300B SE with an interstage - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 8th April 2015, 08:17 PM   #1
LOSI is offline LOSI  Germany
diyAudio Member
 
Join Date: Sep 2012
Location: close to Karlsruhe
Default 300B SE with an interstage

Dear all,

looking for a new project with 300B, I thought to build an amp with an IT.
As a driver, I like to use a D3a (strapped to triode).
(I don't want to use the usual 5842 tube. I like to use the IT in 1:1 configuration)

Does anybody have a proven circuit which I can take as basis?
I built once the 6SN7-300B amp. However, I'm not so experienced to create on my own experience this circuit.

I want to use my existing Hammond OPT 1627 SEA.
I'm open to source a more advanced when it is feasible.
(I mentioned in a different thread, I was not impressed about the sound quality of the 6SN7-300B with 1627 SEA; Walton design).
I have as a comparison an Unison Research Sinfonia (KT88 PSE).

Any help from your side is appreciated?

thanks and regards

Dirk
  Reply With Quote
Old 9th April 2015, 12:57 PM   #2
diyAudio Member
 
Join Date: Dec 2010
Location: Napoli
Quote:
Originally Posted by LOSI View Post
Dear all,

looking for a new project with 300B, I thought to build an amp with an IT.
As a driver, I like to use a D3a (strapped to triode).
(I don't want to use the usual 5842 tube. I like to use the IT in 1:1 configuration)

Does anybody have a proven circuit which I can take as basis?
I built once the 6SN7-300B amp. However, I'm not so experienced to create on my own experience this circuit.

I want to use my existing Hammond OPT 1627 SEA.
I'm open to source a more advanced when it is feasible.
(I mentioned in a different thread, I was not impressed about the sound quality of the 6SN7-300B with 1627 SEA; Walton design).
I have as a comparison an Unison Research Sinfonia (KT88 PSE).

Any help from your side is appreciated?

thanks and regards

Dirk
Ii my experience D3A is an excellent driver tube on paper but have some irregular harmonic distortion decay.
If you do not have problems in sourcing them, E810F could be a better choice.
THD spectrum is usually much more regular and the sound more natural.
Also they have an even lower internal impedance that will make easier to find a good IT for them.
__________________
People always do what they do for what they think is a good reason. Listen to other people's experiences, understand their reasons, treasure them! Then add your own. Try to do better. This will bring you to amazingly good results, in an amazingly short time.
  Reply With Quote
Old 9th April 2015, 02:00 PM   #3
euro21 is offline euro21  Hungary
diyAudio Member
 
Join Date: Sep 2004
Location: Budapest
Quote:
Originally Posted by CiroMarzio View Post
Ii my experience D3A is an excellent driver tube on paper but have some irregular harmonic distortion decay.
I have opposite experience.
D3a, LED bias, 10mA CCS, 70V RMS out.
Attached Images
File Type: jpg D3a driver 70VRMS_Left.jpg (169.1 KB, 683 views)
  Reply With Quote
Old 9th April 2015, 03:44 PM   #4
diyAudio Member
 
Join Date: Dec 2010
Location: Napoli
5th, 7th, and 9th harmonic have an excessive level compared to 4th, 6th and 8th.
E810F triode strapped does not suffer from this problem.

But this I discovered a little too late, after buying several dozens D3A...
anybody loving D3A wants to buy some at a bargain price?
__________________
People always do what they do for what they think is a good reason. Listen to other people's experiences, understand their reasons, treasure them! Then add your own. Try to do better. This will bring you to amazingly good results, in an amazingly short time.
  Reply With Quote
Old 9th April 2015, 03:56 PM   #5
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
GoatGuy's Avatar
 
Join Date: Dec 2012
Location: SF Bay Area
Quote:
Originally Posted by CiroMarzio View Post
5th, 7th, and 9th harmonic have an excessive level compared to 4th, 6th and 8th.
E810F triode strapped does not suffer from this problem.

But this I discovered a little too late, after buying several dozens D3A…
anybody loving D3A wants to buy some at a bargain price?
You're funny! The 5th is [(93 - 22) = –71 dB] lower than fundamental. This would be inaudible even with sine waves, let alone program music content. The 7th and 9th are even lower.

Do try to recognize the difference between an observation and a result, dear CiroMarzio. The 300B is an outstanding tube to build upon. Magnificent.

GoatGuy
__________________
John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink
  Reply With Quote
Old 9th April 2015, 04:07 PM   #6
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
GoatGuy's Avatar
 
Join Date: Dec 2012
Location: SF Bay Area
Dirk (LOSI),

In the optics world, lenses have a problem called “aberration”. The worst is chromatic (red and blue refracting different amounts through curved lenses), but there are other forms too. Optical engineers "deal with it" by two main techniques. First is, using more elements, so that the bending done by any given element is less than with fewer elements. Second is, pairing up elements so one partially (or mostly) compensates for the other's chromatic aberration behavior. They're called doublets and triplets.

