I really want to try my hand at building an amp for myself. I can solder and I should be able to competently stuff a mildly complicated board. It just seems like a project I will want to do until I try it. I felt the same way about recapping and rebuilding a few older speakers. I just wanted to see what all the fuss was about.
I have done a lot of reading here and elsewhere to get to this point. I have a few decisions to make so I am here looking for advice and comments. I would be pairing the amp I build with a 1 year old pair of Zu Audio Omen Dirty Weekend mkII speakers. These speakers are pretty efficient and they feature a nearly full range driver with a super tweeter crossed at 12k. Right now they are being powered by an Adcom GFA-535 that my wife found in a thrift store a few years ago. I really like the way they sound, but I can't help thinking they would sounds much better paired with a better power amp.
I recently read through Paul McGowans book about stereo setup and after moving my DWs around I am convinced that I am still a long way from getting the best out of them. This amp will just be the next step along the way.
I listen to just about every type of music, but spend the majority of my time with mellow electronic, jazz or rock and roll playing. I would use a combination of input and would be able to choose between an Anthem TLP-1 or Yamaha WXC-50 as a preamp to start with. At the moment the Zu Audio DWs are in my office (13x11), but I may look to move them into another larger room as I think they need more room to breathe.
I was trained (many years ago) as an electronics technician (aviation) by the Navy so I remember enough to be dangerous. While I still work in the field, I have not worked on gear directly for a few decades. I have a decent soldering iron and all the basic tools and supplies that should be required.
The reason I am thinking about a build for my DWs is all my other speakers require a LOT more power. Both other sets are currently getting at least 200w. I could look for something to build that puts out that kind of power, but it seems more dangerous and potentially much more expensive. I may get there someday....
I am looking to the First Watt clones or Amp Camp Amp because both are well established, well liked and seem like they are potentially a great match.
I did run my DWs on a flea power AppJ tube amp and the sound was great. I have experienced what the DWs can do with just 3w. I imagine 25+/- watts from a carefully designed class A nelson pass design would be pretty good.
The ACA looks to be a pretty simple and was designed to be put together in an afternoon so I imagine it would be the easiest option. The kit comes with everything I would need and the cost is relatively low. My main concern is I will get it together and find that my apatite is only wetted and I immediately want more...
In the same price range is the Akitika GT-102. I am not a fan of how it looks, and it looks like a very different animal. Not necessarily better or worse just a different direction.
Looks to me like the aleph J or F6 would come in under $800 so I guess another question would be if there is something else out there for that cost that should be on my short list?
Questions and comments are welcome. Thanks for reading!
I have done a lot of reading here and elsewhere to get to this point. I have a few decisions to make so I am here looking for advice and comments. I would be pairing the amp I build with a 1 year old pair of Zu Audio Omen Dirty Weekend mkII speakers. These speakers are pretty efficient and they feature a nearly full range driver with a super tweeter crossed at 12k. Right now they are being powered by an Adcom GFA-535 that my wife found in a thrift store a few years ago. I really like the way they sound, but I can't help thinking they would sounds much better paired with a better power amp.
I recently read through Paul McGowans book about stereo setup and after moving my DWs around I am convinced that I am still a long way from getting the best out of them. This amp will just be the next step along the way.
I listen to just about every type of music, but spend the majority of my time with mellow electronic, jazz or rock and roll playing. I would use a combination of input and would be able to choose between an Anthem TLP-1 or Yamaha WXC-50 as a preamp to start with. At the moment the Zu Audio DWs are in my office (13x11), but I may look to move them into another larger room as I think they need more room to breathe.
I was trained (many years ago) as an electronics technician (aviation) by the Navy so I remember enough to be dangerous. While I still work in the field, I have not worked on gear directly for a few decades. I have a decent soldering iron and all the basic tools and supplies that should be required.
The reason I am thinking about a build for my DWs is all my other speakers require a LOT more power. Both other sets are currently getting at least 200w. I could look for something to build that puts out that kind of power, but it seems more dangerous and potentially much more expensive. I may get there someday....
I am looking to the First Watt clones or Amp Camp Amp because both are well established, well liked and seem like they are potentially a great match.
I did run my DWs on a flea power AppJ tube amp and the sound was great. I have experienced what the DWs can do with just 3w. I imagine 25+/- watts from a carefully designed class A nelson pass design would be pretty good.
