Alternative to JLM VU buffer Boards

[Electrobumps]

Hi

I want a couple of VU meters for my mix bus. I have been looking at the JLM VU buffers. They look like a good option and have seen they come well recommend on forums. Simple to configure between rectified and non rectified meters.

Minimum spend of 270Aud to the UK on the JLM website, so not worth ordering a couple of boards. Does anyone know of a similar offering.

Thanks

 

[sahib]

I have these Sifam AL29 complete with drivers. Also have Tascam again with drivers. Plug and play. Based in Glasgow. Please PM if they are of interest.

 

[grapyofire]

Nice. I was looking at JLM VU buffers too.

 

[grapyofire]

I have these Sifam AL29 complete with drivers. Also have Tascam again with drivers. Plug and play. Based in Glasgow. Please PM if they are of interest.

Would you ship to US or GB only?

 

[sahib]

I am happy to ship to US (or anywhere).

Please let me know which one are you looking for and the quantity.

 

[Newmarket]

Hi

I want a couple of VU meters for my mix bus. I have been looking at the JLM VU buffers. They look like a good option and have seen they come well recommend on forums. Simple to configure between rectified and non rectified meters.

Minimum spend of 270Aud to the UK on the JLM website, so not worth ordering a couple of boards. Does anyone know of a similar offering.

Thankse

Have you considered making some of your own. Circuit is simple enough to use stripboard.

 

[Electrobumps]

Have you considered making some of your own. Circuit is simple enough to use stripboard

Time is not on my side to fully DIY, it will just never get done. Thanks for the input a good circuit to have on the forum.

 

[Newmarket]

Time is not on my side to fully DIY, it will just never get done. Thanks for the input a good circuit to have on the forum.

Fair Enough

 

[MidnightArrakis]

Have you considered making some of your own. Circuit is simple enough to use stripboard.

View attachment 83366

I am assuming that this circuit is - NOT - the same one as shown in Sahib's photo of a PCB, correct? I ask because his photo shows a "TR1" and a "TR2" which are not in your schematic. (NOTE: I am assuming that the term "TR" is a European designation for a transistor, whereas here in the U.S. we use "Q").

Does anyone have a schematic of the circuit shown in Sahib's PCB? I can see that it would be easy enough to "Reverse-Engineer" and trace out.

>> Electrobumps: I could design and build a couple of small PCBs for your VU meters -- IF -- you are willing to cover all of the costs (PCB fabrication, parts cost, mailing to the UK, etc.) to have them made. This ain't hard at all to do, but it does involve some financial costs and I am unwilling to have PCBs made, buy electronic parts for someone else and pay for everything out of my own pocket!!! So.....if you want this and can cover it, I'll get them made for you!!! I am attaching a PDF file that will show you some of the electronic equipment I have designed so you can determine if I am capable of doing this little project for you. I am also attaching a PDF file that shows some PCBs that I have personally designed, so you can check them out as well.

VU meter driver circuits are always a good thing to have around, you know!!!

/

 

[Newmarket]

For clarity I took that schematic image from
http://diy-tubes.com/image/data/manuals/vu-buffer-1.2-en.pdf

Sahib's pcb is clearly not derived from it and is not a JLM pcb assembly.

 

[ruffrecords]

I designed a VU meter buffer board for may last tube mixer project. It operates from the 12V heater suppl (but will happily operate from +15V or more)y. It uses a single TL072. The output circuit is very similar to the JLM but the input is transformer balanced so it is fully floating. Don't panic, it uses a couple of little £5 transformers so it won't break the bank. I am happy to donate a spare PCB to your project if you wish.

Cheers

Ian

 

[MidnightArrakis]

I designed a VU meter buffer board for may last tube mixer project. It operates from the 12V heater suppl (but will happily operate from +15V or more)y. It uses a single TL072. The output circuit is very similar to the JLM but the input is transformer balanced so it is fully floating. Don't panic, it uses a couple of little £5 transformers so it won't break the bank. I am happy to donate a spare PCB to your project if you wish.

Cheers

Ian

Interesting!!! Is there a schematic available for this VU Meter buffer amplifier? THANKS!!!

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[sahib]

For clarity I took that schematic image from
http://diy-tubes.com/image/data/manuals/vu-buffer-1.2-en.pdf

Sahib's pcb is clearly not derived from it and is not a JLM pcb assembly.

It is Soundcraft's original PCB. It uses TL072 and is a differential input with two transistor peak detector. As it is their production unit I do not feel it would be appropriate for me to draw the circuitry and publish it for cloning.

 

[ruffrecords]

Interesting!!! Is there a schematic available for this VU Meter buffer amplifier? THANKS!!!

