[L0rdGwyn]

So I bought a pair of GEC KT88 at an auction and one of them was bad, made a cracking noise at power on while volume pot at zero, quickly switched off, replaced the tubes, and now I can hear really low volume in my headphones when volume is all the way down at zero? This didn’t happen before. The amplifier still sounds great and no noise at all when no music playing.. is it possible that I damaged some resistors or something?

Typically a low volume when the control is down would indicate an issue with the volume pot, although it's hard for me to see how a bad power tube would have affected it. You could try replacing the Alps pot. Did you smell anything burning from the amplifier when this happened? Also were the tubes tested by the seller?

 

[UntilThen]

No amplifier pictures allowed on this thread except Aegis, house rules.

JK I'm out and about at the moment, if someone can find EL12 spez triode curves I can say if they are compatible. I would be surprised if not, I think every pentode we've discussed has been compatible except for one. EL12 spez would need an adapter.

Competition makes the world a better place.

Can Aegis use KT88, 807 and EL156?

 

[L0rdGwyn]

Competition makes the world a better place.

Can Aegis use KT88, 807 and EL156?

Yup.

 

[henrix]

Typically a low volume when the control is down would indicate an issue with the volume pot, although it's hard for me to see how a bad power tube would have affected it. You could try replacing the Alps pot. Did you smell anything burning from the amplifier when this happened? Also were the tubes tested by the seller?

No smell, tubes was not tested by seller.. lesson learned only buy from reputable sellers..
The amp is working great otherwise, can measure the pot and the testing points to verify later

 

[L0rdGwyn]

No smell, tubes was not tested by seller.. lesson learned only buy from reputable sellers..
The amp is working great otherwise, can measure the pot and the testing points to verify later

Yes, putting untested tubes in an amplifier you are playing with fire (literally). Need to go into a tester first. If no smell it's unlikely any resistor was damaged, but you can visually inspect the interior. The low volume is in both channels, or just the one the bad tube was in?

 

[henrix]

Yes, putting untested tubes in an amplifier you are playing with fire (literally). Need to go into a tester first. If no smell it's unlikely any resistor was damaged, but you can visually inspect the interior. The low volume is in both channels, or just the one the bad tube was in?

Both, though minimal with my atrium, a little more with my test headphones FIIO FT3..

 

[DenverW]

Both, though minimal with my atrium, a little more with my test headphones FIIO FT3..

Without having the ability to troubleshoot with you, my humble thoughts are this is not related to the noise from the tube. Has anything else changed? For example, have you recently been rolling in power tubes or others that may affect the volume that weren’t in there when you remember this not happening previously? Have you checked with the gain switch at the back on both settings?

Just some thoughts, but it seems unlikely that a tube is the culprit of both channels now experiencing some volume at zero on the pot. Is it possible that previously it wasn’t noticed due to things like different tubes powers being used, lower gain switch, higher impedance headphones before?

 

[L0rdGwyn]

Without having the ability to troubleshoot with you, my humble thoughts are this is not related to the noise from the tube. Has anything else changed? For example, have you recently been rolling in power tubes or others that may affect the volume that weren’t in there when you remember this not happening previously? Have you checked with the gain switch at the back on both settings?

Just some thoughts, but it seems unlikely that a tube is the culprit of both channels now experiencing some volume at zero on the pot. Is it possible that previously it wasn’t noticed due to things like different tubes powers being used, lower gain switch, higher impedance headphones before?

I agree, I think it's pretty unlikely the bad tube caused an issue with the pot. The most likely way to fix the issue is to just replace it. As I said, I would also inspect the interior and make sure nothing appears damaged.

 

[L0rdGwyn]

Shipping Aegis to CanJam Dallas tomorrow. Sending along Brimar 5R4GY, RCA 5691, and Mullard EL34.

 

[Wes S]

Shipping Aegis to CanJam Dallas tomorrow. Sending along Brimar 5R4GY, RCA 5691, and Mullard EL34.

Heck yeah! I am familiar with those tube's "house sounds", and can't wait to hear it.

 

[L0rdGwyn]

Heck yeah! I am familiar with those tube's "house sounds", and can't wait to hear it.

Shipped it off yesterday, let me know what you think!

 

[henrix]

Without having the ability to troubleshoot with you, my humble thoughts are this is not related to the noise from the tube. Has anything else changed? For example, have you recently been rolling in power tubes or others that may affect the volume that weren’t in there when you remember this not happening previously? Have you checked with the gain switch at the back on both settings?

Just some thoughts, but it seems unlikely that a tube is the culprit of both channels now experiencing some volume at zero on the pot. Is it possible that previously it wasn’t noticed due to things like different tubes powers being used, lower gain switch, higher impedance headphones before?

actually I been running Saratov mil. grade 6P3S-E (@L0rdGwyn are they ok to run on the aegis?) that should equal 6L6 tube but perhaps some difference, though they do sound phenomenal… I will try with the JJ KT77 tomorrow and see..

