Ampeg SVT 50th Anniversary Edtition

[The_Janitor]

Currently sitting in the Denver airport on the way back from the show. The way my Yamaha reps explained it to me was that Yamaha is honoring Ampeg's 50th year with this SVT, then not adding any new products for the rest of the year.

Next year expect to see new amps.

 

[bobyoung53]

Bob, given the limits of the sound recordings proffered in the clip -- any thoughts on the "dual voicing" strategy they took here? Sounds useful to me. But can we infer that they voiced channel one to break up earlier than it ordinarily would?

I love my V-4B but would love one of these for more clean headroom.

Thanks!

It sounded the best to me with both channels. The first channel seems to be voiced a little dirtier than the second one, I don't know if it's really breaking up or what, not sure how they did that. That head really sounds good though, I wish I had one to compare to my 70's heads, sounds very similar to me, mine may be a little cleaner until it's pushed.
I've run channel one into channel two in an old Fender Bassman though and it gave you a lot more control of the sound, I might try that with my SVT.

"I love my V-4B but would love one of these for more clean headroom." Everyone should own an SVT.

 

[bobyoung53]

Given that it’s the 50th anniversary of this monumental amplifier, it’s nice that they are recognizing it with this special revision. I bet that it does well.

It’s also impressive that 50 years down the road, there are still a lot of original SVT amps out there in service. I have a restored 1971 that’s better than new. My 1963 B15N is 56 years old and it too is in top shape. Both sound fantastic. A tribute to the designers.

Who would ever have thought that these amps would still be desirable, so many years later.

You can't kill an old Ampeg.

 

[bobyoung53]

You might notice that Channel 2 has Volume, Bass, Treble. So what he says and what you get are a bit different. My guess is they voiced Channel 2 to be a bit more like a mid 70s Channel 1, but you still only have the functionality of Bass and Treble controls. Honestly I would rather have the original Channel 2 voicing as it is actually very cool. I believe it's like a B15.

In the original amps Channel 1 had three 12DW7 tubes and channel 2 had a single 12AX7. The SVT VR subs 12AX7 and 12AU7 for the 12DW7s in Channel 1. So you get the same gain structure.

Explanation. 12AX7, 12AU7, and 12DW7 are all dual triode tubes. With 12DW7, one triode is equivalent to 12AX7 and one triode is equivalent to 12AU7.

The vintage amps also used a 6C4 tube to blend Channel 1 and Channel 2. The 6C4 is a single triode tube equivalent to one side of a 12AU7.

I had a skunkworks head years ago and it came with the 12AX7's in the preamp like the modern ones *(it was somewhere in the high 200's, supposedly the first ones had the old 12DW7 circuit) and there was a simple mod that involved just cutting a couple of traces on the circuit board so you could use 12DW7's like the original 70's heads, it sounded exactly the same after, I was disappointed

 

[beans-on-toast]

Currently sitting in the Denver airport on the way back from the show. The way my Yamaha reps explained it to me was that Yamaha is honoring Ampeg's 50th year with this SVT, then not adding any new products for the rest of the year.

Next year expect to see new amps.

Denver airport a large busy place. They could make money selling t-shirts that say “I got lost in the Denver airport”.

 

[bobyoung53]

Thanks. When you say "The original channel 2 voicing" is "like a B15" are you referring the the '69 SVT or the SVT-VR? Or both?

Glad you mentioned the lack of mid control on the re-release relative to "clean" channel 2 as I would use an amp bigger than my V-4B almost exclusively for greater clean headroom. So perhaps the standard VR is a better choice for me personally as it would give me more mid controls for the channel I am going to favor.

Still, exciting to have more new gear to drool over!

I very rarely used channel two for anything except when I used to run Rickenbacker's stereo into the one head, I always felt the second channel was kind of one dimensional without the active mid control. Still nice to have though.

 

[Wasnex]

I very rarely used channel two for anything except when I used to run Rickenbacker's stereo into the one head, I always felt the second channel was kind of one dimensional without the active mid control. Still nice to have though.

I actually prefer the basic voicing of channel 2, but rarely use it because the EQ is not flexible enough without the mid control.

 

[bobyoung53]

I actually prefer the basic voicing of channel 2, but rarely use it because the EQ is not flexible enough without the mid control.

I'm sure I would have used it more if it had a mid control too, it always seemed to middy to me.

 

[Mastermold]

I posted this in the NAMM thread already but since it's Ampeg it belongs here too I suppose--me, JimmyM and Hodgy from Ampeg. It was fun getting to hang with such nice folks!

 

[JimmyM]

I posted this in the NAMM thread already but since it's Ampeg it belongs here too I suppose--me, JimmyM and Hodgy from Ampeg. It was fun getting to hang with such nice folks!

