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Item: Pure Class A Power Amplifier
Price Range: 3.5k
Item Condition: New or Used
Extra Info:

I'm looking for class A Power Amplifier. Please pm you offers. Thanks

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I'm sure I saw one in the for sale section not long ago.

May well be gone though.

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9 minutes ago, LogicprObe said:

 

I'm sure I saw one in the for sale section not long ago.

May well be gone though.

Which one?

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Nice simple amp. I have the M2x, 25 watts all class A.

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It's a good idea to look at your system prior to getting a First Watt. Speaker sensitivity and system gain and on the flipside of this, how loud you like to listen to music are the primary considerations when short listing a FW amp. Some First Watt gear is designed with specific speaker matching in mind as well so have a look at the product page linked to below.

That's not meant to be a criticism of FW by the way. Just stating was Nelson Pass points out himself on his site; https://www.firstwatt.com/prod.html

 

Mark

 

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22 hours ago, full_dp said:

Item: Pure Class A Power Amplifier
Price Range: 3.5k
Item Condition: New or Used
Extra Info:

I'm looking for class A Power Amplifier. Please pm you offers. Thanks

Please don't forget to report your post as FOUND when possible. (You can now delete this text).

 

2 Qus:

  • what power are you looking for?  (Class A ranges from 5w ... to 50w!  Into 8 ohms.)
  • are your spkrs 8 ohm ... or 4 ohm?

Andy

 

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14 minutes ago, andyr said:

 

2 Qus:

  • what power are you looking for?  (Class A ranges from 5w ... to 50w!  Into 8 ohms.)
  • are your spkrs 8 ohm ... or 4 ohm?

Andy

 

Hi Andy, Im looking for 35w-50w into 8 ohms bookshelf speakers. Thanks

 

25 minutes ago, deepthought said:

It's a good idea to look at your system prior to getting a First Watt. Speaker sensitivity and system gain and on the flipside of this, how loud you like to listen to music are the primary considerations when short listing a FW amp. Some First Watt gear is designed with specific speaker matching in mind as well so have a look at the product page linked to below.

That's not meant to be a criticism of FW by the way. Just stating was Nelson Pass points out himself on his site; https://www.firstwatt.com/prod.html

 

Mark

 

Thanks for this tips and the link Mark, im reading it now. :)

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24 minutes ago, deepthought said:

Or just be done with it and get a Pass Labs XA25............ :sorry:

Its hard to find any preowned pass labs :(

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3 minutes ago, full_dp said:

Its hard to find any preowned pass labs :(

Yes and the ones floating around generally hold their value quite well too.

 

7 minutes ago, full_dp said:

Hi Andy, Im looking for 35w-50w into 8 ohms bookshelf speakers. Thanks

 

Thanks for this tips and the link Mark, im reading it now. :)

Set aside quite a bit of time. Fun reading though.

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Just now, full_dp said:

Its hard to find any preowned pass labs :(

And near impossible for your budget unless it was ancient. First Watt F5 turbo would match your desires and could easily come in under budget. Getting someone to build for you can be a headache too.

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54 minutes ago, Gryffles said:

Getting someone to build for you can be a headache too

Why would that be?

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21 hours ago, deepthought said:

It's a good idea to look at your system prior to getting a First Watt. Speaker sensitivity and system gain and on the flipside of this, how loud you like to listen to music are the primary considerations when short listing a FW amp. Some First Watt gear is designed with specific speaker matching in mind as well so have a look at the product page linked to below.

That's not meant to be a criticism of FW by the way. Just stating was Nelson Pass points out himself on his site; https://www.firstwatt.com/prod.html

 

Mark

 

 

Agreed 100%. 

As an F7 owner, 20 watts does require a speaker with an above average sensitivity. 

 

Atm I use some 3 ways, which have a sensitivity of circa 94db.

 

I sit near field, and listen typically around 75-90db. 

I have heaps of system gain and volume left. 

 

The system easily hits 100db @ listening position, which is far more than I need.  

 

What I have enjoyed most about the F7 apart from its glorious sound, is the amp is dead silent.

