[CPL593H]

Quote:

Originally Posted by oohms /img/forum/go_quote.gif The volume control essentially forms an L pad at the input, so by adding a resistor there would preserve the sound characteristics of the amp better.. but the setup would be more prone to noise, than if you attenuate at the output.

that could work too. I wouldn't hurt to try, especially if the results no the output don't sound good. That is done in audio for example when a line level signal needs to be reduced to microphone level - and a 20 or 40 db pad might be used on the input. But like you say you are taking a low level signal and making it even lower which can really impact the signal to noise level in the system.

 

[Joe Presto]

Quote:

Originally Posted by oohms /img/forum/go_quote.gif The volume control essentially forms an L pad at the input, so by adding a resistor there would preserve the sound characteristics of the amp better.. but the setup would be more prone to noise, than if you attenuate at the output.

I have the parts I need for an L-pad, depending on the results I'll look into your suggestion.

 

[brendon]

Hi, I have the opportunity to choose between the following tubes. Please suggest which of them are good -

Mullard Made in Great Britain tube Factory Code starts from 'B',*
manufactured in Mullard Blackburn factory**Rs.1500 each (only 3 in stock)

Philips made in Holland tubes, Factory code starting with a right-angled triangle*
made in Philips Heerlen plant Rs. 1250 each

BEL GOLD PIN E88CC special quality ECC88(new in box) * * * * Rs. 850 each

BEL ECC88 (new in box) * * * * * * * * * * * * * * * * * * * * * * * * * * *Rs. 500 each

Philips Miniwatt ECC88 * * * * * * * * * * * * * * * * * * * * * * * * * * * *Rs.750 each

 

[CPL593H]

Quote:

Originally Posted by brendon /img/forum/go_quote.gif Hi, I have the opportunity to choose between the following tubes. Please suggest which of them are good - Mullard Made in Great Britain tube Factory Code starts from 'B',* manufactured in Mullard Blackburn factory**Rs.1500 each (only 3 in stock) Philips made in Holland tubes, Factory code starting with a right-angled triangle* made in Philips Heerlen plant Rs. 1250 each BEL GOLD PIN E88CC special quality ECC88(new in box) * * * * Rs. 850 each BEL ECC88 (new in box) * * * * * * * * * * * * * * * * * * * * * * * * * * *Rs. 500 each Philips Miniwatt ECC88 * * * * * * * * * * * * * * * * * * * * * * * * * * * *Rs.750 each

I don't know what BEL is. The Phillips Miniwatt ECC88 is probably a Heerlen Holland tube also so it looks like the best deal. I have Phillips and Mullards and they sound the same to me. Both are great.

 

[Judge Buff]

Quote:

Originally Posted by brendon /img/forum/go_quote.gif Hi, I have the opportunity to choose between the following tubes. Please suggest which of them are good - Mullard Made in Great Britain tube Factory Code starts from 'B',* manufactured in Mullard Blackburn factory**Rs.1500 each (only 3 in stock) Philips made in Holland tubes, Factory code starting with a right-angled triangle* made in Philips Heerlen plant Rs. 1250 each BEL GOLD PIN E88CC special quality ECC88(new in box) * * * * Rs. 850 each BEL ECC88 (new in box) * * * * * * * * * * * * * * * * * * * * * * * * * * *Rs. 500 each Philips Miniwatt ECC88 * * * * * * * * * * * * * * * * * * * * * * * * * * * *Rs.750 each

I'd have to take a chance on the Miniwatt for half the price of a Mully (If you can get any tube data that is... My guess is that it is only emitting at 60% or so or has some real mismatched triodes.). If the data appears mismatched, don't waste your money.

And not to contradict my friend CPL593H, but I find Mullys to be typically warmer and more "liquid" than Heerlen Philipses (Amperex's parent company). I find the Holland tubes to be cleaner and more precise than Mullys. If the Mully is an A Frame, though, it will sound a lot like a Philips or Amperex A Frame. Both companies have awesome tube families and typically sound amazing, but as with any tubes, you want the triodes to be close to each in emissions - within 5% hopefully.

EDIT: If Rs stands for Indian rupees, the Miniwatt is about $17 USD a real decent price for a good tube. If the tube is good, snap it up!! That makes that Mully about $35 USD, which I consider pretty expensive and the Heerlen Philips about $27 USD, still pricey but a better deal than the Mully. My advice is to haggle, if possible. I'd try to reduce the price by at least 250 for each.

 

[brendon]

Yes INR stands for Indian rupees. Sorry for forgetting to mention that.

Thanks Judge Buff and CPL593H for your helpful comments.

I will order the Miniwatt as per your suggestions and ill try the Philips Holland tube as it should be a nice neutral tube.

The pricing may seem high to you guys but this shop is probably the ONLY shop that sells tubes in the whole of India ! So its much cheaper than if I import the tubes.

 

[enemigo]

I've tried two different tubes on my Bravo amp and can't get them to work properly. The stock 6N11 tube works just fine but having gotten a glimpse of what other tubes can do, I want to replace it.

