Simple SE - very low volume - Page 2 - 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 26th October 2010, 12:39 PM   #11
Divad89 is offline Divad89  Denmark
diyAudio Member
 
Join Date: Feb 2010
I've just gone through the resistors again, and it is the correct resistors (R11 = red-red-yellow-gold = 220 kohm, R12 = brown-black-black-black-brown = 100 ohm).

In this picture you can see how I wired it up:

Click the image to open in full size.

And here is the actual wiring (a bit confusing):

Click the image to open in full size.

I've also tried changing the 12AT7 between 3 different tubes, changing the 5AR4 between two, and changing between 6L6GC and 6550 tubes.

Nothing has helped so far, I can stand about 1 meter from it, with the volume control at max, and with speakers with a sensitivity at 89 db.

PT: Edcor XPWR059
OPT: Edcor CXSE25-4-5K
Choke: Hammond 193H
Auxiliary power supply cap: Eyuda 80F 500VAC
Cathode bias resistor: 560 ohm 5W
Pot: 47 Kohm pot

---
David
  Reply With Quote
Old 28th October 2010, 09:49 AM   #12
Ian444 is offline Ian444  Australia
diyAudio Member
 
Join Date: Nov 2008
Location: Brisbane QLD
What are you using as a source? Is there any difference in volume between triode and ultralinear? The output wiring looks good as far as I can see, do you have eight speaker binding posts on the back panel? (far LHS bottom of pic). It looks like you have 3 pairs of inputs, a power switch, a triode/UL switch, a cathode feedback switch, and eight speaker output terminals, is that right? Are you getting the same volume from each channel? Does the volume pot and input selector work correctly? Can't think of any more questions right now...
  Reply With Quote
Old 28th October 2010, 12:14 PM   #13
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Quote:
Originally Posted by Ty_Bower View Post
...your measurement of R11. I assume you are checking from the grid pin of the 12AT7 socket. Turn the pot all the way towards quiet, and you'll probably measure 100 ohms. Turn the pot all the way towards loud, and I'd expect you would measure ~38.8K ohms (47K in parallel with 220K, plus 100 ohms for R12).
Have you tried this? Does the resistance vary depending on the position of the volume knob?
  Reply With Quote
Old 28th October 2010, 05:46 PM   #14
Divad89 is offline Divad89  Denmark
diyAudio Member
 
Join Date: Feb 2010
Yes you (Ian444) are right about everything on the back panel (I have eight speaker channels because of bi-wire speaker cable), and the input selector and volume pot works just fine, apart from the low volume of course.

And Ty_Bower I have tried measuring the resistance at the different positions, and towards quiet it showed 100.7 ohms and towards loud it showed 40.9 kohms...

---
David
  Reply With Quote
Old 28th October 2010, 06:30 PM   #15
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Well, if the board is assembled correctly and your input wiring is good, then you should get a pretty healthy voltage swing out of the first stage. You ought to be able to connect a source, turn up the volume, and measure at least a good 25 volts AC at the grid of the power tube (pin 5). I've noted the places on the underside of the board where you can try to put your meter. You're checking for AC between ground and any one of the four circles I've drawn. If you have clip probes, you could clip one to the exposed lead from the coupling capacitor. Clip the other lead to ground. Set your meter for AC volts. Be careful and keep your fingers away from the underside while the power is on.

Click the image to open in full size.
http://i69.photobucket.com/albums/i4...SE/Measure.gif


Wiring errors commonly occur between the output transformer and the speakers, especially if you've got UL or CFB switches. Here's George's advice on the topic:
Quote:
Originally Posted by tubelab.com View Post
There have been two or three SSE's that had a bad channel upon initial power up. Most have been traced to a problem with the speaker jacks. The simplest way to test for this is to disconnect the output wires on the OPT from the rest of the amp and connect them directly to the speaker using clip leads. If this results in sound then there is a problem with the speaker jacks or the wiring.
  Reply With Quote
Old 28th October 2010, 06:42 PM   #16
Divad89 is offline Divad89  Denmark
diyAudio Member
 
Join Date: Feb 2010
Is that with all the tubes in place when I measure it?

