...you guys must be fed up seeing that title. 
This is was one hell of a buzz. I can't believe I built an amplifier. yay to me.
I used old parts where possible, so this one channel has cost < £10. I followed the NS schematic more or less. It's an absolute mess but it works fine. There is the slightest hum that can be heard only when my ear is put right near the woofer, but I'm hoping that will go once I sort all the wiring up and fix everything in place. I recall measuring the DC offset to < 4mV which looks too good to be correct?
I was somewhere between pessimistic and realistic in my expectations, and although I won't claim some superioior GC sound (well those caps must be 15 years old to begin with) I must say I am impressed.
I've heard a few tracks, and I feel there is an ever so slight lack of bass (but then again I'm listening on a pair of JBL control 1's at the moment) but the midrange already seems to outdo my midfi mini system. I could hear digitization effects in one (poorly compressed) mp3 track which I'd never picked up on before, and I made out some new sounds in another that I'd never really noticed before. The last time I experienced this was when hearing a pair of Logan ESL's for the first time.
Cheers to Nuuk in particular. Your site is a GC newbie's best friend
This is was one hell of a buzz. I can't believe I built an amplifier. yay to me
. I used old parts where possible, so this one channel has cost < £10. I followed the NS schematic more or less. It's an absolute mess but it works fine. There is the slightest hum that can be heard only when my ear is put right near the woofer, but I'm hoping that will go once I sort all the wiring up and fix everything in place. I recall measuring the DC offset to < 4mV which looks too good to be correct?
I was somewhere between pessimistic and realistic in my expectations, and although I won't claim some superioior GC sound (well those caps must be 15 years old
to begin with) I must say I am impressed.I've heard a few tracks, and I feel there is an ever so slight lack of bass (but then again I'm listening on a pair of JBL control 1's at the moment) but the midrange already seems to outdo my midfi mini system. I could hear digitization effects in one (poorly compressed) mp3 track which I'd never picked up on before, and I made out some new sounds in another that I'd never really noticed before. The last time I experienced this was when hearing a pair of Logan ESL's for the first time.
Cheers to Nuuk in particular. Your site is a GC newbie's best friend
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Tee hee - there is no escape from the Decibel Dungeon! 
Well done Vikash and welcome to the club.
May I suggest replacing those old caps when you can as they are probably more important in the GC design than some other amps where there is more capacitance.
And thanks for all your kind comments on DD. I hope to be adding some new stuff on GCing very soon now.
Well done Vikash and welcome to the club.
May I suggest replacing those old caps when you can as they are probably more important in the GC design than some other amps where there is more capacitance.
And thanks for all your kind comments on DD. I hope to be adding some new stuff on GCing very soon now.
At present, the caps are 5600uF. I've seen small value caps placed close to the pins of V+ and V- (in addition to the smoothing caps). What is the purpose of this? Are they used when the PSU caps are far away?Nuuk said:
Also, I found a difference when putting a 22uF cap close to pin 8 (and the resistor afterward). What is the name of function of this cap (I know it's not a smothing or snubber cap etc.)?
Lastly, I haven't the faintest idea what the resistors I've used are rated at. Is there a minimum requirement for any of them?
Nuuk, I have a few suggestions about your GC FAQ which you may want to take on board. Perhaps I will email you a list of the things that wern't obvious to me which may help others too...
The 1000 uF caps are generally recommended because that level of capacticance has been found to give the best sound by most GC builders.
Some argue for more but it is felt that higher values 'slow' down the sound or affect the tonal balance.
Except for the 0.22 R on the output (if you use one), the other resistors can be 0.125 watts. I suggest a minimum of 3 watts for the 0.22R.
Yes, please contact me (use the form on DD) with any suggestions for the FAQ page.
Some argue for more but it is felt that higher values 'slow' down the sound or affect the tonal balance.
Except for the 0.22 R on the output (if you use one), the other resistors can be 0.125 watts. I suggest a minimum of 3 watts for the 0.22R.
Yes, please contact me (use the form on DD) with any suggestions for the FAQ page.
I'll let you know about the capacitance when my GC4s are complete.
GC1 & 2 - 5600uF on a seperate supply followed by 1000uF at the rails. This was to reduce the indution of 50Hz by the umbilical cords.
