Full Range Amplification - A Revelation

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frugal-phile™
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In reality, a tube amp reacts differently to a real speaker load than a solid state amp. It behaves more like a current source than a voltage source at some frequencies.

Maybe as a generality, but there certainly are tube amps that are voltage sources, and solid state amps that are current sources. Most tube amps, even the ones that have quite high output impedance still fall on the voltage source side of the dividing line. Remove the feedback loop on a pentode amp and it does become a current source.

What hasn't been said yet, is that (until recently) the triode is the most linear voltage amplification device made by man.

dave
 
Maybe as a generality, but there certainly are tube amps that are voltage sources, and solid state amps that are current sources. Most tube amps, even the ones that have quite high output impedance still fall on the voltage source side of the dividing line. Remove the feedback loop on a pentode amp and it does become a current source.

You are absolutely correct. In fact my ultralinear probably acted more like a voltage amp than a current amp, since I used about 30 dB loop gain (a lot for a tube amp!) and tweaked the phase with feedforward compensation until it was stable. Nevertheless, it was distinctly more "tubey" than solid state amps and distinctly less "tubey" than any tube amp I ever heard until the mid 90s. It was quite unique for its time (not a reinvention of the wheel by any means but at the time nobody cared about tubes at all except for nerdy me :D ) and would certainly be considered a fancy boutique amplifier by todays standards.

It had full frequency response (power bandwith of 20 kHz @ 20 watts RMS very good for a tube amp of 37 watts RMS) , it was very dynamic, it made every single speaker that I hooked up to it sound better, it had 4/8/16 ohm outputs, it had 3 dB of voltage headroom, it had very soft clipping with no nasty artefacts at all, it was all that and a bag of chips.

What hasn't been said yet, is that (until recently) the triode is the most linear voltage amplification device made by man.

dave

Again this is true, but the benefits of an ultralinear pentode push pull amp can't be denied. With thoughtfully applied feedback, it becomes virtually a moot point.
 
Synergy

In the last 10 years I’ve built many amps and speakers, many valve amps, both SE and PP, and a few SS, mainly Firstwatt. I’ve found some speakers sound better with valve amps and some prefer SS. Some prefer valves with feedback while others prefer valves without.

I’ve measured stuff until the cows come home but I’m still none the wiser, in fact I’m probably more clueless than when I started.

What I have convinced myself that I’ve found is that a loosely damped cabinet/driver combination will sound very wooly in the bass area if coupled with an amp that has high output impedance(low damping factor).

In the diy area I will always recommend trying to listen to the target combination, either borrowing kit or visiting somebody with the same set up. Building on somebody elses recommendation can present risks. It’s the match between amp and speakers that is the deal breaker, not whether it’s valves or SS.

Synergy matters!

and then when you've got the synergy nailed, there is still the environment to think about.....personally I think the SS vs valves argument is well overplayed.

just my two penneth

Ed
 
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Synergy

In the last 10 years I’ve built many amps and speakers, many valve amps, both SE and PP, and a few SS, mainly Firstwatt. I’ve found some speakers sound better with valve amps and some prefer SS. Some prefer valves with feedback while others prefer valves without.

I’ve measured stuff until the cows come home but I’m still none the wiser, in fact I’m probably more clueless than when I started.

What I have convinced myself that I’ve found is that a loosely damped cabinet/driver combination will sound very wooly in the bass area if coupled with an amp that has high output impedance(low damping factor).

In the diy area I will always recommend trying to listen to the target combination, either borrowing kit or visiting somebody with the same set up. Building on somebody elses recommendation can present risks. It’s the match between amp and speakers that is the deal breaker, not whether it’s valves or SS.

Synergy matters!

and then when you've got the synergy nailed, there is still the environment to think about.....personally I think the SS vs valves argument is well overplayed.

just my two penneth

Ed

I believe you are correct, sir.

When I was pondering tube amps, I listened. Not to the amps, as I had no opportunity to. I listened to the folks around here. One person in particular (chrisb) has the exact same speakers as I do and he seems to love them as much as I do, so when he said (in a thread that I cannot recall now) that the amp which worked best with his speakers is a P-P tube amp, I figured that was something I needed to pay attention to.

So, synergy isn't always an accident. It can be copied. :)
 
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Those "spirit" generic capacitors are prime candidates for modding. :D

Thanks for the tip.

From what I understand, some capacitors matter more than others, depending where they are in the circuit. It seems "coupling caps" and "output caps" (same thing?) are discussed a lot.

Is there any way for an educated person to look at the bottom of this amp and say which caps are doing what?
 
Thanks for the tip.

From what I understand, some capacitors matter more than others, depending where they are in the circuit. It seems "coupling caps" and "output caps" (same thing?) are discussed a lot.

Is there any way for an educated person to look at the bottom of this amp and say what caps are doing what?

Those yellow capacitors couple the driver tube to the output tube. They have to handle hundreds of volts swing rapidly back and forth, so their quality is critical. In a push-pull stereo amp, you have 4 channels, so 4 capacitors. They should be in the range of 0.22uF.

The other capacitors are not as critical. I'm not sure what the white ones are doing.

You can try SS rectification, and roll some tubes, depends on your mood.
 
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Those yellow capacitors couple the driver tube to the output tube. They have to handle hundreds of volts swing rapidly back and forth, so their quality is critical. In a push-pull stereo amp, you have 4 channels, so 4 capacitors. They should be in the range of 0.22uF.

The other capacitors are not as critical. I'm not sure what the white ones are doing.

You can try SS rectification, and roll some tubes, depends on your mood.

Thanks very much for the info. I love learning about this stuff!

If I ever get the courage to replace those caps, which caps would you recommend I use? Auricaps? Solen? Also, I am not a skilled solderer, so I am not so comfortable removing the capacitor leads from the board. Would it be practical to snip the existing caps off, leaving the leads in place, and then solder the new capacitors' leads to the old leads? Silly, I know, but would it be a disaster?

WRT tube rolling; I have already ordered a matched quad of EH EL34 and a matched pair each of NOS-tested Sylvania 12AX7 and NOS RCA 12AU7. I will wait till I have about 150 hours on the amp before doing any rolling.
 
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Yeah, you can leave the old leads in. I would recommend Mundorf Silver/Oil, with the standard Supremes a cheaper alternative.

You can try GE 5751's in place of 12AX7 and 12BH7 in place of 12AU7. Psvane makes Black Treasure series of EL34.

Great! Thanks again.

Re: Psvane tubes; I am very hesitant. The price is very, very high, and while I am very impressed with this amp, GF does also sell some products which I would put into the category of "snake oil" ($100 power cords, $500 interconnects, etc.).

Maybe the Psvane tubes are amazing, but I am not sure I will hear $300 worth of difference. Recall what I paid for the amp! :)
 
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