Apex 460 mod with some Telefunken ELA M 251 influences

[gary o]

Thanks Papsarski, must read to learn more...

 

[saxmonster]

Ok so I did some testing on the apex 460 power supply today after work.

So zener 5 = 69.5vdc
    zener 6 = 71.6vdc

which = 141.1vdc so why is it that when i measure pin 1 i get 142.9 and not 141.1vdc.

For pin 1 its 142.9 VDC so I definetly need to get new zeners as this is 22vdc over what it should be, by why doesn't it equal 141.1vdc with the two zeners added together?

Pin 2 = 6.63 which is great for the heater right?

pin 3 starting from omni to figure 8 goes like this

0.010vdc ---- Keeps dropping for some reason
15.45vdc
30.6vdc
45.6vdc
60.6vdc
75.9vdc
91.2vdc
106.5vdc
123.5vdc  ----- Keeps rising for some reason.


Do theses look good?  Now if I put lower zeners in will they affect the numbers for polarity patterns?

Pin 5 = .053
Pin 6 = .04

I think these pins are for the transformer?

I did all this with just the PS turned on and the cable attached.  No mic attached on it.

Tim's Capsule is on its way so I need to start modding this mic and getting it ready.

Can't wait.

-Scott

So i put in a new 39 vdc zener which actually reads 38 and now between pins 1 & 4 i am getting 110.8 VDC.  I am going keep that value as it is close to a elam 251.  Now my heater is still at 6.63 at pins 2 & 4.  But now all the polar pattern values have changed how do these look?



pin 3 starting from omni to figure 8 goes like this

0.010vdc
12.02vdc
23.85vdc
35.5vdc
47.2vdc
58.9vdc
71vdc
83.5vdc
96.5vdc

How do these values look?  I am still waiting for the bv11 transformer.  I was hoping to do a lot of work this weekend on it.  But i think i will wait for the transformer.  Tim's capsule is hear and looks great.  No mic was hooked up these are just reading from the power supply only.  No cable or mic connected.

-Scott

 

[david-p]

pin 3 starting from omni to figure 8 goes like this

0.010vdc
12.02vdc
23.85vdc
35.5vdc
47.2vdc
58.9vdc
71vdc
83.5vdc
96.5vdc

How do these values look?

-Scott

I have given up trying to measure the voltages in chains of resistors, since one has to take into account the resistance of the meter.  As long as all the resistors are the right value (it would be very unusual for a 1% resistor to be out of spec these days) and the voltage at the top is correct, I would not worry unless the cardioid is way off what it should be when you listen to it.

David

 

[saxmonster]

Ok so I am working on swapping C8 on the 460.  These are the directions Dave gave.

"Remove C8 which is a 1ufd/450 volt.  Hot glue the 2.2 ufd/600v to the circuit board.
One side connects to pin 8 of the tube or where R8 connects to the circuit board and goes to pin 8 of the tube.  R8 is a Red Violet Orange resistor.  The red wire from the transformer goes to the other side of the 2.2ufd capacitor.  The white wire from the transformer goes to ground or pin 4 or 7 of the 7 pin connector."

When I look at pin 8 there is nothing connected to it except a red wire that runs right over to pin 1. Do i have the pins number right.  I see that pin 2 does go to one side of C4 so thats how I found pin 1.  I just think they changed the wiring on this over the years.  Also why are pins 4 & 9 connected together with a small piece of wire and solder, kind of hard to see in picture but its the yellow wire  that goes to pin 4 and then to pin 9. 

Do i have the pins number wrong?  I am a noobie at this tube stuff so be gentle.

thanks
Scott

 

[saxmonster]

Never mind, I had the pins wrong. They go counter clockwise with no skips unlike a picture I was using.


errrrrrr. I hate being a noobie.

 

[saxmonster]

Hi Guys,
If i use two WIMA 1.0u capacitors and hook them up in parallel not serial fashion will this give me 2.0u. The 2.2u caps i ordered are just too big.  But I can make these 1.0u fit.


