new guy seeks first build from donors

[droppedtuning]

hey guys newbie here seeking my first build. i have been reading up for a while and have decided to take the plunge. i have a hammond a0-29 and a magnavox cr717 as donors. i really only expect to use the transformers and tubes. i would like to build a non master volume 8-15 watt amp more of a vox sound than a fender per say. i realize i have 6v6 and 6aq5 tubes [ i also have el84's if needed} and not sure if the iron i have is even suitable for such a build. i am interested in slucky's dual lite amp        http://sluckeyamps.com/dual_lite/dual_lite.htm      . since its my first no trem or reverb just a good sounding vox chimey sound. All suggestions, schematics, help,info,etc will be greatly appreciated. thanks guys.

[shooter]

Here's an active thread on an AO-29 that may be helpful;
http://el34world.com/Forum/index.php?topic=20482.0

[sluckey]

The Hammond PT will give too much B+ for EL84s but has a big OT that will run EL84s nicely. The Magnavox PT gives nice voltages but the OT looks wimpy. So...

I would use the Magnavox PT with the Hammond OT. Use an octal socket for the rectifier, but probably use a ss plugin for higher B+. I think that combo would build a nice Voxy 8-15W amp.

But, I would fix the audio amp in the Magnavox before gutting it. It has a nice PI, PA  and PS in it already. Add an EF86 preamp tapped in where the radio volume control is and that would probably give a nice Voxy sound also. At least think about it before you gut it.

[Paul1453]

Vox uses EL84s for their sound I believe.

Doug has full plans for an 18W Stout, which might sound like what you want.

As a 1st time builder it is much easier to follow plans like this, than venture off on your own.

You could take parts from what you have, and buy the ones you still need from Doug.

That Hammond OT will work well with EL84s and Doug's Stout plans.
I have used a Hammond organ EL84 OT with good results on this.

You might have issues using your PT's with Doug's chassis, but you may be able to make one work.

If not, you've already got most of your output circuit parts, so a new PT shouldn't break the bank.   

[uki]

Greetings !

Welcome to the forum !

You gonna find some deep knowledge in this pages!

 

[droppedtuning]

thanks guys. i am looking for a lower wattage  vox or matchless sound, not really a marshall type . what i have may not be usefull. i want the  u2 chimey thing. i would love to use the 6aq5's if possible for more of a ac10 maybe

[Paul1453]

I really love the 6AQ5 tube.
It is extremely cheap compared to all other output tubes.

I know it can sound chimey, but that really has a lot to do with it's preamp.
I have a Bogen K10 PA conversion amp.
It uses 6AU6 12AX7 and PP 6AQ5 output.
But it doesn't sound very chimey at all.
It is more like a Plexi high gain monster.
It's circuit hardly plays clean and chimey at all.
It sounds fantastic for a tiny tube very high gain amp.
I think you really have to find the amp that sounds like you want,
and then copy that circuit exactly or you may not get the sound you want.

I've made 2 lower voltage 6V6 Plexi amps, and that little 6AQ5 K10 stomps on them as a high gain amp.
That doesn't seem to be the sound you are looking for.
The K10 is what the mud slinging Heavy Metal players around me really like, though. 

[Ed_Chambley]

First consider which Vox sound you are wanting.  Modern or Vintage.  If you want the real Vox sound, IMHO you need a EF86 and EL84's.  The reason is the EF86 is where that glassiness comes from.  It is actually odd order harmonics and that couples with how easy it is to get the El84 to distort especially if you are going for the 290 Plate voltage on them.


To me that is what makes Vox amps special, that and the VIB/Trem.  If using a 12AX7 as your first tube you could build a TMB Stout and set the middle up as a Raw control and still get more gain.


6Aq5 is a lot closer to a 6V6 than EL84.  I used 2 6Aq5 to build a mini Fender AB763 Circuit and is sounds very much like a Blackface Deluxe, just breaks up easier.  The breakup is much different tho.  The 6Aq5 begins breakup with a very noticeable change at the onset of distortion whereas the EL84 transition into distortion seems longer giving it a smoother distortion which to me is better for hard rock whereas the 6Aq5 seems better for Blues.

[jojokeo]

6Aq5 is a lot closer to a 6V6 than EL84.  I used 2 6Aq5 to build a mini Fender AB763 Circuit and is sounds very much like a Blackface Deluxe, just breaks up easier.  The breakup is much different tho.  The 6Aq5 begins breakup with a very noticeable change at the onset of distortion whereas the EL84 transition into distortion seems longer giving it a smoother distortion which to me is better for hard rock whereas the 6Aq5 seems better for Blues.

Ed, is this the amp you were considering appx a year ago to build a mini 10w Twin type amp?

[Paul1453]

Ed has given you another piece of the puzzle, that I wasn't quite aware of.

I knew that chimey sound came from the preamp, but not exactly which tubes could enhance it.
The EF86 is a pentode, like a 6AU6 is.  The 12A_7 series are dual triodes, a quite different amplification affect.

Ed's comment has made me want to maybe play with the EF86 and 6AQ5 on my breadboard.   

It is my understanding that the 6AQ5 is exactly a slightly smaller/lower output 6V6 in a 7 pin bottle.

I am thinking a slight modification to the K10 circuit might make a chimey sounding amp.
Maybe an EF86 on the input, 1/2 a 12AU7 as another gain stage, the other 1/2 as the PI, and a PP 6AQ5 output.
Or, I'm still learning the intricacies of the PI circuit part, no extra gain stage and use both halves of the 12AU7 as the PI.
That might produce a glassy/chimey sounding, around 10W PP 6AQ5 amp. 
PP output helps to cancel even order distortion, but will pass those odd order glassy distortions Ed mentioned.

