300B stereo SE amp and PP2A3 monoblocks

[BHD]

Hammond makes both 15W and 30W rated 5K output transformers, and I wanted to know if there would be any sonic advantage to using the 30W since its only a few bucks more...

 

[fdegrove]

Hi,

and I wanted to know if there would be any sonic advantage to using the 30W since its only a few bucks more...

Generally speaking the higher wattage should be the better sounding one.
I don't know if this is the case for the Hammond models though.
Either way a 15W OPT for a PP 2A3 seems a bit limited.

Mine are actually 30W 6K6 OPTs made by REX from Japan and they're doing fine (they must know I don't like OPTs much ) even though they're better suited for a PP of 6L6 and family.
With the slight impedance "mismatch" you lose a couple of Watts but you get less THD as well.
As I'm only using local feedback this comes in handy.

Cheers,

 

[arnoldc]

i'd say go for the 30W as it also gives you the flexibility (if you decide later to use it for another circuit). better sounding? frank already confirmed that.

 

[ThorstenL]

Konnichiwa,

I'm probably going to try a FW SS bridge rectifier with a damper diode - that way I'll at least have more voltage to play with. It should keep costs down, too.

As said before, I find the cost on many nice NOS Rectifiers to be pretty notional Between $ 10 - $ 20 so cost should not be an issue. More voltage also in not neccesarily a "good thing". The key is to have the "right" voltage.

I'm planning on heading over to Europe next year and I just may arrange a stop over and take you up on it!

If you find yourself in London, my door is also open...

The 274B copy interested me, but it's a bit pricey for a first attempt.

The chinese 274B (Shuang made, sold under Gold Dragon and other labels, NOT the TJ one) costs around $ 15 - $ 20 each.

I went through the article on damper diodes in VTV and there are plenty that I can use that don't have anode caps, so it's cool.

Go for it but consider using two of the damper diodes as the "positive" diodes in a normal bridge. That pretty reliably eliminates the reverse bias spike problem that plagues all silicon diodes (other than shottky) to a certain degree.

Any opinions on the 12SX7GT?

Not really. I never really get on with the 6SN7 Type Valves. They are okayish, but I can usually do much better using others.

Could you go into more detail about the medium transconductance pentodes?

In what sense? Basically think WECO 91 Style Amplifier but with reduced Anode load and adjusted operating point. Examples are the EL84, C3m (both at 150V G2, 250V Anode and around 15mA anode curent with 12K Anode load) for 300B. Or Valves like the 717A used by Yamamoto.

A short guide to using Pentodes as Drivers I'd suggest a target Anode voltage that is more than the required swing above the screengrid and that anode current, bias and screengrid voltage need to be selected to provide enough transconductance to generate the required swing across the anode load without bringing the control grid to close to 0V GK.

Under such conditions the screengrid behave as pretty reasonable current sink. It starts drawing more current once the Anode voltage approaches the screen voltage and the screen current really hit's roof once the anode is lower than the screengrid.

I think I remember reading a thread where you posted info on that (maybe even a link), but I've been studying Franks, SY's and your posts for MONTHS now and I can't seem to find that thread...

I covered calculating Pentode drivers in my DC coupled Valve Amplifier series of articles in Tubes

Sayonara

 

[ThorstenL]

Konnichiwa,

Hammond makes both 15W and 30W rated 5K output transformers, and I wanted to know if there would be any sonic advantage to using the 30W since its only a few bucks more...

More often than not a physically smaller transformer will sound better, if it handles the power at LF.

Sayonara

 

[jlsem]

The Shuang 274B Copy, the russian 5U4 and GZ34 Clones are all not bad. But you can still get a lot of nice NOS Rectifiers, if sometimes with UX-4 basing. Just look around.

For the best deal on a tube rectifier, try a NOS 5X4G. They are pretty cheap at AES. The WWII era ones sound as good as any 5U4G, and almost right up there with NOS 274B's. A 5X4G IS a 5U4G/274B with a different pinout.

John

 

[contaxchen]

Generally speaking the higher wattage should be the better sounding one.

I really question that. Original WE 300B is design for 8Watt ouput each tube. I think there is a optimal value for output transformer for every specific tubes.
C.C.

 

[fdegrove]

Hi,

I think there is a optimal value for output transformer for every specific tubes.

I think it's reasonable to assume that the Hammond OPTs are just standard OPTs, not optimized for any particular output tube.

15W OPT for a PP 2A3 would be a little on the low side powerwise.
Given the small difference in price and all else kept relatively the same the higher wattage one would be more appropriate IMO.

Cheers,