• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Looking for a tube amp

Hello there!

I'm looking for a tube amp for my Mar-Kel70 speakers. I wont use more than 20w since that's the upper limit for the little CSS EL70.

I'm willing to pay $550 but in that case it has to be something really good and with a protective grille for the tubes (in case the cat or my little cousin want to take a closer look).

The idea is quite difficult to explain i think...

I will connect my Harman Kardon HK3490 to my computer with optical cable. And then Pre-Out from the HK to a Reckhorn S-1 to let the HK get the bass freq (from S-1 to Main In) and power the subs. And then the tube is connected to the S-1 aswell to take care of the 80-20000hz signal and power the Mar-Kel70.

What amplifier am i looking for?

Best regards
Niklas
 

nightanole

Member
2009-02-28 1:24 pm
Well this is the diy site. A dynaco st-70 rebuild would be right dead center for your budget and power requirements with some el34's.

If not a pentode PP el84 setup would get you 15-18 watts. There is plenty of PP el84 stereo units on ebay. Worse case is a rewire based on the amp topology you choose (baby huey,red light district, oddwatt) and maybe replace the output transformers with some edcor's.
 
Yes i know this is a DIY forum but the knowledge here is unbeatable, afaik :D
My electronicsknowledge is basically none and i'd prefer to purchase a finished amplifier, just to hook up and play (and maybe place the tubes in their socekts, looks quite easy).

But will 12w be able to play loud enough?
 

taj

diyAudio Member
2005-02-23 8:49 pm
Hmm... I think your only hope here for a finished amp might be if someone wants to sell one of their homebrew amps to you.

A complete ST-70 from Triode Electronics runs close to $1k. You could try one of the many Chinese tube amps on eBay (at your own risk), or grab an old stereo amp from eBay, again at your own risk since it probably would need at least some DIY refurbishing.
 

tinitus

diyAudio Moderator R.I.P.
2005-11-24 1:47 am
its harder in EU, with customs, shipping, etc

I dont know much about this company, but this EL34 PP looks solid

but be careful, there may be additional VAT etc
with other goods(not hifi) I have experienced things like shipping from east, and still charged with additional custom and shipping costs
expences I wasnt aware of because I believed to buy from UK

MingxingMingda MC34-A06 STEREO INTEGRATED AMP.
 
but this EL34 PP looks solid

I've had one of those in house -- it is IMO one of their best push-pulls, Joe Rasmussun uses it as the basis of an extensive mod.

JLTi EL34 & KT88 Amps

(i don't know if Joe snips out the unnecessary stage in the KT88 amp -- stock i much prefer the EL34)

It must thou be considered as a prebuilt kit... there is a lot that can be done to improve things -- damp the transformer covers, change the 5-way posts, wire past unnecessary plug in connectors and circuit boards. For instance there is a seperate board who's purpose is to have a volume pot & a connector mounted to it, and a jumper from that connector to a connector on the driver board. Loose the circuit board and solder wires directly from the pot to the driver board -- quite a few of those kinds of things -- not actually changing the circuit, just streamlining the build.

Attached is a pic with the top* off.. ignore the perf board, we were using the amp to prototype something for a client.

*(watch out, the edges of the top are sharp... just ask the bandaids i had to use :))

dave
 

Attachments

  • yaqin-EL34.jpg
    yaqin-EL34.jpg
    98.9 KB · Views: 448

dovla

Member
2010-03-15 7:32 am
Chinese amps in EU

There are several importers of Chinese amps. Yaqin and Yarland are relatively decent.
Take a look at AAAVT.IT - Amplificatori a Valvole Termoioniche (no affiliation) - prices already include EU VAT and items are already in Italy. Compared to buying on ebay and paying for shipping + duties + VAT they cost just a bit more (and you get EU warranty, you also get better tubes than the stock Chinese).
Check via email with the owner for specific model(s) pricing as web site is not always up-to-date.
 
I've had one of those in house -- it is IMO one of their best push-pulls, Joe Rasmussun uses it as the basis of an extensive mod.

JLTi EL34 & KT88 Amps

(i don't know if Joe snips out the unnecessary stage in the KT88 amp -- stock i much prefer the EL34)

It must thou be considered as a prebuilt kit... there is a lot that can be done to improve things -- damp the transformer covers, change the 5-way posts, wire past unnecessary plug in connectors and circuit boards. For instance there is a seperate board who's purpose is to have a volume pot & a connector mounted to it, and a jumper from that connector to a connector on the driver board. Loose the circuit board and solder wires directly from the pot to the driver board -- quite a few of those kinds of things -- not actually changing the circuit, just streamlining the build.

Attached is a pic with the top* off.. ignore the perf board, we were using the amp to prototype something for a client.

*(watch out, the edges of the top are sharp... just ask the bandaids i had to use :))

dave


Those amplifiers you linked to are way above my budget :(

But i'm not sure really if i need an integrated amplifier or only power amplifier...
And since some guy on another forum said my HK wouldn't power the subs (see my thread about the subs) i'm starting to get a little worried...

And as i said before i'm looking to build and amplifier, or modify it at all at the moment. I haven't even soldered before!
So, the most difficult i can think of doing is place the tubes in their sockets.
 

tinitus

diyAudio Moderator R.I.P.
2005-11-24 1:47 am
I dont understand your setup

might help if you could show a block scheme

suggestions might then be different

before you rush into buying something you dont really understand, maybe your setup and goals should be debated first

with tube amps I think its best to keep the whole setup simple

if your goal is more complicated with multiple units, then maybe a tube amp isnt really your best choise

so please, define your goal
 
Those amplifiers you linked to are way above my budget :(

I wasn't suggesting them, just pointing out that Joe thinks enuff of the Yaqin EL34 amp you were considering to use it as a basis for his amplifier. In other words if you start with a stock amp it can be evoleved into something much better.

dave
 

ChrisA

Member
2008-01-08 12:22 am
[IMGDEAD]http://sv.tinypic.com/view.php?pic=nychi0&s=7[/IMGDEAD]

In swedish though...
Dator = Computer
Rörförstärkare eller rörslutsteg = Tube amplifier or tube power amplifier

That's how i think i am supposed to do. But i'm not sure if it works at all.

I can't see the diagram but from description I think I see what yuo want to do. I'd call it a bi-amp setup usinf a computer source. I think you might find it you buy a ST-70 amp that you don't need the bass amp. the ST-70 will do fine just be itself

As it turns out the most expensive part of a tube based amp is the transformers. They cost quite a bit more than the tubes do. Maybe 5X more. So there is something to be gained using a tube amp in a bi-amp system if you design the tube amp for that purpose. It turns out the weakness of lower cost transformers shows up in poor bass. So if the amp does not need to reproduce bass you can save a good deal of money if it only has to go down to(say 100Hz) Tube guitar amps are this way -- with standard "E" tuning the lowest note a guitar can make is 81Hz so transformers for guitar amps tend to be smaller and cheap than for HiFi which goes to 20 Hz. Much of the cost of the HiFi amp is in the lowest 60 Hz. All that said, my point is that using a ST-70 for a treble only amp is a waste of funds