Yesterday the last missing parts for the tone control board arrived. So I was able to finalize it and a gave it a very brief test spin (it was already very late at night, but I just couldn't resist).
I started my test with +/- 15V to be on the safe side and just improvised interconnects to my phone and a set of mediocre headphones.
IT WORKED RIGHT AWAY! I got sound, all the pots worked as expected and I couldn't hear the slightest trace of hum, distortion or the like - even with this less than optimal setup and open housing. Seems like I got at least the very basisc right and am already looking forward to do more extensive tests.
The only problem I came across during this very brief test session was that the tone defeat didn't do anything. The relays don't click if I bridge the corresponding jumper. I'll have to further investigate. Could the +/-15V supply cause that? Maybe the voltage wasn't sufficient to trigger the relays?
I started my test with +/- 15V to be on the safe side and just improvised interconnects to my phone and a set of mediocre headphones.
IT WORKED RIGHT AWAY! I got sound, all the pots worked as expected and I couldn't hear the slightest trace of hum, distortion or the like - even with this less than optimal setup and open housing. Seems like I got at least the very basisc right and am already looking forward to do more extensive tests.
The only problem I came across during this very brief test session was that the tone defeat didn't do anything. The relays don't click if I bridge the corresponding jumper. I'll have to further investigate. Could the +/-15V supply cause that? Maybe the voltage wasn't sufficient to trigger the relays?
Ah, I think I just realized why the tone defeat wasn't working yesterday. If I read the schematic correctly, the tone defeat jumper is not be bridged, but should be connected to the front panel PCB (which I don't plan to build). On this PCB the jumper is connected to the 15V DC (+Vre) which are provided separately by the PSU for the relays. The Elektor article even mentions something like that and the labels on the the board also reflect that. Simply dropped my mind.
It was probably too late last night
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This is probably the first project that just worked right away as expected .
I finished soldering the PSU, tone control and MM/MC modules ... plugged everything in .... and it just works. AMAZING!!
Now all that's left is putting everything into the case and proper wiring.
My resumee so far is that sourcing the parts and mounting everything into a case are the most cumbersome parts. The actual building, soldering and the design are very suitable for intermediate buliders (like myself) and definitely worth the effort and price. The outcome is very convincing.
.I finished soldering the PSU, tone control and MM/MC modules ... plugged everything in .... and it just works. AMAZING!!
Now all that's left is putting everything into the case and proper wiring.
My resumee so far is that sourcing the parts and mounting everything into a case are the most cumbersome parts. The actual building, soldering and the design are very suitable for intermediate buliders (like myself) and definitely worth the effort and price. The outcome is very convincing.
I've now assembled everything into its case. Since I only built the tone board, phono stage and psu it was quite a struggle to get the wiring right. Some of the connections happen on the input and front panel boards which I don't have. I had some serious humming that was hard to track down and is always frustrating when you're in the middle of it.
The preamp stage is now dead silent - absoletely nothing. Great!
The phono stage has however a tiny little 'ssshhh' sound if I turn the volume all the way up (far louder than I would ever listen music).
Is that to be expected? I guess I wouldn't even bother if it wasn't advertised as the most silent design out there and if I wouldn't have the comparison with the preamp stage.
Adding a 1nf ceramic cap between audio ground and chassis ground had no improvement.
Are your phono stages just as silent as the preamp stage when turning the volume up all the way?
The preamp stage is now dead silent - absoletely nothing. Great!
The phono stage has however a tiny little 'ssshhh' sound if I turn the volume all the way up (far louder than I would ever listen music).
Is that to be expected? I guess I wouldn't even bother if it wasn't advertised as the most silent design out there and if I wouldn't have the comparison with the preamp stage.
Adding a 1nf ceramic cap between audio ground and chassis ground had no improvement.
Are your phono stages just as silent as the preamp stage when turning the volume up all the way?
I have a Paradise Phono stage and a JC80 pre. While the JC 80 is dead silent I can still hear some hiss when listen to Phono stage and it is normal because of the huge gain. I will build this preamplifier anyway and maybe I can compare the phono stage with the Paradise but I think a little hiss is normal…
Thanks - that helps a lot.
I've made some measurements with ARTA meanwhile and found that I also have a slight 50Hz mains hum in the phono stage. I suspect that my transformer might be just to close to the phono PCB.
Since I don't have any options to rearrange the components, I am thinking about moving the PSU components to an external box entirely.
I already found some threads here discussing external PSUs. Most of these threads agree that this would require some additional capacitance inside the original box near the DC consumers.
These threads are however rather focused an power amps and I couldn't find any information specifically on preamps.
Since the Elektor articles mention that "clean" power is not too critical to the design and I am not planning on running lengthy cables between the boxes, I wouldn't have expected serious issues. I would just like to get some space and an additional metal barrier between the PSU and gain stages.
How would you go about outsourcing the PSU?
I've made some measurements with ARTA meanwhile and found that I also have a slight 50Hz mains hum in the phono stage. I suspect that my transformer might be just to close to the phono PCB.
Since I don't have any options to rearrange the components, I am thinking about moving the PSU components to an external box entirely.
I already found some threads here discussing external PSUs. Most of these threads agree that this would require some additional capacitance inside the original box near the DC consumers.
These threads are however rather focused an power amps and I couldn't find any information specifically on preamps.
Since the Elektor articles mention that "clean" power is not too critical to the design and I am not planning on running lengthy cables between the boxes, I wouldn't have expected serious issues. I would just like to get some space and an additional metal barrier between the PSU and gain stages.
How would you go about outsourcing the PSU?
My preamplifiers are using external PSU and while with a line preamplifier this is not really necessary, for a MC preamplifier is mandatory, at least from my experience.
I have the transformer with the rectifiers and the capacitors in an external box and use umbilical cord to bring separate supply L/R for the stabilizers inside the preamplifier box. Will do the same for this preamplifier [emoji6][emoji108]
I have the transformer with the rectifiers and the capacitors in an external box and use umbilical cord to bring separate supply L/R for the stabilizers inside the preamplifier box. Will do the same for this preamplifier [emoji6][emoji108]
Hi all.
Oh yes, I realise it's been quite a few years.
But still...
Does anyone still have all these boards?
It looks like I have everything except the phono board. I thought I had at least one more phono board, because I've been buying parts for it.
I have two other board designs done that I haven't released yet. I was waiting until I finished another design/layout to get all three at the same time, but haven't found time to complete the design. I might be talked into releasing what I have, however, and adding some phono boards to the order. PM me if you are interested.
I have two other board designs done that I haven't released yet. I was waiting until I finished another design/layout to get all three at the same time, but haven't found time to complete the design. I might be talked into releasing what I have, however, and adding some phono boards to the order. PM me if you are interested.
If I understand correctly, you have everything except this board (Preamplifier 2012 (2) (110650-2) £22.95) ?