Help, I need your advice - What Next? - 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 11th May 2008, 11:29 AM   #1
diyAudio Member
 
Rob11966's Avatar
 
Join Date: Jun 2007
Location: Australia
Default Help, I need your advice - What Next?

Hi Folks,

I realise that I may be opening a can of worms here but...

I am looking for ideas for my next project. I have completed both a KT88 and EL34 PP amp. I am extremely pleased with both but I am itchy for a new project.

I am looking to build something really special and I understand that this is largely in the eye/ear of the beholder but I need some input from the members of this forum.

OK, lets pretend that money is no option (it is but lets pretend). My only requirements are as follows -

1. Output tubes different from above (ie no EL34 or KT88)
2. At least 8-10w (or at least something suitable for speakers of 90db sensitivity)
3. No kits
4. Voltages < 600v

I am keen for as little or much advice as you can give especially with regards to specific schematics - I can see myself heading down the 300b road but maybe there is something better out there! I am not looking for a quick or easy project - this one needs to be a killer amp (well, not literally hence the voltage restriction but you know what I mean)

Once again I appreciate the huge scope of the question; perhaps I could rephrase it - with regards to the above criterion, what would you build?

Cheers,

Rob

PS Please find attached a picture of my KT88 at night
Attached Images
File Type: jpg dsc_0017a.jpg (86.4 KB, 544 views)
  Reply With Quote
Old 11th May 2008, 01:35 PM   #2
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Paul Joppa's 102 dB. rule indicates that 15+ WPC are appropriate for your speakers. A 7591 based "El Cheapo Grande" satisfies both PJ's and your criteria. An ECG produces approx. 30 WPC in UL mode and 15 WPC in triode mode.

I'll try to EMail the lower powered "El Cheapo" schematic to you. Circuitry that drives "12" W. multi-grid power O/P tubes also drives the 7591. "El Cheapo Grande" uses the same 12AT7 based splitter/driver that EC uses.
__________________
Eli D.
  Reply With Quote
Old 11th May 2008, 01:38 PM   #3
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
I'd go for something triode, single ended, and directly heated cathode. Mostly because you said you're looking for something new or different, and the two amplifiers you've already built are pentode (or beam tetrode), push-pull, and indirectly heated.
  Reply With Quote
Old 11th May 2008, 01:47 PM   #4
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally posted by Ty_Bower
I'd go for something triode, single ended, and directly heated cathode. Mostly because you said you're looking for something new or different, and the two amplifiers you've already built are pentode (or beam tetrode), push-pull, and indirectly heated.

Unfortunately, cost and/or rail voltage considerations rule that, otherwise, reasonable suggestion out. Higher powered variations on the 300B theme are costly. Rail voltage requirements make using the much more affordable 845 problematic. Phooey!
__________________
Eli D.
  Reply With Quote
Old 11th May 2008, 06:31 PM   #5
tim845 is offline tim845  Hong Kong
diyAudio Member
 
Join Date: May 2004
Location: hk
Go with 845 single ended, using 5687 cap. couple to KT88, then use interstage to drive 845, under this config., you would not regret.

Don't be afraid of the high tension for 845, there is only 2 wiring points must take high attention - the long cable from the cap filter to the output HT and the cable from the "P" pin of the output to the 845 socket.

Carefully to treat this in safe, then nothing should be afraid of !!!

Of course, the high voltage section should be arranged as closer as possible and in a result the wiring can be made as short as possible within the area of the high voltage section, this will avoid the chance of electric shock !!!

Believe me, follow this wiring arrangement your machine should be running for years in safe !!! I am dare to claim that it sounds excellent to you and better than 300B, no matter the punching or textures.

As you mentioned, money for nothing, the output and the interstage you have to use well known brand or reliable one, such as Tamura, Audio Note, Lundhal or its like, because any iron participates in a tube amp. plays a very very important role and the rule of "money is no option" must be obeyed for the quality of iron !!!

I do not quite agree that it should use excellent schematic design and the irons only need to play a proper role is ok. Tube amp is not a rocket science, complicated excellent schematic will not make things easier and understandable, it just make things complicated further and discourage a diyer, that's what I think.

If you don't like the tenant - KT88 living in your house, try KT66 or even 300B as the driver tube. But I don't think 300B is a good choice because it is a waste !!!

Also, it will give you about 20W something for the output power and it is not a big number in terms of output rating. Because you just use one to two watts to drive your sensitive loudspeakers in general listening range and under this range, the 845 can give you a very little distorted sound. Absolutely better than 300B if under same listening level, at least more un-distorted and realistic low bass punch can be reproduced.

