I'm tired of anemic guitar amps!

[toobfreak]

I'm an electronics engineer, if I wanted to build one I would.

Sure you are. If that were true, you wouldn't need a schematic from another.

I asked if he was sure that electrolytic was wired the right way around, no response, but he'll know soon enough I guess.

Sure way to test whether an electrolytic is wired right is to plug it in and see what happens.

The irrational devotion to "tube sound" should have died off by now, its akin to those who obsess over speaker wire, seeking oxygen free silver conductors and other superstitious nonsense.

Actually no. If you were any kind of actual electronic engineer, you'd know full well the reason why tubes are preferred by music professionals and serious audiophiles the world over. But as to the $5,000 speaker wires with magic construction built out of oxygen-free copper, that is another thing.

 

[Chuz Life]

Are you certain this is connected the right way around?

View attachment 1158166

That might depend on what the circuit is for. It looks like the positive voltage is expected to be on the cathode of the diode, which would most likely put it into reverse bias. So, unless we know if it is being used as a half wave rectifier, reverse bias protection, etc. . . (and that would be my first guess.) We just don't know.

And in those cases I stated, the capacitor is in correctly.

 

[Sherlock Holmes]

Sure you are. If that were true, you wouldn't need a schematic from another.

Why must you imply I'm being dishonest? I have had stuff published, studied the subject full time, have certification.

Without a schematic I can't see the design of the amp, schematics are common in electronics, odd you've never heard of them.

Sure way to test whether an electrolytic is wired right is to plug it in and see what happens.

Yes, one can also check the wiring against the schematic. But I never said it was wrong, I only asked if it was.

Actually no. If you were any kind of actual electronic engineer, you'd know full well the reason why tubes are preferred by music professionals and serious audiophiles the world over.

It's a fad, I very much doubt any listener even an engineer could listen to some music and reliably determine if the amplifier relies on tubes or semiconductors.

If they want a particular distortion profile then one should use a DSP and artificially incorporate customized distortion where one can select "tube" vs "transistor" and with various transfer function options, a universal audio amp just for audiophiles.

...tick tock...

Look. here's one:

https://line6.com/helix/

With some effort one could even allow the user to emulate specific tube types, perhaps all controlled from your iPhone !

But as to the $5,000 speaker wires with magic construction built out of oxygen-free copper, that is another thing.

Yes, it's silly.

Now tell me what sort of test equipment you have at home.

 

[scruffy]

That might depend on what the circuit is for. It looks like the positive voltage is expected to be on the cathode of the diode, which would most likely put it into reverse bias. So, unless we know if it is being used as a half wave rectifier, reverse bias protection, etc. . . (and that would be my first guess.) We just don't know.

And in those cases I stated, the capacitor is in correctly.

Someone's complaining?

Everything works, I'm tweaking the power chain as we speak. Bias at a lovely -103v, peachy. Putting in all the preamp tubes, everything but the KT-88's. Once the voltages are correct we can phase the PI and the reverb.

 

[Chuz Life]

Someone's complaining?

Everything works, I'm tweaking the power chain as we speak. Bias at a lovely -103v, peachy. Putting in all the preamp tubes, everything but the KT-88's. Once the voltages are correct we can phase the PI and the reverb.

No complaints from me.

I'm just a tech.

 

[scruffy]

Here's the front of the first stage, and the 3rd stage coupling caps (missing most of the caps because I have to wire up the switch behind it first). Also the largest cathode cap is missing, for some reason I forgot to include it in my parts list, so back for another round... And this pic is pre-cabletie, there's one more wire that has to go in that first grommet which is the reverb return.

 

[toobfreak]

I very much doubt any listener even an engineer could listen to some music and reliably determine if the amplifier relies on tubes or semiconductors.

Look, Sherlock, you are obviously way out of your league. A vacuum tube and a transistor are two totally different devices operating in opposite ways. I won't waste breathe getting more technical than that, but many people routinely hear the difference, and perhaps the best proof of that is the predominance of valve technology still preferred and used throughout the music industry and the audio high end.

In the 1970s, a company called Audio Research came out with the 'Analog Module,' a solid state circuit designed to emulate the characteristics of a tube---- and it utterly failed. It is a matter of the physics of the device and not just a matter of some clever circuitry which can switch the sound back and forth from one to the other.

