tube PreAmp & FX into SS power PA

[Glennjeff]

Before I pull down the previous experiment to build tubenit's cct 2 posts up, thought I would document this simple experiment with schematic and sound clip.

This goes from transformer out, into desk then digital recorder, so its a reasonable representation of what the preamp sounds like through good monitors. The PA will colour the sound differently.

https://soundcloud.com/tags/guitar%20amp%20test%20tone

[jjasilli]

Great tone; well played too!  I agree that a SS driver is a fine alternative, especially since the signal is going into SS equipment anyway. 

[tubenit]

I can't seem to pull up the sound clip??

I get a page with all kinds of sound clips with 24 pages of sound clips in addition to that.

Can you repost the link or give a specific name to the sound clip?

I really would love to hear it! 

Best regards, Tubenit

[Glennjeff]

Working my end ???


https://soundcloud.com/tags/guitar%20amp%20test%20tone

Takes 10 seconds to get going though.

Try this one maybe ?

https://soundcloud.com/glennjeff/dmarscln2loz


OH and that is a 20 metre cable run as well.

[tubenit]

Wow! That worked! 

I like that tone ALOT!  Very cool sound. That would work out fine for me.

IF (& you sure don't have to), you try that with the trannie behind the OD section also, I'd love to hear that sound clip.

AND .......... nice playing!  Sounded really good to me.

THANKS so much!   with respect, Tubenit

[Glennjeff]

Don't know which thread I'm supposed to be using but here is the D'Mars OD channel with a Hi to Lo transformer hanging off the valve cathode followers cathode coupling cap.

There is no problems with level, I had to use a divide by 10 cable to stop it overloading a line input (-10dbU Line in I think)

https://soundcloud.com/glennjeff/dmarsod1

[tubenit]

There is no problems with level, I had to use a divide by 10 cable to stop it overloading a line input (-10dbU Line in I think)

I don't know what this means??   

Thanks for posting the soundclip!

With respect, Tubenit

[Glennjeff]

tubenit,

There was so much signal coming out of the transformer that it was overloading the line input on my desk. I had to use a cable that I have laying around for occasions when there is just too much signal. This cable has resistive dividers built into the plugs (XLR) to reduce the signal by a factor of 10. Some other posters thought that there might not be enough signal, so I thought I'd make the opposite observation.

What do you think of the sound coming out of the distorted channel ?, did the clips give you the information you required?

All the best.

[tubenit]

There was so much signal coming out of the transformer that it was overloading the line input on my desk. I had to use a cable that I have laying around for occasions when there is just too much signal. This cable has resistive dividers built into the plugs (XLR) to reduce the signal by a factor of 10. Some other posters thought that there might not be enough signal, so I thought I'd make the opposite observation.

What do you think of the sound coming out of the distorted channel ?, did the clips give you the information you required?

OK, got it. Thank you for the clarity.  I ordered both a 10k/600 and a 10k/150 trannie as suggested by Pete.

Given your explanation, perhaps the 10k/150  8.2/1 would be better at reducing the signal down to a manageable level?  IF I am understanding this correctly?

I thought the first soundclip of just clean was excellent/superb!  I thought this one with the distortion was really good but not as excellent. However, it could have simply been that particularly recording and playing?  I liked the guitar playing on the first one better also.
 

THANKS so much for the help and info!  I am starting to order parts on this and hopefully will being the build in the next 3 weeks or less.

With respect, Tubenit

[jjasilli]

Yes, there are 2 factors to consider for the source and receiving devices:  impedance, and voltage.  Typically the source impedance will be bridged (not literally matched) to the input impedance of the receiving device.  I continue to advocate for the 10K:600R tranny for prior reasons stated in both threads. 

As to the output voltage of the source device (FX loop) - you're building the circuit.  So you can control the output voltage by fine tuning the voltage going into the input (grid) of the 12au7 tube.

[tubenit]

Well, I hopefully will start building this in a few weeks and have it completed within a month out.  

I ordered both trannies 10k/600 & 10k/150 and plan to try both.

My goal is to build it ........... tweak it .......... and then report back the good success with the design.
 

We'll see if that happens or not?  

With respect, Tubenit

[tubenit]

OK,  guys I start on this project this wkend!  Got my parts from Doug and will build a board and hopefully punch out the blank chassis also.

Got a question. On the Edcor trannie ........... I don't know what to do with the CT on the input and output sides of the trannie?

Question 1:
Can someone help me out with that, please?  If you could post a schem or drawing that would be helpful to me.

http://www.edcorusa.com/Content/Manuals/XSM10K-150.pdf

My best guess is the CT on the output side hooks into the XLR jack in some manner?  

