Onix SP3 information

audiowalker · « **on:** 20 Feb 2010, 07:44 pm »

Hello ~

Does anyone have any experience with using different power tubes with this amp such as using KT66 instead of 5881? And if so, what should be the bias? I emailed Mellody several times but have not heard back from them since they are now selling the Onix line since AV123 has discontinued selling amps, but you probably already know that. Thanks for your assistance.

Cheers ~

bunnyma357 · « **Reply #1 on:** 21 Feb 2010, 03:52 am »

I haven't used KT66's but the I've seen people suggesting running them between 1.40 and 1.65. The preferred brand seemed to be the Gold Lions. A few things to be aware of - a lot of the alternative tubes are large enough that you can't use the tube cage, and some people have had issues with the tube bases not fitting and needing extenders - not sure if it is the amps that vary or the tubes, since for some people they fit fine.

The other thing to be aware of is that the newer SP8/3 has a base bias of .4 rather than the original SP3's 1.15, so depending on which model you have you may have to do a little bit of math to convert a suggested bias.

In general most people feel you get a better bang for the buck starting with the preamp tubes, rather than the power tubes. I ended up swapping out all of mine. For power tubes I've tried New Production Valve Art 350B's, NOS Philips 6BG6GA's with adapters, and NOS Russian Reflektor 6P3S-E's. Originally I was biasing these in my SP8/3 at around .5 or a little higher, but lately I've settled in on .45 with the Reflektor 6P3S-E's.

Also forum member 1BionicEar (Brady) is a great source for both tube info and actual tubes for the SP3. Here is my current configuration, and I'm really happy with it.

http://forums.av123.com/showthread.php?p=745228&highlight=Voskhod#post745228

If you search the AV123 forum there are lots of threads that are hidden since they are no longer current with a ton of SP3 tube info.

Jim C

audiowalker · « **Reply #2 on:** 21 Feb 2010, 04:20 am »

Hi Jim,

Thank you for the helpful information. I have the SP3 and new to biasing tubes. Is there a link to inform me how to calculate bias? I tried to search AV123 for this amp but it seems all of this information has been deleted.

I will contact the other member for additional information. Thanks again ~

Many happy days to you.

Cheer~

bunnyma357 · « **Reply #3 on:** 21 Feb 2010, 04:43 am »

Their search only works for 4 characters or more, so "SP3" won't give you anything, but "KT66" or "bias" will. The old threads are all still there just hidden.

If you've got the SP3, most of the suggestions in the threads are based on the SP3's base bias of 1.15, so you shouldn't have to convert in most cases.

Here are a few of the bigger threads, but there are tons of other ones:

http://forums.av123.com/showthread.php?t=28771&highlight=tube+review

http://forums.av123.com/showthread.php?t=29983&highlight=tube+rolling

http://forums.av123.com/showthread.php?t=10997&highlight=tube+rolling

http://forums.av123.com/showthread.php?t=21475&highlight=tube+rolling

Jim C

audiowalker · « **Reply #4 on:** 21 Feb 2010, 04:50 am »

Hey Jim,

I was just going to reply back to thank you again because I was just reading the thread link you provided to AV123. Very helpful information. Looks like I have lots of reading to do.........

Cheers ~

audiowalker · « **Reply #5 on:** 21 Feb 2010, 05:43 am »

Hey Jim,

After reading several threads, I learned that I have a SP3 version III. Do you know if this amp is by another name like SP8 for version SP3 II?

Thanks again~

bunnyma357 · « **Reply #6 on:** 21 Feb 2010, 05:56 am »

It's not real clear to me the different versions, since I think they made some incremental changes and I was pretty late in getting one, since I have the SP8/3.

The SP8/3 is easy to tell, since the silk screen bias value is listed as .40v rather than 1.15v. The SP8/3 was the last version of the SP3 and was originally supposed to be a totally different EL34 based amp. This thread explains what happened:

http://forums.av123.com/showthread.php?t=31900&highlight=el34+melody

Jim C

audiowalker · « **Reply #7 on:** 21 Feb 2010, 06:10 am »

Okay,

Now I am totally confused so more reading and research. I just checked and mine says 1.15mv but my packing box states it is a SP3 version III. I can not express the gratitude for all your assistance. The person who recommended me to this site said everyone is very helpful. Thanks again~

All my best!