Just want to chip in with Brian...
Those transformers realy need to be turned 90 to the left or right... the magnetic field is weakest around the solid laminated metal sides... and strongest over the coils... right over your nice clean inputs... YMMV, but I had to move my EI's to their own box, with my My_Ref.
BTW, those are some nice trafos.... sure I can't talk you into a solidstate project? They'd sure give substance to bass.
Those transformers realy need to be turned 90 to the left or right... the magnetic field is weakest around the solid laminated metal sides... and strongest over the coils... right over your nice clean inputs... YMMV, but I had to move my EI's to their own box, with my My_Ref.
BTW, those are some nice trafos.... sure I can't talk you into a solidstate project? They'd sure give substance to bass.
tested:
-measured between AC1 and AC2 = 50V
-interchanged pins from input connectors
-de-soldered XLR to Cinch
-shortened trafo-wires
-signal path wires moved away from power supply
no success so far.
edit: Nordic, will try that, thanks. Got those trafos for ~15$, so...
-measured between AC1 and AC2 = 50V
-interchanged pins from input connectors
-de-soldered XLR to Cinch
-shortened trafo-wires
-signal path wires moved away from power supply
no success so far.
edit: Nordic, will try that, thanks. Got those trafos for ~15$, so...
Hi,
music after powering up and before the relay clicks and
then increasingly attenuated music after the relay clicks.
This could be the mute shutting down with the wrong/inverse logic.
or
the amp going into protection mode due to a short on the output.
Are the relay contacts wired correctly.
music after powering up and before the relay clicks and
then increasingly attenuated music after the relay clicks.
This could be the mute shutting down with the wrong/inverse logic.
or
the amp going into protection mode due to a short on the output.
Are the relay contacts wired correctly.
The 5-pin relay can only be inserted one way. The orientation of all caps and transistors looks to be correct. Could be a dead transistor, but would be strange to be the same on both channels, which makes me think wiring, but nothing obvious in the picture.
[EDIT] Here are some close ups of a known good RevC if someone else wants to look: http://www.twistedpearaudio.com/user_gallery/_RevC_1.2_Closeups/
[EDIT] Here are some close ups of a known good RevC if someone else wants to look: http://www.twistedpearaudio.com/user_gallery/_RevC_1.2_Closeups/
It's alive.
Thanks all for helping me, it was a wiring problem at the input connector
All that is left is a terrible hum -> transformers have to move in an external box as you already said.
Sounds great so far!
regards, Micha
Thanks all for helping me, it was a wiring problem at the input connector
All that is left is a terrible hum -> transformers have to move in an external box as you already said.
Sounds great so far!
regards, Micha
Humwise... it is the quietest amp I've heard on my speakers... nothing... ziltz.... just get the traffos far away.... mine is on a 1.8m cable...
Trafos are 1m away now, no hum from those anymore, but my bass-amp is the new source of hum on myrevC.
We'll see.
-Micha
We'll see.
-Micha
Hi,
are you two both using the same PCB?
I am wondering what PCB layout characteristic makes the amp susceptible to transformer radiated fields?
I have just laid out a PCB for a single 3886 and I hope I have not made the same error!
are you two both using the same PCB?
I am wondering what PCB layout characteristic makes the amp susceptible to transformer radiated fields?
I have just laid out a PCB for a single 3886 and I hope I have not made the same error!
Hum Pickup
In my experiance, it is not the pcb that picks up the hum. It is the input wiring.
This particular amplifier has an input impedance of 100K. The higher impedance is great for source loading, but increases the pickup of all fields.
One way to check is to move the input wiring around, "dress the leads" and see if this addresses the problem. I have one boxed, two boxed, and four boxed the circuit. All could buzz depending on how the input cables were routed. They also got down to 0.0 mv ac on the output.
I first used these on 100 dB speakers that were flat below 60 hz. This was a better indicator of hash than a DVOM. But having a VOM across the outputs while moving the leads around is a quick way to quieten them down.
George
In my experiance, it is not the pcb that picks up the hum. It is the input wiring.
This particular amplifier has an input impedance of 100K. The higher impedance is great for source loading, but increases the pickup of all fields.
One way to check is to move the input wiring around, "dress the leads" and see if this addresses the problem. I have one boxed, two boxed, and four boxed the circuit. All could buzz depending on how the input cables were routed. They also got down to 0.0 mv ac on the output.
I first used these on 100 dB speakers that were flat below 60 hz. This was a better indicator of hash than a DVOM. But having a VOM across the outputs while moving the leads around is a quick way to quieten them down.
George
George Nailed it. In any power amp (especially single ended designs) wiring of the signal and power supply wires is critical to hum/buzz free operation. The revC boards are no more or less sensitive to this then any other amp, but you can if you choose lower the input impedance a bit (say 10K), that will make the amp a bit less sensitive to EMI.
In any case I am glad the amp is working well now.
Wiring and transformer issues can be addressed separately.
Cheers!
Russ
In any case I am glad the amp is working well now.
Wiring and transformer issues can be addressed separately.
Cheers!
Russ
Hi Russ,
pls allow me to interfere, but as i understand the problem with input impedance can not be solved by lowering nominal input impedance of the amp.
The source of hum/buzz sees input impedance paralleled to the (dynamic) output impedance of the source and that should be way lower than 100K or even 10K. Except it is transformer coupled or something similar (odd).
So if you have lot of hum look at your driving source and the wiring (ground) would be my approach...
regards Holgi
pls allow me to interfere, but as i understand the problem with input impedance can not be solved by lowering nominal input impedance of the amp.
The source of hum/buzz sees input impedance paralleled to the (dynamic) output impedance of the source and that should be way lower than 100K or even 10K. Except it is transformer coupled or something similar (odd).
