Paramour 2 -> Custom SR45 conversion - (an evolution, with photos)

[Mikey]

Bottlehead Paramour II Amplifiers: (Mechanical Assembly)

I'm building a pair of Paramour 2 amps, and I thought I'd share my progress with the group!


Initial Impressions:

The Paramour II monoblock amplifiers share the same footprint as the other Bottlehead products. A quick glance at the manual reveals a simple circuit that should prove easy to build and modify, with a well thought out layout. The new chassis plate gives the kit a much higher quality feel, with more room for future modifications.


Finishing the Parts:

- The chassis plate is painted with a coat of clear lacquer.
- The transformer end bell is finished with satin black lacquer.
- The transformer lamination stack is painted with high heat flat black paint.
- The base is finished with Watco Danish oil.


Mechanical Assembly Notes:

The mechanical assembly was very straight forward. Exercising all the restraint that I can muster, I am building the amps exactly as described in the manual….without any modifications. So far the assembly instructions are VERY clear and concise, with plenty of detailed step-by-step photos.

Here are a few photos of the completed mechanical assembly:

















Stay tuned, wiring next….

Mike

[Mikey]

Bottlehead Paramour II Amplifiers: (Electrical Assembly)

Paramour II progress report!


I realized yesterday that I haven't yet updated the group on the completion of the amplifier wiring...


Electrical Assembly Notes:

The electrical assembly was very simple, following the well written manual. The layout is very clean and logical, with components placed on the chsssis plate according to their function. All resistance and voltage checks were spot on after finishing up the wiring. After adjusting the hum balance pots, both amps were very quiet!

Here are a few photos of the electrical assembly:















Listening impressions are next....

Mike

[Mikey]

Bottlehead Paramour II Amplifiers: (Octal Driver Conversion)


So…..how do they sound?

The speakers I used for listening were my TAD 4001 / TAD 1601A combo. They are roughly 97 dB efficient, with a 16 ohm compression driver, and an 8 ohm 15” woofer. The amps were used on the drivers, running from 650Hz and up.

The source I used was a Meridan 508.24 CD player. At times, I also used my modified Empire 208 turntable and Progressive Engineering Phono Preamp.

The preamp is a highly modified Bottlehead Extended Foreplay III

My loudspeakers are ruthlessly revealing…..all parts of the signal chain are very audible. From the beginning, the amps provided good tone and timbre. The amps have very good purity and decent resolution, no doubt due to the very simple circuit. Even though these Paramours are bone stock, they show great potential and are a clear notch above the SEX amp I was previously using on the compression drivers. They step out of the way and let the music through….

The amps remained stock for a few weeks before the new octal driver tubes were installed. The 12AT7 was replaced with a 6J5 (basically an octal version of the 76 tube). The C4S load was unmodified, and a 431 shunt regulator was added to the circuit board to obtain a regulated bias voltage for the 6J5 driver.

The 6J5 has less gain, but in my system this is not a problem. The end result is slightly smoother midrange, and a little bit more top end sparkle.

Here are a few photos of the conversion:











Stay tuned! More modifications are in the works….

[Mikey]

Bottlehead Paramour II Amplifiers: (Magnequest Iron Upgrade)

I had plenty of free time over the Thanksgiving holiday, so I decided to install some Magnequest iron in my Paramour amps. Specifically, I installed the BCP-15 plate choke and the EXO-45 M6 output transformers. The original Triad C-7X choke was moved to the power supply to create a C-L-C filter (replacing the 270 ohm resistor). The parafeed capacitor was increased to a 12uF Solen, since that’s what I had on hand.


The result?

Holy cow! I wasn’t prepared for the difference I heard! Any remaining ‘etch’ or ‘grain’ that I heard with the stock transformers was completely banished. The sound became much more liquid and realistic, with a much smoother midrange. The top end was also more extended and less harsh….cymbals sound very real. I cannot comment on the bass response since I don’t use these amps full range. All in all, the amps became much more engaging, and I could listen to them for hours.

While the previous modifications I made to the amps resulted in audible improvements (driver tubes, coupling caps), this iron upgrade simply ‘transformed’ the amps. About the best analogy I can come up with is: The shade-tree mechanic modifies his carb, ignition, camshaft, etc., while still restricting the engine with a stock single exhaust system. Once that puny exhaust system is replaced with a nice big set of free-flowing dual exhaust pipes, the engine can come alive and realize its full potential!

Had I started the modification progression with the transformers, I’m fairly certain the audible differences between driver tubes and coupling caps would be much more pronounced. Before you ask, I’m not going back to the 12AT7 (grin)!


Here are a few photos of the new iron:











Stay tuned! 45 conversion next….

[Mikey]

Bottlehead Paramour II Amplifiers: (45 Conversion)

A few days ago I converted my Paramour II amps over to utilize 45 output tubes….