Question 2:
Also ......... I am thinking this trannie should probably be mounted inside the chassis do to the exposed terminals on the trannie?   On the other hand, I am thinking with shrink tubing that I could safely mount it on the outside of the chassis and cover the terminals on the trannie with several layers of shrink tubing?

Would the outside chassis approach with shrink tubing be reasonable?


With respect, Tubenit

[sluckey]

I don't know what to do with the CT on the input and output sides of the trannie?

The center taps are used if you are dealing with balanced inputs and/or balanced outputs. Your input is definitely unbalanced so just ignore the primary CT. And I'm guessing you're going to connect this unit to a PA unbalanced input using a standard guitar cable? If so, just ignore the secondary CT also. But if you want the common mode noise rejection advantages of balanced lines, then use a XLR jack and cable to connect to the PA. In this case, you would use the secondary CT.

If the transformer is small and fragile, I'd put it inside the chassis. I probably would not use heat shrink on the terminals but if I did, I'd only use one piece per terminal.

[tubenit]

if you want the common mode noise rejection advantages of balanced lines, then use a XLR jack and cable to connect to the PA. In this case, you would use the secondary CT.

Q1:
I am not sure how to "use the secondary CT".  I am guessing that all three secondary wires will hook up to all three XLR connections?   Is that correct?

Q2:
And that even with the XLR, I still will not use the primary CT. Is that correct?

As always, I truly appreciate the help. I am somewhat enthused about seeing if this idea will really work and sound good.

With respect, Tubenit

[sluckey]

Just google "how to wire an xlr jack" and you'll find plenty of simple diagrams for balanced operation or unbalanced operation. Here's a good link...

http://sommercable.com/2__produkte/2__130_support/340_belegungsplaene/belegungsplaene/nf_kabel.htm

I am guessing that all three secondary wires will hook up to all three XLR connections?

That's correct. The secondary CT would connect to the shield which should be pin 1 on an XLR jack. Then each end of the secondary would connect to pins 2 and 3 of the XLR jack.

And that even with the XLR, I still will not use the primary CT. Is that correct?

That's correct.

[tubenit]

Steve,

Thank you, my friend!  I appreciate the help. I'll look up the XLR wiring and figure it out. I'm looking forward to this experiment and challenge. 

Hopefully, within the next 3 wks or so, I can report back how this sounds thru a PA system?!

With respect, Tubenit 

[bibi]

Sorry, are you sure that is the correct way to hook up the output transformer?  I believe pins 5 and 8 on the secondary should be left "floating" for a truly balanced output.  The center tap is not used in this configuration, rather ground, or pin 1, should connect directly to the chassis. 

[sluckey]

Sorry, are you sure that is the correct way to hook up the output transformer?  I believe pins 5 and 8 on the secondary should be left "floating" for a truly balanced output.  The center tap is not used in this configuration, rather ground, or pin 1, should connect directly to the chassis. 

On second thought I believe you are correct. Thanks.

[kagliostro]

May be someone has interest to give a look to this Jensen schematics

http://www.jensen-transformers.com/as/as021.pdf

http://www.jensen-transformers.com/as/as096.pdf

from this page

http://www.jensen-transformers.com/apps_sc.html

and the attached schematic from Merlin

K

[tubenit]

Gentlemen,

THANKS for all the information!  I don't understand all of it, but from what I gather ............... I think this would be the way to hook up
the Edcor trannie to the XLR jack?

Q1:  Does that look like the correct wiring?        (if not can you revise the schematic for the correct wiring, please?)

Q2:  Does this look like a reasonable approach?        ( I added the V4a since so many illustrations had something similar.  Again, I am
        trying to preserve the D'Mars ODS  clean, OD & FX as close to original as I can).

With respect, Tubenit

[kagliostro]

Hi Jeff

as you use an XLR and a you have a transformer with a CT

why did you choose to don't use a balanced output ?

A balanced output has his advantages and is used in professional units

Franco

[tubenit]

as you use an XLR and a you have a transformer with a CT

why did you choose to don't use a balanced output ?

A balanced output has his advantages and is used in professional units

I simply don't understand how to hook up the wiring?   And I don't know what a "balanced" or "unbalanced" ouput is?  

I have no preference.  What would be actually helpful to me if someone could draw me a schematic for my Edcor and XLR?  I can understand a schematic, but I have limits to understanding the information that has been posted.

With respect, Tubenit

[sluckey]

There seems to be some mixed ideas about using the CT in a balanced XLR circuit, so I'll yield to the Jensen method. Pin 8 of the transformer should connect to pin 3 (not pin 1) of the XLR.

You don't have to use XLRs. A standard 1/4" phone jack works well too unless you have a very long cable run from your unit to the PA.

[tubenit]

Steve,

That is what I needed!!!        THANK you!!

I am going to go with that XLR wiring and use the added V4a  unless you direct me differently.
 

