Question about voltages vs compression and some rambling

[proaudioguy]

http://www.el34world.com/charts/valve/ValveData.php?e=view&f=13013

Is there any way to get the compression of the Deluxe Reverb and Princeton Reverb in the Twin Reverb?  I assume much of it comes from the use of tube rectifiers on the smaller amps.

I'm looking for a silver bullet here.  I'm trying to avoid the GAS.  I have my finger on the trigger to order a Deluxe Reverb kit.  Even the Deluxe Reverb would be too loud for the house.  The twin on 3 or 4 is too loud for wifey.  She wants me to move it to the garage.  Even at that low level which is comfortable for my ears, it doesn't have enough compression.  Pedals suck.

I'd love to get input on this.....

Here's an alternative idea but fuels my GAS.

What are your thoughts on building a Deluxe AB763 (1 channel) in a modified Princeton combo chassis and cabinet?  Modified in that it would use a 12" instead of a 10"?  It would be a little smaller, have only 1 channel, but would it sound like a deluxe?  I could give up the tremolo (since I have the twin for that) and use that tube for the Deluxe PI, right?  That would leave me with half a tube leftover, wouldn't it?  Could/should I use that for an additional boost OR effect's loop or just leave it unused?  Is this a stupid idea?  Is there a way to reduce the power further without losing the tone?  Would dropping the voltage before it even hits the rectifier help lower the volume?  Back in the day guys in the studio used variacs.  At some point folks said it was bad for the amps.  I don't know if that's true or if it was bad because more and more solid state amps were being used.  Would dropping the voltage to the power tubes OR the rectifier lower the output power and increase the compression at a given volume?

Thanks

[John]

Have you considered a small SE amp? I don't know exactly the tone you're going for since I'm not that familiar with the different amps. (grew up with solid state Peavey... oh, the shame) Anyway, I built one out of an old Webster carcass. Paralleled 12a_7 into a 5879 into a 6v6. It sounds great, even at very low volume with tons of sustain. To avoid drilling another hole (pure laziness) I did away with a tone knob, and instead have a "gain" pot on each preamp tube. It might very well not be the tone you're looking for but I love it. The only thing lacking is some treble which I know you Fender guys love  but you can tweak that with the bypass and coupling caps I believe.

This probably answers none of your questions, but oh well. 

[Tyrannocaster]

Is there any way to get the compression of the Deluxe Reverb and Princeton Reverb in the Twin Reverb?  I assume much of it comes from the use of tube rectifiers on the smaller amps.

I don't think the rectifier has as much to do with it as you think. I think the natural compression you are talking about is a result of the tubes being pushed, the trannies being pushed, the speaker being pushed...you get it. And what's more, I think it's a combined effect of all these things (rectifier included) that does it, not any one item. So, I think the answer is that without the use of outboard gear, "No, you can't get that compression from a Twin at low volume."

[Willabe]

A number of guys here have built a 1 channel AB763 Deluxe with no verb and trem, with a 12" speaker. And they love it.

There's at least 1 schemo/layout in the schematic section. Probable drawn by tubenit or geezer?

But, if your wife is to be a big factor in what you build for the house, (which is a good thing  ) I'd build a Champ with a 10" or 12" and be done with it.

Doug has everything you'll need in his store to build either amp, except the cab and speaker.


                              Brad      

[Willabe]

I'm looking for a silver bullet here. The twin on 3 or 4 is too loud for wifey. Even at that low level which is comfortable for my ears.

Yeah you are, an 80w amp with 2- 12" speakers is still very loud.        

I could give up the tremolo (since I have the twin for that) and use that tube for the Deluxe PI, right?  That would leave me with half a tube leftover, wouldn't it?

No, the LTP PI uses both half's of a 12A_7.

Back in the day guys in the studio used variacs.  At some point folks said it was bad for the amps.

You can only use a variac to drop the voltage so far. The problem is your dropping the heaters voltage at the same time as the B+.

Would dropping the voltage to the power tubes OR the rectifier lower the output power and increase the compression at a given volume?

