Swap Out My SVT-VR's Preamp Tubes With Tubes From My Hammond Organ?

[PolkaHero]

Title of thread says it all. I replaced the tubes from my 1961 Hammond A100 organ last year with brand new ones. Of all the tubes I took out, there are three 12AX7s and one 12AU7 that I could put into my SVT-VR (USA version). Do you guys think this would improve the tone of my SVT any? The tubes are all marked "Hammond" but they were made for Hammond by GE among other companies back in the day. I know that Hammond tubes are not stressed in their preamps, so I would think these are still in pretty good shape (plus the organ sat unused for about 25 years).

Would do you tube purists think, experiment-worthy?

[BassmanPaul]

Try it if you like but get the tubes tested before you do.

Paul

[PolkaHero]

Wow, no other comments from all of the Ampeg guys on here?!

[Rick Auricchio]

Tubes are tubes. There are subtle sonic differences among brands and subtypes (e.g. 12AX7WXA vs 12AX7A), and you have to listen to see if you like what you here.

That said, when you're at a gig, you're lucky if the audience knows there's a bass player, let alone hearing subtle tonal differences.

I can categorically state that the Hammond tubes won't make your amp sound like an organ!

EDIT: I can't believe I mistyped "hear" in the second sentence and didn't see it. Yikes.

[Jim C]

I'm guessing that you probably don't have access to a tube tester
Didn't think a bad preamp tube could hurt an amp but defer to the experts
I would try them although I personaly have only heard significant improvements with Mullard or Telefunken tubes assuming the existing are decent

[Groover]

All comments above are valid, including the audience one

I'd say, you probably have a nice batch of tubes, and being a tube junkie, I'd say you scored!

The HAMMOND tubes from what I understand could be made by a variety of good manufactures, such as RCA, GE, RAYTHEON, etc. If those are originals tubes, then those would be tubes made from what old radio guys call tubes made in the golden era.

Also, from what I understand, tubes used in organs were select tubes with low noise, so hypothetically speaking, they would pick the best out of the batch. Being that your organ is a high-end Hammond, I'd say that is likely the case.

Most of those tubes are probably long black plates, which are considered to be nice to use in music amplifiers, such as CD players, etc.

Again, I just like old tubes, and after reading this-and-that about their sound properties and having experimented myself with old vintage tubes, I think you should knock yourself out and try various tubes in various spots until your heart is content. Anything in the Preamp is self-biasing, so any tube weak or strong, balanced or unbalanced should not hurt anything. Once you get into the Phase Inverter and Driver tubes, then you would possible need to BIAS the amp to "really" get the best results from the tube change to see if it's worth the swap or not, but again, I don't think even a weak or unbalanced tube will hurt anything... actually, you may end up liking unbalanced triodes as they will give a certain character to your amp.

Then again, I'd say they are junk. Just send them to me for proper disposal.

[MAMMOTHvolume]

i'd give them a blast! i've tried GE's in the past, they'll probably be nicer than what you have in at the moment.

[PolkaHero]

Originally Posted by Groover

All comments above are valid, including the audience one

I'd say, you probably have a nice batch of tubes, and being a tube junkie, I'd say you scored!

The HAMMOND tubes from what I understand could be made by a variety of good manufactures, such as RCA, GE, RAYTHEON, etc. If those are originals tubes, then those would be tubes made from what old radio guys call tubes made in the golden era.

Also, from what I understand, tubes used in organs were select tubes with low noise, so hypothetically speaking, they would pick the best out of the batch. Being that your organ is a high-end Hammond, I'd say that is likely the case.

Most of those tubes are probably long black plates, which are considered to be nice to use in music amplifiers, such as CD players, etc.

Again, I just like old tubes, and after reading this-and-that about their sound properties and having experimented myself with old vintage tubes, I think you should knock yourself out and try various tubes in various spots until your heart is content. Anything in the Preamp is self-biasing, so any tube weak or strong, balanced or unbalanced should not hurt anything. Once you get into the Phase Inverter and Driver tubes, then you would possible need to BIAS the amp to "really" get the best results from the tube change to see if it's worth the swap or not, but again, I don't think even a weak or unbalanced tube will hurt anything... actually, you may end up liking unbalanced triodes as they will give a certain character to your amp.

