REAMP BOX (original) - Fixed with schematic

[BGroen]

Hi all,
The US patent schematic is attached. I found a 600R / 25k transfomer from Hammond that might do the job.
Does the exact 500/30k ratio matter that much? I see many designs with different transformers so I think I can make it work.

Hope hearing,

Beinte

https://nl.mouser.com/ProductDetail/Hammond-Manufacturing/107V?qs=jGmGUJJvvdV4UDIOEdfHuA==

 

[gyraf]

..can you really get a US patent on common-sense stuff like that..? Surrealistic..

 

[musipol]

I think I remember, back in the day, looking at a patent awarded to Randall Smith, for the master volume. I found that hard to believe.

 

[klem]

Hi all,
The US patent schematic is attached. I found a 600R / 25k transfomer from Hammond that might do the job.
Does the exact 500/30k ratio matter that much? I see many designs with different transformers so I think I can make it work.

Hope hearing,

Beinte

https://nl.mouser.com/ProductDetail/Hammond-Manufacturing/107V?qs=jGmGUJJvvdV4UDIOEdfHuA==




View attachment 116868

I can't be of much help here, but it's a bummer to see an earnest, respectful question get ignored with folks repeatedly going on about patent legitimacy. Hopefully some others will be more helpful @BGroen

 

[dmp]

Does the exact 500/30k ratio matter that much?

No, it does not matter much. The spec'd transformer drops the level 35.6dB while your Hammond would drop the level 32.4dB. More important is any frequency difference or distortion from a potential cheap transformer.
I've tried the patent version (with O-10) and NYDs version. I found the only control I need is a ground lift. I don't build in a pad, the RC filter, any series resistance, or the output pot. Simple is good. So the input +/- goes to the transformer and steps down to the TS output. I've always used reamps with the transformer stepping down.
My goal, however, was to be able to DI a guitar or bass into the DAW and reamp with no audible difference compared to the guitar or bass going straight into the amp.

 

[JohnRoberts]

..can you really get a US patent on common-sense stuff like that..? Surrealistic..

Not that surprising as a patent just gives the inventor the right to sue for infringement.

That patent's status is expired so it is public domain and free to use.

JR

 

[Whoops]

The spec'd transformer drops the level 35.6dB while your Hammond would drop the level 32.4dB.

It's not a Drop, it's a Boost.
The transformer is wired as a Step Up

 

[dmp]

It's not a Drop, it's a Boost.
The transformer is wired as a Step Up

Not in mine. I said that in my post.

 

[BGroen]

Hi all,
So I've made a very simple box using the NTE 10/3 from Neutrik.
It works, it's easy, so I'm happy.

I got a 3 questions maybe someone can awnser easily:

The U-pad I have has an input impedance of approx 600Ohm. (As I saw some others did and the original has).
1). Doens't it make more sense to have a >10k impedance input, like modern line inputs?

Due to the step-up the output is quite high and the 50k pod is almost at the bottom. Decreasing the output impedence I believe.
2). Doesnt it make more sense to have a larger level drop with the U-pad so that the 50k pod has less influence?

I can see in some schematics that there is a small capacitor after the pad accross +/-.
3). What is it for, should I add it, and what value would it be?

Hope hearing!

PS, the jack input at the AMP side is replaced by a plastic one (not in the picture) so that the ground-lift works (oepsie).

 

[drtechno]

..can you really get a US patent on common-sense stuff like that..? Surrealistic..

Yes you can, but since I don't use the pad in front of the transformer, the deviated design is a standard circuit which can not be patent and it works better.

 

[Mr. Moscode]

I suspect the novelty is more in the process of reamping than in the exact circuit configuration. Did nobody reamp before 1994? (the date of the patent).

Cheers

Ian

My musing on the subject:

https://en.wikipedia.org/wiki/Re-ampThere's a little history there and, IMHO, the process was not a blinding stroke of genius, but a blinding stroke of the obvious. The genius is making it available w/o having to build one.

My guess is John Cuniberti built one and thought, "Hell, a patent is worth a try." Apparently he got lucky. But the TM of the name is worth the money even though it has become a generic term, and probably was before John Cuniberti went to the USPTO. Who knows how many of these boxes were sold? Probably many more than DIYers have made. Saves time in a high level pro setting to have one that works right.

The trade name on the xfmer may have been made up just for this product.

 

[Mikaeel]

Radial ProRMP

Has AEE19-3460, not the custom-wound transformer many thought.
1:1 10k transformer was chosen because many of the line outs have a variety of output impedance. To handle it properly, they chose voltage impedance matching, so from 10ohm or less, to 1kohm, such impedance converter will work.
Transformer datasheet below. So if anyone wants to build their own, LL1540 or similar from Jensen, Cinemag, ... etc will probably work fine!
P.S. I will upload the schematic later (owner will have to remove the PCB), but at first glance it looks pretty close to the original, except for the H-pad.

 

[Mikaeel]

 

[Brian Roth]

View attachment 120307

DAMN! The input resistor values as drawn are insanely low.

Bri

 

[Newmarket]

DAMN! The input resistor values as drawn are insanely low.

Bri

Guessing there's a "K" missing there.

 

[Mikaeel]

Guessing there's a "K" missing there.

Unless I made a mistake, gold - gold - violet - yellow is on the picture.
There's also a +4db line input specified above the input port. Looks like everything is correct, this attenuator reduces about -3.121db, probably to match 0db (idk, please correct me if I'm wrong).

 

[Brian Roth]

According to the posted schematic (linked above) the signal driving into the XLR sees a 17.6 Ohm load via R2/R3/R4.

Even old vacuum tube line-level sort of load.gear (RCA, WE, Etc) could never drive that load.

Something is amiss with those resistor values in the posted schemo...

Bri

 

[Newmarket]

According to the posted schematic (linked above) the signal driving into the XLR sees a 17.6 Ohm load via R2/R3/R4.

Even old vacuum tube line-level sort of load.gear (RCA, WE, Etc) could never drive that load.

Something is amiss with those resistor values in the posted schemo...

Bri

15R6 by my arithmetic. Ignoring the 10K on the secondary.

 

[Newmarket]

Unless I made a mistake, gold - gold - violet - yellow is on the picture.
There's also a +4db line input specified above the input port. Looks like everything is correct, this attenuator reduces about -3.121db, probably to match 0db (idk, please correct me if I'm wrong).

Sanity check on the load seen at the input.

 

[Brian Roth]

15R6 by my arithmetic. Ignoring the 10K on the secondary.

OOPS....my old/tired eyeballs misread R4 as 8.2 Ohms.

Bri