Valves.

Polar Bear · Post by **Polar Bear** » Wed Jun 30, 2004 12:03 pm

I'm in the market for some new valves, money isn't a huge object at the moment becasue I can get most of the brands rather cheap overseas. I'm after both KT88s and 7027a's.

Does anybody have an opinion on which brands are top notch and good value for money.

I'm steering clear of Sovteks because my amp tech in HAmilton said that both the 7027s and the KT88 are awful. I've been looking at Tesla/JJ, Electro HArmonix, Svetlana and SED-Winged C(i've never heard of these) for the KT88s and probably JJ/Tesla for the 7027a's.

Does anybody have any experience with these valves, as I'm buying from overseas, I don't really want to fack up and end up with duds.

philipnz · Post by **philipnz** » Wed Jun 30, 2004 12:05 pm

No, but when you find out let me know too. I want a set of backups for my Matchless

Polar Bear · Post by **Polar Bear** » Wed Jun 30, 2004 12:09 pm

I should also have asked, how much does a re-bias generally cost?

ash · Post by **ash** » Wed Jun 30, 2004 2:11 pm

Re-bias should cost between $30 and $50. Whatever their minimum charge is. Go to a specialist valve guitar amp tech, because not every tech has a clue about valve guitar amps. Stephen Delft in Welly is probably the one to find.

I don't recommend bringing valves in from overseas unless you're prepared to accept a few broken or damaged ones for the lower price.

Tesla are very good. EH are supposed to be good too. Svetlana may be the source of Sovtek valves, but I'm not sure. Groove tubes are the most reliably consistent brand.

BTW, 7025 (Edit, I had said 7027a which was wrong) are basically the same as ECC83 and 12AX7. Its the military designation for that design. Unless you have a specific desire for a 7025 (Edit, not 7027a), you can fit 12AX7s without noticing much difference. (Edit, of course this means nothing considering PB wanted 7027s!)

Another interesting point... most amp makers recommend matched pairs of output valves, but Peavey's top valve amp dude (5150 designer) says its a load of crap. The valves get matched at 1 Watt loading, but we use them at 30-50W in practice. so the matching wouldn't apply anyway...

Bluesbird · Post by **Bluesbird** » Wed Jun 30, 2004 2:13 pm

SED were formerly known as Svetlana.

Are you looking for new or NOS?

I don't know too much about those tubes in particular, but JJ seem to have a good reputation among the new tubes, although you'd have to check for each valve type.

Groove Tubes aren't as bad as many people make out - they source their valves from many of the brands you mention, test them a little and grade them, so you're less likely to end up with a dud. They've also recently bought the old General Electric factory and equipment, and have been producing tubes in the USA, although neither of the valves you are after, at this stage. The 12AX7M and 6L6GE's are supposed to be pretty good though, probably the best of hte new production valves.

If you're going NOS, some of the better brands include Mullard, GE, JAN Philips, RCA, Amperex, and Telefunken.

Can't help you with the cost of biasing, sorry - my amp is cathode biased.

B45-12 · Post by **B45-12** » Wed Jun 30, 2004 4:59 pm

Has the price of NOS KT88's come down? recall reading a few years back about AC/DC retubing their amps with them and the only good ones they could find were from Japan at about $1000 US for four.

As a valve radio enthusiast from way back I admit to being horrified by the prices of the valves the amps use - used to think $6-00 was a lot!! for a new boxed valve at that.

RCA used to be the American major supplier and Phillips the UK one in the 60's/70's.

'Biasing' for those mystified by the term is basically checking the dc voltages on the valve pins are correct and according to the amp manufacturers specs. A good techie can sometimes tweak these a little to get slightly better performance. You do this by varying the preset resistors inside the amp until the dc volts you measure with a meter is according to specs on the valve's grids, anode and cathodes - not quite a simple as it sounds as the volts all tend to be interelated in amps and like guitar tuning you adjust one, then may have to come back to it.

In the class B amps (push pull) there is another sort of biasing basically to make sure you get a decent output signal but in the boutique guitar amps the output is usually class A (single valve) or class AB (umpteen single valves acting effecticely in paralell as one huge valve) so this 'compensation type' biasing does not apply.

So basically the tech has to measure the voltages and tweak the associated pot resistors until they are right according to a chart/his knowledge. In theory an hour should be ample, but given the vagaries of some manufacturers up to one and a half hours is reasonable for a really good job.

Polar Bear · Post by **Polar Bear** » Wed Jun 30, 2004 10:17 pm

[quote="ash"
BTW, 7027a are basically the same as ECC83 and 12AX7. Its the military designation for that design. Unless you have a specific desire for a 7027a, you can fit 12AX7s without noticing much difference.

