Crikey, it works.
Hi,
Sorry, another newbie here but I feel I must add my thanks to Peter Daniels and his amp design based upon the LM3875. Right from the prompt delivery of the boards and components to the comprehensive guidance notes offered on this forum; Peter is offering a very professional service. Having read and re-read this particular thread, to try and ensure I understood enough, it is clear that he has the expertise and patience to explain the same topic over again to help anyone in difficulty.
My amplifier is now complete, hum free, and at the moment replaces my NAD 350. After checking and rechecking the DC offset I put my amp into my system, consisting of a Cambridge Audio 540, Systemdek (via Cambridge Audio 640) and KEF Q3’s. After playing Miles Davis ‘So What’ and Yes ‘Future times’ (a couple of my favourite test tracks) I swapped back to the NAD to play the tracks again. Initially I broke out in a cold sweat because the KEF’s now sounded like they had socks over them and I thought I had damaged them with my new amp! I guess that illustrates the difference, as far as I am concerned.
I intend to pull together some of my experiences in building my version of Peter’s amp and post on this forum. I hope that it will help some other potential newbie to jump in and try their skill.
Cheers
Jeff
Hi,
Sorry, another newbie here but I feel I must add my thanks to Peter Daniels and his amp design based upon the LM3875. Right from the prompt delivery of the boards and components to the comprehensive guidance notes offered on this forum; Peter is offering a very professional service. Having read and re-read this particular thread, to try and ensure I understood enough, it is clear that he has the expertise and patience to explain the same topic over again to help anyone in difficulty.
My amplifier is now complete, hum free, and at the moment replaces my NAD 350. After checking and rechecking the DC offset I put my amp into my system, consisting of a Cambridge Audio 540, Systemdek (via Cambridge Audio 640) and KEF Q3’s. After playing Miles Davis ‘So What’ and Yes ‘Future times’ (a couple of my favourite test tracks) I swapped back to the NAD to play the tracks again. Initially I broke out in a cold sweat because the KEF’s now sounded like they had socks over them and I thought I had damaged them with my new amp! I guess that illustrates the difference, as far as I am concerned.
I intend to pull together some of my experiences in building my version of Peter’s amp and post on this forum. I hope that it will help some other potential newbie to jump in and try their skill.
Cheers
Jeff
Well mrsbadcrumble , I agreed with you. Peter Daniel is one of the many members here that is willing to help people in this forum as much as He can. I have read a lot of his posts and let me tell you...He has a lot patience and knowledge. I build one LM3875 integrated amp(from Audiosector)using premium parts and the only thing I can say is, I can not be any happier.
roger_lew said:
That's why it is often recommended to have an input coupling capacitor instead of using DC coupling from the signal source (iPod, preamp, etc) to the amplifier. Generally a value of 1 to 5uf non-polarized will work. I used cap's rescued from a speaker cross over unit. The use of a capacitor in series with the grounded resistor from the inverting input (Ci) will also perform a similar function by cutting off the gain of the amplifier for DC. The value here should be 20-100uf NP, though since the DC voltage at this point is zero an electrolytic will work with the (+) end to ground. These extra capacitors are not in the original Gaincard circuit or in Peter's kits (they are in the National Semi reference design). The amplifier works without them, except when you have an input failure (as you found out the hard way).
Hi,
I am a beginner and I built my chipamp using the Audiosector kit and following the instructions in this thread. There were a number of choices proposed by Peter, I just followed the standard proposal that also was the one with minimum parts (no 4.7 microF capacitor at input and no R1 resistor)
I connected the amp to a passive pre I also built, again very simple: selector +attenuator (all grounds of input signals and attenuator connected to a chassis ground).
I have a problem related with the input source I am not able to solve, maybe related with your last posts which honestly I am not able to follow.
Everything is working fine when I use as source a cdplayer, a turntable via phono pre I also built) and an IPOD (I could also test directly connected to the amp).
But when I connected my Mac Powerbook Laptop to the pre via the headphone jack I got a loud noise from the speakers. I quickly disconnected the laptop and I never tried again.