[droppedtuning]

sluckey will my magnavox PT and hammond OT build your dual lite amp?.

[sluckey]

Probably

[Ed_Chambley]

6Aq5 is a lot closer to a 6V6 than EL84.  I used 2 6Aq5 to build a mini Fender AB763 Circuit and is sounds very much like a Blackface Deluxe, just breaks up easier.  The breakup is much different tho.  The 6Aq5 begins breakup with a very noticeable change at the onset of distortion whereas the EL84 transition into distortion seems longer giving it a smoother distortion which to me is better for hard rock whereas the 6Aq5 seems better for Blues.

Ed, is this the amp you were considering appx a year ago to build a mini 10w Twin type amp?

It is, but it was longer than that I think.  I sold it.  It was a great little amp and I built a cage for it and made a head into it.  Paired it with a oversized single 10 Celestial Gold cab and sold it to a friend who's son gets geetar lessons from me from time to time.


It really was a very cool amp.  I just picked up a Musicmaster Bass with the Push Pull 6Ag5 that I plan to make another one out of.


Stuckey built one too.  He used a old Hammond Reverb amp I believe and point wired it.  They are just smudge louder than a Champ, but will do a clean well.

[Ed_Chambley]

Ed has given you another piece of the puzzle, that I wasn't quite aware of.

I knew that chimey sound came from the preamp, but not exactly which tubes could enhance it.
The EF86 is a pentode, like a 6AU6 is.  The 12A_7 series are dual triodes, a quite different amplification affect.

Ed's comment has made me want to maybe play with the EF86 and 6AQ5 on my breadboard.   

It is my understanding that the 6AQ5 is exactly a slightly smaller/lower output 6V6 in a 7 pin bottle.

I am thinking a slight modification to the K10 circuit might make a chimey sounding amp.
Maybe an EF86 on the input, 1/2 a 12AU7 as another gain stage, the other 1/2 as the PI, and a PP 6AQ5 output.
Or, I'm still learning the intricacies of the PI circuit part, no extra gain stage and use both halves of the 12AU7 as the PI.
That might produce a glassy/chimey sounding, around 10W PP 6AQ5 amp. 
PP output helps to cancel even order distortion, but will pass those odd order glassy distortions Ed mentioned.

Push Pull cancels even order harmonics created by the power tubes, but any 2nd order harmonic created in the preamp gets amplified.    This is important in my book.


Actually the EF86 is the main component, but they can be harsh.  If I were using one in a 6Aq5 Push Pull I would try to get more headroom from the EF86 than Vox or Matchless so the 6aq5 will distort before the odd order harmonics hit and this should make the odd order sound glassy.


That is what I was getting at by saying the El84 might be better since the onset of distortion is more gradual and quicker.  The power tubes distorting with the EF86 sounds better to me.

[Paul1453]

So to get that extra headroom in my example, no extra gain stage before the PI would help the 6AQ5 break up sooner or later?

Also maybe that EF86 tube is the reason why I really like the sound of the simple EF86 - 6L6 SE amp I recently built.   

[jojokeo]

So to get that extra headroom in my example, no extra gain stage before the PI would help the 6AQ5 break up sooner or later?

Later, more gain stage(s) = less drive out of the '86 required for the same signal voltage level driving the EL90's. But there's more ways to use the '86 than a triode and this makes a difference in what you'll get out.

[Paul1453]

Thanks Jo.

That's what I was thinking.  I've never tried running the EF86 as a triode yet.

The simple EF86 6L6 circuit I like has the one pot as a master volume before the 6L6.

So to run a 6AQ5 as Ed suggested, where it starts to break up before the EF86 does,
it seems to me that adding another pot on the input of the EF86 as a gain control might be the solution to coordinating their respective break-ups.   

[jojokeo]

I was referring to the triode comparison with a 12ax or 12ay but the pentode used in triode mode is certainly one of ways and options in using it that I was referring to.

Others are plate & screen voltages, biasing, bypassing, loading, etc. which yield their influences on the character while also either increasing or lessening the tube's microphonic tendencies. They are a fun tube to play with & rewarding especially when you find your sweet spot. Preamp pentodes mimick power tube overdrive well and can be as nice in it's own way too?

[Paul1453]

Excellent info.

I guess I will have to experiment extensively with this EF86 on my BB.
I just got 6 more old Russian ones for $30 delivered last week.

My other 2 EF86s were Euro ones, but I did not notice much of a difference when I tested them in my 6L6 amp.
None of them seemed microphonic, as seems to be the biggest complaint against this versatile tube.
The old Russian ones might have overdriven slightly more to my ears.

Sorry if I have Hi-Jacked your thread.
Seems like this info on the EF86 might be valuable to you in your quest for chimey sound.   

[HotBluePlates]

It is my understanding that the 6AQ5 is exactly a slightly smaller/lower output 6V6 in a 7 pin bottle.

A 6AQ5 is exactly like a 6V6. Not smaller or lower output, but exactly like a 6V6. In fact, RCA's tube manual entries for 6V6 would tell you to flip to the 6AQ5 entry for curves.

The difference is the smaller bottle... You might not want to be as freewheeling with going over the published ratings on a 6AQ5 the way Fender did with 6V6's.

[PRR]

Curves are not Ratings.

Two sheets I just consulted show lower MAX plate voltage Rating. And the 10W p-p condition but not the 14W p-p rating.

Of course 6V6 are routinely over-volted. And we could wonder if the 6AQ5 "Max" was manipulated by the Marketing Dept so as not to gut the sales of 6V6.