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2359glenn | studio - Page 338

post #5056 of 10643
Quote:
Originally Posted by dminches View Post

Glenn/Tyrell, what transformers were put into that beautiful amp?

Lundahl LL1664s if I'm not mistaken.  Glenn thinks I'm crazy spending so much money on high dollar parts, but these are actually very reasonably priced compared to the crazy Tango and Tamura transformers from Japan.  I think Lundahl hits a good sweet spot in terms of price/performance, though that is not really based on anything but my own gut feeling.  They're actually not much higher than One Electron which is considered a budget transformer, but the price of the metal covers has to be taken into account too so overall they are a little expensive.  Lundahls are really ugly looking without the covers so they're pretty necessary.

 

I would like to get some custom O'netics transformers from Bud Purvine for my future 300B monoblocks, but maybe it would be easier to just do Lundahl again.  Glenn seemed to really like the Lundahl main power transformers too.

post #5057 of 10643
Quote:
Originally Posted by Clayton SF View Post
 

 

Another member of the Glenn Amp mA Meter Club.

Hey, I recognize that cart! :)

 

My hat is off to you for introducing me to the joys of owning furniture with wheels on it.  :D

post #5058 of 10643

You can expect different biasing with different tubes of the same type depending how strong they are.

 

But once they settle in you should not need to change the bias.

post #5059 of 10643
Quote:
Originally Posted by Xcalibur255 View Post
 

 

All good points.  I'm learning what needs to be learned about working with old DHTs slowly but surely.  You touched on another question I had, if I put a different pair of tubes in will the bias be way higher or lower?  If the current jumps way up for a short period of time can the tube literally be fried by that if it is too high, and conversely is there such a thing as too low as well?  I am going to get another 46 tube and try your adapters as well, but the nominal current on a 46 is I think 22mA.... so what happens when I put them in the socket will they shoot up the 36 and get fried?  There is so much to know and it's hard to guess without a working knowledge of the circuit.  I need your wisdom!  :D  Is it a good idea to turn the bias down some before swapping tubes, or just put the new ones in and adjust once they are conducting and you can see where they are drawing at?

 

I don't claim to have golden ears, but each change from 32 to 34 to 36 produced a difference in sound I found quite easy to spot.  So far higher seems to sound better.  Once I went to 36 the amp really began to achieve the transparency I was hoping for.  It tightened up the bass very nicely too.  Maybe I'm just crazy, but the tubes seem to sound better after I adjust bias too, whether it be up or down.  The treble seemed a little harsh yesterday, the longer I listened it kept getting more "tizzy" but the second I tweaked the bias pots it went away and sounded great.  Maybe these Emperor tubes are just not very good 45s, I was not very confident about them when I bought them but the Emperor branding was really unique so I bit.  Next week I will probably switch to my Tung Sols.  I want to see how much change in sound I'm going to get by rolling the 45s.

 

I did try to get a photo of the amp running but they won't turn out, it always looks really crappy.  The C3g doesn't glow brightly, there is a mild glow at the top edge of the filament and a dim red glow along the heater/cathode (not sure if I even have that right?), but all in all they are sort of like the 45s they don't put on much of a light show.  The rectifiers produce the most glow by far which isn't saying much because you are just getting 4 glowing dots there too.  I still say the 5998 is the most beautiful tube to see in the dark.  They are like bright orange jewels.  The OTL puts on a much better light show than the 45 does. 

 

My thanks btw, to Stavros and Clayton for their helpful responses.  Glenn too of course.  I want to make sure I'm following good practices with biasing.  The training wheels are off but I'm not riding steady yet. 

When you put in a 46 the cathode current will go way down and you will have to turn it up

I did try the 46 and ran it at 38 ma it actually has a larger plate then the 45 and can handle the 38ma.

You just have to remember to turn down the bias pot before putting the 45 back in.

the 46 is a low cost tube so if you run it hot it don't really matter..

 

DHTs sound best when run hot at there max current.

post #5060 of 10643
Quote:
Originally Posted by Xcalibur255 View Post
 

 

I would like to get some custom O'netics transformers from Bud Purvine for my future 300B monoblocks, but maybe it would be easier to just do Lundahl again.  Glenn seemed to really like the Lundahl main power transformers too.

