I have never made anything electrical before from scratch so I am looking at the gainclone because it is cheap and looks like the easiest way for me to start. Because of this I am hopping some of you can help guide me along the way as I collect parts (I am a broke student so any help would greatly be appreciated 
)
Would either of these transformers work work?
http://www.apexjr.com/Clearance.htm
the Primary 115V Secondary 24VCT & 14VCT looks like it would work but I am not sure.
Also I was wondering if I were to put a whole lot more V into the opamp what would happen? If I could find a way to keep it cool would it work at a higher level or do they have a limit?
Also has anyone tried powering one of these with a (I may not get this name right) fallowing down convertor? Like the one in the sunfire amp.
) Would either of these transformers work work?
http://www.apexjr.com/Clearance.htm
the Primary 115V Secondary 24VCT & 14VCT looks like it would work but I am not sure.
Also I was wondering if I were to put a whole lot more V into the opamp what would happen? If I could find a way to keep it cool would it work at a higher level or do they have a limit?
Also has anyone tried powering one of these with a (I may not get this name right) fallowing down convertor? Like the one in the sunfire amp.
Hi DJNUBZ, you have picked the right project to start your hi-fi building career and there is no shortage of good advice on this forum.
I won't comment on the transformers as they are not available in the UK. As regards other parts, there isn't a great deal of difference between using something decent and something horrible so don't rush out and buy the cheapest bits that you can find. I also have to build on a budget due to financial constraints but the cost of a couple of decent caps and resistors is nothing compared to what you can spend on the case etc!
If you are a complete beginner, then you will find my site, which is dedicated to helping people start out in DIY hi-fi, useful. Just click on the small WWW button below. There are lots of money saving tricks too.
I won't comment on the transformers as they are not available in the UK. As regards other parts, there isn't a great deal of difference between using something decent and something horrible so don't rush out and buy the cheapest bits that you can find. I also have to build on a budget due to financial constraints but the cost of a couple of decent caps and resistors is nothing compared to what you can spend on the case etc!
If you are a complete beginner, then you will find my site, which is dedicated to helping people start out in DIY hi-fi, useful. Just click on the small WWW button below. There are lots of money saving tricks too.
as far as "what would happen if you were to feed it a lot of V" if you put too much voltage to the chip, you will blow it up
maximum supply voltage for the lm3875 (the most common one used) is 84V
which means the rails have to be +/- 42V (at the absolute most), so the secondaries of the transformer should be no more than 30V
although 30V for the secondaries would still be too much for the chip, so its recommended to keep them under 24V (my transformer, which hasn't arrived yet, is 22V secondaries (taken as advice from variuos people from here)
also you won't need much cooling, the chips mounted to the case, or a small heatsink will do just fine
maximum supply voltage for the lm3875 (the most common one used) is 84V
which means the rails have to be +/- 42V (at the absolute most), so the secondaries of the transformer should be no more than 30V
although 30V for the secondaries would still be too much for the chip, so its recommended to keep them under 24V (my transformer, which hasn't arrived yet, is 22V secondaries (taken as advice from variuos people from here)
also you won't need much cooling, the chips mounted to the case, or a small heatsink will do just fine
The ApexJr Signal transformer would work but it will only give you 12-0-12 VAC, or about +/- 16 VDC (12*1.4). This will limit your power output (look in the datasheet for the LM3875 for some graphs on expected power output). The transformer is meant for 240VAC but I assume you have 120VAC line voltage (in the US).
If you're using 4-ohm speakers, this might be okay.
The Fender transformer has too high a voltage.
If you're using 4-ohm speakers, this might be okay.
The Fender transformer has too high a voltage.
Hi,as you are in amaerica, the transformer listed there will give only 12 - 0 - 12 rating (24V centre tapped), which will give you around +/-16V supply for the chip, which is just about enough (not much power from it though, only about 10 or 11 WPC from a LM3875). On the pluss side, it would definately allow enough current to run a few of these devices at thet voltage.
ok I am a little confused on something.
The site says this
(Signal 220V input BL 1752)
* Primary 230V Secondary 48VCT 7A & 28VCT 3A
or Primary 115V Secondary 24VCT & 14VCT
I understand that these are 220v and I will be putting in less V then that but I am confused on where it says Primary. What is with the 2 different versions (230V,115V)? Arnt these the rated input voltages? What am I missing?
If I use this here I will have 24V. Does that mean I have a 12+ and a 12- or will I have a 24+ and 24-? From what you are telling me I would have 12+/12-. So why can't I use the 55V fender? Wouldn't that give me 27.5+/27.5-?
The site says this
(Signal 220V input BL 1752)
* Primary 230V Secondary 48VCT 7A & 28VCT 3A
or Primary 115V Secondary 24VCT & 14VCT
I understand that these are 220v and I will be putting in less V then that but I am confused on where it says Primary. What is with the 2 different versions (230V,115V)? Arnt these the rated input voltages? What am I missing?
If I use this here I will have 24V. Does that mean I have a 12+ and a 12- or will I have a 24+ and 24-? From what you are telling me I would have 12+/12-. So why can't I use the 55V fender? Wouldn't that give me 27.5+/27.5-?
