Paramour II 45's With S.E.X. 2.0 iron upgrade

[Natural Sound]

I thought I'd drop in with a progress report. I got the new iron installed today and got one of the amps completely wired. The resistance and voltage checks were good (I think). Something is bothering me a little though. The Paramour II manual notes that the resistance readings will be different with the 45 tube and the adjusted measurement is listed. Mainly a difference of 1100 ohms for a 2A3 vs 1500 ohms for a 45. Mine measure 1500 ohms so all is well there. When I move on to the voltage check section there are no voltage measurements for the 45 only the 2A3. I'm assuming that I'll see less voltage on the B+ line and I do. But without a target voltage I'm not 100 percent certain. So for my sanity, can someone take a quick look and reassure me that I'll be OK? One thing I noticed is that the plate voltage is 270VDC. The RCA data sheet says that the maximum voltage for the 45 is 275VDC. So I'm pretty close to the Max. Then I looked at a couple other sources and they say that the maximum plate voltage is 300. That's where I'm a little confused.

Measurements made with mains voltage of 119.6

Term# / Manual / Measured
P2          136          127.7
P3          130          126.5
P4          -58          -51.9
P11      308          295

1            295          270
7            -58          -50.9
9      140-210    147.8
10          -58        -51.6
11        308        295.4
14    140-210    147.8

A1      .17            .39
A2      295          270
A3 Close to 0        0
A4      .17            .39

B1    140-210  147.8
B3    1.56          1.55
B4    3.15          3.16 (VAC)
B5    3.15          3.16 (VAC)
B9    3.15          3.16 (VAC)

 

[Natural Sound]

Well I finished the second channel this afternoon and the resistance/voltage checks were almost identical to what I posted above. So I gave the hum pots a tweak, put the amps in the rack and hooked up the FPIII. I'm still interested in hearing what some of the more experienced bottle heads have to say about my concerns above. But I couldn't wait any longer.

My initial impressions are quite favorable. I have no way to verify this but my subjective opinion is that I gained a full octave in the upper register. It's almost as though the orcas have a tweeter sitting on top of them now. I never felt that the orcas were lacking in this area but now they are even better, much better. The mids that were always very, very good  have lost a slight edgyness that would come through in certain recordings with the stock iron. And I got a nice bump in bass/mid bass region. I may need to tweak the orca subs a bit but I'll wait to get a few hundred hours of run time on the new parts before I do. Overall this was one of the best "bang for the buck" upgrades I've done in a while. Great job Bottlehead!

In summary this is what I changed.
1. New Iron. SEX 2.0 iron upgrade (same iron as Stereomour) replaced speco output transformer and Triad plate choke.
2. Triad plate choke repurposed as a power supply choke. Adjusted series PS resistor for 45 use and added an extra filter cap.
3. Generic polypropylene interstage cap and Solen parafeed cap replaced with new ClarityCap ESA's. .1uF and 5.6uF @ 630V.

Tubes are RCA Cunningham 45 and a Telefunken ECC81/12AT7.

Gotta go, I have music to listen to. Thanks again Bottlehead.

 

[johnsonad]

Nice work! I too am a big fan of the 45.  Keep us posted as they continue to break in!

 

[Paul Joppa]

Excellent!

Yes indeed, 275v plate to cathode was the design target for the 45. I see -51v bias, which is 34mA, almost exactly the target 35mA. Enjoy!

 

[Natural Sound]

Thanks for the reply, Paul. That gives me the reassurance I needed to tell me that I was on target.

If its any indication of how much I love this upgrade, I put the amps in service at 4 pm mountain time. It's almost midnight and I'm not finished with my test drive yet.

.

 

[jrebman]

Hi Tom,

Wow, hit that 45 operating point right on the head!  So, when did the listening session end?  I love when that happens and have done it myself several times - going 10 or more hours flipping through tunes on the computer server also makes it too easy to do that -- especially for somebody who grew up with LPs and cassettes and who normally listens to album sides or full albums at once and is generally not a big fan of playlists.

Good stuff, and as I said, I'll soon be trying  this opt in the SR-45 to see what it does.

Nice going!

-- Jim

 

[Natural Sound]

Jim,

I went till about 1:30 am and then ran out of steam. When I got up at 8 this morning I fired it up again. I plan on playing it all day and then sit down for a listening session tonight.

Tom