SUPERMAGOO
Well-known member
all info or link about this tube it´s good for me.thanks! :thumb:
6386 need any info or link.
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CJ
Well-known member
SUPERMAGOO
Well-known member
ja ja ja ja!!!!! :grin: :grin: :grin:
i serch before in google.
or substitute info.
or 5670 info.
i serch before in google.
or substitute info.
or 5670 info.
http://frank.pocnet.net/sheets/142/6/6386.pdf
http://tdsl.duncanamps.com/
Rules as a source for tube data.
5670 is a dual sharp cutoff triode with the same basing as a 6386. I have come across renumbered 5670s sold as 6386s. Big bummer. The 6386 is remote cutoff, giving it the charachteristics we all love, and yeah, what Dave said.
The only other remote cutoff dual triode I've seen is the 6ES8/ECC189 that Pendulum seems to be using with good results. According to Greg, it sounds and responds very much like the 6386. I believe EAR uses PCC189s(different heater voltage) in their Fairchildesque limiters as well, and people seem to loooove those.
I may be deluding myself, but I think PRR had a post a bit back that went over some of the finer points of why one might want to use remote over sharp cutoff, or when you might not need to, far better than I would be able to (surprise surprise).
Rules as a source for tube data.
5670 is a dual sharp cutoff triode with the same basing as a 6386. I have come across renumbered 5670s sold as 6386s. Big bummer. The 6386 is remote cutoff, giving it the charachteristics we all love, and yeah, what Dave said.
The only other remote cutoff dual triode I've seen is the 6ES8/ECC189 that Pendulum seems to be using with good results. According to Greg, it sounds and responds very much like the 6386. I believe EAR uses PCC189s(different heater voltage) in their Fairchildesque limiters as well, and people seem to loooove those.
I may be deluding myself, but I think PRR had a post a bit back that went over some of the finer points of why one might want to use remote over sharp cutoff, or when you might not need to, far better than I would be able to (surprise surprise).
CJ
Well-known member
6BA6 also.
A few more, but I forget.
A few more, but I forget.
cannikin
Well-known member
you can buy them here http://www.tubedepot.com/
Not cheap, Just bought one for my Gates Sta-level Clone.
But this is the fun Part :shock: :shock:
Check this out............ :green: :green:
PURPOSE: To provide a replacement for the obsolete 6386 tubes in earlier units or convert later 5670 units to have the same limiting characteristics of the original 6386 for smoother operation.
METHOD: To install a converter board and surrounding modifications to enable usage of two 12BA6 or 6BA6 single pentodes wired in triode mode to take over the duties of a single envelope dual triode 6386 or 5670 (per channel).
:thumb:
I'm trying to obtain the schematic for the Mod.
Not cheap, Just bought one for my Gates Sta-level Clone.
But this is the fun Part :shock: :shock:
Check this out............ :green: :green:
PURPOSE: To provide a replacement for the obsolete 6386 tubes in earlier units or convert later 5670 units to have the same limiting characteristics of the original 6386 for smoother operation.
METHOD: To install a converter board and surrounding modifications to enable usage of two 12BA6 or 6BA6 single pentodes wired in triode mode to take over the duties of a single envelope dual triode 6386 or 5670 (per channel).
:thumb:
I'm trying to obtain the schematic for the Mod.
ciminosound
Well-known member
Seems like we've had this discussion many times. M*nley used the 5670 as the original replacement for the 6386 in their V-mu. Now they use the 12/6BA6 dual board mod. The 6ES8 has been used by several companys including the old Langevin "Level Line" unit. 6BC8 is another type found in Altec types.
rafafredd
Well-known member
There was a link recently to an Ebay auction where the seller wanted $100 bucks for info on a mod that uses some pentodes (suposedly not 6BA6) to sub the 6386. He said it gives better sound than the 6BA6 Munlay T-bar mod. So, I did a search for remote cutoff pentodes and found many tubes. So, maybe this guy found a better pentode to sub 6386s.
I may try some other types of pentodes other than the 6BA6 in my never ending construction of a varimu comp...
Does all the remote cutoff pentodes mantain their cutoff point when straped as a triode? What pentode tubes (wired as triodes) do you think might be worth checking out?
