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Hi!

Ive read a few threads about changing the tubes on the ART Tubeopto 8. I got my hands on some vintage telefunken ecc83 smooth plates and I can’t wait to hear how these sound! Several of the threads I’ve found note that you need to remove the tube snubbers before you pull out the tubes and replace them after.

I’ve only ever changed tubes on amps where there are no snubbers involved. They seem pretty glued in. I was wondering if any of you have experience with this, and if so how you got the things out?

Comments

Link555 Wed, 05/27/2020 - 05:24

Usually tubes are mounted in sockets and are very easy to replace. I am not sure about your unit, but this photo shows the sockets. I have never worked on this unit, but it looks like the socketed tubes are retained via the tip....

The 12AX7 is a pre amp valve which is identical to the ECC83 – same valve, just a different name. What's mounted inside now?

What are your goals with this mod?

pcrecord Wed, 05/27/2020 - 06:00

There is a part you need to remove at the top of the tubes. It holds them there. Once removed they should get out easy.
I'm just wondering how much of a diffence the tube makes in this unit.
I remember changing tubes in a DBX Silver 586 and it didn't made any differences. It depends where they sit in the design..
Make sure to make before and after recordings.. I'm curious about this one ;)

doonunit Thu, 12/24/2020 - 02:37

Alexthebore, post: 464418, member: 51927 wrote: Hi!

Ive read a few threads about changing the tubes on the Art Tubeopto 8. I got my hands on some vintage telefunken ecc83 smooth plates and I can’t wait to hear how these sound! Several of the threads I’ve found note that you need to remove the tube snubbers before you pull out the tubes and replace them after.

I’ve only ever changed tubes on amps where there are no snubbers involved. They seem pretty glued in. I was wondering if any of you have experience with this, and if so how you got the things out?

Hi Alex, did you end up replacing the tubes?
I've just gotten a tubeopto and some better quality tubes to go with it. I opened it up and the snubber thingy's look like a real pain to take off.
Looks as though you've got to take the whole circuit board out to un-do the screws..... I honestly feel like it would be easier to de-solder the tube plug to get them out.
What did you end up doing?

Alexthebore Thu, 12/24/2020 - 05:21

doonunit, post: 466400, member: 52154 wrote: Hi Alex, did you end up replacing the tubes?
I've just gotten a tubeopto and some better quality tubes to go with it. I opened it up and the snubber thingy's look like a real pain to take off.
Looks as though you've got to take the whole circuit board out to un-do the screws..... I honestly feel like it would be easier to de-solder the tube plug to get them out.
What did you end up doing?

I did!

honestly, I approached a guitar amp tech friend of mine about this and he said it would be way too much trouble to do any of that. I ended up just using some pliers to bend the snubbers back until I had enough space to plug in the tubes, then I bent them back into place.

I’m sure if I did this a lot, the metal part of the snubber would weaken, but since I planned to just leave these tubes in it worked just fine.

hope this helps!

doonunit Thu, 01/07/2021 - 13:20

The snubbers are the metal plates with a grommet in them supporting the top part of the tube.
They're screwed in from the bottom of the PCB so it would be a mission to remove them.

I didn't even try it with the original tubes so I can't comment.
Just read a few threads where people were saying their units sounded horrible until they swapped the tubes out.
The stock tubes are manufactured in China, I honestly don't know if Russian tubes sound 'better' than Chinese ones but I imagine cheaper, less ideal, materials would be used in the manufacture of Chinese tubes which could well make a difference to the tone.

I just didn't want to set it up in my rack and be left wondering what it would sound like with good tubes in it, so I ordered some reputable tubes at the same time that I ordered the pre amp.