It has absolutely no audible hiss, or operational noise, somewhat helped by the amps low output gain @ 14db. 

It would make for an awesome higher frequency amplifier in a multiway active setup. 

 

Edited by Grizaudio
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If you're after something that has similar qualities as the passlabs, I have a threshold SA3.9e im looking to offload. All within your price range and power requirements. Hit me up with a msg if you're interested. 

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On 23/01/2021 at 9:57 PM, Gryffles said:

Getting someone to build for you can be a headache too.

 

On 23/01/2021 at 10:51 PM, Willmax said:

Why would that be?

 

Because there's a several-hundred page thread on diyAudio about building one - with many people's input on problems and solutions ... which makes it not straight forward.  :lol:

 

I bought the boards - but then gave up as I suspected I would never be able to get a successful result and built the Alpha 'Nirvana' instead.  Also on diyAudio - 40w into 8 ohms ... but doesn't handle 4 ohms very well.  :(  (I built the 4 ohm version - which is stable into 2 ohms.)

 

On 24/01/2021 at 6:50 PM, Grizaudio said:

@mwhouston could help you. 

 

Great suggestion!  If he is, @full_dp ... remember, I have the boards.  :)

 

Andy

 

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Can I ask why full class A in the first place? They can sound very good but....... any class A amp over 15W requires massive power supply, heatsinks, subsequent limited life of components due to the heat and a dent in your power bill!

Have a chat with Hugh Dean, a great sounding class AB amp in a range of output wattages and reasonably priced

https://www.aksaonline.com/contact/contact.html

 

regards Ian

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My Class A amp only draws 160 watts from the mains power. Yes, it gets hot, around 55C. and is big but only weighs 16Kg.

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On 24/01/2021 at 6:02 PM, Grizaudio said:

 

Agreed 100%. 

As an F7 owner, 20 watts does require a speaker with an above average sensitivity. 

 

Atm I use some 3 ways, which have a sensitivity of circa 94db.

 

I sit near field, and listen typically around 75-90db. 

I have heaps of system gain and volume left. 

 

The system easily hits 100db @ listening position, which is far more than I need.  

 

What I have enjoyed most about the F7 apart from its glorious sound, is the amp is dead silent.

It has absolutely no audible hiss, or operational noise, somewhat helped by the amps low output gain @ 14db. 

It would make for an awesome higher frequency amplifier in a multiway active setup. 

 

 

I hope to own a F7 copy one of these days.... That said I'll fit a resistor based attenuator on the inputs so I can adjust input levels lower. 20WPC is about double what my speakers need for useable levels  :)

 

I'd love a SIT-3 but $8,800 just seems a bit much though there are certainly times I've thought about it.  I don't like the idea of drilling a hole in the back of an $8,800 bit of kit to install the pot though. I have read that the SIT-3 and F7 are similar sounding amps, though the SIT3 foregoes a little transparency for an overall richer sound.

 

If I'm smart though I'll stop once I've my pimped Aleph-M.... Wish I were smart ;)

Edited by MattyW
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2 hours ago, Ian McP said:

Can I ask why full class A in the first place? They can sound very good but.......

 

C'mon, Ian - as I'm sure you know ... Class A offers that 'special something '!  :)  (If you can put up with their generally low power ratings.)

 

Quote

any class A amp over 15W requires massive power supply, heatsinks, subsequent limited life of components due to the heat and a dent in your power bill!

 

Massive heat - yes ... but you don't necessarily need massive heatsinks if you take the 'active approach'.  IE. the output devices are clamped to a finned CPU cooler which has a 12v Noctua fan blowing through the fins.

 

But high power consumption - yes.  :(  Interestingly - did you know that a Class A amp draws the same power whether it's driving the speakers loudly ... or softly!  If its driving the spkrs loudly ... more power goes to the spkrs (and less into the heatsinks).  If the music is soft ... it's the other way round!  :o

 

Quote

Have a chat with Hugh Dean, a great sounding class AB amp in a range of output wattages and reasonably priced

https://www.aksaonline.com/contact/contact.html

 

regards Ian

 

Great-sounding Class AB amps indeed, Ian - but Hugh has also designed a 40w (into 8 ohms) Class A amp which is released on diyAudio (the "Alpha Nirvana") and will be releasing his own (better-sounding!) commercial - ie. ready made version, also 40w into 8 ohms - in the not too distant future ... the "Omega"!

