Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Aug 11, 2017.
Not sure if you posted an image, I do not see anything besides '
I believe he linked it wrong. img: https://i.imgur.com/Nzc7o5O.jpg
thanks - didn't see the link.
that sure looks like a filter cap , if C1 is about 10uF and C2 closer to 0.1uF - then this is likely what it is .
Thanks guys, really appreciate the responses. FYI I’m using the PSU that came with the amp.
Well, looks like I might need to open this thing back up and replace the tube socket. Both of my tubes have issues with how they are sitting in the socket, and if not sitting exactly right, it will not even light up. If I try to set the tube so that it is 'even' in the socket, I get no lights and no sound, it actually needs to be sitting back slightly.
I have probably changed the tube in this thing less than 10 times in its entire time with me, so I'm not entirely sure what is causing the issue, but if it gets any worse then I won't have much of a choice...
Check the heater voltage and make sure B+ is getting to the socket first.
It would be odd for the pins in the socket to lose contact but who can tell. There are so many different manufacturers now that they might have changed the way the pins contact with the socket. I forget how experienced you are with a soldering iron but I would be happy to take a look at this for you - just shoot me a pm.
I'm not sure I follow 100%... you mean check the B+ voltage on the socket with the tube plugged in so that it isn't heating up? The amp works fine with the tube seated slightly back from center, so I'd guess B+ is getting there, but I could open it up and check to make sure the B+ and heater pins are getting what they need. I initially blamed the socket because it happens with both of my tubes--the first time it happened with my EH, I thought the tube was going bad so replaced it with an Amperex A-frame, but then noticed the same issue.
I'm unable to read and interpret circuits except in the most general and broad terms, but I am handy with a DMM if someone is holding my hand through the troubleshooting process. And as for skills with an iron, I'm good: I've built a Crack and modded it to the point that there is very little space left inside, am in the process of building an Eros 2, have modded/recapped a few speaker amps, etc. I really do need to start learning theory so I can make heads or tails of circuit diagrams, but I'm getting off track now....
Great! I think this is purely a socket issue, you might be able to get a dental pick in the socket ( with the lid off ) and bend them to ensure better connectivity. ( obviously discharged and no residual power ) If that doesn't work, I would just change sockets - might even have some for you if you don't have a spare on hand.
I would clip the legs and remove the individual pins as opposed to trying to save the socket .
I apologize. B+ is an old vintage amp term for the DC plate supply voltage. Old vintage amp plate voltage was in series and after the first set of tubes would then be C+ and so on. This amp has constant current source and can simply be referred to as plate voltage. Pins 1 and 6. So the DC voltage between pin 1 and ground.
The way you describe it, it sounds sound like the tube socket. You can also try to bend your pins on your tubes to match what the socket wants for the time being. Unless you can bend the pins or replace the socket.
Thanks @dBel84 @Baten @gixxerwimp & @BrokeSkoolBoi. Replaced the cap and I’m back up and running, magic smoke free.
I never want to solder surface mount stuff again.
I picked up one of these because I wanted a small footprint, all-in-one, tube hybrid that I could keep on a desk while I'm working. It's the combo unit with MCTH and SDAC. Transducers are JVC HA-FD01 (James modded), KSC-75 on PortaPro headband, and HD600. I haven't had good luck with new production Electro-Harmonix tubes in other applications, so I skipped the stock tube and I'm running a NOS 6N23P-EV (Saratov). My other main headphone setups are Vali 2 + OL DAC USB, and Fulla 2, so most of the thoughts below will be in relation to them. Like the Fulla 2 DAC stage, OL DAC is AKM 4490-based (it's not the same thing as ODAC, lol). I know these massdrop units are mostly only available on the used market now, but figured these impressions might still be useful to someone. All impressions are with the stock power supply.
EDIT: My initial impressions are below, but the sonic character of this unit changed a lot after the first couple of days. You can see my updated impressions here: https://www.superbestaudiofriends.o...alli-tube-hybrid-amp.4866/page-52#post-305828
MCTH + SDAC is not as resolving as either Fulla 2 or Vali 2 + OL DAC. If you're a fiend for the micro-stuff, this is not the unit for you. This takes maybe 2 seconds of listening to figure out. I'm not sure if this is a function of the SDAC or MCTH, or some increase in noise floor due to the switcher. (Note: My Vali 2 is from ~2018, so it's not one of the early laid back ones.)
MCTH + SDAC is warmish and slightly thick. There is not a lot of top-end air, and the bass is a bit floppy and less extended in comparison to Fulla 2 and Vali 2 + OL DAC.
MCTH + SDAC does have some of that 3-dimensional tube magic that Fulla 2 can't recreate, but Vali 2 does this better.
For good quality recordings, I would rather listen to Vali 2 + OL DAC (or any competent DAC). It's a pretty big margin here for my personal preferences (living room neutral frequency response, good technicalities).
