This is a very good alternative, but I will use a 2.7 ohms resistor instead because the 5CZ5 heater is rated 4.7V 0.6A and the voltage drop needed is 1.6V .
That is true we can get some 5CZ5 for 3$ or less on eBay but this price don't include the shipping and they are not always tested. In United State, the shipment cost is very low but to Canada where I live, it is sometime very high ...
I just look on eBay and I get 31 results for 5CZ5 tube so they are not rare. Somebody sell four used one tested strong for 19.99$US + 2$US shipping in USA and 8.24$US in Canada. If anyone interested, there is 6 days left, here is the link :
4 Vintage RCA 5CZ5 Vacuum Tubes Tested Strong Audio HAM Radio Amplifier | eBay
Thank you, I never heard about this place before, I will look at their stock, prices and shipping fee right now. In Canada, the shipping fees is a big problem when we buy from USA, most business ship only by "priority mail" instead of "economy international". It is really stupid to paid over 40$ for something that worth only 10$ and when I buy something on Internet, I am not in a hurry, I don't care if I receive it 2 or 3 weeks later.
Vacuum Tubes - Audio Tubes - ESRC Vacuum Tubes - Electron Tubes
Thanks,
You are right, The Tube Store is in Canada :
120 Lancing Drive, Unit 8
Hamilton, Ontario
L8W 3A1
Canada
They ship by FedEx or mail but I don't think the shipping can be less than 10$CAN ... The 5CZ5 at ESRC are only 3$US but at The Tube Store, they are 5.95$US and if I order 6, it will cost me over 45$ for sure the shipping included and they don't accept Paypal and the minimum order before shipping charge is 19.90$US ...
After all, I think the best place to buy for me will be ESRC, their prices are lower, the shipment in continental US for 6 small tubes is 7.95$US, for 7 to 15 tubes 8.95$US, there seem to be no minimum order and they accept Paypal, my preferred way to paid. I don't ask them yet but if they can send order by economy international shipping, it will not be much more than in USA, probably less than 10$US, maybe, 6 5CZ5 from them will cost me a total of about 28$US instead of around 45$US at The Tube Store.
It is not because I am cheap, I am not rich and I don't like to throw my money by the windows for nothing. I also notice ESRC have all types of tube sockets and caps too for 2$ each, this is a very good price. I am thinking building an amplifier with the 5CZ5 because in a push-pull AB1 fixed bias circuit, they can give up to 21 watts with only 1% THD, much less if I add a overall negative feedback and it is suppose to be possible to use a output transformer from 5000 ohms to 8000 ohms plate to plate. With a 5000 ohms transformer, the power will be about 15 watts but the THD will also be 1%, this is with a 350V plate and 280V screen grid supply.
I like to design an amplifier with good low cost tubes because we will use it every day and the power tubes have to be changed often, if I paid 200$ more every year for big hifi tubes like 7591A or 8417 (50$US), after 10 years, this is 2000$ ... a lot of money.
If you are building from scratch, you might want to consider other low cost output tubes besides just the 6V6, 6973, 6CZ5, 6AQ5, .... series.
Looking at ESRC's list:
(And take a look at this other place in Florida too, similar prices, many other tubes besides: http://www.vacuumtubesinc.com/ )
6HJ5 $4
6JN6, 6GE5 $6
12JN6 $3
17GE5 $3
6GB5/EL500 $5
13GB5 $1 (on the doller list)
25CD6 $4
21JV6 $4
33JV6 $3
6CB5A $5
6JC5 $5 (bigger 6CZ5)
6EZ5 $4 (octal 6CZ5)
6HB6, 15HB6 $3
25DQ6 $3
12GC6 $3
26DQ5 $3
17GV5 $4
16GK6, 29GK6 $3 (EL84)
21GY5 $4
16GY5 $3
21EX6 $3
17GJ5A $4
17GT5A $5
12GT5A $3
17GW6 $5
12AV5GA $3
12GJ5 $5
.......
Looking at ESRC's list:
(And take a look at this other place in Florida too, similar prices, many other tubes besides: http://www.vacuumtubesinc.com/ )
6HJ5 $4
6JN6, 6GE5 $6
12JN6 $3
17GE5 $3
6GB5/EL500 $5
13GB5 $1 (on the doller list)
25CD6 $4
21JV6 $4
33JV6 $3
6CB5A $5
6JC5 $5 (bigger 6CZ5)
6EZ5 $4 (octal 6CZ5)
6HB6, 15HB6 $3
25DQ6 $3
12GC6 $3
26DQ5 $3
17GV5 $4
16GK6, 29GK6 $3 (EL84)
21GY5 $4
16GY5 $3
21EX6 $3
17GJ5A $4
17GT5A $5
12GT5A $3
17GW6 $5
12AV5GA $3
12GJ5 $5
.......
