Why no tiny output transformers?
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 25th October 2017, 06:15 PM #11 GoatGuy   diyAudio Member     Join Date: Dec 2012 Location: SF Bay Area http://www.visaton.de/pdfexport/de/s.../pdf/tr84.html Now that's an interesting lil' transformer. Especially suited for wide swing high voltage high impedance SE, I think. Might work. Claims to be 20-20,000 Hz. __________________ John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink
 25th October 2017, 06:58 PM #12 6A3sUMMER   diyAudio Member   Join Date: Jun 2016 Just a little math: (I squared/R)/2 = rms power 20A Squared into 2 Ohms = 200W rms Gaussian response, K = 0.35 (good phase response, and smooth frequency response). K/risetime = 3 dB bandwidth 0.35/3 us = 116.667 kHz 20A * 2 Ohms = 40V 100V/us slew rate 40V/100V = 0.4 0.4 us is much faster than 3us rise time. Is the Golden Rule's math broken? My Vinyl and CDs do not have that fast of a rise time, and not that kind of bandwidth. The microphones used on those recordings do not have that rise time or bandwidth either. My speakers are not rated for 200 Watts, or even 100 Watts, and they would give me ear damage. I can not hear to 100 kHz, and my speakers will not reproduce that. What speakers and what recordings do I need?
 25th October 2017, 08:13 PM #13 GoatGuy   diyAudio Member     Join Date: Dec 2012 Location: SF Bay Area Love it! The first person to actually do some math on my by-line. BRAVO, Summer. Key words worth remembering dynamic load, slew rate, mean output. , bandwidth and min current sourcing. At the upper end of output, 100 V/μs will achieve the 100 kHz bandwidth at 100 kHz. However if we remember d A⋅sin(ωt) / dt = ωA⋅cos( ωt ) (which is to say, the differentiation which computes slew-rate of a sinusoidal signal with ω frequency (in radians/sec, weird, but useful) has a maximum slew of ωA (A is amplitude). So if nominally, ω = 2π⋅20,000 Hz = 126,000 radian/s, and A is 50 VPEAK envelope volts, then that's only 6.3 V/μs slew rate. For that implied RMS power (50 × .707)² ÷ 8 Ω … = 150 RMS watts, well … perhaps 100 V/μs is overkill. I kind of think it is. Yet I read it on John Curl's blog somewhere. If like purists, we pride ourselves of getting full output at 30 kHz, or 50 kHz … or even 100 kHz (for no particularly audible reason), and having 70 volt output rails then (A = 70) x ( ω = ( 100,000 × 2 × π ) ) = 44 V/μs Pretty close to the 100 V/μs proposition. Such a dragon of an amplifier should easily be able to drive (70 × .707)² ÷ 4 Ω = 600 RMS watts into a nominal 4 Ω load. Since I²R = P then … I = √( 2 P / R ) = √( 1200 ÷ 2 Ω ) = 24 amps. See? that one works. I think Curl's recommendation summary just sizes up current audiophile thinking in a nutshell. Expect to 'turn it up' to nearly max-output from time to time; expect 100 or more "program RMS watts" from that. Expect transients up to 20 amps; expect real-world speakers to have impedance dips down to 2 Ω at crossover. Expect to actually hear something audible by having bandwidth above 20,000 Hz. Its like when I listen to Bolero, or the 1812 Overture. The dynamic range of a good 24 bit recording at 96 kHz sample rate … relatively "uncompressed" is remarkable. And its a curious thing: played "at 10", even in the loudest crashes and crescendos, somehow the music doesn't seem significantly louder than you'd encounter sitting in a prime seat in the concert hall. I guess that's the holy grail of audiophile quests. GoatGuy __________________ John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink Last edited by GoatGuy; 25th October 2017 at 08:39 PM.
 25th October 2017, 08:29 PM #14 GoatGuy   diyAudio Member     Join Date: Dec 2012 Location: SF Bay Area PS: your vinyl and CDs of course don't themselves have that kind of rise-time. But per the calculations above, amplified, they just might. Saying (in context) that one has a nominally wonderful 24 bit recording of some uncompressed orchestral piece, and that the output of one's DV D/A codec is 1 volt peak, and it has 96 kHz sampling sporting 44+ kHz bandwidth… (A = 1 volt) • ( 2π 44,000 ) = 0.28 V/μsec AS you say. Now, let's amplify that to 100 volt audiophile (\$5,000 to \$50,000 amp) levels: (A = 100 V) • ( 2π 44,000 ) = 28 V/μsec Ah, getting closer to the 100 V/μsec. If one loses their physics/mathematics sanguine mind, and assumes that meaningful audio exists up to 100 kHz, then you get right up to 63 V/μsec. amplified of course. From a 1 volt (envelope) source. GoatGuy __________________ John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink
 25th October 2017, 08:32 PM #15 smoking-amp   diyAudio Member     Join Date: Dec 2001 Location: Hickory, NC PA system line matching xfmrs don't have an air gap to handle SE DC current. For small SE OTs: EDCOR - XSE Series Output Transformers EDCOR - GXSE Series Output Transformers
 25th October 2017, 08:44 PM #16 stocktrader200   diyAudio Member   Join Date: Jan 2008 Location: Calgary those specs are so that the 20 - 20khz frequencies are low distortion and no phase shift in the amplifier. I want my amps capable of 300 - 400khz as this will yield greater stability in the audio band via a greater gain phase margin.
 25th October 2017, 08:50 PM #17 smoking-amp   diyAudio Member     Join Date: Dec 2001 Location: Hickory, NC Planet Zorkan might have those. Ferrite cores.
GoatGuy
diyAudio Member