---
David
  Reply With Quote
Old 28th October 2010, 06:50 PM   #17
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Quote:
Originally Posted by Divad89 View Post
Is that with all the tubes in place when I measure it?
A sticky question, but a good one. You'll need the 12AT7 and the rectifier tube installed to get a signal out of the first stage. Normally I'd say you could try it without the power tubes (6L6, or whatever you're using) but in your case I'd advise against it. If you power up the amp with the rectifier in, but the power tubes out, you're going to get a lot of volts out of the unloaded power supply. I can see from your photo that one of the supply cap is only rated for 450WVDC. You'd be at risk of over-volting it.

Keep all the tubes in.
  Reply With Quote
Old 28th October 2010, 07:36 PM   #18
Divad89 is offline Divad89  Denmark
diyAudio Member
 
Join Date: Feb 2010
I've just tried it, and it showed very different results depending on the music and the position of the volume pot. Towards quiet it showed just around 4-6 v and all towards loud it showed around 10 v (but this was with a discman connected, I've tried before the sound level between the discman and from a RIAA and the difference in the sound level was very little).

---
David
  Reply With Quote
Old 28th October 2010, 08:19 PM   #19
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Ten volts is less than I expect, but might be OK. It depends on how fast your meter responds. The signal is going to bounce around with the music. At least it shows you've got some gain from the 12AT7.

Have you tried measuring the plate, screen, and cathode voltages of the output tubes? What's your B+?

What's going on with the wiring from the output transformer's secondary (orange and white?) and your cathode feedback switch? It looks like for one channel you wired the orange lead directly to the speaker terminal, and for the other it goes to the CFB switch. That looks suspicious. You might want to consider desoldering both the orange and white leads, and connecting them directly to your speakers. Use clip leads or some kind of extension - they won't have enough length to safely reach your speakers without. Also make sure you disconnect your wiring at T2-SEC and T3-SEC, and install a short jumper wire between the terminals.
  Reply With Quote
Old 28th October 2010, 11:15 PM   #20
tomchr is offline tomchr  United States
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Greater Seattle Area
Maybe I'm confused, but I don't see a way you should be able to measure 100 ohm as the input impedance regardless of volume setting.

If the volume control is connected as shown in the schematic, the resistance measured between the center pin of the input connector and ground of the input connector should be:

47k || 220k = 38.7k at the high volume setting
47k at the low volume setting.

If you measure at the input terminals on the SSE board, you should get:

47k || 220k = 38.7k at the high volume setting
0 ohm at the low volume setting.

Due to the resistance of the wiring and pot contacts, you won't get exactly zero ohm at the low volume setting, but you should get less than 10 ohm.

Above measurements are performed with the amp power OFF. If actual measurements aren't even close to above (100 ohm instead of 38k for example), try pulling the input tube and measure again. If you get the correct values with the tube out of the socket, the tube is bad. This is not very likely.

If you measure from the center pin of the input connector to the point where R11, R12 meet (amp input), you should measure 0 ohm at high volume and 47k at low volume. If you don't, the pot is wired incorrectly.

My guess is that the grid end of R12 got shorted to ground through a solder blob, tin whisker, or rouge strand of wire somewhere. Check around pins 2, 3 and 7, 8 of the tube socket. Check both sides of the board. Clean the flux off with acetone on a cotton swab.

~Tom

Last edited by tomchr; 28th October 2010 at 11:18 PM.
  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
Simple SE - Right side with low volume and crackly sound Salsero Tubelab 20 20th May 2010 12:26 AM
subwoofer volume for simple se royd55 Tubelab 13 23rd January 2010 05:04 AM
Volume pot for Simple SE bigjppop Tubelab 4 17th January 2010 07:50 PM
Stoked about new volume control for my Simple SE BillEpstein Tubes / Valves 10 9th June 2009 07:32 PM
Volume pot for simple se newtube Tubes / Valves 7 19th May 2009 03:34 AM


New To Site? Need Help?

All times are GMT. The time now is 07:17 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