EHX - Hot Tubes (original version)

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Scruffie
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Post by Scruffie »

My Second Attempt Ever at a PCB Layout... Not The Best I'll Admit but it was a Tight One.
Not Checked But Okay at a Glance... :hmmm:

1590B with Onboard Pots, Pots Mount On the Back of the Board... 3 Jumpers but it was the best I could manage.

Based on the Gaussmarkov Schematic - http://gaussmarkov.net/layouts/hottubes ... -schem.png

Board Measures 53.34 x 53.34
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1590B Hot Tubes SS.gif
1590B Hot Tubes.gif

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Scruffie
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Post by Scruffie »

Tidied it up a bit :)
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Post by MoonWatcher »

sonicvi wrote:
Fantabulousnoise wrote:This pedal and other 4049 based pedals I've heard don't really sound anything like tube screamers. They're much more edgy and saturated sounding, even with a little clean blend.
I have a love affair with them. The edgy clipping sounds like a good dose of crossover distortion, which I know that many folks try to minimize, but it really does cut through.

The inverter based OD pedals are really sensitive to supply voltage changes - simply changing a series resistor from 47 ohms to 100 ohms to 220 ohms will all have a noticeable effect on how dynamic the pedal is, and how much usable treble content that there is. This also holds true for the small caps that bleed treble at the feedback loops. Unless you really want to mellow things out, I don't suggest going much above 47pF, and 10pF will give you a much glassier range.

The biggest issue with inverter stages is loading - the Z is not orthodox for most applications, which is why it isn't uncommon to see it either pushed by an op amp or transistor and/or recovered by an output buffer.

I also like how they handle bass heavy signals much better than op amp equivalents. The tube sound fuzz is a great building block - just don't use the subbed in Red Llama component values, as they destroy much of the character that is the essence of what is great about inverters.

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Post by MoonWatcher »

Fantabulousnoise wrote:questions: how does it react to boosters into the input?
A really nice inverter design that responds to being hit with a booster is a tube sound fuzz with the coupling caps cut down in size, as it will keep the OD sufficiently tight. And you really only need 2 or 3 inverters when you whack them with a boost, as well. I wouldn't go above a 22nF or 47nF cap - keep them small.

You might like that combo so much that you could find yourself putting it all in one box. Op amp boosters are fine, I personally like pushing with a BS170 mosfet biased for a modest voltage gain. But you can even whack one with a TS type of OD (with the gain set low) and get some neat effects.

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Post by lofi73 »

I have one of those old ones too modified for use with 220V.I was wondering when they started making those??...78-ish?.Just saw an orange one on ebay!?

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Post by Nocentelli »

I haven't got any 2M pots for the overdrive control, but I'd like a similar range of control as the original. The 2M series pot and subsequent 1M8 resistor to ground appear to form a voltage divider, so I was wondering if I'd get a similar range of gain using a 1M pot and an 820k or 1M resistor to ground?
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by Nocentelli »

Edit button mysteriously disappeared - On further reflection, if my voltage divider idea is correct, the minimum gain might be similar, but the maximum would be lower. Maybe I'll just use a switch to add a 1M fixed resistor in series for low gain/high gain.
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by astrobass »

mictester wrote:
slor wrote:Hi there,

It seems that some folks feel that the Texas Instruments TL072 is a better (less noisy) replacement for the 4558. Any thoughts on this?
The TL072 is much lower noise than the 4558, but doesn't colour the sound in the same way. Believe it or not, there is a 4558 "sound" (just like you'll find in a Tubescreamer) and it has a number of other nice properties that make it a really good device for audio use!
I found it to have a distinctive crispness to it. Attacks were more prominent. The TL072 is more transparent.

You can chip stack though, and get a bit of each while reducing the noise. Or you can replace all of the caps with higher voltage equivalents and run at 18V. Or you might even find that the 4558 sound isn't that important or possibly even detrimental to the way you want to use the pedal.

These are all filthy cheap on eBay. The LM833, LM358 and 4559 are all also very inexpensive and worth ordering a few of each, so that you can test different chips. The TL062 and TL082 are just variations on the TL072 and of the three, the 72 is the low noise version, so I'd skip the other two.

Just use a socket instead of soldering an IC directly to the board.

