Paramount Part Swaps

[Gerry E.]

Hi:

My Paramounts came with aftermarket binding posts which I never cared for.  One of them recently failed, it no longer tightens down, so my friend Boulos offered to replace them for me.  I'm thinking of replacing them with classic WBT 0763 or 0730 posts.  Has anyone used either of these in their Paramounts or other BH components?     

While looking at my Paramounts, Boulos said we could also replace the Xicon 47uF 450v caps with some brand new F&T 47uF 500v that he just happens to have.  Last, he also said we could consider replacing the Xicon resistors to Mills 5W non-inductive types.  Any suggestions as to which of these resistors would be worth replacing?  Thanks!

Gerry         

 

[Paul Birkeland]

Depending on whether you are running the 2A3 or 300B design, the 450V rating of the cathode bypass cap may not be necessary.  (Unless the output tube shorts, which should blow the fuse pretty quickly)

Of the 5W resistors in the amp, the 270 Ohm resistor in the power supply could be replaced.  The Kiwame 5W part is a nice fit here.

The two 22 Ohm resistors in the hum balance circuit are not super critical. 

-PB

 

[boulos]

Thanks PB.  What's usually the voltage across these caps (Gerry is running 300B)? Would 100V rated caps suffice?

 

[Paul Birkeland]

A 100V rating wouldn't bother me, as the target voltage is around 60V for the 300B's.

If you ever switch the amp to 2A3's, don't forget to change these out!!!!

I'm also expecting PJ to weigh in here and also mention that if the parafeed cap shorts, you'll see full B+ on the cathode bypass cap, which would then blow up. 

-PB

 

[boulos]

So then the question is whether to use the F&T cap Gerry mentioned or other 47uF 100V caps -- I'm thinking BlackGate or Elna Cerafine.

If the cap is rated 500V (the F&T), would it be able to withstand full B+?

 

[Paul Joppa]

We have seen enough cases where for one reason or another the 2A3 loses grid-to-ground, or the grid shorts to the filament. In these cases, anything less than a 250v part is likely to fail.

In cases of gross signal overload, which are much more common,  the bias voltage can rise pretty high - I'd specify a 160v part rather than 100 volts.

On the plus side, blowing the cathode bypass cap won't usually lead to other destruction, just nasty corrosive gunk on the surface below.

 

[Paul Birkeland]

On the plus side, blowing the cathode bypass cap won't usually lead to other destruction, just nasty corrosive gunk on the surface below.

It's also incredibly loud! 

 

[Gerry E.]

Multiple small upgrades make a big difference!  They are cumulative in nature.  Actually, not all of these are small but here are the upgrades I (and mostly Boulos!) have made to my Paramounts and BeePre in the past 6 months:

1. Replaced the 300Bs in both the amps and preamp with a factory matched quad of 1998 reissue WE 300Bs.

2. Assembled and installed the BeeQuiet into the BeePre.  Thanks Boulos! 

3. Using an adapter, replaced the 5670/2C51/396A Paramount input/driver tubes with 6SN7s.  Thanks for the suggestion Aaron!

4. Added the Bel-Art Scienceware vinyl coated lead rings to the 300Bs in the BeePre. 

5. Boulos soldered all of my speaker wire driver connections thereby eliminating the alligator clips that were holding everything together.  Interesting note – I have always had a slight channel imbalance in my system.  Replacing the alligator clips with soldering solved the problem!  Boulos believes that at least one of the speaker wires was only touching leftover solder on one of the speaker terminals and since solder is not be the best conductor, it was causing the imbalance.

6. A couple of weeks ago, Boulos upgraded the cathode bypass capacitors, power resistors and binding posts in the Paramounts.  We discovered that the original builder of the Paramounts had replaced one of the power resistors with the same type of Mills resistors that we were using but not the other!  BTW, I won’t mention we didn't notice that the new positive binding posts were grounded to the chassis the first go-round.  Oops! 

All of these upgrades have taken my Bottlehead components to another level.  The overall refinement in smoothness, resolution, definition, impact, tone and treble sweetness have been amazing.  If I had to pick one of the upgrades as the most significant, it would be the BeeQuiet.  If you have a BeePre and haven’t installed the BeeQuiet yet, JUST DO IT!

