Amp Camp Amp - ACA

oc11 said:
Puggie, be patient just wait a year and sometime next summer you will be able to order ACA 1.7, PCBs, components, and cases.
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Around April last year, when I decided to build the ACA, no boards were available from the store. With minimal experience in electronics, I downloaded KiCad and working from the schematic and BOM, a single sided layout was produced - in case I had to etch it myself. But when I saw how inexpensive it was, I mailed the Gerbers to a board house. US$19.38 including shipping from Hong Kong, bought me 10 ACA boards (and bragging rights). The ACA amps worked first time, so no problems with my boards.

Ain't DIY fun? 😀
 

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Puggie said:
I'm about to undertake an ACA build off the back of this thread:

Looking for a little power amp project (spoilt for choice on here)

And I have a couple of issues:
1) No PCBs available, is there a gerber file about for a single or double sided PCB? I can etch no problem but single sided would be prefered if the SQ trade of is not significant.
2) UK component availability, RS is my goto for components and they have no stock of any of the transistors (apart from ZTX) are there UK available equivalents or am I best just using Mouser.

My chassis will be a DIY affair from a heatsink I have available. I will keep my progress posted on here.

thanks

Bill.

p.s. FWIW for soldering I like the Alpha telecore HF-850 63/37
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Perhaps this will help some of you folks that are frustrated with the lack of ACA boards at the diyaudiostore:

https://www.diyaudio.com/forums/group-buys/310775-gb.html#post5149336

But please understand that Jason is doing all that he can and has to wear multiple hats while making equally challenging decisions:

https://www.diyaudio.com/forums/pass-labs/327141-aca-circuit-board.html#post5543298

In addition to pandering to unusually disgruntled diy'ers from time to time!

Jason, thanks for all you do! :cheers:

Best,
Anand.
 
oc11 said:
Puggie, be patient just wait a year and sometime next summer you will be able to order ACA 1.7, PCBs, components, and cases.
Click to expand...


From the DIYStore Website:


UPDATE - SEP 10TH 2018

Batch 2: All chassis and kits have now shipped, 5 days ahead of schedule. Tracking numbers will be attached to orders today.

A batch 3 pre-order will be announced soon.
 
OK Puggie, they just announced a batch 3 for ACA 1.6 coming soon. You will be able to purchase the PCBs, that is unless you want to build your own and make them single sided. You will not need to wait for much longer.
 
I've no intention of buying the kit or chassis. I'm making this from:

left over heatsink from another project + aluminium from work's scrap bin. that is my chassis.

As many passives as I can scavenge from the University Electronic Engineering dept + a minimal spend from RS or similar for the few transistors needed

PSU from the computing dept Weee bin

I'm lazy so if gerbers/eagle files were out there I would just etch my own pcbs from scrap FR4 offcuts in EE again.

I was hoping to turn this amp out for about the same cost a 4 pints of decent beer and make myself far too much work compared to buying a kit (but that is DIY isn't it).

This means no disrespect to the people that put these kits together and sort all this out. I'm just a proper tight ****/skinflint/penny pinching/yorkshire man 🙂

p.s. another tech question. What is the anticipated current draw from a single channel at 24v, I've found a couple of open frame switch mode supplied that would fit in the casing but they are about 60w only.

Hmmm, just spoted the last post. maybe if I concentrate of the chassis first, if the PCBs are in i will buy them, if not I'll fire up eagle and see what I can remember!
 
Something came to my mind thinking about my post of getting musical value for the least price when building a project. That is how is musical value established. A lot of the musical value obtained from a given system is a subjective measure. Is the music from the new amps more pleasing to your taste than what you are currently getting from your present system? To answer this you have to examine your current system realistically.

The truth is that if you have an all Krell system you are not likely to improve much on it, or at least Krell hopes you do not. So let's get real. The following is my current system, it is old but it is pleasing to my ear, and I hope my new monoblocks plus a few other upgrades will surpass it. So what am I playing music with:

1. Amplifier Linn LK 280, not sure if class A or class AB. This is fed with the Linn Spark PSUs, separate PSUs for each with balanced power outputs. I was never sure of the effect the separate balanced power supplies for each channel had, but I believe it was major. The Linn sounded better to me than my class A Forte, an early Nelson Pass Class A from before he joined Threshold.
2. CD transport used to be a dedicated Cal Audio which was fried during a thunderstorm and replaced with a plain Sony DVD player with a coax output, Sony BDF BX50. It works, what can I say.
3. DAC Chroma 396 by Wadia, ancient as the hills but works and is musical. Time to replace.
4. Preamp McCormack TLC-1, wonderful piece with optional balanced outputs.
5. Volume control using one of those little eBay boxes with a beefy ALPS pot inside works fine.
6. Speakers self-built bookcase speakers without porting, hybrid 3rd order and 4th order Butterworth crossovers, self-built. 5" VIFA paper cone drivers and 1" silk dome tweeter whose brand went out of business and I can't recall. The paper cone and silk dome doctored with multiple applications of diluted paint varnish. You have never heard Louie Armstrong's raspy voice as it comes out of these puppies.
7. Subwoofer an old down-firing 8" AR cone.
8. Speaker cables self-built out of woven Cat 5 wires.