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Post by mictester »

voland83 wrote:4558 or tl072 or other opamps are just linear elements and cannot colour your sound, if they did, they were just a bad opamps ( really far from linear characteristic ). tone controll is realised by building integrator or differentiator circuit by means of opamps + capacitors+ resistors and/or inductors.
In fact the 4558 behaves quite differently to the TL072. It has a lower input impedance, higher output impedance, less drive capability, and recovers from overload gracefully without latching up (the TL series is notorious for this problem). A better replacement for the 4558 is the NE5532 - it has greater current drive capability and much lower noise, but recovery from overload isn't quite as graceful.
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Post by astrobass »

Though, I'll admit that when using an op amp as a unity gain buffer, the differences become significantly less noticeable.

Differences in output impedance are less significant if you use a solid state amp, and even the 4558's relatively low input impedance is minimum 300K and typically 5M per the datasheet, which is often enough unless this is the first effect in your chain and your guitar's pickups are reeeeeeally high impedance or you've got your volume knob dialed almost all the way down, or you've got something strange in your signal chain.

As soon as you start using them to actually amplify the signal however, they all have different characteristics. A good way to test the characteristics of different op amps is to build up a basic Tube Screamer, but omit the buffers and clipping diodes. Now you're left with a signal boosting stage with an EQ characteristic and an active tone stack. Use a socket for the op amp. Now you'll hear the combined effects of the input/output impedance of each op amp and as you crank the gain, you'll hear the distortion added by the op amp and its inherent tonal characteristics.

It's a bit of work, but I learned a LOT by doing exactly that. If you use 50V or higher rated caps, you can power the whole thing with 18V instead of 9V and see how that changes things (the op amps all distort much later, at higher gain settings than they normally would).

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Post by okgb »

I owned one for a short time , and I don't get it ! A friend described it as " Caustic " and that matches what I felt for sound & feel
kind of a lemon pucker dry mid-range that's too bright ...........It burns !

People get around this or mod them ?

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Post by astrobass »

okgb wrote:I owned one for a short time , and I don't get it ! A friend described it as " Caustic " and that matches what I felt for sound & feel
kind of a lemon pucker dry mid-range that's too bright ...........It burns !

People get around this or mod them ?
I've never heard of it as being a popular modding platform. It probably depends on your gear. If you have a dark sounding amp or guitar, or both, having an unusually bright distortion effect is less of an issue, there'll either be less high end content to emphasize or you'll be rolling off the highs substantially anyways.

This pedal was originally built in 1978. Lots of people were still using tube amps with reduced high frequency response, I believe humbuckers were more popular than single coils (all of the prominent guitarists I can think of from the era were using Les Pauls) and on the bass side the big trend was warm, sub-bass heavy tones. So it probably made sense at the time.

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Post by Dirk_Hendrik »

2010:
mictester wrote:
voland83 wrote:4558 or tl072 or other opamps are just linear elements and cannot colour your sound, if they did, they were just a bad opamps ( really far from linear characteristic ). tone controll is realised by building integrator or differentiator circuit by means of opamps + capacitors+ resistors and/or inductors.
Op-amps will seriously alter the signal passed through them - they are certainly not "perfect" devices! You have to consider slew rate, noise, bandwidth, available voltage swing, input and output impedance, and several other parameters. The signal out of an op-amp can never be the same as the signal in!

The 4558 (for example) has a limited slew rate and quite a poor noise floor. However, it doesn't suffer from "latch-up" problems when the output approaches the supply rail, so it's good in the distortion stages of effects. The TL072 is much wider bandwidth and much lower noise. It also has a very high input impedance and very low output impedance. It's really good for buffers, hi-fi circuits, tone controls, buffers and balanced output stages. The two devices behave quite differently despite their both being "op-amps".

I suggest you build a simple 10X gain buffer with a socket for the IC. Try different devices in there, and you'll be surprised how different they sound!

2013:
mictester wrote:
voland83 wrote:4558 or tl072 or other opamps are just linear elements and cannot colour your sound, if they did, they were just a bad opamps ( really far from linear characteristic ). tone controll is realised by building integrator or differentiator circuit by means of opamps + capacitors+ resistors and/or inductors.
In fact the 4558 behaves quite differently to the TL072. It has a lower input impedance, higher output impedance, less drive capability, and recovers from overload gracefully without latching up (the TL series is notorious for this problem). A better replacement for the 4558 is the NE5532 - it has greater current drive capability and much lower noise, but recovery from overload isn't quite as graceful.

Brilliant! Read something and hit reply, ignoring other reply's including your own! :blackeye :applause:
Sorry. Plain out of planes.

