FarnsAmp MkII ~ build thread ~ Going back and tidying the chassis after tweaking the circuit.

[Guest Farnsbarns]

I`m sure this thread will disappear off the first pages by the time components start arriving but I`m excited because today I finished planning the circuit and sent off for a quote.

 

Once again I`m really modding an existing circuit but building from scratch.

 

what did I learn from MkI? 20 watts and power stage dirt is too loud for home use. I either need pre amp dirt or variable output. The new circuit has both... Pre amp gain and fully variable output power from 0 to 5 watts.

 

Reverb before dirt sounds pants, the new circuit allows for dirt from both, or either, amp stage. This means a tube driven reverb tank between the stages will be far more usable.

 

Transformers in reverb circuits make for a lot of noise. This time I`ll be very careful about the location ans i might box it in completely.

 

A 3 band tone stack is really the only way to go so this time I will be having one.

 

an effects loop is very useful and a pain to splice in later so I'm doing it from the start.

 

I hope to have all the parts before the end of the month so I`ll dig this thread up then and start the build properly.

[Rabs]

Nice one

 

I look forward to it :)

 

I wish I knew more about amps to comment on your plans but im sure you learned much from the first time (as it seems you have).

 

(maybe we can play my guitar through it when they are both done ;))

[surfpup]

... Pre amp gain and fully variable output power from 0 to 5 watts.

 

So you are going single ended this time? EL84 or Octal?

[Guest Farnsbarns]

So you are going single ended this time? EL84 or Octal?

 

Yes, single ended. As for valves.... eeny meeny miney mo.... Both, or should I say, either. Both sockets, allowing a choice.

[Ryan H]

Yes, single ended. As for valves.... eeny meeny miney mo.... Both, or should I say, either. Both sockets, allowing a choice.

 

I recall seeing a video with Martin Kidd (formerly of Cornish, now of Victory Amplification) who's included both a noval and octal socket in one of his amps and has separate volumes for each...so you can blend 2 output tubes or use them separately by just turning the volume off on one...

 

For some reason your mention of including both sockets brought that to mind...

 

Can't wait to see the build!

 

Carry on,

 

-Ryan

[krock]

Both, or should I say, either. Both sockets, allowing a choice.

 

I'm still yet to use anything other than el84 amps. I imagine the choice would be nice in a studio environment for overdubs

[Guest Farnsbarns]

I recall seeing a video with Martin Kidd (formerly of Cornish, now of Victory Amplification) who's included both a noval and octal socket in one of his amps and has separate volumes for each...so you can blend 2 output tubes or use them separately by just turning the volume off on one...

 

For some reason your mention of including both sockets brought that to mind...

 

Can't wait to see the build!

 

Carry on,

 

-Ryan

 

Yeah, I've seen that too. This will take EL84/6V6/6L6 but it won't allow for mixing them.

[Guest Farnsbarns]

Just ordered an Accutronics type 4, 8 ohm, horizontal, insulated/grounded reverb tank. Also got some knobs. The trickiest part of making a fascia is the numbering for the knobs so I decided to look at numbered knobs like guitar knobs. I wanted something a little bit more amp-ish. I found these, I think they'll give me a unique look. What do you think?..

 

 

 

They're nearly 4cm round, now I'll just need a control label and an arrow on each control.

[pippy]

They only go up to 10.

 

P.

[Guest Farnsbarns]

They only go up to 10.

 

P.

 

Yeah I could only afford 10 masters, 10 gains, 10 basses, 10 middles, 10 trebles, 10 reverbs and 10 dwells this time. Maybe MKIII will have 11 of each. We'll see how 10 of each sounds for now.

[Rabs]

Yeah those knobs look pretty cool

[Rabs]

They only go up to 10.

 

P.

They do (probably obviously) have knobs that go to 11 :)

 

http://www.allparts.com/0-11-knobs

 

Maybe I will use some of them on the next build as a joke ;)

[badbluesplayer]

Cool!! Do you have a schematic or a layout done yet? I'm interested in seeing what you're doing.

[Guest Farnsbarns]

Cool!! Do you have a schematic or a layout done yet? I'm interested in seeing what you're doing.

 

I do have a schematic but it is largely someone else's intellectual property (barring my mods). I believe I'd need his permission to publish it. Maybe once I've asked him. As for layout, only rough, back of an envelope job.

[Guest Farnsbarns]

I have been considering optional Speakon connectors for this amp. I have never had any experience but from an engineering stand point they seem, theoretically, much better than 1/4" jacks. Anyone had any experience with these?

[capmaster]

I have been considering optional Speakon connectors for this amp. I have never had any experience but from an engineering stand point they seem, theoretically, much better than 1/4" jacks. Anyone had any experience with these?

The very Speakon advantage is the complete electrical isolation of the plug's and jack's outer surface.