The ACA looks to be a pretty simple and was designed to be put together in an afternoon so I imagine it would be the easiest option. The kit comes with everything I would need and the cost is relatively low. My main concern is I will get it together and find that my apatite is only wetted and I immediately want more...
In the same price range is the Akitika GT-102. I am not a fan of how it looks, and it looks like a very different animal. Not necessarily better or worse just a different direction.
Looks to me like the aleph J or F6 would come in under $800 so I guess another question would be if there is something else out there for that cost that should be on my short list?
Questions and comments are welcome. Thanks for reading!
The Adcom GFA-535 was a Nelson Pass design. Not bad for a thrift store find. 🙂 It sounds like your speakers need some power so I don’t know if an 8w ACA is going to do the trick. The larger 25w class A amps are better but if you have low sensitivity (circa 84dB at 1w), even 25w is not enough. The Akitika is a nice amp but based on a chip amp - not sure if that is going to beat your Adcom. I would look for at least 35w+ Class A amps if you want to experience more dynamics and power. There are a ton of amps on DIYA that would be great starter projects.
The Solid State forum might be a better place to look for a higher power Class AB starter amp.
I can highly recommend Vzaichenko’s VHEX+. 100w Class AB. Easy to build and sounds great.
Some amps on Apex Ultimate 100w amp thread are great too. List of his amps is here.
If you are considering the Akitika, maybe look at my open source Xmas amp giveaway based on TDA7293. Easy to build and sounds great. I even have some spare PCBs I could give you if interested.
Hope that helps. Good luck!
The Solid State forum might be a better place to look for a higher power Class AB starter amp.
I can highly recommend Vzaichenko’s VHEX+. 100w Class AB. Easy to build and sounds great.
Some amps on Apex Ultimate 100w amp thread are great too. List of his amps is here.
If you are considering the Akitika, maybe look at my open source Xmas amp giveaway based on TDA7293. Easy to build and sounds great. I even have some spare PCBs I could give you if interested.
Hope that helps. Good luck!
Last edited:
Thanks for the responce.
Here are some specs on the DWs. Some have reported lower than the 97db sensitivity indicated on their website, but they are fairly efficient. On the 3w tube amp they sounded pretty good.
Omen DW Mk.II Quick Specs
Height: 36” [91.5 cm]
Footprint: 12 x 12” [30.5 x 30.5 cm]
Weight: 54 pounds [24 kg] each
Bandwidth: 35 ~ 25 kHz
Efficiency: 97 dB-SPL 1W, 1m
Impedance: 12 ohm
Power Amp Range: 4 ~ 300 watt
Made by us in Ogden, Utah
If you have 97dB sensitive speakers then ACA or any Pass 25w amp would be more than enough.
You should also look into the MoFo and LuFo. Both are choke loaded followers 11w and 39w respectively. Will need a powerful preamp to do the voltage gain though. Pass ACP+ is good choice as well as WBA18 line stage.
You should also look into the MoFo and LuFo. Both are choke loaded followers 11w and 39w respectively. Will need a powerful preamp to do the voltage gain though. Pass ACP+ is good choice as well as WBA18 line stage.
I recommend the Akitika GT-102 because it is a full and complete kit. Somebody else did all of the parts-ordering, including dealing with out-of-stock and backordered components. And they got the quantity=250 discount, which you would not. Somebody else drilled all the necessary holes in the chassis, front panel, rear panel, and heatsinks. Somebody else ordered all necessary bolts, nuts, lockwashers, screws, and other mechanical hardware. Somebody else arranged for the front panel and back panel lettering to be professionally silk screened on. Somebody else figured out the optimum way to route all of the internal wires and drew it for you. Somebody else wrote a 30+ page assembly manual.
A full and complete kit lets you focus on what you talked about in post #1 of this thread: stuffing and soldering and assembling. Not purchasing. Not using a drill press. Ad nauseum.
There will be plenty of time later to build additional projects, which require you to do a lot more than stuffing and soldering and assembling. Indeed the vast majority of the projects on this site and in the diyAudio Store, are not full and complete kits. Take a look around! Heck, two of the projects in the Store were put there by me ("M2x" and "Noir") and neither of them is a full and complete kit. You'll have loads of opportunities to learn and grow, you won't be forever stuck as merely a soldering technician. But why not get a resounding success under your belt when you're just starting out, giving you confidence and optimism about subsequent projects?