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And maybe even those cost too much...there's a dollar menu! Summer Dollar Days - Vacuum Tube Sale - $1.00 Vacuum Tubes
6T10
12HE7
13GB5
17BQ6
25CU6
25DN6
...and others.
Or perhaps you don't want to use plate caps, don't want to find Compactron, Novar, Magnoval sockets - these are a dollar each as well...
6DB5
6HB6
6JQ6
12BK5
12DB5
12EN6
12JQ6
Of course, you'll have to buy your 10-year supply NOW, but it will cost about the same as a pair of 6L6s...
6T10
12HE7
13GB5
17BQ6
25CU6
25DN6
...and others.
Or perhaps you don't want to use plate caps, don't want to find Compactron, Novar, Magnoval sockets - these are a dollar each as well...
6DB5
6HB6
6JQ6
12BK5
12DB5
12EN6
12JQ6
Of course, you'll have to buy your 10-year supply NOW, but it will cost about the same as a pair of 6L6s...
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Using cheap tubes for projects is a good thing but it is better to verify first if they are not too rares because they will have to be changed one sooner or later.
For instance, I buy a 6B5 just for experimenting four years ago on eBay for about 2$US + shipping, now they are sold for much more, they are 18$US at ESRC. This is a funny tube design to work in class A1, containing a power triode and a triode driver, directly coupled, 4 watts output in a 7000 ohms load. I was looking for a power triode that can be used with a old radio 2500 to 3,2 ohms transformer but with a 8 ohms speaker, the ratio is close.
It is probably possible to build a nice amplifier using some 12BQ6GTB/12CU6 but taking care not exceeding the maximum screen grid voltage of 200V. Many of these old TV horizontal deflection tubes are very interesting, I got some in my "junkbox".
The trick is to buy enough tubes now to last 20 years once you find a cheap one that works well for you.
If you are going to buy a new PT, OTs etc, and build from scatch, I wouldn't necessarily go with the cheapest tubes though.
Here is a list of low cost TV Sweeps that I would consider for building with:
6JC5 if you want to stay with the high primary Z OT (maybe 5 to 8K P-P, capless tube) 6V6/6CZ5 class stuff (vertical sweep).
6GE5/6JN6/12GE5/12JN6/17GE5..../17GV5 for up to 50 W P-P (like 4.2 K to 6 K P-P OT, GE and JN are capless, good reports on sound)
(looks like 12GT5/12GJ5/17GT5/17GJ5/17GW6 are very similar, I haven't seen much built with these yet, the GT is capless)
13GB5/EL500 ($1, takes an oddball magnoval socket, there has been some experimenting with this lately online, haven't heard any sound evaluations yet, EL500 plate curves look good) maybe 3.3K OT
GU50 oddball sockets (cost more than the tube), oddball looking tube, uses higher Z OT with high B+, low cost Rusky tube, lots of good reports on sound
6HJ5/6CB5/26DQ5/21LG6/35LR6 for up to like 100-120 W P-P (with like 3.3K P-P OT) (the 6HJ5 is capless by the way, George got like 150 Watt, good report on sound) the LG and LR being more pricey if you want to splurge for world class plate curves, LR can do around 150 Watts full time (I think George gets like 200W with a pair!!) maybe a 2.5K OT for the LR
If you are going to buy a new PT, OTs etc, and build from scatch, I wouldn't necessarily go with the cheapest tubes though.
Here is a list of low cost TV Sweeps that I would consider for building with:
6JC5 if you want to stay with the high primary Z OT (maybe 5 to 8K P-P, capless tube) 6V6/6CZ5 class stuff (vertical sweep).
6GE5/6JN6/12GE5/12JN6/17GE5..../17GV5 for up to 50 W P-P (like 4.2 K to 6 K P-P OT, GE and JN are capless, good reports on sound)
(looks like 12GT5/12GJ5/17GT5/17GJ5/17GW6 are very similar, I haven't seen much built with these yet, the GT is capless)
13GB5/EL500 ($1, takes an oddball magnoval socket, there has been some experimenting with this lately online, haven't heard any sound evaluations yet, EL500 plate curves look good) maybe 3.3K OT
GU50 oddball sockets (cost more than the tube), oddball looking tube, uses higher Z OT with high B+, low cost Rusky tube, lots of good reports on sound
6HJ5/6CB5/26DQ5/21LG6/35LR6 for up to like 100-120 W P-P (with like 3.3K P-P OT) (the 6HJ5 is capless by the way, George got like 150 Watt, good report on sound) the LG and LR being more pricey if you want to splurge for world class plate curves, LR can do around 150 Watts full time (I think George gets like 200W with a pair!!) maybe a 2.5K OT for the LR
I never buy new power and output transformers because I already have a lot of them salvaged from old scrap sound systems, radios and TV since over 40 years, also hundreds of tubes of all kinds and thousands of other parts. Sometime, I buy some cheap little low voltage transformers in Montreal surplus stores for semiconductor projects but that's all.
Most of my output transformers are small single end type but I also have some big and high quality ones. My goal is to use all those transformers for small tubes projects, just for fun. For instance, for all pair of small output transformers I have, I can build a little stereophonic amplifier for computer or a MP3 reader, if I only have one, I can build a monophonic amplifier with a two channel mixer or a small guitar amplifier with a "antique looking". Today, tubes amplifiers and radios become a curiosity, many young people never see a tube and they are fascinated by those rare things.
Designing a small and simple tube amplifier is nothing, it just took me a small afternoon to calculate all the parts and make the schematic and cabinet plans. I got all the tools needed to build the cabinets myself from salvaged steel sheets, it cost me nothing, just few hours of work.
Of course, I don't do only audio DIY, I build all kinds of electronic equipments and machines because I am also interested by mechanic, informatic, wood and metal working, artistic and technical drawing, gardening, cooking, politic, etc. I am always very busy, I hope I will live up to 100 years old to be able to realize all my projects, time run so fast when we have fun.
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I don't need a power of more than 20W by channel for my home sound system, I never listen music at over 5W because my bass reflex low power speakers are very efficient. So I have a lot of choice for the tubes, but I will use the highest quality for the lowest price for my next amplifier. But I am not in a hurry, the 1974 6W by channel Kenwood receiver I got now work very well and have a very nice sound, the only problem is the controls are getting dirty and used and I prefer building a new amplifier than replacing all them. I got many other and more recent "HIFI" transistors sound systems but they all sound like crap beside my old Kenwood.
The problem with the big tubes amplifiers is the cost of the output transformers, if I need more than 20W, I will go to a OPT design using a impedance matching auto-transformer if necessary. They don't have to be big in a OPT amplifier because there can't be any DC saturation, and isolation is not necessary. The coupling is also better because there is only one winding. Last year, I work many months on a good OPT design (using my SiMetrix simulator) using cheap 6080, 6082, 6AS7G or Russian 6N13S twin power triodes, I already got some in my workshop.
I will probably build a powerful one for my subwoofer, maybe next year if I got time, but I have to test the prototype first. The supply for the power triodes can be less than +/- 200V but the drivers tubes most work at a much higher voltage. I will use some 6SN7GTA or 6SN7GTB for that because they have a maximum AK voltage of 450V (design center value) and use a full wave voltage quadrupler to get the necessary supply.
The problem with the big tubes amplifiers is the cost of the output transformers, if I need more than 20W, I will go to a OPT design using a impedance matching auto-transformer if necessary. They don't have to be big in a OPT amplifier because there can't be any DC saturation, and isolation is not necessary. The coupling is also better because there is only one winding. Last year, I work many months on a good OPT design (using my SiMetrix simulator) using cheap 6080, 6082, 6AS7G or Russian 6N13S twin power triodes, I already got some in my workshop.
I will probably build a powerful one for my subwoofer, maybe next year if I got time, but I have to test the prototype first. The supply for the power triodes can be less than +/- 200V but the drivers tubes most work at a much higher voltage. I will use some 6SN7GTA or 6SN7GTB for that because they have a maximum AK voltage of 450V (design center value) and use a full wave voltage quadrupler to get the necessary supply.
Small changes needed !!!
The 6CZ5 is supposed to be a good substitute for the 6973 tube. I tried this substitution in an old AMI jukebox amplifier, and the 6CZ5s over heated and turned cherry red. Can any one spot the problem using them in this circuit? (The pin voltages are in the table.)
An externally hosted image should be here but it was not working when we last tested it.
BTW, I bought a set of Electro-Harmonix 6973s, and they work fine.
Retired EE who never played with tubes before, that's how long SS has been out!
The 6cz5 / 6em5 will work nicely but you have to control grid 2 volts and disconect from pin 8 and reconnect to pin 2 ....then everything will be sweet ...
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