*** The DIY Audio Thread ***
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Associate
Only 4 x 1000uF, that is what I had left in my parts box.
You pre-amp looks ace! I need to get my fronts of my enclosures sent off to get engraved properly. Maybe recess the knobs too.
I think my next project is an integrated amp using the SOAP MKIII pre-amp with the LM3875 chip amp. But have to save up
Associate
To be honest this is the first amplifier I have made. But looking at BrianGT's LM1875 kit at chipamp.com they have 2x1500uF so I went for a similar value. I never notice a problem with the bass handling of the amplifier, in fact the bass is quite good for a 20W amp.
Also I have seen LM3875 kits with 1500uF as well. Seems to do the job. But I am still learning and might tweak values in future builds.
Also I have seen LM3875 kits with 1500uF as well. Seems to do the job. But I am still learning and might tweak values in future builds.
Soldato
Adam, could you explain what's going on in your pre-amp? Is there some sort of amplification going on in there as well as the fancy source selction etc?
no probs,
Its an R2r volume control, so the output impedance is slightly too big to feed my valve amp, so i have added a unity gain buffer.
If you put a buffer in front of a volume control, the control's low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower, and that is what i have done. It also means it can ignore the capacitance of the interconnects (some people say it can drive leads..)
The large circuit board in the middle is a shunt regulator to feed the buffers. The buffers are based on a 2sk170 jfet, which is known to be one of the most transparant fets made.
The circuit on the left (on the side wall) is a regulated 5vdc power supply for the vol and source selector.
Caps near the top right are to block any DC.
Its an R2r volume control, so the output impedance is slightly too big to feed my valve amp, so i have added a unity gain buffer.
If you put a buffer in front of a volume control, the control's low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower, and that is what i have done. It also means it can ignore the capacitance of the interconnects (some people say it can drive leads..)
The large circuit board in the middle is a shunt regulator to feed the buffers. The buffers are based on a 2sk170 jfet, which is known to be one of the most transparant fets made.
The circuit on the left (on the side wall) is a regulated 5vdc power supply for the vol and source selector.
Caps near the top right are to block any DC.
Founder_film, that looks great! I've lost track of the thread a bit, looks like a TDA2030 or LM1875 based amp? They are great little chips, I built a compact amp with them but they were on stripboard and badly grounded, thus a connection mistake eventually destroyed them
Glad your home etching worked out! Have to say my attempts never did, even with big connections
. Here's what I do for my PSU boards:
Copper clad board; to make breaks I score 2 lines against a steel rule with a sharp knife and peel out the small strip with tweezers (tricky but once you've started it, it'll peel!). Only good for simple boards, this has an offboard bridge but I could have incoporated a discrete schottky bridge just about. Yes, I cleaned it before soldering
Adam W, nice job! Looks like a similar case to Founder_film? Not certain what you have in your box, I'm guessing the back PCB is an input selector combined with relay ladder attenuator? The blue PCB is a headphone amp? The 2 small PCBs I'm not certain on, some kind of headphone level adjustment? Out of interest, how do you drill the large diameter holes for those recessed phono sockets? I admit I used flat wood bits when I've needed to do them, gives a suprisingly good result but they sure complain about it (alu only!)
I know it's hard to do without ground loops but when using these toroid transformers you should earth the secondaries too (circuit earth) to protect against the risk of a primary to secondary insulation breakdown. E-cores are often double insulated (box inside a box symbol) but toroids rarely are, by nature thier insulation is poorer (it's basically insulation tape!). Also, it looks as though the case panels won't make great electrical contact with each other, check with a MM and if they are temperemental you should add another earth connection to each panel. In mine I used earth loop breakers and suprisingly my panels do make contact (even with black coloured/coated bolts!). See here if you're concerned:
http://sound.westhost.com/earthing.htm
It's only advice, often it's just too hard to do properly. Personally I'm not that concerned if it's only me using it, I'm only worried about it possibly hurting someone else (and of course you'd get in trouble if it did!).
Glad your home etching worked out! Have to say my attempts never did, even with big connections
. Here's what I do for my PSU boards:
Copper clad board; to make breaks I score 2 lines against a steel rule with a sharp knife and peel out the small strip with tweezers (tricky but once you've started it, it'll peel!). Only good for simple boards, this has an offboard bridge but I could have incoporated a discrete schottky bridge just about. Yes, I cleaned it before soldering
Adam W, nice job! Looks like a similar case to Founder_film? Not certain what you have in your box, I'm guessing the back PCB is an input selector combined with relay ladder attenuator? The blue PCB is a headphone amp? The 2 small PCBs I'm not certain on, some kind of headphone level adjustment? Out of interest, how do you drill the large diameter holes for those recessed phono sockets? I admit I used flat wood bits when I've needed to do them, gives a suprisingly good result but they sure complain about it (alu only!)
I know it's hard to do without ground loops but when using these toroid transformers you should earth the secondaries too (circuit earth) to protect against the risk of a primary to secondary insulation breakdown. E-cores are often double insulated (box inside a box symbol) but toroids rarely are, by nature thier insulation is poorer (it's basically insulation tape!). Also, it looks as though the case panels won't make great electrical contact with each other, check with a MM and if they are temperemental you should add another earth connection to each panel. In mine I used earth loop breakers and suprisingly my panels do make contact (even with black coloured/coated bolts!). See here if you're concerned:
http://sound.westhost.com/earthing.htm
It's only advice, often it's just too hard to do properly. Personally I'm not that concerned if it's only me using it, I'm only worried about it possibly hurting someone else (and of course you'd get in trouble if it did!).