One might emulate some qualities by boosting even harmonics and suppressing odd harmonics for a warmer less analytical sound, but that only touches upon superficial characteristics of what makes tubes sound better.

The only reason why transistors ever edged out tubes in home radios, TVs and stereo gear was a purely economic one of saving cost and weight, etc., ie, increased profits.

 

[scruffy]

Look, Sherlock, you are obviously way out of your league. A vacuum tube and a transistor are two totally different devices operating in opposite ways. I won't waste breathe getting more technical than that, but many people routinely hear the difference, and perhaps the best proof of that is the predominance of valve technology still preferred and used throughout the music industry and the audio high end.

In the 1970s, a company called Audio Research came out with the 'Analog Module,' a solid state circuit designed to emulate the characteristics of a tube---- and it utterly failed. It is a matter of the physics of the device and not just a matter of some clever circuitry which can switch the sound back and forth from one to the other.

One might emulate some qualities by boosting even harmonics and suppressing odd harmonics for a warmer less analytical sound, but that only touches upon superficial characteristics of what makes tubes sound better.

The only reason why transistors ever edged out tubes in home radios, TVs and stereo gear was a purely economic one of saving cost and weight, etc., ie, increased profits.

Those old Hickok tube testers are worth a small fortune on eBay now.

 

[Sherlock Holmes]

Look, Sherlock, you are obviously way out of your league. A vacuum tube and a transistor are two totally different devices operating in opposite ways.

But you know nothing about my education or publishing history, so how can you say I'm out of my league? That depends on which kind of transistor surely, why don't you even mention that? why are you implying "transistor" means a 1955 BJT?

I won't waste breathe getting more technical than that, but many people routinely hear the difference, and perhaps the best proof of that is the predominance of valve technology still preferred and used throughout the music industry and the audio high end.

Please get as technical as you want, what difference are they hearing?

In the 1970s, a company called Audio Research came out with the 'Analog Module,' a solid state circuit designed to emulate the characteristics of a tube---- and it utterly failed. It is a matter of the physics of the device and not just a matter of some clever circuitry which can switch the sound back and forth from one to the other.

Yes, it likely failed because people insisted it use tubes not because of how it sounded.

"Listen lads, this new FET amp sounds exactly the same as a good old tube amp, wadya think?"

"does it use any tubes?"

"Err, no it uses FETs".

"Oh ok that's why it sounds crap".

One might emulate some qualities by boosting even harmonics and suppressing odd harmonics for a warmer less analytical sound, but that only touches upon superficial characteristics of what makes tubes sound better.

Superficial? the odd/even harmonics issue is the very BASIS of the preference for tubes (not that anyone can hear the difference).

I can see things on a scope or a spectrum analyzer that are indeed different between tube/semi but to assume that a human being can detect those differences is not scientific it is ridiculous pseudo science like saying you can tell if the plumbing in a house is copper or plastic by tasting the water!

The only reason why transistors ever edged out tubes in home radios, TVs and stereo gear was a purely economic one of saving cost and weight, etc., ie, increased profits.

Yes I know but bipolar transistors which are current amplifiers are not what I'm talking about, I'm sure you know what a MOSET is, so why all the pretense that I'm referring to some old BJT devices?

There's zero credible peer reviewed evidence that randomly selected people can distinguish between valve and semi sound reproduction, if you have some then share it here.

 

[toobfreak]

Those old Hickok tube testers are worth a small fortune on eBay now.

Its been a while since I pulled it out, but looking at pictures, I think I must have been an EICO 625 - 667 type tester that looks similar to this:

Very easy to use, accurate, reliable, and does the kinds of tubes I generally run into and need tested. Either way, this puppy ain't going nowhere.

 

[toobfreak]

Those old Hickok tube testers are worth a small fortune on eBay now.

I have a lot of cool test equipment including an analog storage scope, a frequency counter that uses nixie tubes, and a clamp on current meter that measures current down to a few nanoamperes without actually interrupting the circuit, but the one Hickok unit I had was an old Hickok multitester / multimeter.

This is the best picture I can find on one. It is on the right and the blue thing in the middle is the lid that snaps on top to cover it.

If you look close, there is a slide switch that selects the function left to right just above where you plug in the test leads. It was kinda cool, I don't know where I got it, but the LCD display was bad, probably somebody dropped it, I think I finally threw it away.

 

[scruffy]

Preamp tubes! They all light up. Charting voltages now, to see exactly where each operating point is.

