Some guys I know at work who have had stuff done in the past say it would only be a few quid to have it done (the anodising).
The build quality of the case is pretty decent, there is a fold at the front edge on the top and bottom to give them some rigidity and they are also reasonably think, however, I am considering applying some damping sheets to the top and bottom just to take the ring out of them. What is nice about the side panels is that they are designed to take M4 nuts so that you can attach ICs without having to drill the heatsink. I did drill it so I could get a bolt all the way through, as it didn't suit the mounting arrangement I wanted. Overall I am pleased with the result.
The build quality of the case is pretty decent, there is a fold at the front edge on the top and bottom to give them some rigidity and they are also reasonably think, however, I am considering applying some damping sheets to the top and bottom just to take the ring out of them. What is nice about the side panels is that they are designed to take M4 nuts so that you can attach ICs without having to drill the heatsink. I did drill it so I could get a bolt all the way through, as it didn't suit the mounting arrangement I wanted. Overall I am pleased with the result.
ianpengelly said:
Not bad at all! Did you e-mail the place where you got the case from and ask about a black front? Perhaps in the future this might be an option if the demand is big enough. All my audio stuff is black at the moment, so I would probably prefer black too.
That sounds good! I've used old (quite large) PII computer heatsinks for mine, which... aren't attached to the case at all. Mine gets rather toasty in there, but the thermal protection hasn't kicked in even at absolute max volume so I don't really think I have any thing to worry about really
So you should be, it looks very nice indeed, and my rather short memory is telling me you said it also sounds nice (which is argueably(sp) much more important of course)
ianpengelly said:
How much did you end up spending on it all in total? I actually ended up spending about £150 on mine. Not too bad really I suppose (I did buy some parts which I ended up not wanting to use too, I am very indecisive!). I could have bought another commercial made amp, but I wouldn't have had the fun of building something myself doing that of course
Are you designing the preamp from scratch, or have you found a kit / schematics to use? I remember reading that "carlosfm" made a preamp or something using the OPA627 (I think), and he seemed to love it!
I shall be building what looks to be a fairly simple preamp (P88 from Rod Elliots site) soon too, given the success of the GainClone experiment
I look forward to seeing / reading about your preamp when it's done!
I would like to do something based around the OPA627, as it seems to consistently get good writeups. I would expect to use it as a buffer, so I may have to look for CarlosFM's example. What I may do is get hold of a couple more of the power supply boards (same as the chipamp kit design) and use those to feed a regulator and then the preamp, keeping dual mono as much as possible.
As for how much it cost, I think in the £150 region as well and compared to the £1300 integrated and power amp combo I am currently using my jaw was on the floor. I expect that adding the preamp in place of the integrated (in pre mode) will be even more impressive, though I'll miss the remote source selection and volume control. Thinking about some of the improvements, such as how tight the bass is, is no surprise when you consider how short the signal path is.
I am very pleased I set out on this little experiment, though I have a fear now that there is no going back... not without a lot of money!!
As for how much it cost, I think in the £150 region as well and compared to the £1300 integrated and power amp combo I am currently using my jaw was on the floor. I expect that adding the preamp in place of the integrated (in pre mode) will be even more impressive, though I'll miss the remote source selection and volume control. Thinking about some of the improvements, such as how tight the bass is, is no surprise when you consider how short the signal path is.
I am very pleased I set out on this little experiment, though I have a fear now that there is no going back... not without a lot of money!!
Might I suggest trying out the cheaper op amps like the TL072, NE5532, OPA2132, etc. and seeing if you like them before spending a lot more money on OPA627s. I've tried all three listed above and they're all really quite good for the price. They're drop in replacements for each other as well. The 627s will require a layout made for a single op amp package.
Brian, thanks for the suggestions, I may well look into some of the other opamps and see what is available. However, my goal is to build something i am going to be happy with for a while, I don't really have the time to be experimenting between chips etc and given that a pair of OPA627s are only going to set me back £30 and in the grand scheme of the project that isn't a lot. I will do some more reading though, just to be sure.
