Swapping valves

Could someone please tell me in words that an idiot could understand (ie Yes or No!!!) Can I just swap the EL34's in my Ming-Da M34A for KT-88's, or is there some witchcraft that needs to be done first. I know they have the same socket, but would the bias have to be changed?

 

Yes you can and yes the bias would need changing.

 

If your after some kt88's let me know I was going to get some from the states we could share the postage?

 

I could be interested, but, I now need to know how to change the biasing and what to? Or be pointed in the direction of a man or woman who can!!!

 

The joys of self biasing amps

 

Im getting some 6550's from srs, check ebay, I could ask for a combined cost if you let me know what your after. BTW the 6550's can be used instead of KT88's and the new tung sol's are getting very good reviews.

Lord, biasing on your amp is pretty straight forward, its a case of flipping it over, taking the bottom off, measuring across the big resistor on the valve base and adjusting by the trim pots. I dont mind coming down if you want me too. With KT88's your looking at a bias of around 50mV across that resistor. At present it'll be around 35mV with the El34's.

 

I'll have a think....The ones with a BIN of $109.88. That is interesting. Are they better than the KT88's. I would need my hand holding for sure when playing with electricity!

 

I aint holding your hand dude, leccy travels! These are the ones Im looking at:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=43375&item=7330239408&tc=photo

 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=43375&item=7329110414&tc=photo

A bias tool might be what you need?

 

Its straight forward enough on lordsummits, its only one measurement across a resistor, they do look handy though.

 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=43375&item=7325702924&tc=photo

These look like what I have in mine? They're quad branded, there is a quad of quad branded valves on e-bay at the moment but they aren't svets like mine. I don't need matched valves according to quad would that make a cost difference or would I be as well getting a matched quad?

 

I think its slightly cheaper to get quads actually. Id def buy matched in any instance. Your best trying something different to see what you think, even if your prefer the originals at least you have another set which is quite important really.

 

Svets are nice kt's, I'd keep them till they die. Different brands of the same type power tubes aren't always where its at when it comes to changing the sound, often a very subtle change, the small signal drivers are often the ones to fiddle with if you haven't already.

 

Too right. I was blown away when I changed my single 12AX7 in my power amp.

JJ

 

Me too. I was staggered at the difference between 5687 and 6922 variants in my Audions. Much greater than changing the 300Bs

 

Wasn't aware there wre any other 6SH7 brands than RCA?, and do rectifiers make any difference (5U4G)

 

I dont know about rectifiers. I also found changing my 6u8's made a massive difference, Ive numerous sets but nothing touches the nos Mullards I found.

 

Rectifiers can make a big difference- think about what they're doing, taking the AC input and changing it to DC. Smoother DC is better, so better quality rectification means a better sound.
What do you have in at the moment? From a quick look at google it seems theres a lot of Sovteks around atm, might be worth a try.

 

don't know what rectifier you use at the moment, but the mullard gz34 / 5ar4 is fabulous. makes a huge difference over russian / chinese tubes.

 

Ive never had any experience of valve rectification but I do like the idea of it being done in some nice big friendly tubes as opposed to tiny diodes, dont know why, just do.

Would you say that valve rectification is superior to something like schottky diodes??