I appreciate that people are trying to help by providing information, but I don't understand significant portions of the info and at this juncture, I just needed a simple drawing to go from.

With respect and gratitude,  Jeff 

[kagliostro]

I'm sorry Jeff I didn't understood you at 100%

if you want to read a bit about balanced audio and convenience to use it

http://en.wikipedia.org/wiki/Balanced_audio

Franco

[tubenit]

Hey, no need to apologize at all.  

I should apologize for not being smart enough to understand what you were sharing!  And I do appreciate the info. While I may not understand all of it ............. I do continue to learn more.   THANKS!

 

I'll read about the balanced lines.

Best regards, Jeff

[kagliostro]

I do continue to learn more from you Jeff   

Franco

[tubenit]

Got the board populated.  Used Hoffman board and turrets.

Got the chassis blank punched out sanded and lacquered.

with respect, Tubenit

[PRR]

Agree: 99.44% of the time the CT should be ignored, even for "balanced" wiring.

HARD-Balanced (CT to ground) is sometimes preferable when working directly under a high-power transmitter. (Many old-old radio microphones were hard-grounded.)

In any other audio situation, let the winding "float" (no connection to ground). It will self-balance to suit the situation. It will also work if you (or the sound-dude) grounds one side for an unbalanced connection. (With hard-ground on CT, a ground on another lead shorts-out the signal.)

[terminalgs]

Agree: 99.44% of the time the CT should be ignored, even for "balanced" wiring.

With a small toggle switch, you can add a ground lift to the XLR pin #1.  This is handy in a recording situation to remove a ground loop hum, and perhaps less useful in a house PA mixing board situation, but still, its easy to add.  usually pin #1 is a 1Kohm Resistor to ground with a parallel .01uf cap, and the ground lift switch closes/opens pin #1 to ground.  In a "ground lift" position (i.e. switch is open) you've got a 1K and .01 cap to ground.  This shunts any RFI on the cable's shield to ground,  but eliminates a ground loop with the device at the other end of the cable.  Simple, and potentially very handy.

Also, on some 600CT transformers,  the OT's output leads can be switched/strapped for 150,300, or 600ohm, depending on how the CT is provided: some transformers separate the CT into two discrete wires,  others, use a single CT tap wire.  for an example of the former, google the wiring for a UTC A24.   Mostly this applies  to mike level inputs, and not so much house mixers, but in a recording studio, changing the ohm output from 600 to 150 can significantly change the frequency response ...  it depends on the device you plug into, and what the input Z of that device happens to be.   

[tubenit]

Guys,

It works as the last schematic I posted reflects.  Initial impression is that it sounds good to me.  I only had a time for a super quick plug and play without taking any time to adjust anything.  So far, I am pretty happy with it.

Will post some decent sound clips later.  This was done by just plugging into an EmU Tracker which goes into a computer soundcard.  Everything was on "5" except the volume which was "4" and the FX return which was "2".

http://www.soundclick.com/player/single_player.cfm?songid=12498845&q=hi&newref=1

Regarding the chassis layout. I built it so it could be converted into a complete amp at a later time IF wanted.

With respect, Tubenit

[tubenit]

OK,  here is a demo of snippets from 3 different "1-take" soundclips showing the D'Mars PreAmp into my E-MU Tracker into the computer soundcard.

This PreAmp will go into a solid state PA system.

Only effects were slight EQ and delay in the mix except for 1:15-1:30 where I tried a Zenith Drive pedal out.


http://www.soundclick.com/player/single_player.cfm?songid=12500662&q=hi&newref=1

With respect, Tubenit

[tubenit]

I got the D'Mars PreAmp up and running and recorded it into an E-MU tracker device into a sound card.

Seems like it would clip fairly easily (into the red) both in the E-MU tracker and in the Mixcraft recording program. For exampe, I had to record on "3-4" range out of 100 recording volume in the Mixcraft.

Any thoughts whether this would be a similar experience with a solid state PA system?  I am thinking there may be significant differences in how this sounds in a solid state PA vs. the computer sound card?

I am wondering IF I should use the 10k/150 trannie instead of the 10k/600 trannie?   Which would you suggest as a first try into a solid state PA system.  The 10k/600 is in there currently.

With respect, Tubenit

[kagliostro]

Think to the CF that is preceding the transformer as an FX Loop circuit

and insert a pot (not a big one, say 10k-25k) as to tame the signal from the tube to the transformer

---

See the last schematic on this tread

http://www.el34world.com/Forum/index.php?topic=13120.0

---

You can also try to connect the cap preceding the transformer to the node between the 1.8k and the 27k resistors

K

[tubenit]

Franco,

Those are very good ideas!  And I will try the pot first ( and then the other) and report back.  May be a few days before I can get to it.

THANKS!  With respect, Tubenit

[jjasilli]

Sounds great!

