Which chassis layout floats your boat!

DJH83004

Bit of Friday fun, had two very nice amps in this week, both very popular, but which layout do you prefer and why? also on the lower chassis what is inside the hole left of centre (excluding the bias adjust pot) :-) 

 

Sporky

I like the top one because it's all neat and tidy. It looks like more care and attention went into it and also that it'd be easier to service.

Phil_aka_Pip

I agree with @Sporky

I also dislike the valves sticking out of the back of the lower one

ESchap

DJH83004 said:

 what is inside the hole left of centre (excluding the bias adjust pot) :-) 

 

Flux capacitor?

jpfamps

The Mojave (top) will be easier to work on than the Carr.

Both, in my opinion, don't employ best layout practice, for example grounding seems pretty random on both amps.

The construction method used on the Carr is the most inefficient and error prone method of building and amp, with no real advantages.

I would like to try building an amp with polypropylene filter caps though.

exocet

jpfamps;1071252" said:

The Mojave (top) will be easier to work on than the Carr.

Both, in my opinion, don't employ best layout practice, for example grounding seems pretty random on both amps.

The construction method used on the Carr is the most inefficient and error prone method of building and amp, with no real advantages.

I would like to try building an amp with polypropylene filter caps though.

From what I've seen, a lot of Carr stuff is like that (point to point wiring in many areas). The Slant 6v looks like an absolute nightmare to work on.

Sporky

Out of interest, how is the Carr identifiable as such?

jpfamps

exocet said:

jpfamps;1071252" said:

The Mojave (top) will be easier to work on than the Carr.

Both, in my opinion, don't employ best layout practice, for example grounding seems pretty random on both amps.

The construction method used on the Carr is the most inefficient and error prone method of building and amp, with no real advantages.

I would like to try building an amp with polypropylene filter caps though.

From what I've seen, a lot of Carr stuff is like that (point to point wiring in many areas). The Slant 6v looks like an absolute nightmare to work on.

I've made a few amps like that; in fact the first few amps I ever made used tag strip + point to point wiring.

You can get a very short signal path using this method of construction, which is beneficial for low interference (I don't believe there is any tonal magic that occurs with a short signal path), as components are often soldered directly onto the valve sockets.

However, to do this correctly the component leads should be crimped onto the tags and this makes changing components harder. Of course most components will never changing in the life of the amp.

This is a reasonably good method for simple amps eg Champ, but for more complex amps soon gets very hard to trouble shoot.

Sassafras

I like the point to point wiring although I'm not entirely sure why. Maybe because it is harder and more challenging, so I associate that with better quality work.

exocet

Sporky said:

Out of interest, how is the Carr identifiable as such?

The point to point wiring combined with the "oversized" Solens Polypropylene Capacitors that are used in place of the more typical electrolytic capacitors for power supply filtering. Electrolytics physically smaller for any given value of capacitance. Steve Carr is the only commercial builder that I know of who uses the Polypropylene caps. They are expensive but in theory never need replacing.  

 
Here is the 6V 

https://www.google.co.uk/imgres?imgurl=http://amploft.co.uk/blog/wp-content/uploads/2012/05/image0012.jpg&imgrefurl=http://amploft.co.uk/blog/2012/carr-slant-6v/&docid=LFOaNGm9YJa-TM&tbnid=wKwN7OdBUmZ5ZM:&w=1283&h=855&hl=en-gb&client=safari&bih=671&biw=1024&ved=0ahUKEwi2gOrDydfMAhUgM8AKHdQIDBYQMwglKAkwCQ&iact=mrc&uact=8

jpfamps

exocet said:

Sporky said:

Out of interest, how is the Carr identifiable as such?

The point to point wiring combined with the "oversized" Solens Polypropylene Capacitors that are used in place of the more typical electrolytic capacitors for power supply filtering. Electrolytics physically smaller for any given value of capacitance. Steve Carr is the only commercial builder that I know of who uses the Polypropylene caps. They are expensive but in theory never need replacing.  

 
Here is the 6V 

https://www.google.co.uk/imgres?imgurl=http://amploft.co.uk/blog/wp-content/uploads/2012/05/image0012.jpg&imgrefurl=http://amploft.co.uk/blog/2012/carr-slant-6v/&docid=LFOaNGm9YJa-TM&tbnid=wKwN7OdBUmZ5ZM:&w=1283&h=855&hl=en-gb&client=safari&bih=671&biw=1024&ved=0ahUKEwi2gOrDydfMAhUgM8AKHdQIDBYQMwglKAkwCQ&iact=mrc&uact=8

Indeed.

London Power in Canada used to use poly caps:

http://www.londonpower.com/graphics/studio.jpg

Kevin O'Connor of London Power has written several books on valve guitar amps, and has his followers as a "guru".

His current production amps use electrolytics:

http://www.londonpower.com/image/data/studio-inside_1650.jpg

I am of the opinion that the filter caps do make a difference to the sound of an amp. Poly caps will have lower ESR than electrolytic, so may well sound different.

As exocet says they should never need replacing, unlike electrolytic caps.

Arkless_Electronics

They're both good but bottom one a little easier to work on....
Poly caps will last "forever" but it's very likely that smaller values (poss a bit too small) will be used due to size and cost of polys....

DJH83004

well I'm glad my little post facilitated some interesting debate, from my perspective as a repairer I prefer the logic and symmetry of the Mojave layout, you can almost visualise the schematic. The Carr looks a bit like they made it up as they went along, working their way through the schematic (which clearly they wouldn't do in a production environment, but it looks a bit like that).

With regards to the hole in the chassis, on the otherside is the square aluminum box with the bias pot on the end. Inside is actually a voice coil, which forms part of the L pad attenuation circuit, in much the same way as the Weber Mass attenuators use.    

Sporky

That London Power one appeals to me. So neat. So organised. And chuffin' huge toroidal transformers.

hywelg

Comparing that Carr Slant pic with this similar design amp, my preference is for neatness. I know PTP is supposed to be cool but to me it just looks like its been thrown together.

jpfamps

Sporky said:

That London Power one appeals to me. So neat. So organised. And chuffin' huge toroidal transformers.

$4700.

Never tried a toroidal output transformer, although speaking the Tiger Toroids who make our mains transformers there are a number of issues, not least interleaving, needed for best performance, rapidly consumes the space on the centre of the toroid.

jpfamps

DJH83004 said:

 The Carr looks a bit like they made it up as they went along, working their way through the schematic (which clearly they wouldn't do in a production environment, but it looks a bit like that).

    

Well that's how the first few amps I ever made were constructed, and they didn't look much different...........

exocet

Some of the Matchless stuff looks pretty chaotic

Sporky

jpfamps said:

$4700.

I've spent more on an amp.

But only for work, and not my money.

Also about 200 times the power.

hywelg

Much more of an ordered chaos look to the Matchless than the Carr. And the component legs are all shielded, lead dress is clearly better though out.

Arkless_Electronics

There's no link between neatness and quality! In fact quite the opposite in many circumstances. It depends on the type of circuitry, the frequencies and signal levels, luckily a guitar amp is relatively uncritical. Having all parts well spaced out and in neat parallel lines etc looks nice to the human eye but results in longer wiring between parts and less direct earth paths....