 

First, there is no danger of suffering electric shock when touching connectors driven by a bridge-mode power amplifier under signal - this is why they were designed in first order.

 

Second, you won't bring sweat or grease from your skin onto it.

 

In case of building a guitar amp with an earthed outer speaker connector, i. e. sleeve of jack and plug, I would stay with 1/4" jacks and cables.

 

When I bought a semiconductor stereo amplifier for my digital amp setup, I decided to go with one without a fan and providing 1/4" jacks. I don't use the bridge mode also provided, but there are high voltage symbols and warnings next to the bridged outputs. The signal's peak voltage to ground may reach up to 90 volts.

 

There won't be any danger like this in your amp, so no problem fitting it with 1/4" jacks in my opinion.

[Guest Farnsbarns]

The very Speakon advantage is the complete electrical isolation of the plug's and jack's outer surface.

 

First, there is no danger of suffering electric shock when touching connectors driven by a bridge-mode power amplifier under signal - this is why they were designed in first order.

 

Second, you won't bring sweat or grease from your skin onto it.

 

In case of building a guitar amp with an earthed outer speaker connector, i. e. sleeve of jack and plug, I would stay with 1/4" jacks and cables.

 

When I bought a semiconductor stereo amplifier for my digital amp setup, I decided to go with one without a fan and providing 1/4" jacks. I don't use the bridge mode also provided, but there are high voltage symbols and warnings next to the bridged outputs. The signal's peak voltage to ground may reach up to 90 volts.

 

There won't be any danger like this in your amp, so no problem fitting it with 1/4" jacks in my opinion.

 

Yeah, the point is they are a firmer connection which clicks in, all contacts are away from dirty fingers when unplugged and they are air tight which is good at the cab end. I just consider them a better engineered solution with no drawbacks which is all the reason I need to use them. I am considering having both so as not to discount using 3rd party cabs. I was asking more about any experience of them to identify any drawbacks I might have missed.

[capmaster]

Yeah, the point is they are a firmer connection which clicks in, all contacts are away from dirty fingers when unplugged and they are air tight which is good at the cab end. I just consider them a better engineered solution with no drawbacks which is all the reason I need to use them. I am considering having both so as not to discount using 3rd party cabs. I was asking more about any experience of them to identify any drawbacks I might have missed.

Besides their pricing, there are no drawbacks I experienced with Speakon. I think having both 1/4" and Speakon for compatibility reasons is a good idea.

[badbluesplayer]

I'm not sure what you want to end up with and what you want to learn. Some guys like to build stuff from scratch. Some guys are better off building an established design from a kit.

 

If you want to tinker around and you already know what you're doing, then it's good to build from scratch. If you're serious about amp building or if you want to learn a lot, then building a kit might end up being more rewarding, IMO.

[Guest Farnsbarns]

I studied electronics (actually, electrical engineering, then electronics and then electromechanical engineering) at college and worked in the field for many years. I defo know what I'm doing and I defo like to tinker. Not sure that im looking to "learn" anything really, that's not to say that I have nothing to learn of course. I've designed from scratch before but right now it suits me to add modding amp circuits from schematics, and then building them, to my tone chasing efforts.

 

I've built and tinkered with HAM radio gear before too. Then I realised that HAM radio will put you in touch with other enthusiasts who want to talk by HAM radio about HAM radio. A bit tedious eventually.

[Guest Farnsbarns]

I had word today that the large order, which is the bulk of the bits, is to be shipped tomorrow. I'm still going to be waiting on some stuff but once I have the components I can start thinking about the board layout. The power supply circuit is unchanged from the original design so that's easy. The tone circuitry is seeing a few mods so I need to work on the layout for that and the reverb and effects loop are entirely new so I have to decide on a layout for those and then the overall chassis layout, which will be decided largely by the board layouts.

[Guest Farnsbarns]

The bulk of the components arrived yesterday. I haven't ordered enough turrets (D'oh) and will need some more before I can start properly. I'm also still awaiting the reverb tank but won't need that for a while anyway.

 

I might take some pics tonight to show where I'm at.

[Guest Farnsbarns]

I've roughed the layout on to the board by covering it in masking tape and drawing the components to size. I'll copy this to paper and adjust all the turret spacing just so it's even with pretty, straight lines. Then I'll tape that to the board and punch and drill the holes.

 

[Guest Farnsbarns]

I've been perfecting the layout. Here's an idea of the evolution, there were quite a few stages not shown here, these are the key stages that didn't get thrown out. The one on the right is taped to the board ready for centre punching and drilling.

 

[Guest Farnsbarns]

And here the one on the right is the board. I've centre punched it and then run a pen in each hole to mark them clearly.one edge of the board is a bit rough, it came like that, cut to size but a but rough so I might trim that edge straight...