/

Attached is a copy of the page from my day book when I designed it. It basically starts with the JLM circuit but alters the front end for use with a transformer. So the bias circuit at the top from the JLM is used along with the transformer input circuit at the bottom. I have also attached a pic of the finished PCB. The transformer is a TRIAD TY-141P.

Cheers

Ian

 

[Jen]

It is Soundcraft's original PCB. It uses TL072 and is a differential input with two transistor peak detector. As it is their production unit I do not feel it would be appropriate for me to draw the circuitry and publish it for cloning.

We can all go to Soundcraft or other schematic repositories and download full schematics and service manuals for their products.. they are in public access, no private restricted use. I got all the manuals for my Soundcraft equipment, purchased 2nd hand, free of charge.

 

[MidnightArrakis]

Attached is a copy of the page from my day book when I designed it. It basically starts with the JLM circuit but alters the front end for use with a transformer. So the bias circuit at the top from the JLM is used along with the transformer input circuit at the bottom. I have also attached a pic of the finished PCB. The transformer is a TRIAD TY-141P.

Cheers

Ian

THANKS!!! I saw in your hand-drawn schematic that it appears as though there are two versions, one with and one without a transformer. And, it also seems as though that both versions accept a - balanced - line input. Is this correct?

Is there any preference for one over the other, other than the version without a transformer would be less expensive. Is the transformer version preferred because of its isolation characteristics and also possibly its impedance and/or loading characteristics? I am - not - a circuit designer, so all of the detailed technical reasons are beyond me. However, I happen to do a pretty good job when it comes to designing and building electronic equipment.

Attached is a PDF file of your - transformerless - version as I have captured using my CAD-design software (Sorry!!! I don't use KiCAD, but my program will import KiCAD files). I know that there are some errors in there because I either couldn't decipher what was written in your schematic or I just didn't see the associated information. As an example, the diodes going to the VU-meter are probably the wrong type, but their "type" were the only ones that I saw within your schematic. Any and all comments are most welcome!!!

Another item I wasn't quite sure of was the use of - V/2. I am guessing that this is 1/2 of the V+ voltage and is used as a "reference" voltage, correct? If the TL072 is powered by a 12VDC supply, the circuit shown that derives the - V/2 - voltage is still necessary?

Which version of your schematic is preferred overall? That's all that I am really interested in. You will see that the schematic is a - stereo - version of yours.

You will see on the audio-input that my schematic shows a NEUTRIK "Combo-Jack" connector. I figured when working with line-level signals that that would be the best choice for an audio connector. Any comments?

And, finally...should you have any circuit tweaks, modifications, suggestions or updates, I would be interested in reading what you have to offer!!! THANKS!!!

/

 

[ruffrecords]

Just to be clear, the top circuit IS the JLM circuit. I needed a transformer input for the meters on my tube mixer because all the outputs are transformer balanced and floating and the heater supply it uses is elevated to about 75V above the analogue 0V. So I nicked the op amp bias circuit and output diode arrangement of the JLM and altered the input to use a transformer.

Cheers

Ian

 

[lestatdog]

Attached is a copy of the page from my day book when I designed it. It basically starts with the JLM circuit but alters the front end for use with a transformer.

Is this a good circuit to use with my clasic solos?

 

[ruffrecords]

Attached is a copy of the page from my day book when I designed it. It basically starts with the JLM circuit but alters the front end for use with a transformer.

Is this a good circuit to use with my classic solos?

Only if your Classic Solos have been built with 12V dc heater, If not then you will need a separate 12V dc supply for the meters. You might be able to create s simple dc supply from the heater winding if you are using ac heaters.

Cheers

Ian

 

[MidnightArrakis]

Just to be clear, the top circuit IS the JLM circuit. I needed a transformer input for the meters on my tube mixer because all the outputs are transformer balanced and floating and the heater supply it uses is elevated to about 75V above the analogue 0V. So I nicked the op amp bias circuit and output diode arrangement of the JLM and altered the input to use a transformer.

Cheers

Ian

Attached is an updated schematic using your transformer circuit. Please check it out to see if I have everything OK, OK???

I do have a couple of questions though. 1) Your schematic did not show any resistor value for what is shown as R7/R14 in my version. Do you remember what this value is? 2) I have shown the types of the diodes connected to the VU meters as "BAT85" only because you used that type in your voltage reference circuit. But, isn't the type of diode typically used in this application a type 1N4148? Or, it doesn't matter what is used? 3) The 10K potentiometer is just a single-turn trimmer pot, correct? And.....what exactly is the function of this pot? Level control? 4) Does the capacitor that is connected to the wiper of the pot have its ( + ) side connected to the ( + ) pin of the TL072 (pins 3 & 5) and your R3/4? I am unfamiliar with your polarized capacitor symbol. THANKS!!!

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