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More bass with the SSE

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Hello everyone,

I'm gathering parts to build the SSE. I already have:
- Power Transformer: Allied 6K7VG - PRI:110-120V, 50/60HZ, 750VCT @ 150DCMA, 3A @ 5V, 6.3A @ 5.0A, LEADS
- Choke: Triad C14X - 6H; Tol -20%, +50%, Cur 200mA; Leads; DCR 150 Ohms
- Output Transformers: EDCOR XSE15-8-5K

Although this is my first tube amp, I have read a lot about it and my preferred tubes are KT 88 and EL 34, also was thinking about the 6L6. I'll install a switch for cathode bias resistor.

I intend to use aux motor run capacitor and toggle switches for UL / Triode mode, CFB and disabling SS / Tube Retifier.

I have two types of speakers, one is a hand made full range speakers, Audio Nirvana Super 8 - frequency response from 42 Hz to almost 20.000 hz, and at least 98 db efficiency. The other is a vintage brazilian speaker that copy of JBL L65 - 20 (?) to 20.000 Hz, 95 dB.

I love a good bass, then I would know which tubes could be more suitable. Maybe KT 90?

Thank you all and have a nice week.
Sgrilli AD
Then... get a 1000 watt Crown, a subwoofer, and an active crossover, and amplify all the bass to your heart's desire that way. Its not like the ear is sensitive to exquisite (and frankly almost non-existant) distortion of the 17Hz to 100Hz band. You want thump. Get it by way of the "third option", the subwoofer and independent amplifier. "Triamped!"

Then, make the SSE using whatever the best tube/components are in your research.

I'll be dissed ... but this combination works beautifully. Further, by simply changing the master-volume on the separate subwoofer amplifier (or the cross over, or both) ... you can trivially vary the relative amount of "woof" you're getting. The one volume control attenuator for the system scales the whole thing.

[back to our regular abstract tube programming]

Hi GoatGuy,

I'm not fluent in English, so I did not totally understand your answer.

But, where I unterstood, you suggested that I have a subwoofer (1000 watt??) and an active crossover ... Why is that?
I have fullrange speakers wich no need any crossover. And the subwoofers already has the built-in crossover, right?

I dont want to have a home theater or something like this. I just want to hear music with a good bass with the tube amp and the speakers that I currently have. Then, I would make good use of all the features of the valves for this purpose. Just it.

Anyone else could help?

Sgrilli AD
The 3-channel solution


Não "home theater", mas ... usando a física de áudio de baixa freqüência para realizar o que você deseja, sem ter de impor muita dificuldade em seu amplificador.

Áudio de baixa frequência não é muito específico em termos de "fonte". Você pode ter uma fonte de freqüência muito baixa em quase qualquer lugar na sala, e seu ouvido não vai ser capaz de encontrar a sua localização.

Então, empregar esta física para completar uma solução para os três problemas difíceis seu desejo declarado requer.

[1] "poderosa freqüência baixa" - requer muito mais poder em proporção ao que você percebe como "poder" do que o mesmo volume nas freqüências médias. Ainda menos energia é necessária para altas freqüências.

[2] tubo de vácuo amplificadores são famosos por serem incapazes de atingir alta potência de áudio de baixa freqüência sem dinheiro notavelmente excesso.

[3] maior poder de alta potência de áudio de freqüência ultra-baixa pode facilmente danificar seus drivers excelentes, ... mas, se a parte de ultra-baixo é removida, e separadamente amplificado ... então seus principais alto-falantes são salvos.

O ponto é que você pode continuar em seu caminho escolhido para o amplificador SSE, sem ter que onerar o projeto, ou já possuiu seus dispositivos a extremos. E eu prevejo ... você vai ser feliz.

Eu coloquei mais discussão abaixo (abaixo do Inglês)


[The above compliments of GOOGLE TRANSLATE. Here is the english:]

Not "home theater" but ... using physics of low-frequency audio to accomplish what you desire, without having to impose too much difficulty on your amplifier.

