ferrograph reel to reel tube preamp

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Andybot

Well-known member
Joined
Sep 7, 2004
Messages
105
Hi,
I have a ferrograph tube reel to reel that I would like to try to convert to a
microphone preamp. I would like to get an idea of what can and should be done to make this a usable preamp. I have done a little tube work so have a basic idea of what to do but when it comes to things like trying to add phantom power, making the lines balanced, building a new power supply etc
i am a littl e lost.

Thx
 
Welcome to the club.

> a ferrograph tube reel to reel that I would like to try to convert to a microphone preamp.

I don't want to think about how many different recorders Ferrograph made.

> things like trying to add phantom power, making the lines balanced, building a new power supply etc

Use the existing power supply--- why not?

Unbalanced inputs become balanced with lo-Z/hi-Z transformers, which you can even find at Radio Shack (they are not bad: some oriental workshop turns out the same product for many makers).

Phantom is just a matter of finding 48V, and 2 resistors to the XLR side of the mike transformer.

Getting a proper Pro Line Out from a box made for hi-Z unbalanced hi-fi connections just isn't going to happen.... it would be easier to build an amp from scratch.
 
Some of the ferrographs have an unbalanced line out already. If you have twoinputs on the front, one for mic and one for line, then you can tap a signal out after the first gain stage by just using the 'line' input as an output.

Lots of information & manuals here

http://www.morphet.org.uk/ferro/
 
Playback and record you've got two outs, if you've got a monitor/headphone jack there's another out. Could be a mixer, could use one out as DI, etc. etc.
Stereo you've got four outs reproduce/record. Line in and a mic in (XLR on this?) you've got two ins. Like PRR says you've just got to twiddle the impedances w/xfrmers. Buy xfrmers you can use in another project; I eventually abandoned my similar plans for an Ampex 960, too noisy. I might return to it but if not I've got nice dual concentric pots and a great psu circuit to power about a dozen pre tubes and a funky little vu meter and a fantstic suitcase.
 
I was about to mention that the Ampex 960 is a great little tape deck when set up and working properly--but now that I look at your message again, it sounds like yours has already been disassembled :wink:
 
Thx for all the replies.
Its a series 2 or 3 reel to reel. I already tried taking a line out of an external speaker jack with a transformer on the input. To noisey. I suppose what im looking for are suggestions to reduce the noise floor. My preferance would be to build a pre from scratch that I could use in my studio but my budget says tinker and learn something .

Thx
 
[quote author="NewYorkDave"]I was about to mention that the Ampex 960 is a great little tape deck when set up and working properly--but now that I look at your message again, it sounds like yours has already been disassembled :wink:[/quote]

's'okay, I've got three more, two work great, and there's a 350-2 from Capitol Records here and a funky 300/3200; friend I got it from rebuilt the transport controls as 350 w/an edit button, completely refabbed the control box/panel, very nice transport. Has Inovonics electronics now but the plan is to marry it to the 350 channels--transport is stiffer and can take 14" reels, so I'm hoping for a good 15/30ips mixdown deck. The Capitol machine was modified at Capitol, a common mod there I guess: vu's were removed and put in their own 4u rack face plate (kinda like the 300 mono deck control panel but no level controls, just vu's,) and bias, repro and record calibration pots were moved to the vu holes. The holes are covered by black/white/black plastic squares, like the stuff they'd engrave your name on for your office door, y'know? One says "Capitol #31."
It works okay but's a ghastly damned site. Needs much much luv & affection.
 
[quote author="Andybot"]Thx for all the replies.
I already tried taking a line out of an external speaker jack with a transformer on the input. To noisey. I suppose what im looking for are suggestions to reduce the noise floor.

Thx[/quote]

If its got AC filament voltage, do the dc conversion thing with a bridge rectifier, whatever appropriate amperage, 25, 35 amps. That will quiet things down considerably.

[quote author="Andybot"]Thx for all the replies.
Its a series 2 or 3 reel to reel. I already tried taking a line out of an external speaker jack with a transformer on the input. To noisey. I suppose what im looking for are suggestions to reduce the noise floor. My preferance would be to build a pre from scratch that I could use in my studio but my budget says tinker and learn something .

Thx[/quote]

Series 2 schematic, you can get rid of the bias/erase tube, valve 6 tetrode. There's a little output xfrmr in there for an internal 15 ohm speaker, the speaker jack outputs at 2.3ohms. There's three pentodes, a dual triode and a tetrode, cool, very un-Ampex like. Specs indicate resistance Input 1 (mic?) is 1 meg and input 2 (radio?) is .5 meg. EQ is nested between valves 1&2; input 1 goes to grid on valve 2, input two goes to plate (?) on valve two. Stewart said:
If you have two inputs on the front, one for mic and one for line, then you can tap a signal out after the first gain stage by just using the 'line' input as an output.
Yeah, try that and tell us what it sounds like.
At a glance it looks like valve 1 is the first gain stage for playback head and also the record head, dependent on control switch. Valve 3 is the input tube for the onboard speaker amp, single ended, valve 4 is the power tube, tetrode, 2 &1/2 watts. What tubes are in there???

Controls are hard to read on the photo, looks like two knobs on the left are eq, and then one gain control knob. Nice knobs! You could yank that socket and put another pot there for output attenuation...I can't read what the jack below and just to the right of the gain control is, speaker out? Just wire it for DI out. Anyway, I'd wire it for two ins one out, a little mixer, one output xfrmr. You could use the amp for DI? One input balanced for mic, one switchable balanced mic/instrument (which could also be switched out of the preamp circuit to the di jack.) Use one half each valve 5 dual triode as input gain for the two pentodes. Give the transport to the nearest ferrograph fan and figure out how to save the part of the case that houses the electronics and maybe make a lid from the old lid. See if you can salvage that transformer thats in front of the grid on tube 1. Leave the EQ in there for input 1. RatShack unbalanced to balanced xfrmrs, like PRR said, makes it real easy. What color is the paint?

Interesting machine!

Hey, now I want one! :!:
 
I have a series 2. The line-out trick works OK, but the gain is not huge.

It does sound great as an amplifier though, and I actually use it maily as a guitar amp or effect on vocals. Plug the guitar into the mic input, set all the controls to max, and then mic up the internal speaker. Lots of fun.
:thumb:
 
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