 

Unfortunately, full_dp:

 

On 22/01/2021 at 11:01 PM, full_dp said:

Item: Pure Class A Power Amplifier
Price Range: 3.5k
Item Condition: New or Used
Extra Info:

I'm looking for class A Power Amplifier. Please pm you offers. Thanks

 

... I believe the 'Omega' will be more than your budget.  :(

 

Andy

 

Edited by andyr
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2 hours ago, MattyW said:

 

I hope to own a F7 copy one of these days.... That said I'll fit a resistor based attenuator on the inputs so I can adjust input levels lower. 20WPC is about double what my speakers need for useable levels  :)

 

I'd love a SIT-3 but $8,800 just seems a bit much though there are certainly times I've thought about it.  I don't like the idea of drilling a hole in the back of an $8,800 bit of kit to install the pot though. I have read that the SIT-3 and F7 are similar sounding amps, though the SIT3 foregoes a little transparency for an overall richer sound.

 

If I'm smart though I'll stop once I've my pimped Aleph-M.... Wish I were smart ;)

 

@MattyW the F7 really is a great amp.

The midrange & highs are lovely. Smooth, but detailed, and holographic. I have heard better bass, but its class A 😂, its decent enough.  

I too would love to hear the Firstwatt J2, and SIT options, but they are pricy. I managed to grab my F7 on SNA for a great price, they pop up every now and again.  

 

Can I ask, why would you want to insert an attenuator directly into the amplifier?

Would it not be easier to use a decent quality external passive attenuator (Goldpoint, Schitt, etc), or active/passive preamp? 

 

You might not know, but the Firstwatt F7 has a very low output gain = 14.5db.

Combined with an input sensitivity of 2.7volts, you need to select an appropriate front end if max power is required.

 

image.png.31c3edcb6916dd21e04b4543dbef0cc7.png

 

My RME ADI2 Dac will drive about 3.5v rms via RCA, so theoretically max output is achieve at -2dBu on the volume adjustment. 

+13dBU via RCA, +19dBu via XLR (So fairly high for consumer gear), but great for low gain amplifiers, Firstwatt, Purifi etc.   

 

Here is a helpful Volts, dBu conversion calculator:

http://www.sengpielaudio.com/calculator-db-volt.htm

 

 

 

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59 minutes ago, Grizaudio said:

 

@MattyW the F7 really is a great amp.

The midrange & highs are lovely. Smooth, but detailed, and holographic. I have heard better bass, but its class A 😂, its decent enough.  

I too would love to hear the Firstwatt J2, and SIT options, but they are pricy. I managed to grab my F7 on SNA for a great price, they pop up every now and again.  

 

Can I ask, why would you want to insert an attenuator directly into the amplifier?

Would it not be easier to use a decent quality external passive attenuator (Goldpoint, Schitt, etc), or active/passive preamp? 

 

You might not know, but the Firstwatt F7 has a very low output gain = 14.5db.

Combined with an input sensitivity of 2.7volts, you need to select an appropriate front end if max power is required.

 

image.png.31c3edcb6916dd21e04b4543dbef0cc7.png

 

My RME ADI2 Dac will drive about 3.5v rms via RCA, so theoretically max output is achieve at -2dBu on the volume adjustment. 

+13dBU via RCA, +19dBu via XLR (So fairly high for consumer gear), but great for low gain amplifiers, Firstwatt, Purifi etc.   

 

Here is a helpful Volts, dBu conversion calculator:

http://www.sengpielaudio.com/calculator-db-volt.htm

 

 

 

 

I already have a quality external passive.  Thing is its still not useful if the first few clicks go up in volume too much.  My fullrange and helper tweeters average efficiency is 101db so a 10WPC amp is as high as I can usably go. The only way to use a higher powered power amp, is to further attenuate the signal before it gets to the amp.

