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MXL 2001 Royer Mod Boards (BigUgly version)
- Thread starter Blue Jinn
- Start date
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bigugly
Well-known member
here's a link to the schems and BOMs for the PSU and mic PCB
http://www.mediafire.com/?1tjlbw7hf7ln7t0
http://www.mediafire.com/?1tjlbw7hf7ln7t0
dissonantstring
Well-known member
thanks james! I have always known you are a gentleman and generous member of this forum.
have a great holiday season!
best,
grant
have a great holiday season!
best,
grant
Blue Jinn
Well-known member
EEMO1 said:
I'm not familiar with the Nady 460. If you mean the Apex 460? I am pretty sure the PSU has about 150-155v for B+. (Based upon what I have read, I have not tested it)
That is close to the maximum for the 5840 tube. This circuit is designed for a B+ from 95-120v (Orig Royer mod is 95-100, BigUgly's G7/Royer hybrid is designed for 120. ) This also gives you about 60v on the capsule.
Blue Jinn said:
sorry, yeah I meant apex... I was thinking about using just the case, switches and the mains transformer for my build with your pcb's. I think calculating the resistors etc on your psu board... might work?
bigugly
Well-known member
EEMO1 said:
should work fine. just remember to calculate for wattage on your dropping resistor. more volts dropped the higher the watt rating of your resistor needs to be. I think I only put in enough space for a 5 watt resistor in the PI filter. If that isn't enough use two 5w resistors in parallel that are double the ohm value you need.
dmp
Well-known member
I don't think this is a concern. The mic and pattern switch together will at most draw about 1 mA. Just estimating with V=IR & P=VI
330R dV=0.33v P=0.0003 W
10k dV=10v P=0.01 W
50k dV=50v P=0.05 W
etc...
I don't see why you would need more than a .25W resistor, much less 5W. Now if you use this circuit for a power amp it would be a different story, so maybe that was the inspiration for the design?
dmp
Well-known member
Also, increasing R will improve the filtering
Blue Jinn
Well-known member
FWIW I built the PSU stock (with a 5watt 330 ohm resister) and unloaded I get 99v, loaded this drops to 71v. The transformers feeding it are probably very underrated, (but don't get hot or anything.) 117:9v 12v:115v wired backwards from the 9v. This one only seemed to give me 70v or so for some reason. It was what I had on hand at the moment.
I built another one with a 270 ohm who knows 5-10 watt resistor (happened to have one on hand) and with an 80v transformer (which puts out about 85v actually) I get 118v on the secondary with a (and I'll edit this later when I look at it) 100k - 300k load. (I can't remember at the moment)
I built another one with a 270 ohm who knows 5-10 watt resistor (happened to have one on hand) and with an 80v transformer (which puts out about 85v actually) I get 118v on the secondary with a (and I'll edit this later when I look at it) 100k - 300k load. (I can't remember at the moment)
Hey,
Still one question about the power transformers:
So, we need two, one that gives 120vac and one that gives 8-15vac.
What VA ratings are enough?
would this work for the 120vac? (6VA)
http://de.mouser.com/ProductDetail/Hammond-Manufacturing/186B120/?qs=sGAEpiMZZMvwUzoUXIIvyQPvPmwnNFGyOJ1stXxLUas%3d
And this for the heater? (10VA)
http://de.mouser.com/ProductDetail/Hammond-Manufacturing/160J10/?qs=sGAEpiMZZMvwUzoUXIIvyQPvPmwnNFGy0KFQQ%2fudC8M%3d
Still one question about the power transformers:
So, we need two, one that gives 120vac and one that gives 8-15vac.
What VA ratings are enough?
would this work for the 120vac? (6VA)
http://de.mouser.com/ProductDetail/Hammond-Manufacturing/186B120/?qs=sGAEpiMZZMvwUzoUXIIvyQPvPmwnNFGyOJ1stXxLUas%3d
And this for the heater? (10VA)
http://de.mouser.com/ProductDetail/Hammond-Manufacturing/160J10/?qs=sGAEpiMZZMvwUzoUXIIvyQPvPmwnNFGy0KFQQ%2fudC8M%3d
dmp
Well-known member
Looking at a datasheet for the 5840 tube, the heaters draw .15 A at 6.3v (AC or DC). This means the heaters want 1 Watt. Because it is rectified first, you want your transformer to be able to supply extra power for the rectifier to throw away. Just as a ballpark guess, if the pre-rectified voltage were 12.6v, then (at .15 A), the rectifier would dissipate (12.6-6.3)*.15 watts, which is also 1 Watt. So a transformer > 2 Watts (or VA) would be what you'd look for. VA means Volt-Amp, which = Power (Watts).
I think 120vac may give you a higher B+ than you may want. Depending on the loading, since it is unregulated, the B+ will be between 120v (the AC rms voltage) and 170v (the AC peak voltage). The 5840 has a max plate voltage of 165v.
I built the power supply using two Hammond transformers. For the B+ I got an 80v Hammond transformer (166g80) and for the heater 9v (166g9).
With the only loading being the pattern switch, the B+ is about 120-130v. I haven't hooked up the tube yet to see how much it drops. Hopefully it will get down to around 100v which is the Royer spec.
dmp
Well-known member
I just connected the mic and found the B+ was 128v with the 330 ohm dropping resistor.
Increasing the resistor to 10k gave a B+ of 106v. That should also give a cleaner power rail for the mic.
I haven't fitted the capsule yet so no sound yet, but hopefully soon.
Increasing the resistor to 10k gave a B+ of 106v. That should also give a cleaner power rail for the mic.
I haven't fitted the capsule yet so no sound yet, but hopefully soon.
dmp
Well-known member
I started a build thread in the lab for these boards:
http://www.groupdiy.com/index.php?topic=47258.0
Let's post build questions / discussions there and leave this thread for ordering.
http://www.groupdiy.com/index.php?topic=47258.0
Let's post build questions / discussions there and leave this thread for ordering.
Blue Jinn
Well-known member
telefunk said:
76.2mm x 76.2mm.
sr1200
Well-known member
boards came today thanks 
