Inexpensive tube amplifiers that produce bass down to 20hz, flat?

vinylkid58 said:
4dB down @30Hz isn't bad at all for a small SE trans. I have a pair of Edcor GXSE opt's here that are probably close spec wise.

You'll also need more power. STG, someone in Edmonton has a push-pull amp you could try out?

jeff
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I agree with Jeffs assement of more power. If the claim of 97 db's/m at 40 watts is the correct data I read, thats about 81 db/w. They recomend 50 wpc minimum I believe, that sounds reasonable. If want to go with Tubes you'll should have a minimum of the 50 wpc they recomend. I Really like the MP301, just not for this Application. Musical Paradise has a bigger Amp that looks very tempting, and is well reviewed I believe.

I don't nomally recomend High Power Amps, but in this case a good 100- 200 Wpc SS power Amp might in order for these speakers. Just a suggestion. I really like Bryston's older 3B ST for your speakers, but there aren't many out there. There other Amps get quite expensive fast unfourtunetly
 
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Tinkerbelle said:
The RSPM Mk IV has filter, slope and tilt controls. The graphs shown in post #4 are the effects of the controls not the speaker response capability. The text comments on the graphs are difficult to read.

These speakers will perform down to the 20Hz range. The frequency response 1 metre on axis with measuring equipment low limit at 20Hz is given here: http://www.audiokarma.org/forums/attachment.php?attachmentid=382764&d=1350224913

A description of the controls is given here: http://www.marklev.com/IMF/RSPM/index.html

A brochure with 5 graphs is here: http://www.imf-electronics.com/Home/imf/speaker-range/reference-speakers/rspm/rspm-brochure-2
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Tink, I'm not sure what else I could look at, but those graghs still look like almost 20db down at 20hz..
(no matter which of the graphs there I look at, unless there is something I'm not seeing)
 
Bottom line is, graphs aside, these speakers have some serious bass reproduction. Maybe I'll get them measured on my own just to see what they're capable of. Regardless, they have deep, low bass and I have already discovered that better output transformers make a world of difference. When Garry brought the MP501 I shat bricks, seriously, it was that good. I've heard good subwoofers but these speakers take the cake.

Also, regardless of the room, these will eventually be going into a much bigger room eventually so the fact that it cannot produce that bass now doesn't matter - it will need to later on.

Anyway, that Bryston isn't a bad option actually. I'm going to have a look into that and see if I can perhaps find one or know of someone with one.
 
Graphs certainly aren't the last word IMO. If they were, the Eico HF81 wouldn't bring 4 or 5 hundred for a restore-able piece.
I wonder how these would be with one of Bob's ST120s? For that matter, a properly hopped up ST70 can give you 50 watts no sweat with KT88s. A bigger power TX is a must though when wringing one out. Pak used to suggest buying two, and making mono blocks out of them and having a set of outputs to re-sale. I'd like to do that some day.
 
Before going crazy here.....

canuckaudiog,

Before time, effort and money, find out what you are REALLY missing in bass output.

In your first post (#1) you stated-

"However I don't have a technical measuring tool, only my ears, so it's possible it could be and I have no idea."

OK, fair enough.

On your #16 post you stated-

"I've tuned plenty of set-ups to know what a flat down to 20hz set-up sounds like, and this is tuning with an RTA not by ear. So I know what I am talking about when it comes to frequencies this low.. I am not just saying this without having had any experience. "

Again, fair enough, however you just contradicted yourself!:nono:
(Not a problem, people do this all the time!):D

Why not borrow the RTA and TEST your home system?:scratch2:

This way you can prove (or disprove) what you are hearing (or not hearing) when trying to gauge the performance of your home stereo.

You should know that bass REQUIRES lots of power, esp. at the lowest end (What with all the HEAVY wiring, big A** capacitors, giant fuses etc. used in car systems) and you expect to DUPLICATE that in the home with a SMALL single ended TUBE amp. with TINY output transformers? No F****** way!

You want butt shaking bass down to 20 Hz?, get a SS amp. with some BALLS, and save that nice tube amp for another room or bedside system.:yes:

Low bass requires POWER, POWER requires heavy hardware, YES, you can get "heavy hardware" in a tube amp., but it will (because of design) cost you big bucks!:sigh:

Another thing, home and car systems have to do different jobs for different reasons, and there may be little "common" ground between them, as most expect a home stereo to "have good imaging", where as a car system has to have "good thump" as some call it.

