[Dimu]

Been enjoying vinyl from AT440MLb cartridge directly to TU-8500 preamp. Sounds better than Gungnir Multibit, at least I have this impression. Ordered Nagaoka MP-200 to compare. This is getting unhealthy- rolling tubes and cartridges at the same time

There is some hum in the phono section of my TU-8500, will have to open it up and do some investigating. Could be those Bursons that I inserted in there, but I hope that's not the case.

 

[Dimu]

Crackle all but gone can still hear very very slight. Any ideas?

What are you soldering with? Unleaded crap? I used lead with silver on mine and made sure everything was heated properly. No issues with joints. Unleaded solder is garbage.

 

[Sir Gaben]

Been enjoying vinyl from AT440MLb cartridge directly to TU-8500 preamp. Sounds better than Gungnir Multibit, at least I have this impression. Ordered Nagaoka MP-200 to compare. This is getting unhealthy- rolling tubes and cartridges at the same time

There is some hum in the phono section of my TU-8500, will have to open it up and do some investigating. Could be those Bursons that I inserted in there, but I hope that's not the case.

What turntable do you have?

 

[Dimu]

AT-LP1240, nothing fancy, just a solid turntable

 

[dawktah2]

What are you soldering with? Unleaded crap? I used lead with silver on mine and made sure everything was heated properly. No issues with joints. Unleaded solder is garbage.

I used Kester lead rosin solder.

I switched input cable L <--> R and tubes L <--> R, crackle remained on the right.

 

[Lasollor]

If those are new you are set for life! They are formally rated at 10000 hours. Even if they last half that long you have multiple decades of daily enjoyment ahead of you

caps will have to be replaced many time before you wear out 6 pairs of E80CC. Many caps are rated at 1000 hours only. Even really good ones are 3000 hours. So you will need to replace caps at least 20 times before you have to buy more E80CC

Good to know! Thanks.

About my rattling E80CCs:
I’ve got a good deal on two used pairs of tube dampers in a local store. I hoped it would solve my problem with the driver tubes rattling a little.
It turned out that the tubemonger socket savers made the rattle way worse. After removing the sockets the rattle became almost non existent. And the damper’s mass is just enough to eliminate the remaining rattle. It’s not the best solution and I don’t like the color, but it was almost free and works for now.

Picked up some Toshiba UY-807A tubes recently so did some tube rolling too.
This is an interesting tube.
There is not much about it in english on the internet, but I’ve found some information in japanese: (neither english nor japanese are my native languages so some information might lost in translation):

“Apparently a researcher called Eizaburo Nishibori who later lead the first Japanese Antartic Research Expedition was working in the Vacium tube research center of Toshiba Denpa (They were mainly working on tanks and airplanes) said somewhere, that the Japanese army wanted to equip their tanks with an ultra-short wave (under 10m) telephone so they ordered the research center to quickly develop and manufacture a vacume tube which is capable of very high frequency. The Japanese-Sino war just started so they had to act fast. At the time the frequency limit of the bakelite base vacuum tubes was 20 Mc/s. They developed a new vacuuming method and used a steel base for shielding. This was the birth of the UY807a tube which was capable producing smaller than 10m ultra-short waves (40MC/s) and which was only made in Japan and only for a very short time.”

It is a bright tube, the brightest 807 tube I’ve heard with very upfront vocals. It makes the HD650 sound similar to my Stax L700.

 

[Dimu]

There is some hum in the phono section of my TU-8500, will have to open it up and do some investigating. Could be those Bursons that I inserted in there, but I hope that's not the case.

Yep, Bursons had to go. And put in very short cables. No audible hum unless I turn up volume. Next step is reducing gain in both stages of phono amp and sticking in four LME49990 in there- waiting for adapters.

 

[Dimu]

Dropped gain of both phono amp stages by half and added 10 and 0.1 ceramic caps to op amp bypass electrolytes. No more audible hum even when volume is turned up all the way. Now tubes do more amplification than before this mod. Bursons aren't behaving though- instant hum when I stick them in. So LME49990 project is on. Will have to hack some local bypass for those because there is no ground on the adapter.

 

[Lasollor]

I have a question. What resistor value should I use in R3 and R4 if I want to reduce the gain of the tu-8200?

 

[Dimu]

I have a question. What resistor value should I use in R3 and R4 if I want to reduce the gain of the tu-8200?

why would you want to reduce gain of the whole amp? do you have signal generator and oscilloscope to measure what you are doing? Increasing NFB will bring down gain but it is well balanced as it is.

 

[Lasollor]

why would you want to reduce gain of the whole amp? do you have signal generator and oscilloscope to measure what you are doing? Increasing NFB will bring down gain but it is well balanced as it is.

Actually it would be fine to reduce only the gain of the headphone out. Is there a better way to do that? I have way too much gain.

 

[Dimu]

Actually it would be fine to reduce only the gain of the headphone out. Is there a better way to do that? I have way too much gain.

Just attenuate input signal more, no need to mess with gain.

 

[Lasollor]

Just attenuate input signal more, no need to mess with gain.

Yeah it maybe doesn’t worth the effort. I use about -18db digital attenuation in software and even with that I’ve got about 10-20% usable volume on the pot.
Roon does the DSP in 64bit floating and then converts it back to 24 bit before output. (My Yggdrasil can’t do 32bit)
Most of my music is 16bit 44.1k so I don’t loose any bits, but with 24 bit high res files 18db (3bit) digital attenuation means that I loose some resolution. Of course I’m not going to loose any sleep over it, most likely it’s inaudible. But I don’t want to increase it more than that.
Analogue preamps all had audible effect so I gave up on them. I just wanted a little more range on the volume pot.

 

[ctrlm]

Whilst it is now less audible, I still have a faint consistent hum in my pre-assembled unit that is not affected by volume. I have it in Triode mode and it is slightly louder in Pentode & UL.

That's after the guy I bought it from looked it over and installed Mundorf aluminium oil caps etc. and changed the resistors at the headphone input.

I think I'll take it apart next weekend and give it all the once over to see if there is something obvious such as a bad solder point or something?

 

[Dimu]

I would recommend feeding your files directly into Yggdrasil without any DSP. With each conversion you are distorting sound. If you convert to 64 bit, then attenuate, then convert to 24 you've done three bad things to your signal. And then one more- you aren't using all of the bits in your Yggdrasil when you do that- that's a shame because Yaggdrasil has those expensive chips to have the extra bits. -18dB is insane- you really are chopping dynamic range of your DAC. So throw away all DSP and let Yggdrasil play your source files. And you simply need a different pot in your amp if you want to have different pot volume range.