Blackstar Dept 10 Valve Pedals

[elfwash]

I read with interest, the recent review of the Blackstar Valve pedals in the
current issue.
I don't actually play Guitar, but wonder if I could use a line input to drive
the pedals, either from a Synth, or within an insert loop from a mixing desk ?
I like the driven Valve sound, and these pedals even come with USB out.
Great for quick captures into the box.
A guitar pickup must be a fairly low level, so I wonder if a line level signal would
be too high and overdrive the overdrive as it were ?
A Synth output could be turned down, and I suppose an insert could be too, lowering the input gain. But whether the pedal woud really still be happy ?
And whether SNR is still acceptable.
I could make a little attenuation box, active or passive, if that would help.
What do you think ?

[ef37a]

Hello Elfwash and welcome. I cannot find any noise or level specifications for the pedals but, knowing the Blackstar design philosophy, the noise levels will be as low as is practicable for this class of device. In two words "bloody good!"

Since the 'raw' supply is 9V I would expect the operating level to be around -10dBV = 300mV. If you are operating at +4dBu* ~= 1V then a 10 to 15dB attenuator would indeed be advisable. 22k in series with 10K gives you almost exactly 10dB attn 8k2 gives 11dB and you can make the lower resistor lower for more chop. Since the input resistance is very high at 1M this will not affect the calculation.

If any 'lab rats' at Moulton Park are looking in I would be obliged if they could send me a spec test sheet? I have also just thought that the pedal might have + and - 12V rails? The valve heater would pull 300mA at 6.3V and that is a big chunk out of the stated 500mA. 12V means just 150mA. If indeed the total LT supply was 24V then the headroom would be close to studio spec.

*The guitar electronics world has long embraced the far more logical One Volt as its dB reference!

Dave.

[James Perrett]

As Dave says, the normal line levels are likely to be slightly too high for a pedal. However, I've incorporated pedals in a mixer setup by sending the audio from an aux bus and then returning the signal to an unused line input with the gain set a little higher than normal. Sending from an aux bus means that you have control over the level that you send to the pedal and also means that you can send more than one source through the pedal.

[Wonks]

Sticking a clean boosted signal into a drive pedal or an overdrive (typically set for low gain, high output) before a distortion pedal is fairly standard practice in the guitar world for an even more ‘gainy’ sound with a slightly different character to the original end pedal in the chain.

A hotter clean input signal would normally just mean you don’t have to turn the gain control up quite so much to get the same level of drive.

Of course you may only want a very low level of drive for adding a bit of edge, in which case you do have to be careful of the level going in. But for filth, it’s not really an issue.

[elfwash]

Thank you all for the quick informative replies.
Knowing that a 9V supply may expect a level of 300mV is usefull info,
as there are several line (-10dBv ) outputs on my desk and the line outs
on the synths will be around that too.
The marketing claims a 200+ V tube rail, but that should be isolated from
the audio in's and out's.
Also thanks for the resistor value info.
And James, thanks for the aux buss idea.
I would just have to watch the levels.

[ef37a]

Thank you all for the quick informative replies.
Knowing that a 9V supply may expect a level of 300mV is usefull info,
as there are several line (-10dBv ) outputs on my desk and the line outs
on the synths will be around that too.
The marketing claims a 200+ V tube rail, but that should be isolated from
the audio in's and out's.
Also thanks for the resistor value info.
And James, thanks for the aux buss idea.
I would just have to watch the levels.

I am quite sure the 200V is still derived from the 'diode pump' circuit of the original HTs with, no doubt some refinements although the original was very reliable.
"Isolation" you can be very sure of. The 200V would have to get past 450V capacitors and at least two op amp stages to 'getcha'! I never had a capacitor fail in any Blackstar product.

I actually used a scrap power PCB to make a 48V phantom power unit from a 20V DC supply. Very good regulation and low ripple.

Dave.

[Arpangel]

These pedals look great, I don’t have, any distortion, drive pedals.
Thanks for nothing, big trouble again.

[ef37a]

These pedals look great, I don’t have, any distortion, drive pedals.
Thanks for nothing, big trouble again.

Well Arp' I doubt a man of your electronics resources needs all the gizmos on those pedals? Not short of an interface for instance?

So, you could look around for one of the older HT pedals? The HT-DUAL is really versatile being in effect a 3 channel effects pedal. They were a bit 'Marmite' on the market because they are taller than standard 9volt pedals and needed a special 22V supply. Awkward then to integrate into your common pedal board but I do not recall anyone complaining about the sound quality! Since you are not a ballet dancing gitist the pedal should suit you sir.

The early jobs are all 'thru hole' components so easy to fix and Blackstar's charges for a refurb are pretty low. But really the only things that failed were the pots. The valve seemed to last forever!

Dave.

[Arpangel]

These pedals look great, I don’t have, any distortion, drive pedals.
Thanks for nothing, big trouble again.

Well Arp' I doubt a man of your electronics resources needs all the gizmos on those pedals? Not short of an interface for instance?

So, you could look around for one of the older HT pedals? The HT-DUAL is really versatile being in effect a 3 channel effects pedal. They were a bit 'Marmite' on the market because they are taller than standard 9volt pedals and needed a special 22V supply. Awkward then to integrate into your common pedal board but I do not recall anyone complaining about the sound quality! Since you are not a ballet dancing gitist the pedal should suit you sir.

The early jobs are all 'thru hole' components so easy to fix and Blackstar's charges for a refurb are pretty low. But really the only things that failed were the pots. The valve seemed to last forever!

Dave.

Thanks Dave, I’ll keep a look out.
They seem to be "proper" valve jobs, not just there for decoration.

[ef37a]

These pedals look great, I don’t have, any distortion, drive pedals.
Thanks for nothing, big trouble again.

Well Arp' I doubt a man of your electronics resources needs all the gizmos on those pedals? Not short of an interface for instance?

So, you could look around for one of the older HT pedals? The HT-DUAL is really versatile being in effect a 3 channel effects pedal. They were a bit 'Marmite' on the market because they are taller than standard 9volt pedals and needed a special 22V supply. Awkward then to integrate into your common pedal board but I do not recall anyone complaining about the sound quality! Since you are not a ballet dancing gitist the pedal should suit you sir.

The early jobs are all 'thru hole' components so easy to fix and Blackstar's charges for a refurb are pretty low. But really the only things that failed were the pots. The valve seemed to last forever!

Dave.

Thanks Dave, I’ll keep a look out.
They seem to be "proper" valve jobs, not just there for decoration.

They are indeed "proper" in fact virtually all the distortion comes from the two valve sections. Some naysayers have looked at 'robbed' (not by me!) schematics and said " Ugh! Just a simple 'king diode clipper!" Wrong. The circuit is a level booster with diode FEEDBACK. A poor man's compressor if you will and its purpose is to prevent excessive drive to the valve. You can have too much distortion.

Dave.

[Arpangel]

These pedals look great, I don’t have, any distortion, drive pedals.
Thanks for nothing, big trouble again.

Well Arp' I doubt a man of your electronics resources needs all the gizmos on those pedals? Not short of an interface for instance?

So, you could look around for one of the older HT pedals? The HT-DUAL is really versatile being in effect a 3 channel effects pedal. They were a bit 'Marmite' on the market because they are taller than standard 9volt pedals and needed a special 22V supply. Awkward then to integrate into your common pedal board but I do not recall anyone complaining about the sound quality! Since you are not a ballet dancing gitist the pedal should suit you sir.

The early jobs are all 'thru hole' components so easy to fix and Blackstar's charges for a refurb are pretty low. But really the only things that failed were the pots. The valve seemed to last forever!

Dave.

Thanks Dave, I’ll keep a look out.
They seem to be "proper" valve jobs, not just there for decoration.

They are indeed "proper" in fact virtually all the distortion comes from the two valve sections. Some naysayers have looked at 'robbed' (not by me!) schematics and said " Ugh! Just a simple 'king diode clipper!" Wrong. The circuit is a level booster with diode FEEDBACK. A poor man's compressor if you will and its purpose is to prevent excessive drive to the valve. You can have too much distortion.

Dave.

This is sounding even better Dave, especially the compression bit.

[ef37a]

I don't want to mislead you Tony, the "compression" is quite a crude affair as its function is to prevent the first valve being driven too hard. Therefore it will only come into play at very high levels and will not behave anything like a Fairchild!

You see if valves are driven very hard you can get 'blocking distortion' which is not at all nice. N.B. You will not overdrive and damage the pedal with a synth level input and I doubt even +26dBu from a good mixer would harm it either.

Dave.

[elfwash]

After surfing and lurking and googling, and not being a guitar player, and not
Really needing another interface, I found a couple of HT Dist pedals online
at half price. 125 for the pair.
One is new and one is used, but supposedly 'excelent condition', and 14 day returnable.
There are a few more new HT's to clear as well. A Drive pair for example. silly cheap.
All I really wanted was a driven valve output channel for the synths and VST's.
I almost wanted 2 Coopersonic Deluxe's but that's 4 times what I paid, so
silly really.
As I don't really need all that drive I may well swap the tubes for 12at's or
less even, see how it goes, I doubt they will be a stereo pair out the boxes,
one new and one burnt in.
Thanks for all the advice.

[ef37a]

After surfing and lurking and googling, and not being a guitar player, and not
Really needing another interface, I found a couple of HT Dist pedals online
at half price. 125 for the pair.
One is new and one is used, but supposedly 'excelent condition', and 14 day returnable.
There are a few more new HT's to clear as well. A Drive pair for example. silly cheap.
All I really wanted was a driven valve output channel for the synths and VST's.
I almost wanted 2 Coopersonic Deluxe's but that's 4 times what I paid, so
silly really.
As I don't really need all that drive I may well swap the tubes for 12at's or
less even, see how it goes, I doubt they will be a stereo pair out the boxes,
one new and one burnt in.
Thanks for all the advice.

No! Do not put a different triode in those pedals. The 12AX7/ECC83 pulls the least anode current when biased correctly. The 81/AT7 pulls more and the 82.AU7 even more current. The anode loads in the pedals are necessarily wee, 0.25W iirc, and you might burn them out.

In 'mainstream' valve gear these days such 'circuit bending' is usually harmless but it always pays to check. Some of the early Fender I seem to recall had 'just' high enough rated anode loads and peeps used to bugger 'em!

BTW if you have a valve amp with a front end 83 that is a bit noisier or hummier than you would like you can swap it for one in an HT. The valves are DC heated, no hum, and run at a high enough signal level that a bit of hiss is not noticed.

And! Don't swear and struggle to refit that spring clip on the valve. It was only really there for container shipping and the bottle will not shake loose by fair means without it!

Dave.

[elfwash]

Thanks very much for the advice.
I guess I'll use the AX7's then.
Turns out the new one has a 22V DC supply and the used one has a 16 VAC,
so checking on the scope, they look very different.
I doubt it is because one is new and one burnt in.
I think they may have tweeked the EQ blocks, because it's not possible
to match them at any setting.
Running one into the other sounds great though, so keepers at this price.
No problems driving them, nice input sensitivity actually.
Tempting to rack them up, with a long tail pair and a bunch of diode
configurations on switches for the ultimate mix and match overdrive.

[ef37a]

Thanks very much for the advice.
I guess I'll use the AX7's then.
Turns out the new one has a 22V DC supply and the used one has a 16 VAC,
so checking on the scope, they look very different.
I doubt it is because one is new and one burnt in.
I think they may have tweeked the EQ blocks, because it's not possible
to match them at any setting.
Running one into the other sounds great though, so keepers at this price.
No problems driving them, nice input sensitivity actually.
Tempting to rack them up, with a long tail pair and a bunch of diode
configurations on switches for the ultimate mix and match overdrive.

Checking what on the 'scope? Yes, early ones had an AC supply, no longer can be sold in EU. Don't mix them up. On something atmo will chat later.

Dave.

[elfwash]

In order to see if they would work as a matched stereo pair, I ran a sine
wave into them and found that the waveshapes were surprisingly
different.
The ISF EQ controls modified the waveshape in different ways as if they
had changed the filter configurations from old to new model.
Of course, backing right off on the input level gave me back the sine waves,
although on the new one, the higher frequencies were much more driven
than on the old one.
The old one also had a weaker low frequency response.
I didn't do any serious frequency analysing,but it was obvious the design
had been 'updated'.
Actually, in series, they compliment each other.

[Arpangel]

I don't want to mislead you Tony, the "compression" is quite a crude affair as its function is to prevent the first valve being driven too hard. Therefore it will only come into play at very high levels and will not behave anything like a Fairchild!

You see if valves are driven very hard you can get 'blocking distortion' which is not at all nice. N.B. You will not overdrive and damage the pedal with a synth level input and I doubt even +26dBu from a good mixer would harm it either.

Dave.

I would be using synths, hoping for a good valve overdrive, type sound.

[ef37a]

I don't want to mislead you Tony, the "compression" is quite a crude affair as its function is to prevent the first valve being driven too hard. Therefore it will only come into play at very high levels and will not behave anything like a Fairchild!

You see if valves are driven very hard you can get 'blocking distortion' which is not at all nice. N.B. You will not overdrive and damage the pedal with a synth level input and I doubt even +26dBu from a good mixer would harm it either.

Dave.

I would be using synths, hoping for a good valve overdrive, type sound.

Oh aye, they will do that. The response is of course aimed at guitars and guitar speakers, i.e. low bass and low treble beyond about 8kHz but there is a decent range of T&B boost available. All but the simplest pedal has speaker emulated output and should give nice results for recording.

Dave.

[Arpangel]

I don't want to mislead you Tony, the "compression" is quite a crude affair as its function is to prevent the first valve being driven too hard. Therefore it will only come into play at very high levels and will not behave anything like a Fairchild!

You see if valves are driven very hard you can get 'blocking distortion' which is not at all nice. N.B. You will not overdrive and damage the pedal with a synth level input and I doubt even +26dBu from a good mixer would harm it either.

Dave.

I would be using synths, hoping for a good valve overdrive, type sound.

Oh aye, they will do that. The response is of course aimed at guitars and guitar speakers, i.e. low bass and low treble beyond about 8kHz but there is a decent range of T&B boost available. All but the simplest pedal has speaker emulated output and should give nice results for recording.

Dave.

Thanks Dave, sounds like it’ll be OK, I’ll get one on sale or return.
I’m always a bit reluctant to fork out for distortion, as I can get it in more than one link in my recording chain, just by turning up the gain!