Page 3 of 3
AcousticMirror
loves cheesecake
Join date: Dec 2009
4,843 IQ
#81
Quote by Kanthras
This thread is epic. Makes me feel much better about myself, thanks guys.
We're talking output transformerless, that schematic doesn't have an OT. On the schematic, find the output tubes, trace the wire out of the plate through the coupling cap towards the resistor called "load". That's representing the speaker.


hey you don't get off that easy. you were this stupid once too. don't make me use the search boy.
buffalo buffalo buffalo buffalo buffalo buffalo buffalo.
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#82
Maybe the items with the T reference designator. Stop being rude, thanks.
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#83
I was saying that I saw magnetics all over the place on the "Transformerless" Patent, the schematic you posted does not confuse me AcousticMirror.
AcousticMirror
loves cheesecake
Join date: Dec 2009
4,843 IQ
#84
wait. what was the original point of this thread again...

are tube amps supposed to be warm?
buffalo buffalo buffalo buffalo buffalo buffalo buffalo.
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#85
Also what's the point of that "Output Transformerless" design if you have to use transformers for the DC/DC power conversion? Sure the output stage doesn't have a transformer but you still have to use a transformer.
Roc8995
Moderator
Join date: Nov 2005
2,050 IQ
#86
Yes, there are transformers. Again, it has to have some sort of matching device, but the deployment is novel enough to be called transformerless. It's like a wireless phone - it's got wires, but for all practical purposes, you can call it that. Let's not drag the PT into this - I really don't think you can lump it in with the OT as far as tone changes go.


My purpose in posting that was to show that there are approaches that do away with traditional transformer design, and the tone changes that might come with them. Can we not agree on that?

There are a lot of reasons not to use an OT. They're the most expensive part of the amp, they're overly sensitive to cabs, they're heavy, and they're not hugely reliable.
AcousticMirror
loves cheesecake
Join date: Dec 2009
4,843 IQ
#87
i dunno. buy one and test it out?
buffalo buffalo buffalo buffalo buffalo buffalo buffalo.
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#88

My purpose in posting that was to show that there are approaches that do away with traditional transformer design, and the tone changes that might come with them. Can we not agree on that?


It is interesting indeed, I'll agree on that.

My whole point of this thread was that an amplifier is more of an impedance matching device rather than amplifying the signal by a lot.

Assuming you guys are right, what I understand is that the harmonic distortion content of a tube amplifier is what gives the "warm" sound. I was suggesting that the "warm" sound was coming from the output transformer because the amplifier isn't gaining the signal by a huge amount.
Roc8995
Moderator
Join date: Nov 2005
2,050 IQ
#89
I think it is multiplying it by a lot. The input power is very low, maybe a tenth of a watt. Output power is 50 to 100W - that seems like quite a bit to me, at least in this application. If your background is in SS devices then that probably doesn't sound like a large gain factor.

The reason the tubes color the sound so much is that they're such low-fi devices, and they're being run very close to (or often, beyond) their maximum specs. The OT isn't as low-fi and isn't being stressed as much, so it contributes less. It does add something, though. If you ever have the chance, listen to an amp before and after an OT change. A 100W OT in a 50W amp adds a bunch of girth and low end, and an undersized OT adds a fair bit of compression and even a bit of distortion.
Kanthras
Boogerman
Join date: Aug 2007
905 IQ
#90
Yeah, you can't really deduce what's happening inside a guitar amp by measuring the input voltage and output voltage and comparing that.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#91
I think it is gaining it by a lot. The input power is very low, maybe a tenth of a watt. Output power is 50 to 100, that seems like quite a bit to me, at least in this application. If your background is in SS devices then that probably doesn't sound like a large gain factor.


I think you're getting a little confused here because the input power doesn't matter, it's all about the input voltage. You just need to put an op amp at the front end of the guitar amplifier (high input impedance, low output impedance), so that 5V will be able to drive any circuitry inside the amplifier after the buffer stage.

