Dual Simple SE's in Push Pull w Differential Input - Page 3 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 17th October 2010, 06:58 AM   #21
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
Decided to return the KT88's. I realize I am pushing the transformer, and I don't need that much power. I ordered a quad of 6V6-S's. Looks like they are good up to 500V.
JJ 6V6S

I also have some EL84's, so I'll try out both. I am a little concerned about the choke 200ma rating when used with the EL84s. I probably should have ordered a bigger choke, but I am out of real estate on my chassis.
  Reply With Quote
Old 17th October 2010, 07:05 PM   #22
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
Default It Works!!

I hooked it all up a on temporary piece of plywood, just to work out all the details, take measurements etc. A friend with a mill is cutting some holes in a proper chassis for me meanwhile.

Anyway, it sounds AWESOME. Absolutely fantastic. Thanks George for a killer design of the SE, and it really works great in PP.

I was a little concerned that the OPT were a little too big for the power I would be running them at, but there is a lot about of detail coming through. And the bass really extends very deep and clear.

In fact, the EL34's are probably way more power than I need. But I will run them for a while to see how I like them. I'll pop in the 6V6-S's later.

I feel like I am in the minority here, but after listening for a few hours, I tend to prefer the sound of UL vs triode strapped. In triode, I find the treble kind of grating and irritating, and the bass does not extend down so far. It could be that my speakers which are horn loaded, so I don't need need the mids highlighted.

Anway, I am very pleased. Thanks again George.
Attached Images
File Type: jpg se 001.jpg (92.1 KB, 252 views)
File Type: jpg se 003.jpg (73.5 KB, 245 views)
  Reply With Quote
Old 18th October 2010, 09:48 AM   #23
Ian444 is offline Ian444  Australia
diyAudio Member
 
Join Date: Nov 2008
Location: Brisbane QLD
So good to see a great outcome. You are a much smarter cookie than I would have thought. Big learning curve and you managed to put it all together, even with unorthodox differential input. I say extremely well done!
  Reply With Quote
Old 18th October 2010, 11:12 PM   #24
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
Default Tube Selection

Thanks for the complements, but it turned out to be a lot easier than I thought at the outset. Mostly followed George's instructions, and learned a few things along the way.

One thing I learned is that although the El34's do sound good indeed, it is a whole lot of power. Although the amp can be very delicate at low levels, it can be downright pummeling. Also, since I am using a single GZ34 tube + C354 choke, I seem to have restricted myself to 200ma MAX. The choke is getting damn hot and I've heard that the GZ34 doesn't like much more than 200mA either. I currently have the 84's biased at ~53ma/23W.

I am going to try to select some not so pummeling tubes (to my ears and power supply).

I'm looking for some tubes that like the 420-450 range, and that bias in this situation in the less than 40mA range.

So far, some likely candidates are:

6V6-S
7591-A (I think)

Any other recommendations? New production only, and not impossible to find.- Thanks
  Reply With Quote
Old 19th October 2010, 01:42 AM   #25
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
Also, since I am using a single GZ34 tube + C354 choke, I seem to have restricted myself to 200ma MAX. The choke is getting damn hot and I've heard that the GZ34 doesn't like much more than 200mA either.
You can use 2 5AR4's and 2 chokes if you want. Just wire the power transformer secondary to both boards, and then run each board off of its own rectifier and choke. That's how I had mine connected. Your transformer has a 4 amp 5 volt winding, so there is enough current to feed 2 rectifiers. The rectifiers are essentially in parallel since they share a common heater winding.

Quote:
Any other recommendations? New production only, and not impossible to find.-
Most 6L6GC's should work. I use the cheap Chinese ones. You are still going to get loud, about 30 WPC worth of loud. I think that you will find that the EL34's sound better though.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 21st October 2010, 12:32 AM   #26
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
Quote:
Originally Posted by tubelab.com View Post
You can use 2 5AR4's and 2 chokes if you want. Just wire the power transformer secondary to both boards, and then run each board off of its own rectifier and choke. That's how I had mine connected. Your transformer has a 4 amp 5 volt winding, so there is enough current to feed 2 rectifiers. The rectifiers are essentially in parallel since they share a common heater winding.
Ok, so all you are saying is populate both power supply sections of both boards. Have the HV secondary as well as the 5V secondary connect to both boards. Connect the 2 chokes to their corresponding board and thats it.

