SWR Interstellar OD - Retubed

[Low Down Brown]

Hello TB.

It's been almost a month since put fresh tubes in my SWR Interstellar Overdrive pre. I bought it brand new and it has been my primary amp (paired with a Crown XLS 1500) for about 10 years. It's dated 9/2004 and still had the stock Sovteks. I've noticed quite a difference in sound/output over the past year, so I figured it was time for a fresh set. This was the first place I came to get info about manufacturers, tube types, etc. I learned a lot and just wanted to share the results with other Stella owners since there were limited posts about rolling tubes through these amazing preamps.

Based on recommendations found here, I had narrowed it down to the new production Mullards, Tung-Sols and JJ's. I did some shopping around, read some reviews, and decided to just roll them all until I found which ones I liked best. I came across a 24 hour sale and found a decent price on a gold pin 12AX7 Tung-Sol and the Tung-Sol EL84's - right at $35 incl. shipping - so I snatched them up and put them in.

First, I'm no tech or amp expert, so I can only attest to the difference in tone that I was able to notice from listening/playing through the amp before/after. For reference, I'm playing either a US G&L M-2500 or a US LB-100 through Eden D210 XST's. Having said all that, the more those Tung-Sols burn in, the happier I am with the sound. Stella has an even more gorgeous voice than before...across the whole range. The mud-butt is gone and the highs aren't brittle or harsh anymore. The lows are a lot more focused with much sweeter and pleasant sounding mid-highs. I use a Darkglass Vintage Ultra V2 to do some light tone shaping, and I'm finding that the knobs are all getting closer to 12'o clock as each day passes...no need to boost the lows or the cut the mids. Also, it seems as though the tone controls on the IOD itself are a little more responsive. I bypassed all of my FX, did a sweep with the Aural Enhancer, and was pleasantly surprised at how good the amp sounded on its own now. The LB-100 really sounds fantastic this way and I'm pretty excited to see how Stella sounds as a D.I. for recording.

I will say, there is A LOT more crunch on tap now. I've got the drive set about 2 notches below 11 o'clock, and I'm getting the best Jamerson/Motown tone I've ever gotten. Bring it up to about 1 and crank out "One More Red Nightmare" with some serious growl. So, there was definitely a big improvement in the drive/distortion area as far as tone and articulation. Overall, I think I'm pretty happy with the Tung-Sols, so I don't think I will go changing them out any time soon and I would definitely recommend these to anyone in need of fresh tubes for their Interstellar OD.


Oh, and just in case there are any 'tube warmer' folks out there. I run an EHX Black Finger in the first slot of my FX board as a tube warmer (comp. off). It was in need of fresh tubes too, so I replaced the stock EHX 12AX7's with Tung-Sol 12AX7's as well. It transformed into a completely different pedal...much smoother sounding, yet still beefy. The TS's also cleaned up that nasty high-end hiss from the output stage, plus, the comp section is A LOT more usable now as it seems to be more articulate and not as muddy sounding.

One last thing. I just wanted to say thanks to all the folks who ask great questions and/or share their knowledge on TB. This is a great resource and it's awesome to have a place to go where you can find out practically anything you want to know about the ever-expanding bass world.

Keep it up folks.

 

[SC Bassboy]

Very interesting. I'm getting ready to re-tube my beloved IOD for the 3rd time and have been considering the Tung-Sol tubes. Originally I put a set of Electro Harmonix tubes in it then a few years later changed them out for a set of JJ's. After a year or so I put the EH 12AX7 back in there as I found it just sounded angrier. After almost 10 years the pre has started losing bass tightness and developed and nasty scratchy sound. After reading every review at the Tube Store on 12AX7's and EL84's I believe I'm going to put a full set of Tung-Sol's in there and see what happens. Kinda surprised by the reviews as last time I really looked into tubes my perception of the Tung-Sol brand was that they were cheap Chinese stuff but it seems the brand has been bought and production was moved to Russia. Guess they stepped up their game? Anyway, I'll comment back as to my findings.

 

[NKBassman]

Bit of a zombie thread revival here, but I'm game.

I think I have reissue Mullard EL84s in mine, and an unknown 12AU7 in place of the 12AX7. Ironically, I found myself liking my Interstellar Overdrive more for tubey clean tones (or at most a slight crunch), rather than full on overdrive/distortion tones, and swapping the 12AX7 preamp tube for a 12AU7 helped make the gain control a lot less sensitive, and it's got a lot more clean headroom before breakup now. There's still overdrive available, it just starts higher on the dial.

