Hunoz, I think the challenge for most people in this thread is to take some $1 RF/TV tubes and torture them into sounding like some classic amp they played on.
It has inspired me to try but i have to confess that the thing has beaten me 5-0 and right now it´s sounding like something the cat dragged in.
But to me the journey is far more interesting than the non existing chance to beat the more skilled people in this contest.
It has inspired me to try but i have to confess that the thing has beaten me 5-0 and right now it´s sounding like something the cat dragged in.
But to me the journey is far more interesting than the non existing chance to beat the more skilled people in this contest.
Generally speaking, while not up to the standards of days gone by, it does allow me to try out circuits rather quickly. The loose wiring is to allow me the option of changing circuits and positions on my breadboard, if I want to add a stage I have the wire length to do it. one switch and two pots are not being used so the wires are bent out of the way from the live circuit. It would be nice to have shorter lead length on the parts in the board but since I do not have an unlimited supply of parts I do not clip the leads unless they actually go into a finished circuit.
The temporary conections such as to the output transformer are just that, temporary. Three transformers in the picture, one output, one for the heaters, one for the high voltage. I would assume they are isolated enough from ground even though I have not hipoted them. The messy parts laying around, mainly parts that I swap in and out to judge the effect on the circuit. It would be best to have a spot for them and to mark down the change that they cause, when I get time to build a proper workbench that may happen.
So for all you newbies, do play safe. I do not go changing parts on a live circuit and I always check to see if there is any voltage stored in the circuit before I do any changes. I have loose wires running out from the key points I want to measure that I clip onto rather than sticking my scope or voltage probe into the parts on my breadboard. With the long lead length of the parts in the breadboard it is too easy to accidentally nudge one over and touch another part of the circuit. Mind you, while the photo does not show it well, I do allow enough physical separation between parts and wires to limit the dangers and the interaction of the circuit.
No offense, I'm too touchie this morning.
That said, I have never seen anyone here advocate building the old 'death-trap' amps with direct line strings of heaters and un-isolated B+.
Every time someone comes here with such a schematic there are several posts advising NOT building such circuits. People wishing to use old radios with such circuits are advised to purchase an isolation transformer to provide the necessary safety with such circuits.
Regretably, pushing isolation below bench out of the way leaves it out of sight giving the impression of a less safe environment.
I picked up an old 'American 5' radio, thinking of using it for this build. I did modify it a bit and I am sure it will go through another change or two. Propped up a 8" speaker in position, might loose two of the knobs for switches though. Here is the parts of the radio I am keeping.
Nah, then it's roots as a tabletop radio would all but disappear. I already cut the wood strip that held the knobs and tuning scale and repositioned it to the right side. I have a sort of vintage looking grill material for it, including some artificial 'weathering'. It would be easier if I were to go open back, since I want a sealed speaker I will have to be a little creative with the chassis.
I have been following this post with great interest. I think one point which may escape some people is that everyone wins from this thread. Its true that different styles of playing benefit from different styles of amps. That is exactly what you will have here. Regardless of the "winner", there will be many amps with many sound clips to choose from. How great is that? Build the amp that suits your style! Variety IS the spice of life!
Right!
But it is hard to choose.
Toying yesterday with super-dirty overdrive of a single ended output I decided to "improve" it in this particular regard. Additions included EQ in preamp to attenuate fundamentals of mostly low frequency strings, and to add an overdrive tone control. Here is the schematic attached. It sounds less nasty when overdriven, but did I loose some bottom end on clean sound, as the result? I don't know yet, because instead of a speaker box I use a small baffle with 12" driver from GE console.
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You pretty much end up with a thinner clean sound if you EQ it for overdrive. Just the nature of the beast. Now if you had a dual pot and you reduced the bass as you increased the gain... ... not suggesting anything, just saying.
I was thinking about it, but I don't have a dual pot with different values of gangs. What I come with, you see on schematic: connecting the gain pot to the same point where feedback capacitor goes I made depth of boost of highs dependent on volume control. I will put the result on youtube.
Let me say it again rather than responding individually: I was not talking about any amps or projects built would be unsafe or that such a thing would be advocated here. My concern was relating to working on projects that are on untidy benches with loose wiring and tools cluttering the work area and the safety implications of such practice.
I was taught to work on clean and tidy bench with safety isolation transformer on top of the bench and using it. When I was taught, we had to work with one hand in our pocket. After many years of working on amps, my practice of fully tidying up my bench and/or putting one hand in my pocket lapses and sooner or later I will end up having a minor accident. I have blown test equipment, got shocked by accidentally shorting something I did not intend to and also by forgetting to discharge ALL the caps. Given time not having any mishaps, we all get more comfortable then we should be. After all we are all human and we think this kind of thing will not happen to me.