 

I can very easily achieve high volumes with a 5WPC Pass Amp Camp Amp. The only reason I'm attracted to these more powerful amps is they're much newer designs and amongst the very best Nelson Pass has created. They are too high wattage for my purposes though.

 

The reason I can run a passive pre is simply because my Abbas Audio DAC and phono stage have a very high output level.  :)

Edited by MattyW
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5 hours ago, Ian McP said:

Can I ask why full class A in the first place? They can sound very good but....... any class A amp over 15W requires massive power supply, heatsinks, subsequent limited life of components due to the heat and a dent in your power bill!

Have a chat with Hugh Dean, a great sounding class AB amp in a range of output wattages and reasonably priced

https://www.aksaonline.com/contact/contact.html

 

regards Ian

The XA25 uses about 200w at idle. . That's about the same as my flat screen TV. It puts out 90 watts RMS in Class B and 25watts in Class A. It runs at 55C, the Mosfets are rated to run safely at up to 150C. Pass Labs still has many of its original amp's in service since it started in 1991 and many of his previous Class A designs are happily running. The main mode of failure is the capacitors which usually last around 20 years before needing to be replaced, as would be the case is a Class A/B design.

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3 hours ago, andyr said:

 

C'mon, Ian - as I'm sure you know ... Class A offers that 'special something '!  :)  (If you can put up with their generally low power ratings.)

 

 

Massive heat - yes ... but you don't necessarily need massive heatsinks if you take the 'active approach'.  IE. the output devices are clamped to a finned CPU cooler which has a 12v Noctua fan blowing through the fins.

 

But high power consumption - yes.  :(  Interestingly - did you know that a Class A amp draws the same power whether it's driving the speakers loudly ... or softly!  If its driving the spkrs loudly ... more power goes to the spkrs (and less into the heatsinks).  If the music is soft ... it's the other way round!  :o

 

 

Great-sounding Class AB amps indeed, Ian - but Hugh has also designed a 40w (into 8 ohms) Class A amp which is released on diyAudio (the "Alpha Nirvana") and will be releasing his own (better-sounding!) commercial - ie. ready made version, also 40w into 8 ohms - in the not too distant future ... the "Omega"!

 

Unfortunately, full_dp:

 

 

... I believe the 'Omega' will be more than your budget.  :(

 

Andy

 

 

I'd love to be kept in the loop on the Omega thanks Andy.  I'd need to see if there's an easy way to adjust output levels on the amp though so I can match levels with the amp driving my woofers..... It's only 4x more powerful than I need after all. ;)

 

I'm sure I could be convinced to splash out for it. Have you had a chance to directly compare your Alpha Nirvana with any of the Pass Labs / First Watt amps Andy?

Edited by MattyW
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13 hours ago, MattyW said:

 

I already have a quality external passive.  Thing is its still not useful if the first few clicks go up in volume too much.  My fullrange and helper tweeters average efficiency is 101db so a 10WPC amp is as high as I can usably go. The only way to use a higher powered power amp, is to further attenuate the signal before it gets to the amp.

 

I can very easily achieve high volumes with a 5WPC Pass Amp Camp Amp. The only reason I'm attracted to these more powerful amps is they're much newer designs and amongst the very best Nelson Pass has created. They are too high wattage for my purposes though.

 

The reason I can run a passive pre is simply because my Abbas Audio DAC and phono stage have a very high output level.  :)

 

Have you considered/tried using an external attenuator which uses:  

- Lpad

- Variable/Linear (non stepped)attenuator

- LDR

- High quality DAC preamp - I.e. RME ADI 2 (offers silent/high bit depth variable volume control) 

 

IMO:

Maximum wattage shouldn't be a real concern, assuming you can manage attenuation and amplifier noise floor. 

Oh yes you need to like the sound too. lol. I suspect if you attenuated signal prior to the amplifier with a linear/variable method (that doesn't introduce noise) you should be perfectly fine.

 

The Firstwatt series is optimised for the 1st watt window of power, the amp should be a perfect match for highly sensitive setups.