Join Date: Dec 2012
Location: SF Bay Area
Quote:
 Originally Posted by stocktrader₂₀₀ those specs are so that the 20 - 20khz frequencies are low distortion and no phase shift in the amplifier. I want my amps capable of 300 - 400khz as this will yield greater stability in the audio band via a greater gain phase margin.
Seriously? Wow. Well, there you are then.

I however am VERY happy if the first poles are at 15 Hz and 15 kHz. You know, the natural ones that (at the low end) protect the amplifier and speakers from mechanically coupled rumble or substantial subsonic wow, and at the top end start to neck off HF response gracefully to again protect tweeters and tho' not heard, according to US diplomats in Cuba … the ears. Supersonics at high power can still be a hearing killer.

Why say First poles? because in the argot of digital and analog signal processing, one's signal path inevitably has 'poles' in the S-plane around which in the frequency plane response goes from flat (or "nominal") to non-flat. A high pole is both a phase-shifter and a 'peaky' response. (Goes up toward pole, down like a Butterworth on the attenuation side.) Lower poles can be designed to not do that., just gradually rolling off (either low-pass, low-cut, high-pass or high-cut). Stack several conceptual filter/pole sections in series, and you do not necessarily turn a trio of soft-drop low-pass filters into a peaky filter. It just drops off faster. But you do add the phase delay such a HighCut filter section incurs.

Perhaps I'm explaining overly much. I apologize. Its just that I spent several years in university and trade-practice engineering of digital/analog active second and third order response network design to not know such stuff. Without my 40 year old books! LOL. Peace! (I lived when Berkeley's residents were still swatting pterodactyls like flies and tie-dyeing t-shirts in galvanized washtubs with contraband chemistry-lab dyes made by grad students with the hobby. That IS a ways back. You need REALLY big flyswatters for pterodactyls.)

GoatGuy
__________________
John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink

diyAudio Member

Join Date: Nov 2004
Location: Maryland
Quote:
 Originally Posted by BJosephs I'm wrapping up my 5W EL84 amp for listening and was thinking about building a little <1W triode se project for my desk at work. I want to keep the build small. For the first time in my life I find myself looking for a tiny output transformer and I'm noticing that there just aren't many below 5W. Is there a physical limitation that makes smaller transformers less ideal? Or maybe I'm looking in the wrong places?
I may have drawer full of tiny output transformers...anywhere between half a watt to one watt. Are you interested?

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Holton Precision Audio         CSS         Dx Classic Amplifiers         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post PB2 Instruments and Amps 17 30th April 2015 07:36 AM hatrack71 Swap Meet 4 5th April 2012 07:43 PM hilbert_mostert Tubes / Valves 12 8th March 2009 05:10 PM mjk130 Parts 3 30th January 2009 10:44 AM THOR Multi-Way 18 28th June 2004 06:42 AM

 New To Site? Need Help?

All times are GMT. The time now is 03:56 PM.