Rohde und Schwarz Begrenzungsverstärker ABR / U23
- Thread starter Falk
- Start date
Help Support GroupDIY Audio Forum:
@Falk do you think it's possible to build a dual mono version and fit two boards into one case?
Only depends on the size of the case and the shielding of the transformers. I personally have no motivation to do it put when using a 4 HE case it should be possible.
I am on my way to do the measurement in the original unit today. I thought of getting these values. Anything else you would recommend?
I want to measure all voltages on the tubes, all inductance and dcr of the primaries and secondaries of the transformers and inducutors, VBs and the resistance at the mode selector switch. Should I measure the inductance at 100Hz or 1kHz?
I want to measure all voltages on the tubes, all inductance and dcr of the primaries and secondaries of the transformers and inducutors, VBs and the resistance at the mode selector switch. Should I measure the inductance at 100Hz or 1kHz?
100Hz is probably more interesting as this gives a clue about low frequency capability and impedance range. What kind of measuring device do you have?
I have a PeakTech 2170 LCR Meter
Good news is the everything is in the right ballpark. Voltages are more or less spot on. Whats really surprising because I was estimating most of the unknow component values from playing around with my spice simulation. I have a bit of a difference in the bias of the side chain diode but also the whole side chain is modded anyway and works. So I dont want to overthink this.
Voltages R+S U23:
V1 + V2: K 0.5V A 250V G2 47V
V3 K 13V A 143V
V4 K 3.7V A 230V
V5 K 20V A 250V
Diode: K 2.1V
Double Triode: K1 80V A1 250V K2 3.4V A2: 70V
Input TX is 1:1.5 (32mH : 48mH @100Hz) - I use 1:1
Interstage TX is: 1:1.2 (28.5H : 34H @100Hz) - I use 1:1
Output: made a failure here (I assume 2 : 1) - I use 1:1
Sidechain: 3 : 1 (135H : 50H @100Hz) - I use 5 : 1
L2: 100H 2k5 - I use 150H 3k7
L3: 60H 3k2 - I use 60H 2k7
Voltages R+S U23:
V1 + V2: K 0.5V A 250V G2 47V
V3 K 13V A 143V
V4 K 3.7V A 230V
V5 K 20V A 250V
Diode: K 2.1V
Double Triode: K1 80V A1 250V K2 3.4V A2: 70V
Input TX is 1:1.5 (32mH : 48mH @100Hz) - I use 1:1
Interstage TX is: 1:1.2 (28.5H : 34H @100Hz) - I use 1:1
Output: made a failure here (I assume 2 : 1) - I use 1:1
Sidechain: 3 : 1 (135H : 50H @100Hz) - I use 5 : 1
L2: 100H 2k5 - I use 150H 3k7
L3: 60H 3k2 - I use 60H 2k7
Last edited:
protools
Active member
- Joined
- Nov 7, 2010
- Messages
- 36
Option 2 or 3 is fine
As people keep asking, which I understand:
I know its tiring but I am not coming with the best news. Financially I have to prioritize some studio projects before I can dive into the U23 thing again. Since I use the U23 on a daily base for paying clients I need to build two main boards of the last revision to test them and finally set them free to the people that are on the list. Dumping two or three days and about 1000 Euro in a machine that is working is kind of not so appealing. As of right now I can need the money and time to get the studio in shape and work done. I will asap finish this build - thanks for your patience. Its going to be great. I promise.
I know its tiring but I am not coming with the best news. Financially I have to prioritize some studio projects before I can dive into the U23 thing again. Since I use the U23 on a daily base for paying clients I need to build two main boards of the last revision to test them and finally set them free to the people that are on the list. Dumping two or three days and about 1000 Euro in a machine that is working is kind of not so appealing. As of right now I can need the money and time to get the studio in shape and work done. I will asap finish this build - thanks for your patience. Its going to be great. I promise.
AnthonyBisset
Member
Hi @Falk ,
Totally empathize with work/life equations slowing projects down.
I'm about to start building Heikki's Vari-Mu and u73bt/u273/u373/rn2254 inspired diode comp. (Thanks @scott2000)
Also have a DRIP u73B board sitting here begging for attention.
Even worse, I can't get my mind off the u23 or Vacuvox, but they're both ridiculously expensive. All I really know is I've joined the Uxx tribe and have a lot of populating ahead of me. Whenever your take on the U23 happens, i'd love to be included in the PCB list if that might be possible? Cheers, /A
Totally empathize with work/life equations slowing projects down.
