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Paging mulveling... your W5s are running!

Well, a set of four RCA 12BH7A beat out everything. And I tried about every imaginable combination of tubes of the types being discussed.

The GE 5814 in the front with the RCA12BH7A in the second tube position, was a VERY close second. In fact, I'm going to give Mike a pair of the GE 5814s, just in case it might actually sound better in his room. It's that close...

In this case, though others might have other results with 6CG7s... the 12BY7As win... at least to my ears...

Regards,
Gordon.
 
The 12BH7's are a good choice. I tried it on my extra W5M and the sound was much improved. I do prefer the 6CG7's but the 12BH7's are a close second.
Only thing to mention is I added a separate 3A filament transformer in each amp to take some of the strain off the power transformer. Both the 6CG7 and the 12BH7's have a higher current drain then the 12AU7's. The original PT's on the W5M's are very well known for going bad.
 
The only times I see W5 power transformers in any numbers, is when people are using them with a) the wrong rectifiers (a 5U4 is NOT an acceptable sub for the 5R4!), b) bad coupling caps (leaking, throwing off the bias), c) bad output cathode bypass caps (again, throwing off the bias), or d) improperly biased output tubes.

This amp now has NONE of those issues.

Also, the heater draw must be considered, in context of the units NOT using an umbilical-connection preamp (the WA-P2). That's another two tubes... a 12AX7 and a 12AU7. That is .6 amps... the same difference between the change from 2 12AU7s and 2 12BH7s...

Also, given that the PTs in these amps don't get over about 120 degrees, EVER... I think they should be just fine...

And, AFAIK... isn't it the output transformers that are sometimes problematic (the '309s) instead of the power transformers on these amps?

Regards,
Gordon.
 
Lucky I have the 16458 OPT's as the 309's can be a problem.
Your right about what can ruin a power transformer but I've sure seen and heard about many of these having bad ones in them. The W5M PT's seem to be much more trouble than what was used in other tube amplifiers... that I'm sure have had the same aging issues.
 
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Just got these home today, and finally fired them up an hour ago.

WOW!! Talk about unlocking the untapped potential from my Kensingtons...and it's not like my other amps were GARBAGE. In fact, they're all very very nice amps - a Dewick't MC2100, a restored/upgraded Eico HF-87, and a restored pair of W4 done by none other than Gordon.

The most crucial factor for me, is the midrange. I bought the Kensingtons because of the glorious mids they're capable of (that's not to say they aren't killer across the whole spectrum). I need upstream gear to match the sweetness AND resolution of the speakers without noticeably holding them back, which turns out to be harder than I thought. The W4s came closest to the mids I wanted, but lacked in bass impact compared to the McIntosh/Eico. The Eico had the best overall balance of attributes but lacked that touch of tube magic (at least with the Teslovak EL34 and Sylvania orange-label 6sn7gtb tubes I've got in there). The McIntosh had the best bass impact and surprisingly competent mids, but could get just a TOUCH harsh when pushing out higher volumes.

These Gordon-rebuilt W5s beat them all. The mids are beyond anything above, the bass impact AT LEAST matches the McIntosh, they have that magic "holographic" imaging, and the rendering of music is so perfectly well-integrated and coherent it reminds me of the best high-end headphones in that regard (read: single driver, no crossover, no room acoustics issues - I am/was a hifi headphone lover, btw).

In short, I like these amps. :yes:

THANK YOU Gordon. Wonderful work :)
 
That is Super! glad you are satisfied. I ran 12BH7's in mine for months before taking the "Plunge' and going 6CG7. I have three W-5m's so I was able to do A&B tests... I slowly changed them all over to 6cg7's after the listening tests. The modification is easy and Gorden could do it in an hour....
That said, at this point in my tweaking I have found pre amp tubes to be a major, major component in crafting the sound of my system. I have a PAS-3 and have been rolling tubes to find the best combo. At present I'm running Tele's in the phono section and Raytheon's in the line section. The selection of these seems to be much more detectable than the differences in the 12BH7/6CG7 debate.
Gordon by the way I think there are two 12Ax7's and a single 12Au7 in the WA- P2 preamp.
 