If you're comparing input power to output power, that's just impedance matching. I'm more familiar with FETs, but I assume tubes are voltage controlled amplifiers.
Cathbard
Grumpy Old Tech
Join date: Oct 2009
2,565 IQ
#92
Instead of using a normal oscilloscope and just measuring the output voltage, try hooking up a spectrum analyser to it. Then you might get a better idea of what's going on. A guitar amp that amplifies cleanly will sound like smeg. Try plugging your guitar into a high end hi fi amp - sounds dreadful doesn't it? Even an MG sounds better.
Here's an exercise for you. Compare a valve preamp to a SS preamp. There is no OT in a preamp, they are just capacitively coupled. There is a huge difference in sound still.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Roc8995
Moderator
Join date: Nov 2005
2,050 IQ
#93
Quote by farmosh203
I'm more familiar with FETs, but I assume tubes are voltage controlled amplifiers.


Ah, that's where our difficulties lie. The power tubes increase the current when the input voltage changes. They run at a constant voltage.
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#94
Instead of using a normal oscilloscope and just measuring the output voltage, try hooking up a spectrum analyser to it. Then you might get a better idea of what's going on. A guitar amp that amplifies cleanly will sound like smeg. Try plugging your guitar into a high end hi fi amp - sounds dreadful doesn't it? Even an MG sounds better.
Here's an exercise for you. Compare a valve preamp to a SS preamp. There is no OT in a preamp, they are just capacitively coupled. There is a huge difference in sound still.


Don't have a spectrum analyzer handy but it would be interesting to see what's really going on on different kinds of amplifiers.

I understand why you guys are saying the tube has the "warm" sound, because of how the signal acts when it distorts.
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#95
Ah, that's where our difficulties lie. The power tubes increase the current when the input voltage changes.


But aren't tubes voltage controlled voltage sources? The inside of a tube is an open air gap, right? So you aren't going to get much current (if at all?).

That's the whole reason you need the output transformer, because the tube can't drive enough current through the speaker.
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#96
Well I hope I didn't piss you guys off, but I'm going to bed, g'night .
Roc8995
Moderator
Join date: Nov 2005
2,050 IQ
#97
The input voltage controls the current from cathode to plate. There's a significant amount of current.
Cathbard
Grumpy Old Tech
Join date: Oct 2009
2,565 IQ
#98
Quote by farmosh203
But aren't tubes voltage controlled voltage sources? The inside of a tube is an open air gap, right? So you aren't going to get much current (if at all?).

That's the whole reason you need the output transformer, because the tube can't drive enough current through the speaker.

Actually with valves you are more interested in transconductance.

There is another important need for an OT apart from reflecting an 8K (or so) load to the valves - dc isolation. You feed the centre tap of the primary with about 400V. We don't want that sort of dc voltage on the speaker leads now do we? Apart from blowing up the speaker, 400V hurts. Trust me I know. Ouch!! We don't run +/- rails with a valve amp.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Nov 22, 2010,
311ZOSOVHJH
G G A - B A B Y
Join date: Mar 2008
7,171 IQ
#99
Quote by farmosh203
Well I hope I didn't piss you guys off, but I'm going to bed, g'night .




Good luck with whatever the stuff is you are working on.


PS: you triple posted within 3 minutes not too long ago. I'm not pissed, I'm just disappoint. oktnxbai
Kanthras
Boogerman
Join date: Aug 2007
905 IQ
#100
Quote by AcousticMirror
hey you don't get off that easy. you were this stupid once too. don't make me use the search boy.
I was not ever this stupid, you silly troll.
Perhaps a touch antagonistic, but hey, I learned to take the chill pill every now and then.

And I really hope you're not speaking of the whole "talkback debacle". I'm not getting into it, but I still think it's a stupid term.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
Cathbard
Grumpy Old Tech
Join date: Oct 2009
2,565 IQ
#101
Quote by Kanthras
I was not ever this stupid, you silly troll.
Perhaps a touch antagonistic, but hey, I learned to take the chill pill every now and then.

And I really hope you're not speaking of the whole "talkback debacle". I'm not getting into it, but I still think it's a stupid term.

I really don't know what's so stupid about it. It's just a description of dynamics that describes a behaviour in relation to the player in a poetic way. You're not into poetry maybe? I think it paints a perfect picture of what is happening in artistic terms which is better than trying to describe it in a clynical fashion. Why not use an artistic description for an artistic phenomenon?
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
Last edited by Cathbard at Nov 22, 2010,
CECamps
Schematic Junkie
Join date: Feb 2010
1,253 IQ
#102
Quote by farmosh203
The supply voltage of the active electronics doesn't matter unless the signal is coming close to the positive rail of the power supply. The only reason to increase the voltage supply of an amplifier would be to prevent the signal from clipping if it was coming close. The gain is set by the feedback resistors, not the voltage supply.