I am NOT getting into the politics of the use (and MIS-use) of powerful car systems, I am just telling you that low powerful bass requires a sizable amount of amplifier power and your tube amp. will not fit the bill.

Mark T.
 
markn2wae said:
canuckaudiog,

Before time, effort and money, find out what you are REALLY missing in bass output.

In your first post (#1) you stated-

"However I don't have a technical measuring tool, only my ears, so it's possible it could be and I have no idea."

OK, fair enough.

On your #16 post you stated-

"I've tuned plenty of set-ups to know what a flat down to 20hz set-up sounds like, and this is tuning with an RTA not by ear. So I know what I am talking about when it comes to frequencies this low.. I am not just saying this without having had any experience. "

Again, fair enough, however you just contradicted yourself!:nono:
(Not a problem, people do this all the time!):D

Why not borrow the RTA and TEST your home system?:scratch2:

This way you can prove (or disprove) what you are hearing (or not hearing) when trying to gauge the performance of your home stereo.

You should know that bass REQUIRES lots of power, esp. at the lowest end (What with all the HEAVY wiring, big A** capacitors, giant fuses etc. used in car systems) and you expect to DUPLICATE that in the home with a SMALL single ended TUBE amp. with TINY output transformers? No F****** way!

You want butt shaking bass down to 20 Hz?, get a SS amp. with some BALLS, and save that nice tube amp for another room or bedside system.:yes:

Low bass requires POWER, POWER requires heavy hardware, YES, you can get "heavy hardware" in a tube amp., but it will (because of design) cost you big bucks!:sigh:

Another thing, home and car systems have to do different jobs for different reasons, and there may be little "common" ground between them, as most expect a home stereo to "have good imaging", where as a car system has to have "good thump" as some call it.

I am NOT getting into the politics of the use (and MIS-use) of powerful car systems, I am just telling you that low powerful bass requires a sizable amount of amplifier power and your tube amp. will not fit the bill.

Mark T.
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You make some fair points there. :)

I guess what I was really getting after was a little miscommunicated. I'm not looking for 20hz bass reproduction, I'd have to be some sort of bass junkie to really want 20hz bass. What I really meant by saying I know what 20hz sounds like is that I know the system I have at home is capable of 20hz bass - or at least, very deep bass, deep bass I am not getting from this little tube amp. My question was aimed at 20hz because I want to get the full spectrum. I realize that it's very challenging to achieve 20hz with any sort of set-up, but that's not the goal here more or less just a byproduct. I just want to be able to full emphasize the system I have now, and I know that one thing that is important is having an amplifier that is flat +/- 1db 20hz-20khz. That's what I am after :) The speakers are an afterthought for what frequency range they play.

The only reason I emphasized these speakers have low bass is because I wanted to stress the importance of why it was that I want to get an amp that specifically is able to play 20hz flat, so that I am getting the full frequency range out of the speakers without bottlenecking their performance.

I hope that makes sense? It was kind of an oddly posed question, I probably should have explained it better in the first place.

Now, I do understand my current tube amp doesn't give me the bass I am looking for. That is the whole point of this thread. But regardless yes, I do understand the main differences between car and home systems. I've sold both and own two high end systems, car and home. Not trying to say I'm an expert but I have experience with it, with SPL and all that other fun stuff. I'm not trying to recreate my car audio experience at home, I'm just merely aiming for an amplifier that has a flat frequency response so I can utilize my speakers the way they are meant to be heard.

OK.. enough explaining now. :)
 
If I may, let me emphasize what has been mentioned before, but cannot be emphasized enough, and that is that while you do want a flat frequency response from 20 Hz to 20 kHz, it is far more important to obtain an amplifier that has a flat power bandwidth response from 20 Hz to 20 kHz. Simple frequency response performance (determined by tests made at typically 1 watt) is one thing. But having an amplifier that can produce full power across the entire audio spectrum at low distortion is quite another. Specifications produced from back in the day are hardly very clear about these issues. The better manufacturers typically gave some indication of power bandwidth, while far more did not. It was not until the FTC stepped in that the issue was made crystal. As others have stated however, it takes power to produce bass, so it takes adequate power bandwidth to produce it -- not simple "frequency response".

Regarding your budget and goals, the models I mentioned earlier all have very capable performance down to 20 Hz, allowing your speakers to produce the full bass they are capable of.

