Chienmortbb

I got the fuses and.......they blew but protected the 50ASX2 module. I replaced the fuses with 115R 1/4Watt resistors. These would eventually burn out if there is a problem but hold up long enmough for some faultfinding to take place. Th +ve resistor was burning out, cleary there was a short somewhere. After almost a day looking for the problem I found a small whisker across two tracks on the positive regulator side. Cleared it an all is good. Then I connected everything up gradually, the preamp worked fine but as soon as I connected the unbalanced/balanced/bridge converter the fuses blew again. Disconnected the UBB board and switched on, all OK. Switched off and the mains switch went a bit wobbly. So I have ordered a new one but that will be here midweek.

This is of course true.

Why downplay it Frank?

You must have read my mind. I took out the two through hole, PCB fuses and checked the voltage upstream of the fuses. Both were around 26.5V suggesting that the fuses had protected the module. I decided to bypass the on board fuses and fuse at F315mA. The onboard fuses are, as you say T400mA so there is some safety margin. As you probaby know, the F indicates quick blow and the T before indicate slow blow or time delayed. In this case the F315mA should blow well before a T400mA, protecting the module.even with the fan, the current draw from either supply should be under 150mA, so I should be OK. Sadly the next day delivery I paid for has failed so I will have to wait until tomorrow to proceed unless I risk another module...... can he wait?

Oh dear. It had to happen. Things were going far too well. I had been assmbling checking and then testing as I go. The pre-amp wiring and testing went well, apart from the crossed wires on the gain/volume. Sadly I had problems getting the opamps into the sockets in the unbalanced to balanced converter board. The pins got bent a couple of times. but eventually I got them in. In my hurry to get things moving, I did not notice that one of the chips was in backwards. The result was that I blew the auxilliary supplies. My own fault. I should have fused the power supply board. I will investigate the problem but luckily I have three modules and so I can carry on. I have modified the power supply to include fuses and have ordered some fuses. These should arrive tomorrow and I will carry on then.

I believe that there is a warehouse with lots of flour, eggs and GAS tokens somewhere near Heathrow.

Nice touch. I love Ashdown.

I tend to agree. The switching contacts on jacks are not too reliable, it would be better to have a separate switch but as it is designed in, the contacts need to be cleaned from inside the amp if needed.

Here is a picture from another angle, I have highlighted where the next wires will go. The one from the preamp output (purple) is so short, there is no point in using screened cable. For the one that goes from the EFX send to the faux DI out (turqoise/light blue), I may use a screened cable. This design was designed to use high quality audio opamps but for the purpose of testing I have used TL-082,TL072 and NE5532. Once I have finished testing I will use OPA2034 and either LM4562 or one of the high quality Linear/Analog Devices bipolar opamps.

Well I have put power and signals through the preamp and s seems to be working well. I did encounter one problem. No signal after the volume/gain control. Turns out I wired it in reverse. All the pots were wired with the same coloured wires. Brown, Red and Yellow. I am not at home at the moment so don’t have access to all my bits and pieces. On the preamp PCB, the pot connections are labelled 1,2 & 3. So bass pot connections are b1,b2,b3. The resistor colour code has Brown=1, Red=2, Orange=3 Yellow =4. As I have no orange wire, I used yellow. So whenI looked under the board, I could easily see that wires 1 & 3(4) were reversed on the first volume pot. So I changed those over et voila. Signal all the way. @Passinwind designed the PCB to be double sided so there were pads on both sides to solder the wires to. I xchose to solder from below to make it look better. Had I wired it with all the wires on top, I might have seen my mistake sooner but it would have looked like a rats nest.

Careful, you will have me putting the 125ASX2 amp in instead. My idea for this was a practice amp that could be taken to open mic night.I have PA support there so this could be enough on its own for that. I will save the 125ASX2 for the active 1x12 when lockdown ends.

Some progress.The four pots that are connected to the pre-amp PCB have been wired as can be seen in the picture. I have also been having some thoughts on the hole left by the DEEP switch and the unused Effects Send and Return features of the preamp. I will use the effects send to be the input to one side of the balanced transmitter, the side that feeds the line out (formerly the headphone output). The effects return will be repurposed as the Aux input for practice, after all this is a practice amp. So the next question is, use the Deep hole for the Aux input or drill a new one somewhere else? That can wait. I now only have to connect the +/-15V rails to start testing. It makes sense to test one part at a time so I will check the preamp is working before connecting the to the Unballanced to Balanced converter board. Of course I also still have to convert the module to Bridge Mode (BTL) but more on that later.

Yes I came to the conclusion that the Ghent cables are cost effective and well made, so there is no sense trying to make your own. It was never a job I enjoyed in the past even having the correct crimp tool. I realise I have slipped a bit behind but hope to make more progress today. The Garden Funiture however is finished. I might use that finish on a bass soon.

I got it from Ghent Audio. At the time it made sense as it was hard to source JST connectors and the added cost of the crimp tool did not make sense. As I have three other modules, two of the 50ASX2 and a 125ASX2 I might look again at it although from past experience, crimping well is not as easy as it looks. Looking at the Preamp is like looking back in time You can see the mods on top and there is an added capacitor on the underside. It was already loaded so it seemed sensible to use it on this project.