Additionally, IME the Firstwatt is absolutely dead quiet, at least on my 94db sensitive speaker.

I hear silence with my ear directly on the tweeter.  

 

 

 

Edited by Grizaudio
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1 hour ago, Grizaudio said:

 

Have you considered/tried using an external attenuator which uses:  

- Lpad

- Variable/Linear (non stepped)attenuator

- LDR

- High quality DAC preamp - I.e. RME ADI 2 (offers silent/high bit depth variable volume control) 

 

IMO:

Maximum wattage shouldn't be a real concern, assuming you can manage attenuation and amplifier noise floor. 

Oh yes you need to like the sound too. lol. I suspect if you attenuated signal prior to the amplifier with a linear/variable method (that doesn't introduce noise) you should be perfectly fine.

 

The Firstwatt series is optimised for the 1st watt window of power, the amp should be a perfect match for highly sensitive setups.

Additionally, IME the Firstwatt is absolutely dead quiet, at least on my 94db sensitive speaker.

I hear silence with my ear directly on the tweeter.  

 

 

 

As I've previously said, I already have a high quality, external LDR passive preamp. The issue is not the preamp, though rather that I'm running 101db efficient speakers. I bi-amp as the woofers are a full 10db less efficient and require more power to reach the required levels to match the fullrange and tweeters. 

 

I'm not going to add yet another external box into the chain as it's already source > preamp > 2x poweramps with all the associated downsides  running extra RCA's entail. Basically careful choice of power amp is required for the amp driving the fullrange and tweeters. Essentially 10WPC is ideal.

 

I may have a chat with Hugh once the Omega is available to the market and see if there's a way he can reduce the overall output of the amp in the circuit itself, otherwise it really is down to using a resistor based or maybe DACT attentuator between the RCA socket and the amplifier board. I agree it's not ideal, however you have to match the amp to the rest of the setup. Speakers, as always determine amp choice. Don't get that right, and your system is either unusably loud, or can't drive speakers properly.

 

Anyway, thought I'd explain in a bit more detail why I'm looking for lower powered amps as people keep seeming to tell me the same thing, which I already have.

 

Installing an additional attenuator inside my pre would work if wired to one of the two outputs only, though unfortunately I lack the additional space required inside the unit at the back panel to fit it. The unit is not large. This limits me to finding the solution in the power amp. Any solution will be in the preamp or power amp only to keep the number of RCA cables to an absolute minimum.

 

I may just be able to squeeze something in next to the power cable. Maybe. If I can do that it opens up a lot of amp choices. Though ideally I need to run an amp between 6 and 10WPC.  Perhaps I should stick with the Aleph-M so I retain the advantages of the LDR.

 

20200623_142147.jpg

Edited by MattyW
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On 23/01/2021 at 9:29 PM, deepthought said:

Or just be done with it and get a Pass Labs XA25............ :sorry:

I have one on layby a lot more than 3.5K

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1 hour ago, Gryffles said:

@MattyW I will soon have a similar issue to deal with and IMO the problem should be dealt with using transformers such as these. 

 

http://www.intactaudio.com/atten.html

 

Of course you can find cheaper but quality is essential

 

That's a very interesting solution. I reckon it'd be great from a sonic standpoint. I may just have to get  this   :)

 

Which speaker level autoformer do you think I'd need to allow attenuation down to the level of a 10WPC amp for anything up to 60WPC? Really opens up some amp options! Gives the necessary result without needing to mod amp or passive pre. Wonderful solution.  ;)

Edited by MattyW
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16 minutes ago, camross said:

I have one on layby a lot more than 3.5K

You won't regret it. I had an XA30.8 and as soon as I heard the XA25 I knew it was a keeper.

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3 hours ago, MattyW said:

That's a very interesting solution. I reckon it'd be great from a sonic standpoint. I may just have to get  this   :)

 

Which speaker level autoformer do you think I'd need to allow attenuation down to the level of a 10WPC amp for anything up to 60WPC? Really opens up some amp options! Gives the necessary result without needing to mod amp or passive pre. Wonderful solution.  ;)

I’d suggest talking to Dave at Intact. He’s very obliging

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