He wants to build a tube amp, not SS.
I think Justin wants a bit more power than anything from BH.
jeff
I do appreciate everyone's feed back. Dynakit has my interest at the moment. It says Type A is out of stock. It explains that...
Full kit package, less tubes and top vented cover. Kit requires user assembly of PC board. Choose either type: (A) carbon composition resistors or (B) metal film resistors. INCLUDES (2) SA-6GH8A 9 Pin Socket Adapters. Includes our new brown Polyimide circuit board!
Type A is 25 bucks more then type B. Are the Carbon Resistors but much better? I have also read some tubes have better sound quality over others, is that something that can be customized in the future just by switching out the tubes?
Full kit package, less tubes and top vented cover. Kit requires user assembly of PC board. Choose either type: (A) carbon composition resistors or (B) metal film resistors. INCLUDES (2) SA-6GH8A 9 Pin Socket Adapters. Includes our new brown Polyimide circuit board!
Type A is 25 bucks more then type B. Are the Carbon Resistors but much better? I have also read some tubes have better sound quality over others, is that something that can be customized in the future just by switching out the tubes?
Justin, kits are nice. Finding an old amp that needs fixing is also a great way to learn.
I'd suggest posting your build and people will chime in with how to measure voltages, bias current, ... You will learn ohms law and how to calculate power.
You will need a few tools. I use a variac, scope, volt meter, function generator, and an 8 ohm load for most of my builds.
I'd suggest posting your build and people will chime in with how to measure voltages, bias current, ... You will learn ohms law and how to calculate power.
You will need a few tools. I use a variac, scope, volt meter, function generator, and an 8 ohm load for most of my builds.
In this instance, building a new amp, not really.
Have you ever set an ohm meter to megohms and held the probes between fingers on opposite hands? You conduct a little bit of electricity.
The big risk with high voltage is creating a circuit that passes your heart. This can kill you. Easily.
There is well documented history that a truly talented individual once killed himself with no more than 9 volts. But he really tried. Sharpened the probes of his ohm meter and impaled his thumbs. That, plus bad luck, stopped his heart. He was in the navy. The navy officially swears that this story is true.
Gloves can't help you with this, when you are dealing with high voltages. There are gloves that offer enough protection, but you won't be able to manipulate any electronics while wearing them.
The rule is that if there is any possibility that the circuit is live or that a capacitor might be charged, you keep one hand in your pocket. Always.
That way, unless some other part of your body touches the chassis, the shock will just hurt really, really bad.
I hear that letting 300vdc go through your finger feels a lot like whacking it good and hard with a hammer. So far I've been lucky not to experience this.
The ONLY acceptable alternative to 1 hand in a pocket is 1 hand wrapped around your belt, in the small of your back. Don't get a deadly cardiac shock!
I've been "bitten" by approx. 475 VDC, very locally. It hurts and a puff of smoke indicates where a tiny bit of skin has been vaporized. There was no permanent damage, because I heeded the only 1 hand warning. You may ask, why was I that clumsy? I'm very much right hand dominant and I was forced, by the specific situation, to work left handed.
I've been "bitten" by approx. 475 VDC, very locally. It hurts and a puff of smoke indicates where a tiny bit of skin has been vaporized. There was no permanent damage, because I heeded the only 1 hand warning. You may ask, why was I that clumsy? I'm very much right hand dominant and I was forced, by the specific situation, to work left handed.
Since you are just starting off you can choose to jump in the deep end or start off at the shallow end of the pool. The ST70 is at the deeper end with 500vdc power supply and 7 tubes in a push pull circuit. If you manage to surface you will be swimming in 35 watts (about) of power. If you want to start off at the waist deep end buy one of the old single ended el84 powered single ended amps like the ones made by Zenith or Magnavox also EICO and Voice of Music. These amps have less than half the parts of a Dynaco in a much simpler circuit and a power supply that is usually around 300vdc. Almost all of them have documentation easily available which means learning how to follow a schematic simple. They are pretty cheap usually about a hundred for the amp with tubes. Down side is power of only about 5 watts but you will be surprised at how loud and how nice that will be with medium efficiency speakers. Remember, more than 90% of the music from your speakers is less than 1 watt of power! With the money saved from your purchase you will be able to buy the new tools needed to work on tube amps, like a digital multi meter, variac, soldering iron, long nose pliers, etc. Good luck, 808
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Thanks, for the input Dak. Started looking at older amps on ebay like you mentioned. I did find some ST-70s. Do you still think that would be to far out on the deep end?
Not at all. However, used ST70s often sell for about the same (or more) than the new kit.
I'd definitely go for the kit unless you can find a very cheap used amp. Most used ST70s will
require a complete rebuild, replacing everything except the chassis, transformers, and choke.
Often the chassis is corroded as well.
No, it is more like you have lost control of your muscles which are painfully spasming which at the same causes you to scream like a 12 year old girl!
It is not so bad. Besides if medical professionals can prescribe electrodes on both sides of your head and shoot electricity across your brain a jolt at the tip of a finger cant be much worse? Just be careful and don't drink more than a cup of coffee in the morning. cheers, 808
Hi Justin, the good thing about the Dynaco is that there is much information associated with it. I personally, think, now that I have had many years of working on tube equipment, that a single ended pentode amp like the Maganvox or Zenith EL84 types, there are also others, are the simplest circuits to work on. About the hardest thing to do is to equip it with modern conveniences like an on/off switch, and speaker binding posts. The circuit is simply an input/driver tube that is capacitor coupled to a power tube. Looking at a schematic and it is very simple to follow. It is a good warm up for when you want to tackle push pull amps. And the sound from that simple little amplifier can be extremely rewarding to the ears. cheers!
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If you have not heard a single ended amp in proper working condition you will be impressed. The SE EL84 amps are very capable if your speakers are of adequate sensitivity. My JBL L112 are around 91db and they can play my RH84 amp loud enough for my wife to start complaining. But loud is not what they excel at. They have the ability to convey the subtleties of the record that is sometimes lost in push pull amps. the sound is perhaps smoother more continuous and perhaps more realistic or natural. It is hard to convey in words.
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