2020 Monkeymatic Black Butte Desktop #2

[martin manning]

Well alright, that looks good. Glad it worked out!

[martin manning]

Gotta hear a clip of this...

[xtian]

Gotta hear a clip of this...

Will do...soon-ish. You know, back in the real world, when wife went to work each day, leaving me at home, there was lots of time to play loud...

Just saying.

[norburybrook]

Aaron, love the idea of this and it looks so cool.Love the chassis and wooden surround, like a 60's hifi amp. Did yo make the cabinet, what's the wood, and is it just mitre joints?

I hope it sounds as great as it looks.

I'm tempted to fire up the iron seeing this. I have an old marshall OT in a box here and various bits, I think I have a sheet of aluminium too......

My first build ever was a SE 5w amp. I used it in the studio for ages, it was fantastic.

M

(edit) just seen all the build stuff on your #1 link

[xtian]

Thanks, Marcus! The wood is 3/4" walnut, just mitered and glued, with 1/2" routes for the aluminum to sit in. I love this simple circuit, and building the L-pad into the amp makes a great master volume!

[norburybrook]

are there any technical pro's and cons to a single ended amp. I can see that the signal path would be more pure as you only have 2 tubes so that 'could' be a pro. Obviously you cant have the power of an amp with a p.I and two/four output tubes so that could be a con.

Just thinking aloud here.

are you restricted in what OT you can use or will anything work? I have a Marshall 50w OT sat here could that work with one output tube?


M

[pompeiisneaks]

I'm no pro on SE vs PP, but as far as transformers go, you 'could' use the 50W transformer with multiple parallel tubes, but it still wouldn't work very well. The SE transformers are like 2x bigger than an equivalent PP type, something about the way the transformers work, that for SE use you need a lot more iron, I think the term I recall was 'core saturation' is a problem that needs to be managed in SE but not as much in PP. Again, someone else here is probably way more knowledgable than that.

so basically you could use one, but if don't do a lot of work to tame the output to it, it would burn up or sound bad or both I think? It's definitely not recommended.

I've only built one SE amp ever it was the champ I and my wife built together, we still have that amp and she loves it just because she put it together

~Phil

[martin manning]

...are you restricted in what OT you can use or will anything work? I have a Marshall 50w OT sat here could that work with one output tube?

SE OT's have gapped cores to prevent core saturation due to the high standing current. Hammond has a number of options available with varying current and output power ratings. In PP OT's the magnetic flux at idle is ~zero due to the opposing current flow on each side of the PP stage.

[xtian]

I used a Hammond 125ESE OT, which is 15 watts max. My aim was to get 10 watts clean, as a way to double the volume of the 1-watt amps (Akai M8) I built recently. Goal met.

SE Pros: Power tube distortion is said to have a unique characteristic vs. P-P amps. Small parts count. Plus, you get to use your random single power tubes!

SE Cons: Hum--however, the CLC filter solves this issue nicely. Heavier OT per watt.

[norburybrook]

thanks for the replies, once again I've learned something new

Aaron, what are 'CLC' filters?


M

[martin manning]

I can take that one... SE can't rely on the PP transformer to to cancel ripple in the plate supply, so extra filtering is needed to make them quiet.

[brewdude]

The important thing to note with the CLC pi filter is that the OT hooks to the second cap (the one after the after the inductor.

[Colossal]

A CLC filter up front, before B+1, makes for a VERY quiet single ended amp. Definitely money well spent on that choke. Make sure it is rated for more current than the entire amp draws.

[xtian]

Wife finally left the house for a hot minnit, so I recorded a demo for yuhs!

[norburybrook]

Aaron, that's such a cool amp all round, sounds great, lovely clean and nice dynamics into OD.

Love your little monkey stood up on the transformer

I think it would be a great studio amp for anyone and possibly small gig too and so simple.


p.s. can I ask a stupid question? looking at the layout the SS rectification looks as i would expect, on your actual build the diodes seem to be connected to one side of the AC and the CT not both sides with the CT grounded, why?


Just needs single tube reverb and vactrol trem now.....Doh!!!!


M