advise on diy pass amp

advice on diy pass amp

Hello,

after years i upgraded my speakers. from a mltl full range fostex 164 to a compact two way (scan speak revelator - 90db efficency). Now it is time to upgrade the amp. (current tripath t2024).

i don't need a lot of power, i listen near field. i think i only use 1-2W most of the time. 5w would do fine, 10w would be plenty.

i have looked into the aca amp. which would do nicely. but a lot of mr Nelsons designs are available, some of them can be bought in kit form, other only the main pcb... so i wonder if there is an amp model that is regarded as the better model and there is at least a schematic available. (i can't do it without). or pcb or kit form ? if you look on ebay you find some people who are offering these amps ready build.

i know it's quite subjective. also depends on music, room, speakers, source...

what could be interesting is an amp which sounds also great at 12vdc (at 5w) but could also be run at 24-36vdc at 10-20watt... so that i can adjust the voltage if needed. (i mean not on a daily basis, but if i change speakers i could keep the amp and in the meanwhile not having an oven in my room)

thanks
kind regards
the dude
 
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Member
Joined 2019
Paid Member
Hello,

after years i upgraded my speakers. from a mltl full range fostex 164 to a compact two way (scan speak revelator - 90db efficency). Now it is time to upgrade the amp. (current tripath t2024).

i don't need a lot of power, i listen near field. i think i only use 1-2W most of the time. 5w would do fine, 10w would be plenty.

i have looked into the aca amp. which would do nicely. but a lot of mr Nelsons designs are available, some of them can be bought in kit form, other only the main pcb... so i wonder if there is an amp model that is regarded as the better model and there is at least a schematic available. (i can't do it without). or pcb or kit form ? if you look on ebay you find some people who are offering these amps ready build.

i know it's quite subjective. also depends on music, room, speakers, source...

what could be interesting is an amp which sounds also great at 12vdc (at 5w) but could also be run at 24-36vdc at 10-20watt... so that i can adjust the voltage if needed. (i mean not on a daily basis, but if i change speakers i could keep the amp and in the meanwhile not having an oven in my room)

thanks
kind regards
the dude

Hi Dude -

All the "which sounds better?" discussions will not include me. :D However, it could be argued that any of the First Watt (FW) clones are "better" than the Amp Camp Amps (ACA). I've built 5 of the FW clones and found them all quite enjoyable to build.

All the FW amps I've built sound wonderful. However, that's not too useful to pick an amp. Personally ... I'd advise Aleph J or F5 for First Watt. I've built both. The Aleph J seems to be a favorite among many and is sometimes known for a "sweet" sound. The F5 is extremely versatile and easy to build (but biasing can be tricky the first time). If you want, you can even tailor the harmonic distortion to your preference. Not necessary, but it's a neat feature.

I am a relative noob, but I'd advise listing, weighing, and reviewing your priorities privately to help with a decision. Once you've decided whether or not you're going to build a "full-sized" amp and PSU or not - it's easier to pick.

Some examples may be:

FW vs. ACA
1) Budget - In general, the FW clone amps will end up costing more than an ACA.
2) Size - In general, once completed, the FW clone amps will take up more space than an ACA. You say you listen near-field ... Look up the dimensions of the 4U "jack of all chassis" vs. the ACA chassis dimensions for a general concept.
3) Complexity to build - In general, the FW clone amps will be more challenging to build than an ACA.
4) "Kit" vs. source your own parts - The ACA can be purchased with literally everything you need for a complete project except the tools. All others (even the board kits) will require you to source other major components to complete your project. Some parts are harder to find and/or more costly than others depending on choices you make.
5) Comfort with AC / Mains voltages - It should be taken seriously and at least be part of the discussion. ACA no mains voltages. FW - mains voltages.
6) What tools do you already have or do you want to buy? In some cases multiple DMMs make life easy... a variac, a dim bulb tester etc. etc. ACA, you basically need a very small toolkit. Others, more tools make life easier.
7) Do you want to do your own chassis or buy one totally pre-drilled and tapped... partially done?
8) Do you want to build your own power supply or use a "laptop brick"? ACA runs off the laptop brick. All First Watts require that you'd build a power supply - see also mains voltages.