Since the rectifier filament appears to be tied to the unfiltered B+, and if each rectifier tube's output is slightly off with to respect to the other, I would think that the higher unfiltered B+ would 'go into' the lower potential B+. I have paralleled 2 power supplies before (not tube rectified), in which case I would put a diode on the output of each one, and connect the cathodes together. But really, I don't quite understand how the heater winding works, especially in a tube rectifier, so I totally take your word for it. I just want to make sure my interpretation of what your saying is correct before I go making 400+V connections.
  Reply With Quote
Old 21st October 2010, 01:24 AM   #27
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
I would put a diode on the output of each one, and connect the cathodes together.
Think about it this way. The HV primaries are going to both boards, so the plates of the rectifier tubes are wired together. The 5 volt heater windings are going to both boards so the cathodes of the rectifier tubes are wired together. So what you have are two rectifier tubes wired directly in parallel. Yes they will not share the current exactly equally, but two tubes in parallel will deliver more current than one alone. It would be wise to use identical rectifier tubes to help equalize the current sharing. If you haven't placed C1 on one of the boards leave it out. This will make life easier on the tubes on start up and won't affect the voltage much. You need ONE C1 but two may be too much for the weaker of the two tubes.

You could simply wire the two chokes in parallel and run both boards on the doubled up power supply, but there is some channel seperation improvements to be gained by seperating the two channels after the rectifiers. So one choke drives each board using the C2 on its particular board. The ckokes will run cooler since each only runs one channel. This provides most of the benefit of dual mono operation without the expense of two power transformers.

Make sure each transformer wire goes to the same terminal on each board.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 21st October 2010, 04:09 PM   #28
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
I got it.

I have some more parts on order and will report back once I wire it up.- Thanks
  Reply With Quote
Old 26th October 2010, 01:18 AM   #29
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
So I did what you said. Jumped the HV secondary and the 5V secondary from board 1 to board 2. I was careful to keep the same polarity on each. On board 2 I left off C1. I have 2 chokes now- each wired to its corresponding place on each board. The chokes are not 100% identical. One I got at dynakit parts, and is unshielded and as usual fairly ugly. The other is the same spec, but I bought from Triode. Triode has the nicer looking shielded version, and since I am out of room under the chassis, I figured this one looks OK to put on top.

Anyway, it was odd that the choke on board 2 (Triode elec) was getting warm (but not hot), and the choke on board 1 was not (dynakitparts).

I measured B+ on both boards. B+ on board 1 was 422V and on board 2 it was 407V.

Upon closer inspection, I realized that the new rectifier tube, on board 2, was not the same as the first one. My original rectifier on board 1 was a sovtek 5AR4. I ordered the same part again, but for some reason they sent me a JJ GZ34. Anyway, maybe this explains the weirdness. I'll see if I can return this JJ for the actual part I ordered.

Could the use of 2 different tubes cause this much of a discrepancy? I also wonder why one choke was so much warmer than the other. I'll check my connections again, but I am pretty sure its all correct. I have R2 installed on both boards. Is this correct?
  Reply With Quote
Old 26th October 2010, 02:18 AM   #30
Anchan is offline Anchan  United States
diyAudio Member
 
Join Date: Jul 2009
I just realized that I had both red wires from the middle of the OPT's connected together, both tying to the 2nd board's B+. That is now corrected, and each red wire from each OPT goes to its corresponding B+ on the different boards.

Each board is getting about 415-420 V now. I still plan on returning the JJ for a Sovtek.

When I had one rectifier and one choke feeding both boards, B+ was around 425-430V.

Last edited by Anchan; 26th October 2010 at 02:25 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Differential push-pull design question Tyimo Tubes / Valves 4 15th January 2010 08:05 PM
laying out dual output push-pull transformer? zilog Power Supplies 0 2nd September 2008 09:50 PM
A push-pull differential stage- why not? darkfenriz Solid State 53 23rd December 2007 02:00 PM
single cabinet...dual rlp-15's...push pull? kramskoi Subwoofers 1 26th March 2006 12:34 PM
A very simple push-pull project darkfenriz Solid State 5 6th September 2004 10:26 AM


New To Site? Need Help?

All times are GMT. The time now is 06:11 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2