My mistake, I intended to say increase the headroom.

But this begs the question of why you were wondering about the purpose of the 18v mod if you understood it in the first place.
Wesbanez
Registered Abuser
Join date: Aug 2007
1,380 IQ
#103
I had to call in sick at work today from the headache this thread gave me, reading it as I did over my morning coffee.
[thread="1575882"]Exotic Telecaster Build[/thread]

[thread="1363496"]2x12 Custom Build[/thread]


[thread="1339413"]The Official Egnater Thread V2[/THREAD]

[thread="1356444"]Seven String & ERG Legion[/THREAD]
Kanthras
Boogerman
Join date: Aug 2007
905 IQ
#104
Quote by Cathbard
I really don't know what's so stupid about it. It's just a description of dynamics that describes a behaviour in relation to the player in a poetic way. You're not into poetry maybe? I think it paints a perfect picture of what is happening in artistic terms which is better than trying to describe it in a clynical fashion. Why not use an artistic description for an artistic phenomenon?
I guess I'm not too big on poetry. But when you put it that way, I can see how it's a good term to describe talkback. Perhaps it is appropriate that something subjective is described by a vague term.
Quote by Wesbanez
I had to call in sick at work today from the headache this thread gave me, reading it as I did over my morning coffee.
I can imagine.
Gear:
- Bugera 333
- VJ & VJ cab
- Jackson JS30
- TS9

Bugera Users Militia. We are horrible people. With a sprinkler fetish.
~ BUM: For all things extinguishing

Rackmount Tube Amp Project <<< Updates!
TNfootballfan62
Mr. Blue
Join date: May 2004
1,943 IQ
#105
Quote by farmosh203
My whole point of this thread was that an amplifier is more of an impedance matching device rather than amplifying the signal by a lot.


I disagree. There is impedance matching that goes on, obviously, but you can't say it's "more" for that when it does, indeed, amplify by so much.
Feel free to call me Kyle.

Quote by ibz_bucket
Just so you know, I read everything you type in a Mike Rowe from Dirty Jobs voice.

Quote by tubetime86
I mean in Kyle's case, it is in the best interest of mankind that he impregnate anything that looks at him funny...
FrustratedRocka
UG's Turntablist
Join date: May 2009
2,339 IQ
#106

This is this thread.
Quote by dr_shred
FrustratedRocka you are a legend

Quote by littlephil

The man clearly knows his shit.

Quote by Banjocal


one of the best, educated and logical posts I've ever seen on UG in the Pit. Well done good sir.
fly135
Cheap Gear Enthusiast
Join date: Jul 2007
831 IQ
#107
Quote by farmosh203
....So if you're driving an 8 ohm speaker at 30Vrms, your output power is 112.5Watts.

Assuming 100% efficiency in the power supply, your current coming from the wall would be 120*current = 112.5Watts, which would mean your input current is 112.5W/120V = 0.9375Amps.

What was the current at the output? Well 112.5W / 300V = 0.375Amps.

Can we all agree on this?
No. The output current is 30/8.
gregs1020
Hi mom!
Join date: Dec 2007
10,786 IQ
#108
i knew this was going to deliver.
Quote by Roc8995
I don't think I've ever played anything in black walnut. It's a great ice cream flavor, so I assume it works well for a strat too.

Quote by JustRooster
The slugs in the pickups for telecasters are from old winchester rifles, which is why they sound so country.
stratman_13
666lb bongsession
Join date: Jun 2007
2,002 IQ
#109
This thread is win. Even if it didn't set out to be.

Also: If that's the case, then I need a warmer output transformer.
--

How do you say "I'm okay" to an answering machine?

--
CL/\SH
🤖
Join date: Jul 2009
1,083 IQ
#110
Tube amps are not supposed to be warm... Wait...
Quote by SG_dave at #33549256
I've never wanted to see a guy eat dick so much in my life.
Quote by ali.guitarkid7 at #33553650
If you are white, you are scum.
CL/\SH
🤖
Join date: Jul 2009
1,083 IQ
#112
One of the most confusing albeit amazing threads ever
Quote by SG_dave at #33549256
I've never wanted to see a guy eat dick so much in my life.
Quote by ali.guitarkid7 at #33553650
If you are white, you are scum.
311ZOSOVHJH
G G A - B A B Y
Join date: Mar 2008
7,171 IQ
#113
Quote by Wesbanez
I had to call in sick at work today from the headache this thread gave me, reading it as I did over my morning coffee.



