DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 16 Jul 2019, 04:22

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 9 posts ] 
Author Message
PostPosted: 25 Jan 2019, 10:55 
Offline

Joined: 01 Nov 2015, 09:31
Posts: 13
I couldn't remember but I believed there was a pop noise too but not that loud before I upgraded the caps on my tube amp. Every time the Amp is on, the B+ kicks in then a loud pop on the speakers, there is no hum even the volume is all the way down. I have high voltage delay installed so the B+ is on after 60 seconds after the heater. Everything is working after that pop. Is it normal for tube amp? I am thinking to get a speaker protection circuit, wonder that would fix it.


Top
 Profile  
 
PostPosted: 25 Jan 2019, 12:53 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1586
Location: US Pacific Northwest
The B+ coming on is causing the thump. Usually this is caused by the B+ interrupter being placed after the power supply filter rather than before. Proper placement of a B+ interrupter is after the first capacitor and before the remainder of the B+ power supply filter.

Usually, there is no need for a B+ delay on vacuum tube equipment unless using mercury vapor rectifiers or VERY high B+ values (e.g. >1000 Vdc). Did the amplifier originally have a B+ delay circuit?

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 25 Jan 2019, 13:54 
Offline

Joined: 01 Nov 2015, 09:31
Posts: 13
I put the HV Delay right at B+ and R15. It's YAQIN_MC100B. Attached is YAQIN_MC100B schematic with the point where I soldered the HV Delay. So you mean I don't need HV Delay to protect the tubes?

Image

Image


Top
 Profile  
 
PostPosted: 25 Jan 2019, 16:26 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1586
Location: US Pacific Northwest
Alashikata wrote:
So you mean I don't need HV Delay to protect the tubes?
It's pretty much impossible to strip a cold cathode with 500 Vdc.

But if your really interested in keeping the B+ delay I would strongly recommend that you put it between the diode bridge and the 260µf main filter cap. And that you include an appropriate LC section between the main reservoir capacitor and the amp. The series inductance and shunt capacitor will help prevent the "pop" or "thud" (while providing some additional filtering). Then you can also reduce that first reservoir capacitor as your conduction angle must be so short that it's dumping a lot of heat and stress on your power transformer.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 25 Jan 2019, 17:08 
Offline

Joined: 01 Nov 2015, 09:31
Posts: 13
Do you mean at the option 1 or 2? I haven't traced down the other points yet but that location is the most easy one to install HVD. Some people said it will keep the tube last longer. Since it's less than 400v, I may remove HVD if it annoys too much. Reduce delay to 10 seconds instead of 60s would help?

If LC needs, what value should I get?



Image


Top
 Profile  
 
PostPosted: 25 Jan 2019, 19:25 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1586
Location: US Pacific Northwest
Alashikata wrote:
Do you mean at the option 1 or 2?
There is no function difference between 1 and 2; do whichever is easier.

Alashikata wrote:
Reduce delay to 10 seconds instead of 60s would help?
This would likely make little difference. The power tubes are not fully warm so the thump would likely be reduced a little, but you would still be hitting the tube with a rapid onset high voltage.

Alashikata wrote:
If LC needs, what value should I get?
The values are not that critical. An inductor of a 2H to 5H would be more than enough, with a shunt capacitor of ≈100µf. The inductance provides an impedance to keep the voltage from rising too rapidly and the voltage cannot rise any faster than the capacitor charges. I.e. the capacitor voltage will exhibit a finite rise time in response to a step voltage input.

In the ideal case, the step response of such a section would be a dampened oscillations. However, in the real world, the internal resistance of the inductor, and the non-zero source resistance of the transformer and bridge are enough to over damp the section and result in a nice gentle rise in B+ to the nominal voltage (i.e. no thump).

Additionally, the 2H/100µf solution would give an additional 41dB of filtering at the primary ripple frequency (i.e. quieter amp).

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 25 Jan 2019, 20:08 
Offline

Joined: 01 Nov 2015, 09:31
Posts: 13
Thanks Suncalc, I will try it later to see if it works


Top
 Profile  
 
PostPosted: 27 Jan 2019, 16:32 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 3987
Location: Arizona, USA
Hi, I'm with Suncalc on this. I put the delay relays between the rectifiers and first cap. They are usually not needed on amps running 500 volts or less, but can make folks feel better about having them. It can however prevent the filter caps from seeing voltages above their ratings during turn on. If there is no load on them then the voltage when using solidstate rectifiers can reach about 1.4 times the rms value of the transformer. With say 380 rms that would work out to about 504 volts dc on the caps. Yes you can buy caps rated to handle 600 or 650 volts but if you keep the B+ at a more reasonable level you can use 500 volts ones that are a lot cheaper.

EDIT: If you are using a relay it ought to have a snubber capacitor and resistor across the terminals as well. This can often reduce the arcing (causing the pop) and will preserve the contacts in the process.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
PostPosted: 30 Jan 2019, 11:06 
Offline

Joined: 01 Nov 2015, 09:31
Posts: 13
I did with opton 1, so 1 channel is dead quiet now :) Setting the Delay 45 seconds or more doesn't change anything. So I decided to set at 45-50

Another channel still make a little beep but no hum after that

There was one weird thing with the 12AX7 tube on the beep channel, I could smell burning a little so I turn off right away. Swapped with different tube, then it worked fine. Then I decided to put back the other tube, it's working without problem. Was I inserted the tube incorrect? That sounded impossible with all the pins.

Would the beep sound cause by B+ wire crossing between the caps? I couldn't think what other cause the beep. Would tubes causing the beep too?. That yellow wires are from B+ PT for the right channel still has a small beep sound.

Image


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 11 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy