[David Ellis]

I thought any Dynaco would be a good place to start my own learning.

I agree completely  !!   This amplifier will be a GREAT place to start learning about amplifiers.  It perhaps slightly easier with non-pcb valve amps, but having a schematic will help dramatically.  I have spent hours with looking at the bottom of my amplifiers with the schematic immediately adjacent while studying my valve amplifier books.  I am not an amplifier wizard, but find the study of relatively simple valve circuits quite fascinating.  However, when things get complex I lose track of the electrons mentally. 

A snippet - Valve amps without slow turn on circuitry or a tube rectifier will eat tubes faster.  Tube amps with slow turn on circuitry or a tube rectifier will have extended tube life.  There are a few other variables, but the most important is having a gentle application of primary power after the heaters are warm.

Dave

[27ph]

I tried a SKA (simple killer amp), slighty modified with a massive psu yesterday. It was beautiful.

vH pH

[David Ellis]

I tried a SKA (simple killer amp), slightly modified with a massive psu yesterday. It was beautiful.

Groovy!  Thanks for the contribution!

Do you have a link?

What other amplifiers did you replace?

Dave

[David Ellis]

I have something to add to this string.

A while ago I decided to experiment in something different.  i purchased a Cary 572SE MKII and a friend allowed me to borrow his CARY SLP 50 Preamp.  The amplifier is a 20wpc SET design.  It has enough juice to drive the 1801b to a reasonable level in my living room.

Before mods this setup sounded very MEDIOCRE.  There were some good things about it, but the sound was somewhat colored, the bass was very lean, and the midrange was gritty.  I suspect this amplifier is on par with many commercial offerings that has potential with a few modifications.  I have been spoiled by having a very good amplifer in my living room and experiencing better DIY amplifiers previously.

After a few mods the sound is markedly better, but the highs remain a bit zingy, the bass remains lean.  The detail is strikingly good, but the amp has "no" bottom end.  If I actually achieve decent results with this amplifier I will post my full comments. 

Dave

[bluesky]

Hi Dave

Here is the link to Greg Ball's SKA website:

http://www.diyhifi.org/amplifierguru/guru_002.htm

Greg lives just a track a bit from me here in Queensland.

Bluesky

[lakerblue]

Happy New Year guys,I am prepare to DIY a PASS ALEPH Mini AMP to replace my old QUAD405 AMP,the PASS has a A type output of 28wpc/8 oms,anyone who can give me suggestions whether it will working well with the 1801s?

[David Ellis]

Happy New Year guys,I am prepare to DIY a PASS ALEPH Mini AMP to replace my old QUAD405 AMP,the PASS has a A type output of 28wpc/8 oms,anyone who can give me suggestions whether it will working well with the 1801s?

 

I don't recall anyone using that specific amplifier with the 1801s, but i do have 2 thoughts.

 - A somewhat wealthy fellow DIY enthusiast who also uses SEAS magnesium drivers went through many rather expensive amplifiers and recalled that the Aleph was perhaps the best of the bunch - including a few Jeff Rowland amps. 

- My Cary 572 SET has plenty of juice for normal to modestly loud listening levels, but it's 20wpc is about the least amount of juice that I'd recommend.  It has 20wpc.

Hopefully these data points are helpful.

Oh, it has been a few years since I looked at the design for the Aleph, but I recall it being a relative simple design.  Don't skimp in the coupling capacitors. 

//

I found this site, and it conveyed the Aleph Mini has 10wpc, not the 28wpc you mention??  Are you sure that you have the specs for the correct project?

http://diyamps.com/aleph/aleph.shtml

Dave

[lakerblue]

I hesitate at the ALEPH after some gentle told me that the quad405 may have a more balanced sound than the ALEPH MINI,I am waiting for audition before a decision,also,the fact is the AM consume more power

Please check this:http://www.hifizone.net/shop_view.asp?id=976 indeed It has a 28wpc output,I think it is reasonable because it has  +/-18vdc rails,not +/-15vdc

I do not think there are any coupling capacitors in the original AM,but can add one if some colored-sound is wanted,Please check :http://www.hifizone.net/forum_view.asp?forum_id=14&view_id=1324
Hey Dave,have you sold out all your 1801b kits?My money is still on the way

[David Ellis]

Strangely, I couldn't load either of those links at hifizone??  Perhaps a membership is required to view them.

If there are no coupling capacitors in the design, adding them would be a very bad idea.

It wouldn't seem that bumping the line voltage by 3vdc would raise the output from 12wpc to 28wpc.  I am not an expert, but this doesn't seem correct.

Hey Dave,have you sold out all your 1801b kits?My money is still on the way

I have 3 W18 drivers remaining.

