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Old 17th March 2012, 09:11 PM   #11
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okay . you will need equiptment . variac high voltage insulated test leads .voltage and current meters capable of handling the voltage .

oh well . a blast shield like george uses is also a good precaution . invest in a Proper galvanic isolation before even commencing work on anything !

think about this first . how are you going to power two 10V 10A heaters ?

Ok DC heating is required this will mean lineair or switchmode . oh well if you go lineair transformer has to be rated at 14-15 volts AC at 16 amps or so to keep a fair bit of headroom to regulate .

15 volts AC gives about 12.5-13 under load . needing a minimum of 22,000 u of smoothing
imagine 20 % line sag . your regulator will fall out of regulaton! resulting in ripple .
so we add 20% to our 15 volts =18vac this will give us about 15 volts DC under load wich means the regulator is likely regulating about 50 watts ! under normal line conditions .

Imagine high line you will have 21.6 Vac unloaded yet giving 18VDC you guess your reg. is now regulating a whopping 80 watts !

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Old 17th March 2012, 09:37 PM   #12
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A 833 SET is a great project, why lose time and money with Pentodes and PushPull!!
Safety procedures are many>: use rubber gloves, not put both hands on the amp, not use a wrist watch or rings, Static discharge in transformers can happen above 500V, so transformers may need cover or insulation.
Good Luck.
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Old 17th March 2012, 09:49 PM   #13
lechuck is offline lechuck  Netherlands
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Quote:
Originally Posted by Thesoundmen View Post
-I haven't build a tube amp yet but I builded some others thing like DAC and phono and ect. I have a degree in electric en electronics so I'm not new with electricity
- one reason I love the big old tubes
- For the moment I have a pair of B&W 802N
-budget is no fator , Topology I would like Class A, power output somewhere between 50 -200 I think
If you like big tubes, there is a bigger tube than the 833C available. Its called a TB3-2000 and apparently it should be good for about 500 watt of pure class A musical pleasure

If the budget is not a problem for you then I suggest you take a look at this website: http://home.tiscali.nl/fishbowl.amping/

The owner of the site build it, according to him it sucks up about 5.5KW without even playing a single note

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Last edited by lechuck; 17th March 2012 at 09:55 PM.
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Old 17th March 2012, 09:53 PM   #14
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I am building a PP AB2 GU81m amplifier. 12.6v @44A Had all the transformers made custom. the thread is in the section if you want to take a look. waiting for the power trasformer. The high voltage transformer alone weighs 12-14kg. The low voltage (650va core) weighs 6kg the transformers for the ercury rectifiers weigh as much.



go for it.
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Old 17th March 2012, 10:18 PM   #15
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Yes, it is possible to DIY an 833 type amp. See this thread for some examples:

Where are the 833 amps?

I must say that the 833A or 833C amp should not be anyones choice for a first time tube amp build. Let's just say that you understand all the safety stuff, and you read everything ever written about vacuum tubes until you fully understand them. Most builders have some difficulties with their first amp expecially if is is built using point to point wiring just chasing the hum out of it. More than a few builders blow up a few parts. At the power and voltage level needed for an amp like this stuff gets expensive quick. Custom parts are usually needed, like transformers, and the transformer winder may not even know how to make them.

I have been building tube amps for nearly 50 years. I can generally make whatever amp I want, but I abandoned my attempt at making an 833A SE amp because I couldn't get a suitable OPT. The 833A has a fairly high plate resistance and the OPT design is rather difficult.

My experiments are here:

The 833A SE Amp Prototype
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Old 17th March 2012, 10:57 PM   #16
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thanks for all the replies,

okee the 833c plans is maybe not the best choice to start with.

