penmarker
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Posts posted by penmarker
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11 hours ago, Pars said:
Did you remove or re-install these after bringing the amp out of storage? From your pic above, pin 1 doesn't seem to be clearly marked, so the potential for putting these in backwards is there. Also, have you tried it with the THAT340s?
Nah these were left on during storage. I don’t think I’ve put them in backwards, will they work if they’re put in backwards?
Just checked I can’t see the pin1 marking on these. Hmmm yeah it’s possible I put them in backwards. Also the pins has some green colour like copper tarnishing. It came off by rubbing.
The THAT340’s are working fine. Though they’re noisy with some minor intermittent frying sound. With my low sensitivity headphones and as a pre out the noise isn’t audible.
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Started this project on 2018 I believe. Was a penny pincher because of budgets so cut a lot of corners. Ultimately this isn’t a project you’d want to cut corners. Finally went around finishing it this week because my area got into lockdown and I’m desperate to get myself preoccupied. Ordered some parts and went ahead to redo and finish it.
Initially I built it in one case but the transformer was inducing noise into the board. With the whole PSU (including small 12v transformer for channel selector) rehoused in a separate chassis it’s silent. The amp is being powered by a single GRLV for now. PSU output devices are bolted to the chassis heatsink and only gets somewhat warm.
The amp bottom right obviously has canted headphone/XLR outputs because I used a hand drill to make mounting holes and made a mistake with the angle.
The dynahi makes a great sounding preamp too.
One question I have is I got some C3881/A1349 to replace my noisy THAT340, and after storage for a year or so they got distorted. These were bought from a reputable seller in diyaudio. Anyone has any idea what happened?
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Apple fucked up with the case but since it uses only magnets to put the headphones to sleep there’s a few nice cases around that does the job.
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Rewatching Doc Martin
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I bought a case off Aliexpress with the same switch, with the exception of a translucent ring around the switch nub head. With the ring the clearance is better but the hole could've been half a millimetre smaller though.
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I'm planning to add a relay channel switch in my dynahi that runs on 12v. Will there be any drawbacks if i tap into one of the outputs with R1 = 110Ω, R2 = 75Ω for 12.162Ω?
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On 11/2/2018 at 7:46 PM, kevin gilmore said:
Does that mean you only require either u1/ic2, or they can both be fitted?
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On 2/2/2019 at 1:31 AM, spritzer said:
I just put together the amp and Fang should really fire everybody in the "Hifiman Boston design team" for coming up with this shit. So there is really no good way of assembling this as you can't just put on the front or the back first and connect the internal wires. Nope, they have to hang off at the same time while trying to connect the fiddly connectors. Fucking hell...
It will be fun for them to service this shit...
"You're not supposed to service it yourself. Leave the servicing to experienced professional personnels from Hifiman."
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Sounds like planned obsolescence.
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Oh ok that's interesting. I've recently replaced the THAT in my DynaHi with a pair of 2SC3381-GR/2SA1349-GR and I noticed the gain dropped a lot. Does changing the pot value apply there too? (Sorry for being off topic)
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HD700 is extremely polarizing so make sure you try them out first. I know so many people who wouldn't even want them even for free.
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To those who missed the TKD group buy, I got a pot from here.
https://www.ebay.com.my/itm/283057880224
A Vietnam builder referred them to me, said they are genuine, I've yet measured the channel matching. But from build quality and feel alone its really good.
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Thanks everyone. I've discussed this with some friends and we all agreed its very uncommon if they exist at all. My case already has IEC mounting hole but I'll be using external PSU. I'm planning to just cut a rectangle out of some plastic/acrylic/pcb, sand & spray, then mount from the inside.
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Does anyone know where can I get blanking plates for IEC inlet holes? I found blanking plates for XLR is pretty common but I can't find any info for IECs. Do they even exist?
Attached is the blanking plate for XLR
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Goddamn sorry wrong post and wrong thread.
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Regarding GRHV, is there a drop in replacement for C2M1000170D? They're on backorder on most major sellers.
**Edit
Never mind guys, found out they get out of stock every few months. SCT2H12NZGC11 is also on backorder now and still don't know if FQFP8N80C is a good replacement.
I guess I'll just wait.
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I've compiled a BOM from Digikey for the supplied GRHV based on my silkscreen from the recent group buy board. I hope others can help check if I missed anything.
https://docs.google.com/spreadsheets/d/1XMu81oWk6E3mXPW6ahhEuvmhg4U497F5I5W6JPQgnNo/edit?usp=sharing
You might notice there's RES 90.9K and RES 1.10K, these are because I can't find 92K resistors sold without MOQ.
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People are gonna kill themselves building it
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That's a beauty right there. Kinda regret not getting the cases since the boards has no standoff mounting holes.
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The group buy is the first one, cool that means it's the correct version. I was counting the tube pinouts counter clockwise.
I'll try looking for a suitable buffer stage.
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Gonna build this from the group buy soon,
On the board the silkscreen says "tube mounts on the back side of the board" but tracing the boards shows it's the same version as the one in first post. So tubes should be mounted from the top?
I also have never built tube amps so I might be wrong.
some questions I have:
1. How hot is the mosfet on PSU will be? Will heatsinking with chassis floor (3mm aluminum) suffice or does it need heatsink?
2. LT1085 require heatsinks or not?
3. Will it make a good preamp? Do I need to watch/match it's output impedance to the amp's input?
4. How to bias it?
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Boards received today, thanks a lot!
Do update us if there's leftovers.
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Thanks a lot steve, got the delivery notification in my email.
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Heheh. Booger eating moron.
KG Balanced Dynahi build discussion thread
in Do It Yourself
Posted
I've inserted the SA1349/SC3381 correctly this time, the square pad is less visible now after filled with solder but can still be identified. They sound fine, although they do have the same slight scratchy noise sound the THAT340 developed. It's intermittent and I only notice it in the right channel for now.
Maybe its time to try out the K170/J74. The noise floor on the SA1349/SC3381 is similar or slightly lower than the THAT340 and I can hear it on sensitive cans. How does yours sound?
I'm very glad I built the Dynahi, they sound better than everything else I've listened before.