I figured the 12BH7s would be the ticket... BECAUSE they delivered the best mids, without really giving up significant ground anywhere else. Everything else seemed to give up more, for what they gave in return... so, 12BH7s it is! :thmbsp:

As for the 6CG7s... it's a great tube... but, for whatever reason (I'm guessing the slightly higher transconductance of the 12BH7 being better suited to drive 7581s under this loading?), the 12BH7 won. Now, on other speakers, I could see someone liking the 6CG7 better... it seems, at least with the Sylvania and RCA cleartop 6CG7s, to MAYBE have JUST a little more bass impact than the 12BH7. If your speakers are hard to drive in the bass, this might make the difference enough to tip the scales. But, in this case... the Kensingtons have PLENTY of bass energy on their own... so, they didn't need the additional help.

OH- I almost forgot- one other possible variable- I changed the second-stage couplng caps (between the phase inverter and the diff amp) from .1uf to .22uf. That MIGHT have changed the environment for the 12BH7/6CG7 comparison enough to tip things over to the 12BH7. In any case, I like it better with those caps at .22uf (the value used in the W4, BTW- and since the 12BH7 and 6CG7 are more like the 6SN7 used in the W4 than they are to the 12AU7 used in the W5, the additional cap value seemed logical)... and would recommend that change for anyone thinking about changing out the input tubes in any W5...

BTW: Mike, I can't remember... what preamp are you're running?

Regards,
Gordon.
 
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Glad the W5M's worked out mulveling! They are a great amp and Gordon did a great job. Like kirkleclaire stated, if you have a tube preamp the tube tweeking will keep you busy as well. What are you using for a preamp?
I've tried a tube Ampex, a tube Marantz and a solid state Threshold preamp. I've found that a mixture of Tele. 12AX7's, RCA 7025's and Tung-sol 12AU7's have worked the best in the tubed pres. I need to do more comparison with tube swapping but it takes allot of time. I actually prefer the sound of the solid state pre with the W5M's (probably because of its great phono section) but I need/use it in another all solid state system. For now I need to keep rolling tubes until I find whats works best.
Anyway...:yes: enjoy the amps!
 
Preamp

Well Gordon, remember that Kevin Gilmore designed headphone amp in a HUGE black box I brought in for you to swap gain resistors? For my preamp I'm using another, smaller version of that (Headamp Gilmore V2). The differences are:
* An RK27 pot instead of the stepped attenuator. I can't stand using a stepper with speakers.
* A slightly scaled-down power supply - the bigger one was meant for a fully balanced circuit.
* RCA preamp outputs, which have 10 ohms resistors in series to guard against shorting loads - as the output impedance of the amp is otherwise 0.1 ohms
* Two switched RCA inputs (Turntable, Apple TV :)).

The designer's circuit description is here:
http://www.headwize.com/projects/showfile.php?file=gilmore3_prj.htm

Kind of odd to pair a preamp with that design philosophy up with a TUBE AMP, but hey it sounds great! I've compared it to the Eddie Current Zana Deux (http://www.eddiecurrent.com/Zanadeux.html), and found the Gilmore to sound faster & cleaner without sacrificing the other important attributes of sound quality. Hence, I recently sold the Zana Deux because it costs a HELL of a lot more. In fact, that's one of the sacrifices I made to fund the Kensingtons :D

In the future, I might look again for a more full-featured, speaker-only high end preamp. A remote, even via a motorized RK27, would sure be nice. For now the little Gilmore gives an incredibly clean, transparent sound quality with just enough functionality, and the thing only cost me $200 :thmbsp:
 
I'm just thinking the same thing. I've got a few preamps in the closet waiting to be used. I'm also in Marietta / Kennesaw area.
 
Looks great, Gordon!

I'm about to plunge into my refurbs and was wondering why you opted to use new blue multis for the filter caps? I'm planning to leave the classic silver caps and mount some 47uf and 33 uF caps underneath the chassis below the power tranny.

Just wondering...
 
Andyman said:
Looks great, Gordon!

I'm about to plunge into my refurbs and was wondering why you opted to use new blue multis for the filter caps? I'm planning to leave the classic silver caps and mount some 47uf and 33 uF caps underneath the chassis below the power tranny.

Just wondering...
Click to expand...

Space. It's kind of tight in that little area.

If you were willing to run jumper wires, you could put them in the other side of the chassis, next to the input (under the power transformer). However, that could lead to noise pickup, due to increased lead length (antennas). So, I opted to leave it the stock wiring arrangement, as closely as possible, in that area. And it worked out great...

Regards,
Gordon.
 
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