Mod a Behringer T1953

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walter

Well-known member
Joined
Jun 21, 2006
Messages
416
Location
Seattle Wa. U.S.A.
Mod a B'ringer T1953. Polish a turd? Why bother? Changing out tubes is fine if the tubes actually do something. I am interested in getting something out of this unit, It looks good, I want to make it sound good too. I have purchased a power transformer for a fender standalone reverb unit. My first mod will be to install it to add Heater voltage, and then to add high voltage to the tubes. I have built a board for the rectifier, now I just need to cut some traces, and wire it. There is plenty of room in that chassis. After this mod, I will address the actual pre-amp circuit, the solid state part.
 
From what I've heard, the tubes are only mixed in for some crunch. If that's the case, the unit might still work if you take out the tubes.
 
Don't count on being able to "upgrade" tube powersupply without potentially damaging other parts of the circuit.

Start out with finding the schematic, very little can be done without that.

Post it here, and we'll discuss...

Jakob E.
 
Schematic uploaded to our gmail account - for details look at the end of the Meta-meta.

It surely does not look like a circuit that would benefit from upgraded powersupplies - more from like removing the tube circuit parts alltogether..

Jakob E.
 
http://www.groupdiy.com/index.php?topic=6078&highlight=behringer

That has some pretty good info about changing out some of the OpAmps and caps. Also working some on the power supply.

It sounds like your mods you are looking at might be a bit more extensive.

From my use with stock ones, just the straight pre-amp without the tubes really isn't too bad. I have also heard some great recordings made with those.

At the price you can sometimes find those used, it is probably worth it just for the case, power transformer, connectors, lights, switches, etc. Then just build a whole new circuit in there.

I think they look cool too.
 
That original post for the T1953 is very interesting. Now I am tempted to build my own circuit for the pre-amp. I keep coming to the conclusion that I'm better off building from scratch, as opposed to modding. But I will continue with this project.
 
[quote author="okgb"]Walter , do you have more cases ?

regards Greg[/quote]
PM'ed you
So, I wired up the high voltage last night and did a quick audio test, the WARMTH control is more noticeable. I'll have to put a scope to it next time I get a chance. My power supply delivers 370 volts to the pcb, thru 240k ohm resistors to the plates. The resistors are the original ones on the board, I just cut the trace going to the stock supply. I inserted four .02 caps in the connecting wires to the main board to block that high voltage. The stock cathode caps were high enough voltage rating. The traces to the plates are so tiny I don't expect them to last long.
 
Now the schematic is available (thanks Jakob !) let's for completeness also throw a glance at that 'UTC-magic' before people start cutting out that section, not ?

Rosi provided us with the patent-number in this thread (thanks as well):
http://www.groupdiy.com/index.php?topic=17795&postdays=0&postorder=asc&start=45

DE000019631892A1

For convenience I've uploaded them here (note they're in Deutsch):

http://www.twin-x.com/groupdiy/albums/userpics/depatisnet_DE000019631892A1_pg1.pdf
http://www.twin-x.com/groupdiy/albums/userpics/depatisnet_DE000019631892A1_pg2.pdf
http://www.twin-x.com/groupdiy/albums/userpics/depatisnet_DE000019631892A1_pg3.pdf
http://www.twin-x.com/groupdiy/albums/userpics/depatisnet_DE000019631892A1_pg4.pdf

Summary of the circuit in the third pdf, from line 13 on.

Bye,

Peter
 
[quote author="Rossi"]Note the beautiful artwork on page 4 :shock:[/quote]
Indeed, it's remarkable that he didn't let a manual-DTP-employee spend a few minutes on it. In its present form it looks quite like the original back-of-envelope drawing :cool:


BTW, it's clear he didn't intend an opamp without any feedback, just a substractor. OK...
 
Maybe they thought it was such a hot idea that they couldn't waste another minute. :grin:
 
[quote author="Rossi"]Maybe they thought it was such a hot idea that they couldn't waste another minute. :grin:[/quote]
Right ! :grin:

Or wouldn't Uli trust his own employees ?

But wait... hot idea.... @ 24V plate voltage.... :roll: :cool:

But OK, apart from the UTC-section & HPF this looks like a preamp as in their mixers. Did I miss any essential differences ?

Bye,

Peter
 
no, I don't think you missed anything. Pretty much all of their preamps look essentially the same. Take a look at the analogue section of the ADA8000 - almost identical. They always have pretty good input transistors, though.
 
[quote author="aortizjr"]Well and it is also SMT...

My hands are not nearly steady enough to play that game. My eyes aren't that great either.[/quote]
There is a quad TL074 thru hole on each channel by the Warmth controls, and the 'lytics are radial so you could change the coupling caps.
I'm not seeing a parallel tube circuit. It looks like the tube section comes after the pre-amp.
The Warmth control is a dual pot. One side is between the two grids, the other side is after the tubes, it looks like a volume into an op-amp.
Could someone please summarize a translation of the patent description?
My co-worker loosely translated the text, but I'm not completely grasping the concept. Also with the 1/2 of the warmth pot turned down, it seems like the signal is at ground.
Now I really need to scope it out.
 
[quote author="walter"]Mod a B'ringer T1953. Polish a turd? Why bother?[/quote]
FWIW, here's somebody using it as a starting point for 'ribbon-optimized-preamps'...
http://www.proaudioheaven.com/index.cfm?CFID=41284609&CFTOKEN=15476424
No idea if he's just swapping the opamps (for Burr Brown 2134) or does some other tweaks as well.

http://cgi.ebay.com/Upgraded-Behrin...yZ119018QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Steve said most of the sound was the opamps so he put the very best, Burr Browns, in all stages. The gain increased by at least 30% the noise definitely decreased by more than 80%.
Hard to believe though that the stock unit doesn't reach the front-panel advertized gain - but that were of course the not too scientific words of the happy customer...


edit:
Ah, old news...
http://homerecording.com/bbs/showthread.php?t=222685
 
I think about this mod from time to time, and the other projects I have been neglecting. Perhaps with the rainy season here I will be able to get those "burr brown bugs". There is also a place to mount an audio transformer on the jack pcb. The same transformer is used in their D.I. boxes, and that may be the only source for that part.
 
[quote author="walter"]I think about this mod from time to time, and the other projects I have been neglecting. Perhaps with the rainy season here I will be able to get those "burr brown bugs". There is also a place to mount an audio transformer on the jack pcb. The same transformer is used in their D.I. boxes, and that may be the only source for that part.[/quote]
Having this box anyway (originally got it just for the meters...) it looks like a worthwhile mod... as you said, someday....

W.r.t. gain & ribbons, I haven't checked the schematic or simply measured yet what the total amount of gain available is from this box...
I guess it's 8 Bel (60 dB from the mic-gain + 20 dB from the level control).
 

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