Most data sheets for RF tubes I've seen derate against frequency (eg 6146 - 90W ICAS at 60MHz, 60W ICAS at 175MHz.
Would this apply to Video tubes which are operated at audio frequencies? Or am I just seeing a conservative rating?
I think I'll try a multitap 8K p-p transformer just to see if switching to the 16 ohm tap on an 8 ohm load gives me much more power with better plate load matching.
Would this apply to Video tubes which are operated at audio frequencies? Or am I just seeing a conservative rating?
I think I'll try a multitap 8K p-p transformer just to see if switching to the 16 ohm tap on an 8 ohm load gives me much more power with better plate load matching.
I did build a 6SL7/6SN7 SE guitar amp. Good sound but not enough power.
Someone with a 100dB/1m speaker would have been happy and satisfied. I wasn't. Mine is 96dB. Little by little I've realized I'm no teenager and I can play as loud as I want to. Sooooo who wants a puny 1 watter?
Ok, I've covered now the 'not really loud area' and I'm not interested. Of course I could spend the money on a very sensitive speaker. Celestion Vintage 30 is pretty good. 1W amp with that speaker will be enough for some fun. LOUD.
After all these years the Champ is still the low wattage amp to copy anyway. No designer has beaten it, I see clones with el84's but almost same circuit. So if Wavebourn can make those Russian tubes sing, he's got many chances of winning. IMO.
I agree, those mini tubes have potential.
Reminds me,
Take a peek at The ZVEX Nano Amp.
ZVEX AMPS
http://zvexamps.com/ampsound.html
http://media1.zvex.com/nano.mov
Yeah, pretty cool. A 12V wallwart and a boost converter.
An externally hosted image should be here but it was not working when we last tested it.
Another good idea for a cheap power supply: voltage multipliers.
AVA100 Power Supply
Edit: forgot the rules...you have to buy all the parts. Too many caps to be a cheap alternative.
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No problem here. The RF derating VS frequency comes from the fact that tubes and just about everything else lose efficiency as the frequency increases. So since the losses in the tube go up with frequency you need to back off the power at higher RF frequencies. This is not an issue at audio frequencies.
No "supposed to" about it: they definitely have a negative resistance characteristic, which is why you can silence a Zener by connecting a big capacitor in parallel with it, but you can't do that when using any sort of glow tube as a regulator.
As for arcs, sparks, glow discharges (all the same phenomenon anyway) and RF: Poulsen Arc Oscillators
Depending on the original application, the ratings for VTs can be very conservative. You can usually bust most hollow state specs much more successfully than for solid state, and some by wide margins indeed. Hollow state specs are more like suggestions.
Something rated for "brick on the key" (e.g. FM) service with a Pd= 4W will probably not be real unhappy running higher dissipations in service that has a much less demanding duty cycle (AM, SSB, or amplifying music).
"... gas regulator tubes are supposed to have negative resistance too."
"No "supposed to" about it: they definitely have a negative resistance characteristic, which is why you can silence a Zener by connecting a big capacitor in parallel with it, but you can't do that when using any sort of glow tube as a regulator."
"They required a piece of RF magic known as a circulator. Ferrite, magnets, and resonance all combine to create a device that has 3 ports aranged in a circle. It works like the RF version of a traffic circle, the RF only flows one direction. Now add a negative resistance device to one port and you will have gain across the othar two ports. The circulator keeps the output energy from flowing back to the input, or you will have a tunnel diode oscillator."
There is a LF equivalent of the RF circulator called a directional hybrid splitter/combiner which was used in telephones to split the two directional line traffic down to send and receive (mic and earphone). I think it uses two CT'd inductors in a bridge. However, the thought of having to use two inductors per gain stage is a show stopper here. And then there is the low efficiency and linearity issues of neg. resistance amplifiers. But, if one were already using say a mercury street lamp or florescent lamps for illumination, the amplifier gain could be a near freebie. Could be a certain coolness factor to a pyramind of florescent lights also providing the speaker power. Might be a noise issue with mercury lamps though. I used to work in a restricted facility and one of the florescent ceiling lamps in one lab was found to be radiating a restricted RF signal, it got confiscated and locked away.
"No "supposed to" about it: they definitely have a negative resistance characteristic, which is why you can silence a Zener by connecting a big capacitor in parallel with it, but you can't do that when using any sort of glow tube as a regulator."
"They required a piece of RF magic known as a circulator. Ferrite, magnets, and resonance all combine to create a device that has 3 ports aranged in a circle. It works like the RF version of a traffic circle, the RF only flows one direction. Now add a negative resistance device to one port and you will have gain across the othar two ports. The circulator keeps the output energy from flowing back to the input, or you will have a tunnel diode oscillator."
There is a LF equivalent of the RF circulator called a directional hybrid splitter/combiner which was used in telephones to split the two directional line traffic down to send and receive (mic and earphone). I think it uses two CT'd inductors in a bridge. However, the thought of having to use two inductors per gain stage is a show stopper here. And then there is the low efficiency and linearity issues of neg. resistance amplifiers. But, if one were already using say a mercury street lamp or florescent lamps for illumination, the amplifier gain could be a near freebie. Could be a certain coolness factor to a pyramind of florescent lights also providing the speaker power. Might be a noise issue with mercury lamps though. I used to work in a restricted facility and one of the florescent ceiling lamps in one lab was found to be radiating a restricted RF signal, it got confiscated and locked away.