 

I still will use the Lundahl Power transformer on all amps that have output transformers. No mater what the cost of them are.

So the output transformer don't pick up hum from the power transformer Lundahl have very little magnetic field around them.

post #5061 of 10643

My 300b does make some noise, luckily it's not audible when listening

post #5062 of 10643

That is why I am using only Lundahl power/mains transformers from nowon

Tyrells amp is dead silent no hum pickup from the power transformer.

Your R core transformer is not that bad as E-I transformers I will only use

these with OTL amps from now on.

OTLs have no output transformers to pick up the hum.

post #5063 of 10643

Anything I can physically do to reduce it maybe? Like change the feet or something? (A suggestion from Stavros)

post #5064 of 10643
Quote:
Originally Posted by Ultrainferno View Post
 

Anything I can physically do to reduce it maybe? Like change the feet or something? (A suggestion from Stavros)

You can try to change the feet the transformer could be vibrating at 50Hz and be picked up by the tubes.

Make sure you take off the bottom plate and remove the nuts or you will break off the screws trying to remove them.

The plate is threaded and the nut locks it.

But it is probably the magnetic field being picked up by the output transformers. This is why I am switching to

Lundalh power/mains transformers.They do not radiate a magnetic field like other transformers.

You can look in the Leben CS300 thread they have the same problem and that is a very expensive amp with

a cheap power supply. But it is the power/maines transformer that is causing the problem.

post #5065 of 10643
Don't get me wrong, the buzz is not audible trough the speakers or headphones (luckily)n like I said it is the best sounding amp for my he-500. You can just hear the amp buzz on the table.

So maybe changing the feet might decrease the contact with the table and maybe that would reduce the buzzing impact
post #5066 of 10643

It seems that your are talking about the mechanical hum not hum thru the lines. If this happens to me I sometimes check the mounting screws for the transformer making sure they are tight and/or use rubber washers. Tall rubber feet for the bottom of the unit is something that I would look into.

post #5067 of 10643
Quote:
Originally Posted by Ultrainferno View Post

Don't get me wrong, the buzz is not audible trough the speakers or headphones (luckily)n like I said it is the best sounding amp for my he-500. You can just hear the amp buzz on the table.

So maybe changing the feet might decrease the contact with the table and maybe that would reduce the buzzing impact

Changing the feet might do it I guess the transformer is vibrating at 50Hz  I didn't notice this at 60Hz in the US

but maybe it was there and I didn't notice it. And the table I had it on when listening had a Slate top that weighs

a tun. Don't think it can transfer vibrations into that.

 

Also maybe putting something under the amp will stop it.

 

Just remember to remove the bottom and remove the nuts before trying to unscrew the feet

post #5068 of 10643
I can attest that my amp is dead silent. The noise floor is remarkably low for a tube amp. The 45 tubes themselves seem to make a high pitch whine, not in the headphones but physically in a way you can hear anywhere in the room. Might just be these particular tubes.
post #5069 of 10643

My Glenn Amp 300B mono blocks sound incredibly fine now. The bass has opened up and the highs are clean without rolling off. Midrange is excellent too. But it took about 6 months to settle on a tube: The Russian 5U4G black plate rectifier. Since I was rolling rectifiers I think that the Russians just needed time to break in. Also up there with the Russian is the RK-60. Very close in sound but ever so slightly warmer. The next are the GZ37 and the Tung-Sol 5U4GB. The GZ37 are the warmest and give the amp a little more oomph.

 

There is a slight hum that comes out of the speakers but you can't hear it from where I am sitting which is 5 feet away from the Zu Audio Omens.

 

I am very happy. :)

post #5070 of 10643
Quote:
Originally Posted by 2359glenn View Post
 

Changing the feet might do it I guess the transformer is vibrating at 50Hz  I didn't notice this at 60Hz in the US

but maybe it was there and I didn't notice it. And the table I had it on when listening had a Slate top that weighs

a tun. Don't think it can transfer vibrations into that.

 

Also maybe putting something under the amp will stop it.

 

Just remember to remove the bottom and remove the nuts before trying to unscrew the feet

 

I'll upload a small video later to show you what it does :smile:

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