Are there people with some idea's for a diy mono block amp project with some nice tubes ?
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Old 17th March 2012, 11:00 PM   #17
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someone experience with the Eimac 304TL ?

ore is that some what the same as the 833C ?
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Old 18th March 2012, 12:14 AM   #18
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I think you should abandon the idea of using any of the bigger transmitter triodes for a first build. I've got a few lower power transmitter tubes, including a quartet of HF100's with graphite anodes, and I'm not yet ready to make amps with such voltages. 500V B+ is actually quite easy; just understand the basics, keep in mind that some wires have insulations rated for only 300V or some even less, and make a nice clean build (avoid messy wiring).

But when the voltage jumps up to the kilovolt range these tubes need to work, you'll have to take the voltage into account in almost every part! Plus output transformers for low powers are hard enough to be made decent, so with voltage and power ratings going up, it get's even more difficult. I've seen pictures of a Philips amplifier, that gave a kilowatt of class B power out of 2 TB3/350's. It's OPT was immersed in oil. And it needed 3-phase power...

My second question is, actually how much power do you need? 20W of class A power is actually quite much in most circumstances. Having played around with some circuits and concepts for some years now in tube amplification, I would even go as far as to suggest a single watt spud amp as your first build. It would probably not satisfy all your needs, but would give some perspective as to what really is necessary. I did build one, with an E55L, and got quite amazed.

In my main system I run KT88's in triode, class A push-pull. They put out around 20 watts of mostly clean power. They have no feedback loops. And their sound have amazed most that have listened to them. You could raise the power output for example by doubling the amount of output tubes, but then you'd run into other problems. And with more than 90 dB/W/m sensitivity, it's not really necessary. Even this amount of power can make my ears hurt. So 200W of Class A sounds quite extravagant... Plus you'd be idling at around a kilowatt per channel... Half a kilowatt if you got it right and used push-pull pentodes. And that doesn't include the heaters...
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Old 18th March 2012, 01:13 AM   #19
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Quote:
Originally Posted by Adolf Corkscrew View Post
I think you should abandon the idea of using any of the bigger transmitter triodes for a first build. I've got a few lower power transmitter tubes, including a quartet of HF100's with graphite anodes, and I'm not yet ready to make amps with such voltages. 500V B+ is actually quite easy; just understand the basics, keep in mind that some wires have insulations rated for only 300V or some even less, and make a nice clean build (avoid messy wiring).

But when the voltage jumps up to the kilovolt range these tubes need to work, you'll have to take the voltage into account in almost every part! Plus output transformers for low powers are hard enough to be made decent, so with voltage and power ratings going up, it get's even more difficult. I've seen pictures of a Philips amplifier, that gave a kilowatt of class B power out of 2 TB3/350's. It's OPT was immersed in oil. And it needed 3-phase power...

My second question is, actually how much power do you need? 20W of class A power is actually quite much in most circumstances. Having played around with some circuits and concepts for some years now in tube amplification, I would even go as far as to suggest a single watt spud amp as your first build. It would probably not satisfy all your needs, but would give some perspective as to what really is necessary. I did build one, with an E55L, and got quite amazed.

In my main system I run KT88's in triode, class A push-pull. They put out around 20 watts of mostly clean power. They have no feedback loops. And their sound have amazed most that have listened to them. You could raise the power output for example by doubling the amount of output tubes, but then you'd run into other problems. And with more than 90 dB/W/m sensitivity, it's not really necessary. Even this amount of power can make my ears hurt. So 200W of Class A sounds quite extravagant... Plus you'd be idling at around a kilowatt per channel... Half a kilowatt if you got it right and used push-pull pentodes. And that doesn't include the heaters...
After reading this your nice post, I would change the output tube for a 805 top cap tube.
Or even buy a assembled 805 amp, as Ming-Da to clean 40W or ASL to 50W and a around 100dB speaker>:
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Old 18th March 2012, 03:02 AM   #20
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As others have already noted, iron will get in the way of acceptable results. If you find out a way around this, please let the rest of us know.

Quote:
Originally Posted by riccoryder View Post
...with suitable output transformers
Quote:
Originally Posted by tubelab.com View Post
I abandoned my attempt at making an 833A SE amp because I couldn't get a suitable OPT.
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