Thinking about trying a tube amp. Thoughts.

skipshot12 · August 2025

^ Thanks for the above.

heiney9 · August 2025

skipshot12 wrote: »

I have a some questions for the pros regarding tube amps.

1. Do tube amp owners pursue any active cooling as some SS amp folks do?
2. Are there be any benefits to keeping the tubes/amp cooler?
3. Any negative things in actively cooling a tube amp and/or it's tubes?

4. Are my SDA SRS (Gen1) speakers something that would work well with a tube amp?
We listen loud with the SDA's being driven by a 500w per SS amp.

Also, I'm thinking about a nice tube amp would work really well with my Infinity Prelude MTS speakers.
They have a sub that's driven by a B.A.S.H. 850w class d amp.

These are the specs for the Prelude MTS Tower....
Drive-units (all ceramic-aluminum matrix): 1" dome tweeter, 3*"-cone midrange, four 5*"-cone midbass. Crossovers: 300Hz, 2kHz, 24dB/octave. Frequency response: 80Hz-22kHz, ±3dB; 100Hz-20kHz, ±1.5dB. Nominal impedance: 4 ohms, ±1dB. Sensitivity: 90dB/2.83V/1m. Power requirements: 25-500W.

5. Any thoughts on a tube amp for my Prelude MTS's?

These speakers can be driven completely, including the subwoofer, with the amp of choice or, it has the ability to allow the subwoofer to be driven by the internal class d amp allowing the chosen amp to just drive the tower drivers.

The Prelude MTS's ceramic-aluminum tower drivers can be a little bright, I'm thinking a nice stereo tube amp may be a good choice for the towers, letting the internal Class D amp drive the subs.

Apologies pearsall, not trying to hijack your thread.

"Active cooling" shouldn't be necessary unless you are using your gear in an enclosed space. A single ended Class A amp sounds better "at temp" than it does super cooled. It's designed to run that way with the transistors in the "optimal" operating area which draws full current. Same for tubes their operating parameters occur at a certain temp. Cooling probably won't harm anything, but most likely will limit performance.

There are plenty of other designs out there that run cool. IMO, they don't sound as good, but if heat mitigation is a top priority then that's how it is.

If you are cooling to prevent "over" heating then I could see. Like I said most class A amps go into great detail about how to place them so they don't over heat.

H9

pearsall001 · August 2025

Definitely gonna pass on a tube amp for my combo HT / 2 channel system.
Will revisit Class D amps. I had a pair of mono blocks a good 10 yrs ago & I really liked them. The technology has advanced leaps & bounds since then so worth a revisit.

nooshinjohn · August 2025

pearsall001 wrote: »

Definitely gonna pass on a tube amp for my combo HT / 2 channel system.
Will revisit Class D amps. I had a pair of mono blocks a good 10 yrs ago & I really liked them. The technology has advanced leaps & bounds since then so worth a revisit.

Arcam class G will get you the sound you are looking for. Heavily biased into class A to start with...
The do run hot however.

heiney9 · August 2025

If your looking for tube flavor with all the great attributes of SS, then Pass gear should be what you're looking at. Yes,Class A runs hot to very hot.

When I say tube "flavor" I mean they have some characteristics of tube amp sound w/o the hassle of running tubes. DO they sound and act exactly like tubes? No.

I've heard on this very forum that Pass gear has a "house" sound. With all due respect, they do NOT. Many of his designs are different from each other so there's no way to have a "house sound"

The XA25, XA30.8, X150.8, Int 60, Aleph 0, Aleph 30, etc all sound different because they use different topologies. Is there an underlying philosophy, sure. Think of them like Ferrari. All Ferrari models are different, but underneath there is a philosophy that ties them all together.

They should atleast be in the mix if you're serious about getting a more tube like sound from your amp.

Just my .02c

H9

pearsall001 · August 2025

The Arcam PA240 looks interesting especially when it claims that the first 50watts are class A.
I've looked at many Pass Labs items over the years but their pricing was always a stumpling block for me.

heiney9 · August 2025

pearsall001 wrote: »

The Arcam PA240 looks interesting especially when it claims that the first 50watts are class A.
I've looked at many Pass Labs items over the years but their pricing was always a stumpling block for me.

No way its 50 watts of class A. Not enough heat sinking. They are playing tricks in the marketing department.

My XA25 is 25 watts Class A and even with it's ample heat sinks it gets pretty hot to the touch.

For a few hundred more you could buy a used XA25.

H9

pearsall001 · August 2025

heiney9 wrote: »

pearsall001 wrote: »

The Arcam PA240 looks interesting especially when it claims that the first 50watts are class A.
I've looked at many Pass Labs items over the years but their pricing was always a stumpling block for me.

