What audio system do you have, or plan on getting?

[AnotherSpin]

Where do you buy them?

If I wanted to buy Neutrik products, I would search online. For example, here: https://www.mouser.fi/c/connectors/audio-video-connectors/. I'm sure there are various online sources. Also, I would buy a simple ready cable, but that's just me; someone else might want to build their own, which is understandable.

[Valentino]

Mouser is a good source, also Elfa Distrelec which I have been using for my projects, and RS Components (I believe the former is owned by the latter now). I also second buying readymade, but 3-pin Mini XLR (Male of female?) to TRS female is not common.

[Dry Brett Kavanaugh]

The Leak is decked out with EL84(4) EC83(3) and GZ34 rectifier. Another Spin makes the point that tubes change sound - they do. Through luck rather then judgment, I fitted Amperex "Bugle Boy" EL84s. A noticeable improvement in sound and without tempting fate possess longevity. I'm very taken with them.

Border Patrol (unable to post picture as being repaired) is a completely different animal being single ended unlike the push-pull Leak. This amplifier is built around two Western Electric 300B valves. I have the same WE tubes from new and to replace would be near impossible as not sure if they are still in production and cost would be prohibitive anyway. This did worry me even with alternatives available. I looked up the projected life-span of a WE which up to a point put my concerns to rest.   

Do you mean ECC83 for pre-tubes? I think it's like 12ax7 in the USA specification. As for Amperex, I don't have Amerex, or any Dutch, tubes. I'm curious (and envious)!

[Irons]

Do you mean ECC83 for pre-tubes? I think it's like 12ax7 in the USA specification. As for Amperex, I don't have Amerex, or any Dutch, tubes. I'm curious (and envious)!

Conveniently - other tube/valve amp manufactures take note - Leak inscribe required tubes clearly on casing. My ECC83's are Mullards.

[Kalevala]

After faultless service my 300B valve/tube amp popped. Valves remain working so hopefully they are not the fault. However, something has failed as music no more! Fortunately an electronics engineer a ten minute drive, I dropped my amp off to Henry yesterday.
I have back up of a Leak Stereo 20 circa late 1950's early 1960's, purchased 20 odd years ago. I had a few modifications (Henry again) and hid the Leak away and forgot about it.

 

With some trepidation I powered it up - after removing a covering of dust. Valves glowed, so good start. Next, some music! I am aware that listening to Hi-Fi components, different can be mistaken for better. Even so the Leak sounds bloody good! I'm not saying superior then my much more expensive Border Control 300B but admit the thought crossed my mind, which with some difficulty I'm trying to banish.    

Hope that you get your "baby" back soon, repaired and that the cost is not too dear.

K

[Mandryka]

@Irons Ask Henry what he thinks about tube rolling.

[71 dB]

If I wanted to buy Neutrik products, I would search online. For example, here: https://www.mouser.fi/c/connectors/audio-video-connectors/. I'm sure there are various online sources. Also, I would buy a simple ready cable, but that's just me; someone else might want to build their own, which is understandable.

Thanks for this link! Looks good. 

[Dry Brett Kavanaugh]

Conveniently - other tube/valve amp manufactures take note - Leak inscribe required tubes clearly on casing. My ECC83's are Mullards.

I want to have Mullards tubes someday. I have Matsushita 12ax7 and EL 84, which were (presumably) manufactured based on Mullards specifications and with Mullards eqipments.
All of my amps are single-end amps. How do you like the push-pull amp? What's the advantage? What kind of music/instruments is it good for?

[Irons]

I want to have Mullards tubes someday. I have Matsushita 12ax7 and EL 84, which were (presumably) manufactured based on Mullards specifications and with Mullards eqipments.
All of my amps are single-end amps. How do you like the push-pull amp? What's the advantage? What kind of music/instruments is it good for?

