|
|
| Yes, No, Maybe.... [message #9467 is a reply to message #9466] |
Wed, 28 December 2005 05:32   |
Old Brown Eyes
Messages: 25
Registered: May 2009
|
Chancellor |
|
|
|
There is indeed some degree of truth to what you have heard. When a tube preamp first fires up the output cap has to "charge" up and this will take X number of time constants. During this brief period it can put out DC voltage to the power amp. Some power amps can be damaged by this even though they are switched off. It is rare and very few people have problems but it is possible. In all cases you would want to turn on the preamp first and give it a minute or two to settle down before turning on the power amp. For those power amps that can be damaged you would simply wait until for the preamp to warm up before plugging the interconnect into the power amp.
Russ
|
|
|
|
|
|
| Re: Yes, No, Maybe.... [message #9469 is a reply to message #9468] |
Wed, 28 December 2005 16:14 |
2wo
Messages: 44
Registered: May 2009
|
Baron |
|
|
|
It is true that you must turn on the pre before the power amp. As to other possible damage to your power amp? The risk is very slight. Go for it…John
|
|
|
|
| Re: Yes, No, Maybe.... [message #9471 is a reply to message #9469] |
Thu, 29 December 2005 20:42 |
PakProtector
Messages: 935
Registered: May 2009
|
Illuminati (2nd Degree) |
|
|
|
I'll second John's recomendation. However, the turn-on voltage transient is fairly well documented with that design and its predecessors. I'll go one last step further and suggesting a call to the tech support of your SS amp maker and see if a short duration spike 40-60V high would be any threat. and then there is the sonic side to the topic. I suggest you'll like a good tube pre. tubes properly done are(so far) unbeatable in my experience.
cheers,
Douglas
|
|
|
|
| There is a simple solution to the problem [message #9474 is a reply to message #9471] |
Fri, 30 December 2005 06:36 |
Old Brown Eyes
Messages: 25
Registered: May 2009
|
Chancellor |
|
|
|
If something was added, a switch or a relay for example, to short the output to ground at start up one would be protected. A long time ago I tried out the original foreplay with a solid state amp. Being ingnorant I was doing quick AB swaps between preamps. The solid state amp didn't mind but I did blow speaker fuses and didn't know why at the time:) Given that the new foreplay has dual secondaries I don't understand why they decided to parallel them, use a voltage doubler to create a raw 300VDC B+, and then CR filter it down to a OD3 150vdc regulated supply. Seems to me having more voltage to work with would be a plus....especially when direct coupling....heck maybe even a bi-polar supply for a big tail resistor in the CF. Russ
|
|
|
|
| Re: There is a simple solution to the problem [message #9475 is a reply to message #9474] |
Fri, 30 December 2005 07:07 |
PakProtector
Messages: 935
Registered: May 2009
|
Illuminati (2nd Degree) |
|
|
Hey-Hey!!!,
My first foray into a valve pre was quite similar to the foreplay circuit. I added the bipolar supply, and increased the CF tail load. It was running more current, and through a larger resistance. Adding a CCS there made little if any improvement. The shorting switch for the output is easy, a DPST will do quite well, and eliminated the risk of a large transient. With VR tubes, a CCS instead of a resistor to feed the VR tube has always worked better for me. Less of a need for a high raw voltage( like the 2x regulated that is suggested ). While you're building CCS-es, build two more for the plate loads, and do away with the CF stage. The mu-follower output from the MOSFET CCS is going to have lower output Z than most CF's anyway, and it eliminates the need for that extra stage.
cheers,
Douglas
|
|
|
|
| It may also affect power-down too [message #9477 is a reply to message #9467] |
Thu, 05 January 2006 11:41 |
GarMan
Messages: 960
Registered: May 2009
|
Illuminati (2nd Degree) |
|
|
|
For my Grounded Grid pre-amp and Gainclone combo, I get the infamous "pop" if the amp is turned on first. Pre-amp has to warm up for 15 seconds first to allow the caps to settle. To power off, amp must be down and out first before preamp or else I get the same "pop". But this may be specific to only my system.
|
|
|
|
| Power up, down sequence [message #9479 is a reply to message #9477] |
Sat, 07 January 2006 22:10 |
Shane
Messages: 1117
Registered: May 2009
|
Illuminati (3rd Degree) |
|
|
I was always told to power up the preamp, then amp, then source and power down in the opposite order --source, amp, then preamp. DOn't know if it's right or not, but that's how I've always done it with no problem. I'm looking to put a tube pre on my NAD c320Bee and was curious about tube to SS also.
|
|
|
|
Posting Rules
Members
Search
Help
Register
Login
Get a T-Shirt!