No way its 50 watts of class A. Not enough heat sinking. They are playing tricks in the marketing department.

My XA25 is 25 watts Class A and even with it's ample heat sinks it gets pretty hot to the touch.

For a few hundred more you could buy a used XA25.

H9

I wonder if being class G has something to do with it. Apparently they rival class D in how cool they run & heat sinks aren't a major concern. I'm with you though 50 class G watts does seem like a lot.

I think we're so used to class A / AB amps with massive heavy heat sinks being a major part of their design that we can't wrap our heads around these new designs that don't require the same cooling needs.

Unknown · August 2025

This content has been removed.

mhardy6647 · August 2025

Class G uses a dual rail topology. It's been around since at least the mid 1970s.

It is pretty simple and comparatively low-tech. Not really any more efficient than Class AB, other than the ability to transiently double output power by switching to the higher DC rail voltage(s).
EDIT: OK, Audio magazine said it's quite efficient!

Finally, there is a Class G amplifier
from Hitachi which is designed to op-
erate more efficiently over more of
the operating range. It boasts an effi-
ciency of 90 per cent or better. In-
stead of using two transistors, as is the
case with Class B and D amplifiers, the
Class G uses four. The smaller pair has
relatively low power dissipation and
output, but whenever a higher ampli-
tude signal comes along, a sensing
diode switches on the larger pair of
transistors. Consequently, each pair of
transistors operates in close to its most
efficient operating area, and the over-
all circuit can be smaller and lighter.

source: https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1977-09.pdf#search="class g"

mhardy6647 · August 2025

https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/70s/Audio-1978-11.pdf#search="class g"

Viking64 · August 2025

mhardy6647 wrote: »

Class G uses a dual rail topology. It's been around since at least the mid 1970s.

We had a dual rail Hitachi back in the 70s.

invalid · August 2025

heiney9 wrote: »

pearsall001 wrote: »

The Arcam PA240 looks interesting especially when it claims that the first 50watts are class A.
I've looked at many Pass Labs items over the years but their pricing was always a stumpling block for me.

No way its 50 watts of class A. Not enough heat sinking. They are playing tricks in the marketing department.

My XA25 is 25 watts Class A and even with it's ample heat sinks it gets pretty hot to the touch.

For a few hundred more you could buy a used XA25.

H9

t's not just the lack of heat sinking, it's also the 90 watts of idle current that makes it suspect.

heiney9 · August 2025

pearsall001 wrote: »

heiney9 wrote: »

pearsall001 wrote: »

The Arcam PA240 looks interesting especially when it claims that the first 50watts are class A.
I've looked at many Pass Labs items over the years but their pricing was always a stumpling block for me.

No way its 50 watts of class A. Not enough heat sinking. They are playing tricks in the marketing department.

My XA25 is 25 watts Class A and even with it's ample heat sinks it gets pretty hot to the touch.

For a few hundred more you could buy a used XA25.

H9

I wonder if being class G has something to do with it. Apparently they rival class D in how cool they run & heat sinks aren't a major concern. I'm with you though 50 class G watts does seem like a lot.

I think we're so used to class A / AB amps with massive heavy heat sinks being a major part of their design that we can't wrap our heads around these new designs that don't require the same cooling needs.

I have not heard the Arcam, but the trick topologies of the past are usually just that "tricks". It's all about trade-offs. Not saying it doesn't sound good.

I have always stated that after I heard my first single ended class A amp, that was it for me. No other amp will do for me personally in my main rig. I am willing to put up with the heat and extra electricity bill.

This has only again been reinforced by the little Pass ACA amp. So simple, such great sound from a low powered single ended class A amplifier. I've been comparing to my Keces E40 and Schiit Gjallahorn amps in the office rig. the ACA wins.

Sorry for taking it a bit off topic. We all like what we like for various reasons. There is no "right" answer really. Maybe more right or less right....lol

All I was saying is if you want some tube character in your amplification w/o actually running tubes; Pass gear and single ended class A in general has the some of those characteristics.

I wish you were closer Phil. I'd loan you my Pass Aleph 30 just so you could get a feel for it. I still have it. Not sure I want to risk shipping there and back for a demo. Not so much for a sale, but just to get your ears on it.

H9

heiney9 · August 2025

invalid wrote: »

heiney9 wrote: »

pearsall001 wrote: »

The Arcam PA240 looks interesting especially when it claims that the first 50watts are class A.
I've looked at many Pass Labs items over the years but their pricing was always a stumpling block for me.

