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my new amp - It lives!


Guest Farnsbarns

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Guest Farnsbarns

Often the old 12AX7s are the better... I would rather sacrifice new ones ;)

 

All kidding aside, looks good to me, and to add a tone control shouldn't be a problem if there's enough makeup gain left in the circuit. Did you plan three preamp stages and a single-triode phase invertor/driver stage, ot two preamp triodes and a double-triode balanced driver?

 

 

 

Single pre-amp and another 12ax7 phase inverter. I will try swapping out valves in the power stage, often I find that unmatched triodes helps accentuate even harmonics. I think the triode matching idea is carried over from HiFi amps where it is important. IMO a guitar amp should colour the sound rather than amplify without colour like a HiFi amp. This amp will get it's distortion by saturating the power valves rather than in the preamp stage so a lot of difference will be heard from one valve to the next in the power stage.

 

I will have a single tone control, just not a tone stack (unless I feel it's needed once I start hearing it).

 

Eventually it'll run a single Celestian v30.

 

These vintage style amps with power valve distortion don't tend to play nicely with valve powered spring reverb, overly compressed and dark. Placing the reverb before the dirt rarely works well anway. Because of this I'm not going ton the trouble of spring reverb but I have planned ahead for a digital reverb on the input. Effectively a reverb pedal built in but I don't expect it to sound good with full power valve distortion, effectively making this a blues amp although I will make the reverb true bypassed. I will also have a bypass on the volume and tone control.

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I'm playing 'catch-up' with the forum as you know, Farns, but am watching this one, too.

 

And I'm 100% with Namvet as regards electronics..............[blush]

 

Dickinson Amps will have to watch out soon!

 

[thumbup]

 

P.

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Single pre-amp and another 12ax7 phase inverter. I will try swapping out valves in the power stage, often I find that unmatched triodes helps accentuate even harmonics. ...

Absolutely correct. This supports even-order harmonics long before the power tubes are driven to the ceiling. It is also possible and widely spreaded to use different plate resistor values in the driver stage. On the other hand, since one grid of the driver is driven itself by the signal, and the other one is biased by an RC junction, there always will be a certain amount of even-order harmonics when pushed.

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Well, what should have taken a Couple of hours, max, has turned into a day. Anyone who read my other recent thread knows why.

 

I got the layout done and soldered today...

 

 

IMG_20130821_012300.jpg

As I am in the telephone industry and do a lot of wiring of systems, your wiring is actually pretty neat. Good luck with the rest.

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Guest Farnsbarns

This is the back of the board with all the wiring attached.

 

 

IMG_20130822_180658.jpg

 

All the coloured leads from the bottom edge (in this pic) go to the valves, except the two long ones on the right, they go to the switches. The others are all going to connect the volume, tone, inputs and switches.

 

I need to wire the inputs next. There are several connections on single solder points on the inputs including connections to the board.

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Hmm, beginning to wonder if anyone is actually interested. Ho hum, I've started so I'll finish. Having looseley assembled the chassis I decided to wire the valve sockets for heating, I need to keep this wiring away from signal carrying wires so it made sense to have it in before I work on wire routes for everything else.

Yup im still very interested and watching each update. I havent commented much as I know so little about amps that the only input I can give is "yeah that looks good" so im watching to learn how its done :)

 

Also to be honest this forum has been a bit dead lately so theres just less people about to comment these days.

 

I will keep watching with great interest.

 

But it looks great so far (as far as I can tell anyway ;))

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Guest Farnsbarns

The hot and normal inputs....

 

IMG_20130822_210028.jpg

 

A bit tricky to solder all those connections at once but necessary as several wires go to several lugs. Had to do it blind so I'm not too unhappy with it. I've done better looking soldering but they all look like good strong joints.

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Guest Farnsbarns

And here is the V1 preamp socket all wired up. As you can see, the only difference between the hot and normal connections is a 56k resistor between the input and the valve... (edit: On re-reading this I realised I had been unclear. When a guitar is connected to the hot input it is also connected to the normal input, as a result "hot" means running both sides of the preamp valve).

 

IMG_20130822_205929.jpg

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Guest Farnsbarns

Awesome [thumbup] I can say that, that some neat soldering you got going on there.. nice :)

 

Thanks mate, I'm happy with the board but those valve sockets are so small and fidly, I'm more concerned with good joints and no shorts than I am with pretty soldering. It's OK I s'pose.

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Good luck on your amp build,judging from what I see of your work up to this point in time,you are well up to the challenge.Of course you must already know that any amp that uses 12AX7s in the preamp and EL-84s or 34s in the power amp,begs to be run through Celestions-preferably Vintage 30s or Greenbacks-or for more cleanliness until really driven hard G-12-T-75s.

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Great soldering job indeed. [thumbup] I know how troublesome it can be to solder a short shield to a contact without melting the core's insulation, even with the use of knippers.

 

By the way, do you use leaded or lead-free solder? I found the latter much more difficult to handle when I modded my Gibson EB 2013 basses with three double pole/double throw push/pull pot switches each. However, I went with it since modern instruments are RoHS compliant, and I want them to stay so. When I modded the 1980s bass of a pal a few weeks ago, I used leaded solder since it was already used there. Generally, when repairing old amps or speakers, I use leaded solder for the same reason.

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Hang on a Mo'....

Lower-left. Isn't that a Gibson TRC screw?..................

 

P.

Looks like a Pozidriv screwhead, and a bit too large. The TRC cover screws feature Phillips heads and predate the Pozidrivs by far.

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Guest Farnsbarns

Hang on a Mo'....

Lower-left. Isn't that a Gibson TRC screw?..................

 

P.

 

 

Looks like a Pozidriv screwhead, and a bit too large. The TRC cover screws feature Phillips heads and predate the Pozidrivs by far.

 

I'm pretty sure he was joking. I started a thread about my missing TRC screw about a week ago.

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I'm pretty sure he was joking. I started a thread about my missing TRC screw about a week ago.

I was pretty sure for the same reason, too, but couldn't hold back. I had considered to also mention the obvious zinc plating instead of the nickel common on TRC screws... ;)

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Guest Farnsbarns

This is the phase inverter. Notice the opposite colouring of the wires in and out to reflect the inversion of the signal. The green wires are just the heater power.

 

IMG_20130823_162200.jpg

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