David, I don't know of any importers, simply because I haven't really looked. What I did find was that you (in the USA) have a greater choice than us in the UK, so hopefully, you'll be able to find something you like. Best of luck!
David, I don't know of any importers, simply because I haven't really looked. What I did find was that you (in the USA) have a greater choice than us in the UK, so hopefully, you'll be able to find something you like. Best of luck!
Banned
Joined 2002
Thanks for the compliments.
Sources are all line level. The reason for the active pre-amp is that a lot of people have stated that the LM3886 responds well to being driven with a buffer stage or low gain preamp, also that unless you are fairly cleaver with your attenuator, then there are issues of gain change of the amp when you change the volume.
My experience so far has been very good with using an active pre-amp. I may well experiment since, I have to build a passive preamp effectively and add a buffer stage, so I can see what I think before and after.
As for tone controls.....
Cheers for the suggestions!
Ian
Sources are all line level. The reason for the active pre-amp is that a lot of people have stated that the LM3886 responds well to being driven with a buffer stage or low gain preamp, also that unless you are fairly cleaver with your attenuator, then there are issues of gain change of the amp when you change the volume.
My experience so far has been very good with using an active pre-amp. I may well experiment since, I have to build a passive preamp effectively and add a buffer stage, so I can see what I think before and after.
As for tone controls.....
Cheers for the suggestions!
Ian
A tone control should be driven by low impedance and fed into high impedance to work. Thus the volume control comes first, then tone controls then directly into the LM3886 which is relatively high impedance. There is a 6dB loss in a passive tone control thus you need to bump up the gain of the LM3886 by 6 dB, nothing serious.ianpengelly said:Thanks for the compliments.
Sources are all line level. The reason for the active pre-amp is that a lot of people have stated that the LM3886 responds well to being driven with a buffer stage or low gain preamp, also that unless you are fairly cleaver with your attenuator, then there are issues of gain change of the amp when you change the volume.
My experience so far has been very good with using an active pre-amp. I may well experiment since, I have to build a passive preamp effectively and add a buffer stage, so I can see what I think before and after.
As for tone controls.....
Cheers for the suggestions!
Ian
Adding an opp amp needs another PCB, more earthing arrangements, probably another transformer and power supply and so on....
You can build your passive pre-amp directly on the control pot solder tabs, it is that simple. You want a circuit?
If you use an opamp for this purpose you can use anuthng from your junk drawer as the gain only need be 6dB and low noise expensive stuff is a total overkil. Keep in mind tht the noise source id the input og the CD, tape etc, That id the source, The preamp can be as noisless it wants to be you will have zero benefit.
\\\\\\\so buy a mediocre LM358 dual op amp for about 0,30c and Bobs your uncle - you need no more. it will not slew limit at thse levels, distortion added will be iminimal but what are you achieving, only thowing more components to a simple solution an make it difficlt - I say again want me to knock up a circuit, in maybe two minutes and you can have it going still before bedtime,
Sorry this old fart took his sleeping tables a few minutes ago and I cannot believe what rubbish I am writing, cant spell or use grammar sorry, But I will stay posted until my head and screen merges.
\\\\\\\so buy a mediocre LM358 dual op amp for about 0,30c and Bobs your uncle - you need no more. it will not slew limit at thse levels, distortion added will be iminimal but what are you achieving, only thowing more components to a simple solution an make it difficlt - I say again want me to knock up a circuit, in maybe two minutes and you can have it going still before bedtime,
Sorry this old fart took his sleeping tables a few minutes ago and I cannot believe what rubbish I am writing, cant spell or use grammar sorry, But I will stay posted until my head and screen merges.
I made a 2 + 1 config with a few trick, Just completed in on wired board and sound is beastley. I added bass eq on the two satellite speakers that would give lift to compensate roll off. Then I combined the Left and right into a sub-woofer driver with a simple low pass in the feed-back line. I took lotsa trouble to ensure that the phese between sub and atellite is not screwed up.
I get good solid thumping bass wit fast attach and smooth transision to mid/bass - very nice, is pleased. I only need master volume and sub gain to control my every pleasure.