I may try some other types of pentodes other than the 6BA6 in my never ending construction of a varimu comp...
Does all the remote cutoff pentodes mantain their cutoff point when straped as a triode? What pentode tubes (wired as triodes) do you think might be worth checking out?
ciminosound
Well-known member
Does anyone know what this 12/6BA mod actually is??
Schemo maybe... :green:
Schemo maybe... :green:
> all info or link about this tube it´s good for me.
"ALL"? It is made of glass. It has pins. A girl named "Jane" sealed the bases.
Don't ever ask for "ALL" info. Nobody wants to wear their fingers out typing things you already know, or things you don't need to know.
And the 6386 is Not Magic!!!
It is just another remote-cutoff amplifier.
In a regular tube, to reduce gain a little, you have to reduce current a LOT.
In a limiter, that means that when you try for high signal to noise and high gain reduction, it runs out of current and distorts. Very badly.
A "remote-cutoff" tube is wound so the gain drops almost as fast as the current. In heavy gain reduction it still "starves" and distorts, but it is better than a regular tube.
Most tube limiters solved the problem with careful selection of limiting level (you have over 120dB of dynamic range available) and using a buffer amp after the vari-gain stage so only small current was needed in the vari-gain stage.
Most of these used resistance-coupling for lowest current loading. But that has problems with the common-mode voltage shift. Transformer coupling avoids that, but transformers are hard to wind to very high impedance (low current). Here we want a "big" remote-cutoff amplifier. 6BC8 is a pretty beefy remote-cutoff amplifier.
And then we have the Fairchild. It lacks a buffer amplifier: the vari-gain stage drives the load directly. Part of the compromise is fairly limited output level, much less than comparably sized RCA or GE broadcast limiters. (Broadcast limiters sometimes drive very long lines in very high RF fields, and need monster output; the Fairchild would be used in a recording room where huge levels were not needed.)
To get that crazy plan to work, Narma used the BIGGEST remote-cutoff tubes he could find. The 6386 is marginally "fatter" than the 6BC8. Also 6386 was a high-spec tube, consistent, well matched (remote cutoff tube were mostly used in radio/TV duty and not in push-pull connection). Even so, he had to use four 6386 in push-pull parallel to meet a modest output spec. It came together, for him, at that time, because 6386 were easy to get. I'm sure if he faced today's prices, he'd go for 6BC8 or ECC189 or even push-pull 6L6. (Don't laugh: the 6L6 is not quite as bent as a remote-cutoff amplifier, but significantly and deliberately bent. And Fender used 6L6 bias control for vari-gain tremulo in one of their amplifiers.)
The Fairchild has MANY other small design details that make it a superb audio path. Excellent transformers. HIGH power rectifier driver. Sidechain runs nonlinearly. Well choosen time constants.
> Does anyone know what this 12/6BA mod actually is??
No but it is quite obvious.
6BA6 is an "improved" (for radio) 6SK7. These two types were THE standard IF stage in AM radios in the US market. AM radio signals can vary from 50 microvolts to 500 millivolts, and an AM radio should bring any signal up to full output without overload or constant gain adjustment when tuning or when signals fade. This is where remote cutoff tubes started, and where they shine. (AM radio duty is really easier than audio limiter duty: S/N goals are lower, control voltage spectrum is not in the passband, AC/DC impedance ratio is higher, even-order distortion is a non-issue.)
Actually the bulk of radio production was in "AC-DC" radios using series-string heaters, which in a 5-tube radio with 35V rectifier and 50V output tube leaves about 12V each for RF, IF and detector, so the 12SK7 and 12BA6 are VERY common tubes.
12/6BA6 is pretty "beefy" (good for us) but very high gain (bad for line-level audio limiters). The 12/6SK7 is perhaps the better tube for audio, but is a bigger Octal, and fewer were produced, and even fewer survive.
One advantage of the twin-triodes is that the two halves -may- be well-matched, and we need good matching in audio limiters to reduce distortion and thump. You would think that two random single-tubes would not match as well as a twin-tube. However many twin-tubes are not well matched, so this may not matter if you can find single-tubes from the same factory and time.