Another interesting point... most amp makers recommend matched pairs of output valves, but Peavey's top valve amp dude (5150 designer) says its a load of crap. The valves get matched at 1 Watt loading, but we use them at 30-50W in practice. so the matching wouldn't apply anyway...[/quote]

7027a's are big 6l6s. Two of them together put out 75 watts. And at a quater of the price of NEw zealand prices I'm willing to take the chance on a broken one.

Do you know where this Stephen Delft works from?

Cheers

ash · Post by **ash** » Thu Jul 01, 2004 7:50 am

Oh, sorry! I should have checked before I spat...

I mean't 7025 when I ranted about them being the same as 12AX7, which of course is not what you were talking about at all...

7027a is indeed the big ass pentode like a 6550...

ash · Post by **ash** » Thu Jul 01, 2004 10:54 am

I could find the ones you wanted, but Valve Radio Spares in Christcurch have them listed: KT88 - Gold Dragon $73 and 7027a Sylvania USA $65. These are old prices though, so ring and enquire.

VRS - Christchurch
Bill Bryant
(03) 342 9565

Look in old NZ Musician mags (or their website, he used to write for them) to find where Stephen Delft is hiding...

Polar Bear · Post by **Polar Bear** » Thu Jul 01, 2004 1:34 pm

ash wrote:I could find the ones you wanted, but Valve Radio Spares in Christcurch have them listed: KT88 - Gold Dragon $73 and 7027a Sylvania USA $65. These are old prices though, so ring and enquire.

VRS - Christchurch
Bill Bryant
(03) 342 9565

Look in old NZ Musician mags (or their website, he used to write for them) to find where Stephen Delft is hiding...

I'm assuming that's for a single (?)
I'm looking at basically being able to pay that sort of price for a matched set if I order them in myself, which is why I'm willing to take the chance on a slightly duff one.

Polar Bear · Post by **Polar Bear** » Thu Jul 01, 2004 1:36 pm

ash wrote:I could find the ones you wanted, but Valve Radio Spares in Christcurch have them listed: KT88 - Gold Dragon $73 and 7027a Sylvania USA $65. These are old prices though, so ring and enquire.

VRS - Christchurch
Bill Bryant
(03) 342 9565

Look in old NZ Musician mags (or their website, he used to write for them) to find where Stephen Delft is hiding...

Thank you for the info on Stephen Delft btw, I just realised that I own one of his products and very good it is too! I knew I recognised his name.

goldtop0 · Post by **goldtop0** » Thu Jul 01, 2004 6:27 pm

EH = rebranded Sovtek or Sovtek at a higher price.
Groove Tubes = everything at a higher price.
Svetlana = another Russian tube but not as consistently good as Sovtek.
Tesla = good consistent tubes
JJ = just another branded tube
NOS = now real high prices for any old JAN Philips or Mullards or GE etc.
Sylvania = good tubes
Don't buy Chinese power tubes 7027a or KT88 but if VSR ChCh have these cheap (as you say) I'd get em as these are hellishly costly(Sylvania)overseas.
Simcha Delft formerly known as Stephen is your best bet and he should be in the phone book,he is very exacting and precise.
I use Sovtek, EH, Sino(pre amp only) and old JAN Philips when I can get em at the right price, and EI(Yugoslavia). These are all reasonably priced and do the job in 6L6,EL34 and all pre amp.
Don't get sucked in to paying big money for valves eg Groove Tubes or high cost NOS, buy original manufacturers product such as Sovtek or Svetlana and you won't go wrong.Fender,Marshall and all the other guys use em.

goldtop0 · Post by **goldtop0** » Thu Jul 08, 2004 9:07 am

Made a mistake there Tesla/JJ is a new name for the Tesla company which produces excellent tubes,original manufacture.

Post by **GrantB** » Thu Jul 08, 2004 9:17 am

I can absolutely recommend Tesla/JJ tubes. Reloaded all pre-amp sections of my main amps with these and agree - consistently good sounding. I have not had many issues with Sovtek's, especially the WXT higher gain versions. Seem to do me fine for standard applications. Simcha is indeed the man - he does a greeat transformer for AC30's too. I got my Tesla/JJ tubes from Jansen on Khyber Pass Rd, Akl.

stuu · Post by **stuu** » Thu Jul 08, 2004 11:15 am

i got my MESA power section totally retubed and biased with 4 svetlana EL34's for $200 from an amp tech in Mt Eden (auckland). His name is Clarry and his number is 6307011.

he has an awesome reputation and works for next to nothing.

he also stocks his own tubes (all well known brands, and some un-knowns from what i've seen), and sells them for rediculously cheaper than the rockshop. and re-biases your amp (if needed) when putting the tubes in for less than anyone i know.