Any other suggestions? I would like to stay under $1K, but could go over a bit.
You most likely don't need gain... but most things that I know about that have a more "tubey" character and/or actually use tubes ... have some gain.
How many inputs would you like to have?
Do you need / want to have remote input selection in addition to volume control?
Custom / professional looking chassis as a preference, a must, or don't care? Are you going to design your own, or do you want a 'pre-done' option?
Are any of your sources balanced and/or do you want to run balanced in the future?
For a fraction of your budget, if you like what I'd consider a bit of a "tubey" pre-amp... you could do an ACP+ just to see if you like the sonics. Then, if you happen to like it... you can modify the number of inputs / remote solution / chassis etc. If you don't love it, you can likely sell it in the swap meet. The B1K is certainly a bit of a tone box too, IMO...
The balance (IMO) is that the ACAs all by themselves impart enough of the "tubey" character for me. So, I tend to like as 'neutral' a pre-amp as practical with them. Something as simple / lovely as the B1 may be perfect. You can also do something like the Iron Pre with or without the transformers to lean more toward 'neutral', IMO.
Going off of others' impressions for sonics is always a tough thing... but... the good news is that you have A LOT of room to work with your budget and try things until you find the combo that works best for you. The bonus is / may be that you get to build more stuff while you search for the best combination. 🙂
How many inputs would you like to have?
Do you need / want to have remote input selection in addition to volume control?
Custom / professional looking chassis as a preference, a must, or don't care? Are you going to design your own, or do you want a 'pre-done' option?
Are any of your sources balanced and/or do you want to run balanced in the future?
For a fraction of your budget, if you like what I'd consider a bit of a "tubey" pre-amp... you could do an ACP+ just to see if you like the sonics. Then, if you happen to like it... you can modify the number of inputs / remote solution / chassis etc. If you don't love it, you can likely sell it in the swap meet. The B1K is certainly a bit of a tone box too, IMO...
The balance (IMO) is that the ACAs all by themselves impart enough of the "tubey" character for me. So, I tend to like as 'neutral' a pre-amp as practical with them. Something as simple / lovely as the B1 may be perfect. You can also do something like the Iron Pre with or without the transformers to lean more toward 'neutral', IMO.
Going off of others' impressions for sonics is always a tough thing... but... the good news is that you have A LOT of room to work with your budget and try things until you find the combo that works best for you. The bonus is / may be that you get to build more stuff while you search for the best combination. 🙂
Thanks for the thoughtful response, @ItsAllInMyHead.
When built my original ACA, I tried feeding it directly from my Node streamer and it seemed slightly anemic. I reconfigured to feed the Node into my Marantz 1060 and used the Pre-Out to feed the ACAs and felt there was a pretty significant improvement, so I've assumed the need for some gain ahead of the ACA. It is possible that I don't.
As for inputs, I would like 3-4. However, I have a 4-to-2 switch box I could use with a single input preamp. Remote input switching isn't necessary. I currently do not have any need for balanced input/output, but should maybe think about that for future options.
A professional looking chassis is definitely preferred.
I haven't had a whole lot of DIY experience, so I think I need something that is a proven design. I know there are a lot of great people here who are willing to help, but I think I would like to get a few more projects under my belt before tackling a custom preamp design. I do kind of like your ACP+ idea, though. I have also looked at the B1K project and consider that a promising option. It would mean figuring out how to incorporate multiple inputs and a remote volume control, but you are right that I could start with the basics then add to it. Do either the ACP+ or B1K offer gain, though?
At some point in the future, I may make the move to one of the FW kits, but for now I'm having a great time seeing how far I can take a pair of ACAs.
When built my original ACA, I tried feeding it directly from my Node streamer and it seemed slightly anemic. I reconfigured to feed the Node into my Marantz 1060 and used the Pre-Out to feed the ACAs and felt there was a pretty significant improvement, so I've assumed the need for some gain ahead of the ACA. It is possible that I don't.
