Good luck with the move! We’ll look forward to the possibility of boards next year!
Rohde und Schwarz Begrenzungsverstärker ABR / U23
- Thread starter Falk
- Start date
Help Support GroupDIY Audio Forum:
Good Morning,
just a short notice for those who followed this thread in its entire form.
You sure remember that at some point I discovered the sub bass distortion issue. I minimized it by starting to fool around with different gain staging using different audio transformers. That indeed changed the sound to the better. It got so okay that I felt well to use it for mastering. Anyway, even if it was almost cured, this slight distortion was still there.
Last week some guy close to me sold six pieces of used but tested Valvo EF86. 30 Euro for all of them. Each tested to at least 110% on Roetest 10.
Today it sticked them into the machine et voila - its gone. Dead clean and the bass as tight as I never heard it.
Before I used JJ EF806 in the same positions because I assumed them to be less noisy. This indeed is not the case too.
Just to let you know. Substituting EF86 with the JJs just dont make much sense unless its a guitar amp.
Best,
Falk
just a short notice for those who followed this thread in its entire form.
You sure remember that at some point I discovered the sub bass distortion issue. I minimized it by starting to fool around with different gain staging using different audio transformers. That indeed changed the sound to the better. It got so okay that I felt well to use it for mastering. Anyway, even if it was almost cured, this slight distortion was still there.
Last week some guy close to me sold six pieces of used but tested Valvo EF86. 30 Euro for all of them. Each tested to at least 110% on Roetest 10.
Today it sticked them into the machine et voila - its gone. Dead clean and the bass as tight as I never heard it.
Before I used JJ EF806 in the same positions because I assumed them to be less noisy. This indeed is not the case too.
Just to let you know. Substituting EF86 with the JJs just dont make much sense unless its a guitar amp.
Best,
Falk
Attachments
Agree. Matches my experience with JJ.
Curious... where do y'all get those rail bars to mount the boards to the case with? Nice build by the way.
I though so. Thanks
PermO
Well-known member
What a beauty !
Love that ratio switch, that's really cool !
Love that ratio switch, that's really cool !
Ive seen lots of faults with JJ tubes also , I wouldnt reccomend them to anyone , if someone shows up with them and wants an amp repaired , I'll strongly advise against using them , if they want to plough ahead regardless and use them ,I'll fit them but I wont give any guarantee , where normally I'd give three months .
Ratio switch looks like a 5 way Strat pickup selector .
Ratio switch looks like a 5 way Strat pickup selector .
PermO
Well-known member
I agree on the JJ tubes, never liked them...
If I need new production tubes I go with Tung Sol.
If I need new production tubes I go with Tung Sol.
SKJGProject
Well-known member
any updates on this?
Unfortunately not. The units are working great. I use them almost every day. I will do a pcb run once I find time to write a documentation. As written above - I am building a studio right now which takes all of my spare time this year. Next year is going to begin very busy too but I hope to find time late summer next year to get the stuff together and make it a diy project.
I still have the emails of all the people interested and will contact you asap.
Best,
Falk
I still have the emails of all the people interested and will contact you asap.
Best,
Falk
Good day Gentleman,
the studio build is finished, the first album is recorded and its time to move on with the U23 before I ll become father in summer. This weekend I will check and update the BOM and order the REV 3 main circuit boards and build the last revision of the mainboard and check if everything works.
What I can do is:
If the boards test to be okay. I will make one single run of boards. (There are about 15 people of interest)
I have some stock of EF83 and EF / PF86. This means I can supply some of the orders with NOS tubes. The boards have jumpers so they can be fitted with EF and PF tubes. I also have a bunch of the R+S meters I used.
I can not provide a build manual. I can provide the schematic of the main board and PSU. I will provided printed versions of the circuit with each order. But there is definitely some experience needed to get the stuff together. This will not be a no brainer project. There will be a build thread to help each other.
Is this alright for you guys? What state of DIY project is acceptable for you? If there is the need for a build manual, I will need some help from the community to do it. I simple dont have time right now. I could imagine to collaborate with one or two people to make this an easier build if you say thats needed.
Right now I see challanges here:
- PSU transformer is custom made in Poland and a group buy would make things easier but I can not pre-finance 20 or more transformers.
- I would recommend to use the exact Edcor transformers I used. I tried different ones and this always meant problems
- mechanical design - I will not provide the faceplate
Looking forward to your feedback. Thank you.
