again, the first hearing test followed, and the humming was significantly reduced, but unfortunately still not completely gone ...
The breakthrough
The real breakthrough came with a tip from Helmut Weigl , who - independently of me - also shared a replica of the amplifier and also stumbled upon the problem with the missing capacitors.
I helped him with the capacitors, and in return he gave me tips on how to reduce the hum. If that is no help among hobbyists - Thank you, Helmut!
The grounding at the inputs of the two operational amplifiers is very important.
The grounding at the inputs of the two operational amplifiers is very important.
There should be a central ground point for each channel, to which the voltage divider from the audio input as well as from the feedback and the headphone output refer. Without further ado I created this grounding by scraping open the grounding lines from the potentiometer and connecting them directly to the OpAmps with wire.
Lo and behold, your colleague is no longer grumbling! Bingo!!
Layout, the third ...
In October 2012 I implemented the previous knowledge in a new layout so that you can easily and successfully recreate the amplifier.
In October 2012 I implemented the previous knowledge in a new layout so that you can easily and successfully recreate the amplifier.
There the grounding has been changed again, it is a two-sided layout WITHOUT a ground plane, so that you can theoretically build the amp on a one-sided circuit board if you then lay the missing connections with wire.
In addition, I brought in some of Helmut's ideas and changed the power supply again so that the operating voltages are cleaner (without ripple voltages) (with the exception of the 350V, where a small ripple voltage has no influence on the hum at the output).
Furthermore, a new volume potentiometer from ALPS has been added, which has a better synchronization and hopefully lasts longer - the cheap potentiometer from the old amplifier was already starting to scratch ...
I ordered this board from PCB-Joker , where you can get it for 60 €. The gag with this company is that you don't know what you are getting - it can be a printed circuit board between 0.5mm and 2.0mm thick, with any colored solder mask. While the color is not an issue, I was unlucky with the thickness - I got a 0.5 of all things. For this reason I had to attach an additional fastening in the middle of the board, with a normal 1.5mm board this is not necessary.
The complete documents on the RKV can be downloaded here.
I ordered this board from PCB-Joker , where you can get it for 60 €. The gag with this company is that you don't know what you are getting - it can be a printed circuit board between 0.5mm and 2.0mm thick, with any colored solder mask. While the color is not an issue, I was unlucky with the thickness - I got a 0.5 of all things. For this reason I had to attach an additional fastening in the middle of the board, with a normal 1.5mm board this is not necessary.
The complete documents on the RKV can be downloaded here.
The archive contains:
KiCAD project
Gerber
BOM
Front panel files for the housing
(can be ordered directly from Schaeffer ).
setup and start-up
After setting up the amplifier and checking the equipment (the tubes are not yet fitted!)
You should first connect only the 36V winding of the transformer and switch on the amplifier.
Then you should check the following points:
+ 22V via D20 (22V-Zener-diode)
+ 12V at C44 (output of the 12V regulator)
-8.2V via D19 (8.2V Z-Diode)
-18V via D21 (18V-Z-Diode)
If all voltages are OK, you set a voltage to approx. 3.5V with the potentiometer RV2 via C4, the same with RV3 3.5V via C17.
Now you can switch off the amp again and connect the high voltage from the transformer.
+ 22V via D20 (22V-Zener-diode)
+ 12V at C44 (output of the 12V regulator)
-8.2V via D19 (8.2V Z-Diode)
-18V via D21 (18V-Z-Diode)
If all voltages are OK, you set a voltage to approx. 3.5V with the potentiometer RV2 via C4, the same with RV3 3.5V via C17.
Now you can switch off the amp again and connect the high voltage from the transformer.
ATTENTION, from now on it will be dangerous !! After switching on you should measure a voltage of approx. 375V via C36 (this voltage is even higher than later in operation, since no tubes are plugged in yet and therefore no anode current is flowing).
If this voltage is also fine, you can switch off the amp.
IMPORTANT: wait until the C36 is discharged to a safe voltage and then insert the tubes.
If you turn on the amp now, the tubes should heat up. During the heat-up time, a strong fluctuation in the output voltage can be seen at the headphone output, which should calm down after the end of the heat-up time.
If you turn on the amp now, the tubes should heat up. During the heat-up time, a strong fluctuation in the output voltage can be seen at the headphone output, which should calm down after the end of the heat-up time.
To properly balance the amp, a function generator (1kHz, sine) is connected to the input, a load resistor (300 to 400 ohms, 5 watts) plus an oscilloscope connected to the output.
Now the amplitude of the generator is slowly increased (don't forget the volume potentiometer) until the signal at the output begins to distort and the peaks of the sinusoidal signal are cut off.
