Idea for a dedicated Rhodes preamp, need help !

[PermO]

Here's the datasheet for the Beyerdynamic transformers I have.

https://www.technicalaudio.com/pdf/Beyer_Dynamic/Beyer_Dynamic_input_transformers_1976_oct_cat.pdf

TR/BV 310 001 001 is 200 Ohms ...these were labeled matrix output on the patchbay I got these from
TR/BV 310 001 061 is 1200 Ohms ...these were labeled matrix input

I have both, and it sits on a socket now so I can easyly swap that.

Any suggestions on the driver ?

 

[PermO]

So I swapped the 200Ohm version for the 1200Ohm version in the test circuit and indeed it handles exessive low end a lot better now.

 

[MidnightArrakis]

So I swapped the 200Ohm version for the 1200Ohm version in the test circuit and indeed it handles exessive low end a lot better now.

[it handles excessive low end a lot better now] -- GREAT!!! Now you can become excessively rich beyond your wildest dreams by selling this device to all of the HIP-HOP/RAP creators around the world!!! If their material doesn't have "excessive low-end" in it.....then it is considered not to be worthwhile!!!

Here's your -- TR/BV 310 001 061 -- transformer for all of posterity:



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[PermO]

You're quick at that lol...

The 061 transformer shares the same construction as the 001 transformer, pins in dip8 style, I got it on a socket and just swapped it.

I would still like to know what goes wrong driving the 200 Ohm version.

Going to two layers using via's will not save on cost that much, I might as well stick with the four layer version.
Changing the color to green and increasing the number of units will make it cheaper, but if you only order 10 pieces it's not that much of a difference.

 

[MidnightArrakis]

You're quick at that lol...

The 061 transformer shares the same construction as the 001 transformer, pins in dip8 style, I got it on a socket and just swapped it.

I would still like to know what goes wrong driving the 200 Ohm version.

Going to two layers using via's will not save on cost that much, I might as well stick with the four layer version.
Changing the color to green and increasing the number of units will make it cheaper, but if you only order 10 pieces it's not that much of a difference.

[increasing the number of units will make it cheaper] -- That's usually how it works for practically everything known on Earth!!!

[but if you only order 10 pieces it's not that much of a difference] -- It depends upon who and where you are ordering PCB's from. I know of a PCB-fabricator here in the U.S. that is always running a continuous "special" in one of my PCB-design magazines. Their "special" is.....Order and pay for 10 PCB's from us and.....we will ship you 20 PCB's at NO EXTRA COST!!! Or, something like that. Other PCB-fabricators advertise that you order a minimum of 5 PCB's and the cost is almost "next to nothing", plus shipping!!!

[I might as well stick with the four layer version] -- If you are going to go that route.....I would try and cram as much of your basic "signal routing" on LAYER-1 - TOPSIDE, then LAYER-2 as Vcc and LAYER-3 as Vnn only instead of "routing" those layers, use "Copper Pours" instead attached to those two nets and then finally, LAYER-4 as GND and again, use a "Copper Pour" attached to the "GND" net.

My 2-Guilders worth!!!

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[MidnightArrakis]

The 061 transformer shares the same construction as the 001 transformer, pins in dip8 style, I got it on a socket and just swapped it.

Here's the correct transformer:


>> EDIT: Added cool-looking label to transformer casing.

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[Pinokio]

That’s indeed a cool looking label! Can’t get my eyes off the label!

So I guess @PermO if possible I’m interested in a pcb if there is one in the future!

I’m using a JSI Peterson clone atm build from a board he was selling a couple of years back. Would be happy to add this one next to it for a different (probably more hifi?) flavor next to it

 

[PermO]

No problem, I just ordered 20 very fancy boards from JLC PCB.
Probably here in two weeks. and hope I made no mistakes.
I can also provide you the vintage Beyerdynamic aux output transformer if you wish (it can easyly be bypassed on the circuit board)

Main out, very clean and punchy, aux out has a bit of a vintage flavour with the germanium transistor, baxandall EQ and the transformer.

 

[PermO]

20 pieces came in the mail today

 

[MidnightArrakis]

20 pieces came in the mail today

>>> THAT WAS RATHER FAST!!!.....

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[PermO]

I just populated one of the boards and it's all good, both outputs are in phase and it all sounds good.

 

[MidnightArrakis]

I just populated one of the boards and it's all good, both outputs are in phase and it all sounds good.

>> Is the schematic that you show in Post #170 your -- FINAL -- schematic??? Any other changes/updates/farts???

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[PermO]

Some resistor values have been slightly tweaked, the schematic has not changed, I will post a final version of the schematic.

 

[MidnightArrakis]

Some resistor values have been slightly tweaked, the schematic has not changed, I will post a final version of the schematic.

[I will post a final version of the schematic] -- YA-A-A-A-A-A-A-A-A-AYYY!!!!!!!

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[PermO]

there it is...

 

[MidnightArrakis]

there it is...

LOOKS GOOD!!!.....

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[L´Andratté]

”Matters of great concern should be treated lightly.” Master lttei commented, “Matters of small concern should be treated seriously.” (Hagakure)

What comes to my mind when I see your treatment of what might be conceived as a "simple" DI-box.
Big thumbs up!

How much difference does the germanium driver (as a simple follower) make to the sound, you think?

Why did you choose a transformer with 200:200 impedance, as in wouldn´t a 600:600 work also fine?

 

[PermO]

I really like that quote

For me personally , DI sound is very important as my genre is funk / hip hop, muted guitar, muted bass and my old Rhodes mk I (no onboard pre, just a tonestack) are my main sounds.
I like my sounds punchy and bone dry.

I do have several DI inputs in my setup (soundcard and preamps) and they all sound fine with a guitar, when I plug in my passive jazzbass or Rhodes piano the differences start to show.

This circuit beats all of them, and takes the mic pre out of the equation, you can hit that transformer input on that big old compressor straight from this box and make it sing, no DI does that.

I put in the transformer simply because I have quite a lot of them and I liked the idea of a galvanically isolated aux output, plug in a bass, boost low and high and take level down a bit before the transformer and some nice sounds can be found there at the aux output. I swapped the 200:200 version for a 1200:1200 version as it was easyer to drive and was less prone to distort. I have terminated the secondary based on the Beyerdynamic datasheets that provide termination for 1M inputs, I guess that would be in the ballpark for most pedals.

I really like what germanium transistors do, but in this case it does not impart a whole lot of it's sound, I have increased the current a little bit compared to the first version. I have it on a socket so I can swap it, sillicon will be fine there and I think I will settle for some sillicon transistor and save my germanium for something else. But I don't have any so I will need to buy some.

Now I have to drill some enclosures...

 

[PermO]

I drilled the first enclosure and it's a pretty tight fit.
Now the gap in the top corner of the circuitboard makes sense;
With ?


Or without the idiot bar ?

I have not made the final connections, last resistors, as the enclosures will be out for powdercoating and hopefully I can get a UV print on it from some local service.

 

[MidnightArrakis]

[With? Or without the idiot bar?] -- Personally.....I would go with "With", but I would use an "Idiot Bar" (Rack-Handle) that is "higher". Unless the bar is strictly for "knob protection", a higher bar will allow more space to slip your fingers and knuckles through.....if you are going to carry this stomp-box that way. Dunno.....

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