Why are "Class D" amplifiers expensive?

**pingu** · 02-14-2013, 01:48 PM

Originally Posted by HighSpeedSpoon

A DI box will help, but I was surprised at how well the connection worked without one. I played two humbucker guitars both ways. They worked "fine enough" straight in but the response was clearer via a DI box. And "fine enough" for me may not be fine enough for you if you are playing an acoustic or doing vocals. You will lose some definition and especially trebles if you go straight in. If it matters, good DI boxes are not that expensive. As I write this, the top-selling DI box on Amazon gets 4.5 out of 5 stars based on 44 ratings and costs less than $15, and even good passive ones can be had for around $30 (see here). BTW, the Alto site could definitely be clearer, but fyi I eventually discovered the input impedance hiding in their downloadable spec sheet (15 KOhms).

Good luck.

Thanks Spoon , thats interesting ............
Kind of on topic , class D amps are cheap , or can be , I bought one designed for Car Hi-Fi 150 +150 watts
treble and Bass controls for £15 with PSU ...... and it works great with my PC output powering HI-Fi speakers

These reasonably priced Class D powered speakers like yours should work great for clean Jazz Guit amplification
600 watts into a 10" and light too , the only issues are EQ and input Z .......

Its interesting that plugging straight in works OK (with the provisos you mentioned)
15Kohms is low for a guitar amp i/p Z (more like 500 Kohm to 1 Mohm typically)

do you get enough volume going straight in Spoon ?

**HighSpeedSpoon** · 02-14-2013, 03:34 PM

Originally Posted by pingu

... Its interesting that plugging straight in works OK (with the provisos you mentioned)
15Kohms is low for a guitar amp i/p Z (more like 500 Kohm to 1 Mohm typically)

do you get enough volume going straight in Spoon ?

I hope you don't mind that I am going to answer your question indirectly.

First off, impedance matching is an important issue, but I hope you won't let it be like the tail wagging the dog. There are many solutions, and I would encourage you to consider them - either a DI, a preamp with a Lo-Z out, or even a small pedal like my G3X. The cost, weight, space, and complexity of these options can be appealing, and you have the option of starting with a simple, cheap DI and moving to a pedal later. And FWIW, the competing speakers I considered - the Behringer Eurolive B210D (now $199) and QSC K10 ($799) - have roughly the same input impedances - nothing really designed for electric guitar.

Keeping in mind that I have not played out with this rig, the short answer to your question is that you get the volume straight into the Alto but not the same quality. I would expect the same going straight into the Behringer or the QSC. But I am already spoiled by my G3, and I would not really be happy going back.

Plugging in via my G3X (which has a low Z out), I get more volume and at least as much definition and clarity as I get straight into my 51 pound, 100 watt California Blonde, which has a hi-Z inputs, a 12" bass reflex speaker, and a tweeter. Also, the G3 does more of what I need than even the high-priced Radial JDI that I auditioned: The very precise and flexible EQ on the G3X, the choice and configuration of the amp model, and the choice of cabinet model all make huge differences in the sound. These things may not matter if you are playing a truly acoustic guitar, in which case a DI may be all you need, but they really work for me.

Well, I hope that helps. BTW, can you audition an Alto or a competing product?

**Jim Soloway** · 02-14-2013, 03:57 PM

Originally Posted by Silentwiz

Jim are you using that carvin bass combo without any effects? As a standalone unit, it'd make an incredible grab and go. A review would be appreciated.

I ended up sending it back and going with the VHT Special Six to fill that function. The Carvin just seem to PA-like for my taste.

**Jim Soloway** · 02-14-2013, 04:21 PM

Here's an alternative that will be available in about a month. Street is going to be about $330. It's 9 X 4 X 2 inches, weighs 1.2 lbs and puts out 80 watts per side in stereo and 160 bridgead to mono.

http://www.isptechnologies.com/portf...lth-power-amp/

**HighSpeedSpoon** · 02-14-2013, 05:13 PM

That might play really well with your 8" Raezer's Edge. But I'm not sure what the advantage is for a clean tone, and it would be interesting to see, among other things, if the "excellent sonic and saturated clipping performance" scales down to low volumes.

**Jim Soloway** · 02-14-2013, 06:10 PM

Originally Posted by HighSpeedSpoon

That might play really well with your 8" Raezer's Edge. But I'm not sure what the advantage is for a clean tone, and it would be interesting to see, among other things, if the "excellent sonic and saturated clipping performance" scales down to low volumes.

The advantage is size and weight and after talking with their tech this morning, I suspect that the "excellent sonic and saturated clipping performance" refers to their pre-amp.

**Jonathan0996** · 02-14-2013, 06:19 PM

Originally Posted by GuyBoden

Unfortunately, some folk will always think Black and White TV was best, it's probably due to the past memories of their TV favorites.
Guy

I say color TV is a fad.

**HighSpeedSpoon** · 02-14-2013, 07:04 PM

Originally Posted by Jim Soloway

The advantage is size and weight and after talking with their tech this morning, I suspect that the "excellent sonic and saturated clipping performance" refers to their pre-amp.

Jim,

I did not mean to be difficult, and I thought it was obvious that size and weight are advantages. But the ISP web page said the amp is based on an "analog class A/B amplifier design for excellent sonic and saturated clipping performance". "A/B" refers to the power section in guitar amps, so my question was meant to get at whether or not they claim to replicate the touch sensitivity and tube breakup characteristics of tube amps, and whether or not this is supposed to be the case at scalable volumes, versus at some "sweet spot". This amp may be great when it hits the street, but knowing about your conversation with their tech, I am still wondering what is special about this amp (versus say, lightweight class D amps with a modeler) and how it relates to the class A/B and excellent sonic performance. They talk about their switched mode power supply, and I thought only class D, E, and F amps were switched mode.