The first tube I bought was the Brimar CV2492 (~$15). It sounded far better, but there was a lot of background noise created by the amp (the pot did not affect the noise level). ALso the amp got extremely microphonic, picking up movement on my desk, like putting down my coffe cup. I realised the tube wasn't properly positioned in it's socket, so I pushed a fraction of an inch on one side. After that microphonics was gone, as was the left channel!. Pushing the tube sideways resulted in loud crackeling noises, mostly in the left channel, and microphonics returned. When I found a decent position for the tube I soon found the bass was wrong. It sounded like the amp wasn't getting enough current, the bass was breaking up badly even on low listening leves. So I assumed the tube was busted.

Today I got the RF-shielded GE 6DJ8 (~$27). Installed it, turned on the amp for a few minutes and tried it. No sound on the left channel, moving it about gave the same result as with the Brimar tube. Also, the GE tube heated up the heat sinks far more than the other tubes. So this one isn't working either.

I put back the stock 6N11 tube and the amp is working fine again.

Why? Is anything wrong with the amp? If I'm having bad luck with my tubes, could someone recommend a tube that definitely will work? Must be under $31 excl shipping and preferably RF-shileded.

Thanks
Knut

 

[jcoops16]

Quote:

Originally Posted by enemigo /img/forum/go_quote.gif I've tried two different tubes on my Bravo amp and can't get them to work properly. The stock 6N11 tube works just fine but having gotten a glimpse of what other tubes can do, I want to replace it. The first tube I bought was the Brimar CV2492 (~$15). It sounded far better, but there was a lot of background noise created by the amp (the pot did not affect the noise level). ALso the amp got extremely microphonic, picking up movement on my desk, like putting down my coffe cup. I realised the tube wasn't properly positioned in it's socket, so I pushed a fraction of an inch on one side. After that microphonics was gone, as was the left channel!. Pushing the tube sideways resulted in loud crackeling noises, mostly in the left channel, and microphonics returned. When I found a decent position for the tube I soon found the bass was wrong. It sounded like the amp wasn't getting enough current, the bass was breaking up badly even on low listening leves. So I assumed the tube was busted. Today I got the RF-shielded GE 6DJ8 (~$27). Installed it, turned on the amp for a few minutes and tried it. No sound on the left channel, moving it about gave the same result as with the Brimar tube. Also, the GE tube heated up the heat sinks far more than the other tubes. So this one isn't working either. I put back the stock 6N11 tube and the amp is working fine again. Why? Is anything wrong with the amp? If I'm having bad luck with my tubes, could someone recommend a tube that definitely will work? Must be under $33 excl shipping and preferably RF-shileded. Thanks Knut

I had no problems with that brimar and thought it sounded better than the 6n11. I think the tube socket isnt great at all, mine is very stiff and wobbles too much for my liking when I change tubes.

Try the 6n11 again to see if that will fix things, if it does you now its the tubes, if not, perhaps the tube socket is damaged.

 

[leeperry]

.

 

[enemigo]

Quote:

Originally Posted by jcoops16 /img/forum/go_quote.gif I had no problems with that brimar and thought it sounded better than the 6n11. I think the tube socket isnt great at all, mine is very stiff and wobbles too much for my liking when I change tubes. Try the 6n11 again to see if that will fix things, if it does you now its the tubes, if not, perhaps the tube socket is damaged.

The 6n11 still works (as mentioned ¨,). I'm hesitant to buying more tubes now since the two I've tried are having similar faults. It could be the socket's fault, I'll disassemble the amp and check the soldering joints.

K

 

[brendon]

^^ Strange. I have a total of 3 tubes and all three work fine. Its possible that its the tube that is at fault.

 

[CPL593H]

Quote:

Originally Posted by enemigo /img/forum/go_quote.gif The 6n11 still works (as mentioned ¨,). I'm hesitant to buying more tubes now since the two I've tried are having similar faults. It could be the socket's fault, I'll disassemble the amp and check the soldering joints. K

sounds like a bad tube socket.

 

[Judge Buff]

^X2
On my Indeed, I had some of the initial crackling that you speak of and I ended up getting rid of the 6n11. I did some of the tube "jockeying" that you describe like leaning, reseating, etc. I did apply some pressure around the socket itself to see if it had shifted due to the board flexing in transit and it seemed to move slightly on the left facing the volume knob.

I have had no crackling problems since, but I've never returned the stock tube to the amp. It's worth a try to apply some moderate pressure around the socket, but you must have the pcb supported under the area you are pressuring. I put it flat on a table to do it. If it doesn't work, contact the Bravo folks and ask for assistance/return.

Oh yeah, out of 25+ tubes I've rolled into my Indeed, I've only had two that were nonworking. All of my tubes have come from eBay, inc eBay.uk and eBay.de, too.

 

[FraGGleR]

Does anyone have a model number/source (preferably Mouser since I have some other stuff I need from there) for a drop in replacement for the push button power toggle for the Bravo? Mine doesn't catch consistently anymore. Not a huge issue, but I'd like to have it in perfect working order should I try to sell it. Thanks!

 

[acvtre]

The bravo v2 is just arrived and I want tweak it as much as I can. First of all I'd like to try some valves and change some capacitors. What would you suggest to buy?
Sencodly I would change the pot with a better one and with more ohms, such as the 50kohm blu alps. Is it a good idea?