TC 8W Tube Amp Project

TomCat · 2009-07-10T18:13:17+00:00

Ok.....I decided to start a new thread following from Karel's thread about his 5W amp project. I've decided to go for a 8W Class A Amp head as a project. In summary: Channel-1: 12AU7 Pre for the clean channel (Hopefully I'll get enough gain to drive the O/P Tube properly), I/P Gain Control Only Channel-2: 12AX7 Pre for the OD channel, Gain and Volume Control Output Tube: EL34, No Volume Control. Use an output attenuator - Full 8W, 4W, 1W ALA Vox AC4TV style. Loudspeaker impedance 8 / 16 ohm selectable if possible with an output attenuator. Rectifier Tube: GZ34 Overall Bass and Treble EQ No Reverb or Termelo The main goal for this project is a guitar amplifier head that gives both clean as well as OD tones. Let me know what you think and wish me luck.......

aja

TomCat wrote @ aja

No problem....If I may make a suggestion, he normally does not do small jobs as he is geared up- for large production runs. However he is a good friend of mine and I used to bring him a lot of work so my suggestion is for you to come with me when you are ready and we go see him together.

What it it that you need?

Ah, I see! Thank you very much for the offer!
I am looking at building a dome ceiling cleaning robot next year, not quite sure yet. So I am trying to build up a list of contacts in case I might need them.

TomCat

Another update time.

As I needed to get some 6L6 tubes for my friends Deluxe, I decided to get a few more items for my amp at the same time so it was off to Mr Valve.

I now have all my tube sockets, spring retainer for the 6CA7 as well as a new JJ 12AX7 tube to replace the existing 12AU7 tube given to me by a friend.

I must say that Pia from Mr Valve was very friendly and helpful....full marks to Pia and Co.

I am now in the position to finalise my Chassis design and send off for the metalwork.

I am still debating whether I should go for an all aliminium or galvanised mild steel chassis.... ???....Personally I like the ideal of using Aluminium.

FenderBender

Great to hear things are gearing up for the big build Tom!

Regarding the enclosure, I'm currently repairing and modding a Peavey EVH5150 212 combo and noted they used mild steel for the "five and a bit" sided chassis. They then added a piece of right angled and screenprinted ally plate on top of the steel for the controls and jacks.
Another option for your faceplate is to use engraved traffalite sheet with a brushed aluminium finish. The cool thing is that the traffalite is manufactured with several colours available for the underlayer. I used brushed aluminium with a black underlayer for tube tamer.

Great thread. I'll be waiting in antici.......pation for your future posts ?

TomCat

Hi Graeme

Thanks for the suggestions. I'm thinking now of a steel chassis to help with magnetic shielding and electro-galvanizing it to give the finish.

I like your suggestions for the front plate and will look into that.

I'll keep you all posted on progress.

TomCat

After looking at my friend's Fender Hot Rod Deluxe amp the other evening I've decided to add another 12AX7 tube to the design to provide two more pre-amp stages to the amplifier for O/D / Distortion.

I'll switch these two extra stages in using a relay so that I can also use a footswitch to switch to distortion.

I also bought the rest of the small bits i needed for the build so the only items still needed is the power tranny and the choke, the relays and knobs.

Unfortunately things have got really busy between work and church activities so I'm not getting the chance to sit down to finalize my chassis design.... >☹ >☹

Holidays are coming soon...... :dance:

TomCat

Another Update

Iv'e finally managed to complete my Chassis design..... :dance:

Here are a few 3D images.

Top/Rear View

Top/Front View

Going for Mild Steel with a Cadmium Electroplate to make it look nice and shiny.

My final drawing has a few things slightly shifted around to fit things better.

guitarboy2828

Looking cool! ?

TomCat

OOOOkaaay!!!! Things are starting to move quicker now......Come Holidays..... ? ?

I've ordered my power tranny and DC choke......Thanks Karel

Ive also gone to see the metal pressing friend of mine for the chassis.....should get it in about a week. 1.6mm Mild steel chassis and electrogavanized....gonna look cool.. 8)

I'm also busy ordering the painfully expensive part.....the Celestion Alnico Blue......Ouch.....but i believe the tone will be worth the pain on my wallet.....

