Best Valve pre-amp match for ME 550 amp - Page 3 - 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 3rd December 2011, 02:51 AM   #21
ChrisA is offline ChrisA  United States
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by Zaphod Beeblebrox View Post
...
It is perfectly suited to any preamp which:

* Exhibits a source impedance of less than 10 Ohms.
* Is completely stable, with better than 1 or 2mV of offset.
* Does not deliver any switch on thumps, DC shifts or other nasties.
...

It it's obvious. Use an output transformer in the preamp and use the ME550's balanced inputs. It is impossible for a transformer to produce DC and we all know that transformers are available with 4, 8 or 16 ohm secondaries.



It sounds to me like what is needed is a very low power "integrated amp". So take your favorite tube preamp and add a 1 watt "power section" to it If you only need low power then single ended is reasonable. You could use a 6SN7 or 12au7 to drive a small single ended transformer such as a Hammond 125*se series. You could even go "exotic" and use a 3b7 tube and then have bragging rights to a DHT preamp.

The hammond OPT when driven at 10% of it's rated power will have plenty of bass.

Also the single ended triode likely gives the best "tube sound" and I assume that is the reason for going with a tube preamp
  Reply With Quote
Old 5th December 2011, 02:28 AM   #22
diyAudio Member
 
Join Date: Mar 2006
Location: Australia
Quote:
Originally Posted by ChrisA View Post
It it's obvious. Use an output transformer in the preamp and use the ME550's balanced inputs.
...actually the update on this is that the 550 Type I only has unbalanced inputs @ 1K ohms. (Its the 500 that has balanced ones at 2K...)

...so, <10ohms would be optimal for pre-amp output...

Quote:
Also the single ended triode likely gives the best "tube sound" and I assume that is the reason for going with a tube preamp
...yes, it is the reason I am going with the 'tube sound'...

Last edited by TigerScent; 5th December 2011 at 02:34 AM.
  Reply With Quote
Old 5th December 2011, 02:33 AM   #23
diyAudio Member
 
Join Date: Mar 2006
Location: Australia
I have some used 'huge' valves I purchased - taken from a local radio station transmitter - years ago when it was upgraded/demolished...I must revisit them in my shed interstate and find out what they are. Maybe I can make a 'super valve amp' with them... or something...They are quite massive...about 5" long and about 3" wide have some kind of aluminium ring setup around them

Last edited by TigerScent; 5th December 2011 at 02:53 AM.
  Reply With Quote
Old 5th December 2011, 02:47 AM   #24
diyAudio Member
 
Join Date: Mar 2006
Location: Australia
Quote:
Originally Posted by Zaphod Beeblebrox View Post
My point exactly. It always makes sense to start with a known yardstick and move on from there. Once Tigerscent has evaluated the 'standard' he can move onto other ideas and see how they compare. My point to Tigerscent has always been that the matching preamps are plentiful and modestly priced in Australia. He should have little difficulty in borrowing or buying one to try.
...YES...clearly this is a good idea, ...

... you chaps know a great deal more about all this than myself, I have just viewed the tip of the iceberg -from afar- in comparison..., and am trying to understand what is underneath it..., however, know that its there....in one form or another...
  Reply With Quote
Old 5th December 2011, 03:50 AM   #25
ChrisA is offline ChrisA  United States
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by TigerScent View Post
...actually the update on this is that the 550 Type I only has unbalanced inputs @ 1K ohms. (Its the 500 that has balanced ones at 2K...)

...so, <10ohms would be optimal for pre-amp output....
So that does not change much. You are still building a "mini powered" integrated amplifier. Just a standard preamp but with a flea powered power section. You can do it exactly as I said Use an 6SN7 or 12AU7 as the power tube but now one side of the output transformer's secondary is grounded.

Why is it the unbalanced is so common with consumer electronics? I can understand it on low-end gear but but on a $200+ amp it would not add much more cost and it eliminates problems with interconnects.
  Reply With Quote
Old 5th December 2011, 04:05 AM   #26
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by ChrisA View Post
It it's obvious. Use an output transformer in the preamp and use the ME550's balanced inputs. It is impossible for a transformer to produce DC and we all know that transformers are available with 4, 8 or 16 ohm secondaries.
and if you load it with higher impedance, its primary impedance will change to, no?

actually I thought a 600ohm balanced signal trafo qould work into 1kohm
not that I have ever really understood this stuff
  Reply With Quote
Old 5th December 2011, 07:04 AM   #27
ChrisA is offline ChrisA  United States
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by tinitus View Post
and if you load it with higher impedance, its primary impedance will change to, no?

actually I thought a 600ohm balanced signal trafo qould work into 1kohm
not that I have ever really understood this stuff
Yes it would work. 600 is good enough, you really don't need 10. And yes the transformer will reflect back whatever is the actually load. But I gets if you want the tubes to see a constant load you can put a resistor across the secondary. The resistor will add in parallel with the amp and the preamp will see the sum.

I do this across the output transformer of tube power amps. I'll use a 270 or 470 power resistor. The reason is to save the amp in case the speaker is not plugged in or the cable is cut or the voice coil burns up. The 470R is huge compared to the 8R speaker but tiny compared to infinity (infinity is the impedance of a blown voice coil)

Yes, 600 might be a better design goal than 10.

I still can't believe someone build an amp with such a low input impedance. You are right
  Reply With Quote
Old 6th December 2011, 12:05 AM   #28
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by ChrisA View Post
But I gets if you want the tubes to see a constant load you can put a resistor across the secondary. The resistor will add in parallel with the amp and the preamp will see the sum.
ehh, I though two resistor values in paralel would always be less than the smaller one
  Reply With Quote
Old 6th December 2011, 12:51 AM   #29
ChrisA is offline ChrisA  United States
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by tinitus View Post
ehh, I though two resistor values in paralel would always be less than the smaller one
"Add in parallel" was maybe confusing. I should have said "combine in parallel". The load on the output transformer will be one over the sum of the reciprocals.

I like using the load resistor because, As I said, "safety". It allows you to turn on the preamp with nothing plugged in

The other method is just to give up on building an all tube pre-amp and use a solid state output section
  Reply With Quote
Old 6th December 2011, 01:35 AM   #30
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
ah, ok, the 'traditional' 1Mohm ground resistor(safety)
this big it wont lower the load
  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
Best type of pre-amp for valve/tube power amp elgee Tubes / Valves 10 11th November 2011 11:40 AM
any advice on how to match a headphone level output to valve amp input levels? mondogenerator Headphone Systems 1 18th December 2009 04:08 AM
what guideline to match pre and amp? milen007 Tubes / Valves 5 2nd June 2008 06:58 AM
Valve Pre Amp & Class D Power Amp Puffin Tubes / Valves 7 16th June 2006 05:41 PM


New To Site? Need Help?

All times are GMT. The time now is 03:18 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