FAQ's for:

 

THE EPIPHONE VALVE JUNIOR FAQ's

What about a tone control?
I have tried various tone controls (tone stack circuits) but find that they all reduce the gain significantly and you can obtain as good if not better result using a combination of voicing and the guitar tone controls.
What about valve rectifiers - don’t they give a ‘better’ sound?
Some amplifiers exhibit what is known as “sag” when a note is struck due to a drop of voltage in the power supply. This changes the attack of the note and adds to the overall tone of the amp but not everyone will see it as an improved tone.
The Valve Junior circuit and others like it (commonly referred to as “Champ” circuits after the Fender Champ) draw an almost constant current so fitting a tube rectifier will not induce SAG as there is not enough change in the current to cause sufficient voltage drop.
What about changing the speaker?
Changing the speaker will change the tone/sound of any amp. Whether it is an improvement or not is subjective. I have tried other speakers and while they do sound different they do not sound better to me. You may like a different speaker and the only way to find out is to try changing it. Weber, Jensen and Celestion all make speakers that you can use in the VJ as you have 4, 8 and 16 ohm outputs.
And, don’t forget that with the 3 speaker jacks you can use the combo as a head with almost any separate speaker cabinet.
What about a triode/pentode switch?
A triode/pentode switch is often fitted to give a reduction in output. It also changes the tone, making it darker. With Power Scaling™ there is no benefit in using the triode mode of operation to reduce the volume and in listening tests I found that most people didn’t care for the triode mode sound .
What about changing the output transformer?
While the stock output transformer is a little on the small side, it matches the output tube well and the sound is excellent. Changing the output transformer to something like a Hammond 125CSE will increase the level of clean volume and will have an effect on the tone but not everyone wants that change or will think it sounds better.
What about changing the valves?
The tubes supplied with the VJ are good quality Electro Harmonix and Sovtek valves. Changing the valves will change the tone but whether you like the change is subjective - you can’t say it’s better or worse as it’s personal.
How do I know which version I have?
Version 3 - The serial number is 14 digits and the combo has an "Eminence Inside" label and 3 output jacks. 
Version 1 and 2 - the first four digits of the serial number show the month and date of manufacture e.g. 0105 is January 2005.  Version 1 is before 1205 version two is after 1205.

 

POWER SCALING™ FAQ's provided by London Power

What is Power Scaling?
Power Scaling is a "methodology" and a performance goal. The goal is to achieve the same tone as our loud sound but at a much lower volume. The method of achieving this can be one of over sixty distinct approaches, each with countless variations. There are many approaches that reduce power but do not achieve the full benefit of Power Scaling.
Other designers made attempts to achieve Power Scaling, but never quite got there. London Power refined and fully developed the technology to allow the maximum power of an amplifier to be dialed down to whatever level a player needs.
Isn't this just like a power soak or speaker load box?
Not at all! "Speaker load boxes", "speaker emulators," and "speaker attenuators" are all forms of attenuation that are interposed between the output of a power amp and the speaker. They work for some people but are notorious for sounding "buzzy" at high attenuations.
A speaker attenuator forces your amp to be run flat out producing its full power all the time. The power that is not needed is thrown away as heat, with the required power going to the speaker. It is quieter than full-tilt, but now the speaker is isolated from the amp and cannot interact with it, so some tone is lost.
The key to Power Scaling is that it is applied to the power output tube stage itself, and so comes before the output transformer. Power Scaling allows a dynamic power range of 40dB. Most speaker attenuators alter the tone before they reach 8dB reduction. -8dB is just a little bit quieter than full blast; -40dB is literally a whisper
.
Wouldn't a 'master volume' do the same thing?
Only in specific situations. If you only play clean or you only use preamp overdrive or distortion tones, then a 'master volume' will satisfy you.
Power Scaling is the best solution for those players who incorporate some amount of output stage "effect" in their sound. This effect can be some clipping, heavy clipping, or just that cusp of compression you get in a tube power amp approaching clipping. Power Scaling allows you to live at that cusp or beyond, but at ANY loudness you need.
How clean will a Power Scale amp play?

With the Power SCale control set at maximum i.e. to provide full volume - the amp is running as it would without Power Scaling so it will give a completely unaffected clean tone.