 

[nonamerat]

I'm excited to start this project! I first heard the Aegis (prototype?) at CanJam SoCal 2022 in the ZMF room. I loved listening to it at the show and it really stood out compared to conventional commercial options. I am blown away that this project is shared openly. I'm very appreciative of that. I casually followed this thread for a little bit but then got occupied with other life things and only recently started to check back in on the progress. I'm happy to see the project is completed and that so many are enjoying the amp.

I spent the time to read this entire thread and the manual to make sure there are no surprises. I'm prepared for long lead times for parts, but I am in no real hurry and it's nice to have a project to pick away at over a few months. Parts ordering has started this weekend!

 

[L0rdGwyn]

actually I been running Saratov mil. grade 6P3S-E (@L0rdGwyn are they ok to run on the aegis?) that should equal 6L6 tube but perhaps some difference, though they do sound phenomenal… I will try with the JJ KT77 tomorrow and see..

Yeah those should be fine based on some triode curves I found.

 

[dietrdeb]

The project is up on diyAudio. Note that you will need to make an account there to download the gerber files (accounts are free).

Aegis DIY Tube Headphone Amplifier: https://www.diyaudio.com/community/threads/aegis-diy-tube-headphone-amplifier.399473/post-7354944

Please read the document carefully, there is a LOT of information. Reviewing all of the steps may help you decide whether or not you are capable of building the amplifier.

I've notified Holger at Erhard Audio, Dave at Landfall Systems, and Brian at ELMA that the project is being released. Please be patient with Dave at Landfall, there may be a lead time on getting the chassis if he gets slammed with orders.

I'm creating a thread for an upcoming DIY project I am working on, a tube headphone amplifier called the Aegis (pronounced EE-jis). This is a true DIY project, anyone taking on this project would assume full responsibility for acquiring parts, building, and testing the amplifier, although I will be available for questions and guidance if need be. I've placed a very high priority on making this design easy to build with a large portion of the circuitry on a PCB.

At a high level, the power supply is tube rectified, CLCRCRC filtered. The circuit features a choke-loaded 6SL7 input stage, capacitor-coupled to a triode-strapped pentode output stage. The output topology is a transformer-coupled cathode follower, which at this time is the only headphone amplifier of this topology that I am aware of. There is no silicon in this circuit, it is an "old school" tube amplifier design featuring Lundahl transformers and chokes. The amplifier includes a high and low output impedance switch for the purpose of matching high and low impedance headphones.

Tubes for the amp:
-Rectifier - 5V / 2A types; GZ34/5AR4, 5V4/GZ32, 5R4, 274B. 5Y3 can also be used with lower current output tubes like 6V6.
-Inputs - pair 6SL7
-Output - pair power pentodes; 6V6, 6L6, EL34, EL37, KT66, KT77, KT88, 6550. Others as well, compatibility list in progress.

I am currently putting together materials for the project which will include the following:
-Full build of materials (BOM) document with part numbers, prices, and where to source
-Information on ordering the chassis
-PCB gerber files and information on how to order (for those located in the CONUS, I may hold a stock of these PCBs and ship them to individuals on request, more to come on that)
-Project build document that will include amplifier schematics, information on sourcing parts, step-by-step build instructions, testing procedures

This is a relatively expensive design! Pricing of all of the parts is approximately $2,000 USD. However, this is meant to be a TOTL tube headphone amplifier, an equivalent design on the commercial market would be at least 3x the price. Regardless, the project should not be taken on by those who are not willing to commit the time and cost. This amplifier was recently at CanJam SoCal in the ZMF room and there are some forthcoming reviews. Hopefully Head-Fiers will then be able to determine if this is something they'd like to pursue.

At the time of my writing this, I am waiting to receive a second chassis and set of Lundahl components to build a second Aegis for the sake of creating the build document. I anticipate I will have the project posted in its entirety by the end of January at the latest. I will update here as the project develops, it is likely the major documentation and files will be hosted on a thread at diyAudio.com, which will be linked here.

So... I built this. Excellent instructions, even a total novice, like myself, had no trouble putting it together. I have, in the past, used a McIntosh C52 preamp as a headphone amp, and a McIntosh MHA200. Both were good, really good in fact. However, this thing edges them both out. It has a musicality that simply blows me away. The soundstage is not quite as large as the C52, but the details are a bit better. I have only used them with some Focal Stellias, because that is all I own at the moment, but it is a great pairing. Vocals are stunning, and as so many have pointed out, the background is dark. Very dark. I found Gold Lion KT77's work best with the Stellias. I am using a Mullard GZ34 Blackburn 4 notch rectifier, and two RCA 5691s as the inputs. WELL DONE L0rdgwyn...well done!