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Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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Old 26th August 2008, 11:38 AM   #91
jamesgate is offline jamesgate  United States
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Default circuit safety question (noob question)

After reading this thread, I'm now respectfully cautious approaching my first project, but I also have visions of my first amplifier melting down on the workbench, the victim of cascading component failures. What are the inherent safety factors that go into a tube based amplifier circuit, how do you protect it from itself? Is it the high voltage components? What if they burn up? Is it the distance between components? If 120VAC becomes 400VDC, why not 600V if something breaks, creating a domino effect? What keeps 400V from the cabinet, the on/off switch, or the volume potentiometer ?

Also, I was looking at several inexpensive kits and it seemed clear the power supply plugs were not grounded plugs, they were two prong. I would have expected a grounded plug to be fundamental for safety. Why or why not?

On test equipment, there are references to a "signal generator" - does a Hewlett Packard 200CDR "Wide Range Oscillator" count? The range is 5 - 600,000 Hz, I've used it to test frequency response in speakers. If not this Oscillator, what should I look for, something that can do shaped waves, such as square or saw tooth, as well as sine waves? I also have a surplus HP1220A Oscilloscope and an older HP141B OScope with 1423A Time Base and 1402A Dual Trace Amplifier - will these be worth renovating? Or is this type of equipment 'old school'?

When you test an amplifier for quality of output, how much do you depend on the test equipment compared to listening tests, and how accurate can you get at all gain levels? Do you expect to see
a) low noise (of course),
b) accuracy at the output stage from 20 - 20,000Hz at some gain levels,
c) accuracy at the output stage at all gain levels,
d) a nice sounding amp, almost regardless of what shows on the oscilloscope?

Thanks much -
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Old 7th September 2008, 02:49 AM   #92
Zero Cool is offline Zero Cool  United States
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Originally posted by BHD
This is a great idea for a thread.

This is one of the best beginner sites I've found, it walks you step by step through the design and construction of a simple single ended amp:


WOW this was an awesome read! Thank you for this link!


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Old 24th September 2008, 03:36 PM   #93
etinsley is offline etinsley  United States
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All About Circuits has a chapter devoted to tubes that is very well written.


Also, this link really helped me to understand how tubes work. It has cutesy diagrams that helped me to "get it."

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Old 11th November 2008, 04:39 AM   #94
lowtherdream is offline lowtherdream  Canada
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Location: Montreal, Quebec, Canada
Default Slow learner ...

I have been reading a lot of info and documents about tube amps ... but I still don't fully understand what makes a good tube combination.

In a 2 stage amp, what makes the input/driver stage couple well with the output stage ?
In a 3 stage amp, what is the right combo, and are there rules to follow for stage amplification factor ?

I do understand how each stage is build and calculated, but I found little info that explains stage coupling. Can you please guide me to some specific documentation or maybe explain what the parameters that guide stage coupling ?
surfing the 2nd harmonic ... @@@@
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Old 11th November 2008, 04:04 PM   #95
Cobra2 is offline Cobra2  Norway
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On Line Tube Learning for newbies.... On Line Tube Learning for newbies....
Default Re: New To Tube Testing

Originally posted by 6550stan
Hi, Great site here LOADED with info! My name is Stan & I'm from New York. I have a question on my B & K Dyna-Quik Model 650 & would be beyond grateful if someone could help me. I have a hundred + 6550 International KT-88 tubes and cannot figure out if my B & K has the socket for proper testing. Based on my built in chart that # falls in between two others with completely different sockets,sensitivity #'s & heater#'s. I am new to this end but not new to using tubes. Thanks & great site! Awesome info- I feel like I found a new home! If I need a new tester please let me know the best and most affordable recommendation. 6550stan
B&K 650 settings; (picture) (Tube/Heater/Socket/Section/Test-Pos/Good-Bad/True GM/Std.GM)

Do you not know; It's illegal to have hundred+ KT88/6550 in one house...
I would like to buy a few

Arne K
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File Type: gif b&k 650-1.gif (39.9 KB, 1186 views)
Don't believe everything you think...
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Old 10th February 2009, 12:31 PM   #96
dazzler is offline dazzler  Australia
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there's a lot of good info here. sorry if it's been mentioned. lots of book downloads.

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Old 29th May 2009, 04:22 PM   #97
cheap-Jack is offline cheap-Jack  Canada
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Originally posted by noisenyc
check this lads. the radiotron online!


this mirror seems to be the fastest:


Yes, RDH4 is a must to read for tube & related electrical/electroncis theories. Without sound therories one can't go very far in tubing/electronics building.

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Old 7th August 2009, 04:51 AM   #98
squire is offline squire  United States
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Default thanks

this thread is a godsend was getting frustrated trying to find a place to start with tubes
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Old 31st August 2009, 02:41 AM   #99
hendra1471 is offline hendra1471
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You can search in www.pmillett.com. a great web for book of tube
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Old 8th September 2009, 06:51 AM   #100
garlach is offline garlach  Luxembourg
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Location: Europe
Question Basic question from clueless newbie

In a bi-amped system with one valve amp and one solid state (of roughly equal power) to choose from, would it be preferable to use the tube amp for high frequencies and the solid state for the low end, or vice versa? (crossover freq: 300Hz).

Thanks - I hope this isn't a controversial point, and that there is one, simple answer
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