Other things:
I don't know of an amp that can operate well within the range of voltages you listed.. sorry. Others may have a suggestion if that's important. Some people love to crank up the bias (me included) for some of the amps. However, that's neither here nor there. In general, FW amps are going to generate more heat than the ACA.

I'd strongly caution against buying any FW products, kits or anything labeled as "Pass" off of the auction sites. Some could include fake transistors and/or are being sold without permission to use the intellectual property of Nelson Pass / First Watt / Pass Labs etc. I'd advocate that you support the store directly when you need boards or buy things from known sources with permission to use the intellectual property.

You asked if kits / boards / schematics are available - yes. Start with the store website. You can find everything from bare boards and partial kits, all the way to full kits (for the ACA). Pick an amplifier, read the description of the product, go to the build guide and see if you're comfortable...

The diyAudio Store - DIY amplifier kits, chassis, and parts

You'll enjoy the music from any choice you make.

:cheers:
 
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Joined 2003
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Hello,

after years i upgraded my speakers. from a mltl full range fostex 164 to a compact two way (scan speak revelator - 90db efficency). Now it is time to upgrade the amp. (current tripath t2024).

i don't need a lot of power, i listen near field. i think i only use 1-2W most of the time. 5w would do fine, 10w would be plenty.

i have looked into the aca amp. which would do nicely. but a lot of mr Nelsons designs are available, some of them can be bought in kit form, other only the main pcb... so i wonder if there is an amp model that is regarded as the better model and there is at least a schematic available. (i can't do it without). or pcb or kit form ? if you look on ebay you find some people who are offering these amps ready build.

i know it's quite subjective. also depends on music, room, speakers, source...

what could be interesting is an amp which sounds also great at 12vdc (at 5w) but could also be run at 24-36vdc at 10-20watt... so that i can adjust the voltage if needed. (i mean not on a daily basis, but if i change speakers i could keep the amp and in the meanwhile not having an oven in my room)

thanks
kind regards
the dude

Read 6l6's build guides. All is there. My suggestion is Aleph J. Next, as others said M2. Least hot is F6, Sonically I liked the first 2 better.
All are great amps. See zenmods babysitter for cooling of hotter amps.

Russellc
 
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Since you mention yourself that schematic is minimum for you to build from, it sounds like building a FW DIY amp should not be a great issue. The F6 is a popular choice, it comes as a kit with almost everything, as well as jfets matched available from diyaudiostore.com. The chassis from modushop comes pre-drilled, it really could not be easier to make a high quality amp that will last you a long time.


It won't do the adjustable voltage thing, but i would still argue that you're going to have something far more versatile than building an ACA, should you decide to change your speakers at a later point.



My personal experience, having built the F6 as my first real amp project (not counting head amps), the only drawback really is that it is hard to justify an upgrade now (without shelling out serious cash) - i am amassing materials to build some of the other FW amps, but that is mainly to try out flavors (and not likely to happen in a rush).


There is another added benefit, also mentioned in many of the similar threads here, that once you have one FW amp built in a good chassis (for ultimate choice go 5U deluxe), you can easily build up other FW amp boards and swap them in to try something else.
 
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I'll give you a different approach or different way to start and agree with everyone's comments that they are all great 'next' amps to try.

I would suggest you start with the PSU first. Almost all of the FW projects use the same basic PSU so familiarize yourself with building that and then look at the criteria for what amp to use it with.

You'll need a PSU board and fortunately the DIY store carries a universal board that you can use with external monolithic bridge rectifiers or use the optional diode section on the PSU board. Best of all, there is an accompanying 6L6 illustrated build guide:

diyAudio Power Supply Circuit Board v3 illustrated build guide

You will also need a dual secondary 18V+18V transformer to feed the PSU. There are many different brands, sizes and styles to choose from but for a reputable brand, 300VA would be the minimum and 400VA would be a better choice if available at a small increase in cost. I think in EU, many members use Toroidy and in NA many people use Antek. If you are going to build M2 or F6 or some variant with an autoformer (transformer gain stage) then consider getting a shielded version of your transformer. Antek carries the AS4218 which is a shielded 400VA transformer with dual 18V secondaries:

AS-4218 - 400VA 18V Transformer - AnTek Products Corp

As far as which amp to build, it really depends on your speakers. If you have really high sensitivity speakers (93+ dB/W) you may need to take extra precautions to avoid EM noise/hum in something like the M2. I haven't built the M2X which is available in the DIY store so not sure if that one is susceptible to hum but I do have some hum in my M2.

