Valve amp: help me understand valves

[Bufo Bill]

Okay,I am a recent convert to Hifi having set up a mono system for inherited Classical 78's. I have a Quad ESL 57, a Rega RP3, and a salvaged Leak Stereo 30 amp. This all sounds lovely, but my head has been turned by a Quad II amp that I heard at a friend's home. The story of Quad fascinates me, and the Quad II looks like something Jon Pertwee's Doctor Who would create to defeat the Autons (this is a good thing).
Of course the sound blew me away, but valves and valve amps are all new to me as a child of the Cd generation. I have learned through the Internet and my friend the following: why it is called a valve; a rough idea of the different types and how they work and that with Quad II's that the GEC and Mullard Tubes are considered the best. My questions mainly have to do with maintenance such as when do I replace the valves? What do I need to look for in replacements? Are the expensive Mullard and GEC's really worth it?These are questions I cannot even contemplate answers to by myself, so I really need your help. I would like to state that I understand the need for a preamp control unit ( I have found and bought a QC II UNIT ) and that this is a project I have carefully considered and want to continue with, but at this point I am on the fringes of my knowledge and need your help to continue. All the best from Bill.

 

[expat_mike]

Hello Bill,

Welcome to the forum.

You have obviously spent a fair bit of time already researching valve based hifi. There are many fans of valve amps on the forum, and I am sure that some of them will soon provide some advice/guidance.

 

[Bufo Bill]

Thanks for the warm welcome Mike!

 

[Covenanter]

Try Googling "Valve rolling".

Chris

 

[Rethep]

Nice try, those 'old school' valve-amps but try newer brands like Cayin (1400 euro), some Prima Luna (2200 euro) or more expensive Line Magnetic 518 (3500 euro) or Artephonos Ensemble (4000 euro). All different tubes. Have a listen.

Don't bother about changing tubes. 5000 hours for powertubes means a lot of listening hours.

 

[Bufo Bill]

I was not aware of that term and it seems to be the key to finding the info I needed.

Yowzer because that seems to be a whole can of worms I have wondered into!

Many thanks for the tip off.

 

[The Magus]

hi Rethep 5000 hours that is only a year, what happen if someone dont change the valves? would the amp broke? what is the cost of a valve? and is it easy to change a valve, can we use any valve? what if the valve is inside the amp, can we change ourselft, is not that dangerous?

 

[FennerMachine]

Make sure any amp you buy can handle very low impedance, Quad Esl 57 can dip very low.
Maybe contact Quad and ask them about what valves would be best?
As they made and still service the speakers and amps they should know.

 

[Bufo Bill]

Make sure any amp you buy can handle very low impedance, Quad Esl 57 can dip very low. Maybe contact Quad and ask them about what valves would be best? As they made and still service the speakers and amps they should know.

hi, thanks for the replies. The amp I have my heart set on is a Vintage Quad II, which were designed for the 57's I believe.

I like the suggestion of asking Quad, but I can't find a link or number, I just keep getting the main Quad website.

Many thanks from Bill

 

[chebby]

I like the suggestion of asking Quad, but I can't find a link or number,

Quad Electroacoustics

IAG House, Sovereign Court, Ermine Business Park, Huntingdon, Cambridgeshire PE29 6XU
Phone:01480 447700

 

[Rethep]

hi Rethep 5000 hours that is only a year, what happen if someone dont change the valves? would the amp broke? what is the cost of a valve? and is it easy to change a valve, can we use any valve? what if the valve is inside the amp, can we change ourselft, is not that dangerous?

- 5000 hours is only a year but you are not supposed to keep your valve-amp on standby! So when you listen 3 hours a day that means 4 years.

- When not changed, valves will not blow, biut only sound dull(er)

- Valves are different in price. EL 34 or KT 88 will be 50 euro's a piece or so matched (that is 200 euro's for 4 of them every 4 years). 300 B or 845 or 2A3 will be (much) more expensive, especially when bought matched.

- If the amp has 'automatic bias' or (on the outside) adjustable bias it is no problem to change the valve by yourself. It is wise, considering high voltage or temperature, to wait 15-30 minutes after turning it off.

 

[chebby]

Yikes! That is an expensive hobby right there with just the valves. I thought printer ink cartridges were bad enough. (And I'll bet they all need replacing just after the car's MOT and the vet bills and Christmas.)

 

[Bufo Bill]

Quad Electroacoustics

IAG House, Sovereign Court, Ermine Business Park, Huntingdon, Cambridgeshire PE29 6XU

Phone:01480 447700

Many thanks!

 

[Covenanter]

I had a look at the circuit diagram for a Quad II and you couldn't get anything much simpler. The performance is going to be highly dependent on the quality of the components so it's worth looking for matched sets of valves but you might pay big numbers for them. You are going to get a lot of THD with this circuit but it will be friendly distortion so you might like it.

