Paramount V1.1 300B/2A3 Monoblocks Pair Kit Specs
For Paramount we chose the latter approach, and Paul Joppa created a worthy heir to a legacy of top end Bottlehead DHT amp kits that include Afterglow SE 2A3, B-Glow SE300B Paraglow parafeed SE2A3, and Parabee parafeed SE300B. Paramount is our finest high quality single ended, parallel feed, directly heated triode amplifier kit, consisting of a pair of monoblock amplifiers that can be configured as 8 watt per channel parafeed SE 300B amps or 3 watt per channel direct coupled parafeed SE 2A3 amps. Parts are supplied to allow creation of either circuit, with the builder choosing either 300B tubes or 2A3 tubes to be included with their kit. Conversion from one circuit to the other is possible with some parts changes and some rewiring.
The maximum power output of up to 9 watts in 300B configuration allows the Paramount to work very well with high end loudspeakers of sensitivities as low as 93dB. The option for wiring the circuit as a 3W direct coupled 2A3 amp means that Paramount will deliver the musical subtleties that high sensitivity horns are so good at picking out. Wired either way you get the articulate bass, sweet midrange and extended treble that parallel feed, active loaded and shunt regulated Bottlehead products are known for.
We consider this a Skill Level 3 kit. It has some PC boards and lot of parts. It will probably take three or four evening to complete the two monoblocks. It would make a great second kit for more experienced builders, though quite a few first timers have completed them as well.
The circuit – new and improved, with soft start
The new input stage uses a 5670/2C51 tube. One half is configured as an actively loaded voltage amplifier using our Camille Cascode Constant Current Source for super quiet, dynamic, linear performance. The other half of the 5670 operates as an actively loaded hybrid shunt regulator for the voltage amplifier, giving the driver stage great extension of both bass and treble information.
Here’s what the new improvements are about –
Firstly the new driver PC board has a soft start function. This delays the B+ to the plate of the driver tube for about 30 seconds at startup. I should note here that once fired up, the amp will need to sit for about 20 minutes after you turn it off for the circuit to “reset” itself and function with the soft start. This was added in response to a user who was using some exotic 2A3s in the direct coupled 2A3 version of original Paramount and experiencing those 2A3s arcing at startup when hit with the driver plate supply B+ before the filament could heat up. This new soft start circuit resolves that issue, assuming that the user takes care to wait the specified time before restarting.This should not be an issue in the cap coupled 300B version. However the soft start may be useful in extending the lifetime of other tubes as well.
Secondly, the zener diode string has been beefed up. The original string worked fine unless you goofed something up in the build that overstressed it. The new string is much more tolerant of errant solder joints, miswires, etc. The circuit has been stress tested by Doc B. inadvertent-, uh, personally.
The MJE5731As on the new PC board now sport heat sinks to extend their reliability as well.
One of the most noticeable changes is that we have gone to a 5670/2C51/WE396A tube as the driver. Why? Partly because a lot of folks found that the 12AT7 had to much gain in their system which led to hair trigger volume controls and a bit more transmission of the noise floor from front end equipment than they liked. The 5670 has a mu of 33 as opposed to the mu of 60 of the 12AT7. The 5670 is also a very sweet sounding, particularly linear tube, that we feel is step up sonically from the typical 12AT7. There’s enough variety of brands to make tube rolling interesting and it is not prohibitively expensive.
The output stage may be configured for either a 300B tube or 2A3 tube using cathode bias. A custom Bottlehead plate choke loads the output tube and the output is via a high quality parallel feed coupling capacitor and custom Bottlehead parallel feed output transformer with 4,8 and 16 ohm taps to work with a broad range of speakers. In 300B configuration the two amplification stages are R-C coupled. In 2A3 configuration the additional voltage headroom is used to employ direct coupling between the stages. Both configurations use zero feedback.
The power supply
A custom Bottlehead power transformer supplies Schottky rectified, choke filtered DC to the 300B or 2A3 filaments and high voltage is supplied to the driver stage shunt regulator and the output stage plate choke via smooth sounding Schottky rectifiers and a conservatively designed CRC filter for quiet operation. The power supply components mount on a compact PC board that attached directly to the terminals of the power transformer for a very efficient layout.
