Iron upgrade for a Paramour II

[Natural Sound]

First off, I'm running relatively stock Paramour II's. I may entertain the possibility of shunt regulation in the future. For now they are not.

I'm dying to get the stock Speco output transformers out of the amps. I'm having a hard time deciding on which parts to buy though. I've been doing a lot of reading in the archive. The more I read the more confused I become. I've fallen into, "analysis paralysis." I could use some help to knock me off the fence.

Here is what I gather so far. The BH-5 outputs (Similar to TFA-2004 Jr.) and BH-6 plate chokes are less suitable from a technical standpoint for 45 use. The operating points cannot be optimized for maximum power and the damping factor is poor. But some have compromised because this is a "great sounding transformer." After all its all about the sound, right?

The other option would be the EXO-45/46 Output transformer and a set of BH-2 plate chokes or  BCP-15 (50 henries at 40mA) With this combo the operating points can be better optimized and the damping factor is better. However low end bass may be less using this output transformer.

With that in mind I have a few questions.

1) Which do you think is better and why?

2) What is the definition of, "damping factor" and how does it effect the sound?

3) Will a parafeed cap of 10uf be OK for either option?

4) If I have a choice of output impedance, which would be better for a pair of orca's and 2 subs, 8 or 16 ohm?

Thanks, Tom

[Grainger49]

I don't know if Bottlehead sells the Stereomour transformers but they would be better than the Specos by a pretty good margin.  I am sure that Magnequest should have something to use as well.

Damping factor is the ratio of the speaker impedance to the amplifier's internal output impedance.  With some speaker designs it is important.  It is not as important in the designs that operate on 3WPC. 

Parafeed caps need to match the transformer impedance and speaker impedance.  So the "right" one varies with transformers and speakers.  PJ says to buy some in a range, cheaper ones, and find the best value.  Then buy a good one.

You should ask Clark or Molly the last question.  Try their site or post in the Blumenstein thread in the speaker section.

[2wo]

Well, The BH-5 will give you the most flexibility if you want to try other tubes. I had them in my SR-45 and if I had not got a great deal on a set of nickel EXO-45's they would still be in there. The difference is not huge, the EXO is a bit sweeter in the highs and mids. The BH-5, a bit more extended in the bass, maybe but still plenty sweet.  I go to a sub at ~70Hz 

I would say, if you plan to stick with the 45 go with the EXO...John

[Paul Joppa]

...  1) Which do you think is better and why?

Hard to choose. For the Orcas, I might lean to the 5k to get the better damping factor. See #4 below.

...  2) What is the definition of, "damping factor" and how does it effect the sound?

As Grainger said, except that in my opinion it is important for all speakers. Very few are designed for a small damping factor which is what SETs have. Some speakers will become tubby with bass lumps if the damping factor is too low; a very few that are over-damped with solid-state amps can become livelier and more "present". Sorry for the non-specific audiospeak!

...  3) Will a parafeed cap of 10uf be OK for either option?

No, the 10uF is specific to the BH-5/BH-6 combination. For the 50 henry/5K combination, use 4uF (more or less).  With 40 henries and a 4K transformer (OT-2 and PC-3 as in the Stereomour) it's 5uF. These are flexible numbers within the range of half to twice the calculated value, depending on the particular speaker.

...  4) If I have a choice of output impedance, which would be better for a pair of orca's and 2 subs, 8 or 16 ohm?

As Grainger says - talk to Clark or Molly. They have a lot of experience with the Stereomour which is just a stereo Paramour.

[tsingle999]

I have the tfa 2004 jrs with the bh2 choke and 12 uf caps just to mix it up a bit. Sounds great to me...

[Natural Sound]

Thanks for all the replies so far. I didn't make it very clear but I plan on keeping these amps as 45's. Somehow during my edit I took that out. I know that he 45 likes to see a higher impedance so I'm leaning towards the 5k primary transformers at this time. Especially after what John said. He has experience with both of them both in his system. Since I'll be running Orca subs with their own amps I'm not too worried about losing anything in the lower bass area.

John, what parafeed cap did you wind up with?

[2wo]

I am using 6.8uf, with a BCP-15. I have not experimented with other values. That will wait until I rebuild the amp...John 

[braubeat]

I have never heard these myself, but several people who have think these are the best transformers for parafeed that Mike makes. Also one of the most expensive, but not all that much more than TFA-2004. A pair of these in a 45 amp is on my Bucket list. Also the Dowdy plate chokes.

Michael

[awsjr]

does the parafeed cap need to be 630v or will a 400v rated capacitor be ok ? this would be in the SR-45 amp...thanks