• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

schematic to learn by

I'm looking for a circuit diagram to have and follow whilst studying morgan jones's book on valve amps. So that as I am reading I can also be trying to work out why certain choices were made or what bits do for this design.
Ideally it will be what I base my project on after finishing the book, should I feel ready... hopefully I will be able to adapt the design to become more of my own work as I go.
I plan to build a power amp, ideally putting out about 40w/c but I could cope with as low as 20w/c, so at my early stage of research assume it will have to be a push pull design. probably using el34 or el84's but nothing too big and expensive to replace.
Sorry if this question comes up a lot.
Adam
 
Much depends on what speakers you have ?

If they´re very low sensitive you need a lot of power otherwize a EL84 PP is a good starter.

There´s a big difference in cost of transformers(the main cost) between a small EL84PP and a 40+W amp.

Start with a smaller and basic amp for a start that way you´ll finish it in a reasonable time and get feel of how things work.

Once you get hooked only the wallet will be the limit :D.
 
Hi!

Have a look at my recent series of posts about a 6CB5A amp. Not PP but SE. I think SE might be a better choice to get into this. There is the schematic and also a description about each component:

VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 1

The later parts of this series go through component choice, detailed description of the construction steps and tests:

VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 2

VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 3

VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 4

VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 5

VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 6

Best regards

Thomas
 
Hi, thankyou for all the replies. Yes I'm still using a Mingda el34 integrated... which I have to admit I am still really enjoying, despite what some people had to say about it.

This amp outputs 40w/c which drivers my speakers no problem at all with plenty of power to spare. I've also used an 18w/c hybrid amp that began to feel a little strained when playing at higher volumes.

Thomas, thats a beautiful pair of amps you've made and could well be something I use. I didn't see what kind of power these produce... I'll admit i haven't read the whole thing yet as I'm at work.

I'm more interested in building in 2 stages, a power amp and then a preamp as oppossed to a integrated. I have a preamp I can use.
 
I have a preamp I can use.

Does that preamp have gain? If so, build an "El Cheapo" using a 6J6 in the splitter/driver "hole". Otherwise, use the 12AT7 shown. In any event, drop the volume control pot. You'll need decent, not guitar amp, O/P trafos, as your speakers (at a minimum) require the 12 WPC or so ultralinear mode "finals" yield.
 

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I'm going to be using a digital preamp with digital volume control, initially. and then eventually build a (probably valve) preamp.

The "el cheapo" looks to be a good simple circuit that will be easy for me to follow.. and I guess develop as I read and learn more... is it you own design?
 
I did the bulk of the "El Cheapo" design work, but other folks certainly participated. Dave Dlugos, AKA planet10, who is a moderator here, contributed and Jim McShane offers parts kits for the project. Quite a few of the parts values reflect Jim's stock for other projects. That allows for economy of scale and favorable pricing. :)

BTW, it is possible to use the same small signal circuitry with 7591 O/P tubes and get 30 WPC. However, as a previous poster indicated, the cost of the magnetics increases, substantially.

JMO, you will be better off with an "integrated" and not using a (shudder :eek:) digital preamp. Well executed "sand" analog I can understand, but not digital. If a "standard", 2 VRMS, CDP is used as the signal source, no preamp is needed to use an "El Cheapo".
 
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is that in the book? Maybe I haven't got to that chapter yet. He does a book on building valve amps as well (I think) is that worth getting to follow up or does the valve amp book cover everything I'll need.
At the moment I'm still working through the first bit on the supporting theory, working out values of resistors in paralle etc, and thought it would be good to have a diagram to practice on, that would eventually become the project at the end.... maybe I'll skip forwards a bit to find Morgans example.... I'd hate to spoil the story though.
 
There´s a big difference in building an amp to learn and explore the topologies for a start and building a 40W performance amp.

I think that something basic like a 6V6 SE is a superb starter.

