Millett "Starving Student" hybrid amp
Oct 25, 2009 at 1:16 PM Post #4,036 of 7,277
Quote:

Originally Posted by Fishline /img/forum/go_quote.gif
Tom: Thanks very much for sharing your wisdom. However, none of the ones you linked to are in stock at Mouser. All the UPWs are on order, and the only UKW that they have in stock is this 1000uF (UKW2A102MHD):
UKW2A102MHD Nichicon Aluminum Electrolytic Capacitors - Leaded
It's rather big (18x40mm) and I'm not sure if I can fit four of these guys in the case I'm planning to use. I guess I should consider a different source for caps at least.



Then pick the 470uf's. Sorry, but you really do have to put a bit of effort in this. There are more caps available than we can shake a stick at.

Quote:

I'm confused now: The Muse ES 220uF 16v is what I read in the modified BOM on diyforum, with link to beezar.com, and note in the spreadsheet about also being available from handmade audio. If that's not the correct one to use, perhaps that BOM should be edited?


No, the BOM doesn't need to be edited - only understood.
wink.gif


There are three sets of electrolytic caps used in Dsavitsk's PCB. However, the cathode bypass caps are optional. That's why I assumed you were talking about the output caps. In the early renditions of the SSMH, the output caps were the same as the power caps. Fair enough. However, the first choice would be to upgrade the output caps to something of an audio quality. That's where my comments were directed.

It's true that the Muse ES are recommended for the cathode bypass caps, but that's the third priority in the string of requirements and AFAIK, no one has used them on a P2P design. So, please forgive me if I thought you were talking power caps first, then output caps second.

If you are wanting to try the cathode caps, but not purchase an audio-quality cap (Nichicon KZ's are available at Mouser and the cathode cap need only be rated for 16V), then any old 220uf 16V cap will do. However, almost all of these will "sound" better if you use some Wima film caps for bypasses (MKP10). Quote:

If I can't get the caps from mouser (within reasonable time, at least), I guess I have to split the order up. If anyone has suggestions on where/what to get for the caps, I'd appreciate it.


Do some more work. Stick with UPW's or UHE's from Mouser. You need at least a 63V rating for the power caps and output caps. It would help if the power caps are at least 680uf's and the output caps should be at least 470uf. There are a lot of options under those requirements.

Quote:

Also, any recommendation on the wires? I used cat5e cables on my first build, but found the insulation too easily melted when soldering.


You won't like this answer, because it requires another source and separate shipping charges, but John's Wire Shop (navshipps) on ebay is an excellent source for SPC teflon-insulated wire (doesn't melt when you solder it). 22ga is the best all-around size, IMHO.
 
Oct 25, 2009 at 6:41 PM Post #4,037 of 7,277
Quote:

Originally Posted by tomb /img/forum/go_quote.gif
...and AFAIK, no one has used them on a P2P design


FYI, I did. It's a 90 cent upgrade, why the hell not?

BTW, I agree with fishline on the shipping stuff, but in this case, beezar ships things really cheaply, and some of their items are cheaper than on mouser. (IIRC).
finally, if you ever plan on making a bantamDAC, you would need to order from there anyway. so, you might as well just get the PCB for that now, and the shipping loss will be negated.
 
Oct 25, 2009 at 7:45 PM Post #4,038 of 7,277
I finally had a chance to finish the SS kit I bought from royewest (THANKS!). I am unbelievably happy with it. I can't thank you guys enough for the design, pcb, kit, etc. At the same time, I blame you all for assisting my continuing slide down the slippery slope of audio.
darthsmile.gif


I did make the mistake of putting the 50k resistors in with the 100k ohm pot. I still am getting good volume, though I might go back in and switch them out. I also left out the socket LED. How can you say no to the tube glow? Toss in the case...mmmmm, tasty.

I'll have to give the p2p version a shot at some point.
 
Oct 26, 2009 at 10:39 PM Post #4,039 of 7,277
Followup to static/noise problem.

The static indeed follows the tube, so that's probably damage done by the 48V I shot through it. Time to find a replacement tube.

The noise at a regular interval doesn't follow the tube and stays on the right channel.
 
Oct 27, 2009 at 2:51 AM Post #4,041 of 7,277
Quote:

Originally Posted by tomb /img/forum/go_quote.gif
Then pick the 470uf's. Sorry, but you really do have to put a bit of effort in this. There are more caps available than we can shake a stick at.

the first choice would be to upgrade the output caps to something of an audio quality.

Do some more work. Stick with UPW's or UHE's from Mouser. You need at least a 63V rating for the power caps and output caps. It would help if the power caps are at least 680uf's and the output caps should be at least 470uf. There are a lot of options under those requirements.