A full and complete kit lets you focus on what you talked about in post #1 of this thread: stuffing and soldering and assembling. Not purchasing. Not using a drill press. Ad nauseum.
There will be plenty of time later to build additional projects, which require you to do a lot more than stuffing and soldering and assembling. Indeed the vast majority of the projects on this site and in the diyAudio Store, are not full and complete kits. Take a look around! Heck, two of the projects in the Store were put there by me ("M2x" and "Noir") and neither of them is a full and complete kit. You'll have loads of opportunities to learn and grow, you won't be forever stuck as merely a soldering technician. But why not get a resounding success under your belt when you're just starting out, giving you confidence and optimism about subsequent projects?
Thanks, this is what I was thinking regarding speaker sensitivity. I do not have many preamps laying around so the additional amplifiers you suggest may be beyond my current set up.
Thanks for your thoughtful response. Your recommendation is no doubt a good one. The Akitika kit would maximize my chance of finishing quickly and avoiding problems. I did encounter some "out of stock" items when I was going through the BOL last night for an Aleph J. I didn't work on that problem for too long, but I am sure it can be resolved. My primary concern would be how that Akitika amp would sound. I would rather overcome some difficulties but eventually end up with a great sounding amp than build a quick project that is disappointing.
I had sort of dismissed the GT-102 in my head and I will have to reasses.
It will go together 3X easier than ANYTHING you see on the diyAudio website. Including both of the products in the diyAudio Store, designed by me. You've paid for top flight, first class support / instructions / kitted contents , and that's what you got. Your first project will be (comparatively) easy, and it will help you discover just what you can do, when motivated.
edit- put away the beer. Take out the Anejo tequila.
_
edit- put away the beer. Take out the Anejo tequila.
_
Last edited:
All done. Started work on Friday and finished up Sunday afternoon. The kit went together really well, the directions were great and I am glad I went this route to get my feet wet and build some confidence. Starting here was great advice. It is downstairs now playing and settling in. Sounds great so far.
Stuffing the boards was easy peasy...
https://www.diyaudio.com/forums/attachment.php?attachmentid=968207&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968208&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=9
68209&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968211&stc=1&d=1626699531
All that left was wiring and loading the chassis, then it was time to test and hook it up for a test drive.
https://www.diyaudio.com/forums/attachment.php?attachmentid=968211&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968211&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968212&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968214&stc=1&d=1626699531
I think I will start collecting parts for my next build shortly. Cheers,
Caleb
Stuffing the boards was easy peasy...
https://www.diyaudio.com/forums/attachment.php?attachmentid=968207&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968208&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=9
68209&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968211&stc=1&d=1626699531
All that left was wiring and loading the chassis, then it was time to test and hook it up for a test drive.
https://www.diyaudio.com/forums/attachment.php?attachmentid=968211&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968211&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968212&stc=1&d=1626699531
https://www.diyaudio.com/forums/attachment.php?attachmentid=968214&stc=1&d=1626699531
I think I will start collecting parts for my next build shortly. Cheers,
Caleb
Attachments
-
216593539_10159505268698670_7248993008377019426_n.jpg -
216327750_10159505268743670_2539387640402041928_n.jpg -
215984506_10159505268638670_7802876480184413727_n.jpg -
217200237_10159505268573670_4461187444996781135_n.jpg -
218796794_10159504251968670_7037779835229900095_n.jpg -
216937132_10159505268453670_208748901190275318_n.jpg -
214205529_10159504252103670_1528974738128456734_n.jpg -
216036004_10159504252018670_6059559287219884457_n.jpg
That was unreasonably fast!
A regular build with going back and forth between designs, putting together several BOMs, ordering from several vendors, discovering that you already have these parts in stock, putting off metalwork to finish the chassis, stuffing pcbs, procrastinating doing the internal wiring while working on another build that has also been sitting on the bench for too long, firing up the amp late at night and not daring to hook it up to the main speakers ... all that usually takes months!
Don't get used to the pace at which you just finished your first build 😀
Congrats!