Thanks
-Scott

 

[pasarski]

Hi Guys,
If i use two WIMA 1.0u capacitors and hook them up in parallel not serial fashion will this give me 2.0u. The 2.2u caps i ordered are just too big.  But I can make these 1.0u fit.


Thanks
-Scott

Yep, but I'd try single 1uF first. Just tried output caps ranging from 1 to 3.3 uF in a mic of mine and the difference was small to my ears. 1uF sounded the fattest BTW. It's been discussed here before, smaller values seem to sound "better" some times.

 

[saxmonster]

Ok so I am done my first round of modding with this thing.

Here is what I installed or changed.

I installed Tim's Capsule
I installed Dave's BV11 Transformer.
I installed a GE 5 Star 6072 tube.

I replaced C4 with 1000pf styrene cap
I removed C6,C7, C9, C10
I replaced C8 with two WIMA 1uf caps in parallel for a total of 2uf.  10% tolerance though.

I changed the zener D5 to a 38vdc one.

I now get a reading of 110.8 at pins 1 and 4.  Should I change the zener to a higher one to get 120vdc?  Will this change the sound?  I just don't want to damage the expensive capsule.  I want the cardioid polar patter to read at 60volts correct?  What is the best way to test the vdc.  I mean there is no load on the power supply when I check with just the cable attached and no mic.  Can I check at the capsule with the mic is plugged in?  What would u guys do to correct the voltage for the B+ and polar pattens

With the original zener in I was getting the correct polar pattern voltage at cardioid 60.6 vdc but the B+ was at 143.  Again this was with no load.

The mic does sound great, very vintagey if that is a word.  But I was expecting a little more air and openness or sparkle/clarity. I mean it sounds a hell of a lot better than the original stock 460.  Any ideas on what to do to get the magical air in it?

I have two samples one is the 460 mod and the other is a u87 clone.  These were done on different days but it was the same preamp and room.  Only slight compression on the way in.  What do you thing of the 460mod's sound?

460mod
http://www.ehornstudios.com/media/460mod.aif

u87 clone
http://www.ehornstudios.com/media/u87.aif

I kinda wish the 460mod had some of the brightness like the u87 and kept the fat warm sound too.

Thanks
Scott

 

 

[tskguy]

Very interesting,
I am actually suprised how similar the recordings sound to me. Both sound very nice but I am with you, its intersting that Tims capsule doesnt sound brighter. Everyone says the capsule is 80% of the sound. Have you tried different tubes? It may be worth trying. I sure dont hate the sound thats for sure. I bet it sounds fantastic on male vocals. Good job!

 

[pasarski]

If you're B+ is 143V you're polarization voltage going to the backplate is 71.5V, too high for Tim's capsule (EDIT: you really have to sort it out with a dummy capsule before you put CT12 back in!). Maybe just change the other zener to smaller one also. But I think there's a error in your measurements or in your voltage divider tree. The fig. 8 voltage (the highest pattern voltage) should be the same than B+

And I think the clip sounds suspiciously dark. I know CT12's vary a little but mine was quite bright even though it was little darker than average.

(EDIT: It sounds very good though, and it's maybe just that U87 clone is brighter than I expected. Maybe you should check the new circuit with an other capsule that you're familiar with? If after that you think the capsule is too dark Tim'll adjust it for your taste, but not necessarily if it's been polarized too high!)

 

[saxmonster]

Thanks tskguy,
I have not tried other tubes as I really don't have any others.  This mic is also very hot with gain.  I am running it through my eeezzz 1073 and I am only on the second step up.  I though that was a little weird.  I might try a different c8.

