Looking for Tube Amp Kit Recommendations - 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 14th April 2012, 12:36 PM   #21
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by Bismar View Post
Hi thanks for your advice, but i believe the speakers your recommending are large floor standing speakers. I am looking for small bookshelf speakers instead.
On that topic, I saw the weirdest thing ever. Somebody had set bookshelf speakers up on plant stands--effectively cutting off cabinet space that could have been used for quality bass. Why does better marketing usually result in lesser quality?
  Reply With Quote
Old 14th April 2012, 12:49 PM   #22
roline is offline roline  United States
diyAudio Member
 
roline's Avatar
 
Join Date: Sep 2010
Location: East Tennessee
I have debunked the theory that Teflon silver caps have to be used in the signal path of tube amps to sound great.... Tube amps can be made on a budget that sound great! It is more than just the components, it is the design electrically as well as physical layout.
It is more than just "Tube amp", it is what topology of tube amp......
One of the advantages of "PP triode connected output tube amps" is the fact that the speakers are connected through the transformers to the tubes. The speakers impedance is directly reflected to the output tubes so as the impedance goes up, the output gain goes up also. SO why is that a big deal? With solid state the output impedance is very low and the amp does not care about speaker impedance. When the impedance increases, the output power is decreased P=V^2/R. If the gain of the output section is a reflection of the speaker impedance the gain goes up compensating for the change in impedance. Don't take my word for it, do an A B comparison for yourself.
__________________
SO many tubes, SO little time!!!
  Reply With Quote
Old 14th April 2012, 12:58 PM   #23
kevinh is offline kevinh  United States
diyAudio Member
 
Join Date: May 2007
K & K has a nice kit for the ST70 (you provide a used ST70) for <$300 USD.

details here:

K & K Audio - Lundahl Transformers, audio DIY kits and more
  Reply With Quote
Old 14th April 2012, 01:08 PM   #24
Banned
 
Join Date: Apr 2012
The Bob Latino ST70 's seem to be popular.

You don't need a "kit" per say, you can order transformers and fill in the blanks for the rest of the parts. That will give you more choice and flexibility on the final project.

You can build a juicy tube amp for $500.

Get the iron from Hammond or Edcor, purchase resistors and capacitors in "kits", you will save money had have parts left over for other builds or changes.
  Reply With Quote
Old 14th April 2012, 03:05 PM   #25
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by roline View Post
. . . The speakers impedance is directly reflected to the output tubes so as the impedance goes up, the output gain goes up also. SO why is that a big deal? With solid state the output impedance is very low and the amp does not care about speaker impedance. When the impedance increases, the output power is decreased P=V^2/R. If the gain of the output section is a reflection of the speaker impedance the gain goes up compensating for the change in impedance. Don't take my word for it, do an A B comparison for yourself.
I hope it isn't offensive that my Parallel LM1875 has a dial for that feature that took only 8 minutes to install and the whole thing cost only $34.
  Reply With Quote
Old 14th April 2012, 06:40 PM   #26
rmyauck is offline rmyauck  Canada
diyAudio Member
 
Join Date: Apr 2009
Bismar,

Those Mark III's you would need 2 so costs would add up. Maybe find used over there with good transformers for rebuilding.

Are you handy with tools, and working with metal and wood, as that could save you money by building your own chassis and speaker cabinets?

Can you get Hammond transformers over there for affordable prices, or do you have to ship from the US?

If so get some Hammond (12 lbs. ea so need to make a sturdy base/ chassis for these) 1650R OPT's as they can be had for $105 in the US. With a 100W rating and 5K input they will give you a great bandwidth (Frequency response range in the power range you would use, which is less than half the 100W rating)

One AnteK Toroid 325-0-325 PS trans for $40 as you could use SS diodes to save $ and have great solid bass. Just use ICL's (Inrush current limiters) to help the tubes, caps etc last. $10

PS cap board & kit $77 ( may save by wiring caps on perfboard etc.)

Pick one of the affordable Driver boards of your choice for ST-70. You can get them with a kit of parts for about $100.

All the above are wired up per std ST-70 schematics along with instructions from board kits

Other parts like the 4 Octal 8 pin tube sockets, RCA inputs and speaker terminals , wire etc. Maybe $50. Might be able to add a volume control for $10-20 but a nice line stage preamp may be better and could actually be added to your homemade chassis for say another maybe $50 if you use the amps PS.

For Phono you would have to build or buy a suitable preamp.

Base-chassis could be built for maybe $50 or less if you get scrap materials to build with.

Tubes if you start with affordable EL34/6CA7 /KT-77 or 6LGC/KT-66 types could cost you $100-120

Maybe as low as $650 plus shipping if you want 35-40 W/CH to start and KT-88's could be rolled in later for a different sound and 50W/CH.

For an upgrade add an Edcor 2H low DCR (18-21 ohms) choke with 300-400 mA capacity @ $31-37

Should work with and sound fantastic with a wide range of new and used speakers out there.

