Stereomour 45 Voltage Question

[Paul Birkeland]

a couple questions, did I hurt anything having it wired wrong?

Not particularly, the extra voltage drop from wiring the choke properly will let the 45's last longer.

is this only going to help the bass or is it an overall improvement?

It will be most noticeable in the bass.

is the reason for this amp sounding so good, the  lack of noise and hum or is it the 45 tube , and your going to say both. and this tube was discontinued way back when , WHY? 1.75watts?

45's are still made.  The construction of the 45 tends to create a slightly quieter tube than the average 2A3. 

[Paul Joppa]

You did not damage anything.

[kevner21]

Yes I know they are still made . OMG gentlemen, I just listened to one of my favorites Ahmad Jamals Saturday morning. this is a totally stock kit . running 2 RCA Cunninghams. I don't want to let the secret out so i'll just say thank you, thank you , thank you...................

[kevner21]

so now can anyone hear the difference, now that the changeover has been done correctly??

[rusty-jade]

As noted previously, the bass has increased substantially on my 98 db/m sensitivity speakers, in fact so much so that I do not need my subwoofer anymore. I played  a classical piece with organ ( Strauss 's Nun Chorus) and the vibration was noticeable.  It is difficult to say whether other higher frequencies were also increased but to be sure there are no noticeable adverse sonics.   

[kevner21]

yes kind of floored me especially just being 2 watts. thought it couldn't be done with so little power. want to try the pair of globes I have . this is with AN10's in a 2.8 box, and again in a small room ...........

[chard]

This discussion has got me asking why not do this mod to my stereomour which has a 2a3 tube. I could use improved bass. I measured the resistance of the choke at the different settings.
   Old 45 setting: red to black=263 ohms
   New 45 setting: Blue to red=824 Ohms
   2a3 setting: blue to black=556 ohms
The new 45 setting has the most henries 40, and thus the best bass. Why not use this setting for the 2A3 stereomour? It would only lower the 2a3 plate voltage by 12-15vdc.
  Standard 2a3 choke setting, .05ma at plate x 556 ohms=27.8vdc
  2a3 set to new 45 choke setting, .05ma at plate x 824 ohms=41.2vdc
Is there a reason why this mod would be a bad idea on a standard 2a3 stereomour?

[Paul Joppa]

...
Is there a reason why this mod would be a bad idea on a standard 2a3 stereomour?

Yes, there is indeed.

The flux in the core is proportional to the product of turns times current. (Inductance goes as turns squared.) The iron core saturates if there is too much flux, causing distortion and loss of inductance. Your measured resistances are proportional to the number of turns. Using black to blue, you get 20 henries at 50mA maximum before saturation. Using red to blue you have 40% more turns, so you can use a maximum of 35mA but get 40 henries.

That said, saturation is a gradual thing. You won't hurt anything by trying it.

[chard]

Thanks Paul,
   I think I will leave well enough alone.

[kevner21]

that leads to my next question  of can you still use a 2a3 in the 45 amp? and now that we are on the 45 amp what NEW 45 tube  would you buy, being that there is only 2 companies that make them!!!!!!!?

[Paul Joppa]

You can use the 2A3 in a Stereomour converted to 45. You'll get a bit more power, at the price of slightly more distortion at full power.

[rusty-jade]

@Kevner21
The new 45 tubes at TJ Music is expensive and even more so are the ones from Emission Lab.  I bought all of my 45s used from e-Bay and have been lucky thus far.  Alternatively, you can get the standard Shuguang 2A3 tube from the Tubes Store which is not that expensive.  I have used these before for a 2A3 amp (which I butchered eventually) and I found them to be very good, comparable to the JJ 2a3-40, just a bit less in bass, but  hardly noticeable and they are much cheaper.

[rusty-jade]

The Sophia Mesh Plate is made by TJ Full Music.  DIY Supply used to sell the ceramic base pair, costing $375 at Sophia, for $299, but they are currently out of stock (http://www.diyhifisupply.com/opcart/index.php?route=product/category&path=179_78_241) I have not tried them, but have been fortunate to buy reasonably strong, used older pair versions  like Tung Sol, Ratheon and GE, all bought from e-Bay and all sounded very good.

[kevner21]

 I want to inject further thought to this topic . I replaced the non descript .1uf 600v cap with the Jupiter round bees wax  ones and I know it's been a while , but I'm getting some fantastic bass with no degradation of the already great mids and high frequencies . please let me know when you can convert the stereomour 2 to 45's ,I'm in...........

[mkane]

  I have a 2011 Stereomour and want to switch to 45. Should I just follow the instructions in the manual? thx