Thanks again, Tom. I don't mind doing more work at all, but am just completely ignorant about which ones would pass as "audio quality". I gather from your comments that any UPW or UHE with at least 470uF/680uF and 63v would do. Between the two (UPW vs. UHE) is one better than the other? I've found UPWs for both 470uF/63v (UPW1J471MHD6) and 680uF/100v (UPW2A681MHD). Unless I see more comments about them, I'll go with these.

Quote:

If you are wanting to try the cathode caps, but not purchase an audio-quality cap (Nichicon KZ's are available at Mouser and the cathode cap need only be rated for 16V), then any old 220uf 16V cap will do. However, almost all of these will "sound" better if you use some Wima film caps for bypasses (MKP10).


Again, it's not that I don't want to get audio-quality, but that I don't know what's audio quality and what's not, so your guidance is much appreciated. I take it that the cathode caps aren't important to be audio quality, so as long as they are 220uF/16v, they would work. Just to make things as explicit as I can: Do you mean all three pairs (power, output, and cathode) will benefit from addition of film bypass caps such as Wima MKP10? If so then I'll get some extra Wima MKP10s. (I was planning on using them to bypass the output caps, as indicated on the modified schematic/bom.)

Quote:

You won't like this answer, because it requires another source and separate shipping charges, but John's Wire Shop (navshipps) on ebay is an excellent source for SPC teflon-insulated wire (doesn't melt when you solder it). 22ga is the best all-around size, IMHO.


No, I don't mind the separate shipping here because I'm not getting just enough wire for SSMH, but plan on getting more for future projects (am thinking of possibly gamma2...). Thanks for the pointer!
 
Oct 28, 2009 at 12:49 AM Post #4,042 of 7,277
Quote:

Originally Posted by Fishline /img/forum/go_quote.gif
Thanks again, Tom. I don't mind doing more work at all, but am just completely ignorant about which ones would pass as "audio quality". I gather from your comments that any UPW or UHE with at least 470uF/680uF and 63v would do. Between the two (UPW vs. UHE) is one better than the other? I've found UPWs for both 470uF/63v (UPW1J471MHD6) and 680uF/100v (UPW2A681MHD). Unless I see more comments about them, I'll go with these.


OK - let's back up. I'll try to explain some of the empirical practices that many of us have learned and discovered. Note that none of this is necessarily prove-able with technical expertise, but is more of an experimental experience about what works and what doesn't.

There are three types of potential electrolytic capacitor usage in tube and tube hybrid headphone amps:
1. Power and ground de-coupling
2. DC-filtering of the audio signal
3. Cathode bypassing, (audio signal related)

In the Starving Student, the following caps fit in those categories:
1. C1 and C6
2. C3 and C5
3. C7 and C8.

In the case of #1, low ESR and high ripple ratings are best. The caps that excel in these specs that are available at Mouser are Nichicon UPW's and UHE's. Generally speaking, the UHE's are better, but this is inconsistent. You'd have to check each size to be sure - sometimes the UPW's are better. Certainly, UPW's are not "bad" in comparison and many builders quite successfully choose UPW's and don't worry about the trouble of making a comparison. IOW, you can't go wrong with either one.

In the case of #2, every bit of the audio signal passes through these caps. Therefore, the best choice for these caps is to find ones that are audio quality. Note that the power caps that apply to #1 above are not necessarily the best sounding caps. So, two different uses means two different types of caps if you want to optimize things.

The one exception to this rule is bypassing. It's quite possible through bypassing to make a somewhat bad-sounding power-type cap to sound reasonably good by using bypass caps. Bypass caps usually mean small film caps sized at 0.1 to 0.47uf, but this is highly variable. Many of us have simply settled on 0.22uf out of convenience. Note that bypassing doesn't always work - sometimes the combinations are bad, while others are fantastic. Generally speaking (very generally), bypassing with Wima MKP10's are usually dependable in results. Vitamin Q's make even better bypass caps, but they are nowhere near as convenient.

If you want greater detail into this practice, study Dsavitsk's excellent reference: Notes on Output Coupling Caps. Also, refer to Humble Homemade Hi-Fi for notes specifically on different bypass caps.

Finally, case #3 - this cap is used to bypass the cathode on the tube. In simplest terms, I usually think of it as providing extra headroom for the bottom (negative) half of the signal wave. My experience has been that this cap can positively or negatively affect the bass response in a tube/tube hybrid amp. Of all the boutique electrolytic caps available (Black Gates, Nichicon KZ's, FG's, Elna Cerafines, RFS Silmic, etc.), Nichicon Muse ES caps are most known for bass response. At the same time, ES caps are bi-polar, meaning that they should allow the signal to move in both directions just as easily - a perfect application for bypassing the tube's cathode, where the signal wave is fluctuating up and down (positive and negative) on a constant basis.

