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Bottlehead Kits => Legacy Kit Products => Stereomour => Topic started by: ptlud on February 02, 2015, 12:40:54 PM

Title: Stereomour 45 Voltage Question
Post by: ptlud on February 02, 2015, 12:40:54 PM
I just finished building the Stereomour for 45 tubes.   I substituted 4.7 uF Mundorf Supremes for the 3.3 uF Solens.

T1  357V
T15 355V
T17 366V
T19 364V
A2 356V
C2 354V
IA 364V
IB 366V

The amps is running great, but I want to make sure there isn't something wrong with the wiring.

Thanks,

Paul
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Joppa on February 02, 2015, 05:30:56 PM
I think there may be a problem in the manual. More after I check with the rest of the team.
Title: Re: Stereomour 45 Voltage Question
Post by: ptlud on February 03, 2015, 02:15:22 AM
I re-checked the wiring and think the amp is correctly wired for the 45 tube.  The voltage values I measured are within ~ 5% of nominal.

Paul
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Joppa on February 03, 2015, 01:59:06 PM
OK, I've checked my analysis again and I'm sure about this.

There is an error in the manual (both 2010 and 2014 versions) on page 50, wiring the plate choke for the 45. Doc B will put up a sticky post soon, but meanwhile here is what you need to know:

The blue wire should go to the 45 socket pin 2, for both 45 and 2A3.

For the 45, the black (sometimes black/red) wires go to  terminal 17L and 19L - this is their parking spot since they are not connected to anything else.

For the 45, the red wires go to the HV+ terminals on the power supply board (see p.54, where the 2A3 configuration is shown - but for the 45, put the RED wire in the HV+ center hole). This will greatly improve the bass.

Sorry we missed this for so long - not many have done the 45 conversion, and I caught it by accident when I saw you had only 10 volts drop across the choke. It should be 30 volts drop, so your 45 plate voltage will drop by 20 volts, putting it much closer to the correct voltage. This same voltage error appears in the voltage checks; A2 and C2 should be listed as 320v, not 340v.
Title: Re: Stereomour 45 Voltage Question
Post by: ptlud on February 03, 2015, 03:13:06 PM
OK I made the changes (see attached photo).  Here are the new voltages.

T1 345V
T15 337V
T16 55V
T17 354V
T19 355V
T20 54V
A2 334V
C2 336V
IA 364V
IB 363V
These voltages are much closer, except IA and IB.

Please let me know if its OK to use the amp.

Paul
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Joppa on February 03, 2015, 03:23:35 PM
Looks really good - try some tunes!
Title: Re: Stereomour 45 Voltage Question
Post by: ptlud on February 03, 2015, 03:32:09 PM
Playing JJ Johnson Standards CD.  Sounds great.  Not sure I can tell the difference, but I am glad the 45's are being run at the right voltage.  They are rather expensive.

Paul, thanks for your help and very prompt response.

Paul
Title: Re: Stereomour 45 Voltage Question
Post by: jimiclow on February 08, 2015, 08:49:37 PM
OK, I've checked my analysis again and I'm sure about this.

There is an error in the manual (both 2010 and 2014 versions) on page 50, wiring the plate choke for the 45. Doc B will put up a sticky post soon, but meanwhile here is what you need to know:

The blue wire should go to the 45 socket pin 2, for both 45 and 2A3.

For the 45, the black (sometimes black/red) wires go to  terminal 17L and 19L - this is their parking spot since they are not connected to anything else.

For the 45, the red wires go to the HV+ terminals on the power supply board (see p.54, where the 2A3 configuration is shown - but for the 45, put the RED wire in the HV+ center hole). This will greatly improve the bass.

Sorry we missed this for so long - not many have done the 45 conversion, and I caught it by accident when I saw you had only 10 volts drop across the choke. It should be 30 volts drop, so your 45 plate voltage will drop by 20 volts, putting it much closer to the correct voltage. This same voltage error appears in the voltage checks; A2 and C2 should be listed as 320v, not 340v.