GC3 - 1000uF at rails only (Tube buffered)
GC4 - 10000uF at PSU + 1000uF at rails. Same chassis.
I have tended to find that the extra capacitance on the PSU and th compulsary 1000uF at rails sounds best. Not "slow" or adversly affected in the least. I am yet to listen to my nearly completed GC4s so I can't comment when the PSU is in the same chassis. See my website for details. I should note that all of these designs are monoblocks.
Gaz
GC1 & 2 - 5600uF on a seperate supply followed by 1000uF at the rails. This was to reduce the indution of 50Hz by the umbilical cords.
GC3 - 1000uF at rails only (Tube buffered)
GC4 - 10000uF at PSU + 1000uF at rails. Same chassis.
I have tended to find that the extra capacitance on the PSU and th compulsary 1000uF at rails sounds best. Not "slow" or adversly affected in the least. I am yet to listen to my nearly completed GC4s so I can't comment when the PSU is in the same chassis. See my website for details. I should note that all of these designs are monoblocks.
Gaz
Ok, the first version doesn't even have a case on it, and I'm already looking into the next one. My bro has asked me to build him one already. He wasn't taking it seriously while I was making this one, but within 10 minutes of listening to it (in mono ) he's asked me to build him one to replace is cambridge audio.
Have any of you UK lot purchased BrianGT's kits? I think it's mighty convenient to have nice looking boards and all the components picked out for £25 delivered, but just wanted some of your opinions...
) he's asked me to build him one to replace is cambridge audio.Have any of you UK lot purchased BrianGT's kits? I think it's mighty convenient to have nice looking boards and all the components picked out for £25 delivered, but just wanted some of your opinions...
I agree, considering the hassle of buying electronic components in the UK these days, that's a very tempting offer!
The design was well thrashed out and so many people have built them, I think that is testomy in itself!
I know of a guy in the UK who is bringing out a kit (or told me he was a little while ago) and Fedde (in Holland) was also going to offer a kit (or at least PCB's and chips) but I think he got side-tracked by a new job!
So I would say go for it but like you, I think that it would be interesting to hear the experiences of any UK builders.
Still very provisional, as due to burglary at home everything has been set back a while...
However, it will be a fairly experimental ported isobarik, current sims seem to suggest about a 8/10L box tuned to about 55Hz, crossing over to a Turbosound branded Audax tweeter at about 3-3.5K
There may be more details in the Maplins Close-out thread, I can't remember!
Once work gets properly underway I hope to start a construction log somewhere, probably as a thread as I have no useable web space anywhere at the moment.
However, it will be a fairly experimental ported isobarik, current sims seem to suggest about a 8/10L box tuned to about 55Hz, crossing over to a Turbosound branded Audax tweeter at about 3-3.5K
There may be more details in the Maplins Close-out thread, I can't remember!
Once work gets properly underway I hope to start a construction log somewhere, probably as a thread as I have no useable web space anywhere at the moment.
Can this be chased up? I may even consider just buying lots of boards from Brian, and sourcing the components from here (see last paragraph).Nuuk said:
They are available to order on his site, unless you're waiting for premium kits?D1GGY said:
RE: Audax build.
If I want to use active crossovers what would be the best way to go about it? Would it be feasible to use one psu (per enclosure) then three amps (one each for mid, bass and tweet duties) running of it?
Its seems I will be making many of the amps in the future, so there may yet be advantage in buying components (in quantity) from the UK. But where can I source good quality components (such as those caddock resistors, BG caps) in the UK? Or can you suggest alternative premium lables that can be found over here?
You will certainly notice a different with some component prices when ordering in higher quantities. The MUR860 diodes being a good example!
BG caps? I would say that the extra cost for the BG decoupling caps is very hard to justify over the Panasonic FC type. For DC blockers, I would prefer a polypropylene film type to a BG. (I sed BG NXQ's on my mononblocks as I had some to hand and space was at a premium).
For 'exotic' parts in the UK, try the
Hi-Fi collective .
I prefer Antrim transformers from Maplin.
Most 'ordinary parts I get from Farnell (but I am not happy with the new 20UKP minimum order).
My polypropylene caps come from CPC .
I like a mixture of resistor types with Welwyn RC55 (Farnell) for the feedback caps and carbon types for the input duty.
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