DIY MKIIC+ build.

Toe_Knee

I haven't posted much on here but I am liking what I am seeing so far so I thought i'd post up some pictures of a MKIIC+ style amp i'm building.

PCB & Chassis are from ampclones.

here's the boards partially populated

And here a bit more complete. The silkscreens on the pcb were wrong on some of the capacitors tantalums mainly so it's a good job that I was paying attention to the schematics as I went along.

One thing that I had to do that I wasn't expecting was adding the threads for the chassis mounting. I chose rivnuts to do this as it was a pretty cost effective solution and didn't require any specialist tools.

Then last but not least for now is the custom Simulclass output transformer. This took many hours of research which led me to the fact that a 50w OT could be used in its place with mismatched secondaries but my cab is 16ohm and I didn't want to lose the 15ohm tap so I dug up a winding pattern of the OT that someone drew up when repairing a stereo simulclass power amp and sent it off to BLS transformers and had them make me one with the 16ohm tap. They were a pleasure to deal with and I will definitely be returning in future.

The power transformer is currently being withheld by UK customs so the build is on hold until either that arrives or after i've moved house at the end of the month.

Deijavoo

That remnds me, I'll need to get some more work down your way once this is complete. You know, have an inspection. ....

:-\"

Toe_Knee

Deijavoo said:

That remnds me, I'll need to get some more work down your way once this is complete. You know, have an inspection. ....

:-\"

You're very welcome. In fact i'm in the process of gathering people that I know have interesting amps to have an 'amp day'.

Once i've got moved and it all sussed out you are welcome to pop down.

Misterg

Looking good!

I hadn't come across BLS before - if it's not a rude question, how much (roughly) did the output transformer cost?

Toe_Knee

Misterg said:

Looking good!

I hadn't come across BLS before - if it's not a rude question, how much (roughly) did the output transformer cost?

It's not rude at all. I can't remember the exact price but it worked out around £130 including VAT & shipping. 

Misterg

Thanks - not bad in the scheme of things.

Deijavoo

Toe_Knee said:

Deijavoo said:

That remnds me, I'll need to get some more work down your way once this is complete. You know, have an inspection. ....

:-\"

You're very welcome. In fact i'm in the process of gathering people that I know have interesting amps to have an 'amp day'.

Once i've got moved and it all sussed out you are welcome to pop down.

Get on!

Yeah I'm game for that. Although, we should really make it round at Ant's place.  He seems to have a small army at the moment.

Toe_Knee

I've finally got around to starting to unpack my building stuff after moving.

Now I just need to sort the headshell and get back to building.

[Deleted User]

I'd love to hear some clips when this is finished. The Mk11c is the most revered Mk series Boogie. If they can be cloned, this is great news.

Toe_Knee

quite a few people have already cloned them over on the sloclone forums but they always ignore the simulclass power amp or EQ.

I wanted to go all out.

If i end up disliking the simulclass poweramp ill just swap it out for a marshall style one for that instant master of puppets tone.

there will definitely be clips so watch this space!

Si_

Cool.. looking forward to seeing it progress.

jpfamps

Where were the tant caps used; are they in the eq section?

My guess is that these are an historical hang over from when tants were much better caps than ali electrolytics. 

Modern ali electrolytics are are a huge improvement over the caps used in the 70s and 80s.

Toe_Knee

jpfamps;47353" said:

Where were the tant caps used; are they in the eq section?

My guess is that these are an historical hang over from when tants were much better caps than ali electrolytics. 

Modern ali electrolytics are are a huge improvement over the caps used in the 70s and 80s.

A few are bypass caps 15uf and then there's the eq as you mentioned.

I will probably end up swapping them at some point but I wanted to hear the circuit as intended before tweaking it to my tastes.

jpfamps

Toe_Knee said:

jpfamps;47353" said:

Where were the tant caps used; are they in the eq section?

My guess is that these are an historical hang over from when tants were much better caps than ali electrolytics. 

Modern ali electrolytics are are a huge improvement over the caps used in the 70s and 80s.

A few are bypass caps 15uf and then there's the eq as you mentioned.

I will probably end up swapping them at some point but I wanted to hear the circuit as intended before tweaking it to my tastes.

A sensible approach.

Back in the day Tants had much better temperture stability that ali electrolytics, which is important in the eq networks. 

I suppose there isn't enough room to use film caps.

Toe_Knee

jpfamps said:

Toe_Knee said:

jpfamps;47353" said:

Where were the tant caps used; are they in the eq section?

My guess is that these are an historical hang over from when tants were much better caps than ali electrolytics. 

Modern ali electrolytics are are a huge improvement over the caps used in the 70s and 80s.

A few are bypass caps 15uf and then there's the eq as you mentioned.

I will probably end up swapping them at some point but I wanted to hear the circuit as intended before tweaking it to my tastes.

A sensible approach.

Back in the day Tants had much better temperture stability that ali electrolytics, which is important in the eq networks. 

I suppose there isn't enough room to use film caps.

They could be used in a few of the spots. It's something I will have to figure as i go along.

Toe_Knee

Just a small update. The headshell has been tolexed. Now for the grill and to decide whether to add silver piping or not....

Annoyingly i'm now on long shifts at work so i'll only get a chance to work on it on sundays from here on out. Hopefully it will be done for christmas.

Deijavoo

Ooh!  Very intereted to hear this.