Spring's Coming! Time for the Next B.A.S.S. Meetup! (Connecticut)

[basspig]

It's coming up on that time again. What time, you ask? Time for the Third Annual Basspig Audiophile Society Social!

The way events are going, I'm likely to settle on April 5, a Saturday, for the meet. Our usual starting time of 2PM is planned.

Dinner and a buffet will be served upstairs, as usual.

The main attraction this year (assuming I can complete it in time!) will be my OTL vacuum tube amplifier. This dual mono amplifier, with separate power supply chassis, is being designed to a conservative 125 WPC rating and uses a dozen large beam tetrodes. The power supply is 1000VA for the high voltage and 40 amperes for the filaments. A veritable contender and should be interesting when the unveiling occurs.

As usual, there will be demonstrations of the world-famous Bass Pig sound system, and probably a shop discussion with demonstration at the shop of Amplifier Experts.

R.S.V.P. to basspig (the "at" symbol) basspig ( dot ) com for address/directions, etc.

The past two years have been great as far as turnout, with attendees from as far as 5 hours driving distance.

I hope to see some of you at this year's meet!

 

[basspig]

It's turning out that this OTL vacuum tube amplifier project demands much larger and more expensive components to make it work satisfactorily.


The initial startup of the system with Totem Pole topology revealed that the power supply capacitance is way under the needed amount for sufficient performance. A change to Wiggins-Circlotron topology may help with this, but it requires that both the power supplies float. Which means I need yet another transformer to furnish the fixed supply for the driver stages.


My research indicates that the minimum supply capacitor size should be 7500uF. Currently, I have 1200uF in series (400 volts total) which means the effective capacitance is only 600uF per rail. There is 10 volts of ripple.


The other problem is these 500VA industrial control transformers only furnish less than 2 amps at 220 VAC per secondary winding. The total draw of the output tubes of one channel wants to exceed 8 amps.


I found some suitable capacitors, 7500uF at 400 volts, but they are 3.5" diameter and 6" tall and won't fit on my existing chassis. I need four of them. And here's the real catch: Mouser Electronics has them, for the princely sum of $400 a piece! Frankly, there is no way I'm going to invest $1600 in capacitors to build an OTL amplifier.


In order to do this right, I would have to scrap the chassis completely and start anew with a much larger chassis, even bigger power transformers and huge filter caps. That's just not possible for me to accomplish in less than two weeks that remain before the next B.A.S.S. meetup, which is tentatively set for April 5.


At this point, I'm wondering if I should even go ahead with the annual meeting this year, since I don't have anything new to demonstrate. We would be relegated to just showing off the Bass Pig's sound system, playing records and maybe a few shop demos, like last year and the year before. I'm not sure that such a presentation would be worth doing. Any opinions?

 

[basspig]

EVENT CANCELLATION NOTICE:
The 3rd Annual B.A.S.S. Meeting, tentatively scheduled for Saturday, April 5th, 2014 at 2PM is cancelled.
It was a difficult decision to make, but I felt that, without having the OTL amplifier project ready to show, there would not be much content of high value to show. I don't want these meetings to be just sessions where people spin records--I wanted to add some science and demonstrate unique amplifier designs. The technical hurdles to accomplishing this will require me to invest far more cash into the project than I had anticipated. Therefore, it's been postponed another year.

 

[sawzalot]

EVENT CANCELLATION NOTICE:
The 3rd Annual B.A.S.S. Meeting, tentatively scheduled for Saturday, April 5th, 2014 at 2PM is cancelled.
It was a difficult decision to make, but I felt that, without having the OTL amplifier project ready to show, there would not be much content of high value to show. I don't want these meetings to be just sessions where people spin records--I wanted to add some science and demonstrate unique amplifier designs. The technical hurdles to accomplishing this will require me to invest far more cash into the project than I had anticipated. Therefore, it's been postponed another year.

Although I did not attend I will honestly say that I appreciate your valiant efforts to host and entertain any willing audiophiles and bassheads. I think it sounds awesome and wish you continued success with your next GTG, maybe an early summer meeting can happen instead so get to work on that project

 

[basspig]

If I do reschedule, it will be either next spring, or in the late fall, around November. Once it gets above 50° outside, I have to run a/c to get rid of the equipment heat and the a/c is noisy. The alternative is suffering in 85° heat while it's 60° outside. Early spring is best because the weather is dry and if I keep the windows open, it removes just enough heat to maintain 70°F in the studio with the equipment running. Racks of multi-kilowatt amplifiers and a large venue projector throw out a LOT of heat. And summer is my house renovation season, so I'll be working from dawn to dusk on major renovation. Winter is less busy. Hopefully you can attend the next meet. I'll be sure to announce it here when I resume. This year was just too much with the amp repair shop work, tax filing and rushing that OTL to completion only to run into issues with the capacitance in the power supply and too weak power transformers. A new transformer, for each channel, wounder by Butler to my specifications, about a grand. Capacitors, $400 each x four. About $3600 in additional parts costs I had not anticipated.

 

[sawzalot]

Thanks for the response and heads up regarding another attempt at a GTG , I would surely consider attending as it sounds like a great time, sawz.

 

[basspig]

Thanks for the feedback. You would be in good company, too. We have had regular attendance from west PA area audiophiles in the past two meets.

 

[basspig]

Wow.. it's been four years since the cancellation. I have decided that I will have to have the next one in the spring of 2019, by hook or by crook. No, the OTL amp isn't finished, but there is quite a bit of other stuff that's new.
If I get a move on, and put aside some time and a nice sum of money for custom power transformers for the OTL project, maybe I can finish it this winter. Then we'll have a triple play event with lots of stuff to demonstrate.