Author Topic: alexg's DIY Tube Projects (Read 60328 times)

alexg · « **Reply #120 on:** Nov 18, 2007 at 11:48 AM »

After the success of my parafeed 12b4 amp, am working on a parafeed 6080 design.

Originally, I was thinking driving this with a 6n1p, but upon double checking of the circuit and values, I found that the 6n1p will not be able to swing the 6080 to full power. The 6080 needs around 80 to 100volts from the driver. The 6n1p will only delivery around 50 to 55V.

Looking at options, I narrowed it down to 12sl7 and 12at7, driver tubes that I have on my stash. I will be borrowing the power transformer from my 832 amp and it does not have 12v heater tap, so I will be using the 12at7 (which is quite ok, it can deliver more current).

I will be starting this amp soon. I will post pictures soon.

Leonidas · « **Reply #121 on:** Nov 19, 2007 at 11:17 PM »

Alex,

Looking good. Ngayon lang ako nag browse thoroughly kaya ngayon ko lang nakita. This is like the reality show "Pimp My Ride". Yeahhh. Yo da man!

cheers

rq/leonidas

alexg · « **Reply #122 on:** Dec 14, 2007 at 07:08 PM »

Update:

I am more than halfway done wiring the amp. Here is the upskirt picture:

Hopefully, it will sing or smoke this weekend. Am still waiting for the painted transformer endbells.

squatt3r · « **Reply #123 on:** Dec 14, 2007 at 08:52 PM »

sir alexg, how much inabot itong project na 'to?

ipopost ba ito sa diyaudioprojects.com?

alexg · « **Reply #124 on:** Dec 15, 2007 at 08:23 AM »

Quote from: squatt3r on Dec 14, 2007 at 08:52 PM

sir alexg, how much inabot itong project na 'to?

ipopost ba ito sa diyaudioprojects.com?

This is the same circuit posted on diyaudioprojects.com.

Materials cost a bit more than 20K. Transformers were wound on cores that are Z11, PSU capacitotrs are Nichicon or Nippon Chem and Evox Rifa, no surplus PC PSU caps here. Coupling caps will either be Wima or Mundorf (I found that I like the Mundorf ZN coupling cap for this amp, this mundorf is very reasonably price, I can't hear justifiable difference when using the much more expensive Mundor for coupling). Plate resistors for the 6n1p driver is wirewound, as well as the cathode resistor of the power tube. PSU uses a 10H smoothing choke (10H loaded, 20H unloaded), OPT is oversized (we found that oversized OPT sounds better, but of course cost much more).

I have not tried using lower quality core (H20 and H50, used my most Raon winders) on the PSU. My winder/friend Edrel Sison refuses to use cores that are not Z11 or higher in quality.

Hookup wires are teflon insulated, tinned, OFC copper.

As featured on diyaudioprojects.com, this amp is quite very good for tube rolling (it can use KT88, 6550, EL34, 6L6 for power tubes; and it can use 6n1p and 6dj8 variants for the driver tube). Just imagine the possible combination using different variants of those tubes!

This circuit was the tube amp playing with the Vandersteen 1C at the Alabang Hifi Show last July.

Will post more pictures later today.

alexg · « **Reply #125 on:** Dec 15, 2007 at 07:03 PM »

At around 4:30 pm today, I finished this SE KT88 amp. After checking for smoke and melting plastic, which I found none, I proceeded to check the voltages. All voltages are within 10% of specs.

I proceeded to connect it to my system (CD player into a Monica2 DAC with SS I/V stage into a foreplay inspired preamp and my Fostex iBIB speakers).

Powered everything up, absolutely very quiet amp (connected to my 91db speakers), hit play on my CD player and, wow, Diana Krall is singing!

docsialu · « **Reply #126 on:** Dec 15, 2007 at 07:17 PM »

wow, congrats to you sir alex and to the lucky owner,

s2kov · « **Reply #127 on:** Dec 15, 2007 at 07:37 PM »

gandah!

padinig naman!

alexg · « **Reply #128 on:** Dec 15, 2007 at 07:48 PM »

Quote from: docsialu on Dec 15, 2007 at 07:17 PM

wow, congrats to you sir alex and to the lucky owner,

Doc, thanks.

Quote from: s2kov on Dec 15, 2007 at 07:37 PM

gandah!

padinig naman!

Sure. BTW, I ordered a pair of 2a3, I want to do a parafeed circuit, and maybe a Sun Audio inspired 2a3 (if I will get lucky and find the schematic

)

alexg · « **Reply #129 on:** Dec 15, 2007 at 08:10 PM »

Here is the picture of the 6080 parafeed while I was doing my preliminary layout.

I have finished wiring the amp and and it sounded good, the vocals are great, bass is quite tight, but the bass is not as good as the KT88 SE.

For Jazz and vocals it is a great amp, as well as rock!

I will post the latest picture soon. I have not painted the chassis yet, but I am done with the circuit. 12at7 driving the 6080 in a parafeed circuit. I am using a Talema toroidal mains transformer for OPT!

s2kov · « **Reply #130 on:** Dec 15, 2007 at 09:09 PM »

surely, will send you the schematic!

Quote from: alexg on Dec 15, 2007 at 07:48 PM

Doc, thanks.

Sure. BTW, I ordered a pair of 2a3, I want to do a parafeed circuit, and maybe a Sun Audio inspired 2a3 (if I will get lucky and find the schematic )

Leonidas · « **Reply #131 on:** Dec 15, 2007 at 09:47 PM »

AlexG,

Like a father waiting for his newborn child to spring out from the delivery room. This is how I feel. Poging-pogi with the JJs a. Hmmmm hope it mates well with my KEFs and Altecs waiting. Tapos foreplay naman. Perfect.

cheers,

Leonidas/Robert

alexg · « **Reply #132 on:** Dec 16, 2007 at 07:52 AM »

Quote from: Leonidas on Dec 15, 2007 at 09:47 PM

AlexG,

Like a father waiting for his newborn child to spring out from the delivery room. This is how I feel. Poging-pogi with the JJs a. Hmmmm hope it mates well with my KEFs and Altecs waiting. Tapos foreplay naman. Perfect.

cheers,

Leonidas/Robert

Somehow on your amp, I like the sound of the ultralinear mode. On mine, the ultralinear is quite boring. Hehehehe...

Your amp sounds great with Siemens EL34! Vocals are to die for, you might want to scout for NOS Siemens EL34. Not too shabby too with JJ El34, but does not sound so hot with the Electro Harmonix EL34 (of course, your preference might be different).

See you Tuesday or Wednesday next week.

Leonidas · « **Reply #133 on:** Dec 17, 2007 at 02:41 PM »

Alex,

Haven't really tried listening in ultralinear mode. My EL34 is Gold Aero. Mahirap maghanap ng nos siemens, will try in Balikbayan me nakita akong siemens 6l6 baka me maligaw na el34. Pwede rin pala ako mag tube roll sa driver. What other types of tubes pwede? Howbout yung rectifier?

robert/leonidas

alexg · « **Reply #134 on:** Dec 17, 2007 at 04:41 PM »

Quote from: Leonidas on Dec 17, 2007 at 02:41 PM

Alex,

Haven't really tried listening in ultralinear mode. My EL34 is Gold Aero. Mahirap maghanap ng nos siemens, will try in Balikbayan me nakita akong siemens 6l6 baka me maligaw na el34. Pwede rin pala ako mag tube roll sa driver. What other types of tubes pwede? Howbout yung rectifier?

robert/leonidas

The driver tube is 6n1p, you can use 6dj8 (but don't get the expensive 6dj8 like amperex) you might not like the result (I tried the amperex on mine, did not like the result).

The sovtek 6n1p is the one that will come with the amp, I have another military 6n1p that we got from ebay if you are interested, they cost 600 pesos and are NOS. The Sovtek and the military 6n1p sound quite different.

For a pair of Siemens EL34, I got a pair from Earl Estrera of this forum, pm him, I think he still have a pair, quite expensive but worth every peso that you spend on it.

How many Gold Aero EL34 do you have? Are those NOS?

Leonidas · « **Reply #135 on:** Dec 18, 2007 at 09:52 AM »

Alex,

No idea on my Gold Aero's History. But net searches yielded very positive feedback on the brand some even say they have the best el34's, well that's arguable of course. I will try em with my amp and share my findings. I'll stick with the sovtek 6n1p in the meantime so I can save up for the foreplay.

Robert/Leonidas

romymartinez · « **Reply #136 on:** Dec 19, 2007 at 05:51 PM »

Sir Leonides,

Congrats on your nice new amp!

romymartinez

alexg · « **Reply #137 on:** Dec 19, 2007 at 11:59 PM »

Nice seeing you again Robert.

Thanks for the album (CD) of your wife. Her voice is heavenly, I wish she will do another album!

Am also glad that you like your new amp. I will be re-wiring my amp's PSU so I can incorporate what I did on your amp's PSU, I like the clarity and dynamics of your amp better than my amp.

See you again early January for your new tubed audio gear!

ches · « **Reply #138 on:** Dec 20, 2007 at 07:03 PM »

congrats alexg on finishing the amp.

Leonidas · « **Reply #139 on:** Dec 20, 2007 at 07:05 PM »

AlexG,

Tnx. My wife was thrilled with your comments. Her next album will be instrumental with a few guest vocalists to interpret her original compositions. She's more of a piano virtuoso than a singer.