Falk
the studio build is finished, the first album is recorded and its time to move on with the U23 before I ll become father in summer. This weekend I will check and update the BOM and order the REV 3 main circuit boards and build the last revision of the mainboard and check if everything works.
What I can do is:
If the boards test to be okay. I will make one single run of boards. (There are about 15 people of interest)
I have some stock of EF83 and EF / PF86. This means I can supply some of the orders with NOS tubes. The boards have jumpers so they can be fitted with EF and PF tubes. I also have a bunch of the R+S meters I used.
I can not provide a build manual. I can provide the schematic of the main board and PSU. I will provided printed versions of the circuit with each order. But there is definitely some experience needed to get the stuff together. This will not be a no brainer project. There will be a build thread to help each other.
Is this alright for you guys? What state of DIY project is acceptable for you? If there is the need for a build manual, I will need some help from the community to do it. I simple dont have time right now. I could imagine to collaborate with one or two people to make this an easier build if you say thats needed.
Right now I see challanges here:
- PSU transformer is custom made in Poland and a group buy would make things easier but I can not pre-finance 20 or more transformers.
- I would recommend to use the exact Edcor transformers I used. I tried different ones and this always meant problems
- mechanical design - I will not provide the faceplate
Looking forward to your feedback. Thank you.
Falk
Last edited:
capacitorless
Well-known member
First (and most important), congratulations on the impending fatherhood!
I would like to help, unless you end up with someone better qualified, haha! One thing I was considering was volunteering to put together and maintain a calibration document? I'm a neophyte at some of this, but I have done technical documentation in the past, and learn quickly.
I also have some pretty decent quality 6SN7 here, to send out to the people doing a build.
I would like to help, unless you end up with someone better qualified, haha! One thing I was considering was volunteering to put together and maintain a calibration document? I'm a neophyte at some of this, but I have done technical documentation in the past, and learn quickly.
I also have some pretty decent quality 6SN7 here, to send out to the people doing a build.
Thank you @capacitor and @protools
I can do a calibration manual. Thats not a biggie. What I can not to is a step by step guide of how to assemble the main board, psu and switches.
Actually there is only the 24 step output gain switch which bears resistors. All there rest of the switching is implemented on the board.
I can do a calibration manual. Thats not a biggie. What I can not to is a step by step guide of how to assemble the main board, psu and switches.
Actually there is only the 24 step output gain switch which bears resistors. All there rest of the switching is implemented on the board.
thomasdf
Well-known member
I could be interested in whatever it takes to make a dual mono unit. Is a single power transformer sufficient ?
Hi Falk,
i read along right from the start of this threat; it was fun to "watch" ...ääähhh ... read your journey and even better with a happy end
I'm definitely interested in a pcb, sounds like a fun project.
Calibration manual would be great and maybe a short document (or post here) with Tips 'n Trix..
... and the transformer spec. Maybe we can order a small batch from Rondo-Müller...
ROCK-ON!
i read along right from the start of this threat; it was fun to "watch" ...ääähhh ... read your journey and even better with a happy end
I'm definitely interested in a pcb, sounds like a fun project.
Calibration manual would be great and maybe a short document (or post here) with Tips 'n Trix..
... and the transformer spec. Maybe we can order a small batch from Rondo-Müller...
ROCK-ON!
Awesome to see that we’ve finally arrived at this stage! Also, big congratulations on the upcoming transition to fatherhood!
I’m guessing I’ll be one of the weaker links as far as experience and know-how is concerned. With that in mind, I’d say that any documentation is obviously welcome, but between what you have said you’re able to provide and a build thread, I think it’s enough to get most of us up and running. As Dr_J mentioned, a little “tips and tricks” roundup would probably go a long way as well.
I’d be in for a group buy for the power transformer.
I’m guessing I’ll be one of the weaker links as far as experience and know-how is concerned. With that in mind, I’d say that any documentation is obviously welcome, but between what you have said you’re able to provide and a build thread, I think it’s enough to get most of us up and running. As Dr_J mentioned, a little “tips and tricks” roundup would probably go a long way as well.
I’d be in for a group buy for the power transformer.
capacitorless
Well-known member
Just my 2 centavos, no assembly manual needed We should be able to fill in the blanks in a build thread. If that changes, I'll be glad to step up.
We should be able to fill in the blanks in a build thread. If that changes, I'll be glad to step up.