I bring this up because the same techniques can be applied to high fidelity amplifiers to control and clean up the nonlinear shortcomings of valves in real world operation. The analogy of “use more elements” would be “use more stages”. The analogy of “bend light less” would be “of lower gain per stage”. The analogy for “doublets and triplets” to compensate refraction issues would be “use better biasing and current sourcing techniques”.

So, there you have a basic outline of a design criteria list!

• More, lower gain stages.
• Better biasing.
• Symmetric compensation

One might be tempted to go all faddish-purist, and have a no-capacitor ("direct coupled") amplifier, but this is a bit overblown. Real-world amplifiers with quality components, rightly sized and specified rarely have any audible aberrations based on the DC blocking capacitors influence. But it might be one of your cherished ideals, so if so… include that too.

Anyway, I just wanted to point out the above, in the hopes that if you “get it”, that it will influence the design you choose (or create!).

Have fun! And don't forget to build a really decent power supply for triode mode amplifiers.

GoatGuy
__________________
John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink
  Reply With Quote
Old 9th April 2015, 04:40 PM   #7
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire
Blog Entries: 2
Quote:
Originally Posted by CiroMarzio View Post
...after buying several dozens D3A...
anybody loving D3A wants to buy some at a bargain price?
Did you try the 6E5P (triode wired) ? - I heard it driving a 6C4C once, and compared it with a 6C45P driving same output tube. The 6C45P was very clean, perhaps too 'solid state' sounding for some people. The 6E5P was smooth sounding.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 9th April 2015, 05:09 PM   #8
sjs is offline sjs  United Kingdom
diyAudio Member
 
Join Date: Oct 2011
Location: Manchester
this circuit was successfully built by a number of people, most frequently as a pair of mono block amps

Click the image to open in full size.

You can replace the 417A / 437A with a triode D3a, EC8010, 6C45PI or triode E55L if you wish.

For 1:1 IT you could try the inexpensive Hammond 126B, or similar 1:1 offerings from SP Wound Components, Audio Note UK, Hashimoto, Monolithic Magnetics or Noguchi depending upon the depth of your pockets. I would suggest 1:1 bifilar wound are the way to go.

Nowadays I would definitely use Rod Coleman boards for the 5V filament supplies to the 300B! and be tempted to use SiC diode bias on the input tube

Best of luck

Last edited by sjs; 9th April 2015 at 05:11 PM.
  Reply With Quote
Old 9th April 2015, 05:33 PM   #9
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
GoatGuy's Avatar
 
Join Date: Dec 2012
Location: SF Bay Area
SJS: your B- supply circuit is wrong. As shown, it will produce positive voltage, not negative bias voltage. Nice idea though. Pretty complicated transformer.

The chief disadvantage of having [rectifier → choke → capacitor ] power supply stages is that they waste a fair fraction of the transformer's secondary potential. It would be much better to include a 10 μF to 20 μF capacitor before each of the choke stages to act as a "topping up reservoir". Amazing how much more voltage you get.

Let's see. Its also not clear why you're burning up power with that 12 kΩ/20 watt resistor. If it is to drop voltage to 375, I really can't see the point. It certainly isn't to improve the ripple suppression of the choke. Just seems like a room heater, to me.

Same goes for the 15 kΩ, 5 watt resistor burning power on the A+ supply.

The use of a 2,200 μF cap as a cathode-bias-bypass … is about 10× greater than really necessary, but since they're inexpensive parts … why not. Seems OK.

You could have had a 1:2 or 1:4 interstage transformer between the stages, with little (nil) negative effect. Kind of like "free gain". One of the sweet things that transformers are willing to do for free for us. To not take advantage of it is like not using a free airplane ticket.

The rest seems fine. I'm not sure whether I'd be sticking a rheostat on the filament pins of the 300B. Rheostats are notorious for becoming noisy, even when not periodically wiped.

GoatGuy

ADDENDUM: Indeed… if the goal is to produce a magnificently beautiful chassis AND burn watts (which is what your 3-rectifier plus room heater approach affords), you might as well toss in a few 6CA7s, 3 or 4 voltage regulator tube (0A3, etc) and build up a nice series-cathode-follower regulated multi-volt power supply. Seriously! The gas regulators make the prettiest glow, and with some fiddling, you can get a QUITE stable (and QUIET) set of anode supplies going. Heck.. the regulation is so good with the 6CA7 that you might as well go "stereo" instead of mono block (as drawn). They've (6CA7) got plenty of gumbo in the milliamp and plate dissipation departments.

