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Audio/Video Hardware => Valves/Tubes => Topic started by: Mars on August 13, 2019, 12:29:27 PM

Title: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 13, 2019, 12:29:27 PM
Hi All

We have decided to move the DIY workshop on to 18, 19 and 20 October. Anyone who is interested are welcome.

If you need a kit to build, let us know your needs. Kits are available at www.marsamps.co.za and we also do custom orders for your dream project.

If the kit you want is either not listed, or you would rather have a different kit/price range let us know, and we work out a solution.

Otherwise you can bring own project and work on it in the company of very able gentlemen who will help you every step of the way.

The workshop costs R1200 per day (or R2400 for the two day venture when you build a 18watt guitar amplifier or 70 watt hifi amplifier)

You'll need to bring your own soldering iron and basic tools.

We will supply a table, chair and power point + expert technical assistance.

PM for more information, or reply to this post.

Soldar en!
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 30, 2019, 09:07:13 AM
There has been requests for cheaper kits for the workshop.

Here I am looking at kit options that would be more affordable, and still deliver good sound. So feel free to share your impressions and/or needs.

Since the biggest cost is the transformers, push-pull kits give more bang for the buck. Single Ended kits like big iron and a big choke to boot.

Of the push-pull amps, you basically have the the following options:

1) EL84 push-pull (the cheapest is the ST35 style single preamp tube per channel)
2) 6V6GT push-pull with 6SL7 driver/phase inverter
3) EL34 push-pull
4) 6L6GC push-pull
5) any other tubes? FU32 push-pull?

Looking at cheapest output transformer options we have:

RS audio transformers:

6.6kΩ, 10W Push-Pull Output Transformer for Valve Amplifier
RS stock no. 123-7240 Mfr. Part No. D29A09F Manufacturer OEP

This could be used in an EL84 or 6V6GT amplifier: price + shipping = R1000

(https://media.rs-online.com/t_large/R1237240-01.jpg)

and

5.6kΩ: 4 Ω/8 Ω/16 Ω, 25W Output Transformer for EL34
RS stock no. 123-7237 Mfr. Part No. V78A01F Manufacturer OEP

This could be used in an EL34 or 6L6GC amplifier: price + shipping = R1500

(https://media.rs-online.com/t_large/R1237237-01.jpg)

Power transformers:

Most economical option is SWIFT toroidals A.F.A.I.K.  - I am getting quotes and will post.

I can also get quotes from SJ Andrews and other suppliers.

Point to point, or PCB assembly?

I see quite a few pcb's on offer for the amplifiers on our list. Would anyone prefer a PCB type kit? It seems to raise the kit price marginally, but assembly is relatively fool proof (really?) There we even have options of unpopulated and populated pcb's.

Comments will be appreciated.


Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 30, 2019, 04:48:13 PM
Next in line is the popular Mars Kit 1 Mk 2

(https://i1.wp.com/www.marsamps.co.za/wp-content/uploads/2019/02/Mars-Companion-3-1.jpg?fit=1024%2C732)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 30, 2019, 04:49:27 PM
EL84PP

(https://i2.wp.com/www.marsamps.co.za/wp-content/uploads/2019/02/Mars-Student-1.jpg?fit=672%2C480)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 30, 2019, 04:52:19 PM
Mars 5-10 stereo

(https://i0.wp.com/www.marsamps.co.za/wp-content/uploads/2019/02/Mars-5-10-1.jpg?fit=861%2C616)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 30, 2019, 04:54:14 PM
If you prefer KT88 - try the Companion

(https://i0.wp.com/www.marsamps.co.za/wp-content/uploads/2019/05/Marsamp-Companion.jpg?fit=961%2C628)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 30, 2019, 04:56:06 PM
If you want fixed bias and premium parts, then build the Performer:

(https://i1.wp.com/www.marsamps.co.za/wp-content/uploads/2019/06/fullsizeoutput_e29.jpeg?fit=900%2C600)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on August 30, 2019, 05:05:14 PM
Guitar amplifiers

5 watt Tweed Champ clone

(https://i1.wp.com/www.marsamps.co.za/wp-content/uploads/2019/02/5F1Kit_GuitarsPage_MarsAmps-1.jpg?fit=1024%2C732)

18 watt British style with plexi channel (or tremolo option)

(https://i1.wp.com/www.marsamps.co.za/wp-content/uploads/2019/02/18WattKit_GuitarsPage_MarsAmps_2-1.jpg?fit=1024%2C732)

or USA Tweed Deluxe

(https://i1.wp.com/www.marsamps.co.za/wp-content/uploads/2019/02/5E3-kit-assembled-1.jpg?fit=600%2C378)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Family_Dog on August 30, 2019, 07:27:32 PM
As a suggestion, an affordable, but nonetheless excellent, beginner's amp will be the Mars 5-10, which will present superb audio reproduction at a reasonable price and will drive many speakers without any problems.