Do I need to put the suggested input caps of 4.7microF at the input of the amp?
Thank you for your help
Renato
I am a beginner and I built my chipamp using the Audiosector kit and following the instructions in this thread. There were a number of choices proposed by Peter, I just followed the standard proposal that also was the one with minimum parts (no 4.7 microF capacitor at input and no R1 resistor)
I connected the amp to a passive pre I also built, again very simple: selector +attenuator (all grounds of input signals and attenuator connected to a chassis ground).
I have a problem related with the input source I am not able to solve, maybe related with your last posts which honestly I am not able to follow.
Everything is working fine when I use as source a cdplayer, a turntable via phono pre I also built) and an IPOD (I could also test directly connected to the amp).
But when I connected my Mac Powerbook Laptop to the pre via the headphone jack I got a loud noise from the speakers. I quickly disconnected the laptop and I never tried again.
Do I need to put the suggested input caps of 4.7microF at the input of the amp?
Thank you for your help
Renato
Lets make few things clear, Andrew:
This is not your average amplifier project directed at the beginner.
This is heavily tweaked amplifier with a main goal to provide best sonic reproduction given available resources.
The omission of input coupling cap and gain setting resistor cap is INTENTIONAL and I made conscious decision to offer the project this way. Of course, I had my doubts regarding responsibility aspects of such endeavor, however, perfect track record since 2003 (when the kit was first offered), confirms that such doubts were unsubstantiated.
Certainly, I advise to use coupling cap with unreliable sources: http://www.diyaudio.com/forums/showthread.php?postid=1508778#post1508778
and I couldn't stress it more that whenever new source is connected, you need to first check the DC offset before connecting any speakers: http://www.diyaudio.com/forums/showthread.php?postid=1521304#post1521304
Given the tweaked nature of such design and the attempt to create the best sounding amp in a specific product category, it is not really advisable to connect the ipod there However, if you really need to do it, use coupling caps .
This is not your average amplifier project directed at the beginner.
This is heavily tweaked amplifier with a main goal to provide best sonic reproduction given available resources.
The omission of input coupling cap and gain setting resistor cap is INTENTIONAL and I made conscious decision to offer the project this way. Of course, I had my doubts regarding responsibility aspects of such endeavor, however, perfect track record since 2003 (when the kit was first offered), confirms that such doubts were unsubstantiated.
Certainly, I advise to use coupling cap with unreliable sources: http://www.diyaudio.com/forums/showthread.php?postid=1508778#post1508778
and I couldn't stress it more that whenever new source is connected, you need to first check the DC offset before connecting any speakers: http://www.diyaudio.com/forums/showthread.php?postid=1521304#post1521304
Given the tweaked nature of such design and the attempt to create the best sounding amp in a specific product category, it is not really advisable to connect the ipod there
However, if you really need to do it, use coupling caps .My Peter Daniel gainclone is slowly coming together and I wanted to share one solution I found for the power switch. To start with I really wanted to use one of the Bulgin illuminated switches because I really like the way they look. But, they presented a problem because I would need some sort of latching circuit to power the amp. After a very quick search here I found a circuit that was specifically made for this switch. It may not be the most cost effective solution but it's a very nice design all in one very neat package. I've ordered a couple and will report back later. Here's the link to the power switch driver circuit.
Regards,
Dan
Regards,
Dan
The negative effects of both the input coupling and gain setting resistor caps depend on the quality of those caps and their value. In the case of the gain setting cap, the use of two (or even THREE) different sized caps in parallel can help. Polyprop type caps are the best choice, but in the value required they are large and expensive. An input coupling cap of about 4uf will not reduce the low frequency response in the range above the cutoff of the largest subwoofers. Paralleling a .1uf polyprop would be a good idea. The use of an input coupling cap can reduce or eliminate the 'poping sound you might hear when a source is turned on/off while the amp is powered on. It also protects your amp/speakers from any DC offset injected from an audio source.
