After Eighty - Small Ashdown Combo On Steroids

[Chienmortbb]

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. 

Edited May 24, 2020 by Chienmortbb
Smelling mistakes

[Chienmortbb]

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.

 

 

Edited May 25, 2020 by Chienmortbb

[Chienmortbb]

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!

Edited May 27, 2020 by Chienmortbb

[Chienmortbb]

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?

Edited May 27, 2020 by Chienmortbb
typoze

[Chienmortbb]

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. 

[Passinwind]

14 hours ago, Chienmortbb said:

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. 

Outstanding. I still have a couple of preamps with that first generation board of mine in them kicking around. One is about to get replaced by the second gen one any day now, but the differences are pretty minimal. Hope it goes smoothly for you from here on out!

BTW, did the I/O cabling for the power module come with it, or did you have to do the usual aftermarket route to get it done?

 

[Chienmortbb]

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.
 

[Passinwind]

3 hours ago, Chienmortbb said:

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.
 

I just ordered a few sets of I/O cables from Ghent the other day, not for the first time. IME the key to good consistent crimps is to use a real crimping tool, i.e. not just a generic hand one meant for occasional prototyping . Real JST hand crimpers are already about $400 new over here and you need two different models to do the ICE modules I've worked with. If you go for powered ones with thermal stripping you're looking at a few $K each.

And at least that's one of my older board layouts, which are often much easier to do mods on. The SMT onboard preamps I'm doing these days are really not all that much fun to work on.

[Chienmortbb]

On 29/05/2020 at 14:27, Passinwind said:

I just ordered a few sets of I/O cables from Ghent the other day, not for the first time. IME the key to good consistent crimps is to use a real crimping tool, i.e. not just a generic hand one meant for occasional prototyping . Real JST hand crimpers are already about $400 new over here and you need two different models to do the ICE modules I've worked with. If you go for powered ones with thermal stripping you're looking at a few $K each.

And at least that's one of my older board layouts, which are often much easier to do mods on. The SMT onboard preamps I'm doing these days are really not all that much fun to work on.

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.

Edited May 31, 2020 by Chienmortbb
tie poze

[Chienmortbb]

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.

[Owen]

Back in the days when I desgined amps (in my head) I always fancied something like this. A 10" combo with a MASSIVE power amp in it so that I had something small to carry around and rehearse with but it would plug into a larger cab and drive it hard for air-shifting duties.

[Chienmortbb]

19 hours ago, owen said:

Back in the days when I desgined amps (in my head) I always fancied something like this. A 10" combo with a MASSIVE power amp in it so that I had something small to carry around and rehearse with but it would plug into a larger cab and drive it hard for air-shifting duties.

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.

[Chienmortbb]

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.
 

 

 

Edited June 1, 2020 by Chienmortbb

[Chienmortbb]

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.

Edited June 1, 2020 by Chienmortbb

[Greg Edwards69]

On 31/05/2020 at 14:27, owen said:

Back in the days when I desgined amps (in my head) I always fancied something like this. A 10" combo with a MASSIVE power amp in it so that I had something small to carry around and rehearse with but it would plug into a larger cab and drive it hard for air-shifting duties.

I've been thinking the same lately.  Something small enough for home use and rehearsals that's easy to carry, and only being the big speaker when I need it.  I've been looking at the Trace Elliot Elf combos and the Phil Jones combos. Unfortunately though, I don't have the spare GAS tokens.

[Chienmortbb]

16 hours ago, Greg Edwards69 said:

I've been thinking the same lately.  Something small enough for home use and rehearsals that's easy to carry, and only being the big speaker when I need it.  I've been looking at the Trace Elliot Elf combos and the Phil Jones combos. Unfortunately though, I don't have the spare GAS tokens.

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

[Chienmortbb]

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.

[Mottlefeeder]

The ASX pcb has 400mA fuses on the aux supplies, so you may be able to replace them (SMD fuses?), or short them out and make sure you have smaller value fuses downstream.

David

[Chienmortbb]

36 minutes ago, Mottlefeeder said:

The ASX pcb has 400mA fuses on the aux supplies, so you may be able to replace them (SMD fuses?), or short them out and make sure you have smaller value fuses downstream.

David

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?

[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.

 

[Chienmortbb]

The switch  arrived and of course I originally installed it the wrong way round. After 20 minutes I managed to get it out and change it around. The original switch was stuck with silicon to ensure it did not move, I don't have any of that so used some UHU. I will update when the UHU is dry.

I also decided to take the balanced Headphone/DI output from the output of the pre-amp, before the master volume rather than the EFX Send. This is so is is after the EFX return/aux input.

Edited June 10, 2020 by Chienmortbb

[Chienmortbb]

Too many demands on my time at the moment but I have made progress. I Finished wiring the amp, including re-installing the original board and converting it to BTL.  It is all working I’ve played through for a couple of hours through a PA cab. It sounds good but I am biased.

I’ve decided to put a switch in where the DEP Switch was. The original preamp design had a bright switch and I have decided to incorporate this. You can see the red switch between two of the pots on the photo below. Other things to do are to add the auxiliary input. You can see the upturned white capacitor wire-tied to the red one, that will form the auxiliary input in place of the effects return. I am not  using effects send and return on this build.  To use an auxiliary input requires the front panel to be drilled and there is space next to the instrument input. I am also considering whether to install an dedicated headphone out rather than bridging the DI out( currently labelled Headphone. 
 

more later. 

[Passinwind]

I'll be interested to see how that bright switch works out; I've used it in the Rod Elliot preamp design I lifted it from but not in the board you have.

Nice to hear that you're making noise now!

[Mottlefeeder]

On 10/06/2020 at 12:21, Chienmortbb said:

... I also decided to take the balanced Headphone/DI output from the output of the pre-amp, before the master volume rather than the EFX Send. This is so is is after the EFX return/aux input.

I was wondering why you had a two channel balanced feed circuit, and then I read this bit and it all made sense. Having said that, Rod Elliott has modified the DI output on his bass pre-amp design so that it could tolerate anyone accidentally applying phantom power to it - series resistors and zener clamps if I recall, to take care of the inrush.

David

[nilebodgers]

12 hours ago, Mottlefeeder said:

I was wondering why you had a two channel balanced feed circuit, and then I read this bit and it all made sense. Having said that, Rod Elliott has modified the DI output on his bass pre-amp design so that it could tolerate anyone accidentally applying phantom power to it - series resistors and zener clamps if I recall, to take care of the inrush.

David

A common technique is to use back-to-back 12V zeners with a resistor in the 1k - 3k3 range (plus a 50V min blocking capacitor). GK do that on a lot of their later models.