Vacuum Tube Neve?

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CJ

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I was reading a post over at the Terry Manning place where he talked about a vacuum tube preamp based on the classic Neve circuit.

How would you go about replacing the transistors with tubes ?

Sound's like an interesting project.

Thanks!

cj
 
That is so weird!
I was in the shower yesterday, and a random thought popped in my head. A neve circuit with tubes, but then I quickly responded with, why? I'd be very interested in seeing how one would do it though.
 
You're not talking about the actual tube Neve circuit, right? You're talking about the classic transistor one reworked for tubes?

Because somewhere I have a schematic of an actual early Neve tube circuit, but probably everyone knows that already...
 
This was posted by Terry at the forum. Lenny Kravitz thread:

"
I like the API mic pre's a lot (also the BAE 312 one) and will use those for guitar, but I usually choose first my own custom made Lucas mic pre for guitar. It is based on the Neve original 1073 design (wow, that's a new and novel idea!), but tubes are employed instead of discreet transistors. This gives me the "grain" often associated with a Neve, but also a tube "warmth" (boy, I really hate using this ambiguous, non-specific terminology, but what else is there?) The Lucas has the extra gain stage, but I have found that I don't like that too much, so if the source needs more amplification than the 45 dB of the Lucas' first stage, I will go to something else. I also have a Summit tube mic pre from about '89 or '90 that I have found works well on guitar. It overloads nicely."
 
Holy shit!!! How the hell would you replace BJTs with tubes?! Can you say impedance difference? How about current gain instead of voltage gain? (Not sure I phrased that properly but it's a very different operating principle between the two) And what about the input transformer loading? I can imagine changing a tube circuit to FET, but BJT to tube? WOW!
 
The 1072 microphone pre is a 3 tran setup. Now lets think. The G9, manly I believe and maybe a few more seem to be two gain stages with a feedback loop. The CF are used after the gain and to feed the feedback loop.

The three transistor stage is NPN two transistors for gain and a EF with feedback.

Not that much different from a concept of a design

The headroom is going to be different because of the B+ voltages. So for the same gain and same input level the transistor will be closer to clipping and have higher distortion. I thought this is what people liked about the older neve circuits the simple gain design and how it overloads in a nice manner because of the simple gain design.

The ouput is a two gain stage SE amp. The tube RCA and other preamps have SE outputs.

A tube version would not be a neve but more of a standard tube preamp I would believe.

When you look at the transistor books from the 60's and 70's you will find circuits like the neve 3 transistor stage.
 
Dave,

I spent a little time last night looking for the schematic so I could scan it and post it, but I moved into my new space a few months back and now I have trouble finding things sometimes.

:mad:

I was surprised it wasn't in my filing cabinet along with the other goodies, but I should find it. I'll post it when I find it.

-E.
 
[quote author="pucho812"]Maybe he is refering to the rare Rupert Neve designed tube console?

pictured here
http://socalproaudio.com/console0004.html[/quote]

I got to poke around that console and hear it. Sounded quite usable. It's been extensively modified over the years. I recall it started out as a 3 buss, and got converted to stereo along the way. Originally 4 into 1, 3 into 1 and 3 into 1 with a mono out. So, finding the original schematic may be impossible at this point. I started comparing the supplied schematic with the console, and it's different. I got part way through reverse engineering it, but never finished. I would be killed by the owner if I released the info, by the way.
 
[quote author="electronaut"]Dave,

I spent a little time last night looking for the schematic so I could scan it and post it, but I moved into my new space a few months back and now I have trouble finding things sometimes.

:mad:

I was surprised it wasn't in my filing cabinet along with the other goodies, but I should find it. I'll post it when I find it.

-E.[/quote]
Hah.

Can't resist an off-topic digression:

Try moving from a 2600 sq ft office/highbay where you had all of your stuff in filing cabinets and bookshelves, plus your lab, into your 770 sq ft apartment with the overrun in a 10 x 30 storage space.

But, the monthly nut is about 1/3 of what it was, so it makes a certain amount of sense.
 
Heh, well it's not so much a pre as just a crossover/EQ line level processor, and it is still not done. But I've committed to providing a schematic to the layout guy by the end of June.

The tube wiring will be mostly point-to-point. There are some sand-state assists for things like current sources that will be on PCB. The low frequency channels will use some JFET input DOA's of a new design

I did find that the 6H30 is not near as microphonic as the 6C45, which was a relief.
 
Since you are already off topic, what do you know about the "Neve V0 console"

It's listed here: http://www.sundlaugin.com/ in the gear section and there are some pics of it in the pic section.. That's Sigur-Ros's studio by the way.

cheers,
hejsan
 
Ooh, Sigur Ros....lovely stuff! I have () or whatever it's called--hard to describe, but great to hear! Reminds me to put more of their Cds on my "to buy" list. Uh, now what were we talking about :roll:

A P
 
[quote author="AnalogPackrat"]..Uh, now what were we talking about :roll: [/quote]
Well, it's CJ's own fault...
[quote author="CJ"]blah blah.. don't worry, anything goes in my threads..blahbla..[/quote]
(That's only an approximate quote) :green:
 
[quote author="Family Hoof"]Holy shit!!! How the hell would you replace BJTs with tubes?! Can you say impedance difference? How about current gain instead of voltage gain? (Not sure I phrased that properly but it's a very different operating principle between the two) And what about the input transformer loading? I can imagine changing a tube circuit to FET, but BJT to tube? WOW![/quote]

Well, maybe if you just lift the topology, not the exact circuitry.
NYDave mentioned something about it in this thread:
http://www.groupdiy.com/index.php?topic=2074&highlight=ring+three

Here is the picture he linked:
http://electronicdave.myhosting.net/miscimages/ringofthree2.gif
Now look at this:
http://members.nuvox.net/~zt.robgrow/circuits/neve/neveba283.html
The topology of the preamp section of the 283 is pretty similar really.
 

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