Mono push-pull driver PCB - Page 20 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th January 2013, 01:37 PM   #191
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: South Florida
Quote:
I'm thinking a PP or even PPP with 18GB5's outputs.....
maybe PPPP! I have 16 13GB5's mounted on perf board which will be used as two sets of 8 in a stereo amp. I intend to explore the upper regions of output power too, but I likely won't get back to it for about 6 weeks.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 8th January 2013, 04:20 PM   #192
diyAudio Member
 
pmillett's Avatar
 
Join Date: May 2005
Location: Dallas (but I am not a Texan!)
Quote:
Originally Posted by pso View Post
Hi, the version with KT88, is finished or still in progress?
I will go back to the KT88 to double-check, but I think this same design will still work fine with KT88's.

As for a "real" build, I am going with parallel 5B/254M's:

Click the image to open in full size.

5B/254M @ The National Valve Museum

(Just an 807 in a lovely loctal base)

Pete
  Reply With Quote
Old 8th January 2013, 08:25 PM   #193
tomlang is offline tomlang  United States
diyAudio Member
 
tomlang's Avatar
 
Join Date: Oct 2009
Location: Augusta, GA
What about a PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP 13GB5 amp? Here is a pic of 50 in this box, I have another 50 in another box from Rogalski's at 50 cents each in quantities of 100. Says "Made in USA", not sure if these are the "big power" 13GB5's or not.

The nine pin sockets were 35 cents each and the plate caps 30 cents each from Goodcomponent.com. Shipping almost doubled the cost but still a deal. The sockets are #GZC9-2-F and caps #MCV. Caps fit the top nipple but do not shroud the whole thing.
Attached Images
File Type: jpg 13gb5_1.JPG (335.9 KB, 347 views)
File Type: jpg 13gb5_2.JPG (420.5 KB, 340 views)
File Type: jpg 13gb5-3.JPG (292.2 KB, 319 views)
  Reply With Quote
Old 8th January 2013, 09:02 PM   #194
pso is offline pso  Spain
diyAudio Member
 
Join Date: May 2010
Location: Valencia
Finally, how will be the B+, 450 or 560V? as indicated in the post 152.

Any update about the boards for the PSU?
  Reply With Quote
Old 9th January 2013, 01:55 PM   #195
wicked1 is offline wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
I got it powered up last night.. Voltages all checked out, got the driver board set up, plugged in the output tubes (3d21wb's, for now). I turned up the bias and they biased properly, (put them at 40 ma) but I had a loud buzz. I turned it off for a quick checkout.. Moved some heater wires, etc. Then turn it back on.. It gets very loud. I look at the meters on bias, and they are pulling about 100ma! I turn the bias all the way down and they are still pulling 40ma! (first power up, w/ the bias all the way down, they don't conduct at all).

So, this morning b4 work I checked the bias voltage, and it's still fine.. (-80v is the max, which is how it was originally).

Now I'm stumped.. What would cause that? My first guess is it's the tubes.. For one, they came out of a huge bin of random unboxed tubes.. And 2nd I've got no plate caps and only have wires wrapped around the anodes.. Would the screen burn up if the plate got disconnected? And could a burned screen cause problems like this?
  Reply With Quote
Old 9th January 2013, 04:15 PM   #196
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: South Florida
I had issues with some of my used 3D21WB's. The 5 new ones that I got from ESRC seemed OK but I didn't run them for long. Some of the used ones exhibited bias creep and eventual runaway. Looking back now I believe it was a grid current issue but I don't have an amp set up to play with it right now.

I have a box full of the small plate 3D21B's, but I think they will go to the hamfest next month. I still have way too much stuff in my house.

Quote:
Would the screen burn up if the plate got disconnected?
It is possible, and likely if the screen is connected directly to a power supply. I usually put a resistor in series with the screen. I undersize it (1/2 or 1 watt) during testing but use a 2 watt part for a final design. The resistor will smoke if the plate goes open. The screen will glow white hot before it fries, so it is usually obvious.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 9th January 2013, 06:34 PM   #197
wicked1 is offline wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
Thanks George. One of the tubes was causing trouble.. Now it's all good

The horrible BUZZZ I had was a bad connection at the input ground.

Bias is still crazy.. As they burn in I have to keep turning it down.. a lot.. and the balance drifts all over the place.. One tube pulls about 1.5x the current for the first few minutes of operation, as it warms up. But.. that's all probably par for the course.. I'll let these burn in for a while.

WooHoo! I suppose I'll start building my regulators and get the other channel built w/ the gu-29 version.

FYI, I didn't pay attention to the amp for 10 min, and the current was up at over 100ma per side for a while.. Over 50watts. The tubes showed no signs of stress.
  Reply With Quote
Old 14th January 2013, 05:01 AM   #198
wicked1 is offline wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
PPP 829's
Regulated screen and bias
It is good!
Attached Images
File Type: jpg 829ppp.JPG (325.3 KB, 266 views)
  Reply With Quote
Old 18th January 2013, 01:35 PM   #199
wicked1 is offline wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
I've got two versions of this built and have been trying to decide which is the best... It's difficult! They are both similar enough that I can listen to them as a stereo set, and different enough to tell the differences between the no feedback triode version and the pentode (or tetrode) version. Basically everything every other thread has said on the topic is true. I think I like the triode a tiny bit more.. I think the pentode version sounds clearer, crisper.. It's probably technically better. Since it was my plan from the start, I think the 829 version will win.
What surprised me the most is the two versions are much more similar than different.. (I suppose that's how it should be.. we want to hear the music, not the amp)

If anyone is curious, these are my parameters:
7403 (kt88-ish) triode
492 on the plates
-57v on the grids 70ma
243v on the drivers. Drivers are triode too.

829 (807-ish) PPP Pentode (Or should I be saying Tetrode?) Regulated bias and screen supplies
590 on the plates
-28v on the grids 60ma
215v on the screens
305v on the drivers and 150v on the driver screens
UL to driver plate feedback, as well as global feedback. I decreased the global feedback a little after I added the ul to plate feedback. (the all triode amp was louder! and, I do like the sound of less feedback)
And actually, I dont have test equipment to really get in to it, but I did find the amp much more "listenable" after adding the UL to plate feedback.

I suppose I have one question.. Should the 10m45's be hot? As in, turn the amp off, let it discharge for a few minutes, and I still can't touch the heatsink for more than a second. Someone else has my IR thermometer right now, so I can't be more precise than that...

Last edited by wicked1; 18th January 2013 at 01:38 PM.
  Reply With Quote
Old 18th January 2013, 03:13 PM   #200
pso is offline pso  Spain
diyAudio Member
 
Join Date: May 2010
Location: Valencia
Hi, it appears that the 7403/3D21WB works very well here.

Any particular brand?

Where they are available?
  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
idiot proof mono push pull 6l6gc schematic wanted jasondace2b Tubes / Valves 29 13th October 2011 01:22 AM
Mono 5W-17W Power Amp using EL84 push-pull nbraz Tubes / Valves 30 27th July 2011 11:12 PM
Please Explain difference Mono vs Push Pull vs Single End etc hdlcx2 Tubes / Valves 11 3rd August 2008 02:27 AM
Push-Pull driver stage? alexmoose Tubes / Valves 12 18th September 2006 11:38 PM


New To Site? Need Help?

All times are GMT. The time now is 11:16 PM.


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