Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Oct Wed 21, 2020 12:48 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 44 posts ]  Go to page Previous  1, 2, 3  Next
Author Message
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Tue 06, 2020 6:59 pm 
Member

Joined: Feb Fri 27, 2015 3:19 pm
Posts: 96
This is for Peter Bertini,

Hi Peter, we are old acquaintances from the days radio magazines were printed than posted.
By saying same brand, made me infer that only the manufacturer of the original tube would make the tube under the same original number, in other words, only, for example, Philips made a 6V6GT and no other manufacturer would make the same specs tube using the same number, in which case, I may be able to find, say, a Mazda 6V6PE which has the same specs as the Philips 6V6GT and I can use the Mazda tube. So, by saying same brand you meant same tube number but only the original tube manufacturer could use that number, is that correct?


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Wed 07, 2020 3:42 am 
Member
User avatar

Joined: Sep Mon 16, 2013 2:42 am
Posts: 4227
Location: Tucson, Arizona U.S.A.
Tube numbers were mostly generic; they were made by many manufacturers. A Philips 6V6GT is the same as an RCA 6V6GT, Sylvania 6V6GT, Raytheon 6V6GT, GE 6V6GT, etc. There were some manufacturers that made tubes with proprietary numbers but they were mostly industrial or military types.

_________________
Jim Mueller


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Wed 07, 2020 4:36 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22817
Location: Haledon, NJ, usa
I have used the 6p6s Russian and Chinese made 6p6s
these 6v6 type tubes sound beautiful...

Check Bob's good prices for both new and used 6v6g and 6v6gt
And if you can use the 12V6gt they are undr $5 new:
https://docs.google.com/spreadsheets/d/ ... 0foD#gid=0

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Wed 07, 2020 7:27 am 
Member

Joined: Nov Fri 30, 2012 3:35 am
Posts: 452
Location: Phoenix, AZ
If one is building up a new design based on the 6V6 but doesn't mind 9-pin tubes, I suggest also considering the 6CM6 as an inexpensive option. I built a compact P-P stereo amp using 6CM6s. Very sweet. I installed tall-envelope RCAs; I think TungSol also made them in a tall envelope ... but every Sylvania 6CM6 that I've seen is in a shorter envelope, a lot packed into a small volume.
R/ John


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Wed 07, 2020 6:09 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5770
Location: 253 Blanche St. Plymouth, MI USA
Also, consider using the cheaper 6K6GT, a mostly forgotten output that was very popular in TV's 1946-1958 or so. Specs are 8.5watt vs 12 watt for 6V6GT but that may be plenty.

Also, look at the 6W6GT and 6Y6GT which also was offered in the G envelope. Beware, both pull a over double the heater current !

_________________
Mark Oppat
Antique Audio
Plymouth, MI
http://www.oldradioparts.net


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Wed 07, 2020 10:12 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22817
Location: Haledon, NJ, usa
UV201 wrote:
If one is building up a new design based on the 6V6 but doesn't mind 9-pin tubes, I suggest also considering the 6CM6 as an inexpensive option. I built a compact P-P stereo amp using 6CM6s. Very sweet. I installed tall-envelope RCAs; I think TungSol also made them in a tall envelope ... but every Sylvania 6CM6 that I've seen is in a shorter envelope, a lot packed into a small volume.
R/ John

The 7pin 6AQ5 and 12AQ5 are also great "6V6 tubes" in smaller envelopes

As a matter of interest... I built several 6v6gt stereo amps recently both PP and SE
( http://pbpix.com/amp/ )
(http://pbpix.com/amp/se%2012sl7%206v6%20%20tubes.jpg )
( http://pbpix.com/amp/SE%206V6%20amp%206-12%20switch.jpg )

I used 12v for filaments so I was able ( with an A/B switch) to use either two 6v6s in series or two 12V6s in parallel.
I also added 7-pin sockets in parallel with the octal sockets so I can choose to use the 6AQ5/12AQ5 tubes too.