You need 4 tubes 2x6V6 1x6SL7 1xrect tube) to explore most topologies.

a 5K SE transformer must be about the most bang for the buck you can get in SE OPT´s.

You can easily test Triode/UL/Pentode and different feedback.

Add a second gain tube and all kinds of circuitry including SRPP is available.

But it´s a choice for learning tube electronics not playing at party level.

But it will give a hole lot of tinkering fun for a reasonable amount of money.

It´s all down to choices, to start with a expensive and advanced amp can easily end in dissapointment when it hums and oscillates due to not perfect grounding and layout.

My no good advice is start with something basic and have fun, if you choose one of the amps made by members here you´ll get excellent support.

The first amp rarely becomes the showpiece you keep the rest of your life...mine never does :eek:.
 
...
So that as I am reading I can also be trying to work out why certain choices were made or what bits do for this design.
...

Well I am afraid you will need a spectrum analyzer for that which handles 20Hz-20kHz and they are pricey.

For DIY I would vote on SE parafeed. Tube sweet spot is low power (several watts) Class A amplification and Hi Sensitivity speakers.

In case it is gonna be your first Hi voltage B+ project major concern would safety precautions.

MagneQuest Transformers: DIY Schematics w/ MagneQuest Iron
 
You need 4 tubes 2x6V6 1x6SL7 1xrect tube) to explore most topologies.

I disagree about the vacuum rectifier. Grienacher, AKA "full wave", doubling the O/P of a Triad N-68X, which works in both "120" and "240" VAC zones, is far and away the most economical way to get an approx. 300 VDC B+ rail, for 2X 6V6 family O/P tubes. Execute the SS doubler correctly and it is every bit as quiet as vacuum rectification, while offering better bass performance.

The 6V6 family is large. The 12AB5 and 6CM6 are Noval based. The 7C5 and 14C5 are Loctal based. The 6AQ5 and 12AQ5 are 7 pin miniature types. Any of those, along with the Octal based 12V6, could offer NOS at prices lower than decent current production 6V6s command.

The 5751 is a possible, Noval based, alternative to the 6SL7.
 
I disagree about the vacuum rectifier. Grienacher, AKA "full wave", doubling the O/P of a Triad N-68X, which works in both "120" and "240" VAC zones, is far and away the most economical way to get an approx. 300 VDC B+ rail, for 2X 6V6 family O/P tubes. Execute the SS doubler correctly and it is every bit as quiet as vacuum rectification, while offering better bass performance.

The 6V6 family is large. The 12AB5 and 6CM6 are Noval based. The 7C5 and 14C5 are Loctal based. The 6AQ5 and 12AQ5 are 7 pin miniature types. Any of those, along with the Octal based 12V6, could offer NOS at prices lower than decent current production 6V6s command.

The 5751 is a possible, Noval based, alternative to the 6SL7.

I agree with you on the bang for the buck aproach.

But if you want to test topologies a tube rectifier has some attraction :).

With one chassi drilled for one octal gaintube per channel you can test most topologies without having to hackzaw it frequently.

Small adapter plates make the 7/9 pins fit.
 
I like the advice of building more than one amp, one to learn through making and one that I can make using the skills learnt that stands a chance of sounding good.
Also, making a single ended, low output mono amp could be quite usefull to me.. first of all to practice building something simple then to later modify and use in a mono system set up to give my mono vinyl a commited set up. As this currently comprises of nothing but the records I could easily plan to build a speaker to match the power of the amp.
OR
how about trying to recreate a classic, a marantz model 2 for example... prehaps this should come as the second project, or is an amp like that sort after due to it's classic status as oppossed to it's sound quality... would a replica now be a bit behind the times?
 
A basic SE 6V6 triode sounds very good if you have high efficency speakers.

There are several good designs around this forum so take some time and check around.

If you want a test bed for experimenting a small SE is a good start.

Going SS rectifier 4 tubes gives you the possibility to try most types of gainstages.