No way its 50 watts of class A. Not enough heat sinking. They are playing tricks in the marketing department.

My XA25 is 25 watts Class A and even with it's ample heat sinks it gets pretty hot to the touch.

For a few hundred more you could buy a used XA25.

H9

t's not just the lack of heat sinking, it's also the 90 watts of idle current that makes it suspect.

Yes, I didn't even mention that. I think Phil got that information from an on-line personal sales ad. 90 watts. My Keces desktop integratred runs class A to a point and it idles at 180 watts.

My XA 25 idles at 240 watts to give 25 watts class A.

Not trying to crap on the amp or the brand at all. Most marketing departments stretch the truth as much as they can.

H9

pearsall001 · August 2025

heiney9 wrote: »

pearsall001 wrote: »

heiney9 wrote: »

pearsall001 wrote: »

The Arcam PA240 looks interesting especially when it claims that the first 50watts are class A.
I've looked at many Pass Labs items over the years but their pricing was always a stumpling block for me.

No way its 50 watts of class A. Not enough heat sinking. They are playing tricks in the marketing department.

My XA25 is 25 watts Class A and even with it's ample heat sinks it gets pretty hot to the touch.

For a few hundred more you could buy a used XA25.

H9

I wonder if being class G has something to do with it. Apparently they rival class D in how cool they run & heat sinks aren't a major concern. I'm with you though 50 class G watts does seem like a lot.

I think we're so used to class A / AB amps with massive heavy heat sinks being a major part of their design that we can't wrap our heads around these new designs that don't require the same cooling needs.

I have not heard the Arcam, but the trick topologies of the past are usually just that "tricks". It's all about trade-offs. Not saying it doesn't sound good.

I have always stated that after I heard my first single ended class A amp, that was it for me. No other amp will do for me personally in my main rig. I am willing to put up with the heat and extra electricity bill.

This has only again been reinforced by the little Pass ACA amp. So simple, such great sound from a low powered single ended class A amplifier. I've been comparing to my Keces E40 and Schiit Gjallahorn amps in the office rig. the ACA wins.

Sorry for taking it a bit off topic. We all like what we like for various reasons. There is no "right" answer really. Maybe more right or less right....lol

All I was saying is if you want some tube character in your amplification w/o actually running tubes; Pass gear and single ended class A in general has the some of those characteristics.

I wish you were closer Phil. I'd loan you my Pass Aleph 30 just so you could get a feel for it. I still have it. Not sure I want to risk shipping there and back for a demo. Not so much for a sale, but just to get your ears on it.

H9

Very nice offer there Brock but I'm with you on shipping nowadays. I would feel terrible if anything were to happen. Just not worth the risk.

My real concern is how well a tube amp let alone a Class A amp would hold up in my HT. There is definitely a lot of demand there.

Now that I'm retired my HT gets more use than 2 channel listening. I still enjoy my 2 channel but HT has top billing now. That's quite a few hours during the day/night that the amp is on pulling double duty.

I know most of you guys here concentrate on 2 channel over HT (some have no interest in HT at all) but my needs have shifted in the opposite direction. Maybe it's time for me to turn in my audiophile card. Lol!!!

invalid · August 2025

If you go the route of a class A solid state amplifier, you could get one that has a switch to change from class A operation to class A/B operation. I know Plinius makes amps like this, as I'm sure there are others as well.

heiney9 · August 2025

Phil, I will leave you this quote from a Positive Feedback review. Should alleviate any concerns about being up for the task of HT.

In routine listening sessions the Pass Labs sounded a lot more powerful than those numbers imply.

For example, the XA25 easily provided the full spectrum of extreme dynamic performance, whether it was on the subtle gradations of pianississimo, or the "hang onto your hat" blasts of fortississimo, even at live-like sound pressure levels (SPLs).

To accomplish that kind of a live-like level of dynamics at live music volume levels, without strain, normally requires sensitive loudspeakers combined with relatively powerful amplifiers, or loudspeakers of average sensitivity with astronomically powerful amplification.

As part of the feature review I am writing about the Pass Labs XA25 stereo amplifier for Positive Feedback, I've been asking Nelson a few questions here and there about the XA25.

These questions are partly because I'm interested in what makes it tick from a technology standpoint so I can give you a thorough description of it for the review, but also because its high level of performance simply defies what I would normally consider possible from a 25 watt per channel stereo amplifier (into 8 Ohms).

