Tonefiend Forum

Welcome Guest 

Show/Hide Header

Welcome Guest, posting in this forum requires registration.





Pages: [1] 2
Author Topic: Preamp vs. Power amp
Schrodinge-
rsgoldfish

Posts: 105
Permalink
Post Preamp vs. Power amp
on: September 12, 2012, 21:53
Quote

So, I have a new to me tube amp. I've been reading about tube amplifiers and how their various distortion work; in doing so, I learned about the difference between preamp and power amp distortion. I am curious now about my amp, but there is a problem: my amp has a single volume knob. How does this affect the balance of preamp and power amp distortion in my little combo?

Double D

Posts: 195
Permalink
Post Re: Preamp vs. Power amp
on: September 12, 2012, 22:09
Quote

Hammering your preamp with a boost pedal with the amp's volume knob set on the low side will give you an idea of what preamp distortion sounds like, whilst running it wide open will give you the power amp's grind. Your preamp volume is preset at a fairly nominal level, so you'll need outside help to get it clipping. You'll probably find the "pre-amp only" distortion to be more splattery and less dynamic than running the whole amp hot.

Schrodinge-
rsgoldfish

Posts: 105
Permalink
Post Re: Preamp vs. Power amp
on: September 13, 2012, 06:10
Quote

Awesome. I was hoping that exactly what you said was the case. Most people agree that they like their power amp distortion the best, but it's good to know that I still have control over my amounts of gain in each stage, using a boost to hit my preamp.

mwseniff

Posts: 149
Permalink
Post Re: Preamp vs. Power amp
on: September 13, 2012, 07:49
Quote

There are many reasons why pwr amp distortion is desirable. By the time the pwr amp distorts the pwr supply is also sagging which gives a nice musical compression to the sound (assuming standard guitar amp design). Also the pwr amp usually has negative feedback derived from the output transformer secondary this causes the amp to have an additional effect in that the neg feedback because the amp is now a non-linear device. Beyond this the spkr in most cases is also being overdriven causing even more non-linearity in the negative feedback loop. In the case of an alnico spkr the alnico magnets field is often bent temporarily causing more compression (alnico magnets have a hysterisis loop that is less tight than other most other magnets). In other words the power amp has many more interactive elements than a preamp which is a much simpler circuit. This complexity is why it is so difficult to model completely.

Double D

Posts: 195
Permalink
Post Re: Preamp vs. Power amp
on: September 13, 2012, 11:19
Quote

I thought it might be interesting if some of the solder soldiers in our midst took a look at Shrodingersgoldfish's Gibsonette amp schematic and helped us non-handy types get a little insight into what's going on in there. It seems like a pretty simple circuit, so it might make a good tube amp primer. Here's a link:https://www.0rigami.com/gg/gibsonette_schematic.jpg

mwseniff

Posts: 149
Permalink
Post Re: Preamp vs. Power amp
on: September 13, 2012, 13:44
Quote

It is interesting in that it is actually a single ended amp like a Fender Champ but has 2 6V6 output tubes in parallel rather than 1 6V6 like the Champ. Beyond that it is pretty standard fare.

Schrodinge-
rsgoldfish

Posts: 105
Permalink
Post Re: Preamp vs. Power amp
on: October 2, 2012, 07:22
Quote

I currently find myself without a proper ohmmeter. So I was wondering if it's possible to learn the impedance of the speaker for this amp from the schematic?

Oinkus

Posts: 236
Permalink
Post Re: Preamp vs. Power amp
on: October 2, 2012, 16:17
Quote

IDK I have a Fender Prosonic and I will take the preamp distorion in it over pretty much anything ever made.That and the fact it doesn't require ear bleeding volume to achieve.

Schrodinge-
rsgoldfish

Posts: 105
Permalink
Post Re: Preamp vs. Power amp
on: October 2, 2012, 19:29
Quote

Well, this amp only pushes 10 watts, so getting good power tube distortion doesn't require ear-splitting volume to achieve, which is why this amp has won me over on tiny amps from the start. Who gets to play gigs big enough to open their 30+ watt monster anywhere near toasting? Not me, that's for sure. It's a matter of favorites to me. I like the preamp, but I love the power amp. Just seems so much warmer and more dynamic. It just has this muscle-y tone that is fantastic. The preamp distortion is a little grainier, and much less responsive to my touch on the guitar. I still like it, but the power section wins for me.

Oinkus

Posts: 236
Permalink
Post Re: Preamp vs. Power amp
on: October 3, 2012, 03:40
Quote

Once you hit about 5 or 6 my amp starts to open up and generally the tubes are getting hot and bothered , but watts doesn't really mean volume.The only thing that matters is what YOU hear and like really .

Pages: [1] 2
Mingle Forum by cartpauj
Version: 1.0.34 ; Page loaded in: 0.038 seconds.

Comments are closed.