[Glennjeff]

That sounds REALLY GOOD Jeff. (Think I might have to re tweak my D'Mars OD section seriously.)

[tubenit]

Thanks for the encouragement, guys!     The PreAmp worked but sounded somewhat sterile and clipped too easily when trying to record.

I tried Franco's suggestion with the pot right before the matching transformer.  It worked !!!!

Ironically, I first soldered in a 25k but it lost so much volume that I added a resistor to ground and kept increasing that resistor to ground
until it sounded like the "right" volume.   

I ended up with a 1MA trim pot there with a 150k going into the trim pot.  The trim pot there made a difference in the warmth and sustain of the PreAmp.  I am thinking that what it ended up doing was to limit the clipping in the signal while allowing me to increase the FX level.

Anyhow, I have more warmth and sustain and it sounds closer to the real D'Mars PreAmp.  I also removed the bright cap on the volume pot too.

I will try one more tweak on the OD to get it a little smoother and more overdriven after work today and then post another schematic.

I feel pretty encouraged by the progress!

With respect, Tubenit

[tubenit]

I will post a new sound clip (hopefully) within the next 4-5 days after I finish tweaking this and learning a new recording program.

What I will do is have one sound clip with 3 sections. And anyone that wants to respond can rate each section A, B & C on a scale of 1-10 with 10 being a true full tube amp tone.

(ex: if someone thought it sort of sounded close but isn't really a full tube amp type tone, then they might give a "7". IF they thought it was a true tube amp then they can give a "10") 

Without knowing what is what, it could help in giving an unbiased review of the viability of this experiment/project?

After getting some responses, I'll give the results of which section is what.

I think it will be interesting to see how close I can get the tone of the preamp to a full tube amp tone?   Hopefully people will give me some honest feedback on it. IF it's not getting close to a convincing tube amp tone, I would want to know that (& also if it is close).

With respect, Tubenit

[silverfox]

Tubenit Wrote: "I think it will be interesting to see how close I can get the tone of the preamp to a full tube amp tone?"

Careful there Skywalker, The Darkside may be calling you...


Silverfox.

[tubenit]

Careful there Skywalker, The Darkside may be calling you...

 

[tubenit]

Guys, I would truly love your feedback.  I've tried working on the D'Mars PreAmp to tweak it as close as I can get to the sound of a full tube amp with the speaker mic'd.

There are 3 parts  A, B & C.  Each part is about a minute long.

IF you are willing to help participate in rating the success or failure or this project, just give feedback here on the soundclip thread:

http://www.el34world.com/Forum/index.php?topic=16065.new#new

Thanks & with respect, Tubenit

[kagliostro]

Hi Jeff

waiting for an answer from my son

I've remembered this italian project that may be of some interest to you

http://www.aresaudio.com/speaker-emulator.html



Ciao

Franco

[tubenit]

Thanks Franco!

Is that entire schematic the speaker emulator ............... or is a portion of that schematic the speaker emulator?

In other words, IF I was going to add a speaker emulator to this project, would I be adding a portion of that schematic or the
entire schematic?

Thanks.  With respect, Tubenit

[kagliostro]

The schematic is complete

at the link I posted you can read further and find PCB Layout

here a sample of the original

http://www.aresaudio.com/files/Audio-originale.mp3

and here the emulated signal

http://www.aresaudio.com/files/Demo-Emulato.mp3


I've read about this project some time ago in a forum, but now didn't remember if is to be used between guitar and preamp or in one other way

Franco

[tubenit]

OK,  thanks Franco!

Here is the updated schematic.

with respect, Tubenit

[kagliostro]

Hi Jeff

my son has listen the sample, he say that is difficult to give a response because what are you looking for

is something you can notice better when you play instead of when you listen

he say also that the best thing to do is to search to reach the most agreeable sound at your taste

there are many factor influencing the listen experience, however he say that at his taste

he feel the first part as more "electric", he like more and feel as more natural the second and the third part of the sample

From my part I ended to say that the part that I appreciate more is the third part but this is only my opinion and you know my ear situation

Franco

[tubenit]

PreAmp idea is scrapped!

I am dubbing this a noble effort with mediocre at best results ....................... 

Honestly, I had fun with this experiment but there was NO "wow factor" for me other then "wow, it actually makes sound".   

Project is labeled a quasi-failure!

Thanks for the input guys, sorry it didn't work out!

With respect, Tubenit

[kagliostro]

EH NO ! Jeff

Adesso ci spieghi cosa è successo  

After getting some responses, I'll give the results of which section is what

Now we are waiting

Despite of all, all the three section of the sample has a pleasent sound

only one was better from the other  

Ciao

Franco

[tubenit]

Results are in the sound clip section of the forum   

With respect, Tubenit