In a nutshell, the Pass Labs XA25 stereo amplifier is extremely transparent, resolving, and distortion free from the highest highs to the lowest lows, and it sounds incredibly powerful in contradiction to its nominal power rating of 25 watts. The XA25 can also provide incredible bass slam when it's in the music, and yet it possesses all of the organic musicality and visuospatial characteristics that I would normally associate with directly-heated singled-ended triodes (DH-SETs).

I use the XA25 as example because I speak about what I know. As far as integrating into an HT, not sure how that would work or if the cost per use ratio is way too high since you do little 2ch listening these days. In fact if you are 75% HT, why are we even discussing tube amps.....lol

It's fun to discuss audio even if in the end it's not practical for your use these days. I admit, my 2ch vets used maybe 2-3 times a month (Fall and Winter more). I spend most of my time listening to the office rig. Even that is more rare these days.

But, for me, knowing I have it when I want to enjoy it is worth the cost. Even if those moments are fewer.

H9

pearsall001 · August 2025

I use the XA25 as example because I speak about what I know. As far as integrating into an HT, not sure how that would work or if the cost per use ratio is way too high since you do little 2ch listening these days. In fact if you are 75% HT, why are we even discussing tube amps.....lol

Even though my 2 channel listening has taken a back seat to my HT sessions I still thought it would be interesting to see what a tube amp (never thought about a Class A amp at all) brought to the table for my 2 channel listening even thought it has dropped off. I'll have to look into that Pass XA25...it sounds like it can over perform in both even though it is only 25 watts. Thanks for the info.

treitz3 · August 2025

Watts are overrated.

Tom

daddyjt · August 2025

treitz3 wrote: »

Watts are overrated.

Tom

Too true. I just repaired a Mark Levinson 331, and I’ve been A/B testing it against my Carver Silver 9t pair. The carvers put out a solid 600 wpc, and the Levinson is rated at 100 wpc. There is zero difference in either of these in their ability to drive my NHT 3.3 speakers (which are somewhat difficult to drive). There are MANY differences in the amps otherwise, but you would never guess there is a power disparity between them by listening.

mhardy6647 · August 2025

3 per channel on the big boy hifi at my house. Thermionic watts they are, too... of course.
Not home theater, though.

SeleniumFalcon · August 2025

There's always James Watt:

VR3 · August 2025

Levinson has substantial current in their designs, great amps

pearsall001 · August 2025

Now I'm thinking maybe a tube DAC might be an option to change things up a bit with my 2 channel & leave the HT as is.

pearsall001 · August 2025

Deleted User wrote: »

Phil is always wanting to try something different. I love it!

You know I'm going to say be sure and check out LampizatOr options. One of the top five changes I've made to my rig. Of course, it all started out by seeing what DACs could do with the Geshelli Labs J2 DAC I got from you!

Those Lampo's are some pricey buggers! I've looked at a few:
ANK
LAB 12
FEZZ Audio
LTA AERO
HDT Orchid
PrimaLuna EVO 100 Tube DAC
Still just looking.

invalid · August 2025

Deleted User wrote: »

Phil is always wanting to try something different. I love it!

You know I'm going to say be sure and check out LampizatOr options. One of the top five changes I've made to my rig. Of course, it all started out by seeing what DACs could do with the Geshelli Labs J2 DAC I got from you!

How much rectifier rolling have you done with the Lampizator DAC?

VR3 · August 2025

Abbas should be in that list... One of the best sounding dacs I've heard regardless of price

TroyD · August 2025

So, I’ve had a few tube amps over the years….Conrad Johnson and Heathkit mostly. Tubes are expensive but, really, unless you are into rolling tubes…..a set of power tubes will last a long time. I had one bad tube….which was a Chinesium issue and replaced under warranty. Biasing is not difficult and not something that is a constant task……

So, why I don’t still use tube amps……I lucked into the MF gear and moved on from the Quads.

Bass, depending on amp/speaker may be a little softer, less tight that you are used to but I would have zero issues going back to tubes…..but, I am also not as persnickety about details as Tom is, which is not a criticism at all….but tube amps aren’t for everyone

heiney9 · August 2025

pearsall001 wrote: »

Now I'm thinking maybe a tube DAC might be an option to change things up a bit with my 2 channel & leave the HT as is.

IMO, tube dacs in general add very little tube flavor. I have 2 of them and experience with others. Granted they are implemented more as a buffer than gain stages. Really, IMO opinion tube pre amps really are the best solution.

Also if you're not willing to go a little bit down the tube rabbit hole and only run stock tubes, don't bother. I'm not saying you have be like me and track down every known tube, but the most fun with tubes is experiencing some of the rolling options. Tubes can transform a system.

Again just my .02c

H9

Thinking about trying a tube amp. Thoughts.

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