 

[saxmonster]

Pasarski,
My figure 8 pattern can't exceed 120vdc because the back plate should only go up to 60vdc for the cardioid pattern.  Right now my B+ is 110 so that's why my patterns are lower than the 60vdc.  I will raise the B+ to 120vdc and check the pattern volts again.  Will maybe brighten it up.  Do I need to check these vdc with the mic(load) connected.  What's the best way to do this, I only check the pins holes in the mic cable with the mic not connected.  Thanks guys

 

[pasarski]

Pasarski,
My figure 8 pattern can't exceed 120vdc because the back plate should only go up to 60vdc for the cardioid pattern.  Right now my B+ is 110 so that's why my patterns are lower than the 60vdc.  I will raise the B+ to 120vdc and check the pattern volts again.  Will maybe brighten it up.  Do I need to check these vdc with the mic(load) connected.  What's the best way to do this, I only check the pins holes in the mic cable with the mic not connected.  Thanks guys

Ok, sorry I misunderstood. 110V is fine. You have to check mic connected. Use a dummy capsule, two 50pF-100pF caps are probably fine (I don't know if the values matter at all when checkin dc voltages?). Measure inside the mic if possible, or in the PSU (be careful!). Made some edits to the previous post.

 

[e.oelberg]

you may ask tim to adjust the capsule to your taste, if you are able to describe him what you want
he tunes it for you, he did that for me andI love it now.

nicholas

 

[Tim Campbell]

Of course I'm always willing to adjust a capsule to suit a customer's taste. My capsule is not particularily dark and so you might consider that it's something to do with the amplifier.

Some people feel that FLEA's F12 is a little dark or that Blackspade's UM25c is a tad bright but the top end on those capsules is the same.

 

[Tim Campbell]

Over on another forum Oliver Archut gave this advice:

    A 5K cathode resistor in parallel with a 5K trim pot will give you a wide sound range with reference to bias, for most tubes the capsule won't be able to push the tube in to clipping so the goal of having a symmetric clipping buffer is not needed at all. But the bias point will change high end as well as low end response so playing with the bias can help to find the tubes sweet spot.

    -Oliver

 

[tskguy]

After to listening to it again, (Better speakers) I for sure hear a bit more in the high end with Tim’s capsule. It is very subtle that’s for sure. If it were me I would focus on the amp as well. You can tell Tim’s capsule is pretty balanced in terms of frequency response. 

Eric

 

[saxmonster]

Tim thanks for responding here.  I will look that info up try adjust the bias of the tube.  I really don't think its your capsule at all as it sounds very warm and rich, even and clean.  I think it has something to do with the amp section as stated.  I will have to listen to it again tskguy as it was late last nite but I though the u87 had more highs.  Will double check though.  I will check out the bias part that Tim mention but what else in the amp sections might I look at? 

I also took a few measurements today.

on the tube pins i get the following vdc.

tube pins 1 & 9 I get 64vdc.  Should that not be 110.  As that is what the power supply is putting out?  Or are the resistor r1 and r2 lowering it?

Tube pins 4,5 & 9 I get 6.06 for my heater.  That was 6.63vdc when i measured directly from the PS and the 9 pin cable.

tube pin 9 and rear capsule connection on pcb.
omni = 0vdc
Card = 8.6vdc
fig 8 = 17.5vdc

tube pin 9 and front capsule connection on pcb.
omni = 0vdc
Card = 0vdc
fig 8 = 0vdc

Am I doing something wrong with the front capsule?

I am still learning so be easy on me.

Should I get the power supply to put out 120vdc instead on the 110?

Thanks
Scott

 

[kilmister]

I bet 110V is good enough.

When measuring polarization voltages you should measure them right after voltage divine network. If you measure pol voltages straight from rear capsule your meters resistance is too low (1 to 10Megs typically) and most of current will flow thru meter and drops reading.

 

[saxmonster]

Ok so tonight when I was holding the mic I notice this awful resonance.  I talk about it in this mp3.  This is a CT12 capsule.  Maybe Tim can chime in and let me know what might be wrong.  Thanks for the support guys.

http://www.ehornstudios.com/media/Apex460%20Mod.mp3


I am running at B+ = 110vdc.  Maybe thats not enough volts?

Why can't things just work right?

thanks
-Scott