stelin

Re: investigating the russian 6S6B-V tube
« Reply #40 on: August 05, 2017, 04:57:48 PM »
Thank you, RuudNL. Thats good to know.

/Stefan


stelin

Re: investigating the russian 6S6B-V tube
« Reply #41 on: August 05, 2017, 05:18:29 PM »
I understand that the 6S6B-V tubes wants 6,3 Volts for the heater (just like the 5840) and that the heater draws more current (I don't think that's a problem with my PSU).

Is there anything else I have to change in the "standard" M49c circuit?

ln76d

Re: investigating the russian 6S6B-V tube
« Reply #42 on: August 05, 2017, 07:48:40 PM »
Is there anything else I have to change in the "standard" M49c circuit?

Yes - biasing!

Put potentiometer instead cathode resistor, adjust proper value of voltage, desolder it, measure resistance and install proper resistor.

wlinart

Re: investigating the russian 6S6B-V tube
« Reply #43 on: August 08, 2017, 05:44:24 AM »
I am planning to build a M49 microphone. My thought was to use a apex 460-style PSU for this mic like described in this thread: https://groupdiy.com/index.php?topic=44667.0 So mod the psu with zener diodes to lower the B+ voltage.
The schematic of the psu is found at this link: https://www.gearslutz.com/board/attachments/geekslutz-forum/111879d1235602544-apex-460-mod-u47-apex-460-mods.pdf
Could anyone tell me if this psu would be compatible with the 6S6B-V tube? Will it deliver enough heater current?

Thanks in advance!

ln76d

Re: investigating the russian 6S6B-V tube
« Reply #44 on: August 08, 2017, 06:37:30 AM »
For 6.3V 6S6B-V take lower current than 12AX7 - so - yes :)
You will have to reduce voltage by dropping resistors also, to get lower noise. If memory serves me well, after rectifier is 300V so it's pretty huge voltage to drop.

wlinart

Re: investigating the russian 6S6B-V tube
« Reply #45 on: August 08, 2017, 06:53:58 AM »
Good to know, thanks!!!

Lowfreq

Re: investigating the russian 6S6B-V tube
« Reply #46 on: August 09, 2017, 11:02:54 PM »
Since we've clarified that the 5703 and the 6S6B are equivalent to each other, has anyone here compared them directly in any mic circuits?

I've got some 5703s here in a mic and they sound really good. The noise level is ok, but I'm always looking to better it.  I've covered all the usual bases of cleanliness on the circuitry and floating the high impedance parts, & I'm in the middle of experimenting with different resistor values in the higher Meg parts, but I'm wondering if the Russians did a better job at making a quiet tube.

I'll probably just end up ordering some and experiment to see for myself, but I was wondering if anyone had already done a direct comparison of these two tubes in a microphone.

Re: investigating the russian 6S6B-V tube
« Reply #47 on: August 10, 2017, 01:01:14 AM »
For 6.3V 6S6B-V take lower current than 12AX7 - so - yes :)
You will have to reduce voltage by dropping resistors also, to get lower noise. If memory serves me well, after rectifier is 300V so it's pretty huge voltage to drop.

Ever thought of using a dropping resistor and a OB2 or OC3 VR tube to get 105 volts of regulated HT?  20 k 5 watts from the 300 volt HT to the plate of a OB2 should give you ample regulated HT to run a 6S6B-V, 5703, 5840, etc.  The VR tube will "fire" immediately and clamp the voltage.  You can also get fancy and use a OA2 VR tube, a 15 k 5 w resistor from 300 v to the OA2 plate, and use a couple RC stages beyond it to get 120 volts HT for the mic tube.  This does not consider available space in the PSU box....

ln76d

Re: investigating the russian 6S6B-V tube
« Reply #48 on: August 10, 2017, 07:51:04 AM »
Yeap i was thinking about really different kind of dropping voltage, but in most builds am using typical chinese PSU as a donor, space is required anyway, also some have very busy PCBs inside.  Probably my own microphone built in the spirit of m49 will end up with tube voltaage regulator since am uisng for it rebuilt gefell UM57 PSU. Original one is dead and i don't wont to substitute with direct replacement since it is east germany type not easy to find and nothing specail. Anyway when am building microphone to someone else i need to make it simple way as possible, and definately very stable, tube recitfiers and regulators can be tricky.
For M49 we need 120V (for most, "C" is 116V but 4V isn't any difference) ;)

e.oelberg

Re: investigating the russian 6S6B-V tube
« Reply #49 on: August 10, 2017, 08:30:11 AM »
Hi Lowfreq !

