25L15 Contour control

[Brian Ingram]

I'm building a 25L15-style amp, and wanted to here from folks here who might have played one of the newer Standel amps.

I wanted to know if anyone had tried one of the 5-knob versions (with Contour and Top-Cut controls). If so, what was your impression of the utility of those? Did the Contour provide a useful change in the midrange of the amp?

I'm finalizing my plans for the preamp circuit of my build, and felt these might be useful additions. I'm considering an effects loop as well, but there are some technical challenges to adding that, and the effects I'd likely use (outboard reverb, tremolo, a little electronic vibrato, delay) could just as easily be applied before the input jack.

Thanks for your input!

Brian

[alexjones]

Hi Brian,
The Standel I have is an older reissue with 6550's.It does not have the Top-Cut but it does have the Contour option. I have to say that I do find the contour knob very useful. With the knob set from 0-4 gives a nice full, more in your face tone with the Gretsch. When you turn the knob to 8-10 it give a nice more scooped sound with a tele which gets it really twangy - also sounds cool with the out of phase switch on my T60. It's kind of hard to describe and I probably am not using the right terms. But there really is a difference in tone when you adjust that knob. So I do have to recommend incorporating it into your design. I think it would be worth it. I would be interested to hear what people say about the top-cut knob. Haven't been exposed to another Standel - but boy - this is one amp I will NEVER let go. I love it... Hope this helps.
Alex

[Brian Ingram]

Thanks for the description Alex!

So if I read you right, the effect is a widening/deeping of the midrange scoop as you turn the Contour up. Or said a different way, scooping out the mids when turned up, and adding midrange (or having a smaller scoop) as you turn down to zero.

The Top-Cut is something I'm already familiar with from Vox and Matchless amps. Essentially, it allows the very highest highs to be rolled off right before the output tubes. So you can run a fairly bright sound from the guitar and through the preamp, but roll off the highest/harshest stuff just before pushing the speaker.

Since I'm using a D130 with an aluminum dust cover, I'm thinking having good control over the very top end will be a handy addition.

Thanks for the reply and your impressions!

[alexjones]

Brian,
I think you described it very well. If your using a D130 with the original cone the top-cut would be nice to roll just a bit of the trebles off. It's kind of strange but the reconed D130's or the Standel reproduction D130 (I have both) just don't sound identical. The original ones are brighter and more in your face sound while the reconed ones are darker and bassier and warmer. They both sound very good - but there's a big difference. I guess just different situations may benefit the use of one speaker over the other. Anyways - I have tried to learn exactly how tube amps work so as I could design and create my own. But as a civil engineer, electrical engineering just doesn't come very easy. One of these days I want to learn and dive into it. I would love to create a super clean standelish amp that is more lightweight and portable. Some day... I wish you the best of luck on your project and post some pics and audio when your finished!
Alex

[Brian Ingram]

Brian,
One of these days I want to learn and dive into it. I would love to create a super clean standelish amp that is more lightweight and portable.

Well, since the speaker seems to be a very big part of the sound, you just can't get around a somewhat heavy rig. That said, there's no reason you couldn't have a D130 (or two) in a separate cabinet, with just the electronics in a head. It won't have the "clone look" but if you're just interested in the sound and low weight, that's an easy way to do it.

I've been repairing and designing/building tube guitar amps for about 16 years as a hobby. And while I know what to expect with most circuits, I've only heard the 25L15 on recordings. Your descriptions helped confirm what I expected based on looking over a circuit schematic.

I'm eager to post the pics when the amp's done, as I have a friend who's an excellent woodworker doing the cabinet build. Since the sound is all I care about for this build, we've decided to use the same overall shape and form-factor of the original amp, but build it with some pretty hardwood for an eye-catching appearance.

See below for some samples of my friend's amps. These are just samples; I plan on having the same combo cabinet shape as the original 25L15. However, we will be using ribbon mahogany for the overall cabinet, the flashy crotch mahogany (as in the face of the second pictured amp) for the lower front trim panel, and flame maple accents.

[alexjones]

Hey Brian,
Great looking amps! This should be an interesting build. I like your idea of using hardwoods. It sure does add to the weight of the amp - but man it looks beautiful. This is the amp that I have. It's so beautiful. Just thought you would like to see it. If you would like any measurements - let me know. Thanks!
Alex

[Brian Ingram]

Now that's gorgeous! I love the color.

I've already got the version we're doing blueprinted, and the will be slightly larger overall than the original amp. I have an irrational hangup about the horizontal strip at the bottom of the speaker cutout, so we're making it slightly bigger in every direction to allow a complete circle for the D130.

I actually think it might come in a little lighter than the original, since the upholstered amps have some fairly thick cabinet-grade plywood. All-in-all, the wight should be about even.

The only serious internal debate I've had is whether to add an extra tube to allow for an effects loop. However, I'm thinking I can do fine without one. Either way, I'm planning on building an outboard spring reverb (as in a Fender 6G15 Reverb), and I've got a vibrato unit from a Hammond organ to modify slightly into a guitar-friendly unit. I already have a good-quality tremolo pedal, as I usually like old amps with trem, but I may add that feature to the vibrato unit.

So now it's just a wait as my friend builds the cab, then on to the electronic assembly for me.

[George Beasley]

Here is the one I have...it is also an early reissue, with the contour control.

If I am playing Chet stuff, I usually have the midrange rolled off...which is supposedly the same circuit as the old ones. It does come in handy on other things, though.

[PhilHunt]

Great Scott...How do you guys afford those suckers!!

[Brian Ingram]

Well, I'm building mine... that's how I afford it!

Fortunately, I nabbed a D130 for less than half the going price, and a buddy is making the pretty cabinet for the cost of the lumber. I have most of the other parts on hand from many years of amp building, so I pretty much just have to buy the transformers.

But I guess the initial cost to get the hobby started was steep for my first amp builds.

It's also a general policy to me to build it if it is more expensive to buy than build. That's generally been the case with the amps I have which are copies of vintage models I used to collect.