Does size really matter, output transformer opinions needed

[Alonzo]

I have a Ki**FU**Marry dilemma, too many output transformers for the amps I have left to build.  I have BH-5's in nickel and M4 and a pair of OT-2's from a Stereomour build.  Building 2 more 2A3 amps so what to choose, what to choose?  The BH-5's are much bigger than the OT-2's and I've heard them before in a 2A3 amp.  My only experience with the OT-2's is in a 45 amp (just switched them out for nickel EXO-145's).  Which to use and which to sell?  I thought of keeping the Nickel and the versatile OT-2 but the M4 is no slouch in a 2A3-40 amp into Thrashers.  I could just build three amps but that's how I got in this problem in the first place, there's always another amp to build but I'm near my saturation point.
So I need opinions on the merits of the OT-2 with mesh plate 2A3's or with 2A3-40's.  Anyone have any comments on their Stereomour in the 2A3 configuration?  How about the difference in BH-5 nickel's to OT-2's?  The circuit is the same for all the amps with only changes to the output transformers, mesh plate or 2A3-40 and changes to the parafeed cap if needed.
Thanks in advance, I'll be bagging up parts for the builds.
Alonzo

 

[Paul Joppa]

Technically there is not much to choose between them. The bass power handling is the same; the smaller size of the OT-2  causes a slightly higher loss, from memory around 0.7dB vs 0.4dB for the MQs.

The MQs are of course more meticulously made; you may hear a subtle difference there. I imagine one of the MQs would be easier to sell than the OT-2.  The M4 can handle more deep bass power than the nickel so the M4 is IMHO best suited to a 300B amp. The nickel core has the virtue of delicacy (good bass and low distortion at very small signal levels) so I would pair it with the mesh plate tubes.

Note that the OT-2 has a 4K impedance, optimum for use in the Stereomour with the 2A3 running 300v at 50mA. The 3K impedance of the BH-5s is best matched by 275v at 55mA, again in my opinion. However, you can run the 2A3-40 at greater dissipation, say 300v at 60mA, giving close to 5 watts. You can comfortably use either the BH-5 in M4 or the OT-2 (it has M6) at that power level. The core material distortion difference is compensated by the greater number of turns in the OT-2, so I'd call that a toss-up.

There's my opinions for what they're worth.

 

[Alonzo]

Thanks Paul,
Your opinions are worth a lot.  One of the best part of them is the restraint you use.  All that your response was missing was "try it and see"  .
Seems I have to layout the build with the parts I have and see where my volts and amps come out, that should dictate the opt's and tubes to use.  I have a Chinese SET power transformer, a Hammond 302AX and a Hammond 272FX, I think I'll spend some time with PSU Designer and see what I can come up with.

 

[Alonzo]

I forgot the last option, sell it all and get a Stereomour II !