EL-34 Integrated.

[southall-1998]

I'm thinking about buying an EL-34 integrated next year, which will go in my other room.

Hopefully around in March/April time I'll be ready to purchase.

Any EL-34 integrated that has ''self-bias'' that can be bought?

Budget will be around £400-1,300. Second hand is more likely!!

Ta!

S.

[Spectral Morn]

Audio Innovations Series 500 one of the finest of the type ever made. Buy the second version, still with the 4,8, 16 ohm taps, best output transformers. However replace the el34s with 5881 as el34s are not the most reliable of valves, because when they fail, they do so quiet spectacularly and nearly always damage the amp, blown resistors under the valve base is common after an el34 goes nuclear.


Regards Neil

[southall-1998]

Audio Innovations Series 500 one of the finest of the type ever made. Buy the second version, still with the 4,8, 16 ohm taps, best output transformers. However replace the el34s with 6l6 or 5881 as el34s are not the most reliable of valves, because when they fail, they do so quiet spectacularly and nearly always damage the amp, blown resistors under the valve base is common after an el34 goes nuclear.


Regards Neil

Can you shed some more light on this bit please. What is this ''second version''? Was there a ''first version''??

Thanks!

S.

[Ali Tait]

I recall Nick bringing a PP EL34 amp to a previous Owston that sounding very nice. I'd suggest asking him if he'd build you one.

[Spectral Morn]

Can you shed some more light on this bit please. What is this ''second version''? Was there a ''first version''??

Thanks!

S.

It wasn't an official mk2 simply a number of issues in the first versions was resolved and as manufacturing continued this version is sort of unofficially referred to as being a mk2. The way to tell is that the early amps are a satin smooth black in colour and the later a slightly textured flatter brown/black. As production continued and as cost cutting was applied, the quality output transformers were dropped so later versions don't have the three output taps so no 16 Ohm output just 4 and 8.

I would avoid the two tap version as it doesn't sound as good as the earlier ones.

Guy Sargent of pure sound can shed more light here as he worked for Audio Innovations during the latter period in its history.

The amp is a 25 watt class A (runs very hot), with a passive line level pre, active mm phono stage. It needs to be used with clear air above it, to aid cooling. I met its designer who explained the disagreement he had with then Audio innovations owner Peter Quartrop of Audio Note fame re the finished design. Eric Anderson feared for product longevity because the adopted case design did not allow enough cooling. However house it properly, plenty of ventilation and it will reward with great sound and good reliability, as long as you don't use el34s in it.

Border Patrol had a page dedicated to info about A I designs and the Series 500

Hope the above helps, it's how I remember it but it was a long time ago.


Regards Neil

[Reffc]

You can buy any number of really reliable, decent sounding EL34 amplifiers. I'd say that the valve isn't any more or less reliable than most types. Look how many Mullard 520-type circuits using them are still around! Radfords are a classic example and they remain one of the most reliable valve amps made.

As for self bias, I wouldn't get too hung up on it (Cathode follower types usually). There are some fixed bias amps that have external bias pots and even their own bias meters. Biasing doesn't need to be done very often. Nothing wrong with a fixed bias circuit.

However, Audio innovations is a good shout, as is are Radford amps (STA15, STA25).

Also, YOU CANNOT (!!!) replace an EL34 with a 6L6 type unless the amplifier is specifically designed with this in mind. The two have completely different electrical characteristics (ie differing plate/grid voltages for a start). As a minimum, there are usually some output circuit resistor changes that are required for this modification.

[Spectral Morn]

You can buy any number of really reliable, decent sounding EL34 amplifiers. I'd say that the valve isn't any more or less reliable than most types. Look how many Mullard 520-type circuits using them are still around! Radfords are a classic example and they remain one of the most reliable valve amps made.

As for self bias, I wouldn't get too hung up on it (Cathode follower types usually). There are some fixed bias amps that have external bias pots and even their own bias meters. Biasing doesn't need to be done very often. Nothing wrong with a fixed bias circuit.

However, Audio innovations is a good shout, as is are Radford amps (STA15, STA25).

