[telecaster]

Quote:

 
These look gorgeous! Maybe I should get me a pair (34€ matched). How do they glow?
I never saw or found a pair of 7236 for sale, nice find Sluker!

Ultra those tubes are the bomb! those price are also tremendous!

 

[telecaster]

Finally thanks for the feedback! I've been scratching my head for some long hours trying to understand that electronic bit in english!
First I must say that I too found that the bass region is weak compared to my loudspeaker system that is why I want to improve things. Also, most of the music sound just good with a bass response down to 40Hz... But... I want better lower frequency response, and I know HD650 with an adequate EQ can go much lower...
 
There is very little info about output coupling with OTL in case of our La figaro, you are the first person I hear talking about it and Fitz on headfi. I was really wondering what value would be adequate for my setup (HD650-339) and I thought 200µF would be more than enough considering stock 339 is 130µF and even much less for stock 337! But I found this calculator : http://www.v-cap.com/coupling-capacitor-calculator.php (sorry I didn't mean to advertise for that brand)
 
Seeing the steep fall off I have seen on graphs with caps high pass, to have a -+0dB point at precisely 20Hz, the -3dB point must be at 2Hz!!! That represent a output cap of 265µF per channel!!! I have made my math and I can fit just so so four MKP 120µF 250V (brand SCR) into the black cubic cover...
I haven't pull the cover off to be sure but I estimated the inside width to 105mm. Those 120µF caps are 52mm in diameter so it fit barely and I would just be able to insert a leaf of paper against the cover... I don't like having so less play.
 
Now I need to know if going 250V cap rating (the stock are lytics 350V) isn't dangerous!
 
Also the price isn't friendly at all, but I want to pay for 20Hz response... And I understand the reasonning in putting less µF, less material is more transparent sound. I just hope that going MKP will make up for it. But hearing from your experience with those lytics and very high quality bypass silver in oil, you don't have transparency trade off?! If I read you well you put 150µF in each channel, or 300µF per channel (that's a bit too much right!?)
 
Quote:

 
Always it’s possible to improve things,  Lf339 was designed to provide a good performance/cost ratio. But the sound can always be improved on.

I modded my previous La figaro amp 332c by simply replacing output coupling caps. The 332c was designed to work with high impedance cans in my case with hd650, it is good sonding amp but weak in bass region. Rolling tubes do not resolve issue with the bass, it does but just slightly.The chassis  was to small to put in proprer value (uF) film caps, the stock output coupling caps is 40uF but there was left room to put another caps wchich I did, doubled the capacity to 80uF had a little effect so removed the stock caps and go with 2x150uF Mundorf M-Lytic HV - electrolte  bypased with 1uF M-CAP Supreme Silver & Oil. This time the improvement was huge in all regions the highs, mids and the bass went strong, dynamic and deep like newer before.

The output capacitors will have some impact on the final sound. Solen, MKP, Vishay or Mundorf MKP are good choice and you don't have to bypass them.
The stock value(capacity) is 130uF increase the capacity for example 220uF  will allow extend bass response into 32 ohm headphones.If higher impedance headphones are used you can stick with smaller value of output capacitors.

You have to be careful it is a tube amplifier and there are dangerous voltages present! it will need some understanding of electronics ability to solder and use simple test equipment such as a multimeter.Remember that even when switched off there is still a high voltage. To discharge the high voltage stored in capacitors in power section you can use a 25 watt bulb with connected leads, short the circuit betwin +&- will seftly discharge the caps.
 

 

[WALL-E]

In many DIY diagrams of OTL amps the value output cap chosen by designer was from tens of uF till few thousand! in result to get ultra low frequency response into 32 ohm.There is always compromise between which cap to use, go with smaller value but better film caps or used electrolitic which are larger capacity but worse parametrs. So bypass the electolitic or even "no name film caps" cap is good way to improve high frequency response of the electrolite cap because the lower value film cap will pass higher frequencies much better. There are several scholls of byppas capacitors.
1.The value of the film cap should be 10% of the electrolytic.
2.The value of the film cap should be between 100nf and 1uF
3. or "double bypas"its mean bypass electrolite with larger value film and then the film cap bypass with very low vallue mica or polypropylen cap like wima mkp10.
 
You shouldn't be so critical about the value of the output cap you chosen, if there is enough room to put two 120uf in parallel x 2 so stick with them.
250V it is safely minimum I didn't measure the voltage on cathode resistor but i think is about 150V so capacitors on 250V seems ok. I think you good choise and the extra uF will be needed when you switch to lower impedance cans in future.
 