I'd be tempted to replace all the resistors and capacitors with modern low tolerance components to give more accurate circuits and longer life. The key components are going to be the output transformers and the originals should be fine and you would I suspect struggle to find better modern ones.

Have fun!

Chris

 

[Rethep]

Yikes! That is an expensive hobby right there with just the valves. I thought printer ink cartridges were bad enough. (And I'll bet they all need replacing just after the car's MOT and the vet bills and Christmas.)

When your amp is a few 1000 euro's that is not a big amount. And, If your listening 3 hours every other day they will last 8 years! That reduces the cost.

 

[lindsayt]

According to this: http://www.keith-snook.info/quad-ii-valve-power-amplifier.html

The total THD of the Quad II will be below 0.25%.

That's inaudible.

If it's inaudible, there's no way I'd describe it as "a lot". I'd describe it as insignificant. So insignificant that it's not worth mentioning. Except when mentioning it as a correction to someone else that has described it as "a lot".

Bufo Bill, there are significant differences in how different valve amps sound. If you can, try a few different ones to see which you like best.

I like the very lowest powered valve amplifiers the best - of the ones I've tried so far.

Every valve amp I've owned has sounded really bad when cold. Flat and undynamic. After 10 to 15 minutes they come on song. After 40 mins to 1 hour they really come on song.

For the all important midrange I prefer my valve amps to my solid state ones. For the bass I prefer my solid state amps.

I like to always turn my valve amps off when not in use. It's not just the electricity and valve wear savings. It's the safety.

Mullard valves have a fantastic reputation. There are plenty of other NOS type valves from other manufacturers that are worth getting. It all depends on the valve type.

 

[Covenanter]

According to this: http://www.keith-snook.info/quad-ii-valve-power-amplifier.html

The total THD of the Quad II will be below 0.25%.

That's inaudible.

If it's inaudible, there's no way I'd describe it as "a lot". I'd describe it as insignificant. So insignificant that it's not worth mentioning. Except when mentioning it as a correction to someone else that has described it as "a lot".

Bufo Bill, there are significant differences in how different valve amps sound. If you can, try a few different ones to see which you like best.

I like the very lowest powered valve amplifiers the best - of the ones I've tried so far.

Every valve amp I've owned has sounded really bad when cold. Flat and undynamic. After 10 to 15 minutes they come on song. After 40 mins to 1 hour they really come on song.

For the all important midrange I prefer my valve amps to my solid state ones. For the bass I prefer my solid state amps.

I like to always turn my valve amps off when not in use. It's not just the electricity and valve wear savings. It's the safety.

Mullard valves have a fantastic reputation. There are plenty of other NOS type valves from other manufacturers that are worth getting. It all depends on the valve type.

Well the THD will be a lot higher than in a modern SS amplifier if you want me to put it like that! But I'm not knocking the amplifier, I like classic simple circuits like this.

I found a nice article in Stereophile where someone revamps a Quad II. I'd post a link if I could do that here but a Google will find it.

Chris

 

[lindsayt]

Why mention THD and describe it as being "a lot" if it's inaudible?

For anyone who is not aware of how high THD has to be to be audible you'd be giving the wrong impression that in this respect the Quad II would sound worse than a typical solid state amplifier.

When the reality is that it would sound no different from a THD point of view. And any sonic differences between a Quad II and a solid state amplifier would be down to other factors.

 

[chebby]

0.25% is negligible compared to the hoofing great dollops of distortion you get with loudspeakers (even really good ones).

 

[Al ears]

Mine takes about 15-20 minutes to be at its best and fwiw I use Electro Harmonix valves as I find they are the best for the money.

 

[NSA_watch_my_toilet]

-> Current coming in the amp

->Curren goes through the valve

-> in the valve there is gas and special architecture, it boost the power

->power raised coming out

That's a valve

 

[chebby]

-> Current coming in the amp

->Curren goes through the valve

-> in the valve there is gas and special architecture, it boost the power

->power raised coming out

That's a valve

I thought they were 'vacuum tubes' because they contained a vacuum.

 

[The Magus]

thanks for the information it sounds cool about valves.

so you can use any valve to any amplifier that have automatic bias?

 

[FennerMachine]

0.25% is negligible compared to the hoofing great dollops of distortion you get with loudspeakers (even really good ones).

Just to add to your point, didn't Quad do a comparison between their valve and solid state amps?
Unless pushed too hard no one could tell which amp was which.

If the OP likes the Quad II amp with the ESL 57 why spend hours faffing around trying other amps?

Buy one, maybe get Quad to service it, job done!

 

[Rethep]

so you can use any valve to any amplifier that have automatic bias?

No not any, but if they have the same pin configuration, valves of the same 'family' can be interchanged. Look on the internet for 'families of valves'.