Space Heater - simple tube preamp

[vigilante398]

Well I have good news and bad news about this one. The good news is I finally got a design that works perfectly. It sounds exactly the way it's supposed to, the voltage is holding right where it's supposed to be, and it looks great. The bad news is apparently it doesn't fit in all 125B enclosures. When I designed the board I used the Hammond measurements as a size reference, and I should have 2.44" between the ridge on the bottom plate. The board was designed to be 2.36" wide, which I figured would be enough. But I put it in a Tayda 125B, which I've noticed have increased their wall thickness from 2mm to 3mm. This extra 1mm on each side is enough to make the board hit the ridge on the bottom plate, so you can't close the pedal up. I hate to throw out these boards (this is the 4th revision of the design), so I may just get a big order of boxes from another supplier that would allow the boards to fit and offer those pre-milled with the boards.

So anyway, Space Heater. I was asked a couple years ago to design a super simple tube preamp with just gain and level controls for people that just wanted simple tube warmth with a little bit of grit but with no tonestack. Space Heater is what I came up with. It's a great place to start if you're looking to get into tube circuits due to its simplicity, and it's the basis of what I ended up with in this thread.

It's supposed to fit in a 125B enclosure with top-mounted jacks. Like my Black Eye design it uses a separate footswitch board and a ribbon cable between the two for easy wiring.

 

[jimilee]

You mean the lip on the backplate? That can be sanded or shaved right off. I’ve done that on way more than one occasion.

 

[andare]

OOh mama!

 

[Harry Klippton]

Hey Nathan, you ever thought about doing a tube pedal preamp with an ef86 and 6 position rotary like the normal channel on a DC-30? Would it even work like your 12ax7 designs? Ever since I built my TC15, I love the normal channel

 

[cwsquared]

So, ...

 

[andare]

Will this work only with Lumberg jacks? They have been out of stock forever where I live.

 

[peccary]

Will this work only with Lumberg jacks? They have been out of stock forever where I live.

If you can buy the stereo Lumbergs, the additional tab is pretty easy to remove and once you do that they are exactly the same as the mono jacks. That's what I ended up doing when I couldn't find any of their mono jacks anywhere.

 

[vigilante398]

You mean the lip on the backplate? That can be sanded or shaved right off. I’ve done that on way more than one occasion.

Correct, I've done it as well, I just feel weird asking people to do it on something they bought from me. So if you're doing the enclosure yourself you're more than welcome to do that to a Tayda enclosure, but I'm going to get some different ones in later, probably from Stompboxparts since they're like a 4 hour drive from here and they deliver fast. Once I confirm those fit I'll start offering the boards with pre-milled enclosures as an option.

Hey Nathan, you ever thought about doing a tube pedal preamp with an ef86 and 6 position rotary like the normal channel on a DC-30? Would it even work like your 12ax7 designs? Ever since I built my TC15, I love the normal channel

The thought never even crossed my mind...

Seriously though, my main amp right now is a Ceriatone "Muchle$$" Lightning, and I'm on the waitlist for a DC-30 right now. I love love love love love Matchless tone. I messed up the pinout on the EF86 on this one so I haven't boxed it yet, but it should be an easy enough fix, just need to find the time for it. Oh I don't have a 6-way rotary that I really like though, so I used an 8-position and added a couple more settings to the tone control.

So, ...

I'm always happy to take your money, I just need to get some non-Tayda enclosures in to make sure they'll fit, then I'll get them up for sale.

Will this work only with Lumberg jacks? They have been out of stock forever where I live.

It was certainly designed for Lumberg jacks, those are the ones I use for everything. There's enough room in the box that you could get away with moving the board down a little and using different jacks, or moving it up a little and putting in side-jacks. Keeping Lumbergs on hand has been difficult lately, and I've been trying to find a way to use something else, but there just really isn't anything out there as convenient as the Lumbergs. The stereo model do seem to be a little easier to source, but I've seen those go out of stock as well.

 

[music6000]

Well I have good news and bad news about this one. The good news is I finally got a design that works perfectly. It sounds exactly the way it's supposed to, the voltage is holding right where it's supposed to be, and it looks great. The bad news is apparently it doesn't fit in all 125B enclosures. When I designed the board I used the Hammond measurements as a size reference, and I should have 2.44" between the ridge on the bottom plate. The board was designed to be 2.36" wide, which I figured would be enough. But I put it in a Tayda 125B, which I've noticed have increased their wall thickness from 2mm to 3mm. This extra 1mm on each side is enough to make the board hit the ridge on the bottom plate, so you can't close the pedal up. I hate to throw out these boards (this is the 4th revision of the design), so I may just get a big order of boxes from another supplier that would allow the boards to fit and offer those pre-milled with the boards.

So anyway, Space Heater. I was asked a couple years ago to design a super simple tube preamp with just gain and level controls for people that just wanted simple tube warmth with a little bit of grit but with no tonestack. Space Heater is what I came up with. It's a great place to start if you're looking to get into tube circuits due to its simplicity, and it's the basis of what I ended up with in this thread.

It's supposed to fit in a 125B enclosure with top-mounted jacks. Like my Black Eye design it uses a separate footswitch board and a ribbon cable between the two for easy wiring.

