cannikin
Well-known member
Slowly been building this puppy.. really exciting.
Thanks NewYorkD! you Rock!
Thanks NewYorkD! you Rock!
One-Bottle Preamp
- Thread starter NewYorkDave
- Start date
Help Support GroupDIY Audio Forum:
My local electronics shop is out of 12 av7 but says that 5965(which they have) is a cross-reference. I checked out the datasheets & they seem similar, but I don't know enough to know if they're similar enough. Any thoughts?
Tom
Tom
ciminosound
Well-known member
5965 and AV7 are close and are sold as subs for each other by most tube dealers.
http://www.nj7p.org/Tube1.php?tube=5965A
I can't remember where I found this one the web and take no credit for it's makeup. Just wanna share.
:grin:
http://groupdiy.twin-x.com/displayimage.php?album=lastup&cat=0&pos=0
http://www.nj7p.org/Tube1.php?tube=5965A
I can't remember where I found this one the web and take no credit for it's makeup. Just wanna share.
:grin:
http://groupdiy.twin-x.com/displayimage.php?album=lastup&cat=0&pos=0
pstamler
Well-known member
At least if you go by the RCA tube manual, the 5965 and the 12AV7 aren't all that close. It's hard to tell without curves, but the Class A Amplifier tables give rather different numbers. The 5965 is designed for switching, not audio -- basically a computer tube.
Peace,
Paul
Peace,
Paul
ciminosound
Well-known member
The 5965 and 5965A is listed as a sub in some books for the AV7, haven't looked too closely myself to see how close of a sub. Audiophile types have adopted it as a direct replacement. Some sites claim it's a computer rated AV7, including more "trusted" ones. In my stash of these I may have some that are marked as both by the manufacturer. (Not that that means anything with some of the remarking that's happened, sheesh!)
As with any tube substitution, your mileage may vary.
That brings up the whole computer tube in audio discussion. The 6414 is listed as a computer tube for switching but the M*nley company uses them in their WCF outputs. Sould we start a thread in the Brewery on this topic?
This is fun:
http://www.vacuumtubesinc.com/hos.html
As with any tube substitution, your mileage may vary.
That brings up the whole computer tube in audio discussion. The 6414 is listed as a computer tube for switching but the M*nley company uses them in their WCF outputs. Sould we start a thread in the Brewery on this topic?
This is fun:
http://www.vacuumtubesinc.com/hos.html
tk@halmi
Well-known member
Some computer tubes are now worshipped by Audiophiles like many red base RCA tubes.
Anyhow, the 12AV7 has two major characteristics that the 5965 comes short of:
1. The 12AV7 can handle about twice the plate current of the 5965
2. The plate resistance is of the 12AV7 is 30% less than the 5965.
In the case of Dave's preamp, the 5965 is not a good sub because the design relies on the 12AV7's driving capability. In other applications it might be just fine. It all depends on the circuit.
Tamas
Anyhow, the 12AV7 has two major characteristics that the 5965 comes short of:
1. The 12AV7 can handle about twice the plate current of the 5965
2. The plate resistance is of the 12AV7 is 30% less than the 5965.
In the case of Dave's preamp, the 5965 is not a good sub because the design relies on the 12AV7's driving capability. In other applications it might be just fine. It all depends on the circuit.
Tamas
cannikin
Well-known member
Hey Guys
I'm building both of NYD's designs (one Bottle and LineAmpE in the drawing board). I'm a little confused between the 2 threads due to the similarities and CJ's project threw a wrench in the works :grin:. I just want to verify my parts, that are collecting dust on the shelf, will work for the One Bottle.
Input: UTC A-11
Output: Cinemag CMOB-2H 1:1 (this one I'm not sure about)
power: 125 V, 15 mA
much thanks
I'm building both of NYD's designs (one Bottle and LineAmpE in the drawing board). I'm a little confused between the 2 threads due to the similarities and CJ's project threw a wrench in the works :grin:. I just want to verify my parts, that are collecting dust on the shelf, will work for the One Bottle.
Input: UTC A-11
Output: Cinemag CMOB-2H 1:1 (this one I'm not sure about)
power: 125 V, 15 mA
much thanks
ciminosound
Well-known member
Excellent analysis of the circuit and tube characteristics tk@halmi. Was going to look at the details myself this afternoon but you already have.
:sam:
:sam:
NewYorkDave
Well-known member
Here are some detailed datasheets for the two tube types if you'd like to compare. I haven't studied the differences closely yet, myself, so I can't comment on whether or not the 5965 would work well in the One-Bottle.