2x150uF Mundorf MLytic HV is good cap even not bypassed sounded well in my lf332c, adding the 1uF M-CAP oil cap improved highs and clarity it was much better then the EC stock 5$ caps. I used half of this cap 150uF but bridged to 300uF but the diference was very subtle.
 
Quote:

Finally thanks for the feedback! I've been scratching my head for some long hours trying to understand that electronic bit in english!
First I must say that I too found that the bass region is weak compared to my loudspeaker system that is why I want to improve things. Also, most of the music sound just good with a bass response down to 40Hz... But... I want better lower frequency response, and I know HD650 with an adequate EQ can go much lower...
 
There is very little info about output coupling with OTL in case of our La figaro, you are the first person I hear talking about it and Fitz on headfi. I was really wondering what value would be adequate for my setup (HD650-339) and I thought 200µF would be more than enough considering stock 339 is 130µF and even much less for stock 337! But I found this calculator : http://www.v-cap.com/coupling-capacitor-calculator.php (sorry I didn't mean to advertise for that brand)
 
Seeing the steep fall off I have seen on graphs with caps high pass, to have a -+0dB point at precisely 20Hz, the -3dB point must be at 2Hz!!! That represent a output cap of 265µF per channel!!! I have made my math and I can fit just so so four MKP 120µF 250V (brand SCR) into the black cubic cover...
I haven't pull the cover off to be sure but I estimated the inside width to 105mm. Those 120µF caps are 52mm in diameter so it fit barely and I would just be able to insert a leaf of paper against the cover... I don't like having so less play.
 
Now I need to know if going 250V cap rating (the stock are lytics 350V) isn't dangerous!
 
Also the price isn't friendly at all, but I want to pay for 20Hz response... And I understand the reasonning in putting less µF, less material is more transparent sound. I just hope that going MKP will make up for it. But hearing from your experience with those lytics and very high quality bypass silver in oil, you don't have transparency trade off?! If I read you well you put 150µF in each channel, or 300µF per channel (that's a bit too much right!?)
 

 

[xmdkq]

 
Capacitor 90UF data measured with RMAA

 

[telecaster]

I know all those mods are a little too much, but hey I'd really like to pimp that amp and make it sing to its full potential! Plus having all SCR caps will make it looks like those vintage Conrad Johnson amp! (lots of folks don't like SCR, and some swear by them)...
 
I cannot locate a good seller for caddock resistors, I will then stick with Seta brand... 

 

[telecaster]

Capacitor 90UF data measured with RMAA

 I understand the 339 in it's actual state is perfect, but I want to go all out and try to achieve a perfect 20Hz capability.

 

[xmdkq]

Capacitor 150UF data measured with RMAA

 

 

[T.F.O.A]

How well does this amp drive the lcd-2? So-so, decent, good, or great? Tubes rolling please write it down too, i'm thinking of getting one

 

[Ultrainferno]

Quote:

How well does this amp drive the lcd-2? So-so, decent, good, or great? Tubes rolling please write it down too, i'm thinking of getting one

 
I'm really not going over the tube rolling again, everything has been said in this thread already. Just read it and learn something
LCD-2 needs 5998/2399/7236 power tubes or it won't be that good

 

[telecaster]

Ultra :  how does it goes with your Crack and GEC 6AS7G, did burn in improved things?
 

 

[Ultrainferno]

Ultra :  how does it goes with your Crack and GEC 6AS7G, did burn in improved things?

 

I haven't tried it really. I am redoing the wood now, using the V200 mostly with the HE-400 atm. Crack is just a sideproject

 

[telecaster]

I didn't follow mate, but you got yourself a pair of HE400? I was thinking about the HE500 but I need to take care of my 339 project right now, it's occupying all my funds!

 

[Ultrainferno]

Quote:

I didn't follow mate, but you got yourself a pair of HE400? I was thinking about the HE500 but I need to take care of my 339 project right now, it's occupying all my funds!

 
I think I was one of the first to get the HE-400. I have a couple of headphones yes They're in my profile if you're interested.

 

[T.F.O.A]

Quote:

 
I'm really not going over the tube rolling again, everything has been said in this thread already. Just read it and learn something
LCD-2 needs 5998/2399/7236 power tubes or it won't be that good

Ok, thanks, I'll bug Keph about it
But with those tubes, will it be good, or more than enough good?
 
thanks guys.

 

[Ultrainferno]

The 339 is awesome with a lot of tubes and headphones. Those tubes mentionned above just give it the power it needs for orthos