Dave
 
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dcgillespie said:
If I may, let me emphasize what has been mentioned before, but cannot be emphasized enough, and that is that while you do want a flat frequency response from 20 Hz to 20 kHz, it is far more important to obtain an amplifier that has a flat power bandwidth response from 20 Hz to 20 kHz. Simple frequency response performance (determined by tests made at typically 1 watt) is one thing. But having an amplifier that can produce full power across the entire audio spectrum at low distortion is quite another. Specifications produced from back in the day are hardly very clear about these issues. The better manufacturers typically gave some indication of power bandwidth, while far more did not. It was not until the FTC stepped in that the issue was made crystal. As others have stated however, it takes power to produce bass, so it takes adequate power bandwidth to produce it -- not simple "frequency response".

Regarding you budget and goals, the models I mentioned earlier all have very capable performance down to 20 Hz, allowing your speakers to produce the full bass they are capable of.

Dave

Dave
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Thanks so much Dave, that makes a lot of sense. I am going to re-read your post again.
 
I want to clarify a few things and try to make a conclusion here.

1. It is almost impossible to find a normal speaker can produce 20HZ flat. In most designs, -3db point is at about 40hz.

2. Solid state amps can easily produce 20hz flat since solid state amps do not need to use output transformers.

3. Good tube amps with huge output transformers can also produce 20hz at about -1 to -2db. 20hz flat is also possible if the output transformer is huge enough and apply deeper negative feedback loop. The problem is the larger the transformer the higher the cost. Also, the high frequencies performance can be very poor if a huge size OPT is not designed properly. Too much negative feedback could also make the sound unnatural. It is like MSG in the food.

4. Frequency respond is not directly related to the power. Car audio is 12V, it requires a low of current to achieve the same wattage. For instance, we need to achieve 100W. In car audio system, the current draw is 100W/12V = 8.33A. In a home solid state amp, the current draw is approx. 100W/50V = 2A. In a tube amp, the current draw is usually 100W/400V = 0.25A. That is the main reason that car audio requires thick wire and big caps.

5. There are two solutions here. First one, add a powered sub. Second, get a equalizer to increase the gain on 20-40hz. Both of these solutions have their weakness. Equalizer was a very hot item in the Hi-Fi industry when I was a kid, but it can degrade the sound quality, making the sound quite unnatural, so it was abandoned in the home audio industry, but it is still being used in the recording industry. It is a handy tool to fix imperfection.

6. Nothing is prefect. We need to balance the cost, performance gain and loss.
 
gtube said:
I want to clarify a few things and try to make a conclusion here.

1. It is almost impossible to find a normal speaker can produce 20HZ flat. In most designs, -3db point is at about 40hz.

2. Solid state amps can easily produce 20hz flat since solid state amps do not need to use output transformers.

3. Good tube amps with huge output transformers can also produce 20hz at about -1 to -2db. 20hz flat is also possible if the output transformer is huge enough and apply deeper negative feedback loop. The problem is the larger the transformer the higher the cost. Also, the high frequencies performance can be very poor if a huge size OPT is not designed properly. Too much negative feedback could also make the sound unnatural. It is like MSG in the food.

4. Frequency respond is not directly related to the power. Car audio is 12V, it requires a low of current to achieve the same wattage. For instance, we need to achieve 100W. In car audio system, the current draw is 100W/12V = 8.33A. In a home solid state amp, the current draw is approx. 100W/50V = 2A. In a tube amp, the current draw is usually 100W/400V = 0.25A. That is the main reason that car audio requires thick wire and big caps.

5. There are two solutions here. First one, add a powered sub. Second, get a equalizer to increase the gain on 20-40hz. Both of these solutions have their weakness. Equalizer was a very hot item in the Hi-Fi industry when I was a kid, but it can degrade the sound quality, making the sound quite unnatural, so it was abandoned in the home audio industry, but it is still being used in the recording industry. It is a handy tool to fix imperfection.

6. Nothing is prefect. We need to balance the cost, performance gain and loss.
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Thanks for that very useful information Garry.

Really what I am after is to just get the frequency response to spec out of the speakers using a proper amplifier. We both heard with your MP501 the difference in the bass, it was quite astounding actually. So, I am not concerned about achieving a flat response from 20hz-20kHz, I am really just after getting the proper frequency response these speakers are capable of. Although, adding a subwoofer would be the ideal way to go, for my application it isn't really necessary for my music listening (which a few others have clarified earlier).

Again thank you for that information, that's insightful and useful.
 
Just curious - are the output impedances / damping factors of the two amps known? Looks like you'd get a bit of bass boost with a lower damping factor.
 
Kegger said:
...

Remember 3db is half as loud, 6db is very very down an NOT considered
to be a useful cutoff point to determine useful hearing/performing output.

