Output transformer for SVT-CL that doesn't limit low frequencies

[Chris 'Wighat' Jordan]

There are all-tube amps out there that reproduce fundamental frequencies down in the 30 hz range. Peavey, Aguilar and Demeter come to mind. If memory serves, these all have a torroidal output transformers. Is that the key? And, if so, I wonder if I could swap O.T.'s in my SVT-CL to get more out of my B string.

 

[beans-on-toast]

This is a complex problem that involves reproduction not only of the fundamental but also the harmonics. Your ears make you think that you are hearing a fundamental when you are mostly listening to harmonics. So how an amp reproduces harmonics is important.

As you said, there are amps out there that reproduce low end fundamental frequencies. The frequency limit is designed into the amp so it isn't as simple as changing one component such as the output transformer. Changing the transformer can improve the tone of your amp so there are ways to tweak the sound. More EI-transformer iron helps reduce low frequency distortion but higher inductance in the windings and make the bass not sound as strong. There are always tradeoffs. It is true that toroidal transformers can have an extended low frequency range. That's one reason why they use them in low frequency amps.

The first thing that I would look at is how well your bass is generating those low frequencies and how effective the pickups are reproducing them. If your bass works well in an amp/speaker cab capable of reproducing true 30Hz, then you know that it is presenting an adequate signal to the amp for reproduction.

 

[CL400Peavey]

There are all-tube amps out there that reproduce fundamental frequencies down in the 30 hz range. Peavey, Aguilar and Demeter come to mind. If memory serves, these all have a torroidal output transformers. Is that the key? And, if so, I wonder if I could swap O.T.'s in my SVT-CL to get more out of my B string.

what cabs are you using?

 

[Coolhandjjl]

The second harmonic of B0 is just under 62Hz. Well within most cabs ranges, even the 'Fridge is rated -3dB@ 57Hz (with -3dB being a common measure of a cabs reasonable low end response.)

No bass cab comes even close to -3dB at the B's fundamental of 30.8 Hz BTW.

Generally speaking, a ss head can hold a woofer steadier with better accuracy in the low frequencies than a tube head however.

 

[ThisBass]

As far as I remember the svt cl response is down -3dB at 40Hz. That's not so bad.
If there is an issue with 2nd Hormonic of B0 I'd suppose the issue at cab response at first.

 

[beans-on-toast]

Here are the specs of the vintage SVT and the 810E. They should come with a grain of salt.

 

[Chris 'Wighat' Jordan]

I use one or two SVT-410-HLF's with my CL. F3 48 hz, F10 28 hz. I love the cab's low end. Even with the CL, I much prefer the bottom to cabs that don't go as low. I have used the cab with a SS head and have noticed how much the CL is obviously limiting fundamentals under 40 HZ. I love my tube amps regardless but just wondering if there was a way to get one cooking under 40 HZ.

 

[seamonkey]

You can add a real powered sub. Send the effects out to the powered sub, send the HP out from the sub back to the effects return.
You'll get closer to the fundamental than most bass cabs could do. Me I like fundamental sometimes, but good harmonics and missing fundamental at other times. It's good to have real options.
Problem with SVT is those line out, line in levels are totally non-standard. A good powered sub should have some level adjust to compensate.

 

[agedhorse]

The output transformer is only one part of the overall amp design. How do you know this is the limiting factor?

 

[nashvillebill]

Toroidal OT's also have some limitations, saturation is a big problem IIRC. (I'm not an OT expert, I'll let others more qualified than me explain). High-performance toroidal OT's are pretty expensive.

 

[ThisBass]

I use one or two SVT-410-HLF's with my CL. F3 48 hz, F10 28 hz. I love the cab's low end. Even with the CL, I much prefer the bottom to cabs that don't go as low. I have used the cab with a SS head and have noticed how much the CL is obviously limiting fundamentals under 40 HZ. I love my tube amps regardless but just wondering if there was a way to get one cooking under 40 HZ.

Do an A/B check of the sound (response) of tube power amp section versus SS power amp section.
That's the best way to eliminate preamp influencies.
It's best to have a bass guitar with active pu or on board EQ to provide low Ra to the power amp input stage.

 

[Chris 'Wighat' Jordan]

The output transformer is only one part of the overall amp design. How do you know this is the limiting factor?

I don't!

 

[Coolhandjjl]

Your cabs are fine. Again, consider a ss or hybrid head. Plenty to choose from.

 

[RoadRanger]

Toroidal OT's also have some limitations, saturation is a big problem IIRC. (I'm not an OT expert, I'll let others more qualified than me explain). High-performance toroidal OT's are pretty expensive.

Actually for a given weight they saturate less than a "traditional" (EI core) transformer. Their main benefits is that they can be lighter for the same performance and often have less loss. Their main disadvantages are that they are harder to wind (you can't just assemble the core around a prewound bobbin like an EI - winding involves going through the middle on every turn <eek!>) and they can be harder to mount (larger in two dimensions, but much smaller in the third).

 

[The_Janitor]

The Peavey VB3 is a 300W head with toroidal tranformer. If you can find one to A/B with your CL you could test your theory to some extent. I tried one out, at gig volumes and found it underwhelming and seemingly quiet. My SVT 2PRO is noticeably louder and produces eyeball-vibrating low end, even down to the low B.

Cabs were different, modern Peavey 810 (VB3) vs SWR 610 (SVT), so YMMV and all that...

 

[Mr. Foxen]

Also might find the the impedance of the cabs down low is high that is making the amp run inefficiently. Ported cabs tend to have an impedance spike down low, and the extra sensitivity from the port doesn't compensate so well as it does with SS amps.

 

[JimmyM]

Ever plug an SVT-CL speaker level DI'd to the board through a really nice PA? I have. It's the cab, not the output transformer.

 

[agedhorse]

Saturation of any transformer is not a problem provided the designer chooses the correct core material and cross-sectional area.

What CAN be an issue is that because the core is constructed typically of a single piece of wound metal tape (rather than stacked laminations), air gaps are minimized and HIGHER flux densities can be maintained before saturation. This means that fewer turns are required compared with an EI laminated transformer and higher inrush currents are possible (for power transformers) and lower resistive portions (compared with reactive) change the audio properties of audio transformers. The core material for audio transformers must be chosen carefully to minimize these effects.

 

[Chris 'Wighat' Jordan]

Ever plug an SVT-CL speaker level DI'd to the board through a really nice PA? I have. It's the cab, not the output transformer.

I guess that could be it...as mentioned, maybe the impedance of the ported cab at lower frequencies is what's limiting the lows. Either way, I definitely have noticed the difference between SS amplification and the CL. This was a largely academic inquiry. It's not like there's actually going to be a drop-in transformer solution anyway.

 

[Slevage]

The output frequency range is not limited by the power supply components.

Core saturation can happen if the suppli is 50hz (Europe) and the design is for 60 he (USA)
But this is often not the case.