This is why we select Muse ES as the first choice cap in that position. Others will work, but again, you may want to bypass them with a good Wima or similar. One thing to remember though, unlike the output coupling caps in #2, not all of the music signal necessarily goes through these caps - only when the signal wave hits a certain amplitude. So, the differences in quality of the caps are not as pronounced in their effect as with #2.

Quote:

Again, it's not that I don't want to get audio-quality, but that I don't know what's audio quality and what's not, so your guidance is much appreciated. I take it that the cathode caps aren't important to be audio quality, so as long as they are 220uF/16v, they would work. Just to make things as explicit as I can: Do you mean all three pairs (power, output, and cathode) will benefit from addition of film bypass caps such as Wima MKP10? If so then I'll get some extra Wima MKP10s. (I was planning on using them to bypass the output caps, as indicated on the modified schematic/bom.)


Yes, all three pairs might benefit from bypass caps, but the ones at the output coupling positions will have the most effect. It's questionable whether the difference would be audible in the other two cases (for this amp).
Quote:

No, I don't mind the separate shipping here because I'm not getting just enough wire for SSMH, but plan on getting more for future projects (am thinking of possibly gamma2...). Thanks for the pointer!


Good. You won't regret dealing with John's wire shop on ebay. Just check the insulation thickness and get the thinnest kind he has. Don't buy the twisted pair. Also, stay away from the Kapton insulation kind. If he doesn't have what you want (22ga SPC Teflon-coated, single multi-strand wire), send him a message through e-bay. Most likely, he'll make a special listing that you can buy from.
 
Oct 28, 2009 at 2:01 AM Post #4,043 of 7,277
Geez, Tom! Your generosity in sharing your knowledge is just amazing! Can't thank you enough for all the help and the education. Now I feel like I'm seeing more light on the subject, instead of blindly following instructions (which is basically how I built my first SSMH). I will surely read up Dsavik's notes on output caps.

I will take my time to put everything together. With the first one, I simply used my cordless drill and whatever bits I have to do drill the case, and it is barely passable. With the second one, I ordered a proper case (instead of recycled tin) and plan to use a stepped bit. I don't think I want to go as far as getting a drill press, but the drill guide I found on amazon looks like it should do OK. I've got some used CPU heatsinks that I'm planning to use. Will have to figure out how to fix the MOSFETs to the CPU heatsink.

It may take a while, but I'll try my best to report my progress (or lack thereof).
 
Oct 31, 2009 at 12:46 AM Post #4,046 of 7,277
Quote:

Originally Posted by acvtre /img/forum/go_quote.gif
I'm a noob and I wanna build a cheap but good sounding hybrid amp. Do you think is better the SSMH or the millet max?


Look - this puts me in a bad position, since I sell both of them and the different designers are all friends. That said, I've built more of both than anyone (4 SSMH's, 4 Millett Hybrids w/DB's, 4 MiniMAXes, 7 Maxes), so I think I can speak with authority on the matter.
wink.gif
IMHO, the performance of both amps is proportional with the cost. The proportionality is that the SSMH is half the cost of a MAX/MiniMAX. Some of that price difference exists in a greater feature set on the MAX/MiniMAX, but still - something to consider in the price difference. At the same time, there's probably no tube or tube hybrid amp that is cheaper and simpler with great performance than the SSMH.

To be more descriptive, while both amps do well with all kinds of phones, you will find that the MM/MiniMAX probably has a greater advantage with mid-to-lower impedance phones, while the SSMH has a greater advantage with high impedance phones, but each has enough current and voltage swing to handle both impedances authoritatively. The SSMH is definitely more "tubey", with emphasized mids, a very dark background but with somewhat rolled off highs and lows, while the MM/MiniMAX has much more of a flat-response, with solid-state-like detail & slam - but with distinctly unique tube flavoring.

There are those that disagree with my opinions, however. Some people have listened to one or two instances of the above with somewhat esoteric phones and have made sweeping statements in complete contradiction. I make mine based on the phones that I have and use almost constantly: KSC-75, Portapros, PX-100, Grado SR225, HF-1, and HF-2, Sony V6, Sennheiser HD25-1 II, HD580, HD600, AKG 701, and Fostex T50RP. I've also had my hands on a couple of other orthos from time to time (graciously loaned by cetoole). So, please measure my response accordingly in that context.
smily_headphones1.gif
smily_headphones1.gif


EDIT: Ordinarily, I thoroughly despise requests for amp comparisons, but I seem to be losing that battle around here. Please don't ask me to compare against something I don't sell.
 
