Building a tube amp. Questions----->

[zeegler]

So I've decided that for my next project, I am going to build an amp from scratch. I have seen many sites selling kits, or just parts, or just the basic plans. I think this would be a good place to start, since I am learning as I go.

My question is, since all of the kits and plans seem to be based on existing/vintage amplifiers, which one should I build? I want a 50 watt, high gain amp, and it HAS to have a master volume. I don't want to have to crank it to get a decent sound, or have to use a power attenuator. It needn't be fancy, in fact a single channel would do to start with.

Someone point me in the right direction. [img]images/icons/smile.gif[/img]

[CZSER]

Re: Building a tube amp. Questions----->

Well Zeg, from my own experience....
The SLO clone I build (I'll replace te burned power tranny this week end) sounds good at vol 6 to 7.
If you want that round/non-harsh sound you need power stage saturation more than pre-amp gain (gain=overdrive or distortion).
As I told you before, the facts involved here are:
* the B+ voltage supply(power tranny involved)
* the plate to plate load (output tranny impedance)
* tube type (some crank up earlier than others & sounds different also)
* bias current.
All this is reflected at the tube's load lines
To avoid this design/calculation nightmare I would recomend this (unless you want to experiment or get deep in designing power amps):
Build an amp from schematics, BUT choose a model that you can buy direct replacement power & output trannies (also choke).
This assures you a prooved design
BTW, SLO is one of the easiest designes I found & schems availables includes the power supply and bias voltages, but not the OT load plate, for this u shold buy a replacement OT.

[CZSER]

Re: Building a tube amp. Questions----->

I forgot, I included a pentode triode mod in my amp, stolen from Marshall 6100 schem i think. This mod reduces power a half: 50->25(still loud for bedroom) cos 1/2 power doesnt mean 1/2 decibels
BTW, glad to hear you're steppin' the path [img]images/icons/wink.gif[/img]

[zeegler]

Re: Building a tube amp. Questions----->

Originally posted by CZ V-KNIGHT:
I forgot, I included a pentode triode mod in my amp, stolen from Marshall 6100 schem i think. This mod reduces power a half: 50->25(still loud for bedroom) cos 1/2 power doesnt mean 1/2 decibels
BTW, glad to hear you're steppin' the path [img]images/icons/wink.gif[/img]

<font size="2" face="Verdana, Helvetica, sans-serif">LOL, I'm gingerly testing the waters at this point. I have a few questions. I have never owned or even played a Soldano. Let's hear the specs on your amp. What is the power output? What does it sound like? Is it single channel? is it master volume? What is the oputput impedance? blah, blah, etc......

[Twisteramps]

Re: Building a tube amp. Questions----->

Don't take this badly, but building a high gain amp for your first build is a mistake imho unless you really know what's going on.

Just my opinion, prove me wrong.

Pete

[yabba]

Re: Building a tube amp. Questions----->

I'm speaking from a position of much less knowledge and authority than Pete, but I was goign to say the same thing; for your first build it's probably better to keep it really simple (something like the p1 at ax84 )

you can always mod the crap out of it later, and since it's small and simple, it's also relatively cheap.

[edit: plus I'm biased and I love really tiny amps like that [img]images/icons/grin.gif[/img] (although 5 class A watts is actually pretty loud) because you actually can crank it and get power tube saturation while keeping things at a reasonable volume level. I'm currently collecting parts for 1.5 watter [img]images/icons/smile.gif[/img] ]

[ June 12, 2004, 11:04 PM: Message edited by: yabba ]

[CZSER]

Re: Building a tube amp. Questions----->

FIRST OF ALL: don't let anyone tell you can't.
Second: Never heared a SLO (live in Argentina), but my amp beats any Marshall 900/2000 Series by FAR.
At the original SLO(gain-bass-mid-tre-vol+presence), when lead channel is active, clean channel stills active, so I used optoacouplers(also home made [img]images/icons/wink.gif[/img] VATEC style)to make a "Y" optical switch(no mechanical switches in the signal path to avoid "Pop/click" swich noise) & turn clean channel out off. Also duplicated the entyre control panel, now indeppendent for each.
Power output is: 100/50 (Two or four tubes: you need dual impedance @ primary windings + interconection digital relay contoled sistem) + Pentode/triode: full or half power with both 2 or 4 tubes.
Now runnig all Fender(sovtek) 5 x 12AX7 & 2 x 5881WXT (6L6 "GC" alike) read Sovtek 5881WTV & bias
ASAP I'll get replaced them with JJ
Since SLO POWER STAGE is a tipical Fender POWER, I winded myself my tranny like a tipical Fender tranny but a bit hotter: 4400-2200 ohms for 2 or 4 tubes.
How it Sounds with crappy Sovteks? Beats all JCM900 & JCM2000 [img]images/icons/grin.gif[/img]

[Twisteramps]

Re: Building a tube amp. Questions----->

I think what you've done is great, but 99.9% of people wanting to build an amp aren't going to have the ability time or desire to hand wind their own transformers... and the fact that you did that shows you're pretty high up the food chain as far as knowledge goes.

Someone just walking into this hobby really should stick with a low gain, low power, single channel amp in my opinion... otherwise they are going to end up so frustrated that the amp they start will never be finished.

Would you recommend a beginning guitarist start off with a few simple chords or trying to learn Black Star by Yngwie?

