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]

If built using an M49C circuit, the 5718 has very little low end, which I guess is why so few people try the 5718.



After a lot of experiments, until today, I found that 5718 is optimal only when the board voltage is 53V. The low frequency is back again, which is great.