12AV7
5965
(Datasheets courtesy of the magnificent "Frank's Tube Pages").
Just glancing at the datasheets and the plate curves, the tubes are obviously not the same but the curves are not terribly dissimilar. The "typical operating conditions" given in that chart linked above are not really useful for comparing these tube types because they're not identical conditions! For instance, the conditions for the AV7 are given at 18mA plate current, but only about 8mA for the 5965. Of COURSE the plate resistance for the AV7 comes out lower, the Gm higher. You really have to look at the datasheets and the curves.
Really, if a 5965 is all you have handy, it's close enough to try out--you won't blow anything up. If you don't like the results, find a 12AV7. Simple...
The slight difference in max ratings for plate dissipation is not really a concern because the One-Bottle isn't working near the max rating of either type. (Tamas, the Ia column on that chart refers to the plate current at which those "typical operating conditions" are given, not the design-center maximums).
David, the input transformer you have is fine for either circuit, but the 1:1 output transformer isn't. The One-Bottle requires a 4:1 output xfmr; "Line Amp E" can use a 2:1 or higher ratio output xfmr.
Your power transformer will work (with a voltage doubler) for the One-Bottle, but its rated current is too low for "Line Amp E."
You mentioned something in your PM about using the preamp as a DI. Here are some input/output options for the One-Bottle that I posted earlier. They would also work for "Line Amp E."
PDF
12AV7
5965
(Datasheets courtesy of the magnificent "Frank's Tube Pages").
Just glancing at the datasheets and the plate curves, the tubes are obviously not the same but the curves are not terribly dissimilar. The "typical operating conditions" given in that chart linked above are not really useful for comparing these tube types because they're not identical conditions! For instance, the conditions for the AV7 are given at 18mA plate current, but only about 8mA for the 5965. Of COURSE the plate resistance for the AV7 comes out lower, the Gm higher. You really have to look at the datasheets and the curves.
Really, if a 5965 is all you have handy, it's close enough to try out--you won't blow anything up. If you don't like the results, find a 12AV7. Simple...
The slight difference in max ratings for plate dissipation is not really a concern because the One-Bottle isn't working near the max rating of either type. (Tamas, the Ia column on that chart refers to the plate current at which those "typical operating conditions" are given, not the design-center maximums).
David, the input transformer you have is fine for either circuit, but the 1:1 output transformer isn't. The One-Bottle requires a 4:1 output xfmr; "Line Amp E" can use a 2:1 or higher ratio output xfmr.
Your power transformer will work (with a voltage doubler) for the One-Bottle, but its rated current is too low for "Line Amp E."
You mentioned something in your PM about using the preamp as a DI. Here are some input/output options for the One-Bottle that I posted earlier. They would also work for "Line Amp E."
tk@halmi
Well-known member
I am just thinking out loud so don't kick me in the shorts yet. A useful mod to Dave's one bottle amp may be adding a MOSFET follower on the output, still included in the feedback loop, to increase driving capability for use with a 2:1 transformer on the output, AND keeping it a one bottle design. The IRF710 from International Rectifier has as low of a gate capacitance as it gets with those beasts, and in the follower configuration it matters less. Naturally, the HV power supplies would have to be able to provide whatever current you set the follower to...
NewYorkDave
Well-known member
Yuck. Count me out.
We could replace the input transformer with an IC, too, or replace the plate resistors with BJT current sources--but that's also going against the whole minimalist "one tube, no bullshit" concept of the circuit.
Unless you have reason to believe the output capability is not adequate, you're talking about a solution for a problem that might not exist.
We could replace the input transformer with an IC, too, or replace the plate resistors with BJT current sources--but that's also going against the whole minimalist "one tube, no bullshit" concept of the circuit.
Unless you have reason to believe the output capability is not adequate, you're talking about a solution for a problem that might not exist.
tk@halmi
Well-known member
I see. You are one of them open minded ones. It is really not going against anything as far as I am concerned. LOL.
Wait a minute, isn't you line amp doing the same with a tube follower?
Wait a minute, isn't you line amp doing the same with a tube follower?
skipwave
Well-known member
[quote author="NewYorkDave"]"one tube, no bullshit"[/quote]
I like the way you think Dave. I would be happy if I never had to solder another IC in my life.:evil: That's an impossibility, but one can dream.