I’m currently running 1940s Raytheon VT-231s (6SN7s) in the Paramounts but just purchased a pair of Tung-Sol black glass, round plate 6SN7s.  I really like the Raytheon VT-231s but the Tung-Sols should make another incremental improvement. 

Gerry

 

[johnsonad]

Those Raytheon's are my everyday tubes (great sounding!!!!) but for special recordings, I pull out the Tung-Sol's.  Not to brag, but a buddy gave me a second pair as a Christmas present.  He had 10 that he paid all of 10 bucks for a couple of decades ago And, to further wet your whistle, I'm going to try a a pair of 2C22's to replace the 6SN7.  They are cheap, plentiful and reputed to sound better.  I'll report back in my Paramount-ish thread later with results. You can buy the adapters on ePay and most tube sellers have them for 5-8 bucks a tube.

Mills are great resistors and so are film caps as the bypass cap.  There are good quality and nice sounding cheap film caps out there now.  Try the Panasonic caps from Mouser.  They are rated for 500v and are quite small in form.  They can easily be super glued to the bottom of the chassis and have been my go-to starting cap.  Steve turned me onto them in a different post here on the BH forum.

Gerry I can't remember of you are using a HPF to your WE speakers or not.  If the Paramounts are not running full range, you may want to consider a lower value than the 47 uF of the original design.  I'm going to change out my 100uF Panasonics for 1.5uF ClarityCap MR's and see how it sounds.  My 755's are crossed at 80Hz.

 

[boulos]

A couple of weeks ago, Boulos upgraded the cathode bypass capacitors, power resistors and binding posts in the Paramounts.  We discovered that the original builder of the Paramounts had replaced one of the power resistors with the same type of Mills resistors that we were using but not the other!

We used Mills MRA12 for the 270 Ohm power resistors. It was easier to source than the 5W version. The one we found in one of the amp was MRA5, but we took it out.

For the cathode bypass caps, we used Elna Cerafine 47uF 100V. Voltage measurements across the cap at various signal levels (including extremely loud) were within 2V (or 0.2V, I forgot) of the measurement at no signal, which was about 72V.

 

[Paul Joppa]

The high voltage rating on the stock cathode bypass cap is only needed for the direct-coupled 2A3 variant.

 

[Gerry E.]

I'm going to try a a pair of 2C22's to replace the 6SN7.  They are cheap, plentiful and reputed to sound better. 

Gerry I can't remember of you are using a HPF to your WE speakers or not.  If the Paramounts are not running full range, you may want to consider a lower value than the 47 uF of the original design.  I'm going to change out my 100uF Panasonics for 1.5uF ClarityCap MR's and see how it sounds.  My 755's are crossed at 80Hz.

Hi Aaron:

Please let us know how the 2C22s work out.  My 756s run full range but I also use a powered sub.  Since the sub inputs are taken from the BeePre, the Paramounts don't have to run full range. 

I like the idea of limiting the low frequencies to the Paramounts and by extension (pun intended) to the 756s.  Also, a high quality 1.5uF cap is obviously much less expensve than a 47uF.  Hmmm, Parts ConneXion has some really good caps on sale!  Maybe Boulos will see this post! 

Gerry             

 

[boulos]

Maybe Boulos will see this post!   

I'm watching the thread   I'm happy to switch the Elna to a 1.5uF film cap, but isn't that a little low for the cathode bypass cap?

 

[Gerry E.]

I thought that Aaron was limiting the low frequencies in his Paramounts by changing the cathode bypass cap value.  Obviously I was mistaken based on this reply in another thread: 

“You miss read it Gerry. My sub woofers have a built in high pass filter. The signal chain is preamp to the subs (with HPF) then to power amp and speakers. Those frequencies are filtered before they get to the power amp.”

Yikes!  I didn’t realize Aaron was using his subwoofer crossover for this.  In any case, I know there’s a way to limit low frequencies in an amplifier using a capacitor.  Given that I have a BeePre and Paramounts, what’s the optimal way to do this? 

Also, what cap value do I use?  Is there a calculation or calculator for this?  Like Aaron, 80hz or maybe a little higher would be good.  I’m using a second set of BeePre outputs to run my subwoofer, so that has to remain full-range.  Thanks! 

Gerry