If you are replacing a common remote-cutoff twin-triode with 6BA6: wire G2 to the Plate and strap the pins to the twin-triode socket the obvious way. This is more a mechanical puzzle than an electronics problem. With G2 defeated, the 6BA6 may actually be the "same" grid-cathode structure as the twin-triodes (factories did not like to keep too many jigs around). The Mu will be similar to any of the remote cutoff twin triodes, maybe a few dB shift in input threshold. If it isn't the "same" grid as the twin triode being replaced, the output level and calibration will shift somewhat.
If you are designing from scratch, pentode operation beats triode. Triode plate resistance variation fights the variable transconductance. A "conventionally" designed triode amplifier, with large plate resistor, won't change gain much until you really dump the grids negative and have lost a lot of bias current. Pentodes with any practical load start losing gain right away. And there is a trick of feeding G2 through a resistor which improves and linearizes the remote-cutoff effect, though if you take it too far you get a fairly soft GR curve.
"ALL"? It is made of glass. It has pins. A girl named "Jane" sealed the bases.
Don't ever ask for "ALL" info. Nobody wants to wear their fingers out typing things you already know, or things you don't need to know.
And the 6386 is Not Magic!!!
It is just another remote-cutoff amplifier.
In a regular tube, to reduce gain a little, you have to reduce current a LOT.
In a limiter, that means that when you try for high signal to noise and high gain reduction, it runs out of current and distorts. Very badly.
A "remote-cutoff" tube is wound so the gain drops almost as fast as the current. In heavy gain reduction it still "starves" and distorts, but it is better than a regular tube.
Most tube limiters solved the problem with careful selection of limiting level (you have over 120dB of dynamic range available) and using a buffer amp after the vari-gain stage so only small current was needed in the vari-gain stage.
Most of these used resistance-coupling for lowest current loading. But that has problems with the common-mode voltage shift. Transformer coupling avoids that, but transformers are hard to wind to very high impedance (low current). Here we want a "big" remote-cutoff amplifier. 6BC8 is a pretty beefy remote-cutoff amplifier.
And then we have the Fairchild. It lacks a buffer amplifier: the vari-gain stage drives the load directly. Part of the compromise is fairly limited output level, much less than comparably sized RCA or GE broadcast limiters. (Broadcast limiters sometimes drive very long lines in very high RF fields, and need monster output; the Fairchild would be used in a recording room where huge levels were not needed.)
To get that crazy plan to work, Narma used the BIGGEST remote-cutoff tubes he could find. The 6386 is marginally "fatter" than the 6BC8. Also 6386 was a high-spec tube, consistent, well matched (remote cutoff tube were mostly used in radio/TV duty and not in push-pull connection). Even so, he had to use four 6386 in push-pull parallel to meet a modest output spec. It came together, for him, at that time, because 6386 were easy to get. I'm sure if he faced today's prices, he'd go for 6BC8 or ECC189 or even push-pull 6L6. (Don't laugh: the 6L6 is not quite as bent as a remote-cutoff amplifier, but significantly and deliberately bent. And Fender used 6L6 bias control for vari-gain tremulo in one of their amplifiers.)
The Fairchild has MANY other small design details that make it a superb audio path. Excellent transformers. HIGH power rectifier driver. Sidechain runs nonlinearly. Well choosen time constants.
> Does anyone know what this 12/6BA mod actually is??
No but it is quite obvious.
6BA6 is an "improved" (for radio) 6SK7. These two types were THE standard IF stage in AM radios in the US market. AM radio signals can vary from 50 microvolts to 500 millivolts, and an AM radio should bring any signal up to full output without overload or constant gain adjustment when tuning or when signals fade. This is where remote cutoff tubes started, and where they shine. (AM radio duty is really easier than audio limiter duty: S/N goals are lower, control voltage spectrum is not in the passband, AC/DC impedance ratio is higher, even-order distortion is a non-issue.)
Actually the bulk of radio production was in "AC-DC" radios using series-string heaters, which in a 5-tube radio with 35V rectifier and 50V output tube leaves about 12V each for RF, IF and detector, so the 12SK7 and 12BA6 are VERY common tubes.
12/6BA6 is pretty "beefy" (good for us) but very high gain (bad for line-level audio limiters). The 12/6SK7 is perhaps the better tube for audio, but is a bigger Octal, and fewer were produced, and even fewer survive.