This is not a purist system but it is the very best I could put together. The speakers and cables stay, the subwoofer stays too even though is it mediocre at best. I think the McCormack preamp will also stay. What I want to replace now are the DAC, the transport, and the amps assuming the ACA 1.6s sound better to my ears. Little steps all the way, saving money wherever I can and substituting my own labor in the bargain.

If you are in the money is no object crew, you are way-way out of my league. This means to me that if I am lucky the ACA 1.6's will sound better than the Linn. I hope so.
 
My ACA competes side-by-side with my $1500 NuPrime ST-10. The ST-10 has a slight edge on resolution, while the ACA has a slight edge on overall balance (the ST-10 being a bit treble-harsh). - This is sound-quality wise, obviously, the 150W ST-10 has the advantages of higher output.

The LK 280 was around the same $1500 but in 1989. That purchased quite a bit 'more' during those days, but you are fighting 30 years of evolution, so I think you would rather like the ACA.

The thing to consider is that your Linn is 80W at 8 Ohms and has 26dB of voltage gain. Your PRE is a unity gain pre. So perhaps you need a bit more gain within your chain to better accommodate the ACA? Without it, you might feel the sound a bit 'thin' with low punch and volume.

Other than that, the 3Kohm input impedance of your AMP is rather low-ish, so the greater 10Kohm of the ACA would perhaps prove a bit easier to drive.

Still, the Unity-Gain PRE + 26db Gain AMP vs the 10db gain of the ACA could present an issue.

Best regards,
Rafa.
ps. Obviously price of equipment means nothing in itself, I'm just using it as a base reference having never heard the LK 280.
 
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Forgot to add that I also own a pair of Maggie speakers, 2nd version. Very nice for music, not so much for voice, the bookcases are better for voice. However, my wife thinks the Maggies are drop dead ugly and does not want to see them in areas open to visitors. So they rest in the basement gathering dust.
 
Puggie said:
A
I was hoping to turn this amp out for about the same cost a 4 pints of decent beer and make myself far too much work compared to buying a kit (but that is DIY isn't it).

This means no disrespect to the people that put these kits together and sort all this out. I'm just a proper tight ****/skinflint/penny pinching/yorkshire man 🙂

p.s. another tech question. What is the anticipated current draw from a single channel at 24v, I've found a couple of open frame switch mode supplied that would fit in the casing but they are about 60w only.
Click to expand...

Cheapskate 😉

As long as you realise it will not be an ACA when you've finished then I would say you have little to lose by experimenting.

The input FET us where things could get interesting but at least the preset allows a massive range of adjustment. The power FET's should be easy to substitute as is the regulator transistor.

60 watt @ 24 volts only gives you around 2.5A to play with. Not enough for a stereo pair. You could try scaling the 0.47 and 0.68 ohms up to say 0.68 and 1 ohm to bring the current down.
 
Thank you Rafa. I believe I have read in various places in this blog that the db gain of the monoblocks is higher than that of the stereo unit, and that the unit gain of the balanced input monoblocks is higher still. Of course, the input level fed to the amps will also have an effect. I mentioned earlier on that the Schiit Gungnir DAC balanced output achieves 4 v RMS. If you look at the photos of the Gungnir's guts at the Schiit site you will easily see that it has 2 transformers, one per channel, and two analog boards again one per channel. This is exactly what I am looking forward to pair with the monoblocks each one with its own PSU as well. So, it is looking like I will have had a lot of entertainment trying to puzzle this stuff out as I move forward.

By the way, sometime in the 70's Harman Kardon produced a commercial stereo amp with two separate internal power supplies. It supposedly was wonderful but it was expensive to produce and did not sell well so it was cut off. I got the Linn exactly because of the separate PSUs in the Spark PSU.

I have a good feeling about the combo of a Gungnir with balanced outs and the ACA 1.6 monoblocks. If it does not pan out I will probably get the extra gain in terms of a preamp between the DAC and the ACA. I do not know about you, but to me, this looks like a lot of fun is coming my way.
 
Rega RS1 with ACA?