Anyway, I'm going to have this built over the weekend. It would have been cool for the 60's-style rock band I recorded last weekend, but at least I can still try it for makeup gain with my passive summing box when I mix it. :thumb:
I like the way you think Dave. I would be happy if I never had to solder another IC in my life.:evil: That's an impossibility, but one can dream.
Anyway, I'm going to have this built over the weekend. It would have been cool for the 60's-style rock band I recorded last weekend, but at least I can still try it for makeup gain with my passive summing box when I mix it. :thumb:
Svart
Well-known member
CJ pre: I was talking to a old time tube guy the other day and got on the subject of the single bottle preamp and he was really excited to hear about it! I talked to him about attenuation schemes and he mentioned putting a rheostat between the input trafo secondary and the grid of the 417 to cut gain, also mentioning to make sure that the value of the pot was sufficiently large. 100k should do it he claimed. I have a few 100k logs laying around and will give it a try and neither he nor I can think of any reason to NOT try it.. can you guys?
also, I would like to eventually put an output attenuator if i can ever figure out how to do a switching attenuator so that I can saturate the tube and the trafo for coolness factor.. any ideas why not?
also, I would like to eventually put an output attenuator if i can ever figure out how to do a switching attenuator so that I can saturate the tube and the trafo for coolness factor.. any ideas why not?
NewYorkDave
Well-known member
It's generally a bad idea (from a S/N perspective) to attenuate a mic signal before the first stage of amplification, unless the signal is already hot enough to overload the input stage.
If you do insert an attenuator between the input xfmr and the grid, as a "trim" for hotter signals, wire it up as a pot, not a rheostat.
As for an output level control, if the input impedance of the following equipment is high enough, why not just use a pot on the output?
If you do insert an attenuator between the input xfmr and the grid, as a "trim" for hotter signals, wire it up as a pot, not a rheostat.
As for an output level control, if the input impedance of the following equipment is high enough, why not just use a pot on the output?
Svart
Well-known member
it's a balanced out via transformer. I could insert the pot before the output trafo but I figured that it would screw with the impedance for output trafo.
Ok I will give it a try as a pot, not a rheostat, but am now digesting your lesson from the other thread and working on my switched attenuator.
Ok I will give it a try as a pot, not a rheostat, but am now digesting your lesson from the other thread and working on my switched attenuator.
skipwave
Well-known member
I've almost got my NYD One-Bottle pres built. They would have been done last night if I hadn't forgotten how to wire the heaters for 12.6VDC. I re-learned this morning with a quick search of the board. :thumb:
Speaking of input attenuation, I'm planning on using the Hampt0ne after-the-input-tx-pad, as shown in the jfet pre article:
http://home.comcast.net/~markfuksman/hamptone.jpg
I'm using Sescom MI-70 input TX, which aren't going to saturate easily, so I really like the idea of putting the pad after them. Hit those babies hard.:twisted:
Thoughts?
Speaking of input attenuation, I'm planning on using the Hampt0ne after-the-input-tx-pad, as shown in the jfet pre article:
http://home.comcast.net/~markfuksman/hamptone.jpg
I'm using Sescom MI-70 input TX, which aren't going to saturate easily, so I really like the idea of putting the pad after them. Hit those babies hard.:twisted:
Thoughts?
Hmmm, I wonder if a tapped grid choke has ever been used for input attenuation? Would have to be many henries, and could not go to far down the winding as DCR would get small, but s/n ratio would be good.
Brown Note
Well-known member
...so I've read every page of this thread, and I still have one question:
How do the values of the input xformer effect the values of the compensation network on the 12AV7 pre? A mathematical solution would really help me out here.
I'll probably use one of the Cinemag CMII-10 trafos for this project.
How do the values of the input xformer effect the values of the compensation network on the 12AV7 pre? A mathematical solution would really help me out here.
I'll probably use one of the Cinemag CMII-10 trafos for this project.
skipwave
Well-known member
[quote author="Brown Note"]How do the values of the input xformer effect the values of the compensation network on the 12AV7 pre? A mathematical solution would really help me out here.[/quote]
Too many variables for a single equation. Only the transformer manufacturer knows (or claims to know) what is needed. Check the datasheet for the tx in question, or be lazy like me and just see how it sounds without compensation. You can always add it, if needed.
Edited for spelling.
Too many variables for a single equation. Only the transformer manufacturer knows (or claims to know) what is needed. Check the datasheet for the tx in question, or be lazy like me and just see how it sounds without compensation. You can always add it, if needed.
Edited for spelling.
