Tweed Champ Based Ideas

[lkrasner]

I'm working on a little build based on the 5E1/ 5F1 champ circuit, and I want to add a few things just to give it some mojo or interesting features.

So far I'm thinking of a variable NFB, switchable bright cap on the volume knob. Could I make the first stage cathode bypass cap switchable, or would this not have a positive effect? How about a master volume to make it a bit more flexible for low volume use?

I know a lot of people around here have dabbled in something like this, so I'm just brainstorming.

[kagliostro]

You can steal from here



http://www.ampmaker.com/infocentre/forum-31-page-1.html



http://www.ampmaker.com/infocentre/forum-29.html

note that the N5X has two power tube sockets (1 x noval - 1 x Octal) but you can insert only one tube at time

and the Double Six (an amp that is considered by the autor very clean) uses two paralleled power tubes but you can install also only one socket and one tube (the OT must be adequate)

K

[shooter]

I did 3 5E1-ish amps, original, PSE 6L6, and KT88.  The guitar guys I had testing liked the PSE best, but to be fair, I sorta took a 5E1, a Gibson GA-5 and melded the two.

[lkrasner]

Would you recommend the 12ax7 preamp in the 5e1 and 5f1, or the 6sj7 one in the 5c1? Can someone explain the sound difference?

Check this out: http://www.tdpri.com/forum/shock-brothers-diy-amps/277341-6sj7-amp-build.html

[lkrasner]

I did 3 5E1-ish amps, original, PSE 6L6, and KT88.  The guitar guys I had testing liked the PSE best, but to be fair, I sorta took a 5E1, a Gibson GA-5 and melded the two.

What did you do to "meld" these. I just took a look and they are incredibly similar! only big difference is the 220K plate resistors.

[kagliostro]

Those 220k resistor make the difference

with 220k instead of 100k the gain is higher

K

[shooter]

I tried finding my schematic but all I got was the original, but my notes say I used 5e1 pre + tone stack and PA section from  GA-8(PSE) that I tweaked for 6L6,  and trem from a Gretch-something.  No neg feedback.  It was like my 2nd build and I was at the far left lower end of the bell curve   But she was pretty loud, got gigged at small venues by my Son, then vanished into his gear sale/swap void.

[Fresh_Start]

There are so many ways to go that it's hard to know where to start.

Yes, you can have a switchable bypass cap on the first triode. Adjustable feedback might be interesting, but a tone control would be way better IMHO. My first build was a 5F2A Princeton with a 10" speaker and I put a choke in before the plate node (like 5E2).

Notice that in the 5E1 the plate and screen grid are fed off the same node. At least put in a screen grid resistor if you go that route.

There are a lot of interesting single-ended amp ideas at AX84.com. Proven layouts too.

Cheers,
Chip

[lkrasner]

There are so many ways to go that it's hard to know where to start.

Yes, you can have a switchable bypass cap on the first triode. Adjustable feedback might be interesting, but a tone control would be way better IMHO. My first build was a 5F2A Princeton with a 10" speaker and I put a choke in before the plate node (like 5E2).

Notice that in the 5E1 the plate and screen grid are fed off the same node. At least put in a screen grid resistor if you go that route.

There are a lot of interesting single-ended amp ideas at AX84.com. Proven layouts too.

Cheers,
Chip

Thanks, I'm a big fan of AX84. I have a P1 Extreme with the adjustable bias and a 6V6 in the power section. It is an amazing sounding amp.

For this build, I have so far added a single tone control (right from the princeton), the variable NFB, and redone the power supply to be solid state rectified and provide a separate screen tap.

[Ed_Chambley]

Would you recommend the 12ax7 preamp in the 5e1 and 5f1, or the 6sj7 one in the 5c1? Can someone explain the sound difference?

Check this out: http://www.tdpri.com/forum/shock-brothers-diy-amps/277341-6sj7-amp-build.html

I prefer the 5C1 with a 6sj7 pentode.  I have one I use for testing tubes and I play it some as well.  The difference is the 5F1 has more gain, is louder and more harsh distorting.  The 5C1 is smokey bluesy sounding.  I also have a second input with a 12Au7, not bypassed cascaded into the 6sj7 for a lower impedance input.  Here I can really use effects and hit the front end very hard and get a lot of different tones.