As for inputs, I would like 3-4. However, I have a 4-to-2 switch box I could use with a single input preamp. Remote input switching isn't necessary. I currently do not have any need for balanced input/output, but should maybe think about that for future options.
A professional looking chassis is definitely preferred.
I haven't had a whole lot of DIY experience, so I think I need something that is a proven design. I know there are a lot of great people here who are willing to help, but I think I would like to get a few more projects under my belt before tackling a custom preamp design. I do kind of like your ACP+ idea, though. I have also looked at the B1K project and consider that a promising option. It would mean figuring out how to incorporate multiple inputs and a remote volume control, but you are right that I could start with the basics then add to it. Do either the ACP+ or B1K offer gain, though?
At some point in the future, I may make the move to one of the FW kits, but for now I'm having a great time seeing how far I can take a pair of ACAs.
^ Both the B1K and the ACP+ have some gain. Gain isn't necessarily a bad thing at all, IMO... but you're boosting the signal, just to cut it back again in most cases. I can see both points of view.
If you feel like you can take it on, my recommendation (HIGHLY biased) is to try the Iron Pre SE with Frank Wilker's Muses solution for volume / input selection. You can run it as a buffer only (with some fairly easy tweaks), or configure it for 6dB or 12dB of gain with a jumper.
Why?
Again... I'm HIGHLY biased. So, grain of salt... YMMV etc.
Cheers,
Patrick
If you feel like you can take it on, my recommendation (HIGHLY biased) is to try the Iron Pre SE with Frank Wilker's Muses solution for volume / input selection. You can run it as a buffer only (with some fairly easy tweaks), or configure it for 6dB or 12dB of gain with a jumper.
Why?
- EASILY comes in under budget. Even though it's relatively expensive as far as projects go, I think it punches well above its weight.
- It has a touch of gain / configurable to needs.
- Frank's Muses solution is "drop in" and IMO is fantastic. It offers remote volume / input switching / standby and is configurable.
- I just think it works with every amp I've paired with it (including ACAs).
- 5 inputs
- Modushop offers a ready to go custom chassis, that I think not only honors Zen Mod appropriately, but it's quite pretty.
- Tons of people have built it successfully, and it's not a particularly advanced project. Lots of support from ZM himself as needed along with other people in the forum. Exceptional build guide from 6L6 for a version that's very, very close. Exceptional inspiration / instructions for a build.
- For some reason or another (I truly have no clue why or if it's just my imagination) it works incredibly well at high attenuation (aka volume knob below 9 o'clock). Some pre-amps / amps seem to just not sound great (to me) at "don't wake up wifey" listening levels.
Again... I'm HIGHLY biased. So, grain of salt... YMMV etc.
Cheers,
Patrick
I absolutely second @ItsAllInMyHead's recommendation for the IronPre SE. ACA's can almost always do with a bit of gain, in my experience, and I have pretty sensitive speakers. I'm currently listening to my own IronPre SE + ACA combination and it sounds just great. That's intended to be an understatement, because I'm not good at describing sound quality.
Please consider using a tiny bit of your audio budget and upgrade the ACA's with premium parts. https://www.diyaudio.com/community/threads/aca-amp-with-premium-parts.328357
It's best done while populating the PCBs for the first time, so maybe you can even get new PCBs and use those for the premium parts. It's the biggest single improvement I've made to my ACA. (I had a spare boards).
Please consider using a tiny bit of your audio budget and upgrade the ACA's with premium parts. https://www.diyaudio.com/community/threads/aca-amp-with-premium-parts.328357
It's best done while populating the PCBs for the first time, so maybe you can even get new PCBs and use those for the premium parts. It's the biggest single improvement I've made to my ACA. (I had a spare boards).
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@Skylar88 When building with premium parts, did you do anything different than what is discussed in the ACA With Premium Parts thread? It's been a while since I read through that thread, so I need to go back to refresh. So far, my biggest sonic improvement has been to go dual mono with a second ACA. 😀
I think it may be that the ACA is just outgunned by the Fisher X-101-B.
The Fisher is rated at over 20W with THD less than 1%.
