Santa Claus DIY Tube Amp

Hi Screamgigi !

screamgigi schrieb:

Interesting comments on that TS 6550 re-issue. Is it produced by the same company that's bringing out the re-issue Mullards?

I'm not quite sure where exactly they are produced only thing i know is that it's an russian plant now. The 12AX7 Tung-Sol reissue should also be a very good Tube, i'll surely give em a try someday.

screamgigi schrieb:

What are your operating points on the 6550?

I'm having mine on a B+ of 360VDC @ around 90mA which sounds pretty good in my opinion, but testing this out is not complete finished. Want to try different op points in the range from 360/100 to 400/70 just to compare. It's been said to me that 360/100 should be best for KT88 in SEP-UL.

screamgigi schrieb:

Ever since Amp-Nut-ji dismissed our little Munna amp , I have been plotting to get even. Plan is to use 4 x 6550 per channel to pump out approx 200 RMS /channel in a monoblock build. Right now I simulating the OPT design to have it locally wound. It will be too big and expensive to import.

Sounds pretty intersting, i've my Mind on Mono's also, and collecting nice parts for them right now. Got those Monsterous Sprague Powerlytic Elcos and a great stepped Attenuator using Vishay's precision R's. To bad i've only one, so i want to import another one from Australia - complete price is at around 40-50 Eur depending on how much i order the more the better - so if anyone would an good cheap Attenuator - let me know ! So my IMHO very fine James OPT&Chokes will go in there someday because i've found some quite good AND cheap replacements for them at Jan Wuesten Only limiting factor on the OPT would be 70mA DC Current, hence the OP Test using this Values (360-400VDC/70mA).

If anyone wants some pictures from the above said, just let me know i could do easily.

BTW he has some nice and good priced Paper-in-Oil caps too.

Also good PIO Caps with reasonably prices could be obtained from Hornfabrik Eder I'm using them in almost all of my coupling points and they sound great.

screamgigi schrieb:

Therefore, your words on the TS reissue 6550 is encouraging and consistent with others posting in AA and elsewhere. How much did you pay for each 6550? It is now in my 'buy' list.

I buy em at Tube-Town.de

Because their price is ok (EUR 27,50 per Tube) and they add no additional fee for Power Tube matching.

Their TT7025 Black Plate is also a very good Tube IMO. I use them as a the first tube in my chain because of their great linearity.

Another thought about your SC Amp: What about delayed B+ using an NE555 Timer to safe some Tube Lifetime ?

Wish u a nice Time !

Regards
Markus

screamgigi-ji said :

Ever since Amp-Nut-ji dismissed our little Munna amp

Alow me to clarify ... for the record... I did NOT 'dismiss' your proposed 20 Watter.

When you were Inviting suggestions on the specs ( like output power) I had said that 20 Watts "Did not float my boat'

I have inefficeient speakers that I love, and one price I have to pay, .... is higher power amplification....

The comment was Never intended to provoke or draw anyone into the "maidan."

Take it easy ...

Your proposed intended project of a "4 x 6550 per channel to pump out approx 200 RMS /channel in a monoblock build" will not only float my boat, but probably float it to Nirvana !

Thanks Markus-ji for that detailed info. 360~380 VDC at 85mA ~ 95mA looks really nice on the curves. What is your Raa ? 4.5K? I shall be looking forward to your valued opinion while planning for that monster amp build.

Amp_Nut-ji

Hey common ! I like to banter with with you
But seriously your monster amp suggestion has been agitating my mind for all this while. Shortly I will present my approach for this build and hopefully you shall be generous, as usual, on that project too.

Cheers !

Hi screamgigi!

screamgigi schrieb:

What is your Raa ? 4.5K?

If you want to have a look at my OPT data sheet->



I'm using the 2.5K tap what leads to a UL tap at 50% which may sound a bit akward, literally, but the acoustics are just breathtaking, don't feel the urge to change anything right now. Tried Pentode mode at 3.5K before but liked 2.5K much more. Maybe i'll give UL at 3.5K a try next time i'm in soldering mood.

What about the delayed B+ i've mentioned ?

You're aware of that problem of a fully applied B+ on a cold Cathode ? This is shorting Tubes lifetime, maybe not drastically, but worth to think about.

Do you know a 'neat trick' to get around this issue by using SS rectification ?