Circuit here:
I get good solid thumping bass wit fast attach and smooth transision to mid/bass - very nice, is pleased. I only need master volume and sub gain to control my every pleasure.
Circuit here:
Attachments
Curves show it all. Satellite has slight increase in low-end. Green trace. Bass has heavier gain in the low end to compensate for loudspeaker roll-off, and black curve shows overall system performance - loud with well controlled solid bass, not boomy or like a wet fart. It does not shake the house, but it moves your hart and make your foot tap the been involentary
Thanks for all the input and suggestions, I would have got back to you sooner, but I needed to sleep after all the food I ate yesterday (Christmas is a killer for the waistline!)
I understand the implications of going active, i.e. another transformer, etc. and have these budgeted for.
The shaking head at the tone controls was simply because of the fact that I don't need or really want them, I have lived for the last 12 years without them
As I said before I haven't 100% decided what to do with the pre-amp, but I have some ideas and I'll see how I get on with it in passive mode first then with a buffer.
I would be surprised if cheap opamp chips are up to the OPA627 standard given the number of tests people have performed from this site comparing various opamps.
I understand the implications of going active, i.e. another transformer, etc. and have these budgeted for.
The shaking head at the tone controls was simply because of the fact that I don't need or really want them, I have lived for the last 12 years without them
As I said before I haven't 100% decided what to do with the pre-amp, but I have some ideas and I'll see how I get on with it in passive mode first then with a buffer.
I would be surprised if cheap opamp chips are up to the OPA627 standard given the number of tests people have performed from this site comparing various opamps.
Well, I have finally got round to making a pre-amp and I have purchased a second transformer for my chipamp, so that it runs true dual mono and hopefully solves my hum problem once and for all!
The preamp is mounted in an identical case to the power amp and I have tried to keep the signal paths as short as possible by mounted the source control and the volume pot on a bracket at the back of the case close to the input and output connections. I then used some 6mm aluminium tubing to extend the controls to the front face and the control knobs. The internal wiring is all done with the tighter wound pairs from some CAT6 network cable. I have installed a power inlet and switch such that I can add a buffer stage at a later date without having to take the whole thing apart!
The volume pot is a 100kOhm Alps Blue and the source selector is a 4 pole 6 position switch from RS Components (gold plated contacts, 2A handling) which allows me to switch both the signals and the grounds, to maintain maximum channel separation.
With CD selected as the source and the volume at all the way down the amp is completely silent, with it turned all the way up there is a slight hum that can only be heard with your head next to the speaker.
The results are a very clean sound, possible not the drive that you get when using an active preamp. I need to do some more listening with CDs, but TV played through the system sounds great!
I don't have any photos at the moment, but will try and get some this weekend.
The preamp is mounted in an identical case to the power amp and I have tried to keep the signal paths as short as possible by mounted the source control and the volume pot on a bracket at the back of the case close to the input and output connections. I then used some 6mm aluminium tubing to extend the controls to the front face and the control knobs. The internal wiring is all done with the tighter wound pairs from some CAT6 network cable. I have installed a power inlet and switch such that I can add a buffer stage at a later date without having to take the whole thing apart!
The volume pot is a 100kOhm Alps Blue and the source selector is a 4 pole 6 position switch from RS Components (gold plated contacts, 2A handling) which allows me to switch both the signals and the grounds, to maintain maximum channel separation.
With CD selected as the source and the volume at all the way down the amp is completely silent, with it turned all the way up there is a slight hum that can only be heard with your head next to the speaker.
The results are a very clean sound, possible not the drive that you get when using an active preamp. I need to do some more listening with CDs, but TV played through the system sounds great!
I don't have any photos at the moment, but will try and get some this weekend.
Well, I have been cr@p at getting photos of the pre-amp, but I have got some of my recently upgraded chip amp, which now uses two transformers as opposed to the single that I started with... its a heavy amp now! 
Also I have added a disconnecting network between the safety earths and the chassis ground points on the chipamp boards.
Will post photos tonight! I promise!
Also I have added a disconnecting network between the safety earths and the chassis ground points on the chipamp boards.
Will post photos tonight! I promise!
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