Hum over 113db horn? S.E.X a better bet?

[BD]

I think that pretty much sums my worry. And I sit only 3m away from the speakers.

I've tried Miniwatt S1 and it was quiet enough. Their newer N3 was not however. I'd like to try for something a bit better than the Miniwatts and used to have an enhanced S.E.X which I really liked and which was very quiet over 100db speakers and which I belive is quieter than teh AC heated Steromout. 2A3/45's would be preferable if they wont be too noisy. Could anyone give a good idea of how much noise I could expect, or compare it to some other well known amp in terms of noise/

Thanks for the help

B

 

[JC]

Perhaps the numbers will guide you; I believe they rate the SEX at approximately 83 dB signal-to-noise.  How does that compare with the S1?

Edit: I seem to have a conflict between my browser and the Miniwatt site, or I would have tried to look up this information myself.  Another indication may be the Hum rating for each amp.  I seem to recall something about the SEX being around .3 mV, but I have never found the occasion to actually measure this.

 

[Thoburn]

FWIW, My Lowther DX4 in a back loaded horn cabinet is rated 99 dB and I can hear no hum at all if I am more than 3 feet from the speaker (nothing playing). I have a Stereomour running the Stock Sovtek 2A3 power with a Mullard NOS 12AT7 input stage. I am running Jupiter HT caps in the signal path. As Always, YMMV.

 

[Paul Joppa]

Here are the typical hum levels of Bottlehead amps, as we have measured them:

Paramour/Stereomour:  2mV

Paramount 300B: 0.6mV

S.E.X. Amp  0.27mV

The Paramount should be 0 to 6dB quieter set up for 2.5v filament tubes (2A3 or "2A3-40" types), but we haven't made the measurement. 2mV is typical for AC-heated 2A3 amps. Hope that helps a bit.

The Miniwatt N3 is spec'd at 1mV noise, the S1 at 0.8mV - an insignificant difference. I suspect the difference you observed was not typical of these amps; hard to say if the S1 exceeded spec or the N3 was extra quiet. Was this comparison done in the identical system and at the same time?

 

[BD]

Thanks very much for the replies.

Something does seem amiss with the Miniwatt figures, or my amps. I need to sound out first if what I'm hearing is 1mv. (I did use both those amps on same speakers at the same time).

Cheers
B

 

[Grainger49]

I will assume that you dialed in the hum pots on the Stereomour with a meter.  I don't know what the manual says.  

An alternative that is cheaper than scrapping a nice new Stereomour is to convert it to DC heaters.  Much of the hum in the Stereomour is from the 2A3 heater circuit.  The Paramount uses choke filtered DC heaters  The Stereomour heater winding might not support this so you might need another transformer just for the heater.

I say this because I love the sound of my Paramours.  I'm just encouraging you to seek a cheaper path.

Let me get this straight, you are 9 feet back from the horns?  You used both amps (miniwatt and Stereomour) on the speakers at the same time?  (this one I think I have wrong)