Try it and you will find it is worth to try it and own it.
  Reply With Quote
Old 11th May 2008, 06:44 PM   #6
diyAudio Member
 
Join Date: Jan 2007
Location: Iowa
What is your budget? The 300B's themselves can be a bit pricey but other than that the costs aren't to bad. If you need the increased power you could do a Parallel SE or Push/Pull 300B. Stick something fun in front for a driver and drive the back end with an interstage transformers.

http://www.audiodesignguide.com/my/sep_mk2.gif

Example (^); most of your cost is going to be in iron and tubes....like all things. The 417A/5842 from Raytheon can be found for $20-$30 USD, a matched pair of 300B's, the same ones I am looking at for my build, are $175USD for EH Gold Grids. The interstage would be costly though, you want to use a high quality unit here, no skimping. As for the B+, it is under 600v at 380v. Most simple 300B designs that I have come across use 350v to 425v or so, only a few use up to 700v, Electra-Print DRD 300B SE for example. The JE Labs 300B SE would be a simple and cheap implementation to get a bit of 300B taste. That is the design I considered but since starting a thread here on my build I have decided otherwise.

Another option that could be done on the cheap. Buy some 12HG7's, they are great drivers when pentode wired or triode wired, and they can be found cheaply. Couple it to a 300B and you would have a great little amp. You could simple wire it up as a triode or you could use the pentode option and make a 91A type amplifier. You could even do something fun with it like choke load, DRD, or interstage drive. For the cost of a single WE 417, or even a Raytheon, you could get a small handful of 12HG7's.

Why not take something like a power pentode like the KT88 (sorry) and make a SE amp. To try something different you could use 807's (beware of plate cap). These can still be found fairly cheaply even as NOS. I have about 16 807 that I am planning projects for, all NOS, I love 807's. There is just something about the seductive coke bottle ST shape with a cap on top, and they glow heavenly. Although they don't glow quite as heavenly as a GM70. Parallel 6L6's could do the trick, or do a 6C33C SE. You could take a KT88, 6L6, 807, etc... and set it up for triode operation with a switch so you can switch it back to UL operation if you need to or want to. You can get a quasi taste of SET sound without paying for the classic SET tubes like the 300B, 50, and 2A3.

http://diyaudioprojects.com/Tubes/KT88/index.htm

The above is just an option to consider. You could look at the 813 (directly heated pentode) also, it likes 900v+ but you can get by right at your 600v maximum. With a full 900v or more though you can get 20watts or more in triode mode and almost 50watts in UL. Beware though, this beast has a plate cap, not good for kids, pets, and wandering fingers .

Cheers

James
  Reply With Quote
Old 11th May 2008, 07:09 PM   #7
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
Here's a special one. It meets all your stated criteria, and you won't find any of these on your block. A lot going on under the hood - would be a real learning experience: http://www.intactaudio.com/forum/viewtopic.php?t=549

Sheldon
  Reply With Quote
Old 11th May 2008, 07:23 PM   #8
diyAudio Member
 
Join Date: Jan 2007
Location: Iowa
Holy triodes Batman! That is a beautiful looking boat anchor! It would with out a doubt be a learning experience.

Cheers

James
  Reply With Quote
Old 11th May 2008, 08:31 PM   #9
diyAudio Member
 
Join Date: Jun 2004
Location: Indiana
How about parallel (or accordian) SE DHT using some of the less glamorous bulbs. What is that one that is a 6V heater 2A3? 6A5 I think. Add transformer coupling and you have something quite different that what you have done.

Or do something other than a power amp like a tuner, phono preamp, mixing board etc. Just thinking outside the box.

mike
  Reply With Quote
Old 11th May 2008, 10:02 PM   #10
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
Quote:
Originally posted by JPeitzman
Holy triodes Batman! That is a beautiful looking boat anchor! It would with out a doubt be a learning experience.

Cheers

James
I enjoy the way he thinks. I've built a couple of projects based on his designs and have been pleased with the outcome. If I were looking for 45 of sweet pp power, I'd build this one. Relatively efficient for that power level too. I don't know much about building the controller, but everyone of us probably has a friend that does.

Sheldon
  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
first amp advice prezden Class D 2 18th November 2008 10:05 PM
TT advice??? geordie Analogue Source 2 30th September 2007 04:04 PM
Advice for an amp wyomoose Subwoofers 1 12th February 2007 08:07 PM
New to DIY, looking for advice flubhubber Multi-Way 1 14th November 2005 03:48 PM
Poster in Musical Instrument forum needs bridging advice on BrianGT 4780 advice moving_electron Chip Amps 0 16th February 2005 12:37 AM


New To Site? Need Help?

All times are GMT. The time now is 10:54 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