View attachment 3299866

And of course my wife NancyM

Really great to meet you finally, Ron! We ran ourselves ragged there but we had a great time!

 

[cerrem]

From the digging I have done, the preferred tube would be the 6146B and a matched NOS set is almost impossible to find. 6146W are available, but I don't get the idea there is a bunch of NOS supplies left of those either. There are current production Chinese 6146Bs available, but reviews suggest low manufacturing quality and reliability problems.

Here are my notes:

6146B are 35W max plate dissipation. There is confusion on whether 6146W is 35W or 25W. Some claim that W's made after a certain time around 1964-65 were 6146B spec, and earlier tubes are 6146A spec. 6146W Information:. Others claim all varieties except 6146B are 25W; essentially all 6146Ws are just ruggedized 6146As.

The only datasheet I have found is for the RCA 6146W. It appears to be dated 9-65 and indicates 25W max plate dissipation (ICAS). No 6156W datasheets listing 35W have been located.​

The 35W is good to have but not really needed in the SVT.... I have run all the variants of 6146A, 6146B and 6146W .. @ 700V on the plates ...no failures or over-heating of the tubes... These tubes are biased at 15W each in the SVT...
I own three 69' SVT's with 6146 Tubes.....I do not have any failures and play them constantly.... One time I did have a failure but it was mechanical failure of the 6146... The glass cracked on one 6146 from the amp being too loud and having the heads on top of the cabs...LOL
To answer your questions..... The Sylvania 6146W tubes are 6146B tubes... I measured the bulb temperatures with infared camera while operating the tube in increments up the 35 Watts.....

 

[NeonVomit]

Given that it’s the 50th anniversary of this monumental amplifier, it’s nice that they are recognizing it with this special revision. I bet that it does well.

It’s also impressive that 50 years down the road, there are still a lot of original SVT amps out there in service. I have a restored 1971 that’s better than new. My 1963 B15N is 56 years old and it too is in top shape. Both sound fantastic. A tribute to the designers.

Who would ever have thought that these amps would still be desirable, so many years later.

Pretty clear case of 'If it ain't broke, don't fix it'.

Some designs are just timeless and you don't mess with them much. This is one of them.

Speaking as someone who was never really a fan of Ampeg.

 

[greengoblin]

Meh... I was really hoping to see a true reissue of the 69 with 6146's or at least the same pre-amp tube layout with 6550's. Although I understand the 6146s are getting harder to find. Not big on the the 69/70's channels marketing hype.

Would've been nice to see a skunkworks type reissue, handwired, original SVT layout (even with 6550's) without all the modern IC's and other stuff inside. Just a true SVT tone monster.

 

[The_Janitor]

Denver airport a large busy place. They could make money selling t-shirts that say “I got lost in the Denver airport”.

Still better than Dallas, Atlanta or O'Hare.

 

[Jim C]

And of course my wife NancyM

She is very cute, and was interested enough to go to NAMM with you?
Awesome woman!

 

[cerrem]

Meh... I was really hoping to see a true reissue of the 69 with 6146's or at least the same pre-amp tube layout with 6550's. Although I understand the 6146s are getting harder to find. Not big on the the 69/70's channels marketing hype.

Would've been nice to see a skunkworks type reissue, handwired, original SVT layout (even with 6550's) without all the modern IC's and other stuff inside. Just a true SVT tone monster.

If AMPEG wants to hire me.... I can make a bullet-proof version of the 69, true to the original circuit... High quality PCB material not the FR-4 cheap garbage...and 4 oz copper traces with High Voltage clearances and extrusions to prevent arcing... I have wound these early transformers many times and know how to wind them to keep them original sounding... Then they need build a 8x10 cab with real wood not particle board and return to using the ALNICO magnets .....I don't believe Ampeg will pay a descent salary.... I think they like cheap interns with little to no experience...

 

[Wasnex]

The 35W is good to have but not really needed in the SVT.... I have run all the variants of 6146A, 6146B and 6146W .. @ 700V on the plates ...no failures or over-heating of the tubes... These tubes are biased at 15W each in the SVT...
I own three 69' SVT's with 6146 Tubes.....I do not have any failures and play them constantly.... One time I did have a failure but it was mechanical failure of the 6146... The glass cracked on one 6146 from the amp being too loud and having the heads on top of the cabs...LOL
To answer your questions..... The Sylvania 6146W tubes are 6146B tubes... I measured the bulb temperatures with infared camera while operating the tube in increments up the 35 Watts.....

Thanks...I did realize the tubes were biased way below 25W, I was kinda curious how they would behave if run hard, which is not an issue with my basement queen. It was thrashed and obviously had many tube failures before I bought it, possibly because Node H was never built into the power supply. I have rectified that.

It seems GE and Philips ECG are the commonly available 6146Ws. I put a matched sextet of the Philips in mine.

Can you share the actual working voltage at Node E for a properly running 6146 equipped amp? Schematic says 220V, but I believe 230-235V is probably closer to normal.

 

[Wasnex]

Meh... I was really hoping to see a true reissue of the 69 with 6146's or at least the same pre-amp tube layout with 6550's. Although I understand the 6146s are getting harder to find. Not big on the the 69/70's channels marketing hype.

Would've been nice to see a skunkworks type reissue, handwired, original SVT layout (even with 6550's) without all the modern IC's and other stuff inside. Just a true SVT tone monster.

I guess it depends upon how you judge the circuit. I believe most of the Skunks used 12AX7s throughout channel 1 and the PI, so it's not 100% true. You can flip between 12AX7 and 12DW7 which a simple resistor swap. I believe I have already given you the directions...PM me if you want them again. The VR maintained the gain staging of the original amp but did it in sort of a weird way.

As you probably know the 12DW7 is has one 12AX7 triode and one 12AU7 triode....also 6C4 is a single 12AU7 triode. Rather than using relatively uncommon tubes types (12DW7 and 6C4). The VR maintains the proper gain and circuit functionality by going in and out of various 12AX7s and 12AU7s. I posted the signal path here last night if your interested: Ampeg SVT-VR LOUD static noise when turned on Also you can see for yourself by comparing the VRs preamp to the vintage preamp. http://www.bustedgear.com/images/schematics/Ampeg_SVT-VR.pdf

 

[greengoblin]

I guess it depends upon how you judge the circuit. I believe most of the Skunks used 12AX7s throughout channel 1 and the PI, so it's not 100% true. You can flip between 12AX7 and 12DW7 which a simple resistor swap. I believe I have already given you the directions...PM me if you want them again. The VR maintained the gain staging of the original amp but did it in sort of a weird way.

As you probably know the 12DW7 is has one 12AX7 triode and one 12AU7 triode....also 6C4 is a single 12AU7 triode. Rather than using relatively uncommon tubes types (12DW7 and 6C4). The VR maintains the proper gain and circuit functionality by going in and out of various 12AX7s and 12AU7s. I posted the signal path here last night if your interested: Ampeg SVT-VR LOUD static noise when turned on Also you can see for yourself by comparing the VRs preamp to the vintage preamp. http://www.bustedgear.com/images/schematics/Ampeg_SVT-VR.pdf

I guess I never really sat down at thought out the signal path like this and instead concentrated too much on the tube designations rather than the sum of all parts. I was aware of the internals for the 12xx7 series, but not the 6c4. So really then, it would be nice to have a more original layout like the Skunkworks HD or original SVT, basically nothing with newer IC's and such. Go back to the tone roots.

 

[cerrem]

Thanks...I did realize the tubes were biased way below 25W, I was kinda curious how they would behave if run hard, which is not an issue with my basement queen. It was thrashed and obviously had many tube failures before I bought it, possibly because Node H was never built into the power supply. I have rectified that.

It seems GE and Philips ECG are the commonly available 6146Ws. I put a matched sextet of the Philips in mine.

Can you share the actual working voltage at Node E for a properly running 6146 equipped amp? Schematic says 220V, but I believe 230-235V is probably closer to normal.

Yes... You are correct.... With 120V going in.... A well set-up 6146 SVT will have roughly 695-700V on the plates and 230-235 on the screens at idle...
A few problems when the amp is turned up to full power..... The 120V takes a major dip.... First it dips if your using a long power cable....then it dips in the tiny wire it passes through to go through the MOLEX connector up to the ON-OFF switch then back down through the little MOLEX connector and tiny wire back to feed the transformers..... The heaters also take a dip, thus lowering the effective gm of the output tubes... I use an OCTAL socket relay from the ON-OFF switch so the 120V current only travels a few inches and through 14 Gauge wire... I also re-wire the heaters with bigger wire and start the heater feed from the CENTER of the 6 output tubes.... The original heater wiring daisy chains the heaters with 6 power tubes in series with tiny wire....so the last tubes in the heater string takes a major voltage droop...it winds up ending around 5.9V ... So now your pricey matched tubes are no long matched with un-even heater voltages.. Yes..the GE JAN spec 6146W tubes up to the 6146B specs...
WHen your 120V is drooping it will make the High voltages and heaters also droop even more than normal secondary loading... this will kill the power output... When you make some of these fixes you can get 350W output into 4 Ohms...