The ACA is rated at approximately 5W with nearly 3% distortion.
The distortion of both amps is second harmonic dominant, at least at lower power output.
A low cost, low distortion preamp can be made with the DIY Front End 2022 circuit. Its gain can be adjusted to suit. The cost is low and the performance is high so there is not much monetary risk.
The Fisher is rated at over 20W with THD less than 1%.
The ACA is rated at approximately 5W with nearly 3% distortion.
The distortion of both amps is second harmonic dominant, at least at lower power output.
A low cost, low distortion preamp can be made with the DIY Front End 2022 circuit. Its gain can be adjusted to suit. The cost is low and the performance is high so there is not much monetary risk.
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@ItsAllInMyHead and @Skylar88, thank you both for taking the time to give your thoughts. This is what I love about this group! Now, it is time to dig deeper into your suggestions with some research on the relevant threads. What fun!
I have had the Fisher for a long, long time and found it pretty disappointing with previous speakers. When I bought the Fortes, I pulled it out of storage to give it another try and have been very impressed. Interestingly, the sonic difference between the Fisher and a pair of ACAs is very slight. I assume it is the second order harmonic similarities. Boosting the output of the ACAs to 15w in mono mode may not hurt, either.
@CWelsh52 Not really anything different than what is discussed in the Premium Parts thread, but I think my choice of parts may have contributed to the lovely sound, i.e. Nichicon KG series for C1, Organic Polymer for C2 & C4 as per TungstenAudio's notes and Elna Silmic II for C3. The latter wasn't available at Mouser and Digikey last time I checked, but Parts Connexion have stock.
Let me expand a little on "lovely sound"... Up until when I built the Premium Parts ACA, my M2 amp was my pride and joy and I just loved it's sound. I used quality parts in the M2 too; Elna Silmics, etc.
So, after upgrading the ACA, I naturally wanted to compare it to the M2. I used two preamps in my tests, IronPre SE and B1 buffer. With both preamps, the difference was unexpected. The ACA is now my preferred amp, by far. And in near field where I've done the comparison, one can clearly hear how exceptional the upgraded ACA's sound is.
@Skylar88 I read several of your posts on the Premium Parts thread and see you posted a list of the parts you used. That will be helpful when I'm ready to upgrade. What version is your amp? Mine is a 1.8. I'm not sure if it makes any difference, but I think one or two resistors related to the three-way switch might be different in the stock assembly.
Are you able to describe why you prefer the ACA over the M2? I know that is tough to convey sometimes, so I understand if you can't.
Are you able to describe why you prefer the ACA over the M2? I know that is tough to convey sometimes, so I understand if you can't.
@CWelsh52 I have just posted my BOM with Mouser part numbers in the Premium Parts ACA thread.
I have ACA V1.5 which is upgraded to v1.6. But that's not important, as all versions use the same parts, except as you pointed out, the resistors at the switch.
As I've mentioned before, I'm not good with describing sound. But I can tell you how I compared the premium ACA to the M2. And please don't think I'm saying the ACA is a better amp than the M2. It most certainly isn't "better", and can't replace a 25Wpc amp, because of it's lower power.
I listened to both amps; the Premium Parts ACA and M2, using the same preamp and speakers and the same music that I knew well. Under the same conditions, I could listen to each amp and detect the differences quite easily. While I still loved the sound of the M2, the Premium ACA just had more clarity and sweetness. And especially with the smaller speakers, I heard more and better bass. Something that struck me and which took me by surprise, was whenever I listened the ACA, my breathing stopped involuntarily so that I could enjoy the sound even more. The sound was just so good, I wanted more of it. And when I listed to the M2 again, I missed that exceptional sound. It could be because the ACA is single ended and sounded different because of that. I'm not sure.
A week later an audio friend who also builds FirstWatt amps had a listen to both amps in the same conditions and confirmed my findings.
I have ACA V1.5 which is upgraded to v1.6. But that's not important, as all versions use the same parts, except as you pointed out, the resistors at the switch.