View attachment 29542
View attachment 29543

Does the Tayda lid only foul on the Ribbon, just file that part if the Lid Ridge flush!?
That looks like a Tayda in the Pic????

 

[Robert]

Oh I don't have a 6-way rotary that I really like though, so I used an 8-position and added a couple more settings to the tone control.

You can get those 16mm rotaries in 2 - 8 positions, they just aren't stocked at the most common places.

I have some 5-positions here waiting for a couple projects.

 

[vigilante398]

Does the Tayda lid only foul on the Ribbon, just file that part if the Lid Ridge flush!?
That looks like a Tayda in the Pic????

It's not the ribbon, it's the very corner of the PCB that hits it. The lip is just barely to the side of the ribbon. That is a Tayda box in the pic, that's how I know the Tayda box lids don't close

You can get those 16mm rotaries in 2 - 8 positions, they just aren't stocked at the most common places.

I have some 5-positions here waiting for a couple projects.

Good to know, thanks! I've seen them in 2 and 4, didn't know they came in others. But I have a bunch of 8-position on hand, so I figured may as well.

 

[Robert]

Yeah that's what I usually do as well. More is more, right?

 

[andare]

If you can buy the stereo Lumbergs, the additional tab is pretty easy to remove and once you do that they are exactly the same as the mono jacks. That's what I ended up doing when I couldn't find any of their mono jacks anywhere.

I've never seen stereo Lumbergs locally.
Maybe Mouser has them but shipping is 20 euros unless I spend at least 200 euros. I gave up on them after waiting forever for certain parts to become available, which I found elsewhere.
I'll keep looking.

 

[HamishR]

Speaking of the Ceriatone Matchless clones (sorry for the derail) I recently used a Ceriatone chassis and faceplates along with MM transformers to build a Lightning for a friend. I found the circuit sounded good but was so over-filtered it felt stiff to play. So I compared the schematic with the original Voxes and managed to reduce the number of filter caps almost by half (!) with no ill-effects but a marked improvement in feel. And they can be rather hot in the bias. You can "cool them down" to 100% plate dissipation with no loss of feel or tone but it may just help your power tubes last a lot longer. But you probably already know this!

 

[music6000]

Speaking of the Ceriatone Matchless clones (sorry for the derail) I recently used a Ceriatone chassis and faceplates along with MM transformers to build a Lightning for a friend. I found the circuit sounded good but was so over-filtered it felt stiff to play. So I compared the schematic with the original Voxes and managed to reduce the number of filter caps almost by half (!) with no ill-effects but a marked improvement in feel. And they can be rather hot in the bias. You can "cool them down" to 100% plate dissipation with no loss of feel or tone but it may just help your power tubes last a lot longer. But you probably already know this!

Isn't the Matchless a clone of sorts of the AC30.
I believe the AC were noted for catching on fire back in the day from running too hot!

 

[HamishR]

Yeah that's why I consulted the Vox schematics - The Lightning is very much a Vox-style amp. I had recently built Mojo's version of an AC15 but with an GZ34 instead of an EZ81 and several other changes and the difference in filtering is hilarious!

I'm not sure if the "Vox AC30 catching fire" thing was because of the bias or the cab's lack of ventilation. But Matchless amps typically run way too hot in the bias and they really don't need to. Biasing at 140% doesn't improve your tone. If anything they sound better at 100%. Biased too hot can make them sound too bright to me, and in an unpleasant way.

 

[music6000]

Yeah that's why I consulted the Vox schematics - The Lightning is very much a Vox-style amp. I had recently built Mojo's version of an AC15 but with an GZ34 instead of an EZ81 and several other changes and the difference in filtering is hilarious!

I'm not sure if the "Vox AC30 catching fire" thing was because of the bias or the cab's lack of ventilation. But Matchless amps typically run way too hot in the bias and they really don't need to. Biasing at 140% doesn't improve your tone. If anything they sound better at 100%. Biased too hot can make them sound too bright to me, and in an unpleasant way.

I'm curious to know how the Trainwreck Rocket amp is set up as it's a hotrodded AC30 type from what has been written.

 

[Harry Klippton]

The thought never even crossed my mind...
View attachment 29563
Seriously though, my main amp right now is a Ceriatone "Muchle$$" Lightning, and I'm on the waitlist for a DC-30 right now. I love love love love love Matchless tone. I messed up the pinout on the EF86 on this one so I haven't boxed it yet, but it should be an easy enough fix, just need to find the time for it. Oh I don't have a 6-way rotary that I really like though, so I used an 8-position and added a couple more settings to the tone control.

This is tight. I was thinking just the ef86 channel, but you said why not both? I like it. I want it. Please and thank you

 

[Betty Wont]

If you can buy the stereo Lumbergs, the additional tab is pretty easy to remove and once you do that they are exactly the same as the mono jacks. That's what I ended up doing when I couldn't find any of their mono jacks anywhere.

I use the stereo ones all the time. But why remove the extra prong? It doesn't do anything if you don't hook anything up to it, the solder tab can be bent down flush out of the way if needed, and your plug will have a tighter connection to the jack.

 

[peccary]

I use the stereo ones all the time. But why remove the extra prong? It doesn't do anything if you don't hook anything up to it, the solder tab can be bent down flush out of the way if needed, and your plug will have a tighter connection to the jack.

I don't know why I do half the things I do.