Paul, so is this the reason my Stereomour was dissipating 11.25 watts because of the extra 20 volts? Thanks for the info.
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Joppa on February 09, 2015, 11:18:45 AM
Paul, so is this the reason my Stereomour was dissipating 11.25 watts because of the extra 20 volts? Thanks for the info.
Yes, I believe that is most of the reason. I'm bummed that we missed that clue for so long. Try the switch - you will find a change in the deep bass, and I believe you will like it.
Title: Re: Stereomour 45 Voltage Question
Post by: jimiclow on February 09, 2015, 03:37:53 PM
Paul, you're right! I swapped the wires this morning, not only more bass but better sound. But then I'm now using the Smash. I've been listening to the old configuration for almost 2 years, didn't know it could be improved with just a wire swap.
Thanks Paul!
Title: Re: Stereomour 45 Voltage Question
Post by: rusty-jade on March 05, 2015, 05:42:16 AM
I was going to change the circuit from a 45 back to a 2A3 until I read PJ's comments.  I changed the wiring and was pleasantly surprised to hear how strong and tight the bass has become.  So, instead to reconverting the Stereomour back to 2A3,  I sold my Magellan VI sub instead!
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on March 08, 2015, 02:06:47 PM
i did the conversion about 6 monthes ago and was very happy with it . never checked the voltages for such a simple changeover. the tubes acted normal except for one 45 that went south. so this is the other wire that is twisted with the blue wire that goes to the HV+?
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Birkeland on March 08, 2015, 04:06:21 PM
so this is the other wire that is twisted with the blue wire that goes to the HV+?
The red wire that comes from the choke should go to B+ and the blue wire from the choke goes to plate.  The black choke wires can be heatshrunk and left alone, or can anchor at the empty two terminal strip lugs on the 5 pin strip behind the 9 pin socket.
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on March 08, 2015, 05:22:37 PM
Thanks CB got it now. has been playing awhile and just today changed it out for one of my other amps. to give it a rest . this amp with the 45's is quite possibly the finest ive heard. so it will be even better? cant imagine, will change it out tomorrow! thanks for the quick respond
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on March 11, 2015, 10:36:10 AM
a couple questions, did I hurt anything having it wired wrong? is this only going to help the bass or is it an overall improvement? didn't listen enough yet. 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?
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Birkeland on March 11, 2015, 04:24:45 PM
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. 
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Joppa on March 11, 2015, 05:47:16 PM
You did not damage anything.
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on March 12, 2015, 04:58:38 AM
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...................
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on March 21, 2015, 05:21:15 AM
so now can anyone hear the difference, now that the changeover has been done correctly???????????
Title: Re: Stereomour 45 Voltage Question
Post by: rusty-jade on March 21, 2015, 05:40:18 AM
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.   
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on March 21, 2015, 01:10:40 PM
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 ...........
Title: Re: Stereomour 45 Voltage Question
Post by: chard on March 23, 2015, 01:32:31 PM
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?
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Joppa on March 23, 2015, 07:09:22 PM
...
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.
Title: Re: Stereomour 45 Voltage Question
Post by: chard on March 24, 2015, 12:57:53 AM
Thanks Paul,
   I think I will leave well enough alone.
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on March 24, 2015, 04:44:30 AM
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!!!!!!!?
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Joppa on March 24, 2015, 01:41:14 PM
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.
Title: Re: Stereomour 45 Voltage Question
Post by: rusty-jade on March 25, 2015, 06:10:16 AM
@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.
Title: Re: Stereomour 45 Voltage Question
Post by: rusty-jade on March 25, 2015, 11:12:08 AM
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.
Title: Re: Stereomour 45 Voltage Question
Post by: kevner21 on September 05, 2016, 04:58:15 AM
 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...........
Title: Re: Stereomour 45 Voltage Question
Post by: mkane on September 05, 2016, 02:32:52 PM
  I have a 2011 Stereomour and want to switch to 45. Should I just follow the instructions in the manual? thx
Title: Re: Stereomour 45 Voltage Question
Post by: mkane on September 05, 2016, 03:01:30 PM
  And I believe after a bit of searching I can just follow my manuals instructions. Looking forward to this.
Title: Re: Stereomour 45 Voltage Question
Post by: Paul Birkeland on September 06, 2016, 03:29:33 AM
  I have a 2011 Stereomour and want to switch to 45. Should I just follow the instructions in the manual? thx
Yes, but just to ensure proper operation, the blue choke wires stay connected to the tube sockets, while the black choke wires are removed from the power supply PC board and the red choke wires take their places.

-PB
Title: Re: Stereomour 45 Voltage Question
Post by: mkane on September 06, 2016, 03:38:02 PM
  Tubes are on the way and I'll attempt this modification within the next few days. Thanks for the reply.
Title: Re: Stereomour 45 Voltage Question
Post by: mkane on September 07, 2016, 10:03:26 AM
  Seeing this amp was configured for 2a3 the black choke wires are a bit short and instead of adding a piece of black wire so they reach 17 & 19L can I just cap them with a piece of heat shrink? thx
Title: Re: Stereomour 45 Voltage Question
Post by: mkane on September 07, 2016, 10:54:39 AM
  It's done. running 2a3's. No problems.
Title: Re: Stereomour 45 Voltage Question
Post by: marantzfan on September 07, 2016, 06:04:55 PM
2a3's or 45's?  You had 2a3's in it, right?
Title: Re: Stereomour 45 Voltage Question
Post by: mkane on September 08, 2016, 03:15:28 PM
  45's will be here tomorrow. Bought some Cunningham branded tubes on the auction site.
Title: Re: Stereomour 45 Voltage Question
Post by: mkane on September 09, 2016, 08:38:37 AM
  Darn, this is silly good. Paired with my passive preamp there's headroom to spare using the modded Cornwalls. I should really be out getting some chores done.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi285.photobucket.com%2Falbums%2Fll58%2FMKane63t%2FDSC_0487%25203_zpsszea8wc4.jpg&hash=6e117d35d10380e9ecb23a35de331941) (http://s285.photobucket.com/user/MKane63t/media/DSC_0487%203_zpsszea8wc4.jpg.html)
Title: Re: Stereomour 45 Voltage Question
Post by: maryc27182 on September 09, 2016, 04:38:45 PM
45s are special, aren't they?

Enjoy!