TomCat

Hey All

I was informed last Friday that my amp chassis was ready at the metalworks....went through on Saturday morning to collect it only to find that they had bent the chassis the wrong way.....Left was Right and Right was Left.....AAAARRRGHH...... >☹ >☹......was I frustrated.

Anyway, they promised to make and bend a new one for me and it is available today for me to collect......I'm holding thumbs that it is the right way round this time.....

I'll start posing pics soon.....

TomCat

I got my Chassis yesterday afternoon and all is well...they bent it the right way around this time. The electro-galvanize came out really well and make the chassis look really professional... ? ?

So here are some pics indicating progress so far.......

Chassis from the Top/Rear

Chassis from the Bottom

Fitted Tube Sockets, Pots and Switches

Tag strips, Power Caps (Still waiting for one Cap) and other bits

Things are taking shape really nicely. All the bits so far have fitted into the chassis nicely and looking good.
Next....I'm getting hook up wire and screened cable tomorrow.

I should have my power transformer and choke either by the end of this week or early next week.

FenderBender

Fantastic looking chassis so far Tom! I like the tag strips for all components. Looks quite rugged and neat too ?

I had Karel wind me up a 5k:4/8/16 trafo for a repair recently. Very nice work! It's so much better than the original little thing that had its laminations welded directly onto a mounting plate. If you haven't used him before, I'm sure you'll be happy with his work. What is the value of the cap you're waiting for?

TomCat

Thanks Graeme....Yup. I'm going for the tough/rugged finish on this one.....

I've ordered some extra caps from Matta...he is just waiting for more orders to make the shipping worth while....(Hint.... ?)

The cap I need is a 20uF/500V to supply the OD gain stage. No hurry as I can carry on with the clean stage and test the amp.....

matta

OH MY GOODNESS ?

Tom it looks insane!!! Well done mate, fan flipping tastic! It just goes to show what can be done. The metal work is superb. I need to get that companies contact details. Did you design the chassis yourself in CAD? You are most certainly a man of many talents 8)

The tag strip idea is cool as well, fiber/turret/eyelet boards look cooler, but for sheer DIY factor nothing beats a tag strip / point to point design.

Again mate, kudos, very impressive. RE the other cap, I'll get on it early next week, even if I have to just order your bits.

Cheers

Matt

Heath

that is starting to look stunning , i really like it , can't wait to see the finished product

TomCat

Thanks guys....really appreciate it. I've always had a simple approach to things and that is either go big or go home.... ? ?.

@ Matt....Thanks Matt.....Please don't put yourself out of pocket though for my sakes.....Please let me know what we can do and I'll come to the party....even if i need to order some extra caps to make up a more decent order....just give me a shout.....

Yes I did design the chassis in CAD......been a CAD user for many years and used to do a lot of 3D design so it was relatively simple for me to do...

CDee

Looking good Tom, can't wait for the sound clips.

Manfred-Klose

Tom@ did you keep track of the cost of all the parts? since you are not going to charge yourself for labour, would like to know how much such a project works out?
(including the chasis)

TomCat

I'll keep track of costs...although it won't be a true reflection of costs as some of the parts I got 2nd hand or given to me.

I'll however put in what they would have cost new to give some ideas.

I'll do it once I have finished the amp and all is working....

TomCat

Hiya all...

Ive just switched on the amplifier for the first time today and IT WORKS...... ?arty:

OK not perfect yet, but a guitar sound comes out of the loudspeaker in time with my strumming so I'm now very excited.

There are a few things to sort out...... :-\

1. Ive wired my Bass Pot backwards so it works opposite to what it is supposed to....easy fix there.
2. Got a strong buzz on the first pre stage...i.e before my volume control so I'm going to have to track that one down.
3. Tone bypass gives A LOT OF EXTRA GAIN so that will need to be tamed a bit.
4. The extra two preamp stages are not working yet as I need caps to complete the wiring. Thanks again Matta for organizing for me....cant wait to get that going.

Tone wise all sounds good so far although its hard to tell without the channel being totally clean (Buzz free). Seems to really respond well to the different PUP combinations and volume shifts on the guitar.

Also this baby has got some oomph.....can't wait to push it through my Celestion Blue when it arrives..... :bopping:

MikeM

I have been troubleshooting mine basically non stop since Saturday 2am ☹ Congrats..

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