The chassis
The chassis layout utilizes the latest 8″ x 10″ format as employed in the S.E.X. amp and Foreplay III kits. Each monoblock’s grained and laser cut aluminum plate is .080″ thick, and includes our unique Hole Shrinker socket adapter which allows for future experimentation with octal based tubes in the driver stage. The chassis plate sits in an attractive Pacific Northwest alder wood base that you assemble and finish to taste. All of the inductors are mounted under the chassis except for the power transformer, resulting in a clean look that highlights the beauty of your glowing tubes. Input, output and power entry jacks are at the top rear of the chassis plate. A easily accessible power switch sits at the top front of the chassis, and an equally easy to access hum balance pot resides next to the output tube.
Component quality
Laser cut chassis plates and alder wood base kits are made for us here in the Pacific Northwest. Our custom Bottlehead inductors come from Northern California. Rectifiers are Cree high voltage Schottkys for B+ and high current Schottkys for filament DC. Capacitors are a combination of Panasonic ECPQ (U) polypropylene, Solen polypropylene, and Panasonic TSU electrolytic. Resistors are carefully selected for each application and include carbon composition grid stoppers, 1% metal films for precise voltage and current tolerances, and overrated wirewound resistors for output tube cathode loads. Hookup wire includes both Alpha teflon insulated 22 ga. solid core copper wire for high voltage connections and Belden solid core shielded twisted pair for super quiet signal wiring.
Specifications
• Power: 300B – 8.5 Watts, 2A3 – 3 Watts
• Bandwidth: 16Hz to 34kHz at -3dB
• Sensitivity: Full power at 1.56v (300B); about 0.94v (2A3)
• Gain: About 8 at the 8 ohm tap (21.5 dBV)
Will Paramount work with my 90 dB speakers?
This question is always a tough one to answer because everyone has a different taste in music style and playback levels, and everyone has a different listening environment. While some folks are happy using amps as small as 2 watts output with 90dB sensitive speakers, we suggest 93dB minimum sensitivity speakers for use with the 8 watt 300B version of Paramount and 97dB minimum sensitivity speakers for use with the 3 watt direct coupled 2A3 version of Paramount, as a rough guide. However, if you have tried other low powered amps with your lower sensitivity speakers and liked what you heard, chances are Paramount will sound great to you as well.
How hard is it to convert a 300B Paramount to a 2A3 Paramount?
Simple! Everything but the tubes is already in the kit. Here’s how
Impressions
So finally got the Paramounts fired up and I must say I’m impressed.
My Paramours are some very fine sounding amps. But even in their obviously un-broken-in state these are definitely a step up the sonic ladder. They still retain that wonderful laid back quality but seem to have put a death grip on my Fostex FE108 Sigmas and achieved a level of driver control that the Paramours were never quite able to.
Can’t wait to get them broken in and start messing with them. See what some adamantium in dinosaur lacrimation caps and unicorn eyelash resistors can do to it.
Thanks to all those who put their blood, sweat, and tears into this great design and helped me figure out what I blew up in order to get these suckers running.
–ssssly, on the Bottlehead Forum
I have been playing with my Paramounts for about 8 months now, and I must say that they are fantastic. Superquiet, top resolution and great soundstage. My amps are set up with 2A3s. Hope you sell a bunch of these amps.
–Roger, on the Bottlehead Forum
The fine folks at BH Headquarters got my problem mono block up and running in no time flat!
Thanks so much and I’m really excited to get them in the system and burned in…they sounded great right off the bat, just more clarity in the midrange and the upper end sounds so natural and real…the changes were noticeable right away.
Thanks again to the Bottlehead Team!
Best,
John
–InfernoSTi on the Bottlehead Forum
Just finished my 2a3 Paramounts. Wow do they sound great! It’s like liquid gold is coming out of my speakers. While not as forceful as my 300b DRD amp, it is much more liquid sounding. Hearing nuances in the music I didn’t hear before. I am very impressed, thank you Bottlehead.
Here in Norway, we are already at sunday evening (9 hours time difference). I have played for about 8 hours today, and the amps are already much better than right after the first power up. Looking forward to more music from my system. It sounds great now. What amazes me is that they are dead quiet on 107dB horns.
