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.......

TomCat

Alan Ratcliffe wrote Ya think? ?

Actually, I've got a good RCA NOS EZ81 in my Vox and generally the NOS rectifiers last decades. I'm more interested in sourcing some NOS Mullard or Brimar 12AX7s.

Phew....That means I now have a second one for my next project...... 8) 8)

aja

How are things going with this, Tom?

TomCat

Things are going a little slow on the amp at the moment. Busy with work stuff.... >☹

Busy assembling all the parts together....next month I'm getting the transformers.

Once I have these I will be able to finalize the chassis design.

TomCat

Update time.

Ive managed to acquire two second hand OP transformers. These are Hammond 125ESE that someone had in their HiFi and has updated these to wider bandwidth units. I also got a pair of brand new matched 6CA7's chucked into the deal as well..... ? ?

Currently busy with the chassis design in 3D CAD...I'll post some images soon when the chassis design is complete.

Just looking for the power Tranny and choke now......hope to get these soon as I'm starting to seriously GAS for this amp now..... ?

guitarboy2828

Just an FYI... My dad is a techinician, and he is old.. So he has a box full of old tubes.. I know he has 4 Mullard EL-34's.. He was going to build me an amp with them, but never got around to it. There are a bunch of others, who knows what...

Reason for mentioning it, I'd be willing to donote/sell for a low price to TC or someone else doing projects like this. I'm not sure at this point that I'll ever use them and it's a waste to leave them lying in a box. I don't have them at the moment, so don't nkow what is in the box, but will take some pics and write down the names and post them on here. TC if you can use them, PM me and we can make a plan! ? All in aiding out fellow muzo's hey! ?

TomCat

Thanks....looking forward to seeing what you got....

AlanRatcliffe

I'd kill for some Mullard or Brimar 12AX7s. But you should really evaluate what you have and see what kind of value they have. NOS power valves in particular and brands like Mullard and Telefunken can be worth quite a bit.

I was fiddling with both my amps yesterday, swapping out preamp valves left right and centre to get the best from both amps. Can really make a difference (especially with the Vox, the Twin is too clean to make a huge difference). Ended up with all Telefunkens in the Vox aside from a Philips in V1 of the Top Boost channel.

The Twin ended up with a real mix of Philips, Siemens, AEG and notably an RCA 5751 as phase inverter, which made quite a difference (It had a 12AX7 before, which was really killing the tone). I don't have a single 12AT7 for the reverb driver though, so I've got a new EH 12AU7 in for now - works, but Fender reverb circuits put a lot of stress on the valve apparently, so I want the right thing in there..

TomCat

Small update time..... ?

Getting my O/P Trannies and valves either today or tomorrow..... ? ?

Busy placing order with Matta for my Caps. Karl is going to do my Power Tranny.

Loudspeaker wise I've decided to go the whole hog and get a Celestion Blue for the cabinet.

Another small mod I'm including is a tone defeat switch to bypass the tone stack. Thinking of making it a relay so that I can use a footswitch.

Manfred-Klose

tom, where are you getting the speaker from?

TomCat

Ok...Got the O/P trannies and Valves yesterday afternoon.....All arrived safely and looking good.

@ Manfred
The Celestion agency is in the process of changing....apparently Philtron have lost the agency...NOT SURPRISING...... >☹ >☹

The new agents are getting stock in around November (Including Guitar Loudspeakers.... :dance?......Chat to your local Music store as they should have been contacted by the new distributor already.

FenderBender

Great to hear that you are making good progress Tom. Also, with your amp design and the new speaker agencies, it seems like SA is getting on the map with parts and gear availability ?

[deleted]

When are you going to start taking orders? ?

Looking forward to see the pics when you start putting it all together and then the sound clips!

Good luck, hope it's going to sounds as good as it looks here!

MikeM

What speaker agencies? ?

Dumb question, missed that post. Wonder what pricing will be like

TomCat

Brentcgp wrote When are you going to start taking orders? ?

Looking forward to see the pics when you start putting it all together and then the sound clips!

Good luck, hope it's going to sounds as good as it looks here!

I hope so too.

I'm really looking forward to completing the project now......just cash is slowing the process.....know what I mean.... >☹ >☹

TomCat

Time for another update.....

I just got my Caps from Matta........All arrived safe from Cape Town....Thanks Matta

I'm now getting really excited about the amp now.