I'm about to start building Heikki's Vari-Mu and u73bt/u273/u373/rn2254 inspired diode comp. (Thanks @scott2000)
Also have a DRIP u73B board sitting here begging for attention.
Even worse, I can't get my mind off the u23 or Vacuvox, but they're both ridiculously expensive. All I really know is I've joined the Uxx tribe and have a lot of populating ahead of me. Whenever your take on the U23 happens, i'd love to be included in the PCB list if that might be possible? Cheers, /A
Could you write a mail to [email protected] - I ll put you on my list then. The price was the only reason I got into this endeavor. The wait will be worth it. I also have the U73 boards and transformers in the drawer. Since I have the U23 I dont feel like needing something else. I also have a Stamchild 670 and in 95% of the cases I prefer the U23 on the stereo bus.
I updated the BOM today and changed my plan a bit to get on track faster. I wanted to check transformers from Igor but I will skip this. Maybe someone of you people might do this. So this build will be recommended to use Edcor transformers and Hammond chokes.
Per Channel:
2 x 15k:15k EDCOR XSM (Input and Interstage)
1 x 10k:10K EDCOR WSM (Output)
1 x 15k:600r EDCOR WSM (Sidechain - 600r side only using half of the winding)
1 x Hammond 156c (First Gain Stage)
1 x Hammond 155c (Output Stage)
I will do the following. I will order REV 3 boards next week. This is the revision I want to give to you. I will order the exact BOM for the signal board and build two of the signal boards. I will put these in place of my REV 2 boards and see how it goes. When everything goes fine I ll do some calculations and contact everybody from the list and take orders. I hope all this will happen until end of June 2024.
The PSU is fine. It works very stabile in the U23s since almost 2 years and in my stereo V76 since a couple of months.
I used custom transformers with electrostatic and magnetic shield. The power TX will need to deliver:
Secondary 1 HV: 225V 150mA (200V is the absolute minimum)
Secondary 2 Filament: 12V 4A (should not have less than 3A)
Secondary 3 Calibration: 12V 100mA or more
So if you want to start gathering some stuff. Here you go.
The boards need the following tubes:
2 x EF83 (I can provide some of you with those)
3 x EF86 or PF86 (I can provide some of you with those)
1 x 6SN7
1 x 6AL5
Best,
Falk
Per Channel:
2 x 15k:15k EDCOR XSM (Input and Interstage)
1 x 10k:10K EDCOR WSM (Output)
1 x 15k:600r EDCOR WSM (Sidechain - 600r side only using half of the winding)
1 x Hammond 156c (First Gain Stage)
1 x Hammond 155c (Output Stage)
I will do the following. I will order REV 3 boards next week. This is the revision I want to give to you. I will order the exact BOM for the signal board and build two of the signal boards. I will put these in place of my REV 2 boards and see how it goes. When everything goes fine I ll do some calculations and contact everybody from the list and take orders. I hope all this will happen until end of June 2024.
The PSU is fine. It works very stabile in the U23s since almost 2 years and in my stereo V76 since a couple of months.
I used custom transformers with electrostatic and magnetic shield. The power TX will need to deliver:
Secondary 1 HV: 225V 150mA (200V is the absolute minimum)
Secondary 2 Filament: 12V 4A (should not have less than 3A)
Secondary 3 Calibration: 12V 100mA or more
So if you want to start gathering some stuff. Here you go.
The boards need the following tubes:
2 x EF83 (I can provide some of you with those)
3 x EF86 or PF86 (I can provide some of you with those)
1 x 6SN7
1 x 6AL5
Best,
Falk
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Hi Falk. I have been following this thread from the beginning. This project interests me. What price do you estimate the boards to cost ?
I think 75€ without PSU Board and 100€ with PSU Board. But I cant really make the calculation before I know how many people will order.
I think the cost per channel will be like:
electrical components 200€
transformers 200€
case 200€
tubes 120€
PCBs 100€
misc 100€
power tx 75€
cable and hardware 50€
-----------------------------
1045€ per channel
Count me in for a set of pcbs please. Can you give more details of the mains transformer so I can work out if I have something suitable lying around here ?
rock soderstrom
Tour de France
Secondary 1 HV: 225V 150mA (200V is the absolute minimum)
Secondary 2 Filament: 12V 4A (should not have less than 3A)
Secondary 3 Calibration: 12V (100mA or more)
Could you please write a mail to [email protected] I ll get back to you as soon as I plan the orders.
Presumably one doesn't actually need the calibration voltage in the box. Does this unit need calibrating a lot ? Could one use a bench PSU ?
Looks like the Hammond 369HX could be a good candidate for the mains transformer.