Low frequency audio is not very specific in terms of "source". You can have a very-low frequency source almost anywhere upon the room, and your ear will not be able to find its location.

So, employ this physics to complete a solution to The Three difficult problems your stated desire requires.

[1] "Powerful low frequency" - requires far more power in proportion to what you perceive as "power" than the same loudness in middle frequencies. Even less power is required for high frequencies.

[2] Vacuum-tube amplifiers are famous for being unable to attain high-power low-frequency audio without remarkably excess money.

[3] High power, ultra-low frequency audio's higher power can easily damage your excellent drivers, ... but if the ultra-low part is removed, and separately amplified ... then your main audio speakers are saved.

The point is, that you can continue on your chosen path for the SSE amplifier, without having to encumber the design, or your already-posessed devices to extremes. And I predict ... you will be happy.

- - - - -

* I am NOT advocating a 1,000 watt subwoofer speaker. But I am advising you that a 1,000 watt amplifier is a very good solution. (Why? Because most "1000 watt" amplifiers cannot produce even 1/3 of that continuously. The extra watts are there for occasional powerful bass.)

* I am advocating that you simply tap (not really "cross-over" but simply extract out an additional bass channel between 15 Hz and 80 Hz). This would be tapped by a small, high-quality 4th order filter. Solid state. On the input side. It would also make a great little 12AX7-type tube project.

* You may find that without the subwoofer, your full-range speakers will be "nice", but lacking a little bass. My solution is simple, elegant, and technologically sophisticated beyond only "2-channel purists" ideals.

(Você pode achar que sem o subwoofer, seus alto-falantes full-range vai ser "agradável", mas falta um pouco baixo. Minha solução é simples, elegante e sofisticada tecnologicamente além apenas "2 canais puristas" ideais)

I wish you good luck. If you would like a diagram, see the attached.


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The 3-channel solution

Hi GoatGuy,

Thank you for your response and for patience in trying to make me understand.

I got a doubt in the diagram, even drawing a bass channel, it seems to me that all all sound frequencies would still heading for the main speakers. Am I right?

If I extract a bass channel directly into the tube amp. Is it possible? How to do this? In that case, I'll need an active filter?

Thank you
Sgrilli AD

You're welcome...

All the frequencies would be going to main speakers, but not all the power. The additional power would be going to the subwoofer. If you want to attenuate the lower frequencies, you always could just use a simple capacitor-inductor combination (passive high-pass filter). Many of our audiophiles here though deplore the sound of capacitors, so this will be challenged as a good idea.

The bigger problem they introduce is that there is definite phase group delay ... which can change the perception of ultra-baixo freqüência, of how "fast" it is, and so on.

ACTIVE filtering can be better - but introduces "color" of its own into the signal path. There are no perfect solutions!

In other words... the diagram, as I show it, remains the closest-to-straight-through that will still accomplish your high-bass desire.

I don't know why the question asked is not being answered here. The question seemed to ask how to get the best bass out of an SSE. I will answer that, but I need to explain a few things. Just stating that "you need a subwoofer" without explanation is not a valid answer, even though it may be a valid choice.

High power, ultra-low frequency audio's higher power can easily damage your excellent drivers, ... but if the ultra-low part is removed, and separately amplified ... then your main audio speakers are saved

I highly doubt that an SSE can damage either of your speaker systems no matter how you run it. A solid state amplifier run into clipping will produce a lot of high frequency energy which can blow tweeters. This is not the case with most tube amps. Woofers are usually blown from long term thermal damage, or overexcursion of the cone, both come from too much power, either tube or solid state. An SSE does not have too much power for either of these speakers.

Vacuum-tube amplifiers are famous for being unable to attain high-power low-frequency audio without remarkably excess money.

I can demonstrate several reasonably priced tube amps capable of high power at low frequency. I have one under development that makes 300 watts at 20 Hz. There are two reasons for a blanket statement like this, and cost is involved, but this statement is not entirely true. There are two reasons that many tube amps are weak in the bass region.