Yes you could put in Power Scaling or a VVR but if it were me to get all the way down to the volume that will work for your wifes ears, I have no idea what size your house is but, I'd go with a Champ or the AB763.

The Twin has a steel chassis so you'ld have to also install a heat sink or 2 and drill a hole or 2 in the chassis. It would be best, if your going to try and drop that much voltage/volume to install a MV, 2'nd hole. I'd leave the Twin alone as I seem to remember seeing pics of it and it was in very good shape?


                     Brad        

  

[sluckey]

You may be interested in this...

http://home.comcast.net/~seluckey/amps/misc/AB763_Deluxe_Lite.pdf

It's probably still too loud though.

[jeff]

 If you're looking for cranked sound at lower volumes I'd check out some SE amps at a music store and see what you think. 5Ws is louder than it sounds. I always thought "5W that's nothing" but I built a nice 6V6 SE that sounds great at moderate(wife friendly?) volume levels. Not much clean headroom but if you're looking for something to push try one out and see if it's what you're looking for. Use your twin for quiet clean.

You could also build a SE 6L6 for a little more output/louder clean If a 6V6 isn't enough.

By the way what's GAS?

[Tyrannocaster]

GAS = Gear Acquisition Syndrome

I forgot to mention one other option you have - an attenuator, ie, Powerbrake, etc. They aren't cheap, but they are certainly cheaper than any amp build is going to be. At least then you can get the amp's natural compression, although not that of the speakers.

[proaudioguy]

The Twin is indeed really cool and loud as *)#%)*.

Last night while trying to go to sleep I found a silverface vibrochamp.  I'm told it needs lots of love. I believe it's an AA1164 iirc.  If it only needs a speaker (current one has a hole in it), then I'll likely not do much to it, but if it needs a lot more work, I might as well make it mine.  Even the face plate is pretty messed up.  I am thinking a Jensen 12" (Have to find the least efficient one) if I can cram it in there, or perhaps a little deeper cabinet but the same basic form factor or at least a decent 10", although I have not been too satisfied with the bass response of the 10"s.  I'd also like to add verb if I end up modding it heavily.  As for the tone, I am def into the BF clean and dirty sounds.  The Black Face Deluxe Reverb with old tubes is the standard.  Wondering how the little Champ compares tone wise.  I'll be interested in what you all have to say.  I think the key here is a very inefficient speaker.  I really like the sound of the old Jensens from the Twin and Super, but the Super has plenty of bass due to having 4 of them and the twin has 2 12"s.  My Concert has an Eminence 12" and it has good low end.  My Super Champ has a Pro Jr Eminence 10" and the bass farts out pretty bad.  It's very close to the tone on the clean side, but the verb is very dark (need to figure that out), and at 18 Watts, it's way too loud.  I think a hot plate of some kind on the Champ would get the so called "bedroom levels", but I have to have the tone.

[tubeswell]

Princeton reverb

[HotBluePlates]

Is there any way to get the compression of the Deluxe Reverb and Princeton Reverb in the Twin Reverb?  I assume much of it comes from the use of tube rectifiers on the smaller amps.

I never thought of the Princeton Reverb or Deluxe Reverb as "compressed" amps. And I'm thinking you want to find a way to use your existing Twin Reverb while being quieter. But how do you make a V-8 sip as little gas as a Prius? The big output stage of the Twin limits you realistically getting "quieter".

Different idea you may like:

Once upon a time, I was trying to cop the SRV sound. I couldn't afford to go buy the sea of amps described for his recording sessions, but I did have a Princeton Reverb and an octal-based 5B2 Princeton. I ran through an A/B/Y pedal to drive both amps at once, using the tweed for its distorted/compressed sound when cranked to 11, and the Princeton Reverb for mid-scooped clean with reverb.

Even a tweed Champ/Princeton is loud enough to annoy your family if it's cranked up. And if you think about typical guitar speaker being anything from 90-105dB with 1w of input, this makes sense. So... what about the PRR 1/3w amp? It's a pair of 6AU6's with a reverb transformer as the OT. Plug your Twin's speakers into the speaker jack and forget about mismatched impedances. Should get you low enough volume while allowing you to distort the snot out of the "output" tube.