Oct 31, 2009 at 3:50 AM Post #4,047 of 7,277
Quote:

Originally Posted by acvtre /img/forum/go_quote.gif
I'm a noob and I wanna build a cheap but good sounding hybrid amp. Do you think is better the SSMH or the millet max?


Keep in mind that if you can't find the 19J6 tubes, you'll have to do one of the variants posted in the thread. But that means changes to the tube socket and resistor values, so it won't be as straight forward a build.
 
Oct 31, 2009 at 9:07 AM Post #4,048 of 7,277
Quote:

Originally Posted by tomb /img/forum/go_quote.gif
Look - this puts me in a bad position, since I sell both of them and the different designers are all friends. That said, I've built more of both than anyone (4 SSMH's, 4 Millett Hybrids w/DB's, 4 MiniMAXes, 7 Maxes), so I think I can speak with authority on the matter.
wink.gif
IMHO, the performance of both amps is proportional with the cost. The proportionality is that the SSMH is half the cost of a MAX/MiniMAX. Some of that price difference exists in a greater feature set on the MAX/MiniMAX, but still - something to consider in the price difference. At the same time, there's probably no tube or tube hybrid amp that is cheaper and simpler with great performance than the SSMH.

To be more descriptive, while both amps do well with all kinds of phones, you will find that the MM/MiniMAX probably has a greater advantage with mid-to-lower impedance phones, while the SSMH has a greater advantage with high impedance phones, but each has enough current and voltage swing to handle both impedances authoritatively. The SSMH is definitely more "tubey", with emphasized mids, a very dark background but with somewhat rolled off highs and lows, while the MM/MiniMAX has much more of a flat-response, with solid-state-like detail & slam - but with distinctly unique tube flavoring.

There are those that disagree with my opinions, however. Some people have listened to one or two instances of the above with somewhat esoteric phones and have made sweeping statements in complete contradiction. I make mine based on the phones that I have and use almost constantly: KSC-75, Portapros, PX-100, Grado SR225, HF-1, and HF-2, Sony V6, Sennheiser HD25-1 II, HD580, HD600, AKG 701, and Fostex T50RP. I've also had my hands on a couple of other orthos from time to time (graciously loaned by cetoole). So, please measure my response accordingly in that context.
smily_headphones1.gif
smily_headphones1.gif


EDIT: Ordinarily, I thoroughly despise requests for amp comparisons, but I seem to be losing that battle around here. Please don't ask me to compare against something I don't sell.



Really interesting. Now the questions are, how much do the both kit-amps cost? And which one could be better for me considering that I almost can't read a schematic, so I need a step-by-step guide.
Can I roll the tubes with the MM? I've also found a pic of the last version of the MM with the space for the Bantam DAC, THAT'S REALLY COOL!

P.S.: for now I've got a AKG k240 mkII
 
Oct 31, 2009 at 12:18 PM Post #4,049 of 7,277
Quote:

Originally Posted by acvtre /img/forum/go_quote.gif
Really interesting. Now the questions are, how much do the both kit-amps cost? And which one could be better for me considering that I almost can't read a schematic, so I need a step-by-step guide.
Can I roll the tubes with the MM? I've also found a pic of the last version of the MM with the space for the Bantam DAC, THAT'S REALLY COOL!

P.S.: for now I've got a AKG k240 mkII



The Step-by-step guide for the Starving Student is in my signature.

There are threads for both the MAX and the MiniMAX - we need to keep discussions/questions about those over there.
wink.gif
 
Oct 31, 2009 at 7:38 PM Post #4,050 of 7,277
Quote:

Originally Posted by acvtre /img/forum/go_quote.gif
<snip>
Can I roll the tubes with the MM?
<snip>



Not exactly. Rather there are three different 'versions' of the circuit, using completely different tubes. This different tubes are not interchangeable, that is, you cannot plug tube A into an amp version built for tube B; this for a variety of reasons that range from the mechanical (e.g. the tubes use different sockets) to the electrical (different pinout, current requirements, etc.)

Still, given that you mention that you are not very proficient in reading schematics, I strongly recommend you build the Beezar.com version using 19J6 tubes and a printed circuit board (PCB). You'll have to keep an eye on this thread and on Beezar.com for TomB's announcement of kit availability. The kit might be a little more expensive than what you originally could have had in mind for this project but it's an OUTSTANDING value: easy to build, beautiful case, good quality components, in a word: great. Just take a look at the step-by-step build thread here.


If you're still interested in building any of the two alternate tube version, for which no PCB is available, search the thread for 12SR7 and 12AU7.

cheers!
 

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