I have always wanted to make something really small I can bring to the office (and also use at home) and 0.5W - 1W is all I need.
I have been reserving my 12B4 for this but I was side tracked
and made a 12B4 preamp instead, which I really liked. Besides, I don't think that the 12B4 can be run without a driver.
I wanted the purest (sic) single triode amp (duh) that can be driven from a CD player.
From the tubes available with me, it seems that the 417A is capable of producing some watts with a 5W plate dissipation, so I was thinking of putting in a 5K load and drive it around 25-30mA. Bias it around 2V and I should be fine? Maybe?
Are there any triode candidates out there? Maybe I can beg friends if they have any that you may suggest
I have been reserving my 12B4 for this but I was side tracked
and made a 12B4 preamp instead, which I really liked. Besides, I don't think that the 12B4 can be run without a driver.I wanted the purest (sic) single triode amp (duh) that can be driven from a CD player.
From the tubes available with me, it seems that the 417A is capable of producing some watts with a 5W plate dissipation, so I was thinking of putting in a 5K load and drive it around 25-30mA. Bias it around 2V and I should be fine? Maybe?
Are there any triode candidates out there? Maybe I can beg friends if they have any that you may suggest
With ss power supply, this would be one tube:
http://www.sempermusica.com/
Search under "spud amps" for more examples of the genre.
Sheldon
http://www.sempermusica.com/
Search under "spud amps" for more examples of the genre.
Sheldon
arnoldc said:
I don't see any reason you couldn't sub in a cap for the transformer, or no cap. Note that I haven't looked up that transformer to see if he's getting any gain there. But here's one with the same tube and just a pot on the input:
http://digilander.libero.it/paeng/projects_frame.htm
Edit: Actually, no pot shown, but could be one. Should be no problem as long as the source has no DC.
Tube amp kit
Hi all,
I cheated and took the easy way out.
Got the amp kit from Antique Electronic Supply and it works. Each morning I get into the lab and turn it on. It runs a full 12 hour day, every day.
It gets coments and always brings a smile to visiting brass who come here.
I don't have the 'ears' any more to know good from great, but it keeps me happy and it was a snap to build.
Good luck on this project, perhpas I will order parts for one of these as well.
Later dude
Jack Crow
tdy
Camp Arifjan, Kuwait
Hi all,
I cheated and took the easy way out.
Got the amp kit from Antique Electronic Supply and it works. Each morning I get into the lab and turn it on. It runs a full 12 hour day, every day.
It gets coments and always brings a smile to visiting brass who come here.
I don't have the 'ears' any more to know good from great, but it keeps me happy and it was a snap to build.
Good luck on this project, perhpas I will order parts for one of these as well.
Later dude
Jack Crow
tdy
Camp Arifjan, Kuwait
Done!
The picture shows the amp in testing in the kitchen (yeah, I assembled it in the kitchen as my workbench has another unfinished project on it) with Kenwood car speakers.
This amp sounds great with the cheap Hammonds on it I like the tone so much! So this is how a real single triode amp sounds like It's so pure, I'm listening to Hayley Westenra's Pure album.
It's now driving my DIY Altec speakers.
I like it, I like it!
The picture shows the amp in testing in the kitchen (yeah, I assembled it in the kitchen as my workbench has another unfinished project on it) with Kenwood car speakers.
This amp sounds great with the cheap Hammonds on it
I like the tone so much! So this is how a real single triode amp sounds like It's so pure, I'm listening to Hayley Westenra's Pure album.It's now driving my DIY Altec speakers.
I like it, I like it!
An externally hosted image should be here but it was not working when we last tested it.
A single 5842 per channel will give you somewhere around 1W output, and can be incredibly simple. There is a very simple transformer coupled pre-amp circuit on my site that works well as a tiny power amplifier with the substitution of a 5K:8 ohm transformer like some of the ones that edcor sells.
Hi Kevin,
I can't simulate this thing with my SEAmp CAD. Right now I have 180V B+ and 82R on the cathode.
How do I get all the mighty 1W that the 417A/5842 can put out? I fell in love with the tone of the amp (the prototype in previous post) and I'd like to maximize power now
TIA
edit:
I checked your schema and it has 62R for cathode, and 150V B+. Is that it? I'll lower my Rk now.
I can't simulate this thing with my SEAmp CAD. Right now I have 180V B+ and 82R on the cathode.
How do I get all the mighty 1W that the 417A/5842 can put out? I fell in love with the tone of the amp (the prototype in previous post) and I'd like to maximize power now
TIA
edit:
I checked your schema and it has 62R for cathode, and 150V B+. Is that it? I'll lower my Rk now.
It also depends on the primary impedance of your output transformer and any electrical/magnetic losses in the transformer.
With a vs of 180V I would probably recommend a cathode resistor of around 75 ohms, just watch out for dissipation in the real world.
I will do a simulation and see what I come up with..
Kevin
With a vs of 180V I would probably recommend a cathode resistor of around 75 ohms, just watch out for dissipation in the real world.
I will do a simulation and see what I come up with..
Kevin
Hi Kevin, I'd appreciate that. This little baby sounds so good I want to give it a Tamura F-475 But right now, I'm using a Hammond 125ESE.
I want a really small, but good performing output transformer so that I can put it in this chassis I've been saving for a nice project.
ps.
Will a cathode CCS from an LM317 similar to the 12B4 linestage thread work?
Or maybe a bunch of RED LEDs? Sy? Where's Sy?
But right now, I'm using a Hammond 125ESE.I want a really small, but good performing output transformer so that I can put it in this chassis I've been saving for a nice project.