I now have the following:
1. All Tubes..including some extras
2. O/P Transformer plus a spare
3. All the Caps
4. Mains Input IEC Socket with fuse holder
5. 80% of a chassis design
6. Lots of excitement..... :woohoo:

Still need to get:
1. Power Transformer....talking to Karel at the moment
2. Power Choke
3. A completed Chassis
4. Tag Strip
5. Tube sockets
6. Pots, switches and lamps
7. Chicken head knobs
8. Make up the cabinet

The loudspeaker cabinet will be separate and will be using a Celestion Blue in the cab.

Gearhead

TomCat wrote cash is slowing the process

TomCat wrote will be using a Celestion Blue in the cab

¿Que? If cash is the limiting factor in progress, Blue's are going to slow the whole thing down enormously... It's your choice dude, but should you not want to go for something second hand, cheap and okay-ish just to get it working?

matta

TomCat wroteI just got my Caps from Matta........All arrived safe from Cape Town....Thanks Matta

My pleasure! Glad they arrived safe and sound.

TomCat wroteI'm now getting really excited about the amp now.

Still need to get:
1. Power Transformer....talking to Karel at the moment
2. Power Choke
3. A completed Chassis
4. Tag Strip
5. Tube sockets
6. Pots, switches and lamps
7. Chicken head knobs
8. Make up the cabinet

The loudspeaker cabinet will be separate and will be using a Celestion Blue in the cab.

I can help with the sourcing the sockets, switches, lamp etc and I may even have a couple new Black Chicken heads I'll throw in for free if you would like as my contribution to your first build? RE Chassis, I know Karel uses some pre formed aluminum for his, maybe use this as a starting point and then just add a trafolite engraved panel over it for more 'wow' factor.

Can't wait to see/hear the end results!

Cheers

Matt

TomCat

matta wrote
TomCat wroteI just got my Caps from Matta........All arrived safe from Cape Town....Thanks Matta
My pleasure! Glad they arrived safe and sound.

TomCat wroteI'm now getting really excited about the amp now.

Still need to get:
1. Power Transformer....talking to Karel at the moment
2. Power Choke
3. A completed Chassis
4. Tag Strip
5. Tube sockets
6. Pots, switches and lamps
7. Chicken head knobs
8. Make up the cabinet

The loudspeaker cabinet will be separate and will be using a Celestion Blue in the cab.
I can help with the sourcing the sockets, switches, lamp etc and I may even have a couple new Black Chicken heads I'll throw in for free if you would like as my contribution to your first build? RE Chassis, I know Karel uses some pre formed aluminum for his, maybe use this as a starting point and then just add a trafolite engraved panel over it for more 'wow' factor.

Can't wait to see/hear the end results!

Cheers

Matt

@Matta

Thanks...I really appreciate that. I'll PM you the details.

Regarding the chassis I have a good friend up here in Jozi who owns a large metal pressing and metalwork factory. He has done a lot for me in the past and I'm getting him to punch/press/bend the chassis for me from aluminium.

I'm designing the chassis in 3D on CAD. Once I'm done I'll post the images for all to see.

aja

TomCat wrote
matta wrote
TomCat wroteI just got my Caps from Matta........All arrived safe from Cape Town....Thanks Matta
My pleasure! Glad they arrived safe and sound.

TomCat wroteI'm now getting really excited about the amp now.

Still need to get:
1. Power Transformer....talking to Karel at the moment
2. Power Choke
3. A completed Chassis
4. Tag Strip
5. Tube sockets
6. Pots, switches and lamps
7. Chicken head knobs
8. Make up the cabinet

The loudspeaker cabinet will be separate and will be using a Celestion Blue in the cab.
I can help with the sourcing the sockets, switches, lamp etc and I may even have a couple new Black Chicken heads I'll throw in for free if you would like as my contribution to your first build? RE Chassis, I know Karel uses some pre formed aluminum for his, maybe use this as a starting point and then just add a trafolite engraved panel over it for more 'wow' factor.

Can't wait to see/hear the end results!

Cheers

Matt
@Matta

Thanks...I really appreciate that. I'll PM you the details.

Regarding the chassis I have a good friend up here in Jozi who owns a large metal pressing and metalwork factory. He has done a lot for me in the past and I'm getting him to punch/press/bend the chassis for me from aluminium.

I'm designing the chassis in 3D on CAD. Once I'm done I'll post the images for all to see.

Please give me the metal guy's details if you dont mind, I might need him beginning next year! Thank you!

TomCat

@ 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?

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