OK so today I switched to CD (Fleetwood Mack - Mr. Wonderful) and a Sony MDR-7506 (impedance 63 Ohms) and the sound is great! Voices are very crisp and clear, basses are deep and the soundstage is wide. Keep experimenting!
Ok, so, I switched it on today to try and fix it and it works almost perfectly. Just like that. I imagine it's a bad solder joint and I'm just lucky right now? Anyway, the base is pretty thin both on my low impedance in-ears and on my DT880 600 Ohms. There's a volume independent hum in my in-ears which is not present on my DT880s. There's also a faint crackling sound when I move the tubes around.
Anyone got an idea how to fix the low base? Using the Neutralizer android app, it looks like frequencies below 900 Hz are getting steadily quieter. I've attached a pic of the equalisation curve. I also couldn't hear the 32 Hz sound at all, no matter how much I turned up the volume. I really hope that that's not how it's supposed to sound, that would be very disappointing.
Attachments
Tryomg to solder directy to tube pins isn't a great idea. The metal is usually not very solder friendly. Not sure where you are but you should be abe to find sockets nearby.
Connecting the grounds the way you have its is probably OK.
It is hard to guess why the freq response is odd, since you have made so many mods. Do you have a schematic as built?
DT880s come in different impedances. Even if 32 ohms the FR should not look like that. I would question the validity of the app.
Last edited:
The voltage being correct is a good sign. I would suspect that maybe the muting circuit isn't pulling in the relay? You should hear it click a bit after you turn the power on. If not, check to make sure the right diodes are in the right place and in the right orientation (I know, very hard to read).
You're in Tyler - do you know Raymond?
Sorry, very hard to guess what you are hearing. If you can hear the difference between CCS and resistor, and between tubes, then you are hearing relatively small changes. This amp does not have the very low distortion leves that you find in an opamp-base amp - it is somewhat "tubey".
Your headphones are not super efficient so I guess I wouldn't expect earsplitting levels, but it should be OK.
I would try a different source, CD or a good DAC?
I couldn't find any local vendors, but I wouldn't know where to start looking anyway. On ebay, most of them are either from the US (20$ shipping) or from china (takes ages to ship, but cheaper). I thought about tightly wrapping some thin wire around the pins. Would that work?
I attached the schematic I used. The only modifications are the usage of 12SR7 tubes instead of the 12SR7GT, but they have the same pin layout afaik, and adding a 3.5mm input as well as the RCA jacks. The RCA jacks are connected as long as nothing is plugged into the 3.5mm, and both work fine.
The app I only use to make the sound a bit flatter compared to normal. It plays a sound at several frequencies (32, 63, 125, 250, 500, 1k, 2k, 4k, 8k and 16k Hz) and I adjust the volume so that They are all the same volume. It helps with the treble and low bass of the DT880s, which are the 600 Ohm edition.
Attachments
Pete, you are right, I don't hear the "click". I'll look over the diodes this afternoon.
Hey! Thanks so much for the recommendation to go over the solder connections you have made to others in response to problems. Last night I did that with one of your other designs, and it is working GREAT!
NoMethod.
Hey! Thanks so much for the recommendation to go over the solder connections you have made to others in response to problems. Last night I did that with one of your other designs, and it is working GREAT!
NoMethod.
OK. This is based on the orignal starving student, which is a bit different than the SSII offered here.
Anyway... the output caps might want to be larger for such low impedance headphones, 330uF or 470uF would be good. And I really have no idea how well a 12SR7 tube will work here.
There are many vendors for tube stuff in Germany (assuming that is where you are?), like Ask Jan First ® ; electron tubes and more
No component changes needed. But the RK27 is much larger than the on board pot, so you may have some mechanical challenges.
Pete
Thanks Pete. I will be using my own large enclosure so I have lots of room.
What are some mods or upgrades builders have performed?
Thanks!
Help please
Hi,
This is my first real project this size and I have hit a problem. I got everything built and preformed the smoke test. Have almost 19v on both sockets. However, I only have sound in the left channel. I've swapped tubes, tested the headphones and the source. I traced as much of the right channel as I could (what to do at the socket?) and reflowed a few questionable joints. Still no luck. Any help would be much appreciated.
Cheers,
Hi,
This is my first real project this size and I have hit a problem. I got everything built and preformed the smoke test. Have almost 19v on both sockets. However, I only have sound in the left channel. I've swapped tubes, tested the headphones and the source. I traced as much of the right channel as I could (what to do at the socket?) and reflowed a few questionable joints. Still no luck. Any help would be much appreciated.
Cheers,
As much as I hesitate to suggest, I listened when Pete recommended that I re-solder the diodes. And it worked! The only difference was that I had both channels out. But like you, I had proper voltages.
Don’t give up! In a couple of days you’ll be ordering another kit!
Hi Pete, I have been browsing your earlier material on SS HPA's, and bit tempted on the 12AU7 version (normally preamps come loaded with them). Since the initial version used 19J6, the availability of tubes probably made you chose 18FX6(A). the SS II board seems not to be suitable for 12AU7 straightaway since pin outs are different...do we have a work around or Point-Point soldering to the Tube holders is the only way out...thats more of mechanical solution.
Just finished the SSII and it was a really enjoyable project. Thank you Pete. As this is my first experience with tubes, I've been having a great time testing it with various headphones. I've been running it in the resistor plate load, and plan to switch to CSS in a couple weeks and try that out.
I notice a barely audible hum on my sennheiser 558, and a very pronounced background hum with the campfire audio nova (22 Ohms, 114 dB SPL/mW Sensitivity). Whereas the background is dead silent on the LCD-2. I'm wondering if I have a ground issue, or if the IEMs are simply a poor pairing for this amp.
I notice a barely audible hum on my sennheiser 558, and a very pronounced background hum with the campfire audio nova (22 Ohms, 114 dB SPL/mW Sensitivity). Whereas the background is dead silent on the LCD-2. I'm wondering if I have a ground issue, or if the IEMs are simply a poor pairing for this amp.
Quick question - I am not getting the right measurement range when I test voltage between pins 3 and 4 on tube sockets- barely get anything. Does this mean the tube sockets should be extracted and re-soldered first, or should I look back to something earlier in the circuit as possible problem? The tube LEDs do light up. Thanks - determined not to give up!
Oh, man! I was so close!!!! It was playing excellently out of its (factory) enclosure. But then it stopped working when I assembled the box. Took it out and it worked again. I slowly started putting the enclosure back together.
But now it plays only a single channel very well. And it doesn't care which channel!!! Either L or R works fine but when I plug in both RCA plugs, the level and quality drops way down. Especially absent is the low end. Not terrible distortion, just very muffled. Just unplug one of the RCAs and it sounds great, and sound comes out both L and R outputs.
Pins 3 are good, solders look pretty good to me. Any thoughts folks? Thanks!
But now it plays only a single channel very well. And it doesn't care which channel!!! Either L or R works fine but when I plug in both RCA plugs, the level and quality drops way down. Especially absent is the low end. Not terrible distortion, just very muffled. Just unplug one of the RCAs and it sounds great, and sound comes out both L and R outputs.
Pins 3 are good, solders look pretty good to me. Any thoughts folks? Thanks!