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Thu 08, 2020 12:50 am 
Member

Joined: Nov Fri 30, 2012 3:35 am
Posts: 452
Location: Phoenix, AZ
Yes, I agree on the 6AQ5. Although it's a bit smaller, I think it's an overlooked gem. My musical tastes are classical at low to moderate volume levels, and the 6AQ5 (or 12-volt version) is excellent for the purpose.
I've never built an amp using the 6K6, 6W6 or 6Y6 ... but I agree, they seem to be largely forgotten types. With a proper design there is no reason they couldn't sound very good. Yes, the heater power required in the W and Y might be a concern.
R/ John


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Thu 08, 2020 3:17 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5770
Location: 253 Blanche St. Plymouth, MI USA
Another way to save big bux is to use the same tube with odd voltage filament. The 5V6GT is cheap. 5 V xfmrs are available of course. The 5V rectifier winding on a radio power xfmr is rated usually 2A for a 5Y3 or 3A for a 5U4.
The 5V6 wants .6A per tube. So 4 of them is 2.4 A

_________________
Mark Oppat
Antique Audio
Plymouth, MI
http://www.oldradioparts.net


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sat 17, 2020 4:42 am 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 14537
Location: Central PA 16801
oldradioparts wrote:
Another way to save big bux is to use the same tube with odd voltage filament. The 5V6GT is cheap. 5 V xfmrs are available of course. The 5V rectifier winding on a radio power xfmr is rated usually 2A for a 5Y3 or 3A for a 5U4.
The 5V6 wants .6A per tube. So 4 of them is 2.4 A


this is something i have always wondered.

according to nj7p tube database, the 5V6gt is the same as the 6V6gt other than the filament voltage. it says "see 6v6gt for other characteristics".

since most (if not all) 6.3 volt tube sets are in parallel for the filaments, could a 1-2 ohm resistor be put on the filament to the 5v6 to make the 6.3v filament 5 volts ?

would one then get the same output/characteristics exactly like a 6v6 when using 5v6 on 6.3v with a filament dropping resistor ?

i have never tried it since i have a few hundred 6v6gt tubes to last the rest of my life and a generation or two after me.

i was just thinking about this the other day...

they aren't as expensive as the 6v6, but they aren't 2 dollar tubes either.

https://www.ebay.com/sch/i.html?_from=R ... w=5v6+tube

after writing the above, i found this:

https://www.thegearpage.net/board/index ... r.1950984/

this article says that even adding a filament dropping resistor will be an extra load on the power transformer. i did no research to verify anything in this article.


steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.
-Churchill


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sat 17, 2020 5:53 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5770
Location: 253 Blanche St. Plymouth, MI USA
Answer is YES, adding a dropping resistor to bring the 6v filament line down to 5V works well, and YES, its adding wasted heat to the system so you must have a transformer that is able to supply the extra total filament power that will be used.
The 5V6 pulls .6 A vs the 6V6 pulls .45 A. The 5V6 is actually designed for 4.7V but if you had a 5V xfmr thats plenty close and you could run them directly from that with no loss. But if you add a resistor to drop it down, you are dropping about 1.3v at .45A, thats a 2.9 ohm resistor (3 ohms is good here) dissipating .6 watts, so a 1 watt 3 ohm resistor per tube, not too much wasted in power, a well over spec'd power transformer would probably be OK with that.

_________________
Mark Oppat
Antique Audio
Plymouth, MI
http://www.oldradioparts.net


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sat 17, 2020 6:36 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22817
Location: Haledon, NJ, usa
Hey Dutch Rabbit:

Substituting a 5V6gt

For filaments... You can also use a 12uf non-polarized film cap ... (No heat produced)
Yes, a 12uf (dropper capacitor) will run one or more 5v6gt in series filaments @ 600ma.