No I didn't  compare 5703 and 6s6b but I might have a 5703 in my locker than I could try. I wouldn't be surprised the russian is better. The USSR continued development and production of tubes longer than the west.


micaddict

Re: investigating the russian 6S6B-V tube
« Reply #50 on: August 10, 2017, 08:35:10 AM »
 :)

Were you an Ossi or a Wessi?

e.oelberg

Re: investigating the russian 6S6B-V tube
« Reply #51 on: August 10, 2017, 04:11:12 PM »
neither: West-Berlin

useme2305

Re: investigating the russian 6S6B-V tube
« Reply #52 on: August 10, 2017, 05:12:38 PM »
dann warste wessi! punkt!  :P

e.oelberg

Re: investigating the russian 6S6B-V tube
« Reply #53 on: August 10, 2017, 07:14:19 PM »
aber nein !  die Begriffe Wessi wie auch Ossi sind eine Westberliner Schöpfung. Die einzigen die weder Ossis noch Wessis sind  die Westberliner.

ln76d

Re: investigating the russian 6S6B-V tube
« Reply #54 on: August 10, 2017, 08:06:34 PM »
Meinungen sind gespalten ;)

Re: investigating the russian 6S6B-V tube
« Reply #55 on: August 12, 2017, 12:23:08 PM »
Yeap i was thinking about really different kind of dropping voltage, but in most builds am using typical chinese PSU as a donor, space is required anyway, also some have very busy PCBs inside.  Probably my own microphone built in the spirit of m49 will end up with tube voltaage regulator since am uisng for it rebuilt gefell UM57 PSU. Original one is dead and i don't wont to substitute with direct replacement since it is east germany type not easy to find and nothing specail. Anyway when am building microphone to someone else i need to make it simple way as possible, and definately very stable, tube recitfiers and regulators can be tricky.
For M49 we need 120V (for most, "C" is 116V but 4V isn't any difference) ;)


Look up the schematic for the NKM supply.  Trace out the UM57 PSU...it may be close.  It's rather easy to adapt the NKM supply for the 6 volt tubes using 120 volt HT.  I personally prefer the VR tube (150B2, OA2, etc.).  I like the way the HT is clamped with the VR tube in those power supplies.  The VR tubes last a long time, also...

Delta Sigma

Re: investigating the russian 6S6B-V tube
« Reply #56 on: August 12, 2017, 02:47:40 PM »
I have an M49 that I will be rebuilding. I have AMI's BV11r which is wound to compensate for the 5840's lack of low end. I'm considering rebuilding with the 6S6B. Does anyone have any thoughts on using it with the BV11r? I'll most likely give them both a try and see which I like better but I'm still curious if anyone has thoughts about the BV11r and 6S6B.

I built the B version of the M49 only to have noise issues. It looks like it's the choke that's causing noise.  I built the PSU in too small of a chassis and rather than fight with the choke I think I'll ditch it and build the C version.

ln76d

Re: investigating the russian 6S6B-V tube
« Reply #57 on: August 12, 2017, 07:31:58 PM »
I have an M49 that I will be rebuilding. I have AMI's BV11r which is wound to compensate for the 5840's lack of low end. I'm considering rebuilding with the 6S6B. Does anyone have any thoughts on using it with the BV11r? I'll most likely give them both a try and see which I like better but I'm still curious if anyone has thoughts about the BV11r and 6S6B.

I built the B version of the M49 only to have noise issues. It looks like it's the choke that's causing noise.  I built the PSU in too small of a chassis and rather than fight with the choke I think I'll ditch it and build the C version.

BV11r - for me it was weirdest idea from Oliver transformers - what for messing up with transformer bandwith, especially when:
- most M49 circuits have pretty big cut on lows made in the circuit
- you can controll low end in the circuit anyway

Don't see concatenation between circuit version change and noisy/hum PSU.
If there's problem with PSU, then it will be on both circuits.
If it's choke (don't know why and how? - but let say it's choke problem) then i would remove it and replace with just RC.
   
Change tube and adjust bias - then you will hear is it worth to use 6s6b or not ;) (fix noise first :P)

e.oelberg

Re: investigating the russian 6S6B-V tube
« Reply #58 on: September 01, 2017, 09:40:13 AM »
hola the mic is running - with a couple of bucks  chinese k67 clone it already sounds decent. Now I wait for the Maiku  k47. The tube is superquiet no frequency roll off, goes straigth down into rumble, I might have to do something down there.  no broadcast filters installed, 2 x  0.47 in parallel on the output. I didn't have 150M so I use 470M.

e.oelberg

Re: investigating the russian 6S6B-V tube
« Reply #59 on: September 02, 2017, 03:57:44 AM »
any tip for a damping material to install the tube, right now it's loose and a bit to microphonic