I also had a switch installed to bypass the Aural Enhancer circuit, which turns it into a completely different amp. Both tones are good, but being able to get rid of that mid scoop is a nice feature.

 

[Low Down Brown]

Very interesting. I'm getting ready to re-tube my beloved IOD for the 3rd time and have been considering the Tung-Sol tubes. Originally I put a set of Electro Harmonix tubes in it then a few years later changed them out for a set of JJ's. After a year or so I put the EH 12AX7 back in there as I found it just sounded angrier. After almost 10 years the pre has started losing bass tightness and developed and nasty scratchy sound. After reading every review at the Tube Store on 12AX7's and EL84's I believe I'm going to put a full set of Tung-Sol's in there and see what happens. Kinda surprised by the reviews as last time I really looked into tubes my perception of the Tung-Sol brand was that they were cheap Chinese stuff but it seems the brand has been bought and production was moved to Russia. Guess they stepped up their game? Anyway, I'll comment back as to my findings.

I spent a couple of months looking into tubes and trying to find as much info as I could about tube rolling Stella. I read lots of reviews about tubes on all the different websites and found as much as I could here on TB. I was surprised to find out that there are just a handful of factories putting out tubes for multiple companies based on their specs. I was kinda worried about the quality of the newer tubes myself, but after reading all the reviews and such, I decided to give it a shot since I had to put new tubes in anyhow. I haven't had any issues with the quality of the Tung-Sols, but it's still too early to tell.

I did switch out the gold pin 12AX7 for a Tung-Sol 5751. The gold pin really started to open up as it burned in...it got REALLY crunchy. I was getting some nice breakup at about 10 or 11 o'clock on the gain knob. If you like a good bit of crunch, that might be one to try. I liked it, but it was a bit much for the types of music I'm playing now (jazz, country, R&B/Soul). So, the 5751 was EXACTLY what I was looking for. I run the gain between 11 - 1 o'clock, depending on the bass. It is warm and FAT and is probably the closest I've ever gotten to nailing the Jamerson sound with that amp. I've been running my signal: bass > Union Tube & Transistor LAB Opti-comp > Barber Electronics Linden EQ > IOD. I keep the EQ flat on the IOD and the Aural Enhancer at about 10 o'clock. I haven't been using the IOD as much recently since I've been using a more portable pedalboard rig, but I used the XLR out on Stella about 3 weeks ago with FOH support...it sounded GLORIOUS. The sound guy even came back up and asked about my rig after we did the soundcheck.

Good luck on the 3rd re-tube. I look forward to hearing about it

 

[Low Down Brown]

Bit of a zombie thread revival here, but I'm game.

I think I have reissue Mullard EL84s in mine, and an unknown 12AU7 in place of the 12AX7. Ironically, I found myself liking my Interstellar Overdrive more for tubey clean tones (or at most a slight crunch), rather than full on overdrive/distortion tones, and swapping the 12AX7 preamp tube for a 12AU7 helped make the gain control a lot less sensitive, and it's got a lot more clean headroom before breakup now. There's still overdrive available, it just starts higher on the dial.

I also had a switch installed to bypass the Aural Enhancer circuit, which turns it into a completely different amp. Both tones are good, but being able to get rid of that mid scoop is a nice feature.

I was curious about the Mullard tubes. I almost went with all Mullard, but I got such a good deal online at the time, I couldn't really pass the Tung-Sols up. I'm like you as I use the IOD for more tubey clean tone nowadays than distortion. Have you had any issues running a 12AU7 in place of the 12AX7? I was tempted to do that, but a 'tube expert' that I chatted with said it was not recommended. I'm no whiz with tubes and electronics, so I just went with a 5751 as per other recommendations.

I've been tempted to bypass that Aural Enhancer circuit too. Thanks for the input. I wasn't sure about how big a difference that would make. I guess it's pretty pretty noticeable. Do you prefer the A.E. on or off? Or does it depend on the gig, bass, etc?