A regular build with going back and forth between designs, putting together several BOMs, ordering from several vendors, discovering that you already have these parts in stock, putting off metalwork to finish the chassis, stuffing pcbs, procrastinating doing the internal wiring while working on another build that has also been sitting on the bench for too long, firing up the amp late at night and not daring to hook it up to the main speakers ... all that usually takes months!
Don't get used to the pace at which you just finished your first build 😀
Congrats!
Congratulations Caleb! There's nothing more gratifying than success on the first try. Best wishes for even greater enjoyment, as you take on more ambitious projects.
Very nicely done. Congrats on your successful build.
Looking at the pics, can someone remind me about the whys and wherefores of wrapping wire around electrolytic capacitors?
I see it here in this build and I remember seeing it employed in early Dynaco solid state amplifiers (ST-80, ST120 etc).
No doubt related to some form of inductance but what is the advantage of doing of wrapping the wire around the capacitor?
Is the cap simply being used as a form or is there more to it than that?
Thanks
Curt
Looking at the pics, can someone remind me about the whys and wherefores of wrapping wire around electrolytic capacitors?
I see it here in this build and I remember seeing it employed in early Dynaco solid state amplifiers (ST-80, ST120 etc).
No doubt related to some form of inductance but what is the advantage of doing of wrapping the wire around the capacitor?
Is the cap simply being used as a form or is there more to it than that?
Thanks
Curt
Last edited:
Curt,
According to the supplied schematic the wire is acting as an inductor in parallel with a 10 ohm resistor. The provided theory of operation indicated that this circuit provides load matching to allow the amp to drive a variety of loads. The attached pages explain in a little more detail. Hope this helps!
Caleb
Akitika Was based /derived from an upgrade of an ST120. No surprise that it reuses the wound on the caps 'coils' . Besides , they do their job.
That said My Kit sounds pretty darned good TBH. Not as good as my F6 but not massively less either 😉.
It's a Good 'un... enjoy it.
That said My Kit sounds pretty darned good TBH. Not as good as my F6 but not massively less either 😉.
It's a Good 'un... enjoy it.
Excellent! I am quite tempted to buy this kit. You got the regular GT-102, correct? Your speakers are 8 ohms (or higher?), right?
I would be getting the GT-102 Z4 - which comes with a larger transformer (I think?) and they simply add all the changed parts needed for the Z4, along with all the regular parts.
Which is odd, in my mind - it costs them more to duplicate some parts, AND the builder has to remove the parts that are replaced with the Z4 version's parts. So, this is a lot of room for error.
For the extra $25, it seems like they should just sell the Z4 version - and maybe call it the GT-103? Fewer parts to stock and pick and ship, no confusion or extra work for the builder, and a more flexible/capable amp, still for less than $400.
Last edited:
ST-120? What brand is that?
I have noticed the similarities of the AkitikA GT-102 with my B&K ST-140 - though the former has no bias trim pots, so there are also considerable differences.
Akitika is a sister company of update-my-dynaco. Dynaco made the ST-120, it's an all transistor power amplifier using discrete transistors. So is the B&K ST-140. The Akitika GT-102 uses the LM3886 "chip amp" instead of discrete transistors.
Question - I see the discrete diodes on the power supply board, that I am assuming are the diode bridge. Do those get hot during operation?
And what is the small square circuit board near the two amp boards, on that side of the RF shield?
I am probably going to get the DC scraper, if I get this kit - my system gets a very audible 60Hz hum/hiss at times, coming from the speakers. And I may ask AkitikA to send a second DC scraper, that I can put into my B&K ST-140.
The other amp that the GT-102 reminds me of, is the Audio by Van Alstine AVA Vision SET-120. Which is also 60W/ch, but puts out (nearly?) double into 4 ohms. It also costs $899.
And what is the small square circuit board near the two amp boards, on that side of the RF shield?
I am probably going to get the DC scraper, if I get this kit - my system gets a very audible 60Hz hum/hiss at times, coming from the speakers. And I may ask AkitikA to send a second DC scraper, that I can put into my B&K ST-140.
The other amp that the GT-102 reminds me of, is the Audio by Van Alstine AVA Vision SET-120. Which is also 60W/ch, but puts out (nearly?) double into 4 ohms. It also costs $899.