Link555 Fri, 01/08/2021 - 07:05

Thanks for clarifying, I might be wrong but I would have called those things tube Retainers. I know its a convertisal topic but I have not experienced much sonic difference in 12AX7 tubes. Certainly the design and grid current can alter the sound, but once the grid current is set up in a design all the 12AX7s I have messed have sounded virtually identical. The high gain of 12AX7 causes it to have a small window of amplification between the grid current and grid cutoff. Some designs use a small anode voltage, which makes this window of operation even tighter. Do you know what the Anode voltage is in this design?

doonunit Fri, 01/08/2021 - 15:37

Sweet thanks, I was just following what Alex said, I would have had no idea what the official name would have been.
Ok thats good to know, old mate in the thread I read originally changed them out to ECC83s. Do you reckon that would make a difference? I’m not overly happy with it since testing it out. The 12AX7s I put in it are breaking up quite easily, there’s very little gain needed to get a lot of tube distortion. It’s much too heavy of a distortion for my taste. No I didn’t test it when I had it apart unfortunately.

Link555 Fri, 01/08/2021 - 16:14

I Dont think changing them from 12AX7 to another 12AX7 (ECC83) will make much difference. unless your tubes are damaged....How hot is your input signal? do you how much gain your applying....? 12AU7 has the same pin out but a lower gain...but from your description I am not sure too much gain is your issue.

doonunit Sat, 01/09/2021 - 21:05

Yes it’s definitely set to the right voltage.
Ok thanks for the tip, I think that sounds like a good direction to go down. Yeah it’s not necessarily too much gain just lack of headroom until the distortion gets really thick and ugly. I might test out a 12AT7 and a 5751 and see how they go, apparently they’re both somewhere in between a 12AU7 and a 12AX7 gain-wise.

paulears Sun, 01/10/2021 - 00:18

I did smile. In the seventies I was learning electronics from scratch at college. I know little, my friend a lot and much I learned then I can still remember, including, for some reason resonance formulii! With many valve/tube designs we used snubbers - well established designs to remove (usually) voltage spikes. Snubber circuits were part of loads of better designs back then. Vibration mountings, with rubber rings and brackets were never anything remotely to do with snubbers, which were, and still are transient protection, and tended to be small or large depending on the voltages they were trying to moderate. Tubes/valves always had to be matched for critical uses, especially when working in pairs, and quality control was and still is, the critical, not so much the country of origin. Quality control when they produced real quantities alway meant X brand was better than Y, because X removed less good products off the line. Many would be sold through different pathways for non-critical use. Audio, especially radios and TVs were non-critical. Broadcast and hifi, in the audio world were the critical areas, with price to match. Now, it’s more likely to be good and bad batches, not so much brand or country because the scale of production is so small. Apprentices were often given the job of valve testing. Plug them in, let them warm up, decide which bin to put them in in the workshop. When I first started the valve bins were tv, radio, and premium. Any would do in TVs. Nothing has changed really, but I suspect there are more in the system now than before because the fourth bin we had was the scrap bin,

aslem Fri, 06/07/2024 - 21:23

Hello, sorry for my bad English, but I need your help.

A customer sent me an Art Tube opto 8, the optical output was not working, it has been resolved, but the resistor R27 is toast. I would appreciate it if someone could tell me what its value is.

Boswell Mon, 06/10/2024 - 04:17

I don't own a Tube Opto8, but I have used one and been impressed by its versatility and performance.

I don't see any schematics online for the Opto8, so it's not easy to know what the function of R27 is. Unless another member has one of these units and is prepared to open it up to photograph, we are never going to know with certainty.

In the absence of any response from actual Opto8 owners, I suggest that you post a few photographs of the inside of your Opto8 showing the burnt resistor, and, importantly, the printed circuit board tracks in the area of the resistor. It may mean taking the circuit board out of the case, since views of the tracks on the underside would be needed as well.

There is little point in replacing R27 with a new part until you have a reason for it failing in the first place. The mains power supply in the Opto8 provides the anode voltage (HT+) for the valves/tubes, and a likely position for R27 is in the smoothing section of the HT+ line. I would start by looking to see whether R27 connects to high-voltage electrolytic capacitors, and, if so, you should test the capacitors for leakage. To do this check, you would need to unsolder the +ve lead connections to the capacitor if it is separately wired, or else remove it from the circuit board if it's board-mounted. Be certain to disconnect the mains supply to the Opto8 before doing any work of this nature, and to discharge the HT+ capacitors by using a screwdriver shaft to short the +ve capacitor terminals to the -ve while you hold the insulated screwdriver handle.