Hello,

I have a Rega RS1 pair of speakers but I’m a newbie in the audiophile world. I read about Pass AmpCampAmp and I’m interested. I read the specifications and RS1 speakers need minimum 30 watts amplifier but the ACA have 8+8 = 16 watts. I read also that one Pass Class A Amplifier watt is not equal with an ordinary watt. So, my question is: it can be propper (in a way) for these speakers to use ACA? If it is not, what other Pass Amplifier can be propper for these speakers?

From Rega RS1 specifications:

  • Nominal impedance � 8 Ohm
  • Sensitivity � 90dB
  • Power � 80w per channel (one can use amplifiers from 30 to 80 watts).
Thank you in advance for your answers and excuse me if my question is a stupidity...
 
Puggie said:
... I have a couple of issues:
1) No PCBs available, is there a gerber file about for a single or double sided PCB? I can etch no problem but single sided would be prefered if the SQ trade of is not significant.
2) UK component availability, RS is my goto for components and they have no stock of any of the transistors (apart from ZTX) are there UK available equivalents or am I best just using Mouser.
Click to expand...

In the UK, Farnell have IRFP240 and ZTX450 in stock, maybe widen your department's buying choices?
You can find genuine 2SK170 devices with a little searching too.

You could be a real cheapskate and use strip board too ... 🙂
Alan
 
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Alan4411 said:
In the UK, Farnell have IRFP240 and ZTX450 in stock, maybe widen your department's buying choices?
You can find genuine 2SK170 devices with a little searching too.

You could be a real cheapskate and use strip board too ... 🙂
Alan
Click to expand...

Thanks for the heads up, I default to RS, but Farnell is fine too 🙂 The 2sk170s are available without too much grief so I would probably stick to the original ACA spec, I have a fair stash of decent electrolytic caps (Ruby XYZ and ZL, Panasonic FCs) so probably have something suitable.
 
oc11 said:
Thank you Rafa. I believe I have read in various places in this blog that the db gain of the monoblocks is higher than that of the stereo unit, and that the unit gain of the balanced input monoblocks is higher still. Of course, the input level fed to the amps will also have an effect. I mentioned earlier on that the Schiit Gungnir DAC balanced output achieves 4 v RMS. If you look at the photos of the Gungnir's guts at the Schiit site you will easily see that it has 2 transformers, one per channel, and two analog boards again one per channel. This is exactly what I am looking forward to pair with the monoblocks each one with its own PSU as well. So, it is looking like I will have had a lot of entertainment trying to puzzle this stuff out as I move forward.

By the way, sometime in the 70's Harman Kardon produced a commercial stereo amp with two separate internal power supplies. It supposedly was wonderful but it was expensive to produce and did not sell well so it was cut off. I got the Linn exactly because of the separate PSUs in the Spark PSU.

I have a good feeling about the combo of a Gungnir with balanced outs and the ACA 1.6 monoblocks. If it does not pan out I will probably get the extra gain in terms of a preamp between the DAC and the ACA. I do not know about you, but to me, this looks like a lot of fun is coming my way.
Click to expand...


OC11,

I don’t know where you have read it, but I confirmed with Nelson Pass as well as my own measurements that whether you use the RCA inputs and run the unit as a “stereo amplifier” or whether you have a pair of monoblocks with XLR as the input and use the outputs in a bridged configuration, the overall gain is the SAME. It is 10-11 dB. Same is true if you are using the RCA inputs and running it as monoblocks.

Which means about 2.25-2.4 V RMS is required for maximum power (8-15 watts depending on configuration above).

I have not tested the new “Parallel” configuration however.

Best,
Anand.
 
mihstef said:
Hello,

I have a Rega RS1 pair of speakers but I’m a newbie in the audiophile world. I read about Pass AmpCampAmp and I’m interested. I read the specifications and RS1 speakers need minimum 30 watts amplifier but the ACA have 8+8 = 16 watts. I read also that one Pass Class A Amplifier watt is not equal with an ordinary watt. So, my question is: it can be propper (in a way) for these speakers to use ACA? If it is not, what other Pass Amplifier can be propper for these speakers?

From Rega RS1 specifications:

  • Nominal impedance � 8 Ohm
  • Sensitivity � 90dB
  • Power � 80w per channel (one can use amplifiers from 30 to 80 watts).
Thank you in advance for your answers and excuse me if my question is a stupidity...
Click to expand...

At 90dB sensitivity, the Pass ACA should be able to drive your RS1s to more than acceptable loudness levels.

How large is the listening room with your RS1s?
 
Hello Anand

I know you kindly sent a link to Nelson Pass' statements saying that the ACA output is the same for the stereo version as for the monoblock. However, if you go to the ACA KIt 1.6 entry (sold out) in the diyaudio store and scroll down to the specifications you will find it clearly stated that the output for the stereo version is 8w per channel and the output for the monoblock version is 15w per channel. So, the output doubles even though the gain per (? board) stays the same. What am I missing here?
 
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