As I mentioned above different does not necessarily equate with better. Certainly a different sonic sound-stage between push pull Leak and single ended Border Patrol. In a nutshell, Leak sounds more powerful and BP more detailed.
For me convenience wise, the Leak has one big advantage over BP with self-biasing valves/tubes. Garry Dews when designing the Border Patrol found this detrimental to sound. Every 3 to 6 months or so, it is required to bias both Western Electric tubes with a digital multimeter. Removing bottom plate and delving into the innards of the amp fills me with dread! As we know there are high voltages present in tube amps! Garry emigrated to US some time ago and I would be surprised if he would be allowed to market such a setup over there.

[Mandryka]

As I mentioned above different does not necessarily equate with better. Certainly a different sonic sound-stage between push pull Leak and single ended Border Patrol. In a nutshell, Leak sounds more powerful and BP more detailed.
For me convenience wise, the Leak has one big advantage over BP with self-biasing valves/tubes. Garry Dews when designing the Border Patrol found this detrimental to sound. Every 3 to 6 months or so, it is required to bias both Western Electric tubes with a digital multimeter. Removing bottom plate and delving into the innards of the amp fills me with dread! As we know there are high voltages present in tube amps! Garry emigrated to US some time ago and I would be surprised if he would be allowed to market such a setup over there.

This is the biggest problem with my Radford, though I don't have to remove the bottom plate, just stick probes in various places and turn a screw. I'm not sure what the consequences are of not checking the bias. It's a pain in the neck.

[Irons]

This is the biggest problem with my Radford, though I don't have to remove the bottom plate, just stick probes in various places and turn a screw. I'm not sure what the consequences are of not checking the bias. It's a pain in the neck.

Turning a screw! I wish. After turning (heavy) amp on side and removing bottom plate, I have to connect red probe to Cerafine Capacitor and the black probe to one of valve's anodes and adjust bias pots to required DC volts. Repeat with other valve - thankfully two not four - it does not end there, as adjusting one changes the other! So repeat the process multiply times. After getting close, I then connect red probe to the anode of the second valve and bring values to 00.00 or near. One false move and I'm up in smoke! Poking around inside a valve amp by a non-technical person is a dangerous business and not ideal.

Did you visit Henry? Why I ask, he has pulled down his old house and built a new one. I couldn't believe my eyes.    

[Kalevala]

Turning a screw! I wish. After turning (heavy) amp on side and removing bottom plate, I have to connect red probe to Cerafine Capacitor and the black probe to one of valve's anodes and adjust bias pots to required DC volts. Repeat with other valve - thankfully two not four - it does not end there, as adjusting one changes the other! So repeat the process multiply times. After getting close, I then connect red probe to the anode of the second valve and bring values to 00.00 or near. One false move and I'm up in smoke! Poking around inside a valve amp by a non-technical person is a dangerous business and not ideal.

Did you visit Henry? Why I ask, he has pulled down his old house and built a new one. I couldn't believe my eyes.    

Good for him!  Hopefully, he's now living in a warmer, more comfy and in a more energy efficient home.

K

[Mandryka]

Did you visit Henry? Why I ask, he has pulled down his old house and built a new one. I couldn't believe my eyes.    

Yes, I last saw him about a year ago,  he'd been building the new house for years and hadn't finished, has he finished now? There's a reason he did it, but I forget. He was doing all the building himself because he feels that tradesmen aren't good enough.

What actually happens if you don't adjust the bias on a valve amp? I don't really know what bias is.

[AnotherSpin]

Yes, I last saw him about a year ago,  he'd been building the new house for years and hadn't finished, has he finished now? There's a reason he did it, but I forget. He was doing all the building himself because he feels that tradesmen aren't good enough.

What actually happens if you don't adjust the bias on a valve amp? I don't really know what bias is.

There were times when I tweaked the lamp settings using a voltmeter for monitoring. I don't remember hearing any difference.

[Mandryka]

There were times when I tweaked the lamp settings using a voltmeter for monitoring. I don't remember hearing any difference.

So it doesn't explode or anything like that?

[AnotherSpin]

So it doesn't explode or anything like that?