At 60hz ... the 12uf capacitor's reactance will actually act as a 600ma current limiter.

https://www.digikey.com/en/products/det ... PT/4694505

If you start at the 120v primary side and put a 12uf 250v film cap in series with the 5v6 tube or two 5v6gt tubes in series.
The 12uf cap will only allow approx 600ma to the filament string of two 5v6gt tubes in series.

( Note: you can also add a 1-amp (or so) fuse in series and be sure to put a bleeder resistor of 56k across the 12uf cap)

If you want to test this on the bench first ... try feeding 120vAC through the 12uf cap to an 8 ohm 10 watt resistor( to represent the 5v6 tube filament resistance) ... put an AC amp meter in series with the resistor and also measure the AC voltage drop across the 8 ohm 10watt resistor..

BELOW:
From 122volts AC, ...you can see that I use a 10uf cap (C-3A) here to run two 6v6gt tubes in series @450ma
The 3.2uf cap, C-3-b supplies 150ma for the 12SL7gt.

Image

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Last edited by Pbpix on Oct Sat 17, 2020 8:18 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sat 17, 2020 7:46 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5770
Location: 253 Blanche St. Plymouth, MI USA
Peter, good pick on those 12uf caps... if you can run two 5V6 off of one, thats a good deal as the 5V6GT tubes are only about $5 NOS from some sources vs $25+++ for USA NOS 6V6GT

There are still some real deals doing this "Filament Fudging" if you know what you are doing. I save a lot doing it for certain types I will not reveal here.

_________________
Mark Oppat
Antique Audio
Plymouth, MI
http://www.oldradioparts.net


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sat 17, 2020 8:16 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22817
Location: Haledon, NJ, usa
oldradioparts wrote:
Peter, good pick on those 12uf caps... if you can run two 5V6 off of one, thats a good deal as the 5V6GT tubes are only about $5 NOS from some sources vs $25+++ for USA NOS 6V6GT

There are still some real deals doing this "Filament Fudging" if you know what you are doing. I save a lot doing it for certain types I will not reveal here.

Thanks... I love working with "dropper capacitors" ... such a great idea and low cost and no heat.
btw:
There are several other 12uf caps on Ebay for a few bucks + shipping
(but of course any lower cost smaller values in parallel works fine too ie 4uf +8uf or two 6uf caps etc.
https://www.ebay.com/itm/250V12UF-polye ... Sw1UdbhBLR

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sat 17, 2020 9:11 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 8678
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
oldradioparts wrote:
I save a lot doing it for certain types I will not reveal here.


Why won't you reveal it here?


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sun 18, 2020 2:43 am 
Member
User avatar

Joined: Sep Mon 16, 2013 2:42 am
Posts: 4227
Location: Tucson, Arizona U.S.A.
One problem with using capacitors like in the schematic above is that they give the circuit a very low power factor. This means that the transformer has to supply 450 mA for the 6V6s plus 150 mA for the 12SL7 plus the B+ current. That's 72 VA for the heaters in the capacitor circuit vs. 7.6 VA for connecting them to a 6.3 V transformer (and using a 6SL7). It works but it requires a MUCH larger transformer than would otherwise be required. Note that the schematic specifies a 100 VA transformer. This is why.

_________________
Jim Mueller


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sun 18, 2020 3:38 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22817
Location: Haledon, NJ, usa
Jim Mueller wrote:
One problem with using capacitors like in the schematic above is that they give the circuit a very low power factor. This means that the transformer has to supply 450 mA for the 6V6s plus 150 mA for the 12SL7 plus the B+ current. That's 72 VA for the heaters in the capacitor circuit vs. 7.6 VA for connecting them to a 6.3 V transformer (and using a 6SL7). It works but it requires a MUCH larger transformer than would otherwise be required. Note that the schematic specifies a 100 VA transformer. This is why.

Yes that's right Jim:
.. but I like using these "dropper caps" vs filament transformers for cost and mostly for space inside the chassis.