How does Power Scaling affect tube life?
With the Power Scale dial set to any setting less than maximum, tube life will actually be extended. In accelerated tests, power tube life is as long as that of a preamp tube ... up to 100,000 hours if the tube is not mechanically upset.
This is one of the benefits of the full Power Scaling effect, referred to above. Output transformer life is also extended as it is subject to much lower voltage stress even with fully squared output signals and unexpected load disconnection
.
Couldn't a low power tube amp do the same thing?
No. A low-watt amp only has one compression point, one cusp of distortion and one loudness level through a speaker.
Power Scaling amps can play both louder and quieter than amps of less nominal power. And, the compression point stays in the same position relative to the cusp point for all settings, allowing the touch responsiveness to remain consistent.
How is this possible?
In technical terms, all that must be accomplished is to keep the "transfer curve" of the amplifier the same. The transfer curve is just the relationship between the input and output signals, but as we know, tube amps respond differently to different size signals. This trait is due to the transfer being not straight and not uniformly curved.
Think of the transfer curve like a mirror. A flat mirror that is parallel to you will reflect your image perfectly and full size. If you move the mirror away, the image is smaller but still perfect. A tube's transfer curve is like a slightly curved or rippled mirror. In this case the image is slightly distorted, but this is exactly what we wanted - it is why we chose a tube amp in the first place. So, moving the mirror farther away, reduces the size of the image but it is still perfectly imperfect.
Can Power Scaling be added to any tube amp?
The circuits can be retrofitted into existing tube amps, but... The tech doing this installation must be very good at mods - not just a good repair tech as these are two different skills.
Depending on the amp, some heatsinking or a fan might be required to cool the Power Scale circuit.
Is the Power Scale circuit just converting the unwanted audio power into heat?
No. If you only need 3W of power then only 3W is produced; if you need 29W, then you get 29W. The simplest Power Scale circuits are soft regulators, and as such, they divide the voltage available from the raw power supply between the amplifier and itself. In that voltage sharing, there will be some waste heat.
For Power Scale control settings between minimum (fully anti-clockwise) and about 12-o'clock, there will be waste heat from the Power Scale regulator. At settings between maximum (fully clockwise) and 12-o'clock, the regulator runs cool. Meanwhile, as audio power is reduced, waste power in the power tubes goes down in direct proportion, which increases their reliability.

 

THE BLACKHEART BH5H and BH5-112 FAQ's

What about other mods?
The tone stack can be made switchable for extra gain.
Changes can be made to additional resistor and cap values to alter the tone and get even more gain.
Some people fit a valve rectifier (see below).
If hum is an issue more work can be done to the valve heater circuit.
A boost footswitch can be fitted.
An octal 6V6 valve can be fitted.
What about valve rectifiers - don’t they give a ‘better’ sound?
Some amplifiers exhibit what is known as “sag” when a note is struck due to a drop of voltage in the power supply. This changes the attack of the note and adds to the overall tone of the amp but not everyone will see it as an improved tone.
The Blackheart circuit and others like it (commonly referred to as “Champ” circuits after the Fender Champ) are known as ‘class A’ amplifiers. They draw an almost constant current so fitting a tube rectifier will not induce sag as there is not enough change in the current to cause sufficient voltage drop. A London Power SUS2 kit can be fitted to induce sag in a class A single ended amp.
What about changing the speaker? (combo)
Changing the speaker will change the tone/sound of any amp. Whether it is an improvement or not is subjective. You may like a different speaker and the only way to find out is to try changing it. Weber, Jensen and Celestion all make speakers that you can use in the Blackheart as you have 4, 8 and 16 ohm outputs.
And, don’t forget that with the 4, 8 and 16 ohm outputs you can use the combo as a head with a separate speaker cabinet.
What about keeping the triode/pentode switch?
A triode/pentode switch is fitted to give a reduction in output. With Power Scaling™ there is no benefit in using triode mode of operation to reduce the volume.
What about changing the output transformer?
The stock output transformer is a pretty decent size, it matches the output tube well and the sound is excellent. Changing the output transformer to something like a Hammond 125ESE may increase the level of clean volume and may have an effect on the tone but not everyone wants that change or will think it sounds better.
What about changing the valves?
The tubes supplied with the Blackheart are unbranded valves made in China. Changing these to good quality branded valves like JJ, Electro Harmonix and Sovtek will change the tone and probably improve the reliability but whether you like the change is subjective - you can’t say it’s better or worse as it’s personal.

 

Do I need to spend £000's on an old guitar and amp to sound like my guitar hero?
Consider this; when Eric Clapton made his classic recordings in the 60's, 70's, 80's etc. he was using what were then nearly new amplifiers and guitars! When he recorded the famous "Hyde Park Concert" he was using new guitars and amplifiers.  Unfortunately there's no 'Mojo' or magic that will make you sound like Eric.  If you did spend £100,000 on an old Strat/Les Paul, Dallas Rangemaster and Marshall 1962 Combo or Fender Champ it wouldn't help (well, it might a bit).  First, because you're not Eric and second because the aging that the guitar, amp, and pedal have experienced for the past 40-plus years will have changed them from the new or nearly new state they were in when Eric Clapton used them to make history.   Would it sound good? - Yes it probably would although it could need a good service before it did.  Would you sound any more like Eric? No not really.  Eric Clapton, Dave Gilmour, Brain May etc. sound the way they do because of the way they play.  Give them a decent new guitar, a decent new valve amp and some decent new effects and you'd still know it's them playing. 

 

 

 

 
 
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

© 2008 MasterTone  Amplifiers all rights reserved