There's two 12au7's on the bottom, one is the PI the other is the driver.

Then the gap is where the reverb transformer sits, under the chassis. And of course the obligatory 12at7 reverb driver is right next to it.

Followed by 5 12ax7's, two of which are for the reverb. The power amp requires the proverbial 0 dbm input, 0.775 vrms into 600 ohms. The last of the ax's is a cathode follower for the reverb recovery, that doubles as a tone stack driver, its output impedance is almost exactly 600 ohms. Also 0 dbm is a convenience for external effects, it means you can drive the power amp to full output from any nominally rated device.

 

[toobfreak]

Preamp tubes! They all light up.

Now if only it were Christmas time, you could sit in the dark with your tubes glowing, looking at them as you sipped on some eggnog.

Charting voltages now, to see exactly where each operating point is.

Man, that sure is one long puppy.

Then the gap is where the reverb transformer sits, under the chassis.

Is that what that is for? I had just assumed it was a choke.

And of course the obligatory 12at7 reverb driver is right next to it.

Well, of course--- that's obligatory.

 

[scruffy]

Now if only it were Christmas time, you could sit in the dark with your tubes glowing, looking at them as you sipped on some eggnog.

Ah, but Halloween is almost here. I will play the amp for the children while I drink their blood. Bwahaha...

Man, that sure is one long puppy.


Is that what that is for? I had just assumed it was a choke.

Maybe one of the biggest selling points of ultralinear - no choke needed. The OT puts enough inductance on the screens.

Well, of course--- that's obligatory.

Turns out I have a bunch of Amperex 7025 tubes I neither need nor want - would you like them? They're old but haven't seen many hours in use. Kinda sorta NOS - more O than N.

 

[toobfreak]

Ah, but Halloween is almost here. I will play the amp for the children while I drink their blood. Bwahaha...

You could hook the amp up to a speaker in the yard then play low pipe organ dungeon music through it full of creepy sounds and creaking hinges as the kids trick or treated.

Turns out I have a bunch of Amperex 7025 tubes I neither need nor want - would you like them? They're old but haven't seen many hours in use. Kinda sorta NOS - more O than N.

Gee thanks! That is generous, but frankly, I don't think I need any of those, but you could probably sell them on eBay or somewhere maybe?

 

[hondo 50]

So why are there crappy amps? I'm guessing this is another thing that China has ruined. Don't tell me I can walk into Walmarx and see plastic amps on the shelves!

 

[toobfreak]

So why are there crappy amps?

A number of reasons:

1. Manufacturers addressing a price point more so than the quality of product. There are always buyers of cheap amps.
2. Bad engineers. Just getting your sheepskin from some mail-order college does not guarantee you know what the farg you are doing.
3. Bad hearing. You'd be surprised by the number of people with a tin ear who cannot hear for shit.

 

[Chuz Life]

toobfreak , I know you don't like AI but I had to use it to answer this question for myself, after reading some of your recent comments about Tube vs Transistor amps.

Please review my chat with GROK on this and see if you agree with both, my hunch and Grok's response.

https://x.com/i/grok/share/yg3ZR56pQBq99n0oIWTUlB7C1

ConclusionYour gut is correct: intermodulation distortion is generally more degrading in transistor-based amplifiers than in tube amplifiers, particularly in audio applications, due to the harsher clipping and higher-order distortion products in transistors. However, this difference is most pronounced in overdriven or poorly designed transistor amps. Well-designed solid-state amplifiers with proper biasing, feedback, and linear operation can minimize these effects, sometimes rivaling or surpassing tube amps in linearity. If you’re working in a specific context (e.g., audio, RF, or a particular circuit), let me know, and I can dive deeper into design strategies to mitigate intermodulation distortion!

 

[sparky]

A number of reasons:

1. Manufacturers addressing a price point more so than the quality of product. There are always buyers of cheap amps.
2. Bad engineers. Just getting your sheepskin from some mail-order college does not guarantee you know what the farg you are doing.
3. Bad hearing. You'd be surprised by the number of people with a tin ear who cannot hear for shit.

On that note......I'm wondering what your take on bose is Toob??>>>

~S~

 

[Sherlock Holmes]

So why are there crappy amps? I'm guessing this is another thing that China has ruined. Don't tell me I can walk into Walmarx and see plastic amps on the shelves!

Can you list a few examples of these crappy amps along with their specs?