An externally hosted image should be here but it was not working when we last tested it.
ps.
Will a cathode CCS from an LM317 similar to the 12B4 linestage thread work?
Or maybe a bunch of RED LEDs? Sy? Where's Sy?
Hi Arnold,
Based on simulations, it looks like anything over 0.5W is unreasonable to expect despite claims of 1W made by several people I know who have actually built spud amplifiers based on the 5842/417A. (I build white cathode followers with them for headphone amplifier use - they work quite well..)
My simulations with 3.5K/5K transformers and 200V plate supply with 120 ohm cathode resistor indicate about 350mW/250mW respectively at something less than 5% thd, with 2nd harmonic being predominant.
Since these are somewhat expensive tubes I don't recommend exceeding the rated plate voltage of 200V, current of 38mA or the plate dissipation rating of 4.5W..
It seems to me that this amplifier would be useful for driving headphones or really high efficiency speakers in a small room.
Edcor makes some nice open frame type transformers that ought to perform well in this application..
See this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=72654&perpage=10&pagenumber=1
Based on simulations, it looks like anything over 0.5W is unreasonable to expect despite claims of 1W made by several people I know who have actually built spud amplifiers based on the 5842/417A. (I build white cathode followers with them for headphone amplifier use - they work quite well..)
My simulations with 3.5K/5K transformers and 200V plate supply with 120 ohm cathode resistor indicate about 350mW/250mW respectively at something less than 5% thd, with 2nd harmonic being predominant.
Since these are somewhat expensive tubes I don't recommend exceeding the rated plate voltage of 200V, current of 38mA or the plate dissipation rating of 4.5W..
It seems to me that this amplifier would be useful for driving headphones or really high efficiency speakers in a small room.
Edcor makes some nice open frame type transformers that ought to perform well in this application..
See this thread: http://www.diyaudio.com/forums/showthread.php?s=&threadid=72654&perpage=10&pagenumber=1
shoog, i've seen a couple of them 6BM8 designs on the net but I never have the kick to make them due to a) pentode output (yes, can be triode strapped), b) two stage
jack, no problem with that, if that's what works for you
kevin, alright now, i'll back down to the textbook operating condition of 150Vp and 20mA. Thanks! Right now I can't complain, I've been listening since this morning using my DIY Altec and I really like it. I have a small 4m x 4m room (yuk! square)
OT: i have a Simpson 265 volt-ohm-milliameter with Simpson 260 audio power meter attachment. Anybody knows how to use this?
jack, no problem with that, if that's what works for you
kevin, alright now, i'll back down to the textbook operating condition of 150Vp and 20mA. Thanks! Right now I can't complain, I've been listening since this morning using my DIY Altec and I really like it. I have a small 4m x 4m room (yuk! square)
OT: i have a Simpson 265 volt-ohm-milliameter with Simpson 260 audio power meter attachment. Anybody knows how to use this?
Consider the ECL82 in UL - a good compromise.
I would be cautious about using LEDS in the cathode. In a driver they run to lean and tend to sound a bit grainy. SY was toying with the idea of supplementing their current with a seperate supply to reduce this effect. They might work better in the cathode of a low current output valve, though exceeding there current rating might be an issue, you could try running them in parallel.
Shoog
I would be cautious about using LEDS in the cathode. In a driver they run to lean and tend to sound a bit grainy. SY was toying with the idea of supplementing their current with a seperate supply to reduce this effect. They might work better in the cathode of a low current output valve, though exceeding there current rating might be an issue, you could try running them in parallel.
Shoog
Hi Arnold,
I ran another simulation this morning with a higher primary impedance of 7.6K.. The cathode resistor was 120 ohms bypassed by 470uF and the plate voltage was 200V.
The simulation results were quite interesting, 330mW output at 1% thd (2nd @ -40dB, 3rd @ -62dB rel to 1kHz output) I am not sure how good the tube model is that I am using for the 5842/417A, but this seems reasonable as an estimate. Out of curiosity what output transformer as you using? (Impedance, inductance, etc.)
The Edcor XSE-25-8-7.6K seems like a good match and is quite inexpensive even with shipping..
I ran another simulation this morning with a higher primary impedance of 7.6K.. The cathode resistor was 120 ohms bypassed by 470uF and the plate voltage was 200V.
The simulation results were quite interesting, 330mW output at 1% thd (2nd @ -40dB, 3rd @ -62dB rel to 1kHz output) I am not sure how good the tube model is that I am using for the 5842/417A, but this seems reasonable as an estimate. Out of curiosity what output transformer as you using? (Impedance, inductance, etc.)
The Edcor XSE-25-8-7.6K seems like a good match and is quite inexpensive even with shipping..
Hi Kevin,
Right now I'm using a Hammond 125ESE 5K primary tap, 8 ohm output on the amp. Here's some data I found on the Hammond site-
125ESE Inductance (Minimum) 9.58 H DC Resistance (+/- 20%) 90.6 Ohms
Your simulation looks interesting and since I'm going to have my output transformer custom made (I want a 32 ohm tap for my Senn), I'm ok with any primary.
Right now I'm using a Hammond 125ESE 5K primary tap, 8 ohm output on the amp. Here's some data I found on the Hammond site-
125ESE Inductance (Minimum) 9.58 H DC Resistance (+/- 20%) 90.6 Ohms
Your simulation looks interesting and since I'm going to have my output transformer custom made (I want a 32 ohm tap for my Senn), I'm ok with any primary.
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