Let's see. 2 of the 6CA7s. Drop the room heater resistors. 2 0D3 (150 volt) regulator tubes plus 1 0A3 (75 volts) gives 375. The 190 can be wrought with a pair of 0B3's (90 volts each). And, to think! each type is a different color! 7 more tubes in the power supply. 2 more tubes for the LEFT channel. 2 more transformers. Paint it all metallic-greeeeeeeen

GoatGuy
__________________
John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink

Last edited by GoatGuy; 9th April 2015 at 05:45 PM. Reason: subsequent thoughts, renewed
  Reply With Quote
Old 9th April 2015, 05:48 PM   #10
sjs is offline sjs  United Kingdom
diyAudio Member
 
Join Date: Oct 2011
Location: Manchester
Quote:
Originally Posted by GoatGuy View Post
SJS: your B- supply circuit is wrong. As shown, it will produce positive voltage, not negative bias voltage. Nice idea though. Pretty complicated transformer.

The chief disadvantage of having [rectifier → choke → capacitor ] power supply stages is that they waste a fair fraction of the transformer's secondary potential. It would be much better to include a 10 μF to 20 μF capacitor before each of the choke stages to act as a "topping up reservoir". Amazing how much more voltage you get.

Let's see. Its also not clear why you're burning up power with that 12 kΩ/20 watt resistor. If it is to drop voltage to 375, I really can't see the point. It certainly isn't to improve the ripple suppression of the choke. Just seems like a room heater, to me.

Same goes for the 15 kΩ, 5 watt resistor burning power on the A+ supply.

The use of a 2,200 μF cap as a cathode-bias-bypass … is about 10× greater than really necessary, but since they're inexpensive parts … why not. Seems OK.

You could have had a 1:2 or 1:4 interstage transformer between the stages, with little (nil) negative effect. Kind of like "free gain". One of the sweet things that transformers are willing to do for free for us. To not take advantage of it is like not using a free airplane ticket.

The rest seems fine. I'm not sure whether I'd be sticking a rheostat on the filament pins of the 300B. Rheostats are notorious for becoming noisy, even when not periodically wiped.

GoatGuy
Nice critique, it's a shame you have never built or listened to such a circuit, as all would become clear.

The B- supply is not wrong, it does give negative rail, I have built 10s of them over the years - go try it

Choke input power supplies go much easier on the mains tx and sound way better, the inclusion of an input cap makes it sound like every other flabby SE amp, so it is not of interest. It is not "much better" with an input cap, it sounds significantly worse. Why bring up "efficiency" a total red hering is SE valve power amp is the purpose, you want efficiency? go build a Class D amp.

The shunt resistors are to provide min current through the choke, always a good idea with a choke input psu imho

I had a pile of 2,200uF 6.3V black gates at the time, hence the design. I have said in my post that I would probably use a diode if doing it today.

The point of a 1:1 bifilar IT is you can get sub 10Hz to >100kHz bandwidth, it is the only sensible option which cannot be achieved with 1:2 or 1:3 or 1:4 options, so it is not "free gain" as you restrict bandwidth and often introduce ringing, if you have ever heard a 1:1 bifilar compared to a 1:2 or 1:4 IT then you would know why

Using the pot on the 300B filament? apart from again stating I would use Rod Coleman supplies if done today, therefore the pot would vanish, I have examples built more than 20 years ago using good 2W wirewound pots which have not gone noisy.

The OP asked for a proven circuit, rather than un-proven conjecture. I have built several versions of this amp, as have more than 10 DIYs I am personally aware of since it was first published 18 years ago.

best of luck

UPDATE

And Series Regulators sound truly awful, please don't suggest that again!

Now, a really good Shunt Regulator, maybe using 300Bs as the pass tube? You could get me interested in that..... see John Camilles 211 Shunt Reg for his 211 SE amp in Sound Practices back in the day

Last edited by sjs; 9th April 2015 at 05:53 PM.
  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
Optimum driver valve for an interstage-transformer-driven SE 300B needsp Tubes / Valves 19 6th May 2012 09:57 PM
300B with interstage summilux Tubes / Valves 4 5th April 2011 09:51 PM
SJS SE 300B with Interstage Transformer Mk2 DVDHack Tubes / Valves 29 20th August 2008 12:52 PM
Interstage Couple 300B 811-3 SE amp tube-lover Tubes / Valves 0 12th November 2007 01:47 PM
Groups Buy for Supermicro Crystalline OPT 300B SE amp with Interstage driver stage. tube-lover Group Buys 0 5th February 2006 04:36 AM


New To Site? Need Help?

All times are GMT. The time now is 07:32 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright ©1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki