InputVu Meter on tube preamp

[pstcho]

Hello everybody, i would like to add an input VU Meter to a tube preamp ( Ridge farm gas cooker )

Is there any advice you could give me ?

i am pretty ok with DIY , i make a load of stuff like pedals, tube amps, the classic G9, Gssl bus comp , G1176 and other kits from here and there, just dont have much electronic knowledge

thanks a lot

 

[ruffrecords]

I suspect you mean an output VU meter. The signal level at the mic input is so low it would not even twitch the needle of a VU meter. The normal place to add it would be right across the output. Probably best to use a Buffered types so it does not add distortion to the output.

Cheeers

Ian

 

[pstcho]

thanks for your reply

Output is easy to add and is not really needed cause of the vu metrer of the converter or DAW

i would like  one for the input in order to be sure i dont clip the input tube of the preamp

 

[ruffrecords]

It is very difficult to know when this device is going to clip. Do you have a schematic?

Cheers

Ian

 

[pucho812]

The ridge farm gabs cooker is a two channel all tube path mic pre...

I have seen inside them before, it's all tube caps resistors and transformers. Linear power supply, nothing complex but they sound really good.  The name gas cooker comes from the knobs used which are from a gas stove.

I am not sure about the original question, I am trying to figure out how one can clip the input of a mic pre  with a microphone?

Essentially the front is typical, standard bit o kit few switches of phantom and what not following by a mic input transformer,  which outputs to the first valve stage,

 

[ruffrecords]

The ridge farm gabs cooker is a two channel all tube path mic pre...

I have seen inside them before, it's all tube caps resistors and transformers. Linear power supply, nothing complex but they sound really good.  The name gas cooker comes from the knobs used which are from a gas stove.

I am not sure about the original question, I am trying to figure out how one can clip the input of a mic pre  with a microphone?

Essentially the front is typical, standard bit o kit few switches of phantom and what not following by a mic input transformer,  which outputs to the first valve stage,

Do you remember how many transformers you saw or how many and what type of tubes it uses?

The spec seems to say the first stage has a gain of 30x and the output stage a gain of 3x . Part of the problem is we do not know the ratio of the input transformer. To be honest I am not convinced there is one. Although it is called a mic pre on the front panel, if you read the ridge farms applications blurb it never mentions connecting a mic to it. It suggests using it on instruments or as an insert.

It also says it has high voltage circuitry and you can get tube tone by over driving the output stage. The implication is it has only a HI-Z input, no input transformer and the first stage has a gain of 30dB or 10dB (with the pad engaged. Given the high voltage circuit the first stage can probably output +30dBu before clipping. Even with no pad engaged that implies an input of 0dBu can be tolerated. With the 20dB pad engaged it will probably need a +20dBu input to get any where near clipping.

Cheers

Ian

 

[ruffrecords]

I found this pic of the guts on that other site. Looks like four audio transformers (Sowter??) so there are input transformers. The post say the three tubes are all 12AX7. One for each output and one shared. Still puzzled. XLRs on the back must be balanced outs. Only inout is jack (TRS?) on front. The unbalanced pre fader output must be the one labelled AMP on the front panel. Where are the main unbalanced out - under the XLRs where I can;t see?

Strange device.

Cheers

ian

 

[pstcho]

to reply as good as i can with all the questions:

yes it is pretty easy to distort with just a normal scream ( without the pad ) it is pretty surprising

it doesnt sound bad cause the preamp really polishes the distortion in a very sweet fashion ( it is awesome ) dont need any compressor after hahaha,  but sometimes it is annoying

there are input and output transformers

3  12x7

both channels react the exact same way

there is balances inputs and outputs and unbal in and out

the gain is huuuuuuuuuge

i use a Shure KSM44 most of the time inside

anyway it can be much from any weird setting cause there is only gain control phantom power pad and ground lift

i compared with a second unit a friend owns and there is the same exact behavior

i believe the gain control is used between 2 tubes cause even the gain full the output level is still good

 

[emrr]

You'd want an extended range meter, and a peak one at that, not a VU.  You would need to calibrate it to match the desired input distortion level, which you'd need to determine independently.  Essentially you'd be designing a parallel fixed gain bridging preamp to drive a peak meter calibrated to your needs. 

Or just use an input pad when you get fuzz, that's the truth with every transformer coupled tube preamp.  I've never seen one that doesn't clip with condenser mics, also your average dynamic mic with loud sources. 

 

[pstcho]

so it is normal   i have this preamp since 10 years and also used the PAD but now i wanted to find a more accurate solution

alright so i guess i will just not risk anything and leave it like that

 

[pucho812]

The gas cooker newer version with mic pre

http://medias.audiofanzine.com/images/normal/ridge-farm-the-gas-cooker-746981.jpg|

http://medias.audiofanzine.com/images/normal/ridge-farm-the-gas-cooker-528197.jpg

Older version was purely a tube DI
http://medias.audiofanzine.com/images/normal/ridge-farm-the-gas-cooker-208527.jpg
http://medias.audiofanzine.com/images/normal/ridge-farm-the-gas-cooker-87014.jpg

I found this pic of the guts on that other site. Looks like four audio transformers (Sowter??) so there are input transformers. The post say the three tubes are all 12AX7. One for each output and one shared. Still puzzled. XLRs on the back must be balanced outs. Only inout is jack (TRS?) on front. The unbalanced pre fader output must be the one labelled AMP on the front panel. Where are the main unbalanced out - under the XLRs where I can;t see?

Strange device.

Cheers

ian

I can confirm the sowter transformers.  The XLR jacks on the rear are for the mic inputs. 

 

[pstcho]

yeah i was talking about the mic preamp version