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Remember the Rockman. It was a belt worn guitar amp. it sold well because the inventor and chief marketeer was named Tom Scholz. He worked full time for Polaroid and played in a little rock band called Boston, who sold several million records.
The Rockman was a small amp that used headphones, but it could drive a small speaker or be used as an effects preamp for a big amp. It sounded pretty good, but the cheap slide switches and plastic case could not handle serious rock and roll. It faded into memory about the same time that Boston did.
Another one that did sell pretty well was the Smokey amp. I think it was a 1W amp.
An externally hosted image should be here but it was not working when we last tested it.
I loved my Rockman, it had still one of the best chorus effects I have ever heard.
They actually still turn up on ebay regularly, I sold one of mine there for 120 bucks a few years ago, like new in box.
Those Zvex amps actually do well especially for recording, I have played one plugged into a Marshall 4 X 12 cab and it really had a good bit of thump on the bottom end.
Thing is, stick a mic in front of it, and its good to go for lots of uses.
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I just played through a $99 Kustom Defender 5W head that uses an EL84. Sounds a lot like the 2 stage volume-only amp I just built...
Kustom Defender 5H Guitar Amplifier Head
Kustom Defender 5H Guitar Amplifier Head
The Flathead transformer was a bust. I got 4.8Vrms into 8 ohms in PP at 1KHz, but the frequency response is abysmal. -3dB points are 100Hz and 2KHz compared to an Edcor GPP10-8-10K in the same circuit going from 80-18KHz.
This is a guitar amp circuit with tone stack and frequency shaping, so I'm surprised the Edcor went to 18K.
I also need to check an Edcor GXSE10-8-5K SE transformer to finish testing.
Two line transformers I tried were respectable with 80-4.5KHz response.
The Champ clone transformer (P-TF22905) only went from 180Hz to 3.5KHz. I need to try an output tube with lower plate resistance to be sure this is true. If it is I don't care about cloning a Champ.
The P-T31 did well with a response of 80Hz to 8KHz.
This is a guitar amp circuit with tone stack and frequency shaping, so I'm surprised the Edcor went to 18K.
I also need to check an Edcor GXSE10-8-5K SE transformer to finish testing.
Two line transformers I tried were respectable with 80-4.5KHz response.
The Champ clone transformer (P-TF22905) only went from 180Hz to 3.5KHz. I need to try an output tube with lower plate resistance to be sure this is true. If it is I don't care about cloning a Champ.
The P-T31 did well with a response of 80Hz to 8KHz.
Hard to tell if its china without opening it up but Kustom is based out of Kentucky.
Hanser Music Group
BTW, that price is $99.00 SHIPPED ground!
Manuel 5H
I wonder what I could mod for $1.00 to improve it
Hard to tell if its china without opening it up but Kustom is based out of Kentucky.
Hanser Music Group
BTW, that price is $99.00 SHIPPED ground!
Manuel 5H
I wonder what I could mod for $1.00 to improve it
Could you do a re-branding for a buck? A little bit of paint...
From the rear panel photo in the user manual on their web site:
Designed in USA Made in China
Kustom Amps appeared in the 60's making solid state amps. They were based out of Chanute Kansas. They dissapeared sometime in the 80's. I got a dead Kustom PA head in the 70's for cheap. I fixed it and used it for keyboards until I sold it some time in the 80's when I sold all my keyboards. It had a neat shiny silver roll and pleated naugahyde cabinet. I never saw a Kustom tube amp.
Kustom Signals made police radar equipment in Chanute Kansas. The MR-7 was the first radar unit capable of operation from a moving police car. It was housed in a neat little roll and pleated cabinet like a tiny Kustom guitar amp. A friend who repaired police equipment brought one here for us to play with one night in the early 70's. Kustom Signals is still in business and their manufacturing plant is still in Chanute Kansas.
The new Kustom Amps is based in Hebron Kentucky. I have no idea how it is related to the old Kustom, but the logo is the same.
There are some clips of the little Defender 5 playing on Youtube. It doesn't sound bad.
One of the music stores I do repairs for has one paired up with the Kustom $99 single 12" cabinet.
Basically, it responds like a Champ. Despite the promo most of the crunch seems to come from driving the 1st stage with a hot signal until you get really loud, but it's a nice smooth breakup. I.e most of the influence on tone is using the guitar knobs.
When I get my cabinet with the Jensen built I'm going to take it in and compare voicing.
My BOM is $500 for total of head and single 12 cab. Even without the fancy caps and the extra iron, the head alone is $262. A $100 BOM for a head only would have to be very creative in areas like the power transformer and chassis metal, have a hardwired AC cord, etc.
What do you suppose the factory BOM on the Kustom amp is?
Basically, it responds like a Champ. Despite the promo most of the crunch seems to come from driving the 1st stage with a hot signal until you get really loud, but it's a nice smooth breakup. I.e most of the influence on tone is using the guitar knobs.
When I get my cabinet with the Jensen built I'm going to take it in and compare voicing.
My BOM is $500 for total of head and single 12 cab. Even without the fancy caps and the extra iron, the head alone is $262. A $100 BOM for a head only would have to be very creative in areas like the power transformer and chassis metal, have a hardwired AC cord, etc.
What do you suppose the factory BOM on the Kustom amp is?