...
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Kegger:

Not to contradict your other fine points, I agree with them, but 3 dB is not half as loud. It is half the power. It is also the smallest volume change that most of us will hear as a perceived volume change. Smaller then that we will tend to describe it in other terms like more or less "full" or some other descriptive but perhaps not technically accurate term. The half volume point is 10 dB which is also a 10x's change in power.

And yes, at -6dB the change in output is very noticeable and objectionable. A pair of speakers I built had a 7 db difference in the treble and bass output and I initially tested it without the pad on the tweeter. Both my son and my wife told me, in no uncertain terms, to fix the bass, they couldn't hear it. The pad fixed it.

Just wanted to correct the half power / half volume thing.

Shelly_D
 
canuckaudiog:

Putting aside all the questions of what the lower end of your amps power bandwidth is and whether it goes down to 20 Hz or not, it is clear that you are dissatisfied with the bass of your system with your current amp speaker combination. You have also clearly done the research to find out if another amp will do better and it clearly does.

Your choices are now:

1) Modify the amp. You have indicated you do not wish to do this.
2) Replace the amp
3) Replace the speakers
4) Modify the speakers

I assume, from your comments, that you like the speakers as they are and since you don't wish to modify your amp you would also be reluctant to modify your speakers. This leaves replacing either the amp or speakers. You are clearly leaning toward replacing the amp.

At this point you have done all the homework you need to in order to decide which way to move forward. You do need to be aware that there are tradeoffs no matter what way you proceed.

You currently have, if I read gtubes description correctly, a no feedback single ended amp. If you go push pull, the likely hood will be it will have negative feedback. That does several things to the amp. It flattens and extends the frequency response, reduces the output impedance to provide better damping factor and reduces harmonic distortion across the audio spectrum. This will affect the character of what you hear. I can't describe the changes you might hear cause all my amps use negative feedback and I like it, others don't and you might be among those. I understand that the character of the midrange and treble may be affected by the change but I don't know for sure. Also, most solid state amps will be flatter then what you have to a much lower frequency, but again, the trade off may be what you are liking in the upper registers. A different single ended amp may go down further, indeed you seem to have found one in your friend's amp. Did you like the rest of the music as well. If so, that may be how you want to proceed. No one can decide this but you. With single ended no feedback designs, it is not possible to transfer the musical experience of one set of speakers to another because it is the feedback that provides a "correcting" signal back to the amps input to adjust for any distortions that occur. Without that there are no corrections and you just hear what results. Given the following that these type of amps have it is very pleasing to listen to but I would submit that each amp/speaker/room combo is unique.

All of this is boiling down to it now being a matter of taste. If doesn't matter what road you move in as long as:

1) you can afford it and
2) you like it.

Good Luck

Shelly_D
 
The main issue with the current speakers is going to be power.

They are not efficient, I'd imagine Most Any Amp Besides the Low
power single ended amp used will provide better bass performance.
(just aren't the kind of speakers to work best on low power SE amp)
 
shelly_d said:
canuckaudiog:

Putting aside all the questions of what the lower end of your amps power bandwidth is and whether it goes down to 20 Hz or not, it is clear that you are dissatisfied with the bass of your system with your current amp speaker combination. You have also clearly done the research to find out if another amp will do better and it clearly does.

Your choices are now:

1) Modify the amp. You have indicated you do not wish to do this.
2) Replace the amp
3) Replace the speakers
4) Modify the speakers

I assume, from your comments, that you like the speakers as they are and since you don't wish to modify your amp you would also be reluctant to modify your speakers. This leaves replacing either the amp or speakers. You are clearly leaning toward replacing the amp.

At this point you have done all the homework you need to in order to decide which way to move forward. You do need to be aware that there are tradeoffs no matter what way you proceed.

You currently have, if I read gtubes description correctly, a no feedback single ended amp. If you go push pull, the likely hood will be it will have negative feedback. That does several things to the amp. It flattens and extends the frequency response, reduces the output impedance to provide better damping factor and reduces harmonic distortion across the audio spectrum. This will affect the character of what you hear. I can't describe the changes you might hear cause all my amps use negative feedback and I like it, others don't and you might be among those. I understand that the character of the midrange and treble may be affected by the change but I don't know for sure. Also, most solid state amps will be flatter then what you have to a much lower frequency, but again, the trade off may be what you are liking in the upper registers. A different single ended amp may go down further, indeed you seem to have found one in your friend's amp. Did you like the rest of the music as well. If so, that may be how you want to proceed. No one can decide this but you. With single ended no feedback designs, it is not possible to transfer the musical experience of one set of speakers to another because it is the feedback that provides a "correcting" signal back to the amps input to adjust for any distortions that occur. Without that there are no corrections and you just hear what results. Given the following that these type of amps have it is very pleasing to listen to but I would submit that each amp/speaker/room combo is unique.