As I've mentioned before, I'm not good with describing sound. But I can tell you how I compared the premium ACA to the M2. And please don't think I'm saying the ACA is a better amp than the M2. It most certainly isn't "better", and can't replace a 25Wpc amp, because of it's lower power.
I listened to both amps; the Premium Parts ACA and M2, using the same preamp and speakers and the same music that I knew well. Under the same conditions, I could listen to each amp and detect the differences quite easily. While I still loved the sound of the M2, the Premium ACA just had more clarity and sweetness. And especially with the smaller speakers, I heard more and better bass. Something that struck me and which took me by surprise, was whenever I listened the ACA, my breathing stopped involuntarily so that I could enjoy the sound even more. The sound was just so good, I wanted more of it. And when I listed to the M2 again, I missed that exceptional sound. It could be because the ACA is single ended and sounded different because of that. I'm not sure.
A week later an audio friend who also builds FirstWatt amps had a listen to both amps in the same conditions and confirmed my findings.
@ItsAllInMyHead, where can I find more information on Frank Wilker's Muses solution for volume / input selection? I tried searching, but think I may be missing some essential information to get a result.
I'm sure ya could find AN AIkido preamp, that someone would be selling for around 500 or so. One definitely doesn't have to worry about gain, as ironically...the only negative quality compared to the 2-5,000 dollar level preamps would be that the aikido has too much gain !😎 Either build one yourself (which can be really easy or a PITA.....ya never know when building ones 1st aikido.......but I've been able to snag impressively built ones quite easily on the message boards. I say all this as I have 2 of em, bought from reputable builders for 450 and 500 and also have 2 ACA monos......my cornscala variant speakers have a sweet synergy with ACAswith AIkido front ends. My system def = garbage in, garbage out or perfection in, perfection out......anyway, it's soul just shouted from the other room, saying that pair provides it, the best 3way in town. ANyway, the aikido or just it as a buffer can range from 30DB down to 6-9DB of gain, per variousdocumented builds I've seen online. But really any decent pre will drive the ACA to full output easily, for the most part. But also the cheap fosi buffer in between ot without a pre coming straight from a DAC should be fine for power/loudness.
I packed my ACAs away a good while ago and decided dust them off again. I built them on the 13th November 2012 according to this thread! Now I remember why I packed them away. One channel is dead. The LED lights up but no one is home.
Any idea what might have failed or how to test?
Any idea what might have failed or how to test?
One of the most common advices in this case: could you post good pictures of the dead board?
Further, pictures of the connectors, etc.
Even further, you could check all the voltages described in the build guide.
In this post you will find the measurement too: https://www.diyaudio.com/community/threads/aca-illustrated-build-guide.247361/post-3735738
Further, pictures of the connectors, etc.
Even further, you could check all the voltages described in the build guide.
In this post you will find the measurement too: https://www.diyaudio.com/community/threads/aca-illustrated-build-guide.247361/post-3735738
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Was it the channel dead when you packed it up 10yrs ago, etc? I per usual, I assume everyone will ask or need to see pics in order to ascertain why. However, especially if the sound seems weak in the good channel, depending on the oreinetation of the rear switch; The first thing to look at is whether or not the PCBs are not accidentally grounded through the heatsink(s). Not necessarily via shorted lead touching the heatsink underneath from various resistors or caps, but through the standoffs for the PCBs. I've seen that a few times, and in my own case.....it drove me nuts......because even though on nylon standoffs I, unecessarily for the most part, decided to use one of the screws from the kit in the center hole into the nylon standoff (which i think is normal per instructions.....however, I managed to strip through it and basically = no sound and weakly in the other). I say drove me nutty, as I had to take the whole board off to even see the miniscule short I created.
Check the supply voltage is reaching the board. Should be 18 or 24 volts depending on the power supply version.
Check the board ground is good (not floating).
Are the FET's getting hot in the bad channel. Yes is good here 🙂
Check the voltage on the plus end of the big speaker coupling cap. This should be around half the supply voltage so 9 or 12 volts depending on the power supply.
And that's it at this point.