One advantage of the twin-triodes is that the two halves -may- be well-matched, and we need good matching in audio limiters to reduce distortion and thump. You would think that two random single-tubes would not match as well as a twin-tube. However many twin-tubes are not well matched, so this may not matter if you can find single-tubes from the same factory and time.
If you are replacing a common remote-cutoff twin-triode with 6BA6: wire G2 to the Plate and strap the pins to the twin-triode socket the obvious way. This is more a mechanical puzzle than an electronics problem. With G2 defeated, the 6BA6 may actually be the "same" grid-cathode structure as the twin-triodes (factories did not like to keep too many jigs around). The Mu will be similar to any of the remote cutoff twin triodes, maybe a few dB shift in input threshold. If it isn't the "same" grid as the twin triode being replaced, the output level and calibration will shift somewhat.
If you are designing from scratch, pentode operation beats triode. Triode plate resistance variation fights the variable transconductance. A "conventionally" designed triode amplifier, with large plate resistor, won't change gain much until you really dump the grids negative and have lost a lot of bias current. Pentodes with any practical load start losing gain right away. And there is a trick of feeding G2 through a resistor which improves and linearizes the remote-cutoff effect, though if you take it too far you get a fairly soft GR curve.
EmoRiot
Active member
Ebay has a guy selling "Plans for subbing 6386 triode in tube compressor limiter"
He says:
I have spent over two years developing and evaluating this. First of all it is NOT a copied circuit from a well known maker of the variable mu type of limiter. I have developed this very simple combination to sound exactly like the 6386...no lifeless low end. The gain reduction characteristics and the frequency response measure right up to the 6386....the gain reduction ability in some cases exceded the ability of the best example of the 6386 I have.
Which sounds promising, but then again he's charging 100 bucks for the plans and 2 tubes. Also, he says: Your purchase will entitle you to obtain additional tubes from me as the need arises. I will not disclose the tube type...dont ask!
To me it sounds like a bad deal that just might yield good results. But I wouldn't like being beholden to this guy for all my future tube purchases! :?
He says:
I have spent over two years developing and evaluating this. First of all it is NOT a copied circuit from a well known maker of the variable mu type of limiter. I have developed this very simple combination to sound exactly like the 6386...no lifeless low end. The gain reduction characteristics and the frequency response measure right up to the 6386....the gain reduction ability in some cases exceded the ability of the best example of the 6386 I have.
Which sounds promising, but then again he's charging 100 bucks for the plans and 2 tubes. Also, he says: Your purchase will entitle you to obtain additional tubes from me as the need arises. I will not disclose the tube type...dont ask!
To me it sounds like a bad deal that just might yield good results. But I wouldn't like being beholden to this guy for all my future tube purchases! :?
cannikin
Well-known member
Is there a way to Identify the tubes, through a series of tests?
We already discussed this here
http://www.groupdiy.com/index.php?topic=6795
You could buy 2 real 6386 for what he wants for his "cost effective" solution
adrianh
Well-known member
Yes but if we bought it it would be no proble to look at the tubes.
ID is easy.
Looks like a 6AU6 ????????????????????
ID is easy.
Looks like a 6AU6 ????????????????????
ciminosound
Well-known member
A lot of those little pentodes look alike. There is a version of the FAA limiter that uses 6AU6's.
http://www.waltzingbear.com/Schematics/Misc/FAA_CA-1589.htm
Like PRR said in his 12AU7 comp design, you can use a lot of different types for small amounts of compression. It's the distortion characteristics that matter with larger amounts of limiting. (just paraphrasing there PRR :thumb: )
http://www.waltzingbear.com/Schematics/Misc/FAA_CA-1589.htm
Like PRR said in his 12AU7 comp design, you can use a lot of different types for small amounts of compression. It's the distortion characteristics that matter with larger amounts of limiting. (just paraphrasing there PRR :thumb: )
CJ
Well-known member
Have to do a load line .
Or plug one into a 670 to see if GR is the same.
Or plug one into a 670 to see if GR is the same.
SUPERMAGOO
Well-known member
i need hard and good compression...