Well the postman came and I now have almost all the parts I need. I will send pictures tomorrow but I now just need to connect about 26 wires. I hope I can get some sound out tomorrow.

I cannot do anything with the amp side until the new components arrive so I decided to cut the port hole. I have a Lidl (Parkside) rotary cutter, similar to a Dremel Trio. It has been used to cut the woofer hole for the prototype of the BC112 as it has a circular hole cutting attachment. When I went to set it up I realised it would not cut a hole as small as 40mm radius. So I had to do it free hand. Those of you that can tear their eyes away from those stylish slippers will see that the hole is not quite circular. However it will do. The test fit of the port is shown below. Now to wait for the postman?

Just for a laugh I checked on my package from Thailand and....... yes it has landed in the UK. The package will be here today, Wednesday!

The best laid plans......I got something in my eye and could not do anything for the last few days.I may get back on the horse later but I can fill in a few more details. I have removed the fan drive circuitry. I could not be sure the thermal pin on the ICEPower works as I, so it has gone. The options are, no fan, fan on, running from the +15V rail, fan on , running from the +25v unregulated rail, fan on , running between the +/-15V rails, As the fan is only needed if the module is used at a fair volume, I will leave that until the end. Initially this is only for use as a small prctice amp but it may well become my go-to for opon mic. If I do build an extension cab, the fan would be needed. All the circuits I am using, apart from the +/-15v power regulators and ill-fated fan drive circuit, were designed by other people. The power unit is ICEPower, the preamp is by @Passinwind and the amplifier bridging unit is from Elliot Sound Products. I am happy to answer any questions while respecting the intellectual copyright of the above.

Most of the mechanics are complete and I have started the wiring between the modules. The have done a quick audio test on the ICEPower module and connectedit to the pre amp power supply. Thankfully I get +/-15V as expected and music out of the speaker. I have added the green connectors to enable easy installation . They make it easy to connect the modules but the screw heads are tiny. As my parts order is still stuck in Asia, I va re-ordered the pots and a few other parts from a UK company. They should be here by the end of next week. You can see the mains and speaker wiring here. To keep things easy I have kept the jack extension speaker output on the top and wired it in parallel with the combo’s speaker. The ICEPOWER module can output 100 watts into 8 ohms or 170 watts into 4 ohms at 1% distortion. Many vendors quote 200 or even 220 watts for this module but that can only be achieved as high distortion levels (10%) still for what I want 100/170 is more than enough. Tomorrow I hope to cut out the hole for the speaker cabinet port as well as finishing the garden furniture.

I have made some progress although other, more boring projects, neede my attention. The chassis was stripped of everything except the IEC mains input socket/fuseholder and the on/off switch. The best part of modifying an existing amp is that most of the holes are cut. ON the other amp project the worst part was cutting the holes for the mains switch. In the picture below you can see the switch/fuse holder and IEC input socket. The transformer was attached on the right hand side. You can still see one of the mounting bolts. You xcan also see the bodge I had to do as the mounting spacer for the preamp ended up in one of the ventilation slots. Four washers and some superglue created a solid fixing. The smears are from the heatsink compound that thermally coup[led the original heatsing to the chassis. it gets everywhere but can be cleaned up with thinners or white spirit.

Thanks for the suggestion. I would rather keep 230V out of the way as muct as possible.The fan I am using has come from a piece of audio equipment so I am hopping it will be OK. I will be checking the disturbance on the supplies soon.

I have not tested it. My current plan is to run the fan only as the temperature rises and I was going to power the fan from the unregulated auxilliary supply (+25V) while the preamp is powered by the regulated =/-15V. This wsas because |I was worried about exactly what you describe. I am still investigating as I cannot find the information I need in the ice power literature, I might have to run the amp while heating it with a hairdryer to test the thermal performance. More later.

Don't tempt me Pete. Right the good news is that some of the parts reached Heathrow this morning. The others are still somewhere between Singapore and Poole even though they were ordered two days earlier. Anyhow I will not peer too intently into the oral cavity of a equine present. The chassis is now stripped (although the transformer is still fitted). The boards are laid out on the chassis as can be seen in the picture. On second thoughts I will move the bridge adaptor to the centre and rotate the ICEPower module so thate the airflow from the fan blows ditrectly past the whole of the power supply/amp module.

Well I got the sander out and thought I had not done very well. It was hard and there is still a lot of adhesive and carpet residue on the sides but it is much better than the picture above. The covering is not due untill next week so I think I will test wrap that with the cabinet as it now is to see how it will look. However I suspect, like paint, it will show all the lumps and bumps. My original thought was to keep this cabinet. It is supposed to be a low cost build made largely ftom existing components and materials. It is very heavy though and a ply cabinet would be much lighter. Thinking cap on. On to the electronic design for a while.

The carpet (why do the call it that, it's felt) has come off but it was a b*gg*r, took three hours and it looks a mess. Tomorrow, weather permiting I will get the sander out, clean it up and cur the porthole (no cruising or Jane MacDonald jokes please). The box is made from a sort of heavy chipboard, denser than we usually get and the baffle is MDF. I almost wish I had started from scratch and made a new cab from light weight ply.