[SoundmasterG]

The smaller Fenders overdrive quicker partly because they are lower power of course, but also partly because their preamp and phase inverter use lower voltages. You could modify the values of the dropping resistors in the Twin so that your preamp and phase inverter voltages more closely match what is found in the smaller amps, and then you will lose headroom and get a bit more breakup and a warmer sound. It will still be louder than shit though! Another thing you can do is put in a negative feedback disconnect switch. You just disconnect the ground switch and throw away the death cap if it is still connected, and use the switch to disconnect the negative feedback. this will make for a more raw and overdriven, and louder sound, but it will overdrive a bit sooner in the volume range. When you combine that with the changes to the preamp voltages, that may get you where you want to be.

Greg

[proaudioguy]

The smaller Fenders overdrive quicker partly because they are lower power of course, but also partly because their preamp and phase inverter use lower voltages. You could modify the values of the dropping resistors in the Twin so that your preamp and phase inverter voltages more closely match what is found in the smaller amps, and then you will lose headroom and get a bit more breakup and a warmer sound.
Greg

The is the very definition of power compression and current limiting.  This happens to our 6000 Watt amps if the mains voltage is to low (there is protection built in for that reason).  The mains voltage will drop just by using too long, too small gauge power cable.  Speakers themselves also exhibit a form of power compression.  As they get HOT they draw less from the amp.  They do reach a point of equilibrium, but there is a point where more power will just simply not get any louder (even if the speaker can survive it).  I was thinking the lower voltages combined with the use of a tube rectifier that could not supply large current causing the voltage to drop more as more power is needed, was what caused the compressed sound, and eventually the clipping in the tube, without getting into the heat capabilities of the tube.  IN a high power solid state amp with massive heat sinks and massive fans, the output device will never fail before the power supply will give up giving.  The clipping will destroy the PA before the output transistors have a chance to fail and open circuits don't harm solid state amps.  So I was just carrying this idea over to the Twin thinking maybe I could get the sound of 6-10 at 3-4.  That combined with a power soak and pulling 2 tubes and driving an 8 ohm single speaker, could get it there.  Anyway the GAS is winning.  I'm going to get that VibroChamp and see what I can do with it.  If it's in better shape than I think, then I won't deface it further.  I'll just fix it.

Also working on my Super Champ in another thread.  The clean is getting VERY close to the twin.  Oddly most of the work is just clean up.  I haven't changed any component values.

[HotBluePlates]

The is the very definition of power compression and current limiting.  ...

But you're a Pro Audio Guy, right?

Compression makes the average volume higher. The rest of what you're asking speaks to having too much volume. Smaller seems the way to go.

It's hard to get smaller than a 6AU6 "output" tube running on 170vdc.

[sluckey]

Let's see, you want your SC to sound more like a TR and your TR to sound more like a SC? Maybe you're just plugged into the wrong amp at a given time? 

Seriously, I know you're chasing a problem in the SC, but it just struck me as a little bit funny when you mentioned both amps in the same thread.

[proaudioguy]

The is the very definition of power compression and current limiting.  ...

But you're a Pro Audio Guy, right?

Compression makes the average volume higher. The rest of what you're asking speaks to having too much volume.

This is actually wrong. Compression reduces the loud part and does nothing to the soft part. Compression in an amp is nothing more than a very soft clip with round edges. A compressor effect (the real ones not a guitar pedal) uses a voltage controlled amplifier (VCA) to very quickly turn down the level of any signal surpassing a threshold.  As the signal is reduced the VCA allows the gain to come back to unity. Real compressors have attack time, the time it takes to engage the gain reduction, release time, the time it takes to allows th gr to go back to unity once the signal is no longer above the threshold, ratio which can be set in a continuously variable way from 1:1 (unity gain) to infinity :1. A 4:1 ratio means if a signal going in it 1dB over the threshold, the signal coming out will be 1/4 dB above the threshold because the VCA will turn it down 3/4 dB. The VCA can be very fast or very slow based on the attack and release times. Boutique and high end tube compressors sometimes have a variable ratio that increases depending on the signal coming in (soft knee). This can sound extremely good.  You kill the dynamics without any artifacts. dbx in the 1970s introduced what they call overeasy which is actually a very very soft knee. The knee is Hard if you go from a 1:1 ratio to a 4:1 ratio the instant you cross he threshold. A soft knee gradually changes the ratio from 1:1 to 4:1 as the signal approaches the threshold. It's far more forgiving.