–Roger, on the Bottlehead Forum
I thought I would give an update on my Paramounts. I have put quite a few hours on them since my last post, so if there’s a break-in period for the Soft Start upgrade kit (plus one new V-Cap), I have probably passed it. Either way, the Paramounts are sounding great! I have heard a number of 300B amps before and didn’t like most of them. This includes Wavelength Cardinals, Wright Sound Mono 8s and a couple of very high-quality, custom-built amps.
It wasn’t that they sounded bad, it’s just that they sounded boring. I don’t know if it’s the Parafeed circuit, solid state rectification, DC heating of the output tubes or some combination of all three, but the Paramount sounds anything but boring/lifeless.
–Gerry E. on the Bottlehead Forum
I just finished building my Paramount 300Bs with soft start. I did all the proper checks and adjustments and sat down to listen tonight in a darkened room. I set the volume to what is a reasonable level and started a CD. It was like sitting in a black hole there was absolutely no audible background noise and then the music just came wafting out of the darkness. It was like the musicians were sitting in the room with me. The tubes and everything else have not even had a chance to burn in yet so I can’t wait till I get more hours on it. These amps are amazing I am hearing detail I never heard before. Tomorrow night the records go on for the real test.
The system is Seduction Phono, Extended Foreplay, Paramount 300B, Cambridge Azur 650C CD, Kenwood KD600 with Ortofon 2M Black and ASW Cantius Speakers (91db)
My intention is to add another pair of Paramounts and bi-amp the speakers at the same time I am doing the conversion to my Revox B77 to run at 15IPS and then I am going to get the Eros Tape Head AMP for it. I can’t quite afford the larger tape rigs yet and I am running out of space for now.
Paul and Doc keep up the good work the products are fantastic and I can’t wait for the 300B Pre-Amp.
Cheers;
Mike
–mchurch on the Bottlehead Forum
Arrived safe and sound minutes ago. I don’t believe that Thank You is said often enough today. Well packed, immaculate assembly (Bottlehead hat tip to Shawn) and the best sound of my 46 year gear collection. I couldn’t be more pleased with your service and amplifiers. Inaugurated with St. James Infirmary with much more music to come. Well done, from a grateful customer and fan!
John Schweiger
Paramount with headphones?!
Photo courtesy sridhar3
From the July 2010 Seattle HeadFi meet –
“did hear the speaker amps that the k1000 was connected to (Paramounts). If the headphone amps (Crack, S.E.X.) sound as good as the speaker ones then I will be sad that I never had the opportunity to take a listen. “
HeadFi member Kingstyles, on the HeadFi Forum
from the October 2010 Seattle Head-Fi meet
I can’t really capture everything I heard but I wanted to mention the various excellent sounds coming from the Bottlehead room. This was my first time hearing the AKG K-1000’s and simultaneously hearing them coming off of a pair of beautiful 300B monoblocks (the Bottlehead Paramounts, I think Doc said). This combo should definitely get into the Hall of Fame.
Head-Fi member flatmap, on the Head-Fi forum
Maybe I’m getting used to the Paramounts but I’ve never been this involved with the music from this system. These amps help to bring me closer to the music something other amps have not been able to achieve. For this, I’m very thankful to Dan, Paul and the rest of the Bottlehead team.
–johnsonad on the Bottlehead Forum
Paramounts!
Posted by patmcsween on July 31, 2009 at 15:56:44
Hello all,
Just finished the Paramounts, all I can say is WOW! They absolutely blow my old amp (PrimaLuna Prologue II) out of the water. Much more dynamic, FAST, more bass, much more on top and the mids are wonderful. The stage is wide and deep. I’m into the 4th hour and I can already hear an improvement. Modified with Mundorf silver oil caps in the stream, chose not to try and install the delay boards I got from Sophia at this time as this was only my 2nd build (FP III was 1st) and I was over my head already.
I would like to thank Doc, PJ, Eileen and everyone at Bottlehead for an outstanding job. The instructions were clear and accurate. Easy enough for an absolute novice to successfully complete with 1 unsoldered connection found during the resistance checks as the only mistake.
This stuff sounds REALLY good.