Neumann M49 Clone : Build Thread Puck Style (TLM49 Conversion To M49 b-c)

[Moby]

Understood and thank you, Srdjan. I'm using 6S6B-V's and they are all about the same noise level out of the 5 or 6 I've tested. Maybe it's worth trying some 5718ws's?

I have the PSU from Dany's kit so I believe it's unregulated. The cap doesn't appear leaky but it's probably better to not risk it in this case...

From my experience 6s6b's are good low noise tubes. But yes, you can also try other like 5718. I'm not familiar (in details) with Dany psu arrangement but measure the voltage unloaded and if exeeds 150v stay away from the 160v capacitor.

 

[egroys]

Just to be clear, you mean the B+ voltage, correct? And is there anything else I can check/do in terms of noise, or at this point is it just the circuit?

 

[Moby]

Just to be clear, you mean the B+ voltage, correct? And is there anything else I can check/do in terms of noise, or at this point is it just the circuit?

Yes, anode voltage. At the psu, withouth the load of the tube.
I'm afraid that you can't do much but good PSU filtration (hum) and low noise tube selection.

 

[rmburrow]

Yes, anode voltage. At the psu, withouth the load of the tube.
I'm afraid that you can't do much but good PSU filtration (hum) and low noise tube selection.

I like the Neumann NKM type supply where a gas voltage regulator tube is connected across the HT in series with an 8 k resistor off the HT rectifier. The regulator is a 150B2 (a 0A2 American will work with wiring change) which limits the DC voltage to the filter caps to 150 volts regardless of the HT load. 0A2's are inexpensive compared to the 5840, 6072, etc. I use rechargeable 1.5 v AA batteries in place of the "stabilytes" in the NKM. To power a 5840, the 4 volt DC heater supply must be increased to 6 volts with a wiring change, and 4 "AA rechargeables" in series regulate the heater supply for a 5840.

 

[egroys]

Yes, anode voltage. At the psu, withouth the load of the tube.
I'm afraid that you can't do much but good PSU filtration (hum) and low noise tube selection.

I have 138V unloaded at the PSU. Do you think that's too risky for that Soviet NOS rated at 160V?

 

[Moby]

I have 138V unloaded at the PSU. Do you think that's too risky for that Soviet NOS rated at 160V?

I's really tight.since i'ts PIO NoS I really can't be sure. Generally speaking those guys can handle more than 160v but who knows?

 

[ZHOUJUN]

terribly sorry
I take back my previous statement about the insufficient low frequency of the 5718 used in the M49C circuit. I now feel that the 5718 is richer and fuller in the mid-low frequency than the 6S6b and 5840. The 6S6b feels that the mid-frequency is too prominent, and the 5840 low frequency is a bit lacking. I used MOBY's BV11 and Moby's T14 for testing, no big differences were found.

 

[egroys]

I just received a ready made M49 PSU from China. I purchased a body and yoke directly from Jenny and they were offering PSU's for $55 so I couldn't resist. I am curious, since these appear considerably different than my poctop ones, if I should change/upgrade any components? There are no trimmers here but there is also a voltage regulator. I will likely update the 7 pin wiring to match Dany's standards for interchangeability.
Please let me know your thoughts and recommendations!

 

[Migs 31]

if I should change/upgrade any components? There are no trimmers here but there is also a voltage regulator. I will likely update the 7 pin ...

Hi,
I think I got exactly the same (well... Thomas ordered them for me )from Jenny, with a M49 & their great Yoke.

Could you share what’s written on the front of the metal box ? Is it PS-2 ?

You say « there is a regulator » From the top of my head that would be for the 6.3V heater. The HT will be at the bottom left of your PSU (on first pic) coming out of those two 1N47** diodes, like most Chinese Power supplies. And it will need filtering and/or correct grounding scheme.

Check it really is 120V at HT output.


M

 

[egroys]

Hi,
I think I got exactly the same (well... Thomas ordered them for me )from Jenny, with a M49 & their great Yoke.

Could you share what’s written on the front of the metal box ? Is it PS-2 ?

You say « there is a regulator » From the top of my head that would be for the 6.3V heater. The HT will be at the bottom left of your PSU (on first pic) coming out of those two 1N47** diodes, like most Chinese Power supplies. And it will need filtering and/or correct grounding scheme.

Check it really is 120V at HT output.


M

It doesn’t say it on it but it’s their ‘PSU-3’

What sort of filtering would I need to add?