Then again, I'd say they are junk. Just send them to me for proper disposal.

Thank you for this insightful information! I might take these into my local Hammond tech to get tested before I start swapping.

What's interesting is that you can find Hammond spinet organs for next to nothing nowadays. Seems like it would be worth picking one up just for the tubes alone!

[PolkaHero]

Just experimented swapping out the tubes. I initially replaced 4 out of the 5 preamp tubes but got a lot of static and noise. Tried putting a couple of the original tubes back in and still got the noise so I ended up only replacing V1 with a Hammond (Made In USA) tube. No static or noise and to my ears the sound is a little warmer but it's a subtle difference at best. I think I'll leave it in and see if it makes any difference at our next gig. BTW, four of the five preamp tubes in my SVT are Groove Tubes, and one of the 12AU7s is a Sovtek.

[christw]

To be honest, I've never noticed differences in preamp tubes besides obvious gain differences. (12AX7 to 12AT7 to 12AU7, etc.) Even among different 12AX7's I've seen very little difference in make, type, or tone besides general categories of new tubes versus select NOS tubes. Even that is primarily just a gain difference. Tone doesn't really change. This is my own testing among 10+ different tube amps with a variety of tubes and makes. (Trust me, I am picky and can tell if there really are subtle tone differences besides expectancies.)

In the end, buying a ton of NOS tubes seems a waste to me. I've got a mix of Sovtek, EHX, JJ, Groove, and NOS GE/RCA/Hammond and Lowrey branded USA tubes in my amps. Those NOS ones I just plucked for great prices or from old amps/organs of mine to test with.

[Groover]

Takes a little while to find the right combination. Not sure how many you have on hand to "roll", but could have been just one out of the four that was a bad tube. You can narrow it down by using your V1 as your "noise" test slot, as any noise from that first spot will build by sequential tubes and just get worst as it works its way to the power section.

Also, it's easy to check for microphonic tubes as well. When the amp is on, just tap the tube slightly with something, like the eraser side of a pencil. It should NOT sound like when you tap your hand on a microphone, instead it should be quite of a very quite thump. You can easily weed through them at least for microphonic tubes that way.

Some of the Grove Tubes that Ampeg uses are just relabeled Electro Harmonix. Those and the Sovtek they use (that I've seen in Ampegs) are typically short gray plates which tend to be a little more sterile sounding, but possibly more punchy, and due to the short plate, they are also more quite and less prone to microphonics - all in all, yes they are good tubes too.
A lot of the differences are suble. If you search the web, some audiophile fanatics have made comparisons of tubes by swapping tubes in broadcast type mics – those are fun to find, and really highlight the difference when listening. A little harder with bass amps because of the low frequencies, but also because you have to basically blow up your ear drums to turn the amp up to really feel the changes. Some changes are easy to spot, others not so much.

[Seans]

12AX7's are really strong tubes and the older the better, so I wouldn't worry about swapping them.
You describe a warmer sound with the Hammonds, this shows you have some nice tubes and the more you play through them the more smooth sounding they will appear, until you put the chinese valves back in and notice how hard and unsubtle they are, you'll soon have the Hammonds back in. Welcome to preamp heaven, try some Brimar, Mullard, telefunkens too, you won't look back.

[PolkaHero]

Originally Posted by Groover

Takes a little while to find the right combination. Not sure how many you have on hand to "roll", but could have been just one out of the four that was a bad tube. You can narrow it down by using your V1 as your "noise" test slot, as any noise from that first spot will build by sequential tubes and just get worst as it works its way to the power section.

Also, it's easy to check for microphonic tubes as well. When the amp is on, just tap the tube slightly with something, like the eraser side of a pencil. It should NOT sound like when you tap your hand on a microphone, instead it should be quite of a very quite thump. You can easily weed through them at least for microphonic tubes that way.

Some of the Grove Tubes that Ampeg uses are just relabeled Electro Harmonix. Those and the Sovtek they use (that I've seen in Ampegs) are typically short gray plates which tend to be a little more sterile sounding, but possibly more punchy, and due to the short plate, they are also more quite and less prone to microphonics - all in all, yes they are good tubes too.
A lot of the differences are suble. If you search the web, some audiophile fanatics have made comparisons of tubes by swapping tubes in broadcast type mics – those are fun to find, and really highlight the difference when listening. A little harder with bass amps because of the low frequencies, but also because you have to basically blow up your ear drums to turn the amp up to really feel the changes. Some changes are easy to spot, others not so much.

