OT, ....New Capaciitor Type.............. for AUDIO Use....

[LowOhms]

"OT" in my "Title" usually stands for " Off Topic", but I want to suggest, in this case, it really means " ON Topic " !!

This is my first full disclosure on a public Forum of a new film capacitor type, that has profound and serious uses in audio, in my experience and in my OPINION.... both in speakers and amplifiers.

It is called a Gate-Turn-Off capacitor, and you can read datasheets from people like WIMA, who produce these. I have also seen RIFA " GTOs" and Arcotronics brand " GTOs", which has been merged into Kemet.

This is a long post and story, be forewarned.

In April 2016, I befriended a fellow in the Netherlands, an eBay capacitor seller, who, like me, built Single Ended triode amps, he did 300Bs, and I was doing Type 45s then. WE are both amateur enthusiasts.

My new friend John tells me about his favorite sounding cap, ......an ARCOTRONICS film cap, 5 uF value at 1200 VDC rated. Easily sensing this fellow was legitimate, I ordered some of these capacitors from him, and immediately incorporated them in a second-generation Type 45 SET direct-coupled amp I had designed and was building just THEN, for myself, for VOTTs..

I ordered many of these, and used two for the shared power supply. This stereo amp used a single L1/C1/L2/C2 B+ filter to the Finals stage. These 5 uF caps were added. as part of a multiple film bypass cap " bunch or bundle ", across C1 and C2, which usually are about 30 uf ( C1 ) and 50 uF ( C2 ) in value.

I was also FINALIZING my own DIY VOTT 800 HZ crossovers for my speakers, so I included this same type 5 uF Film Caps as part of each " C " position in a 12 dB / 800 hZ, Butterworth Filter. So, it was to employ two ARCOTRONICS GTOs, per crossover.

In May, 2016, when I fired-up the newly-built 45 amp ( and speakers with new crossovers ), for the first time, it all sounded very good to me. Nice and dynamic.

By about August, 2016, I go the nerve to disconnect the ground from ONE 5 uF Arcotronics Gate Turn Off cap, bypassing C1. Holly smokes.....the whole system died in Dynamics and sounded very ordinary. I quickly re-connected the C1 5 uF GTO bypass, and have listened that way, religiously, since then.

I didn't tell too many about this result. In December 2016, I had a USA friend, who I had shown photos to of my DIY VOTT crossovers, call to tell me " he figured out what the cap was, and where to get them ". Lawrence said he ordered some, and installed it in his system, and he was FLOORED. His specific description " It gets the LEADING EDGE of all transients, from the bass on up, UNLIKE anything we have ever heard any wheres in audio ". I truly LIKE his description, after living with these at that point .....for over half a year.

Lawrence gave me his own unsolicited and unexpected surprise confirmation. So, I re-read the literature on line, in the eBay ad, etc etc to find out more about this device., in December 2016. The spec given by the eBay seller was 1.3 milliohm ESR at 100 khZ, which is very good, and 64 Amps RMS, not too shabby.

By CHANCE, I notice WIMA made this same type of industrial cap, so I downloaded their datasheet on GTOs. Inside, I found out what I was likely responding to. These caps, besides being supremely low in ESR, ( as are some other caps ) it can ( UN - like other caps ) do INSTANTANEOUS PEAK currents, ( in my size : 5 uF at 1200 VDC ) - in the WIMA datasheet - of " about 1,500 AMPERES PEAK " !!!!!!!!!!!!!!!!!!!!!.

This instantaneous peak capability, I surmise, it what is now giving us " The leading edge of all musical transients, from the bass on up " as precisely described in November by my copy-cat nice friend Lawrence, who is a good listener.

In early 2017, I had urged my good personal friends, in audio, to acquire some of these caps for their own use, typically on ALTEC systems, so they are " covered ". The reports from users, are all very positive. In January, I had a St. Louis musician friend add them, in this order : first to his DIY 604 MLTL woofer crossover, then to his crossover's tweeter section, and finally to his amps.

This was the OPPOSITE of my practical experience in 4-2016, when the amps and speakers got the treatment ALL at one time. His report was very positive, each step. He has also has recently done his upstairs Valencias.

There is also a ALTEC User, a friend and Forum Member frorm Canada, that has had a similar experience in the last month, with his 604s and his VOTTS. . I asked these friends NOT to discuss this, until I decided to release the information to the audio people up here. Todd, today, thankfully has paved the way !!

The GTO 5 uF ARCOTRONICS eBay auction, most recent, is here for all to see:

5uF 1200V MKP Filter Caps GTO LOW ESR HQ arcotronics 2Pcs | eBay


These 5 uF at 1200 VDC film caps normally will sell in the $50.00 to $80.00 each range, so two for $16.95 is attractive. Kemet, who presently owns ARCOTRONICS, sells the same value part for over $50.00 but has a 50 part minimum.

Shipping from the Netherlands can be done in packages of up to five or up to thirteen pieces, advantageously. I am pretty sure John in the Netherlands has under 100 pieces left, and I would APPRECIATE IT if someone does NOT buy out all of his stock, so OTHERS can try this out, and we can " share " our results and experiences among more than just a few users. Many of the caps will be scratched and chipped from poor storage and handling. Not usually a factor .

In a separate post, IF any ( or enough ) folks are interested, I would be happy to cover what I have learned as far as how to most-effectively implement this part. The two mounting bolts I get from McMaster Carr, and they are BRASS, M-8s at 12 mm length, and a 1.25 pitch.

:-) No no, we do not use 26 AWG magnet wire ever, to connect these caps, .....for obvious reasons. I would be happy to assist any who have an interest.

In my humble opinion, and Old Guy, its ONLY " my " opinion, from listening for over a year, possibly the first in the USA to do so, this is the future !!


Thanks, too long a post !!


Jeff Medwin...... Low Ohms , Low ESR, High Current



PS, Here is a 6 uF VISHAY GTO, only an example, rated at 7,200 Amperes PEAK current :

http://www.vishay.com/docs/13094/gto4500.pdf