The older I get the more and more I make sure I do not start work at my bench if I am rushed to go out in an hour and there is a chance I may need the whole hour to finish what I started. Equally it is not a good idea to start working if I had a blow with my wife. Frustration is not a good friend at the bench! At least not a good friend for me. I am not advocating that any of you should follow the above, but if you had any mishaps in the past, recognise any of the situations I referred here then you may want to think about my concerns.
I was taught to work on clean and tidy bench with safety isolation transformer on top of the bench and using it. When I was taught, we had to work with one hand in our pocket. After many years of working on amps, my practice of fully tidying up my bench and/or putting one hand in my pocket lapses and sooner or later I will end up having a minor accident. I have blown test equipment, got shocked by accidentally shorting something I did not intend to and also by forgetting to discharge ALL the caps. Given time not having any mishaps, we all get more comfortable then we should be. After all we are all human and we think this kind of thing will not happen to me.
The older I get the more and more I make sure I do not start work at my bench if I am rushed to go out in an hour and there is a chance I may need the whole hour to finish what I started. Equally it is not a good idea to start working if I had a blow with my wife. Frustration is not a good friend at the bench! At least not a good friend for me. I am not advocating that any of you should follow the above, but if you had any mishaps in the past, recognise any of the situations I referred here then you may want to think about my concerns.
I am all for the challenge and especially all for it, if the amp will use some tubes that have not been used for audio before. I grew up with using TV tubes for all sorts of things because parts were difficult to get and were super expensive to buy. However, lots of old TVs, radios, transmitters were available to strip down and we reused anything that we could. It is a great way to learn. Test equipment was a rarity and if the club had one we had to queue to use it. Its use was always supervised by someone senior so that it would remain working.
Yes, high voltages in tube amps are dangerous. Once during rehearsal we were half - naked because it was too hot then. I heard some distortions in the right channel speaker. Amps were on the edge of the stage, so I took screwdriver and opened the cover of the right channel amp (it was 100W tube amp, with voltage doubling rectifier, so 300V was on one electrolytic can). Then I saw a smoke going from underneath the chassis, so I took the amp by both hands and tilted on my belly, to look under the chassis, what is burning...
I don't remember what was burning, but I remember myself sitting on the chair in the front row, trying to calm down...
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Now it does not sound so terribly when overdriven, but is not it too thin when played clean? Additional sneaky control with feedback seems to fix it: low end cut depends on gain control knob's position. Both pots, tone and gain, are inter-dependable. Should I patent it, huh?
YouTube - World Champion guitar amp project -- overdrive tone control added
YouTube - World Champion guitar amp project -- overdrive tone control added
I agree with you a tidy ordered workplace is much safer than one that is not. In a year from now I may have one. But since that will not happen in the duration of this contest the 24" x 24" electronic work space that I have (just measured it) with my back to the clothes dryer (which I do use as temporary stand for my speaker). No I do not work when I am distracted or tired, it usually is counterproductive to do so.
Mind you this is during my hobby time. At work you are paid to get the job done, tired or mot. Working in industry some of us do not have the luxury of a workbench or even good lighting. More often than not I crawl into places with my trusty Magllite, a while back had a trouble light behind me with a 600V 3 phase speed drive half apart on the wall while standing on a ladder (No hand in my pocket as I needed it for three point contact), wondering why I left that cushy repair job.
In a perfect world we would have all the tools and time at our disposal at work and at our hobby to do things right. Sadly this is not a perfect world.
Yes, high voltages in tube amps are dangerous. Once during rehearsal we were half - naked because it was too hot then. I heard some distortions in the right channel speaker. Amps were on the edge of the stage, so I took screwdriver and opened the cover of the right channel amp (it was 100W tube amp, with voltage doubling rectifier, so 300V was on one electrolytic can). Then I saw a smoke going from underneath the chassis, so I took the amp by both hands and tilted on my belly, to look under the chassis, what is burning...
I don't remember what was burning, but I remember myself sitting on the chair in the front row, trying to calm down...
I am glad to see you are still with us! As innocent as your actions were, I would also bet you would never do that again.
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Right; I was young and innocent. A bit older than on my current avatar.
Here are pictures of my current breadboard: preamp and power stage, using sub-miniature tubes. 6N21B tube can be replaced by 6N2P or 12AX7, 6P30B can be replaced by 6P1P or 6V6.
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Right; I was young and innocent. A bit older than on my current avatar.
Here are pictures of my current breadboard: preamp and power stage, using sub-miniature tubes. 6N21B tube can be replaced by 6N2P or 12AX7, 6P30B can be replaced by 6P1P or 6V6.
Your project is interesting and the sounds of your amp is not bad either. Keep improving it as I am looking forward to see the final version. I would especially like to hear it with a 6V6.