NOS Tubes for Sunn Solarus....

[paulcampo]

Hey All, I'm new here and was glad to find such a cool site for old Sunn amps...Well I have a Solarus head I got off ebay coming any day now,and was wondering how you felt about tubes in relation to tone...I play old JCM 800s and have been playing for 27 years.. I know that Tung Sol 6550 (USA made) are the absolute best 6550 made, and I'll likely put in Telefunken smooth plate 12ax7 and 12au7s...but I've never needed to know about a 6an8 tube...what tonal effect does the 6an8 have on the overall sound?...anybody have any thoughts?
Thanks!
Paul

[djc]

other guys will be able to explain this, I don't really understand it, but that 6AN8 is a phase inverter.  I don't think it affects tone.  and I don't think there are other easily available tubes that work in that spot.  at least other tubes like 12ax7's and the like don't.
good luck, sweet amp.  what are you using it for, guitar or bass?
BTW, I like JJ KT-88's in my 200s opposed to 6550's. 

[paulcampo]

Thats what I was thinking about the 6AN8 tube...phase inverter. I was wondering if a better tube would give you quieter operation or it doesnt have an effect at all? I should probably wait until I get the amp as I'm really excited about it but its not here yet. I've heard good things about the JJKT88s....especially with the price of old Tung Sol 6550s these days! I have enough to last me though...haha...my attitude with any tubes/tube amps is just try different ones till you find your tone....I try to put in tubes and try them for a few days as you then hear and feel the difference in tone. Has anyone experimented with the 12AU7? Is this a reverb/tremolo tube, and the 12AX7 is the real tone slot? It also appears to have a visible solid state rectifier 'plug' to the left of the 6550 tubes next to the transformer. Any ideas on the tone of these over the tube rectifier? Are these interchangeable or are they permanently installed in the amp? I know a tube recitifier will give you a tonal 'sag' that is associated with most tube recitifer amps I've played. Anyways, this is a great forum as I've been studying and reading up on all of it....thanks!

[rick.heil]

One of the more senior members can give you specifics, but I've heard a lot thrown around on this forum about changing it to a certain solid-state rectifier.

Disclaimer : I have no idea if said replacement would do what you're looking for, just a suggestion for discussion.

[paulcampo]

Really? So people feel the solid state rectifier is a better tone then? I know you'll get a little more volume as in the case of switching the tube rectifier for the solid state in the Fender 59 Bassman combo reissue....so what I noticed was that one just sold on ebay and had no sign whatsoever of a recitifer solid state or tube...mine is showing what would appear to be a solid state rec. as its not a tube..I should be getting it any day, and I think I'll have a tech give it a checkup to make sure all is well with it....so who are the 'senior members' you are speaking of, and how do you become one? I think at my age, I must be old enough...haha
Thanks
Paul - http://www.myspace.com/paulcampo

[Soundmasterg]

It all depends on what you pan to use the amp for. If it is guitar, then I would say to stick with the tube rectifier as it will give some sag that works well with guitar. If you plan to play bass through it, then a solid state rectifier would be a better choice as it gives the impression of a tighter low end and a more immediate reproduction of the sound. Another choice is to use a Weber Copper Cap, which is a solid state rectifier replacement module that emulates the voltage drop and sag of the tube rectifier. You can see them at www.tedweber.com.

One problem with going with a solid state rectifier is that the voltages go up in the amp as a result, and it may go up high enough to stress the upper voltage ratings of the filter caps in the amp. You won't know for sure until you get the amp and you can experiment with it.

The 6AN8 works as the phase inverter in the amp. The power tubes work as a push/pull pair, and while one is pulling, the other is pushing....kind of like a 2 cylinder engine with one piston going one way while the other goes the other way. The signal gets it's phase reversed at the phase inverter so that it will work for each power tube appropriately. There is no replacement for the 6AN8. There are some tubes that are similar, but I would just stick with the 6AN8. Any of the other similar tubes would require some rewiring of the socket and some voltage adjustments to work, and they would also change the sound. Besides, good NOS 6AN8's are pretty cheap. Get a couple extras and you'll be good for the life of the amp. The 12AX7 is for the gain stages in the preamp and will affect the tone the most.

Personally, I like the JJ KT88 in my Sunns too. I've tried Tung-Sol 6550's and they sound good too, but for the price, I'd go with the JJ's every day.

[rick.heil]

^ senior member

I use that to refer to experience and knowledge about the amps, not a reference to age at all :-p.  Soundmasterg is one, the guys marked with the "moderator" badge are another set, and of course Conrad occasionally pops by (the ultimate in senior member I suppose!).  There are plenty more, just depends on what your question is.

And the CopperCap was the often-discussed thing I was trying to remember.

[paulcampo]

Thanks guys for all the info..it is being shipped with a tube rectifier so I think I'll start a new post on the topic...

[sundhy]

Regarding the 6AN8 phase inverter tube - this is not the best tube to use plus they are leaky.  This may sound strange from the one who manufactured the Solarus, but over time one learns and advances.  There is a modification using 1/2 of a 12AT7 to drive a longtail pair phase inverter.  However, this requires drilling for another 9-pin tube socket.  If you want to maintain the amp in its original condition for collector value, this mod is not recommended.  If you don't care about that and want maximum performance then a modification is in order.

Conrad Sundholm
www.conradamps.com
www.myspace.com/conradamps

[paulcampo]

Hey Conrad, thanks for the reply...I'm obviously very interested in what you have to say on the topic of Sunn amps! haha...its a pleasure to meet you! ...so when you say maximum performance, what does that exactly mean? Depth of tone or possibly more/less headroom? I might be open to it if I could find someone in my area to do it.I'm not a collector, and I'm a working musician. If you say the amp should be modded in this way I'm all ears. Do you do repairs/mods on Sunn equipment if shipped to you? I just moved to Seattle two months ago, so I dont know too many people here as of yet...also, I used to do a lot of tube sales on ebay and some sources say you can sub the 7258 or 8489 tube for the 6an8 in most circuts for better performance...is this true?...or are these numbers just military designations for the same 6an8 tube?
Thanks
Paul

[djc]

wow.  conrad sundholm.  this is one of those uhhh..., ummm..., brain draws a blank type moment.

[Isaac]

Does anyone have a link to the mod?

What about converting to a split-T driver stage like the Model T has?

[paulcampo]

So does anyone out there have or know of the 12AT7 modded Sunn like Conrad was speaking of? I'd like more info if anyone knows...or possibly this is a new revelation he just designed recently? Maybe the begining of something that sounds really good...the excitement of the quest for tone!

[paulcampo]

Heres some great Sunn labeled Genelex KT88s that are on ebay...unfortunately they wont be going in my new Solarus as they are WAY too much... I've never seen any Sunn labeled tubes, and I cant beleive Sunn amps came stock with GEC KT88s! Now thats the quality you want to hear in your amp!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230139162949&fromMakeTrack=true&ssPageName=VIP:watchlink:middle:us