For poor quality recordings (e.g., Dookie), MCTH + SDAC is perfect. This massdrop combo unit does a good job of making shitty, compressed pop music more listenable. This is not intended as a backhanded compliment. I like listening to everything and prefer listening to bad recordings on MCTH + SDAC than Vali 2 + OL DAC. Easy choice here.
I was hoping MCTH + SDAC would have a bit smaller footprint. It's not huge, but does eat up some desk space. Still, there are very few all-in-one tube hybrids, and MCTH + SDAC seems like it's the best option under $300. One big advantage of the all-in-one package is having only one power brick and cord. I basically got this unit because my current desktop setup would be constrained by two more Schiit-style AC wall warts.
MCTH + SDAC gives me kind of vintage Hi-Fi vibes. Like listening to my Dad's garage sale receivers as a kid in the 90's. Those memories are distant, but it's evocative of those experiences. Again this is not a backhanded compliment or faint praise, I think it's kind of a cool and endearing trait of MCTH + SDAC.
Summary: For me, the main selling points of MCTH + SDAC are that it's a relatively small all-in-one that does a really nice job with marginal recordings. If the slightly sterile, flat quality of opamp-based headphone amplifiers bothers you, and you're ok with sacrificing resolution to fix it, then MCTH + SDAC could be an option. I personally would only consider it in desktop applications. For budget-oriented main system listening, I think Vali 2 plus a good DAC, like Modi or Modius, is a better choice. The redeeming quality of MCTH + SDAC is that it's forgiving of less than perfect recordings, and does a nice job of emphasizing the music over the gear. Not technically excellent, but kind of addicting listenability.
A brief update on my experience with MCTH + SDAC. I bought my unit on Ebay, assuming that it had been burned in already. Turns out it was basically brand new, and the sonic character changed a lot after the first ~2 days. Here is a summary of the deltas after burning in:
Much more resolving and better microdetail. Easily on par with Vali 2 in this area. No longer sounds slightly thick.
The frequency response tilted, so it's definitely not on the warm side. Neutral, if anything slightly cool.
As a result of the above, it's much more revealing, and no longer forgiving of bad recordings :-(
The vintagey-ness that I initially found endearing about MCTH + SDAC is gone.
So if you buy one of these, give it 2-3 days of being on playing music before you make any real judgments. For me the overall verdict hasn't changed much. I still prefer Vali 2 and a separate DAC. I kind of wish I could get that warmish and slightly thick sound back that I was first hearing from MCTH + SDAC. I rolled a few tubes including the GE 5670 (w/ adapter), but MCTH sounds pretty much the same with any of the compatible tubes I tried. Combined with the footprint being a bit too big for my workspace, I will be putting this unit up for sale soon.
If you’re willing, there may be another option. You can use the 6c8g tube and will give you a more open and tubey sound. You’ll have to buy a socket saver, a 6c8g to 6922 adapter, and the 6c8g tube (Sylvania is a good start). All this will total around $75 - $100 depending on the tube cost.
Hmm I’ve been thinking about adding a 6sn7 or 6f8g onto mine but not sure if that’s compatible. I’m thinking I’ll need a good linear power supply for it? Have a socket saver but afraid it’ll get stuck given theres no clearance an doesn’t protrude if I put it in lol. Might need to find a taller one? Is there a list of tube / adapters recommended or against for the mcth?
then again maybe I’ll just buy the vali 2 again. I had rolled the 6f8g/vt99 on it before with the stock wallwart and it was nearly as good as the super7. If only the pot was bigger on that
You won’t be able to run 6SN7 tubes as it pulls too much amperage. The 6C8G falls in line with what the 6922 can pull and is safer.
Ah, will i likely damage the amp if I run it with 6sn7 with a linear power supply? I just bought another mcth and the seller has been running it with adapters for 12a*7, 5670 adapter to run we396a, and Adapters with 6sn7 tubes.
What about 6f8g? Or is it much safer to run it with 6c8g tubes? If so I’m gonna order some adapters & tubes from eBay lol
ideally I’m hoping that it’ll run fine with all those variants as long as I’m running it with a linear power supply (an acopian A28MT500).
An Acopian still won't change the tube circuit amperage. It's not the best idea, long-term.
Do you think it was the tube or SS parts (amp and/or DAC) of the circuitry that burned in? I found the sound to vary quite a lot with tubes (impressions somewhere further back). My favourite is the TFK E88CC.
Good question, most likely a combination. Pure speculation, but maybe the interstage capacitors needed some burn-in time to open up. Thanks for sharing your experience with tube rolling. Using the magic 8-ball, I don't think tube rolling will change my overall opinion much. I rolled the stock tube, a NOS 6N23P-EV, and a GE 5670 with adapter. The differences were subtle, an order of magnitude smaller than the sonic changes I observed rolling tubes in Vali 2. If no one buys my combo unit, I will turn it into a little project. My hunch is that rolling interstage capacitors would make a much bigger difference than rolling tubes. To my eye, it looks like they used some cheapo knockoff WIMA caps. (Edit: They're WIMA, see dBel's post.) I wouldn't spend more than a few bucks, but I'm curious if those green Russian PIO caps would sound any better.
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