All of this is boiling down to it now being a matter of taste. If doesn't matter what road you move in as long as:

1) you can afford it and
2) you like it.

Good Luck

Shelly_D
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Thanks Shelly, that sums it up very, very well.

As it currently stands I am not so sure I can get the money together to afford the MP501 ($1200). I really enjoyed it, in fact it blew my mind just how great it sounded, the combination between that amplifier and my speakers was like a match made in heaven. I have never heard such sweet, smooth sound.

I think what I am actually leaning towards right now is either finding a restored set of tube amplifiers, but you make an extremely compelling point that if I am enjoying this amplifier right now, besides the bass output, I may not get that same fidelity enjoyment from a different unit due to its different circuitry.

So, I think in order to gain the most ideal upgrade without breaking the bank, because like I say I don't think I can realistically afford the $1200 MP501 (as much as I really enjoyed it!), I think I am actually leaning towards modifying the MP301 and putting on bigger OPT's, so it looks like I am going to head down that road. Worst case scenario, I buy a different amplifier to use for now, gain some insight on different circuitry in tube amplifiers and have to sell it later on to afford the amp I really want.

I've been doing some conversing with Garry at Musical Paradise and with his extensive experience has recommended to be careful with what OPT to choose. I have no experience in this area so I will have to tap into the opinions and advice of others. He has recommended a Hashimoto OPT, which I understand to be very good, but also very expensive.

So then, let's go down this route for a bit. Would I be able to get what I am after, by modifying the OPT's, for less than say $500? I think doing the modifications to the amplifier is not challenging, creating a wooden chassis for the new OPT's would be more difficult but I am sure I can get help with that locally. It's more the cost of the parts.

Does anyone have any recommendations based on experience for a good OPT at a decent price, say $200-$400 for the pair, that will give me the 20hz bass response with an even power bandwidth? One thing I'd like to stress is that even though these are insensitive speakers, the 6.5wpc SET amp provides more than enough volume. I estimate I use at most, 5 watts, and that is on the extreme side for me. I estimate this based on VU meters from past receivers I have used.

Thank you once again, this thread has been very insightful.
 
I would say NO, a low power SE amp is not the best choice for THOSE speakers.
Changing those Output Transformers is Not going to give you the power needed.

Within the "budget" to get the type of amp/power needed to get the full bottom
from those speakers your looking more at something like PP KT88 at like "60wpc"
or so to do them justice, it would be pretty much wasted money for new output
transformers on the amp you have now to power those speakers.

Your really looking at needing/wanting different amps altogether for those speaks.
(those are not low power single end amp friendly speakers)

--------

Power not meaning there volume overall increasing, but low end grunt to drive the
speakers properly, to get the full range they are capable of. (mainly in there bass)
 
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Kegger said:
I would say NO, a low power SE amp is not the best choice for THOSE speakers.
Changing those Output Transformers is Not going to give you the power needed.

Within the "budget" to get the type of amp/power needed to get the full bottom
from those speakers your looking more at something like PP KT88 at like "60wpc"
or so to do them justice, it would be pretty much wasted money for new output
transformers on the amp you have now to power those speakers.

Your really looking at needing/wanting different amps altogether for those speaks.
(those are not low power single end amp friendly speakers)

--------

Power not meaning there volume overall increasing, but low end grunt to drive the
speakers properly, to get the full range they are capable of. (mainly in there bass
Click to expand...

I get what you're saying, but the thing is the MP501 that Garry tried out I really, really liked. I could have listened to that for days on end. But it's the high price tag I can't afford. That amp is an SET no negative feedback amplifier just like the one I have, but it is more robust and has bigger OPT's as well as dual power supplies. I found the low end grunt on that unit was plentiful.

I guess I haven't stated this yet but the room these speakers are in is 9'x11.3'. It doesn't take much power to get these speakers to sing.
 
You've asked an ignored all/many of the responses in this thread. (even experienced)
Just decide for yourself what YOU want to do an what YOU think the capabilities are.

---

BUT those speakers are not good match for a low power set amp, I have expressed as
much as I can here, with no more to add from this point, good luck in your quest here. ;)
 
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