Associate
Founder_film, that looks great! I've lost track of the thread a bit, looks like a TDA2030 or LM1875 based amp? They are great little chips, I built a compact amp with them but they were on stripboard and badly grounded, thus a connection mistake eventually destroyed them
Glad your home etching worked out! Have to say my attempts never did, even with big connections
Copper clad board; to make breaks I score 2 lines against a steel rule with a sharp knife and peel out the small strip with tweezers (tricky but once you've started it, it'll peel!). Only good for simple boards, this has an offboard bridge but I could have incoporated a discrete schottky bridge just about. Yes, I cleaned it before soldering
I saw your method of making a PSU board earlier in the thread. Seems nice fool proof way of doing it. Luckily my etch board worked out. Going to modify the design a bit though to accommodate larger capacitors. But for now it works fine and sounds really good.
Yes its a LM1875. Fits in a very small case, and now I have a new PSU board I could add a volume pot to the front instead of having a separate passive pre amp.
Soldato
What exactly does the R2R ladder do? I'm familiar with their use in a flash ADC: does yours simply give the volume to a digital value for display on the LCD?
How much did effect did the buffer have on the sound quality? I know you say that particular JFET is very transparent, but could you tell any difference?
Also, are the coupling caps "Sonicaps"? I've seen them a few times, they seen pretty popular but quite large...!
Edit: just spotted your post on HeadFi. Looks like they are Sonicaps.
How did I miss this!? I must have taken ages writing my post out!
I've been looking at shunt regulators too, for when I eventually build my active crossover. It might be excessive with just unity gain and the high PSRR of op-amps, but many claim it sounds better. Where did you get your 2SK170's from? They are also used in this design(s) I'm looking at:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=143693
It's getting some real attention now with PCBs being made up. Is your one a kit, the PCB looks very professional, I assume it's dual polarity?
Dr. Em,
If you needs 2sk170's drop me a line, i have been busy created matched quads and pairs to sell.
the shunt regulator is from diyzone (china), and i am afraid i do not think they are for sale anymore. There was a group buy for cetoole regs on diyaudio, but development seems to have gone wayward.
Just had a look at the salas reg, if PCB's come available can you contact me, i wouldnt mind a few.
If you needs 2sk170's drop me a line, i have been busy created matched quads and pairs to sell.
the shunt regulator is from diyzone (china), and i am afraid i do not think they are for sale anymore. There was a group buy for cetoole regs on diyaudio, but development seems to have gone wayward.
Just had a look at the salas reg, if PCB's come available can you contact me, i wouldnt mind a few.
The R2r ladder is the actual attenuator, relays just drop resistors into the signal to control the vol, reputed to be much 'cleaner' than a pot.
With regard to the buffers, yes i did notice a difference, bass and the really highs (air..) improved. IT isnt night and day but if i take them out i start to notice it sounding a bit rolled off in the highs.
sonicaps are small compared to a lot of PIO or oil caps. I normally use obbligato's, they are MASSIVE
Soldato
Balls, diyaudio appears to be down, anyone know when it's gonna be back up?
Once again, not quite up to the standard of the rest of the people on here, however I have knocked up a cable for my new sub as the supplied one was not suited to work on my hi-fi as it needs to be connected at the speaker end rather than the back of the amp. Modifed the F-connectors so I could solder the wires in place at the speaker end. Amazingly it worked and didn't short anything out or melt my amp!
A quick mains cable to go with my sub.
Dave
A quick mains cable to go with my sub.
Dave
Soldato
how safe are these diy power cables and what improvements do they offer or the free ones we get with our equipment?
I haven't tried the power cable out yet but the sub cable is working fine, no real improvement as I couldn't use the supplied cable as it was too short and I couldn't find anywhere that made one desinged to connect at the back of the speakers. The sub cable cost just under a tenner to make.
Not used the mains cable yet, want to get it set up with the standard lead first. Its a bit of Belden shielded cable (can't remember the model no.), a Wattgate and a MK plug, total cost of about 40 squid.
I was pleased with the improvment gained from the hydra I built a few months ago and decided to knock a cable up for the sub as well. Much better and cheaper than the russ andrews mains block and power cords I had before. I'm not going to start a debate on cables as its been done to death on here. Have a search though the rest of rest of the threads in this area of the forum if you want.
Dave
Not used the mains cable yet, want to get it set up with the standard lead first. Its a bit of Belden shielded cable (can't remember the model no.), a Wattgate and a MK plug, total cost of about 40 squid.
I was pleased with the improvment gained from the hydra I built a few months ago and decided to knock a cable up for the sub as well. Much better and cheaper than the russ andrews mains block and power cords I had before. I'm not going to start a debate on cables as its been done to death on here. Have a search though the rest of rest of the threads in this area of the forum if you want.
Dave
Soldato
will have read posts about speaker and videocables but never psu cables.
If I was looking at taking my first steps into the world of DIY Tube/Valve amplifiers, and wanted an "all-in-one" kit (or as close to one as you can get), where would I go about buying one online in the UK?
All I can seem to find is Tube Depot over in the US, is there someone over here that sells what I'm after?
All I can seem to find is Tube Depot over in the US, is there someone over here that sells what I'm after?