I can also sub an EF86 in as well.  That said, most guys like the 5f1 because it does sound great distorting and pairs very well with single coils, but I find it to be a one trick pony.

[kagliostro]

a second input with a 12Au7, not bypassed cascaded into the 6sj7 for a lower impedance input

That is very interesting to me Ed_Chambley

So you have the input jack -> 12au7 -> 6sj7 -> and the remaining is the standard 5C1 circuit ?

of the 12au7 do you use a single triode or both triodes paralleled or which other configuration ?

Thanks

Franco

[Ed_Chambley]

a second input with a 12Au7, not bypassed cascaded into the 6sj7 for a lower impedance input

That is very interesting to me Ed_Chambley

So you have the input jack -> 12au7 -> 6sj7 -> and the remaining is the standard 5C1 circuit ?

of the 12au7 do you use a single triode or both triodes paralleled or which other configuration ?

Thanks

Franco

I just use half of the 12Au7.  Got the idea from John Shur a while back on one of the other forums.  I built it for a friend to use in his studio.  I did use regulated DC filaments and it is dead quiet.

Very easy to do.  Another thing is it sounds great with an acoustic guitar pickup.

I was going to use the other side for another input going to an EF86, but I just made an adapter. 

[Willabe]

I did use regulated DC filaments and it is dead quiet.

Ed, I know you've used a dc stand off (@70 to 80dcv) on filaments with very good results.

Did you get better results with the regulated DC filaments? If so how much better?


                Brad   

[kagliostro]

I was going to use the other side for another input going to an EF86, but I just made an adapter.

but I just made an adapter ??

I'm not able to follow you, please, can you explain ?

Thanks

Franco

[Ed_Chambley]

I did use regulated DC filaments and it is dead quiet.

Ed, I know you've used a dc stand off (@70 to 80dcv) on filaments with very good results.

Did you get better results with the regulated DC filaments? If so how much better?


                Brad   

Brad, this task was a combined effort and my friend wanted what he wanted.  I do not think making a regulated 6 volt power supply DC has any additional benefit.  I cannot say for sure since my personal Champ 5C1 has traditional filament with an artificial CT and a humdinger.  I believe adding additional filtration in the power supply does more for these circuits.  Also, I have begun using SS rectification with switching sag resistors for more options for studio work.

I read John speak so highly of the humdinger when using octal preamp tubes, I had to give it a try.  IMO this is the best way to go.  You have a quiet PA and preamp.

Buy yes, I have tried different methods of elevated filaments and have found a sweet spot where you suggested to me a couple of years ago. Now I just plan for it since it is so easy.  I have a couple of high gain builds and there is a noticeable difference in floor noise from an elevation above what the cathode will provide.  It is very much worth getting around 70vdc to elevate.

 I wish I had more time right now as I would love to get into the SE build DummyLoad had worked out.  I can say I much more prefer a EL34 single ended tone.

[Willabe]

Ok, I was wondering if you were experimenting with the regulated DC filaments.

Our friend tubeswell really likes the dc standoff with humdinger pot.

I'm going to try that next.


             Brad     

[Ed_Chambley]

I was going to use the other side for another input going to an EF86, but I just made an adapter.

but I just made an adapter ??

I'm not able to follow you, please, can you explain ?

Thanks

Franco

Sorry Franko for not being more clear.  If I had a schematic I would post it.  This was a joint effort between me and a friend.  To explain further, the 5C1 circuit is in a head design with loads of room.  We simply added to the stock circuit 1/2 of a 12A_7 tube like the return section of a loop.  I prefer the 12AU7 here, but most of the recording he is doing with it he is using a 12AT7.  He is a drummer, what can I say.

We had planed to use the other half to drive an additional tube, an EF86 and not have an effects send.  Instead I built an adapter so you can plug an EF86 into the same position as the 6Sj7.  The purpose is the EF86 sounds much better with overdrive, but the octal tube sounds much better with effects like Chorus, flange...etc.

Since I do not know much about recording and studio work, I was very surprised how nice a 10" speaker sounded on playback.  Definitely more like LA Rock tones.

[kagliostro]

Thanks Ed

now I understand what you mean about an adapter 


Ciao


Franco