For all the years of my interest in tube equipment, I don't recall a single case where a tube exploded just because the bias wasn't adjusted.

[ultralinear]

What actually happens if you don't adjust the bias on a valve amp? I don't really know what bias is.

The bias voltage sets the operating point for the valve.  Generally the idea is to get the most gain for the least distortion.  As the valve ages the characteristics will change, and the bias may need adjusting to keep it in the sweet spot.  If you don't do this then you may be slightly down on power or up on distortion, but that wouldn't usually be very noticeable until the valve was on its last legs.

[Mandryka]

This is from another forum, Pink Fish Media, but quite informative

Bias is used in both SS and valve amps to partially switch on the output devices and hence "smooth over" the transition from one device to another, lessening crossover distortion. If both devices remain on at all times then this is class A.

Valves are naturally "on" with no voltage on their control grid. This is opposite to standard bipolar transistors and mosfets which do not conduct until a forward bias voltage is applied.
Hence in a valve power amp with the very confusingly named "fixed bias" (fixed bias is adjustable usually but cathode bias/self bias is not), such as the STA25 (STA15 is cathode bias IIRC) a negative voltage is applied to the grids along with the signal waveform, and this negative bias sets the "amount of class A" ie how hot the output valves run.

Fixed bias valve amps generally give more power than cathode bias for a given type of output valves.

If you never check it and adjust as necessary? It is made adjustable because valves leave the production line with a tolerance on transconductance, measured usually as mA/V. Hence to get the manufacturers recommended bias current, set by the negative bias voltage on the grid remember (usually -50V ish but it varies), bias adjustment pots are usually provided.

These set both the bias and the balance between the output valves.

New valves are rarely perfectly matched and can wear at different rates in use. So if you never check the bias it can often mean the current can drop as transconductance reduces with valve wear, resulting in increased distortion.

Also if they wear at different rates the push and pull become less well "mirror imaged" to each other, again resulting in increased distortion, but also increased mains hum (a bit beyond the scope of this...).

Worst of all is that as valves age they can "outgas" and become a little "soft" which can result in a form of runaway operation where the valves overheat, draw too much current and could threaten the output transformers etc... this is very much a worst case scenario but keeping an eye on bias can show this up early before it ends in glowing anodes!

It should be set and balanced with new valves then kept an eye on in the early days of new valves as they "settle in".
Then check it every month or two. Poorer modern valves from China etc are more likely to drift and need adjustment than quality NOS valves.... (there can be another story there due to the age of NOS valves in some cases but rare so lets not confuse things by going there!)

With top quality NOS valves and a reliable topology that doesn't unduly thrash the valves you should be OK to check less often, but better to check too often than not enough.

More often than not a small resistor, often 1R, is included in the cathode circuit of each valve and you monitor the small voltage (mV's) dropped across this resistor to indicate the actual current, hence no high voltages involved.

[Irons]

The bias voltage sets the operating point for the valve.  Generally the idea is to get the most gain for the least distortion.  As the valve ages the characteristics will change, and the bias may need adjusting to keep it in the sweet spot.  If you don't do this then you may be slightly down on power or up on distortion, but that wouldn't usually be very noticeable until the valve was on its last legs.

The fall off in performance in my Border Patrol is noticeable. I thought the object of exercise was to keep DC voltage of each valve at a same or similar value. Garry Dews told me it is not so important the actual value (for my BP optimal current on meter 9.31) more that the valves are are set at near as possible the same. It may be the case, only a guess, that bias is more of importance for a 300B? 

[Irons]

Yes, I last saw him about a year ago,  he'd been building the new house for years and hadn't finished, has he finished now? There's a reason he did it, but I forget. He was doing all the building himself because he feels that tradesmen aren't good enough.

What actually happens if you don't adjust the bias on a valve amp? I don't really know what bias is.

Thanks for post above. Explains clearly what I am attempting to say.

The house that Jack Henry built is amazing. As you say, taken years. Considering he is an electronics engineer by trade to do this is a jaw-dropping feat.