At the output of a professional compressor there is a gain control. Since you have reduced your signal in the compressor you need to bring it back up before going to the next stage. By doin this you are amplifying the signal. Slow the threshold and the signal above the threshold is close to the level of you original peaks. This may SOUND like you are increasing the level. Guitar pedals confuse the issue in that they usually have only 2 controls on the outside and the rest are preset on the inside. The sustain control is just a relbelled threshold control. Reducing threshold increases apparent sustain. I have a dynacomp. It sounds nothing like what I am after. If I had a drawmer 1969 or a summit DCL or a blackface deluxe reverb I could get there easily.

As for Steve's comment. I started tweaking the SC to try and get this sound after I started this thread.  Being 18watts it's still way too loud.  The clean was really close but during my testin yesterday I broke my V1 tube and now I'm chasing that dragon again.  Really need to get some NOS RCAs.  I have tried 10-12 different tubes in that position.  One particular 1990s sovtech with the writing missing sounded good and the rest sound blah. Several sound quite harsh especially when playing the G string. Thinking about putting he snubers back,.. But that's for another thread isn't it.

Let's face it what I really want is that 1967 DR I played at sam ash 48th st a few months back, and for my family to tolerate me cranking it up.

[HotBluePlates]

... Compression reduces the loud part and does nothing to the soft part. ... At the output of a professional compressor there is a gain control. Since you have reduced your signal in the compressor you need to bring it back up before going to the next stage. ...

But the compressor (or limiter) reduces the number of dB from "softest" to "loudest". So the average is bigger than it would be before compression (or after expansion). But I know what you mean; technically, the peaks have been reduced. I submit that people compress to either increase the actual average loudness, or to give the impression of loudness, by raising the volume of the quiet parts of a sound (like snare rattle after the initial whack).

Radio stations squash the hell out of the music the broadcast so they can be the loudest station (the one everyone can pick up) without overmodulating the transmitter and being fined by the FCC.

What I'm really trying to say is it's not about compression. It's about output stage distortion. You want to be able to crank up to get "the sound". So either your family needs to change their view on what is "too loud" or you need a smaller output stage.

Having owned Champs and Princetons (reverb and non-, tweed and blackface) as well as bigger amps, I can tell you that even a Champ might be too loud for some family.

Save your time. Don't try to figure out how to get more compression (that's easy to do, right now, for cheap), get a smaller output stage.

[proaudioguy]

The signal only LOUDER on average because you then turn it up AFTER it's been compressed.  The radio station "makes up the gain loss" after the compression takes place.  This usually happens inside the compressor.  They use multiband compression that squashes different frequency bands different amounts.  The state of the art in radio station "mastering" is digitally controlled and the makeup gain happens automatically.  I'm looking more for what a dbx 160, or a Drawmer 1969, or Summit DCL does.  These are devices I strap on the insert when I'm mixing YOU GUYS.  Of course much of it is done in the digital domain inside the mixing console now.

In the case of the Twin you reach compression at a much LOUDER amp level because the drive to the power section is quite high by the time it compresses and the power tubes put out a lot of power before they compress.  On a small amp "the end" is reached while the amp is quieter.  The output tubes have less power, there are less of them and the power supply may be under built causing them to clip sooner.

We are in complete agreement.  So what do I do, build an AB763 preamp with one of these "regular tubes" driving a reverb transformer (as suggested above I think)?  Will this SOUND the same only quieter?

I think the only way I'm going to get the twin under control is a power soak.  Anyone got any schematics?  I found a nice one for sale for about $800. online.  I can't imagine it's more than just a bunch of power resisters in series/ parallel.  Am I right?