I think I'll use some DeOxit and an old toothbrush to clean the tube pins again. I did the pencil test when all four tubes were installed and didn't notice any microphonics. Do any of the tube sockets (V1-V5) make more of a difference tone-wise? Also, I run a DI to our PA system post-EQ; if I ran it pre-EQ, how many of the tubes in the preamp are affecting the DI sound?

[PolkaHero]

Oh yeah, one of my Hammond tubes is an ECC83. Isn't this a European equivalent of a 12AX7? If so, could I replace one of the 12AU7s with this?

[Rick Auricchio]

Correct on the ECC83. As for replacing a 12AU7 with an AX7, it depends on the circuit design. Don't try it without knowing for sure.

As for pre-EQ DI output, that again depends on the circuit design.

[Seans]

Originally Posted by PolkaHero

Oh yeah, one of my Hammond tubes is an ECC83. Isn't this a European equivalent of a 12AX7? If so, could I replace one of the 12AU7s with this?

I wouldn't, stick to the correct types they were designed for. But a NOS vintage 12AU7 ECC82 is not as expensive as an ECC83 12AX7, so ebay would be a good place to find a nice Mullard, GE or T'funk.

[Groover]

There is some information in this thread here in regards to the Tube functions of the SVT-VR.

I wouldn't swap the 12AU7 for the 12AX7, as mentioned above there are tons out there NOS to experiment with, and as Seans said, the 12AU7 seem to be cheaper than 12AX7 when really start comparing.

ECC82 = 12AU7, can also use military 5814 - tons of those out there.

ECC83 = 12AX7 (as well as 7025), can also use military 5751 - these last have less plate current, but work in the SVTs well in place of 12AX7. People claim less noise with them, different distortion break points depending on slots. I personally found the 5751 GE 5 Star 3 Mica in V1 to really add some ba11s to my SVT-HD.

Have fun.

[Seans]

Originally Posted by Groover

There is some information in this thread here in regards to the Tube functions of the SVT-VR.

I wouldn't swap the 12AU7 for the 12AX7, as mentioned above there are tons out there NOS to experiment with, and as Seans said, the 12AU7 seem to be cheaper than 12AX7 when really start comparing.

ECC82 = 12AU7, can also use military 5814 - tons of those out there.

ECC83 = 12AX7 (as well as 7025), can also use military 5751 - these last have less plate current, but work in the SVTs well in place of 12AX7. People claim less noise with them, different distortion break points depending on slots. I personally found the 5751 GE 5 Star 3 Mica in V1 to really add some ba11s to my SVT-HD.

Have fun.

+1, have fun.

You could also look for CV4004 its a specifically designed ECC83 12AX7 for audio applications, not cheap though. CV4003, ECC82 12AU7 also.

Now to really confuse the situation the Early SVT's had 12DW7 which is one 12ax7 and one 12au7 in the same bottle.

Groover how's your early SVT going?, I've just found a pair of military grade 12BH7 for mine, Brimar CV5042 haven't tried in anger yet though.

[Groover]

Originally Posted by Seans

Groover how's your early SVT going?, I've just found a pair of military grade 12BH7 for mine, Brimar CV5042 haven't tried in anger yet though.

All going well with it. I'm pretty happy with the final configuration, but I may still try an RFT ECC83 in there somewhere, either V2 to try and make channel two somewhat "dirty" or in the phase inverter, but I really like the NOS RCA short gray plate in that spot (PI). As far as the driver tubes go, I have some late 60's NOS 12BH7A RCA long grey plates that seem to be pretty good solid workhorses in there.

[Bongolation]

If you know how to read the manufacturer's codes, you can tell exactly what these tubes really are.

There are a lot of really great Mullard and Amperex tubes with various sound gear manufacturer's names on them, and they are the identical stock from the exact lines as the ones marked with the real manufacturer's name.

Some of these are great tubes, and I always have one in V1 in a guitar amp, but I wouldn't waste one in a bass preamp because the differences aren't usefully audible with bass, at least in the way that I play it -- traditional sound with flats.

Some old American 12AX7s really aren't that great, though.