The conversion was very simple; replacing the 1.1K output tube cathode resistor with a 1.5K resistor, and installing a 1.5K resistor in place of the 270 ohm power supply choke. While those two changes were all that were actually required for the changeover, I took the opportunity to do some ‘rearranging’ under the hood….

Since I had to replace the cathode resistor anyway, I chose to swap it with a chassis mount style resistor from Vishay-Dale. This also necessitated replacing the bypass capacitor, as the leads on the original bypass cap were not long enough.

I replaced the original 10 ohm hum balance potentiometer (and its associated 22 ohm resistors) with a 50 ohm precision ten-turn pot. Also, I relocated the power switch and reconfigured the interstage coupling cap scheme to eliminate some wiring.

Lastly, I relocated the plate choke and output transformer to free up some additional chassis plate real estate. I stacked the two pieces of iron (as in the S.E.X. amp) to make room for future modifications…..stay tuned!


The result? A smoother and more natural sounding amplifier! To my ears, the 45 seems more ‘distinguished’ than the 2A3, although slightly lacking in ultimate power output. In my system this is of no consequence, as the amps are directly driving a pair of 110dB compression drivers. Listening to these amps has become even more enjoyable and engaging! I’ll turn on my system with the intention of listening as background music, but get drawn into my listening chair for hours…..one LP (or CD) leads into the next, and before I know it, it’s midnight!

If you’ve got the high-efficiency speakers to take advantage of this modification, I urge you to try it! I don’t think you’ll be disappointed.



















Shunt regulators are on deck….

[Mikey]

Bottlehead Paramour II Amplifiers: (Oil Parafeed Capacitors)

I did some more component 're-arranging' the other night so I could try out some ASC oil capacitors in
place of the Solens I was previously using. I moved the plate choke and output transformer back underneath
the chassis plate, and installed some new binding posts.

A 15uF ASC capacitor was used, since that's what I had on hand! Here are some photos of the retrofit:









There was an audible improvement over the Solen cap I was using previously....just a hint more smoothness.
The sound seemed a little bit more 'relaxed,' for lack of a beter term.

That chassis plate sure is getting a little bit shopworn, huh? :-)

Mike

[Mikey]

Bottlehead Paramour II Amplifiers: (Shunt Regulator Conversion)

With all of the inclement weather in New England this weekend, I had plenty of time to add shunt regulators to the power supply of my Paramour 45 amplifiers.

A 6SN7 was chosen for the shunt regulator tube. This tube (along with its associated circuit board) was mounted on the chassis near the 6J5, and additional heater wiring was run back to the power transformer to heat the 6SN7 filaments. At the moment, I’m only using one half (one triode) of the 6SN7, but I may try both triodes in parallel to see if there is any difference.

I wired the original 270 ohm power supply resistor in parallel with the existing 1.5K (in the CRC filter) to raise the voltage prior to the shunt regulator. The shunt regulator was spliced into the circuit directly after the CRC filter and the B+ was taken from there….

The result?


WOW! The first thing that I noticed was a tremendous improvement in spaciousness! The sound seemed much more ‘three-dimensional’ and palpable….not simply emanating from the loudspeakers, but completely surrounding the loudspeakers with a very realistic soundstage.

After some more time with the amps, it seems that there is an increase in refinement or ‘elegance’….for lack of a better word. Realism is improved, and I can just sit and listen for long periods at a time without a hint of harshness or fatigue!

Lastly, although all of the filaments are AC, the amplifiers are VERY quiet. In my system, the amps are wired directly to 110dB compression drivers, so any noise at all will become very easy to detect. I have to place my ear right up to the horns to notice only the slightest bit of ‘tube rush,’ and as a result the music pours forth from a very black background!













Another home run by Doc B. and Paul!


A few other tricks are still in store…

[Mikey]

Bottlehead Paramour II Amplifiers: (Magnequest Iron Upgrade, Part 2)

Since the Bottlehead SR45 was developed with the Magnequest TFA-2004 Jr. in mind, I decided to call Mike LaFevre and see if he had any of these output transformers in stock. He happened to have a pair of pinstripe units on the shelf, so he sent them to me at the beginning of the week. They arrived yesterday, and I installed them into the amps last night.



The result?

HEY! Who added the super-tweeters to my loudspeakers?! I was expecting a subtle improvement, but not this! The top end was MUCH more extended and airy, by what seemed at least an additional half octave or so. All of the goodness that was there with the EXO-45’s was still there….the resolution, clarity, musicality, etc. With the extended frequency response, cymbals sound much more realistic, and the overall presentation has much more ‘palpability’…..without being harsh or edgy. Now I know why Doc B. was so excited about these amps a few months back (smile)!

These amps have evolved into a new reference for me. Quite simply, they are now among the finest amps I’ve ever heard in my system! I’ve still got a few more things to try, but I honestly don’t know how they can get much better. Once that last bit of experimentation is wrapped up, I can begin constructing a pair of new (larger) chassis plates and bases.


Here are a few photos of the new output transformers:









Chassis redesign next…..