The amplifier is then set with the potentiometer of the respective channel so that the distortion is symmetrical, ie positive and negative half-waves of the sine are cut off evenly. The other channel is set in the same way.
If you don't have an oscillator / function generator, you can simply set the potentiometer so that about 150V is applied to the output electrolytic capacitor (C13 / C26). Then you should be roughly in the middle of the dynamic range.
If you don't have an oscillator / function generator, you can simply set the potentiometer so that about 150V is applied to the output electrolytic capacitor (C13 / C26). Then you should be roughly in the middle of the dynamic range.
A few more tips ...
Here are some more information and tips on how to recreate it. The ZIP archive contains a parts list that should contain pretty much everything you need for a replica. Sources of supply and current prices are also given there. Do not be put off by the price, it really includes ALL parts including custom-made transformer, circuit board and housing, and some things are only available in larger quantities (screws, etc.). So you can definitely still save here.
When making a replica, you should make sure that the entire audio signal chain, if at all, should only be grounded at one point (connected to the protective conductor). The housing is designed so that this ground point is at the headphone jack; the cinch sockets, on the other hand, are isolated from the housing.
Here are some more information and tips on how to recreate it. The ZIP archive contains a parts list that should contain pretty much everything you need for a replica. Sources of supply and current prices are also given there. Do not be put off by the price, it really includes ALL parts including custom-made transformer, circuit board and housing, and some things are only available in larger quantities (screws, etc.). So you can definitely still save here.
When making a replica, you should make sure that the entire audio signal chain, if at all, should only be grounded at one point (connected to the protective conductor). The housing is designed so that this ground point is at the headphone jack; the cinch sockets, on the other hand, are isolated from the housing.
If the rest of the audio system is grounded somewhere, you can quickly catch ground loops; then you should look where the ground loop is and break it open.
The metal axis of the potentiometer should also be grounded if possible, otherwise it could crack when you touch the (metal) potentiometer in the headphones.
Don't be surprised if you put on the headphones and turn on the amplifier; at the beginning during the first 10-20 seconds you can hear an illustrious humming concert until the tubes have reached their operating temperature.
The metal axis of the potentiometer should also be grounded if possible, otherwise it could crack when you touch the (metal) potentiometer in the headphones.
Don't be surprised if you put on the headphones and turn on the amplifier; at the beginning during the first 10-20 seconds you can hear an illustrious humming concert until the tubes have reached their operating temperature.
Afterwards, the amplifier should be quiet - at least as far as the hum is concerned ...
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And now of course the all-important question:
How does it sound now?
I would like to say! Together with my Sennheiser HD570, a really strong duo. Nice sound, well-developed bass, that's how it has to be. And it really is the case that with familiar songs you keep hearing small details that you haven't noticed before. So the construction was definitely worth it for me.
Pictures of the construction
Here are a few more photos of the structure and inner workings of the RKV:
Front view ...
... and from behind.
Interior view of the RKV.
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And now of course the all-important question:
How does it sound now?
I would like to say! Together with my Sennheiser HD570, a really strong duo. Nice sound, well-developed bass, that's how it has to be. And it really is the case that with familiar songs you keep hearing small details that you haven't noticed before. So the construction was definitely worth it for me.
Pictures of the construction
Here are a few more photos of the structure and inner workings of the RKV:
Front view ...
... and from behind.
Interior view of the RKV.
The circuit board in detail.
In the middle the additional fastening necessary for the 0.5mm board.
Pictures of replicas
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March 2017:
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March 2017:
Uli recreated the amplifier with the original layout of Jogi's tube booth, and came to my site because of the hum problem. Obviously the original is not completely hum-free either, but together we were able to calm the amplifier down a bit. Also a very nice replica!
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January 2014:
Stefan cloned the headphone amplifier with his own layout and also added a circuit for volume control via a motor potentiometer, which can be remotely controlled using an infrared remote control. The case is self-built. A really nice piece!
The complete documentation on this replica can you download here.
Many thanks to Stefan for providing!
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March 2013:
Thomas used the current, the third version of KiCAD layout.
He made the circuit board himself by simply producing the front and back sides separately on two single-sided circuit boards and then putting them back to back.
The housing is made of laminated wood with bamboo fittings, the front and back panels are made of 3mm MDF panels painted gray. Became very beautiful!
Note:
The pictures show a Euro plug without a protective conductor. Due to the metal surfaces that can be touched and the high voltages carried in the device,
I strongly advise you to use the amplifier WITH a protective contact:
SAFETY FIRST!
In addition, the cable should be led through a rubber grommet etc. at the housing entrance and provided with a strain relief, otherwise the cable could chafe through and the conductors could come into contact with the housing.
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END OF Mario.de
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END OF Mario.de
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