-F_D
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on September 04, 2019, 12:26:42 PM
I realised that there may some people wanting to do a Single Ended amplifier? Since the wiring is less complicated than the other kits, this might be an attractive option for the workshop.

SET, DHT, 2A3, 300B or KT88/KT90 take your pick. PM me for pricing.

(https://i.imgur.com/MeT1VVR.jpg)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on September 05, 2019, 11:13:15 AM
Update: We have two participants for the workshop. Two more seats left. If you want to secure your participation PM me.
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: fredeb on September 05, 2019, 07:11:10 PM
I realised that there may some people wanting to do a Single Ended amplifier? Since the wiring is less complicated than the other kits, this might be an attractive option for the workshop.

Other than being less complicated than the other kits , Single Ended amplifiers also offer a more refined sound compared to Push-Pull amplifiers which offer higher power . Single Ended amps are more likely to be paired with high efficiency loudspeakers .
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Qualityten on September 09, 2019, 12:46:15 AM
I can recommend the 6k6 transformer from RS Components for EL84 builds. The SA price is cheaper than in the UK.

For participants wanting to learn how Amos is irk, i would also recommend point to point construction. It helps beginners to see exactly what is connected to what. This aids circuit understanding and makes repairs easier.
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on September 09, 2019, 11:56:38 AM
Following on the different kits available:

Here you can see the inside of a Kit 2 Mk 2

(https://i.imgur.com/iU6KdLC.jpg)

And this is a SE88:

(https://i.imgur.com/AeLoXhx.jpg)

And this is the Mullard 5-10 stereo:

(https://i.imgur.com/KIXd3sa.jpg)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on September 19, 2019, 12:51:18 PM
UPDATE:

It is just under a month till the workshop. Anyone still wanting to be included should PM me a.s.a.p.


If all goes well there will be a Tube T-shirt for all attending.

Venue tentatively in Randburg at Wheelwell. I took a few photos of the venue.

(https://i.imgur.com/r29yYNT.jpg)

(https://i.imgur.com/wLPJCDc.jpg)

(https://i.imgur.com/h3grDCQ.jpg)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on October 07, 2019, 10:25:00 AM
Hi All

We are moving the workshop date on towards 15&16 November to allow more people to come on board. Ideally we would like to have two hifi and two guitar amp projects. But the choice is yours. Book now to build your own Christmas present.


Photo from previous workshop in Pretoria.

(https://i.imgur.com/uFyzyxi.jpg)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on October 09, 2019, 10:57:28 AM
Our kits are wired "point-to-point". Here is a great article on the technique:

http://mmiworks.net/sprc/SP11-Sawyer.pdf (http://mmiworks.net/sprc/SP11-Sawyer.pdf)
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on October 18, 2019, 10:02:37 AM
Someone is doing similar courses in Great Britain.

http://vyseamps.com/training-courses.html (http://vyseamps.com/training-courses.html)

From the page:

The most important thing is to select a suitable project. There is a huge range of amplifier kits to choose from, with multiple options, so you really can design your perfect amp. However, take care not to be too ambitious. You must get the most out of the teaching time. Experience has shown that one needs to focus on learning the basics. Get the electronics right and at first build the core model from which your amp derives. Having mastered the ground skills you can then go on to add extras like reverb, effects loop etc if required. You should leave the course with a fully working amp, but for some projects you may have homework to add extra features. You will have learnt the skills to do this work and support is always on offer.

and maybe something to look at for me...

Beginners can also be sent a practice kit to try some soldering etc before the course.
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on November 07, 2019, 12:01:16 PM
Hi All

We are finalising arrangements for the workshop coming up. If you have an interest in this, PM me a.s.a.p.
Title: Re: DIY tube amplifier workshop in Gauteng - October 2019
Post by: Mars on November 19, 2019, 09:23:36 AM
Hi All
The workshop in Gauteng has been postponed to 2020; dates to be confirmed. Apologies to those following the thread. Too few participants were available to host a decent workshop.

We are still doing workshops in Paarl till later in December, so when you're in the Boland, take a break from the wine route,  and come build your own Christmas present.