If the cap in the gain setting position is used a value of at least 22uf, and as high as 100uf are common. Here a polarized electrolytic can serve, but it should be a high quality cap. A defective electrolytic cap can act as a battery and produce DC offset rather than eliminate it! Some recommend the use of a non-polarized cap, or two polarized ones connected back to back (with like polarities together). Here you need to use double the total required value for each capacitor. Also bypass the cap with a .1 uf polyprop.
If you do decide to add a capacitor at either position compare the sound with and without each capacitor. If you can't hear the difference, (with some speakers, source material, etc you won't) then you might as well leave them in. IF you do hear a negative difference, then leave them out, but understand what their purpose is. For those that consider any coupling capacitor a bad idea, remember that you have such capacitors in the cross over network of your speakers.
History:
Some of the amplifiers and receivers made by the company I work for have had a crowbar circuit that would shut down the amplifier if an excessive DC offset was detected at the speakers. We had a rash of customer returns on an amplifier that was blowing fuses. This was caused by the crowbar circuit firing, and the reason was traced to a batch of defective capacitors that caused the DC offset by acting as batteries. (The problem no longer exists, we now are using a different capacitor supplier!).
If the cap in the gain setting position is used a value of at least 22uf, and as high as 100uf are common. Here a polarized electrolytic can serve, but it should be a high quality cap. A defective electrolytic cap can act as a battery and produce DC offset rather than eliminate it! Some recommend the use of a non-polarized cap, or two polarized ones connected back to back (with like polarities together). Here you need to use double the total required value for each capacitor. Also bypass the cap with a .1 uf polyprop.
If you do decide to add a capacitor at either position compare the sound with and without each capacitor. If you can't hear the difference, (with some speakers, source material, etc you won't) then you might as well leave them in. IF you do hear a negative difference, then leave them out, but understand what their purpose is. For those that consider any coupling capacitor a bad idea, remember that you have such capacitors in the cross over network of your speakers.
History:
Some of the amplifiers and receivers made by the company I work for have had a crowbar circuit that would shut down the amplifier if an excessive DC offset was detected at the speakers. We had a rash of customer returns on an amplifier that was blowing fuses. This was caused by the crowbar circuit firing, and the reason was traced to a batch of defective capacitors that caused the DC offset by acting as batteries. (The problem no longer exists, we now are using a different capacitor supplier!).
northernsky said:
Hi Renato,
just a guess: Did you plug in your MacBook via headphone plug while the amp was powered ON? - If so, please, NEVER do it like that! A 3,5mm headphone jack has three contact plates: left channel (on top), right channel (middle) and ground. When you plug in this jack, the left and right channel plates do have contact BEFORE the ground contact has been made. And without this you get a loud hum and you are probably going to destroy your amp and/or speakers.
Ok. So, if you have some hissing noise when the MacBook is connected to the amp and everything else is working properly, that's ok, because you are then listening to a headphone amplifier as source, and these things have some hiss or white noise sometimes. (That's only ONE reason why we are all so fancy about those nice and affordable USB-DACs ;-)
Regards
martin
That's the sort of reasoned response I expect to see.kscharf said:
It informs the reader of the pros and cons.
The reader can now make an informed decision.
I wish there were more of you prepared to explain where your viewpoint comes from and why you believe in certain values.
A categoric:
"this is the best Chipamp ever"
is unhelpful, if the information that it could be a speaker destroyer is deliberately hidden from the uninitiated.
I build the LM4780 parallel kit.
This amp may be used for party with variety of sources, including pcs. To be safe, I understand that I should put input coupling caps.
1. can I solder the cap right on the RCA signal input connector ?
2. would this cap make it ? http://www.wima.com/EN/mks2.htm
This amp may be used for party with variety of sources, including pcs. To be safe, I understand that I should put input coupling caps.
1. can I solder the cap right on the RCA signal input connector ?
2. would this cap make it ? http://www.wima.com/EN/mks2.htm
I'm still awaiting the arrival of some parts I ordered. I figure sometime next week my transformer should show up [Antek AN-3222] and an order I placed with partsconnexion for the doodads like wire, RCA jacks, binding posts etc. taking advantage of their 20% off sale.
