Stereomour vs. Tucker 45...?

[johnsonad]

I've not tried the Stereomour. I've had a Fi-X, Bugle and had a JE Labs Simple 45 and another 45 amp in my system. I owned the first two.

There are things a 45 tube does well in my opinion. For full range, it isn't my first choice. The Stereomour configured for 2A3 may work better but you should give a 45 amp a listen in your system before committing to one.  There is probably someone near you that has one you can try.

In my experience, it wasn't  a matter of power output but of tonality of the tube.

[galyons]

Aaron, Did you try it in a Stereomour?  Did you have efficient speakers like Klipschorns? I also worry about its ability to control a woofer. I'm not poaching here...The Stereomour is 850.00 and I'm in Canada so it's more like 1100.00 right now because our dollar sucks.

I have Paramour II -45's, much the same circuit as the Stereomour, but mono blocks and no input selector/volume pot.  My main speakers are EV Sentry IV-A's, 102dB/1W/1M.  The 45's are wonderful, BUT, they do not control the bass as well as my Paramount 300B's or 2A3 Paramours.  I agree that the 45's are best as mid/treble amps.  That being said, I still use the 45's as the full range amps and they are so sweet I soon forget the less than stellar bass.

I agree with the recommendation to quit the internet queries. You said you have 45's.....it's simple....use them!!  The only ears that you need to please are yours.

Cheers,
Geary

[Paul Joppa]

One of the reasons for bass difficulties with 45s is that they have a relatively high plate resistance, so you get less damping of the speaker. This is clearly speaker-dependent, of course. It is possible to tune a speaker for a low damping factor but it is almost never done because it will then sound wrong with a normal (high-feedback) amplifier.

[jdm]

Paul,

Can you provide any advice concerning tuning a GPA 604-8H-II driver in a 9 cu ft vented box for optimum damping factor with a 300B Paramount?

Jim

[Paul Joppa]

Paul,

Can you provide any advice concerning tuning a GPA 604-8H-II driver in a 9 cu ft vented box for optimum damping factor with a 300B Paramount?

Jim

If you can provide the Thiele-Small parameters, I can run some calculations for that.

[jdm]

Thanks Paul.  Great Plains Audio published the following Thiele-Small Parameters:

Xmax (inch) = 0.20
Re (ohms) = 6.80
Vd (cu. in.) = 19.20
Fs (Hz) = 30.90
Vas (cu. ft.) = 16.35
Ref. Eff (%) = 4.87
Qts = 0.261
Qms = 8.49
Qes = 0.270
Vid (cu. ft.) = 0.24

Jim

[Paul Joppa]

I'm getting 10CF tuned 36Hz; with a sand amp it would be more like 5CF - looks like the box is already well tuned for SETs.

[jdm]

The box is tuned to about 42 Hz.  I will experiment with restricting the air flow through the port (2.5"x11"x0.75" slot) with foam or some fibrous material to lower the tuning a bit.

Could you describe how you calculated the box size and tuning for the high(er) impedance amp?

Jim

[Paul Joppa]

I increased the speaker's QE in proportion to the effective source resistance.

Roughly, the tube plate resistance is about 700 ohms; add in the transformer primary resistance plus the secondary DC resistance times the turns ratio squared to get about 900 ohms. The nominal reflected load resistance is the primary impedance rating, 3000 ohms. Multiply QE by 3900/3000 = 1.3 times, and run some software (I'm lazy!)

You can lower the tuning by making the opening smaller. Most speaker design free software will have a calculator. Measurements are better, but it's easiest to measure if you have a 2-channel oscilloscope.

[jdm]

Thank you Paul. If I understand this correctly you used Qe=0.270x1.3=0.351 in a typical speaker design software to adjust for the higher impedance of the amp.

Jim

[Paul Joppa]

Exactly.

[faithintruth]

By the way Paul, is the iron used in the Stereomour supplied by Magnequest?  Any brand name parts?

[Paul Joppa]

No boutique parts - we choose the parts carefully, including listening comparisons, but also try to keep the cost down. The transformers are my own designs.

In another thread the question of a suitable Magnequest output transformer and plate choke came up. The question is at present still unanswered.

[Natural Sound]

Like galyons I have Paramour II's set to run 45's. In addition I have the SEX/Stereomour iron installed. I ran the system for a couple of years with 2A3's. Then a friend gave a pair of 45's and I decided to try them. Lets just say that the 45's never came out. There are arguments for both tubes. But for me, my listening room, speakers (Orcas/Subs) and music taste, the 45 was preferred. As they say YMMV.

As mentioned here previously the 2A3 tube can safely operate in the 45 configuration but NOT the other way around. So if you wire it for a 45 you can tube roll 2A3 and 45's for comparison. Just make sure that the amp and tubes have been given ample time to burn in before doing any critical listening. 

[Paul Birkeland]

  Any brand name parts?

You will find the same level of parts quality in our products that you would find in many Stereophile class A rated components.  This includes the coupling capacitors, resistors, diodes, sockets, and switches, etc.

We select our parts for reliability, good in-circuit performance, and ease of acquisition.  Our high end Tube Repro uses a lot of botique parts, and it can take me days chasing down multiple vendors to find what I need to complete the build.

-PB