**Jim Soloway** · 02-14-2013, 07:21 PM

Originally Posted by HighSpeedSpoon

Jim,

I did not mean to be difficult, and I thought it was obvious that size and weight are advantages. But the ISP web page said the amp is based on an "analog class A/B amplifier design for excellent sonic and saturated clipping performance". "A/B" refers to the power section in guitar amps, so my question was meant to get at whether or not they claim to replicate the touch sensitivity and tube breakup characteristics of tube amps, and whether or not this is supposed to be the case at scalable volumes, versus at some "sweet spot". This amp may be great when it hits the street, but knowing about your conversation with their tech, I am still wondering what is special about this amp (versus say, lightweight class D amps with a modeler) and how it relates to the class A/B and excellent sonic performance.

The only problem I have with my Carvin class D amp is the form factor. It's light weight, sounds great and powers my RE cab beautifully. But I'd rather it be something small to sit on the cab than have to deal with even a small, shallow depth rack case. So really, I'm at a point where the size and weight are the only benefit left. This is the one and only reason I wish I had made it to NAMM this year. I'd like to have heard this in person. I'm going to try to talk them into letting me be one of the final testers before it ships commercially next month and I'll let you know then whether it fills the niche or not. in the mean time, I'm probably going to try that little Dayton Audio class D amp. I just wish the channels were bridgeable.

**HighSpeedSpoon** · 02-14-2013, 08:19 PM

Thanks for that; makes perfect sense.

**Jim Soloway** · 02-15-2013, 09:51 PM

Originally Posted by dingusmingus

Hi Jim,
Have you ever looked at these?
Dayton Audio DTA-100a Class-T Digital Amplifier 50 WPC Provides Power To Computer Speakers, Bookshelf Speakers, Headphones, And More! 300-383

It's a cheap 50 Watt-per-channel class D stereo amplifier. Tiny little thing. I use it to power stereo speakers and it does just fine. Not sure how many watts you need, but it might be worth looking into if you haven't already.

EDIT: Actually, it doesn't look like it can be bridged, so probably not right for you.

I checked with Dayton and while it's not bridgeable, it can be run in mono into an 8 ohm cab. I figured for that price I'd give it a shot so I ordered one from Parts Express. I'll let you know how it works with my Raezer's Edge cab next week. It would be very cool indeed if I could get away with a power amp that size.

**GuyBoden** · 02-21-2013, 09:00 AM

Originally Posted by Jim Soloway

I checked with Dayton and while it's not bridgeable, it can be run in mono into an 8 ohm cab.

Jim, I'd be very interested in how you progress using the "T Class" amp in mono?

I believe that the Tripath Integrated Circuits are "D Class", but named "T Class" after the company name Tripath.

I was interested in the Tripath, because they are very small, but I thought that they are usually 11watt in 4ohm or 6watt into 8ohm without clipping giving audio quality.

Thanks for the info.
Guy

**Jim Soloway** · 02-21-2013, 11:28 AM

Hopefully I'll have it today or tomorrow. I've got all of the cables and ready to give it a go. I have great hopes for this. An amp this size could be something of a game changer for me if it works, especially coming just as I'm starting to get back to playing out a lot.

**HighSpeedSpoon** · 02-21-2013, 12:13 PM

Originally Posted by GuyBoden

... I believe that the Tripath Integrated Circuits are "D Class", but named "T Class" after the company name Tripath. ...

This is correct (see the wiki page).

Jim: Good luck on NAD.

**Jim Soloway** · 02-21-2013, 05:13 PM

Originally Posted by HighSpeedSpoon

This is correct (see the wiki page).

Jim: Good luck on NAD.

It's here and it's a complete win! 2-1/8" H x 3-3/8" W x 5-1/2" D and 2.75 lbs and runs of a laptop style power supply. (The power supply is actually bigger than the amp). Unlike the EH power amps, it's silent. It's giving me perhaps a tiny bit lower maximum volume than my Carvin power amps but running through my Raezer's Edge cab, it sounds almost identical and along with the power supply, it will drop in my gig bag. Cabling is a bit unusual but not really hard to get around and the idea of being able to run a passive system without a rack for the amp is so cool. I'm seriously impressed (and more than a bit excited).

**Silentwiz** · 02-21-2013, 08:33 PM

Need pictures!

**GuyBoden** · 02-22-2013, 12:05 PM

Originally Posted by Jim Soloway

It's here and it's a complete win! 2-1/8" H x 3-3/8" W x 5-1/2" D and 2.75 lbs and runs of a laptop style power supply. (The power supply is actually bigger than the amp). Unlike the EH power amps, it's silent. It's giving me perhaps a tiny bit lower maximum volume than my Carvin power amps but running through my Raezer's Edge cab, it sounds almost identical and along with the power supply, it will drop in my gig bag. Cabling is a bit unusual but not really hard to get around and the idea of being able to run a passive system without a rack for the amp is so cool. I'm seriously impressed (and more than a bit excited).

Well done Jim, cabling must be a bit unusual, but no real problem.

Why are "Class D" amplifiers expensive?-inputs-amp-back-bmp

**Jim Soloway** · 02-22-2013, 02:13 PM

Not only is it no problem, but Guitar Center's web site is blowing out the exact 10' banana plug to 1/4" cable in a two pack for $10. That was a nice coincidence. And playing through it again this morning, I'm really thrilled with the results.

And here are some photos. I was trying to think of something to put the size in perspective and it occurred to me that what could be better at than than just photographing it on a guitar?