Also, YOU CANNOT (!!!) replace an EL34 with a 6L6 type unless the amplifier is specifically designed with this in mind. The two have completely different electrical characteristics (ie differing plate/grid voltages for a start). As a minimum, there are usually some output circuit resistor changes that are required for this modification.

Agreed re the 6L6 however in regards to the Series 500 I have never read or heard of this being needed but my own view is that I like 5881s in this particular amp.

http://www.borderpatrol.net/aiind.htm

Edit NB I stand corrected its 5881s that can be used without modification - memory lapse sorry.


Regards Neil

[Jason P]

Someone's got an A500 for sale on the 'Wam at the mo - dunno what one though...

[southall-1998]

Smashing guys! Thanks.

S.

[walpurgis]

I've heard several EL34 amps and they always seem to sound rather good.

[spendorman]

How about this:

www.ebay.co.uk/itm/Radford-STA-15-series-3-valve-tube-amp-amplifier-/161455440221

[spendorman]

Or a bit more money:

www.ebay.co.uk/itm/RADFORD-STA-25-MK-3-tube-power-amp-with-new-Mullards-tubes-/121476805413

That top cage has four screws along it's front edge, normally only two, strange.

[southall-1998]

Will study the Radfords a little later!

I've always liked that ''rounded'' rich sound from the EL-34.

The Triode Corporation TRV-35SE looks lovely. Does this amp have UK dealers too??

S.

[walpurgis]

Will study the Radfords a little later!

I've always liked that ''rounded'' rich sound from the EL-34.
The Triode Corporation TRV-35SE looks lovely. Does this amp have UK dealers too??

S.

That's not how I'd describe my EL34 monoblocks Shane. They're very clean, lucid and transparent, with good bass punch. Obviously, no harshness anywhere.

[southall-1998]

That's not how I'd describe my EL34 monoblocks Shane. They're very clean, lucid and transparent, with good bass punch. Obviously, no harshness anywhere.

Blimey, you still have them! Do they get much usage?

S.

[spendorman]

I'd describe the STA 25 III as dynamic. If that means anything.

[walpurgis]

Blimey, you still have them! Do they get much usage?
S.

Not recently, but I'm thinking about re-installing them.

[southall-1998]

I'd describe the STA 25 III as dynamic. If that means anything.

What is the power output?

S.

[jaym481]

5881 is a 6L6 type valve, also seen marked 6L6WGB. If the amp accepts 5881s you can sub the lower wattage 6L6 type (6L6G, 6L6GA, 6L6GB) valves in, but not the higher 6L6GC types (plus the Sovtek 5881 is a 30 watt valve, I think - so be careful).

[spendorman]

What is the power output?

S.

36 Watts RMS per channel

But sounds more powerful than that.

[southall-1998]

36 Watts RMS per channel

But sounds more powerful than that.

Well, never underestimate the valve watt :)

I've never really paid much attention to Radfords. Does the vintage STA 25 III have to be ''biased adjusted'' by the owner once in a while??

S.

[spendorman]

Well, never underestimate the valve watt :)

I've never really paid much attention to Radfords. Does the vintage STA 25 III have to be ''biased adjusted'' by the owner once in a while??

S.


The Quad 303 is 40 W per channel, and the STA25 seems more powerful, probably because of it's more graceful overload characteristic.

The bias is safely and easily set, without opening up the amp. Does not need doing very often.

[southall-1998]

I just really want an EL-34 that doesn't require biasing by hand...wishful thinking!!

Anyway if I give up, then perhaps the Sugden A21a series 2 will walk into my life.

S.

[walpurgis]

The Prima Luna Prologue Premium integrated EL34 valve amp has 'Adaptive AutoBias'.

[spendorman]

The STA25 is very easy, just plug cheap multimeter into socket and adjust pot so that meter reads 2.0V (I think). It's a while since I did this.

The STA15 is auto bias, nothing to do.

[spendorman]

I had the original Sugden A21 Class A, was OK, but a bit dull and boring.

[southall-1998]

The Prima Luna Prologue Premium integrated EL34 valve amp has 'Adaptive AutoBias'.

Nice one Geoff. Thanks!

S.