Randy

Last edited by rmyauck; 14th April 2012 at 06:51 PM.
  Reply With Quote
Old 14th April 2012, 10:03 PM   #27
roline is offline roline  United States
diyAudio Member
 
roline's Avatar
 
Join Date: Sep 2010
Location: East Tennessee
Quote:
Originally Posted by danielwritesbac View Post
I hope it isn't offensive that my Parallel LM1875 has a dial for that feature that took only 8 minutes to install and the whole thing cost only $34.
Current feedback is not used in mainstream products mainly due to being more sensitive to the speaker and room dynamics being part of the feedback loop. You are correct that accomplished by a different method, a similar result for improved sonic performance. More than one way to skin a cat...

Current feed back in solid state amps does have some limitations, "The principal advantages of current drive are seen to be an elimination of performance dependence on voice coil resistance ( which is thermally modulated) and also coil -inductive effects, which give rise to high frequency distortion, along with nonlinear electo-magnetic damping due to BL variations. The technique is similarly insensitive to the lumped series elements of the amplifier-loudspeaker interconnect. However, it is often necessary to lower the system Q caused by the loss of amplifier generated dampening, either by open loop compensation, by special drive-unit design, or by motional feedback, where the latter is regarded as the optimal method at low frequencies."
from Distortion Reduction in Moving -Coil Loudspeakers Systems Using Current Driver Technology, Mills and Hawksford 1989

In a tube amp it just a matter of reflected speaker impedance through the transformer on the output tubes......
No special feed back loops, no real change to dampening, however global negative can be used to lower the distortion.
__________________
SO many tubes, SO little time!!!

Last edited by roline; 14th April 2012 at 10:07 PM.
  Reply With Quote
Old 15th April 2012, 01:21 AM   #28
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally Posted by Bismar View Post
Eli Duttman, i take it theres no kits for the El Cheapo?

Also found the speaker impedance curve for the original firesprite i linked.

SB Acoustics :: 6" SB17NRXC35-8

Seems pretty flat.
Jim McShane sells parts kits for "El Cheapo" builds. The builder supplies "iron" and case work.

That's a frequency response plot for a bass/midrange driver. The impedance curve will reflect both the drivers and the crossover used.
__________________
Eli D.
  Reply With Quote
Old 15th April 2012, 01:37 AM   #29
diyAudio Member
 
danielwritesbac's Avatar
 
Join Date: Nov 2007
Quote:
Originally Posted by roline View Post
. . . In a tube amp it just a matter of reflected speaker impedance through the transformer on the output tubes......
No special feed back loops, no real change to dampening, however global negative can be used to lower the distortion.
Just now I imagined: LM675 non-inverted, set to very low gain, with 47k to 100k feedback resistor for no current noise, run from reg/capmulti power, and enclosed into global negative feedback with a tube so as to override the solid state sound. A similar prospect can be done with TDA7293 by shorting the inputs to create a unity stable fet buffer with enough power to drive inefficient speakers. The low loss outputs of these two hybrid prospects is especially good for driving ported bookshelf speakers.

My opinion on Hybrid amplifiers: There isn't a circuit more cost efficient than the triode if one wants a tube amp sound. Fully solid state circuits can do it, but a totally effective tube emulation is several complex dodges stacked and instead of finding one tube, there are scads of little bits to find, which can be expensive, and energy consumption of such devices is usually inferior to the triode. Therefore, I do believe that any sensible tube hybrid amp will contain small signal triodes. All of the other matters are all adjustable (at either amp or speaker) or at least less complex.

Last edited by danielwritesbac; 15th April 2012 at 01:41 AM.
  Reply With Quote
Old 15th April 2012, 07:06 AM   #30
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
Sorry I am posting in a hurry, but the OP flag says he is from Australia. Suggestions about power supplies, transformers an shipping need to be considered. That is 240 volt mains and very expensive shipping for transformers and speaker drivers.

For OP, if you can get speakers that are 3dB more sensitive (92 dB), then you can get away with half the amplifier power. Tube amps of 10-14 watts are great for a beginner. Getting 30 watts becomes more expensive and complex (but still achievable). I think if you can get a few dB more sensitive speakers, the 10-14 watt options mentioned are all great.

Trouble with speakers is trying to get more than two of the four parameters (small, cheap, efficient, bass extension).

Good luck with the project, plenty of helpful people on this forum who will be willing to assist you!

Chris
  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
Tube amp kit and speaker recommendations? mrcandyman Tubes / Valves 19 23rd December 2011 03:41 PM
Recommendations for a valve amp kit Fivetide Tubes / Valves 13 6th August 2011 12:43 AM
power amp kit recommendations keungfai Tubes / Valves 11 17th August 2006 01:22 PM
Amp kit recommendations DaveCan Tubes / Valves 22 2nd August 2006 12:32 PM
1st amp (and preamp) kit recommendations ? greg7 Solid State 1 20th April 2003 12:56 AM


New To Site? Need Help?

All times are GMT. The time now is 03:22 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