Have to do that by myself for my Amp, but i dislike the fact of having a Solid State Circuit in my Amp and the urge to do a separate PSU for it, so, well..

Regards

Markus-ji

What is the plate dissipation of the TS 6550? For the older version I recall it was either 35 or 42 watts. Assuming it is later try triode connection at 400~420 VDC at around 85mA on the 3.5K tap. I have a gut feeling that a sweet spot is somewhere around that. Do first check up the max Pd first.

Delayed Start:

Sorry I missed to address your comments on the soft start in my last post, which was made well past 2AM when I came home after lots of Last of the festive parties

I would not bother too much with a delayed start when we are dealing with low voltages. It makes more sense on something like an 845 or 211 where voltages is in excess of 1KV. However, a SS delay is a good idea. The “neat trick” would be a standby switch. But do remember to put your standby (or the relay switch) before the capacitor bank or on the return path. IMO the weakest link is the relay. Even the best ones start malfunction after a couple of years. You can not put in a more heft relay cause you are usually limited to a trigger voltage of around 12volts (doubled from the 6,3volt tap) unless a dedicated higher winding (or a separate transformer) is used for the relay. Not worth the trouble IMO. So my suggestion is a standby switch that you operate manually after 30 seconds or so of powering on the amp.

A do have a few proven schematics on the delay. Pls ask me if you need them.

A valve rectifier scores on this front. You get a built in soft start. Depending upon your choice of rectifier it could vary from 5 seconds to 40 seconds.

screamgigi schrieb:

A valve rectifier scores on this front. You get a built in soft start. Depending upon your choice of rectifier it could vary from 5 seconds to 40 seconds.

I've listened to a couple of tube rectifier preamps (not power amps) now - one was an AudioNote(UK) M2B & another was a ref DIY preamp made by a friend. In both cases IMHO I found the bass to be too soft for my liking. Were they the very best implementations of ty\ube rectifiers? Probably not esp. for the M2B case. AN(UK)'s far more expensive preamps have better renditons of valve rectifier ckts. In the DIY preamp case, the rendition was very, very good (this fellow does this for a living as well).
Somehow, I still like the s.s. rectification in a tube ckt - sort of mix & match & the best of both worlds.

screamgigi schrieb:

Interesting comments on that TS 6550 re-issue. Is it produced by the same company that's bringing out the re-issue Mullards?

AFAIK, the Tung-Sol re-issue is being manuf in Russia (as correctly stated b4) by the same Reflektor plant that makes Sovteks, E-H, etc. The equipment used in some part is the same as Tung-Sol used in New Jersey, USA. I've heard this tube & my very reliable source informs me that it's the closest that it'll ever get to the original, venerable Tung-Sol 6550. Much better sound than the Svetlana 6550, which I used previously. They go for $120 for a matched quad here. FWIW.

screamgigi schrieb:

I would not bother too much with a delayed start when we are dealing with low voltages. It makes more sense on something like an 845 or 211 where voltages is in excess of 1KV. However, a SS delay is a good idea. The “neat trick” would be a standby switch. But do remember to put your standby (or the relay switch) before the capacitor bank or on the return path. IMO the weakest link is the relay. Even the best ones start malfunction after a couple of years.

i wanted to add a delayed start to my Sixpacs & found a nice compact & reasonably priced unit made by one Sophia Electric in Washington D.C.
http://www.sophiaelectric.com/pages/parts/delay_action_board.htm

I never actually had it put in actually because I could not get a hold of the people concerned in that company! Maybe it was my bad timing that I was getting these changes done during the 2nd half of December & they were really busy or off during that time?
Anyway, this unit looks really nice, compact & could fit easily in most chassis. Anyway, just FYI.

Hi screamgigi !

screamgigi schrieb:

What is the plate dissipation of the TS 6550? For the older version I recall it was either 35 or 42 watts. Assuming it is later try triode connection at 400~420 VDC at around 85mA on the 3.5K tap. I have a gut feeling that a sweet spot is somewhere around that.

My GE Data sheet for the 6550-A says 42W, Svetlana states 35W for their 6550-C

We'll get to little less than 36W at 420/85 so i might give it a try at 400/85 which should work safely in every case.

Hope that remaining power will be enough to drive my 88dB Tannoys nicely...

screamgigi schrieb:

..my suggestion is a standby switch that you operate manually after 30 seconds or so of powering on the amp. A do have a few proven schematics on the delay. Pls ask me if you need them. A valve rectifier scores on this front. You get a built in soft start. Depending upon your choice of rectifier it could vary from 5 seconds to 40 seconds.

Good points here, i'll go for that standby Switch too in my Stereo and Tube rect. in my Mono's - i want those coke bottle 5V4G's / 83V's

In every case i'm interested in those delay schem's. If you would be so kind to make them available for me, that would be great, thank you.

Regards

Hey bombaywalla!

bombaywalla schrieb:

http://www.sophiaelectric.com/pages/parts/delay_action_board.htm

This was exactly what i was looking for !

I just want to do it by myself 'cause i think i've a couple of fitting relays somewhere in my "collected goodies" box.

Thanks for sharing anyway !


Regards

bombaywalla schrieb:

I've listened to a couple of tube rectifier preamps (not power amps) now - one was an AudioNote(UK) M2B & another was a ref DIY preamp made by a friend. In both cases IMHO I found the bass to be too soft for my liking. Were they the very best implementations of ty\ube rectifiers? Probably not esp. for the M2B case. AN(UK)'s far more expensive preamps have better renditons of valve rectifier ckts. In the DIY preamp case, the rendition was very, very good (this fellow does this for a living as well). Somehow, I still like the s.s. rectification in a tube ckt - sort of mix & match & the best of both worlds.

Tube rectifier and pre-amps are made of for each other. Compared to a power amp, the implementation is not that critical, requirements are not so stringent. My preferred tube for pre-amps will be the Mullard/Philips/BEL EZ81 or EZ80. You still have a lot of headroom.

As for power amps I would look to parallel two tube rectifiers of GZ34 class if my power output is more than 15 watts, even if the total current draw is within the capability of just one GZ34.

The biggest advantage of SS rectifier is lower PSU impendence and resonance fq. We have discussed these in our posts covering the PSU earlier in this thread.

However, I will blindly put in a tube rectifier in a small build such as Linestage or Phono amp. Tube rectifier allows a far natural blossoming of sound, which IMHO silicone diode is lacking. And I am sure most of us prefer the "natural" stuff over the silicone

.:Bulli:. schrieb:

Hey bombaywalla! bombaywalla schrieb: http://www.sophiaelectric.com/pages/parts/delay_action_board.htm This was exactly what i was looking for ! I just want to do it by myself 'cause i think i've a couple of fitting relays somewhere in my "collected goodies" box. Thanks for sharing anyway ! Regards

Markus-ji
Try this. Works great. C1 and R1 control the delay period. Adjust them to your need. Get the best relay you can find preferably those used in industrial control instrumentation.

Hey screamgigi !

This looks quite simple, so i'll try that one soon !

Thanks for the circuit !

What's the current state of the Santa Amp ?

Greets
Markus

screamgigi sir !

is our munna ok ? you have been quiet for a while now.

manek.

hello all,

any news on screamgigi ? the amp ?

manek.

Manek schrieb:

hello all, any news on screamgigi ? the amp ? manek.

Perhaps Santa is taking a break.

Cheers
K

Wasnt this DIY due last Christmas

Easter around the corner

Cheers!

Where is the Santa...can someone in Mumbai make a visit to Northpole.

EL34 Push Pull Triode amp.

This is how it was when finish. Now it has a wooden fascia and an indicator LED.

Backside. Simple. 8Ohm taps. Can be wired as fully balanced. All that is required is an XLR socket.

Ironware. PSU transformer generously provided by Lyrita Audio and made by DELTA Output transformers SILK thailand. PSU Choke DELTA.

Mullard XF4 Double D getter EL34. Fixed bias. Fully triode, full Class A operation. No NFB. Around 20 watts of pure Class A triode operation.

http://img.photobucket.com/albums/v452/corbato/6.jpg

Fully Differential and balanced back end.
Using premium Mullard E88CC. 2 per channel. Precise bias control by MOSFET current source
And those huge Black gate WKZ 100+100uF capacitors came gifted from forum member Rajiv in Chennai. 2 per channel. Bypassed with MKP's.
Coupling capacitors Soviet FT3 Teflon. Resistor a mix of metal film, carbon composition and wirewound.

Hi aks07,

Welcome back!

Is that the erstwhile amp!

Viren.

Fully Differential and balanced back end.
Using premium Mullard E88CC. 2 per channel. Precise bias control by MOSFET current source
And those huge Black gate WKZ 100+100uF capacitors came gifted from forum member Rajiv in Chennai. 2 per channel. Bypassed with MKP's.
Coupling capacitors Soviet FT3 Teflon. Resistor a mix of metal film, carbon composition and wirewound.

viren schrieb:

Hi aks07, Welcome back! Is that the erstwhile amp! Viren.

Thnx Viren-ji.

Yes it is the erstwhile amp. But now in a completely different avatar.
I finished building the old version somewhere around feb. Then a series of domestic setbacks, health problems, etc. My wife is still not fully well, etc etc

I could not post the result earlier. My laptop crashed around the time old amp was finished. I lost the old login info. I did not even know how to look up hi-fi.de Indian forum. Anyways, thanks to a forum member I got the coordinates right and registered again.


While the SC amp was nice, it was something I had done numerous times. There was noting great in keeping a standard push pull amp. It was a nice, classic, tubey sound. Mild and mellow.


So I decided to scrap it after using it for sometime and used the ironware for this amp. As the primary aim (that of sharing the build in this forum) was gone, I went a different approach. This amp features fully differential topology and provides for balanced inputs. The result is a stunningly modern sounding amp, wide soundstage and dynamics of a top end solid state amp. And this is a power amp. You need a line stage to operate it.

Tubes were changed. Out went the 6L6G (a painful decision) and in came the El34. Out went the 6SL6/6SN7 family and in came the E88CC super tube. The design is based the highly acclaimed AW PP-1C design, but I did experiment a lot. I also tride the differential front end with 5842 and the 6H30 Russian super tube. In the end I went back to E88CC primarily cause I wanted to use them. These tube work well in cascade topology and the result attest to that.

Thought its still not fully broken it, I am quite pleased with the amp.

At the work bench

Welcome back.Good to see you again.



K

Hello aks07,

GREAT to have you back on the forum, sharing..

The new Amp seems Really nice.

I wonder if you are likely to Travel to Mumbai or Pune with it.

Would be lovely to hear it.

Thanks my dear friends for the welcome and the kind words.

Unfortunately, my domestic situation preclude any outstation travels for a while. We are still in deep of things. AMP_NUT-ji I will be glad to send it across to you. Let me see. Actually, its still being tweaked.

In the past months i have realised how important it is to have a hobby. I am glad to have many and now I actively encourage others to take up one. It doesn't matter what is your choice; you must have something to de-stress the system.

Right now I planing to try out an active biasing system for this amp. In a nutshell a sensing circuit constantly monitors the input signal and keep adjusting the bias for the output stage on the fly. A simple analogy will be the technology Honda uses in their V-tec engine. Variable valve timing. I got the PCB's made and received the sample CMOS from National. Getting a lot of help from the Seoul DIY Club. At least on the simulation i can see many advantages. Will keep posted.

AMP_NUT-ji, you will be glad to note besides the Santa Claus amp, I have also been tinkering with your fav 6550 tube. I had an EL34 SE amp (DIY of-course) that i was using as my main amp for a while. 6 watts/channel triode connection and no-NFB. Valve rectifier and PIO caps for for power supply and coupling. It was a very musical and smooth amp.

I had never considered the 6550 to be as refined as the 6L6/KT66 family or for that matter the EL34 pentode. But looking at Markus-ji (see his posts above) and amp-nut-ji's mentions, i decided to modify the amp to take in the 6550. Used a pentode loaded 6SN7 driver, RC coupled to TungSol 6550 in triode connection. No. NFB.

And was i startled ! IMHO of all tubes 6550 is the only one which comes closer to refinement and authority that the 845 provides. I am completely mesmerised by the 6550 and now repent having let them idel away for so long. I am using the famous early 60's Smooth Grey plates TungSol 6550. In my amp they produce the fine delicacy of a small tube like 2A3 and deliver the authority of an 845. This is now my main amp !

The conversion process from EL34 to 6550 quite a thing. I was expecting to retain everything from the EL34 and just change the output stage bias resistor. In the event I used a pentode CCS on input stage made up of EL91 in the top and our forum favourite 6SN7 in the bottom. DELTA power transformer and Choke while the Output transformer is wound by a very reputable company called Hashimoto. At around 9 WPC of no-NFB, triode sound, it drives my 88dB Sonus speakers to astounding levels.

This is a pic of my fire breathing 6550 SE amp. 6SN7 as input tube, the El91 pentode CCS load is inside the chassis. There were no extra holes for them.





And this is the sedate earlier avatar in EL34 SE. In this earliest pic 6SJ7 metal pentode was used as input tube. Later I changed over to 6SL7 in a Mu-follower configuration.

Dear aks07

Thanks for a VERY INTERESTING and detailed writeup.

You are doing some GREAT work.

The fit, workmanship and finish of your amplifier is also SUPERB, better than some commercial products that I have seen.

I wonder if you have any plans to insert the 6550s in your latest, fully balanced power amp, currently running on EL34's.

Which (Sonus) speakers do you use ? I envy you that low powers are adequate for your room and system.

I fully agree with you about having a hobby, it IS a Great De-stresser.

scream bhai !!!

welcome back. sure missed the pearls of wisdom for a while. i still call you by your previous avataar as I liked the name so much..still do.

nice looking amp you got there...nice sounding one too. You fit and finish are very good....car to enlighten us on how you manage that ?

manek.

aks07 schrieb:

Thanks my dear friends for the welcome and the kind words. Unfortunately, my domestic situation preclude any outstation travels for a while. We are still in deep of things. AMP_NUT-ji I will be glad to send it across to you. Let me see. Actually, its still being tweaked. In the past months i have realised how important it is to have a hobby. I am glad to have many and now I actively encourage others to take up one. It doesn't matter what is your choice; you must have something to de-stress the system. Right now I planing to try out an active biasing system for this amp. In a nutshell a sensing circuit constantly monitors the input signal and keep adjusting the bias for the output stage on the fly. A simple analogy will be the technology Honda uses in their V-tec engine. Variable valve timing. I got the PCB's made and received the sample CMOS from National. Getting a lot of help from the Seoul DIY Club. At least on the simulation i can see many advantages. Will keep posted. AMP_NUT-ji, you will be glad to note besides the Santa Claus amp, I have also been tinkering with your fav 6550 tube. I had an EL34 SE amp (DIY of-course) that i was using as my main amp for a while. 6 watts/channel triode connection and no-NFB. Valve rectifier and PIO caps for for power supply and coupling. It was a very musical and smooth amp. I had never considered the 6550 to be as refined as the 6L6/KT66 family or for that matter the EL34 pentode. But looking at Markus-ji (see his posts above) and amp-nut-ji's mentions, i decided to modify the amp to take in the 6550. Used a pentode loaded 6SN7 driver, RC coupled to TungSol 6550 in triode connection. No. NFB. And was i startled ! IMHO of all tubes 6550 is the only one which comes closer to refinement and authority that the 845 provides. I am completely mesmerised by the 6550 and now repent having let them idel away for so long. I am using the famous early 60's Smooth Grey plates TungSol 6550. In my amp they produce the fine delicacy of a small tube like 2A3 and deliver the authority of an 845. This is now my main amp ! The conversion process from EL34 to 6550 quite a thing. I was expecting to retain everything from the EL34 and just change the output stage bias resistor. In the event I used a pentode CCS on input stage made up of EL91 in the top and our forum favourite 6SN7 in the bottom. DELTA power transformer and Choke while the Output transformer is wound by a very reputable company called Hashimoto. At around 9 WPC of no-NFB, triode sound, it drives my 88dB Sonus speakers to astounding levels. This is a pic of my fire breathing 6550 SE amp. 6SN7 as input tube, the El91 pentode CCS load is inside the chassis. There were no extra holes for them. And this is the sedate earlier avatar in EL34 SE. In this earliest pic 6SJ7 metal pentode was used as input tube. Later I changed over to 6SL7 in a Mu-follower configuration.

Screamgigi,
welcome back!
I did not recognize your post in my "Cary Audio Factory Tour" thread as your moniker was different.
I now realized that "aks07" & "screamgigi" are the same person.
Sorry to read about your health issues & that your wife is still recovering. You must have been really down & out!! Appears to be some major illness....