 

[NKBassman]

I was curious about the Mullard tubes. I almost went with all Mullard, but I got such a good deal online at the time, I couldn't really pass the Tung-Sols up. I'm like you as I use the IOD for more tubey clean tone nowadays than distortion. Have you had any issues running a 12AU7 in place of the 12AX7? I was tempted to do that, but a 'tube expert' that I chatted with said it was not recommended. I'm no whiz with tubes and electronics, so I just went with a 5751 as per other recommendations.

I've been tempted to bypass that Aural Enhancer circuit too. Thanks for the input. I wasn't sure about how big a difference that would make. I guess it's pretty pretty noticeable. Do you prefer the A.E. on or off? Or does it depend on the gig, bass, etc?

I don't even remember what tubes were in it when I bought it, so I can't say how the Mullards compare to anything else. I haven't noticed any issues with the 12AU7, but I also didn't ask or read into it at all before I did it. I had a 12AU7 laying around so I went with it. I've been using it that way for a few years now in my home studio and haven't noticed any ill effects. 5751 would also be good for reducing the gain. I put a 5751 in the overdrive channel of my Verellen Meatsmoke and it really cleaned things up while still maintaining a decent amount of drive.

The AE Bypass is a huge difference. There's a few old threads on Talkbass somewhere that explain it in far more detail than I ever could. I'm pretty sure I commented in a few of them back in the day, so you can probably find them with a keyword search and using my user name. I tend to prefer it bypassed, but every now and then I'll switch it back in if I find things are sounding too dense or thick or whatever. One thing about it though is that there's a very large increase in overall volume/signal level when bypassed, so I wouldn't say you can really flip the switch back and forth between songs or anything like that. It's also a pretty drastic change between that baked-in mid scoop and a nearly flat response.

 

[Arthur U. Poon]

Bit of a zombie thread revival here, but I'm game......but being able to get rid of that mid scoop is a nice feature.

I wish I knew about tube rolling back when I owned an IOD. I couldn't overcome the mid-scoop you described. Back in those days I was a plug and play guy. Now I know I gave up on that preamp way too early.

I'm glad to hear you've got yours fine tuned. They are a great preamp. Extremely high build quality too.

 

[NKBassman]

I wish I knew about tube rolling back when I owned an IOD. I couldn't overcome the mid-scoop you described. Back in those days I was a plug and play guy. Now I know I gave up on that preamp way too early.

I'm glad to hear you've got yours fine tuned. They are a great preamp. Extremely high build quality too.

The AE Bypass was the best thing I could have done to that preamp. You can roll tubes till the cows come home and not get anywhere near that drastic a change at the flip of a switch. It's like a two channel pre now. I wish the volumes matched up better between in/out on the AE, but that's the way she goes.

 

[Low Down Brown]

The AE Bypass is a huge difference. There's a few old threads on Talkbass somewhere that explain it in far more detail than I ever could. I'm pretty sure I commented in a few of them back in the day, so you can probably find them with a keyword search and using my user name. I tend to prefer it bypassed, but every now and then I'll switch it back in if I find things are sounding too dense or thick or whatever. One thing about it though is that there's a very large increase in overall volume/signal level when bypassed, so I wouldn't say you can really flip the switch back and forth between songs or anything like that. It's also a pretty drastic change between that baked-in mid scoop and a nearly flat response.

The AE Bypass was the best thing I could have done to that preamp. You can roll tubes till the cows come home and not get anywhere near that drastic a change at the flip of a switch.

Thanks for elaborating further on that

Now I'm all worked up and ready to get Stella out of the rack and get to soldering. Time to hit up the TB archives and figure out how to bypass that A.E. Something tells me that I'll end up using it more if I mod it with the bypass.

 

[NKBassman]

Thanks for elaborating further on that

Now I'm all worked up and ready to get Stella out of the rack and get to soldering. Time to hit up the TB archives and figure out how to bypass that A.E. Something tells me that I'll end up using it more if I mod it with the bypass.

IIRC there used to be some good diagrams for the mod floating around. They're not all IOD specific, but the AE circuit should be similar across all SWR amps, I'd imagine.

I had my amp tech do it for me with documentation i printed off talkbass at the time, so I guess it's doable, but I can't personally give you any guidance.

 

[SC Bassboy]

OH DAMN... there's a way to bypass the Aural Enhancer circuit.... excellent. I've had mine in the same position since I bought the IOD, just found the place where it seemed to have the least effect on the sound. Like most of you guys I just use it as a fat tube preamp, never push it into distortion territory. Now if I can just find the schematic....