I don't know I mentioned this previously, but SEAS changed the W18 driver quite dramatically.  The new one has a completely different surround and the shape of the response above 2500hz reflects this.  The new driver also has more inductance (this is bad).  The most important part in all of this is the crossover for the 1801 would have to be completely redesigned to accommodate the changes in the new W18 driver.  Having already endured a few minor changes in the W18 driver I am unwilling to continue in this stead.

The scarlet lining in these problems is the Accuton C95 driver.  It's better.  If the W18 driver remained constant, I wouldn't have discovered this.

After the 1801C is finished, I should be able to manage a less expensive project in 6-12 months.

Dave

[Rocket]

Hi Dave,

Do you have an estimated timeline when the 1801c speaker will be completed and ready for shipping?

Thanks

Rod

[David Ellis]

Do you have an estimated timeline when the 1801c speaker will be completed and ready for shipping?

My prototype pair are already complete, but I want to evaluate a few minor crossover changes before a final stamp of approval.  I should have these evaluated by the end of this month.  There are a couple parallel inductors that I may have custom wound to eliminate a few resistors.  But this is minor in the grande scheme of things.

Dave

[lakerblue]

[lakerblue]

can the pictures been saw?

[David Ellis]

can the pictures been seen?

Yep, I have them.

That's a very sharp looking amplifier!

I was also able to load the other pages you mentioned below - today.  I don't know why I couldn't load them earlier.  Unfortunately, the text on the pages is unreadable.??

Perhaps the 18v dc rails AND the use of a very low impedance loudspeaker (3-4 ohms) make 28wpc available ??  This is only a guess.  And, such a configuration may overload the output transistors.

Dave

[smithy666]

Hi Dave
Happy New Year to you. It's been a while since I posted, but here is a montage of my system. Rebuilt 2 x Stochino amps with handmade anodised aluminium cases and my 1801s. Still working on phase 2, which is adding the SS23W subwoofer to the system, to be integrated through a Borbely 24dB filter and leaning towards one of Anthony Holton's 400W modules (www.aussieamplifiers.com) to power it. Hopefully I'll have this up and running in the next few months and can report back...where is time going??

[lakerblue]

Do you have an estimated timeline when the 1801c speaker will be completed and ready for shipping?

My prototype pair are already complete, but I want to evaluate a few minor crossover changes before a final stamp of approval.  I should have these evaluated by the end of this month.  There are a couple parallel inductors that I may have custom wound to eliminate a few resistors.  But this is minor in the grande scheme of things.

Dave

Hi Dave
I checked the T/S parameters of the two woofers,I found the ACCUTON has higher sensitivity than the SEAS,but the ACCUTON has a heavier moving mass by 2g,also higher voice coil inductance,is that means the 1801c need a more powerful amp to handle with?if so,what is your recommend wpc-output for the amp to work well with 1801c?

[David Ellis]

Hi Dave
I checked the T/S parameters of the two woofers,I found the ACCUTON has higher sensitivity than the SEAS,but the ACCUTON has a heavier moving mass by 2g,also higher voice coil inductance,is that means the 1801c need a more powerful amp to handle with?if so,what is your recommend wpc-output for the amp to work well with 1801c?
 

My amplifier reccommendations remain unchanged.

And, within reason, voice coil inductance will have absolutely no impact on real-world amplifier requirements.  Sure, there may be room for mathematical discussion on the matter, but the real world difference with regard to these two woofers doesn't exist.  The same is true with regard to the moving mass.

The only issue that might be a consideration is the 2db change in spl.  But, this is a very small change, and has virtually no impact.

The only issue that might be a consideration is the higher Qms of the Accuton C95.  This results in a higher impedance peak in the bass region.  However, thus far I have experienced the 1801C on 3 amplifiers;  a modified Golden Tube SE40SE, a AKSA Life Force MK 2 100, a Atma Sphere OTL 60wpc.  These amps present a relatively wide variation of output impedance and there is no notable problems with regard to the hump in the impedance hump presented by the higher Qms Accuton C95 woofer.  The OTL Atma Sphere and Single Ended Pentode SE40SE perform just dandy.

Dave

[David Ellis]

Hi Dave
Happy New Year to you.

And a happy new year to you also Smithy666.

Very nice looking stuff!  Are the amplifiers in a case for cooling?  I can't quite discern what the blue case thingy is doing.

DAve

[smithy666]

No, the blue surround is actually 7 feet tall and is a wall unit for tv, books etc. There is actually two side by side and all my audio gear fits in the bottom of each. Not your average lounge room...

[MemphisJim]

Hi Dave-

I'm curious. I've got a Golden Tube SE (which we've discussed before) that has many of the upgrades that your amp has. Those upgrades made a big difference and the amp is wonderful. I want your opinion on whether or not I should add a second SE40 se to my system (per Jeff's recommendation that these are even better amps monoblocked) or should I purchase a Lifeforce amp? The money will be about the same either way (used se40se + upgrade components + tubes).

Thanks!
Jim