A question? Since everything was reasonably priced I rounded out the partsconnexion order with a couple of Black Gate 50V 470uf "F" polarized capacitors. I thought I'd use them on the amp board and put the Panasonics 1500uf's on the power supply. The "N" type no longer are available in suitable voltage so I went for the F which had some NOS arrive. Is this a suitable capacitor?
I also dragged out of my tool supply a cheap digital multimeter I bought a while back for working on my car and re-familiarized myself with it. On the DC side the lowest setting is 200mv which I assume would be reasonably adequate for measuring DC offset with each new connected source?
Another question.
What would be a good wire choice to carry the DC current from the rectifier board which will be with the transformer in a seperate case, I figure about a 24" distance between cases. I heard all kinds of reference to signal wire [I bought some Mundorf PTFE shielded silver/gold wire for signal 24 awg, hey...it was on sale!!! LOL!] but not too much on suitable wire for carrying the DC. I estimate 34ish volts on that 2-foot trip? Nothing too fancy required I assume. I also bought some DH Labs 18 awg hook-up wire. This good for the DC umbilical?
Thanks for your responses.
A question? Since everything was reasonably priced I rounded out the partsconnexion order with a couple of Black Gate 50V 470uf "F" polarized capacitors. I thought I'd use them on the amp board and put the Panasonics 1500uf's on the power supply. The "N" type no longer are available in suitable voltage so I went for the F which had some NOS arrive. Is this a suitable capacitor?
I also dragged out of my tool supply a cheap digital multimeter I bought a while back for working on my car and re-familiarized myself with it. On the DC side the lowest setting is 200mv which I assume would be reasonably adequate for measuring DC offset with each new connected source?
Another question.
What would be a good wire choice to carry the DC current from the rectifier board which will be with the transformer in a seperate case, I figure about a 24" distance between cases. I heard all kinds of reference to signal wire [I bought some Mundorf PTFE shielded silver/gold wire for signal 24 awg, hey...it was on sale!!! LOL!] but not too much on suitable wire for carrying the DC. I estimate 34ish volts on that 2-foot trip? Nothing too fancy required I assume. I also bought some DH Labs 18 awg hook-up wire. This good for the DC umbilical?
Thanks for your responses.
Hi Martin,
thank you for your reply.
Connection was done with the amp switched off (being honest sometime in the past I forgot the amp switched on and I tested myself what can happen).
But what I here is not just a hiss, but a loud noise at the same volume of the music.
I should try by adding the input cap at the amp. However my DMM does not measure any DC at the headphone Mac output.
Anyway the standard sources for the amp are a Meridian CD player and a Rega turntable, the amp should have a good company as Peter wishes.
Renato
My transformer came in today, Antek AN-3222, far sooner than expected. Doing this transaction with John Ango at Antek was a totally awesome experience. Awesome price, excellent communication, shipped the next day via Priority Mail with tracking number, and considering it had to travel 3 thousand miles plus cross an international border it arrived in lightspeed fashion. If you are in Canada, the bonus that is only a $36 purchase price puts at under $40 where no duties, customs fees or taxes apply, ensuring that it zips right through customs, if shipped by mail. My total cost to my door including shipping was $71 CAD out of my PayPal account. Way to go John!
...and let me telll ya, this thing is HUGE! HUGE I tell ya! So far, so good...
...and let me telll ya, this thing is HUGE! HUGE I tell ya! So far, so good...
passive pre
Can someone tell me what I need to pay attention when connecting passive pre to GC mono blocks?
I still haven't made passive, so I need an advice.
I'm waiting for TKD pot,I have Lorlin CK rotary switch(4 pole,3 pos).
If you have interesting links where I can buy quality case for preamp,I will be grateful.
Can someone tell me what I need to pay attention when connecting passive pre to GC mono blocks?
I still haven't made passive, so I need an advice.
I'm waiting for TKD pot,I have Lorlin CK rotary switch(4 pole,3 pos).
If you have interesting links where I can buy quality case for preamp,I will be grateful.