 

[SC Bassboy]

The AE Bypass was the best thing I could have done to that preamp. You can roll tubes till the cows come home and not get anywhere near that drastic a change at the flip of a switch. It's like a two channel pre now. I wish the volumes matched up better between in/out on the AE, but that's the way she goes.

Would you say the AE bypass kills the high end "sparkle" that everyone attributes to the SWR sound? I had my IOD completely apart yesterday and then backed out because I kept reading that the modification took away some of that shimmer, so to speak. If so I'm going to take it to my amp tech and have him install a switch like you have so it's not permanent.

On a side note, I dug up the thread about bypassing the AE and it directs you to locate the two caps in the circuit, one of which is blue. There's not a SINGLE blue cap in my IOD. It occurred to me that since my unit is after the Fender buy-out that something may have changed and I looked around until I found a picture of the inside of an older SWR produced IOD. Yup... there's a blue cap in those.

 

[NKBassman]

Would you say the AE bypass kills the high end "sparkle" that everyone attributes to the SWR sound? I had my IOD completely apart yesterday and then backed out because I kept reading that the modification took away some of that shimmer, so to speak. If so I'm going to take it to my amp tech and have him install a switch like you have so it's not permanent.

From my understanding (and just a reminder that it's been YEARS since I read anything on the topic), all it does is remove the mid-scoop and boost the overall level. The resulting frequency response is remarkably flat (for better or worse). I don't think it kills any high end, but the additional mid frequencies may swamp that sparkle and make it harder to hear.

I don't use my IOD live, and even if I did I don't use cabs with tweeters. I tend not to focus much on sparkle/shimmer/presence. That being said, my IOD does have a nice presence to it in the studio, especially for a tube preamp designed primarily for overdrive tones.

Install the bypass on a switch and you'll be happy.

 

[ihixulu]

I did the AE mod on my SM400 and it totally changed the amp, and not in a good way to my ears. It does take the sparkle away but it also changes the gain staging of the preamp so that you redline it much more quickly. Basically, it seemed to take away the dynamic range of the pre. Great rock sound but it's not an SWR as you know it. I restored it to stock. Of course, YMMV, and many people are happy with the mod.

On the topic of the IOD, and not meant to hijack, do you/does anyone happen to have the biasing instructions that were floating around a few years ago? I retubed my recently acquired IOD and am curious about the factory bias settings. Cheers

 

[Arthur U. Poon]

The AE Bypass was the best thing I could have done to that preamp. You can roll tubes till the cows come home and not get anywhere near that drastic a change at the flip of a switch. It's like a two channel pre now. I wish the volumes matched up better between in/out on the AE, but that's the way she goes.

That modification sounds awesome. There's one more reason for me to kick myself for selling it.

I also really liked that I could plug it directly into a speaker cabinet and use it as a practice amp. It's definitely a very cool preamp!

 

[Arthur U. Poon]

I did the AE mod on my SM400 and it totally changed the amp, and not in a good way to my ears. It does take the sparkle away but it also changes the gain staging of the preamp so that you redline it much more quickly. Basically, it seemed to take away the dynamic range of the pre. Great rock sound but it's not an SWR as you know it. I restored it to stock. Of course, YMMV, and many people are happy with the mod.

On the topic of the IOD, and not meant to hijack, do you/does anyone happen to have the biasing instructions that were floating around a few years ago? I retubed my recently acquired IOD and am curious about the factory bias settings. Cheers

Would those instructions be in the IOD Owner's Manual? I'm pretty sure I still have mine. It will take some digging through boxes in my basement, but I know I have it somewhere.

 

[NKBassman]

I've had these saved on my computer for a long time.

Disclaimer: I do not know the source or reliability of these documents, and I take no responsibility for anyone who chooses to use them to perform any work on their own equipment.

 

[ihixulu]

I've had these saved on my computer for a long time.

Disclaimer: I do not know the source or reliability of these documents, and I take no responsibility for anyone who chooses to use them to perform any work on their own equipment.

Thank you for this! Will definitely study before attempting.

 

[Wasnex]

Thank you for this! Will definitely study before attempting.

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[NKBassman]

@Wasnex doing the good work I was too lazy/busy to do.