Most tube amps use an output transformer to transform the audio signal from the high impedance tubes to a low impedance needed to drive the speaker. The low frequency response of this transformer is directly related to its physical size, and therefore it's cost. An SSE with the right OPT can produce full power at 20 Hz without saturation distortion. The EDCOR XSE15-8-5K may not be the right choice for the JBL clones.

Many tube amps, and most SE tube amps do not use negative feedback. Negative feedback will lower the distortion, and increase the Damping Factor of the amp. Too much feedback tends to suck the life out of the music. Most SE amp users prefer no feedback at all. Some speaker systems need a relatively high Damping Factor for well controlled bass. Dynamic sounds like the kick drum hit can sound "loose" on some speaker systems with an underdamped amp. The AN speaker was designed for these types of amps, but the JBL clones were made for a solid state amp with a good DF. The DF of an SE amp is relatively low. The tube choice will affect it. So does the idle current, and the OPT.

I have an SSE with exactly the same components that you specified. I run it with Yamaha NS-10M Studio monitors which have limited bass below 70 Hz, so I use a subwoofer. The little Edcor XSE-15-8-5K OPT's begin to roll off the low frequencies below about 90Hz so I have the sub's LPF set to 120 Hz. It is a cheap 10 inch amplified speaker box that claims 100 watts, but it does the job perfectly in a 10 X 12 foot room. I don't try to play this system very loud, but it does do OK with anything I feed it. I am building a bigger sub using a Parts Express 15 inch driver and 300 watt plate amp. The bigger system is not to get louder, it's to get lower since I have been playing with a music synthesizer.

I have another SSE that uses the larger CXSE-25-8-5K transformers playing through a home built set of speakers that use 15 inch woofers with 96db efficiency. There is NO subwoofers, but the bass from this SSE can be felt INSIDE the HOUSE ACROSS THE STREET! This SSE can produce 15 watts from 20 Hz to 18 KHz. NO SUB NEEDED, or wanted.

In this case the Electro Harmonix KT88 or 6550 tube produces the best most well controlled bass and power. I use UL mode with the CFB turned on. Pink Floyd, Depeche Mode, Metallica, all sound great at high volumes. The 6L6GC doesn't have the solid bass, but is a good all round performer. I use the EL34 in triode with no feedback for the best detail with female vocals. It still shakes the walls in my house, but not the neighbors, since it only makes 6 watts.

An "8 ohm" speaker is usually not 8 ohms. It should be close to 8 ohms at 1KHz and will vary all over the place at other frequencies. It will go way up, maybe 20 to 100 ohms at the resonant frequency of the woofer, and be quite low below this frequency. Most modern audiophile quality speakers publish this curve. The small Edcor will start to saturate (distort) at anout 80 Hz with a true 8 ohm load at 10 to 15 watts. It will go lower at higher impedances.

You already have the small Edcors, so I would try them. They should be Ok with the AN's. There is a chance that the impedance curves of the JBL clones will allow the small OPT's to produce reasonable bass. There is also a chance that they will not. If the speaker's impedance goes up in the region where the OPT starts to saturate, then things can work. If the speaker's impedance remains flat, or drops, then the bass can sound weak or distorted.

if the bass is not good enough with the small OPT's, then the larger Edcors or a subwoofer system can be considered.

If you do think about a sub, then you want one that uses a line level input, and has a built in LPF. Avoid anything that connects to the speaker leads when using a tube amp for the main speakers. Connecting it as the Goat Guy says (across the SSE inputs) usually works the best, and is the way I have mine wired. There are several other SSE builders who have used the small Edcor OPT's with a sub and a full range driver like the AN, or Lowthers.
Uh... "TubeLab"

I'm surprised by the offense you took at my recommendation, while you yourself did exactly the recommended 3-speaker configuration for at least one of your systems.

Your reason was (paraphrased), "because my stereo speakers didn't have good low-frequency response, I added a powered subwoofer to reinforce what bass they were suppressing". Well, there you are. Just what I said.