[walpurgis]

Spotted this on eBay. Looks interesting. Dunno about biasing though.

http://www.ebay.co.uk/itm/AA-Acoustics-EL34-Push-Pull-Integrated-amplifier-UK240v-Remote-Full-Warranty-/131331976214?pt=UK_AudioTVElectronics_HomeAudioHiF i_Amplifiers&hash=item1e93feec16

[spendorman]

Spotted this on eBay. Looks interesting. Dunno about biasing though.

http://www.ebay.co.uk/itm/AA-Acoustics-EL34-Push-Pull-Integrated-amplifier-UK240v-Remote-Full-Warranty-/131331976214?pt=UK_AudioTVElectronics_HomeAudioHiF i_Amplifiers&hash=item1e93feec16

Yes, interesting, something worries me though, single valve rectifier, not sure of it's spec, but can it supply enough current to drive two channels at 40 Watts? I have doubts.

[AlanB]

Best EL34 amp I've heard is the Mastersound. With 6550's even better.

[spendorman]

Best EL34 amp I've heard is the Mastersound. With 6550's even better.


I put KT77's in my Radford STA25 III

[spendorman]

Yes, interesting, something worries me though, single valve rectifier, not sure of it's spec, but can it supply enough current to drive two channels at 40 Watts? I have doubts.

The rectifier valve is a 5Z4P, which seems to be an equivalent of the GZ34, which the Radford STA15 uses. I suspect that Radford used solid stated rectification for the STA25 because the GZ34 could not supply enough current. Only a theory, I could be wrong.

[walpurgis]

The rectifier valve is a 5Z4P, which seems to be an equivalent of the GZ34, which the Radford STA15 uses. I suspect that Radford used solid stated rectification for the STA25 because the GZ34 could not supply enough current. Only a theory, I could be wrong.

This amp is supposedly based on the Dynaco ST70. What did that use?

[spendorman]

This amp is supposedly based on the Dynaco ST70. What did that use?

Just looked it up, same, 5AR4/GZ34. Does say that there is a solid state option though.

So perhaps it could get away with it, but I know that the STA15 can be quite hard on it's GZ34, so a more powerful amp with the same rectifier?

[spendorman]

Specs for the 5AR4 seem to be 0.125 A, 350V. Assuming these are maximum, Power = 0.125x350 = 43.75W.

So for an amp that claims 40+40 Watts output, something looks wrong.

Perhaps someone can check my figures.

[Canetoad]

I have a Dared i30 which takes EL34 or 6L6 valves. Documentation says it's optimised for 6L6. I'm running mine with a set of 6P3S-E Russian valves and it sounds pretty good.

Would it be worth trying some EL34 valves? :scratch:

[mik_rik]

Second the 6p3s-e, however they must be the "coin" based version ,much better than the other poorer construction type. Mick

[Canetoad]

How do you tell the difference Mick? :scratch:

[jaym481]

How do you tell the difference Mick? :scratch:

The one on the left is the "coin" type base. The 6P3S-E is, as far as I know, only coin-based, while the 6P3S (no "E") has the plastic cup-type base.
http://www.avx.hu/forum/uploads/monthly_03_2011/post-20826-019396900%201299837031.jpg

[mik_rik]

Sorry Canetoad for not getting back sooner, but as the saying goes about 1 picture being worth a thousand words! , with thanks to jaym481.

[Spectral Morn]

I have a Dared i30 which takes EL34 or 6L6 valves. Documentation says it's optimised for 6L6. I'm running mine with a set of 6P3S-E Russian valves and it sounds pretty good.

Would it be worth trying some EL34 valves? :scratch:

I would be very careful and stick with what is recommended.


Regards Neil

[Canetoad]

Sorry Canetoad for not getting back sooner, but as the saying goes about 1 picture being worth a thousand words! , with thanks to jaym481.

Not a problem Mick. :)

Mine are the same as the left version.

[southall-1998]

Anyway, thanks for responding guys.

S.

[Canetoad]

I would be very careful and stick with what is recommended.


Regards Neil

Thanks Neil. I've had the Russian valves in for at least a year without any problems. They definitely sound better than the Ruby 6L6 valves that were in it when I bought it. I bought it because I wanted to try a valve amp without having to spend too much. Glad I did as it sounds rather nice in my second system with Touch, AN Zero DAC and AR28 speakers. :)