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Post by mictester »

... and your point is?

Two years more experience, and several more commercial design projects have actually made me re-evaluate the strengths and weaknesses of some well-known analogue ICs.

For example: I've completely abandoned the use of the MN32XX series of delay ICs - the older MN30XX are far better, despite needing awkward supplies. It seems that there's a virtually unlimited supply of the Panasonic originals (and if they're copies, they're damn good ones because they work so well). There's even a very high quality studio limiter that uses a pair of 3007s for feed-forward. I was surprised because I always had the impression that these were somewhat sub-standard, low quality parts. They're not - it's just that most people are too lazy to supply them with the right voltages and impedances!

I've learned a lot in the time I've been away from this forum. I've found several manufacturers blatantly ripping off some of my earlier circuits. I don't care any more. My more recent stuff is un-copyable, and I won't be giving away good ideas on sites like this any more. Any one who goes to the trouble of taking one of the recent ones to pieces will be disappointed because he will have killed a perfectly good, working effect, discovered nothing and the warranty will be void.

I was talking to a friend of mine who makes his living building guitars. These are very sought-after, and made in limited quantities (he can only make so many himself) and they command insanely high prices. He doesn't need to advertise - there's always a stream of people want instruments. He told me that he never "wastes his time" with websites like this. The vast majority of visitors to a site like this have nothing to offer - they just take. I'm not going to bother with this site (and the others) any more. I can use my time profitably, servicing the ever-growing demand for high quality effects and audio processors. I'm retiring from my full-time occupation, and will devote more time to developing effects for people who can appreciate them.

See you around (or not.....)
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Post by andrej »

mictester wrote:It seems that there's a virtually unlimited supply of the Panasonic originals (and if they're copies, they're damn good ones because they work so well).
Is there? Because the only ones I can find are hugely overpriced and in small quantities.

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Post by Nocentelli »

mictester wrote:The vast majority of visitors to a site like this have nothing to offer - they just take.
Wow. I didn't think you came to this website because of what you thought other people had to offer - I thought you came here to dispense wisdom on circuits you were familiar with from decades of experience, shared circuits you (claimed to have) invented, and consistently insist that all new parts sounded better than old ones, all capacitors of the same value sound the same, and slam those booteek boobs. Next you'll be telling us that germanium tranistors really so sound better than silicon.
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by Nocentelli »

Nocentelli wrote:
mictester wrote:The vast majority of visitors to a site like this have nothing to offer - they just take.
Wow. I didn't think you came to this website because of what you thought other people had to offer - I thought you came here to dispense wisdom on circuits you were familiar with from decades of experience, shared circuits you (claimed to have) invented, and consistently insist that all new parts sounded better than old ones, all capacitors of the same value sound the same, and to slam those booteek boobs. Next you'll be telling us that germanium tranistors really do sound better than silicon.
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by uncleboko »

mictester wrote:... and your point is?
Exactly my thought even before scrolling down :roll: :roll: :roll:

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Post by okgb »

Some countries , societies seem to promote greater arrogance but back to topic
Can this thing be made better ? better merely with the use of alternate I.C.'s ?
This is from MY ignorance and lack of experience trying different I.C.'s

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Post by astrobass »

okgb wrote:Some countries , societies seem to promote greater arrogance but back to topic
Can this thing be made better ? better merely with the use of alternate I.C.'s ?
This is from MY ignorance and lack of experience trying different I.C.'s
The 4558 in this circuit is first used as an input buffer and then used to provide a decent amount of gain.

A lower noise IC should likely result in a reduction in noise. I haven't built this circuit personally, but to me it looks like the amount of gain here should be comparable to a TS with the gain set just above 1/10. With the 4558 that does result in noticeable noise, but not a lot.

If you're going to try other ICs, make sure they have high input impedance. The TL072 is both lower noise and has very high input impedance. The LM833 is a low noise op amp designed to work well with audio and at first blush looks like a good substitute, but it has an input impedance of 175 kΩ, which is really too low to use for a buffer. The TL072 is really an excellent IC to have on hand, it's very cheap, there are a million places you can order it from (I recommend eBay), and it's ideal for use as a buffer and almost always is a reasonably effective substitute.

Failing that however, try different stuff, just use a socket for the IC. I wouldn't bother with an expensive Burr Brown op amp for this purpose though. I also wouldn't really expect it to make a HUGE difference in this circuit but please do comment back if you find it does.

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