Further, you go on to cite your other system having magnificent 15 inch drivers, (paraphrased), "and no subwoofer needed, or wanted". Well, there you are! The problem isn't an amplifier problem, but in your first case, a speaker issue. Which were both solved by adding more surface area to the speaker subsystem that reproduces the bass. Toots!

And then you take on my notion that "more bass in SSE requires more expensive circuit accoutrements" (paraphrased). Uh... then you go on to say that the output transformers need to be selected to actually achieve the frequency response (to avoid saturation). You didn't talk about larger bypass caps on the preamps, and so on, but they too figure into this area. Needless to say ... again ... you've just confirmed what I said: it costs more to effectively shore up any kind of transformer-output amplifier design. Hell, it costs more for capacitor-protected designs as well.

However, thank you for the agreement at the end about choosing to tap things at the LINE level, and not the speaker/output level. While one could, the levels are high enough to be annoyingly difficult to tame as inputs to a separately amplified subwoofer channel. Also, one is way more likely to get phase-delay matching by tapping the line level for subwoof, than tapping the possibly phase delayed output power stream.

Carry on, folks! Its all good.
As I said, people would object to my advice.
But... it remains good advice.

And "TubeLab's" demonstration that better (larger) speakers also solves the problem remains good practice too!

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I'm surprised by the offense you took at my recommendation

I do not "take offense" to anything you said. I am attempting to explain that the use of a subwoofer is valid, but not the only option here. Just simply stating that he needed a sub without an explanation why, doesn't help him or any other reader with a similar question.

I have a full time engineering job and I have to make these posts from a smartphone at work, since forum acces is restricted, and I felt that this one wasn't being completely answered. In fact he asked for another opinion.

Neither he, nor you attempted to describe what "good bass" is. It has a different meaning to different listeners. He did state that he did not want a HT system.

I also explained that the complex interaction between the speaker and OPT plays the largest role in the bass reproduction ability of any tube amp.

I explained that you will not get deep clean bass from the little Edcor OPT on small speakers, and I chose to augment my similar system with a cheap sub. I have nothing against such systems. I use mine for a home recording studio, and have tweaked it out for the most flat frequency response, but can't go below 50 Hz with my cheap sub, so I am building as bigger one. This system stresses sonic accuracy over awesome listening.

My other SSE system which does use bigger speakers AND a bigger OPT is completely adequate without a sub. I use it for most listening, and switch to a 125 WPC P-P tube amp where "rock concert in the living room" is the listening criteria. The SSE with the small Edcors does NOT work well with these big speakers. It distorts badly with heavy bass at high listening levels.

It is possible that the small Edcor will work good enough for his larger speakers, but this is completely dependent on how the OPT and speaker interplay at his chosen volume level, with his chosen music. Only a listening test will tell.

If this isn't good enough, the only valid choices are larger OPT's or a sub. The frequency response of the SSE built with the recommended components is sufficient to go to 20 Hz with a proper OPT.

Goat Guy.....does this refer to the 4 legged, or 4 wheeled variety, or something else entirely.
Wow ... I could not expect better answer ... directly from Mr. George!

Well, I'm sure the ways were shown.

I'll build the SSE with EDCOR I have on hand and see what happens. I will follow exactly what Mr. George recommends on part list and add a input selector switch, because I do not intend to use a preamp for now, only a phono preamp for my turntable. I´ll also play DVD and CD player.

I think it is better to make now a subwoofer output if I want to use it in the future. I really like to have this output in SSE, since I will not have a preamp now. If possible, I'd like Mr. George sent me a diagram showing how to make this output.

I'm sure many readers might enjoy these discussions and I appreciate the help.

Sgrilli AD
That is a loaded question, because it depends a great deal on what you are going to use for a subwoofer. Do you need a line-level cross over network? If you are just going to buy a typical powered subwoffer, they often already have the necessary low-pass filters. In that case you just think of the subwoofer as another power amp to drive and wire it accordingly. If you want to control the SSE and the subwoofer with the same volume control, that complicates things. You would needed some sort of line driver/buffer circuit to drive the cables and the SS amp that will power the sub. This is what your preamp would do for you.
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