I've built two of the GT-102s and it was fun both times. The instructions are great and reminded me of the Heathkit manual for the A9-C I rebuilt.
The first GT102 I built with the volume control and I added an input sector switch with 2 extra sets of RCAs on the back. I had initially built a Rod Elliott TDA7293 amp to give as a gift but after years of wondering about the Akitika I decided at the last second to see how the GT-102 sounded compared to it and it was enough better that I gave them the GT-102 instead.
I thought I could live with the TDA7293 for my own use, but after a few months I missed the GT-102 enough that I built one for myself.
@NeilBlanchard it is my understanding that the DC scraper is to help with hum that actually comes from the transformer, not the speakers. Toroidal transformers will hum if there is DC on the line.
The first GT102 I built with the volume control and I added an input sector switch with 2 extra sets of RCAs on the back. I had initially built a Rod Elliott TDA7293 amp to give as a gift but after years of wondering about the Akitika I decided at the last second to see how the GT-102 sounded compared to it and it was enough better that I gave them the GT-102 instead.
I thought I could live with the TDA7293 for my own use, but after a few months I missed the GT-102 enough that I built one for myself.
@NeilBlanchard it is my understanding that the DC scraper is to help with hum that actually comes from the transformer, not the speakers. Toroidal transformers will hum if there is DC on the line.
Mark, thanks for clarifying - I did think of the Dynaco, but I wasn't sure. And I had heard their history, but forgot this part.
And thank you for saying how this is a "chip amp". That term makes me think of an IC, so understanding what "chip" means in this context is helpful.
Any thoughts on how it is that the GT-102 doesn't have/need and bias trim pots? Is the bias level set with part of the discrete circuit, and if so, is there any advantages / disadvantages in terms of sound quality, or longevity, etc?
It certainly makes building it easier and less touchy. I have recapped and rebiased my B&K ST-140 - it had drifted A LOT from stock specs - I think it is supposed to be ~210mA? The left channel was at about 340mA - and the right channel was about 510mA !! My black anodized heat sink is a beautiful pink/magenta, after having been run 24/7 for a good portion of the 34+ years I have owned it.
With the recapping, it now sounds better than ever. But it is getting creaky, and I am looking for a worthy / better replacement. I have a Schiit Vidar, which is fine sounding - but doesn't have the open soundstage and air and transparency and detail of the ST-140. The Vidar has better bass control and extension, so if I biamp, the Vidar on the woofers and the ST-140 on the tweeters - is a magical combination.
The AkitikA GT-102 Z4 is on my short list. Also, the ACA (as monoblocks?), the Schiit Aegir, and the AVA Vision SET-120. And even possibly the Decware Zen monoblocks?
I have an Audible Illusions Modulus 3A, so I am set for a preamp; though maybe I need a balanced preamp to go with the Aegir, or ACA as monoblocks?
And thank you for saying how this is a "chip amp". That term makes me think of an IC, so understanding what "chip" means in this context is helpful.
Any thoughts on how it is that the GT-102 doesn't have/need and bias trim pots? Is the bias level set with part of the discrete circuit, and if so, is there any advantages / disadvantages in terms of sound quality, or longevity, etc?
It certainly makes building it easier and less touchy. I have recapped and rebiased my B&K ST-140 - it had drifted A LOT from stock specs - I think it is supposed to be ~210mA? The left channel was at about 340mA - and the right channel was about 510mA !! My black anodized heat sink is a beautiful pink/magenta, after having been run 24/7 for a good portion of the 34+ years I have owned it.
With the recapping, it now sounds better than ever. But it is getting creaky, and I am looking for a worthy / better replacement. I have a Schiit Vidar, which is fine sounding - but doesn't have the open soundstage and air and transparency and detail of the ST-140. The Vidar has better bass control and extension, so if I biamp, the Vidar on the woofers and the ST-140 on the tweeters - is a magical combination.
The AkitikA GT-102 Z4 is on my short list. Also, the ACA (as monoblocks?), the Schiit Aegir, and the AVA Vision SET-120. And even possibly the Decware Zen monoblocks?
I have an Audible Illusions Modulus 3A, so I am set for a preamp; though maybe I need a balanced preamp to go with the Aegir, or ACA as monoblocks?