So if you have lot of hum look at your driving source and the wiring (ground) would be my approach...
regards Holgi
I am only spoke of one source(and mitigation) of input noise(I was thinking EMI, not him), certainly not all of them. Not all noise comes from the source, or even a GND loop. 😉
Thanks.
Thanks.
Hi,
I hope that this is an acceptable post here.
I have a pair of Russ's Twisted Pear My Ref Rev C boards, built up, over in the Market Place on this forum, under Trading Post.
They are unused - too many projects.
Cheers
Stuey
I hope that this is an acceptable post here.
I have a pair of Russ's Twisted Pear My Ref Rev C boards, built up, over in the Market Place on this forum, under Trading Post.
They are unused - too many projects.
Cheers
Stuey
After study the whole thread I am planing to built this circut, base on the very original Rev_C circuit, but since Hong Kong DIY market is quite wired, for example I can buy very hi-end luxury componets like HOLCO resistor easily, and cheap low end China made metal film all over the street, but hard to find something in the middle like Philips resistor, so I have some questions;
1) Which components should be the most critical, which I should use as best as I could offer to buy? Since something like the 22pF small caps is only something cheap or dame expensive I can find as told above, I must know to use my money wise😉
2) Is that enough if I use 4x1600uF/40V for each channal PSU rather then 2x6800uF per channal, which total 8x1600uF=12800uF for both chnnal?
1) Which components should be the most critical, which I should use as best as I could offer to buy? Since something like the 22pF small caps is only something cheap or dame expensive I can find as told above, I must know to use my money wise😉
2) Is that enough if I use 4x1600uF/40V for each channal PSU rather then 2x6800uF per channal, which total 8x1600uF=12800uF for both chnnal?
Member
Joined 2003
On the revC schematic: C1, C2, C17, C18 (220uF) look at datasheets before purchase to find the lowest possible ESR characteristic. The small caps such as 22pF should be c0g type ceramic. Do not use any other type of ceramic. Look at the Twisted Pear parts list here for help. Try to find parts that match the ones on the list as closely as possible. The 0.1% resistors are critical. You may run into stability issues if these are not 0.1% tolerance.
I would try to achieve 2x10,000uF per channel, as indicated in the original schematic. Good luck with the building.
I would try to achieve 2x10,000uF per channel, as indicated in the original schematic. Good luck with the building.
I agree, when I upgraded the 220uf to low ESR Vishays it was a pleasant surprise...
I dissagree about the .1% resistor.. mine ran just fine for over a year on 1% resistors, until my recent upgradeitis.
I dissagree about the .1% resistor.. mine ran just fine for over a year on 1% resistors, until my recent upgradeitis.
Thank you very much.
I try to shop around today and can't find the mentioned ceramic caps, is ceramic type is a must?
Meanwhile, I also read this thread (http://www.diyaudio.com/forums/showthread.php?s=&threadid=69167) about some modifications of this circuit, for the mentioned bipolar feedback cap, from what I understanding the circuit, should be refer to the 220uF, right? What is the minimum voltage rating of the cap should be? I wanna try to use bipolar cap but something good I can only find is ELNA Cerafine 220uF 10V BP, will 10V rating to low?
I try to shop around today and can't find the mentioned ceramic caps, is ceramic type is a must?
Meanwhile, I also read this thread (http://www.diyaudio.com/forums/showthread.php?s=&threadid=69167) about some modifications of this circuit, for the mentioned bipolar feedback cap, from what I understanding the circuit, should be refer to the 220uF, right? What is the minimum voltage rating of the cap should be? I wanna try to use bipolar cap but something good I can only find is ELNA Cerafine 220uF 10V BP, will 10V rating to low?
You are lucky. The 0.1% are absolutely required. Your 1% resistors probably just happened to be within 0.1% of each other. You can use 1% by hand matching them, if your VOM is precise enough. I used 0.1% in the kits because resistor matching on a large scale is not my cup of tea. 😉
Ceramics are not required, but you will have a hard time finding anything else in that value, other than mica (22pF, etc). If you do use ceramics, use C0G/NPO, as they have the required tolerance.
For the ELs, your rail voltages (assuming 24VAC transformer secondaries) will be about around 33-34VDC, so you want to use 50V caps at a minimum.
You could use a bipolar for the feedback cap, but I have seen fantastic results with very low ESR polar caps, such as Panasonic FM series.
The circuit is designed to not depend too heavily on any one component. I would build it with what you can get and experiment/upgrade later.
If you need help getting any of the parts, send me a private email.
Is this idea going to work?
I build a Mauro's design and it's very pleasant to my ears. Then, I'll try a triamp project.
My idea is to make a optimum room to the pcb's and wires and a strange thought came immediately into my mind, after that, a big question:
can I split the Mauro's pcb in 3 portions?
1- the power supply
2- the protection stage
3- the amplifier strictly speaking
Here is a picture of the idea where to split and how to regroup the stages. It's too wild?
I'll be glad to hear opinions
Thanks in advance
Iván Francisco
PS: sorry my language
I build a Mauro's design and it's very pleasant to my ears. Then, I'll try a triamp project.
My idea is to make a optimum room to the pcb's and wires and a strange thought came immediately into my mind, after that, a big question:
can I split the Mauro's pcb in 3 portions?
1- the power supply
2- the protection stage
3- the amplifier strictly speaking
Here is a picture of the idea where to split and how to regroup the stages. It's too wild?
I'll be glad to hear opinions
Thanks in advance
Iván Francisco
PS: sorry my language
Attachments
Conceptually, there is no reason it would not work. As long as the circuits are sound it should work fine.
Cheers!
Russ
Cheers!
Russ