Gallery, Projects and General > Gallery
A little Audio project I have virtually completed
spuddevans:
Thanks for all the comments guys.
--- Quote from: Brass_Machine on April 03, 2011, 10:51:17 AM ---Whats the silver button for under your volume control?
--- End quote ---
That button switches on a latching relay (well, an ordinary relay wired to be latching), the relay switches the power on to the main transformer and the Valve ( tube :D ) HT psu. The reason for this is to let the heaters on the valves warm up before applying the HT voltage to them ( I believe that not letting the valves warm up before applying the HT does shorten their life )
The button also has a groovy blue led in it.
--- Quote --- Motorized control? So the knob moves when you use the remote?
--- End quote ---
Yup, looks pretty groovy when it does, plus the remote can select the input as well ( I only have 2 inputs, but the controller can have up to 5 )
Thanks for looking,
Tim
bigmini:
--- Quote from: spuddevans on April 03, 2011, 07:21:42 AM ---For the last few weeks I have been working on building a HiFi amplifier, and I thought I'd share a few pics for your visual enjoyment.
<SNIPPED PHOTOS>
I still have the lid to finish off, I have to drill some cooling vent holes above where the big heatsinks are. And I also have to modify the pre-amp circuit to increase the gain (the plans give the option for 7 or 11 times gain, I choose 7 but I think I need the extra gain)
I cant tell you how it sounds as I have only hooked up just a little speaker to check if it has hum or problems, and I am very happy to report that it is as quiet as a dead mouse, even turned up full. But when doing this test I noticed that the gain is not as much as I need, so I will modify it and then test it on my main speakers.
Tim
--- End quote ---
Very nice knobs Spuddevans. If you don't mind me asking though, how did you make the splines? or did you use imperial pots with a flat and setscrew? I've been meaning to make some custom knobs myself, but the splines have me stumped. The only way I can figure to make them is by using an old pot shaft and pressing the knob on.
Bluechip:
Just get some splined knobs and machine them down to make an insert for the knobs you make?
Cheapo items. As an eg.
http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/Fasteners-Fixings/Knobs/15mm-Three-colour-mixer-knobs/64709/kw/Knobs
BTW, the flatted shafts are not always imperial sized. I got some BCD rotary switches a few weeks ago that are 6mm. flatted. Which is annoying, as the knobs I wanted to use are 1/4" fitting .... always a snag ain't there ...
Dave BC
spuddevans:
--- Quote from: bigmini on April 03, 2011, 07:29:50 PM ---Very nice knobs Spuddevans. If you don't mind me asking though, how did you make the splines? or did you use imperial pots with a flat and setscrew? I've been meaning to make some custom knobs myself, but the splines have me stumped. The only way I can figure to make them is by using an old pot shaft and pressing the knob on.
--- End quote ---
Hi Bigmini :wave: Thanks for your comments. Re the knobs, I didnt make the splines, I think only the vol pot had splines, but I just measured the OD and then bored a corresponding hole, then I bored a hole in from the bottom for a grub screw. To avoid damage on the pot I turned a little slug of brass that goes into the hole before the steel grubscrew goes in. (I remember Bogs showing that method of avoiding marring shafts with grubscrews, Thanks Bogs :thumbup: ) Because these knobs are fairly large in diameter, I was able to make the brass slug long enough that it does not fall out of the hole for the pot shaft.
--- Quote from: Bluechip on April 03, 2011, 08:07:50 PM ---BTW, the flatted shafts are not always imperial sized. I got some BCD rotary switches a few weeks ago that are 6mm. flatted. Which is annoying, as the knobs I wanted to use are 1/4" fitting .... always a snag ain't there ...
Dave BC
--- End quote ---
Aint that the truth. On this project the vol pot and the input selector switch were both 6mm, but the power switch was 1/4", but when you're making the knobs, you can just make the hole to suit the size needed.
--- Quote from: Da_Kengineer_Meister on April 03, 2011, 09:03:30 PM ---
And for the question not asked / answered.... How does it sound?
--- End quote ---
Well, truth is, I have not hooked it up to my main speakers yet as I want to adjust the gain of the preamp. I hope to make the adjustment today, and then I will bring a pair of small bookshelf speakers out to the workshop and give it a test. So sorry, the question will have to remain unanswered for a littl longer :lol:
--- Quote ---Is there an over arching plan for air-flow through the assembly? Also are there specific measures in place to reduce interferance in the cabling and selection of grounding points, etc...?
--- End quote ---
The airflow plan is as follows; as it came, the 19" rackmount case came with a series of 4mm x 2" slots (hows that for mixing standards :lol: ) on the bottom panel that span from one side to the other towards the rear of the case. As it came, the lid has no holes or slots in it except for the holes for the fixing screws.
My plan is to drill a pattern of holes directly above the 2 main heatsinks to allow the hottest air to be exhausted. My hope is that this will be enough without having to resort to forced convection, ie a fan.
If my plan fails miserably, plan B is to put in a 12v fan, but just run it on 6-8v, much quieter.
Regarding reducing interferance, I have tried to follow good audio earthing practice. I'll trace the signal from the start. The inputs have their shields connected together, and then that is connected to the batch of relays that switch the inputs via just one of the shielded cables (the others have the shield connected at one end). Then after the relay board, the signals (L+R) are wired through shielded wires (again the signal ground is connected at both ends in only one cable) to the Vol pot. Then from the pot the signals are fed into the valve preamps, but at this point the signal ground is connected to the star ground.
The signals are then wired through screened cables (screen connected only at one end) to the amp modules.
The ground from the AC power supply is also connected to the star ground, along with the ground from the valve HT psu. The grounds from the speakers are all connected to the star ground.
The star ground is the bottom plate of the case. I also routed some of the AC cables through brass channels to screen them from sensitive circuitry.
--- Quote ---Nice looking presentation...
--- End quote ---
Thankyou, glad you like it.
Tim
spuddevans:
--- Quote from: Da_Kengineer_Meister on April 03, 2011, 09:03:30 PM ---And for the question not asked / answered.... How does it sound?
--- End quote ---
And now the question is answered..............
It sounds pretty darn good :headbang: :headbang: :headbang: (well to my ears anyway)
I modified the preamp circuit, hooked up the little speakers to test, and it all went well. So I brought the amp into my office where my big speakers are (Homebuilt from plans from HiFi World - KLs9 Click here for some specs ), hooked them up with some silver plated speaker cable, connected my ipod to it, switched on and then turned it up.
I cant fully describe the sound as I am recovering from a heavy cold, and also I had to replace a tweeter in one speaker, so it needs a few hours to "bed-in" before a true judgement is made. I will say that the Bass is very well controlled and tight, but nice and deep too. The amp can be pushed all the way to the max on the vol pot without any audible distortion.
I do plan on running some audio tests with my measuring mic and some software on the pc, just to see the measured response.
Tim
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version