Anyway, I was not able to spend a lot of time with the amp last nyt kse I was dead tired and today am rushing lots of work before christmas break so hassle. Anyway, am still waiting for the full range speakers so I'll reserve my observations muna till I put them together. Right now kinabit ko muna sa Advent3 ko kasi dun pinaka maganda tumunog. Na notice ko lang sa KT88 medyo on the brightside pag Kef ang partner. With your amp kse using 6550 tamang tama lang even with the Kefs. So I guess I would be getting a pair of 6550s soon.

Anyway, tnx for making my audio life more exciting this christmas. Cant wait to see my foreplay!

cheers,

robert/leonidas

oweidah · « **Reply #140 on:** Dec 20, 2007 at 07:48 PM »

Qbral! talagang Tubero ka na ah!

Congrats & happy holidays to both of you!!!

Leonidas · « **Reply #141 on:** Dec 21, 2007 at 01:57 AM »

Rene.

Oo nga e. simula na to ng walang hanggang wagas!

Happy holidays din sayo at sa lahat!

alexg · « **Reply #142 on:** Feb 18, 2008 at 01:21 PM »

It all started when I started exchanging emails with a Kiwi guy (Bruce Ward) who wants to build a copy of my SE KT88 amp based on Mikael Abdellah's design at diyaudio.com.

Bruce works for Tait communication in New Zealand (secured radio designer and manufacturer, these secured communication equipment are used by embassies and other agencies, usually, the black kind), and one day he told me they found a box of NOS tubes at their warehouse. He said the tubes are 6080. Being a very nice guy, Bruce sent me 4 pairs of 6080s and at the same time I bought another 5 pairs from trademe.co.nz (Kiwi's version of ebay.com). I intend to use them as voltage regulators for my projects!

I started reading about 6AS7/6080 and found several people have used these tubes as power tubes for amps, these tubes are designed to be voltage regulators.

I opted to do a parafeed circuit using 12at7 as driver. The project was breadboarded and stayed that way for a few months. This weekend I decided that my parafeed 6080 deserves a better chassis:

Chassis sanded and fitted on the plinth.

Aluminum plate painted with automotive clear polyurethane and the plinth oiled. The two transformers are plate chokes for the 6080.

Testing the amp. The transformer endbells underneath the plinth is used as temporary feet for the amp (This amps gets very very hot, 2.5A 6.3V 6080 heaters, and the single tube is dissipating almost 24 watts).

It sounds excellent for what it is, a tube regulator for power tube, ordinary toroidal transformer for output transformer!

In all, these amp have 8 transformers consisting of 1 power transformer, 1 smoothing choke and 4 plate chokes! All of the irons are wound on Z11 cores done by Edrel Sison. The OPTs are toroidal power transformers from RS.

Between this and my SE KT88, this amp gets more playtime than my SE KT88.

qguy · « **Reply #143 on:** Feb 19, 2008 at 05:54 AM »

Hi alex,

I noticed that there is only one tube, how does it handle the left and right channels ?

ATJr. · « **Reply #144 on:** Feb 19, 2008 at 07:08 AM »

Quote from: qguy on Feb 19, 2008 at 05:54 AM

Hi alex,

I noticed that there is only one tube, how does it handle the left and right channels ?

it's a dual triode, 2 sections in one envelope capable of 15watts per plate......there are others like this tube, the 6258, 6336 and the russian 6c33 are other types and have even more power dissipation capability.......

one section, one channel, simplicity is the salient feature of this amp......the use of choke plate loads enables the 6080 tubes to be driven well, a simple resistor plate load will have a hard time with this amp....

good job Alex!

edrel sison · « **Reply #145 on:** Feb 19, 2008 at 11:24 AM »

great work on that plinth alex. very nice wood. this is a very encouraging project!

romymartinez · « **Reply #146 on:** Feb 19, 2008 at 12:23 PM »

Congrats Sir alexg.

Ilang watts per channel ito, Sir?

romymartinez

ATJr. · « **Reply #147 on:** Feb 19, 2008 at 12:33 PM »

Quote

Ilang watts per channel ito, Sir

between 3 to 6 watts....

docsialu · « **Reply #148 on:** Feb 19, 2008 at 07:07 PM »

nice work again sir alex, keep on inspiring us with your projects,

qguy · « **Reply #149 on:** Feb 20, 2008 at 08:25 AM »

I reckon the same principle applies for those tube pre-amps and CD players with single tubes right ?.. always wondered how those things work..

Quote from: TonyT on Feb 19, 2008 at 07:08 AM

it's a dual triode, 2 sections in one envelope capable of 15watts per plate......there are others like this tube, the 6258, 6336 and the russian 6c33 are other types and have even more power dissipation capability.......

one section, one channel, simplicity is the salient feature of this amp......the use of choke plate loads enables the 6080 tubes to be driven well, a simple resistor plate load will have a hard time with this amp....

good job Alex!