I also see that you ditched the 6L6 & P-P & programmable N-feedback. Great!!! Those attributes were destined to make the amp a very mediocre one (as you found out yourself).

Zero global NFB (gotta have the local NFB or else...), triode-connected EL34s & SE amps are the way to go. I purchased an AES/Cary Sixpac which uses EL34 in triode P-P mode & I have to say that there is something special about that triode sound that a beam tetrode or pentode connected in UL mode just cannot give.
So, I'm not surprised that you have found nirvana in these configurations. I am also converging to that tube space - triodes, lower wattage in the 50-60W/ch, which is not as low as what you cited. That tube space yield dynamic & totally jaw-dropping sound. I can now see why so many people love 2A3, 845, 45, 6AS7 triode tubes.

I am surprised re. your comments on the 6550 tube. I also was not aware that it could sound as divine as you have written. However, I know that tubes have a sweet spot for biasing & if you can find that sweet spot you can get pretty damn good sound from them.
The only bias under which I have heard 6550 tubes is an UL P-P, which is not the best topology by a long shot.
I have not heard the class-A CAT amps that use 6550 tubes, which people are raving about.

Hello amp_nut-ji and manek-ji

In the pics some of the blemishes are not apparent ! Although, i would have preferred a perfect finish, its impracticable to so for a single construction. I get hold of the local electrical contractor for the chassis. They make a lot of those boxes for their junctions etc. They make the chassis as per my dimension and i punch out the holes etc. Finally its powder coated. If there were more than 5 chassis of the same design, i would have taken to a professional fabricator. But in all modesty I can say my amps are at par (or maybe better) with the Cadence build quality !

Yes this design can take the 6550 or for that matter the triodes like 300B, 2A3, 45. With a change of Output transformer I can use EL84, 6V6 etc. But on this build I am using EL34 cause 6550 will drain more heater current and the current power transformer heater winding is marginal even for the EL34. You will recall this tranny was originally planned to power 6L6's. With the 6550 thing get very hot. I did try and the performance was a notch better than the 6550. I will look to reinforce the heater winding in future so that 6550 can be used.

I use Sonodyne Sonus 2605. Actually, these are on extended lend from a friend. Not the best of speakers but adequate for my needs at the moment.

bombaywalla-ji

Thanks for your kind words.

Actually, the 6L6 was “dichted” solely due to its limitation vis-a-vis this balance topology. I intended to triode wire the output; in that configuration 6L6 would have given a minuscule PO of around 6 WPC. The other major issue was the drive requirement. A triode 6L6 would require a more stiffer swing, calling for an additional drive stage (a cathode or MOSFET follower) that I wanted to avoid. EL34 is a true “audio” pentode; it requires a just a whiff of input to drive it to peaks. A triode EL34 can give out a decent 12~14 watts of Class A watts.

As for sonics of 6L6 versus EL34; its a long debate, though i slightly prefer the 6L6.

The erstwhile 6L6 powered Santa amp was not at all a bad thing despite it gNFB. Just that it was nothing outstanding. It retained all the sonic characteristics (pleasant mostly) of a classic tube era amp; whereas I wanted to experiment with a more “modern” sound particularly as I have more that 10 Push Pull tube amps already comprising both DIY and classics such as the QUAD II and Dynaco ST70 etc.

I have no idead on the reissue 6550. I only have the old US made TungSol and GE 6550's. I am sure the new reissue are as nice too.

Great to have you back, Scremgigi / Aks07

Those Sonodynes are nice entry-level speakers, but won't cut it with your high quality valve amps. Now, you need to take us through the DIY of a fine pair of speakers. It will complete your setup.

Neutral schrieb:

Great to have you back, Scremgigi / Aks07 Those Sonodynes are nice entry-level speakers, but won't cut it with your high quality valve amps. Now, you need to take us through the DIY of a fine pair of speakers. It will complete your setup.

Thanks Neutral-ji

Sure the idea seems great ! How about a Full range project using Fostex drivers ? But let me warn you that my speaker building skills are at a scale of 1/10.

The Sonus is actually not bad for the money. I do have other speaker systems also.

I remember you living in Chennai. It could be possible for you to connect up with forum member Rajiv who too live in Chennai. He has a lot of vintage audio goodies including Tannoy monitors and QUAD/Leak amps. Do PM him. I am sure he will be glad to meet you.