Hot Springs - Circuit Redesign

[Electrobumps]

Hot Springs Reverb - Modification Ideas

I love spring reverb, but I don’t love the noise issues and mechanical spring noise you can get with transients. I own the Urban 111B and Great British Spring which I use pretty regularly on projects. I have been looking at the hot springs project for a while and from the few builders’ reports, they say it sounds great.

This is how I would like to upgrade the circuit.

• Change to balanced line level to +4dbu i/o
• Change the quad op-amp and upgrade to 2 lower noise and faster dual op amps
• The grounding scheme is questionable and shielded cable should only be needed for reverb tanks in an upgraded version
• Build smoothing onto the board and use a good-quality wall transformer for DC
• Make the PCB a stereo unit instead of Mono

I would use MOD tanks as grounding can be changed by soldering. This page can search out what tanks can be used off the shelve.

These are the tanks originally recommended for the build.

1FB2B1D - Accutronics

1 -2 Springs short tanks
2 - i/p 1475 Ω
3 - 2250 Ω
4 - Decay Medium
5 - I/p grounded o/p Insulated
6- Non Locking
7 - Vertical connectors down

8EB2C1B - Mod

1 - 2 Springs short tanks
2 - i/p 600 Ω
3 - o/p 2250 Ω
4 - Decay Medium
5 - o/p Insulated, i/p grounded
6 - Non Locking
7 - Open side down


I do not have the know-how to create schematics and Gerber files. This is not something I have time to learn at this point in time. It would be great to collaborate on this build with someone who has or wants to learn those skills.

I have attached the original build article and some spring info.

 

[Zed80]

Hello, I plan to build a stereo spring reverb as well. I will read your documentations (thx for sharing). On my side I found this article :
https://sound-au.com/articles/reverb.htm
It says everything needed. The most important factor being the input impedance. 600ohm may be already too high if you have only +/-15v. The author explain that he had a 1475ohm tank and it would require a +/-35v PSU or a transformer (or may be vacuum tubes).

I intend to build the figure 5 circuit (8 to 250 ohm) because I can only find short decay tanks with 8 ohm input. The 5A circuit is simpler to build but it cannot cope with a so low input impedance.

If you don't like the vintage spring response on transients, 3 springs reverbs seem less affected by this characteristic. But personally I found them less clear and direct than the 2 springs versions.

 

[Electrobumps]

Hello, I plan to build a stereo spring reverb as well. I will read your documentations (thx for sharing). On my side I found this article :
https://sound-au.com/articles/reverb.htm

Have read this, what I like about the hot springs is the parallel springs are out of phase for noise and mechanical spring noise cancellation.

It says everything needed. The most important factor being the input impedance. 600ohm may be already too high if you have only +/-15v. The author explain that he had a 1475ohm tank and it would require a +/-35v PSU or a transformer (or may be vacuum tubes).

Parallel springs so input impedance would be halved. I was looking at the MOD 800 ohm so this would be 400 ohms input. Will read up on this.

If you don't like the vintage spring response on transients, 3 springs reverbs seem less affected by this characteristic. But personally I found them less clear and direct than the 2 springs versions.

I like 3 springs on vocals, like the Great British Spring and 2 springs from my Orban 111B tend to work better on instruments.

 

[Zed80]

Parallel springs so input impedance would be halved. I was looking at the MOD 800 ohm so this would be 400 ohms input. Will read up on this.

Re-read the page 2 of the C.Anderton article. It explicitly says that the drivers are mounted in series. Look at the figure 2. So the total impedance would double, I am afraid.

 

[Electrobumps]

Re-read the page 2 of the C.Anderton article. It explicitly says that the drivers are mounted in series. Look at the figure 2. So the total impedance would double, I am afraid.

Yes I see that now. I don't want to use transformers.

There is a good choice of tanks with 150 or 190 ohms input impedance off the shelf that could work even with the doubled I/P impedance of the tank.