I would recommend building EUVL's UDNeSS as a first project actually. You may have to search for boards but some members have had boards made that you could buy from potentially. The best part of that project is that you don't need the hard to find JFETs (SJ74 and SK170) as it uses J113 (63 cents each in Canada) and regular IRFP9240 mosfets. It is a similar topology to the FW J2 but be aware that this isn't so great with low impedence speakers. Check the impedence curve for your speakers to make sure they don't drop down below 6 ohms or so depending on how loud you listen. For more information read the J2 reviews.

UDNeSS, or You don't need Semisouth's

Good luck and be sure to let us know what you decide!
 
Hello,

after years i upgraded my speakers. from a mltl full range fostex 164 to a compact two way (scan speak revelator - 90db efficency). Now it is time to upgrade the amp. (current tripath t2024).

i don't need a lot of power, i listen near field. i think i only use 1-2W most of the time. 5w would do fine, 10w would be plenty.

i have looked into the aca amp. which would do nicely. but a lot of mr Nelsons designs are available, some of them can be bought in kit form, other only the main pcb... so i wonder if there is an amp model that is regarded as the better model and there is at least a schematic available. (i can't do it without). or pcb or kit form ? if you look on ebay you find some people who are offering these amps ready build.

i know it's quite subjective. also depends on music, room, speakers, source...

what could be interesting is an amp which sounds also great at 12vdc (at 5w) but could also be run at 24-36vdc at 10-20watt... so that i can adjust the voltage if needed. (i mean not on a daily basis, but if i change speakers i could keep the amp and in the meanwhile not having an oven in my room)

thanks
kind regards
the dude

dude, just build them all...
 
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Joined 2019
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Might take a look at the Aksa Lender P-mos Hybrid Aleph (ALPHA) Amplifier, a build thread for this amp is located here also. It is a variant of the Pass Aleph but does not require the more expensive and matched semiconductors.

I've built the Aleph J and F6 so far (and also a newb.) Both outstanding amps. The F6 kit on the store comes with great, well matched and is an easy build. Especially easy if you buy one of the deluxe chassis, though not the most cost-effective approach. My F6 is still burning in, but my initial impressions favor (slightly) the Aleph J. Mainly because of those sweet, sweet mids. That said, The F6 has really great control in the lower end and a superb sound overall.

I'm not sure I'd be too concerned amount transistor costs with the Aleph J, especially if you go with the LS jfets.
 
I'll give you a different approach or different way to start and agree with everyone's comments that they are all great 'next' amps to try.

I would suggest you start with the PSU first. Almost all of the FW projects use the same basic PSU so familiarize yourself with building that and then look at the criteria for what amp to use it with.

You'll need a PSU board and fortunately the DIY store carries a universal board that you can use with external monolithic bridge rectifiers or use the optional diode section on the PSU board. Best of all, there is an accompanying 6L6 illustrated build guide:

diyAudio Power Supply Circuit Board v3 illustrated build guide

You will also need a dual secondary 18V+18V transformer to feed the PSU. There are many different brands, sizes and styles to choose from but for a reputable brand, 300VA would be the minimum and 400VA would be a better choice if available at a small increase in cost. I think in EU, many members use Toroidy and in NA many people use Antek. If you are going to build M2 or F6 or some variant with an autoformer (transformer gain stage) then consider getting a shielded version of your transformer. Antek carries the AS4218 which is a shielded 400VA transformer with dual 18V secondaries:

AS-4218 - 400VA 18V Transformer - AnTek Products Corp
Can I ask- this one's out of stock- and the next one up is 500VA, and a little larger- any reason that wouldn't work?


Thanks!
 
With all of the suggestions above, I'm sure you're confused now...
Don't worry.
That's really the process of infection once you are bitten by diyaudio bug.
Once you finish your next amp, your craving does not stop there...
Like most of us, you end up building many amps.

I hope somebody finds us all a vaccine:D:D