+1

But seriously, it's not how big your transformer is....it's how you ....wait...ok.... I'm not going to lie to you.
gumbilicious
beginner
Join date: Oct 2007
1,236 IQ
#114
Quote by farmosh203
The inside of a tube is an open air gap, right?


no, not free air. free space. a vacuum would be the optimal environment. but close to a vacuum

something simple like a diode would have an anode at one end and a cathode at the other (like your FETS). the cathode would consist of a piece of filament with a coating (called a emulsifier). the idea is to run a current through the fillament (thus heating it) until the emulsifier reaches a 'saturation' temperature and is induced into thermionic emmision.

thermionic emmision is an excess 'cloud' of electrons being emitted from a material. without thermionic emission there wouldn't be enough electrons for sufficient operation.

the anode would then be a relatively positively charged plate that will attract the excess electrons surrounding the cathode. with a simple anode/cathode vacuum tube you can implement a diode. you can rectify AC current with those.

but suppose you wanna great tricky. apply a large direct current to the cathode filament to induce a flow of electrons to the anode plate, but place a 'screen' or 'grid' between the anode and cathode and apply an A/C signal to the 'grid' and you can attract some of the current going from cathode to anode (and thus effective control current flow). that is a basic description of a simple triode (equivalent to your transistors and FETs in ways).

larger vacuum tubes (tetrodes and pentodes) just use optimal distances, more heat resistant materials and extra screens/grids to focus the electron beams.

Quote by farmosh203
So you aren't going to get much current (if at all?).


thermionic emission is the key. but tubes are horribly inefficient anyway. the plate voltage are enormous vs. FET's/opamps/transistors.

Quote by farmosh203
That's the whole reason you need the output transformer, because the tube can't drive enough current through the speaker.


i thought you needed a transformer because a tube's output impedance was so high that it needed to be 'stepped down' to drive low impedance devices like speakers.

i heard FET's and transistors output impedances were so low you can just run an appropriately large load instead of an output transformer.

this may correlate to what you say, but i am not good enough at electronics to tell.
punk isn't dead, it's always smelled that way.

"A perfection of means, and confusion of aims, seems to be our main problem."
-ae
Last edited by gumbilicious at Nov 22, 2010,
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#115
No. The output current is 30/8.


Woops, haha... now why would I use the +rail to find output current? My bad.

i thought you needed a transformer because a tube's output impedance was so high that it needed to be 'stepped down' to drive low impedance devices like speakers.


Yup that's correct, but that's the same thing as saying that the tube can't drive enough current through the speaker. It's just a voltage divider where you have Vout = Vin*[Rspeaker]/(Rspeaker+Rsource). A high Rsource means your voltage at the output is low, so you have low current.
gumbilicious
beginner
Join date: Oct 2007
1,236 IQ
#116
Quote by farmosh203
Woops, haha... now why would I use the +rail to find output current? My bad.


Yup that's correct, but that's the same thing as saying that the tube can't drive enough current through the speaker. It's just a voltage divider where you have Vout = Vin*[Rspeaker]/(Rspeaker+Rsource). A high Rsource means your voltage at the output is low, so you have low current.


well if that is the case, then the reason for such a high Rsource would be the extreme conditions that are a vacuum tubes operational environment. there was no secret they were highly inefficient. they were almost better at radiating heat than they were at amplifying.

speakers are also inefficient, but we still use em anyway.
punk isn't dead, it's always smelled that way.

"A perfection of means, and confusion of aims, seems to be our main problem."
-ae
farmosh203
Registered User
Join date: Aug 2010
594 IQ
#117
Woops, instead of "Rsource", I should have used the variable "Rout", don't grill me! Ok, I'm done with this thread
MilbertCom
Registered User
Join date: Jul 2009
10 IQ
#119
and regarding this

"I just measured the output of my pedal (the stage going into my amplifier) and it's definitely above 4V peak to peak. Sort of having trouble plucking the note, then quickly grabbing the probes on my oscilloscope to measure the signal though." from page 1 of this thread

there's this

Tubes vs Transistors
http://milbert.com/Files/articles/TvsT/tstxt.pdf