From what it says one there with it being a dual 55V, I think you are more likely to find it being a 55 - 0 - 55 transformer, which would give a fairly high +/-78V supply after rectification and smoothing. As for the Signal, I do believe that you would get +12 and -12 from the transformer, which would rise to about +16V and -16V after you had rectified the output.
the 115V/230V is the input voltage .. 115 if you're in north america, 230 if you're in europe
24VCT means 24V center tapped, +12/-12
55VCT is +/- 27.5V .. that's too much for most chips, since that needs to be converted to dc ..
and when converted it comes to ABOUT 27.5*1.4=38.5V
LM3875 has a max voltage of 84V, which is 42V rails .. 38.5 is kinda getting close to its max rated voltage ..
if you could drop the rails 2-3V then it should be allright ..
but even with the 27.5 it will most likely be ok, ALTHOUGH the sound might suffer
EDIT: just checked the apexjr site .. its dual 55V secondaries, 110VCT!!!
so no, you can't use the fender one .. sorry
24VCT means 24V center tapped, +12/-12
55VCT is +/- 27.5V .. that's too much for most chips, since that needs to be converted to dc ..
and when converted it comes to ABOUT 27.5*1.4=38.5V
LM3875 has a max voltage of 84V, which is 42V rails .. 38.5 is kinda getting close to its max rated voltage ..
if you could drop the rails 2-3V then it should be allright ..
but even with the 27.5 it will most likely be ok, ALTHOUGH the sound might suffer
EDIT: just checked the apexjr site .. its dual 55V secondaries, 110VCT!!!
so no, you can't use the fender one .. sorry
Yes, it's a bit confusing. There is only one Primary, and it is rated for 230V. What ApexJr is saying is that you could apply 115V to this primary, but it would result in half the voltage on each of the secondaries. They also suggest you not plan to get any more than the original current out of them (probably because of the wire size of the windings), so you have to cut the VA rating of the transformer in half.DJNUBZ said:
You may want to email Steve at ApexJr and see if he has anything around 48VCT instead; I picked up a few but it looks like they're out of stock now.
Just to further complicate things, the Fender is not 27.5-0-27.5
I asked Steve that question last year. It has dual 55V secondaries hence the name. I presume it could be used as 55-0-55 if you wired one half of each secondary together as a 'center tap'?
I am currently using the 115V to 24-0-24 signal transformer from Apex Jr. to run a pair of LM3875 gainclones and it works just great. No hum or anything like I have heard happens with gainclones and EI transformers.
I bought four of the signals from Steve and still have two left... for now... I'm in Calgary Canada so shipping would be quite a bit if anyone wanted one. Also, they're in very poor cosmetic shape.
When/if I get some toroidal tf's I may be able to pass on one of these to someone who wants it, since they're out of stock at Apex Jr. Anyone have any toroids to trade/part trade?
Best regards
Chris
I asked Steve that question last year. It has dual 55V secondaries hence the name. I presume it could be used as 55-0-55 if you wired one half of each secondary together as a 'center tap'?
I am currently using the 115V to 24-0-24 signal transformer from Apex Jr. to run a pair of LM3875 gainclones and it works just great. No hum or anything like I have heard happens with gainclones and EI transformers.
I bought four of the signals from Steve and still have two left... for now... I'm in Calgary Canada so shipping would be quite a bit if anyone wanted one. Also, they're in very poor cosmetic shape.
When/if I get some toroidal tf's I may be able to pass on one of these to someone who wants it, since they're out of stock at Apex Jr. Anyone have any toroids to trade/part trade?
Best regards
Chris
ok as you all know I am a super newbie when it comes to making amps.
How can I tell if I have the correct transformer? It seems like there is more then one way to look at the specs.
Like this transformer
http://www.radioshack.com/product.a...name=CTLG_010_009_003_000&product_id=273-1512
it seems like this would work (may not be the nicest). Am I right or is this actualy a -12/0/+12 transformer.
Does max amperage matter with a transformer?
If there is a site that has this information I would be more then happy if someone would post it.
How can I tell if I have the correct transformer? It seems like there is more then one way to look at the specs.
Like this transformer
http://www.radioshack.com/product.a...name=CTLG_010_009_003_000&product_id=273-1512
it seems like this would work (may not be the nicest). Am I right or is this actualy a -12/0/+12 transformer.
Does max amperage matter with a transformer?
If there is a site that has this information I would be more then happy if someone would post it.
Greetings,
The "Signal" brand transformer will work...With an important requirement. In order to obtain +/- 30 VDC will require supplying the transformer with 220Vac. This is NOT your standard house current in the US. However, almost all homes are provided with 220V at the circuit breaker box. Often that voltage is distributed to clothes driers, ovens, air conditioners and (sometimes) base board heaters. You will need to obtain the services of a qualified (licensed) electrician to determine the availability of 220Vac.
If you power any home built equipment with 220, I reccomend a double pole switch and fuse BOTH legs of the circuit at a minimum. Bear in mind, 120V is dangerous and can kill you. 220V has a greater potential for the same.
I understand your interest in the Signal tranny from Apex. I just received 2 from Steve. I will use them for multi-channel amps based on the LM3886 chip. Good Luck.
The "Signal" brand transformer will work...With an important requirement. In order to obtain +/- 30 VDC will require supplying the transformer with 220Vac. This is NOT your standard house current in the US. However, almost all homes are provided with 220V at the circuit breaker box. Often that voltage is distributed to clothes driers, ovens, air conditioners and (sometimes) base board heaters. You will need to obtain the services of a qualified (licensed) electrician to determine the availability of 220Vac.
If you power any home built equipment with 220, I reccomend a double pole switch and fuse BOTH legs of the circuit at a minimum. Bear in mind, 120V is dangerous and can kill you. 220V has a greater potential for the same.
I understand your interest in the Signal tranny from Apex. I just received 2 from Steve. I will use them for multi-channel amps based on the LM3886 chip. Good Luck.
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