Pete

[Twisteramps]

Re: Building a tube amp. Questions----->

Oh, a few things that copying a schematic isn't going to tell you:

How to wire the heaters for the tubes, including the best way to cut noise if you don't have a center tap on your power transformer. Most schematics won't even show the tube heater wiring, because you should know that already if you're building an amp.

Grounding, which could fill a book by itself - do you want a buss system? Or Star? Which way is going to provide for lower noise?

Placement of parts - the schematic won't tell you where to put the transformers in relation to the tubes in relation to the power supply wiring for lowest noise and oscillation/hum

Where shielded wire should go, and how it can cut noise drastically... Heck, even how to wire the input jack properly isn't mentioned on schematics. They don't tell you that the 1M resistor usually on the input should be wired directly on the jack, and the 68k that most amps have should be put directly on the tube socket for lowest noise.

A schematic won't tell you any of this, but if you build an AX84 P1 you can learn this stuff and more and also have a common reference to ask other builders questions on their BBS, and even buy a kit with the chassis predrilled from Chris Hurley at Doberman Amps.

Pete

[Tetsuo]

Re: Building a tube amp. Questions----->

Would you suggest building a Poweramp as a first project?

[CZSER]

Re: Building a tube amp. Questions----->

Well noooowww, Pete. I did not have specific knowlledge at first, but every single thing you mentioned I'serched the web, readed a lot, talk to people at forums (every night for almost a year) & finally cleared all my dubts BEFORE Start making PCB schems. Not telling every experiment was success, BUT I DIDN'T HAVE THE MONEY TO BUY A TUBE AMP; I managed myself to get what I wanted!
U SHOULD KNOW: People at forums are really helpfull.
Other Fact: Here in Argentina is almost immposible to find printed data, manuals or any reference in tubes theory, but once again: you fix your own limitations & you beat them too!

[Twisteramps]

Re: Building a tube amp. Questions----->

There's a key phrase right there... "every night for almost a year". Most people who want to build an amp aren't going to want to gather knowledge for a year before they dive in... a simple kit will show them many things that they will need on a more complex build like yours, and really, may be faster in the long run towards the amp of their dreams. Also, if you used previously designed PCBs instead of reading a schematic and having to come up with your own layout, that's a pretty good shortcut right there.

Maybe it's just because I'm spoiled with the availability of cheap tube amps in the USA, but you'd have problems building a soldano clone with the correct transformers (which aren't available anyways... just try getting DeYoung to sell you a set of custom Soldanos... hell, Mercury won't even sell you a set of custom HotRod transformers!)

let's say you bought a set of 100 watt plexi transformers from Mercury Magnetics... for the cost of those transformers alone, I can recommend several tube amps that sound good. For the price of a punched chassis, all components, transformers, etc... you could buy many different amps. for most people, building an amp from scratch costs MORE than buying a similar amp. It's not really the best way to get a cheap amp, at least I haven't seen it. Also depends on what your time is worth too, of course.

Pete

Originally posted by CZ V-KNIGHT:
Well noooowww, Pete. I did not have specific knowlledge at first, but every single thing you mentioned I'serched the web, readed a lot, talk to people at forums (every night for almost a year) & finally cleared all my dubts BEFORE Start making PCB schems. Not telling every experiment was success, BUT I DIDN'T HAVE THE MONEY TO BUY A TUBE AMP; I managed myself to get what I wanted!
U SHOULD KNOW: People at forums are really helpfull.
Other Fact: Here in Argentina is almost immposible to find printed data, manuals or any reference in tubes theory, but once again: you fix your own limitations & you beat them too!

<font size="2" face="Verdana, Helvetica, sans-serif">

[Twisteramps]

Re: Building a tube amp. Questions----->

Originally posted by Tetsuo:
Would you suggest building a Poweramp as a first project?

<font size="2" face="Verdana, Helvetica, sans-serif">No, because I can't think of any poweramps that are in schematic form that would be easy to build. You'd have to be able to either design one from scratch, or crib parts of your design from several different sources, and be able to shape it tone-wise as to what you wanted.

Just my opinion, I'm sure the soldano builder in this thread will disagree [img]images/icons/smile.gif[/img]

Pete

[Tetsuo]

Re: Building a tube amp. Questions----->

Schematics are for the weakminded I can easily build one with no experience at all with no schematic and I can have it done in under 2 hours total time Okay enough of fantasy land time I'm just going to buy amps like you suggested. I am the guy that would get so mad that the amp would meet the concrete in my workshop

[CZSER]

Re: Building a tube amp. Questions----->

Ok Pete, you've got your point, not a simple task at all. Some skills are required, but by walkin you make your path.
Coulden't get VATECS anywere.
SO I ALSO MADE THEM MYSELF. After a day of tests I came out with an optoacoupler better than original VATEC (sealed in epoxi putty [img]images/icons/grin.gif[/img] ). Just an example to show how yor limited resourses push you to achieve your goals OF COURSE WITH LOTS OF EXTRA EFFORT! Would be easier to go to RADI-o-SHAC store and buy them.. [img]images/icons/tongue.gif[/img]
You need dedication, effort and no givin up (no matter the problems that ALLWAYS come out)attitude to reach your goals.
BTW. PCB (new process I used. [img]graemlins/laugh.gif[/img] ), metal chasis, wooden head housing, tolexing, even speaker cab, made it all myself.
Once again, didn't have the money, and if I would had it, here wouldn´t be available to get. So I HAD TO do it myself.
The biggest pain in the ass is the fact tha the best tubes i could get were Sovteks [img]images/icons/mad.gif[/img] . Can't wait till I get enough cash to import JJ's!