But .. being the "cavalier one" some might call me, I don't actually experience any space problems either way, ... because on my own amp here at home, I chose not to use any power transformers at all and because .. the entire amp is inside a wooden box-chassis.
But also ... for safety's sake, I make sure that I am drawing power through a GFCI AC source ..which, when tested, trips on as little as 5-ma of leakage current.
The end result allows me to have lots of space and to use very small wooden boxes for chassis.
In the last photo of the inside build, the lower box half shows the entire power supply doubler and filters on the left, with the fuse and dropper caps on the right top corner of that lower box half.

Amp Outside build:
http://pbpix.com/amp/se%2012sl7%206v6%20%20tubes.jpg

Amp Inside wiring:
http://pbpix.com/amp/se%2012sl7%20-%206 ... inside.jpg

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Last edited by Pbpix on Oct Sun 18, 2020 10:11 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sun 18, 2020 4:23 am 
Member
User avatar

Joined: May Sun 13, 2012 8:12 pm
Posts: 14537
Location: Central PA 16801
those are some good thoughts.

it seems to always be that "heater current" thing when trying to get by with a variant tube

it would be nice if the 6W6 and the 6Y6 could be made to work, but if they were able to do so, their price would not be as low as it is.

that all would be something cool to experiment with, but since i have an excellent pile of used and nos 6v6 tubes, i will just process it all in my head.

steve

_________________
You have enemies ? Good. That means you've stood up for something, sometime in your life.
-Churchill


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sun 18, 2020 8:46 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5770
Location: 253 Blanche St. Plymouth, MI USA
John Bartley wrote:
oldradioparts wrote:
I save a lot doing it for certain types I will not reveal here.


Why won't you reveal it here?



Once the guitar nuts and audiophools catch on the prices will skyrocket. Its a tube that is used in most of the German radios and many audio amps. Its the 8 V filament version, its a plug and play sub really.... works great.

_________________
Mark Oppat
Antique Audio
Plymouth, MI
http://www.oldradioparts.net


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Sun 18, 2020 9:49 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 22817
Location: Haledon, NJ, usa
oldradioparts wrote:
John Bartley wrote:
oldradioparts wrote:
I save a lot doing it for certain types I will not reveal here.


Why won't you reveal it here?



Once the guitar nuts and audiophools catch on the prices will skyrocket. Its a tube that is used in most of the German radios and many audio amps. Its the 8 V filament version, its a plug and play sub really.... works great.

Is this the pentode tube where the 6v sells for $16, ...and the 8v sells for $6 and the 10v sells for$5 at findatube.com

I believe that the price would not go up fast if the guitar musician guys know about it ... only because not many of them build their own or modify their beloved famous amp because:
1.) either they don't know how or
2.) more likely, they are afraid to vary from the original design... even for such a trivial change.
The reason then is that if they rewire it for 8 or 10 volt filaments... they are then not compatible with the 6v world anymore or some such thinking..
3.) Musicians of any note, are not penny-pincher type people. In fact a few more dollars for the tube is trivial to their overall total sound and whatever that all means to them.

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: Cheap 6V6GT Tubes
PostPosted: Oct Mon 19, 2020 12:57 am 
Member
User avatar

Joined: Sep Mon 16, 2013 2:42 am
Posts: 4227
Location: Tucson, Arizona U.S.A.
Pbpix wrote:
. the entire amp is inside a wooden box-chassis.

Amp Outside build:
http://pbpix.com/amp/se%2012sl7%206v6%20%20tubes.jpg

Amp Inside wiring:
http://pbpix.com/amp/se%2012sl7%20-%206 ... inside.jpg

Which brings up the obvious question: where do you get the nice boxes? I don't see much of that sort of thing at any store that I go to.

_________________
Jim Mueller


Top
 Profile  
 
Post New Topic Post Reply  [ 44 posts ]  Go to page Previous  1, 2, 3  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 8 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB