Root 666

[azatplayer]

This was my first build nearly 2 years ago. I loved it at the time but grew weary of it. And of course developed an addiction for building..
Funny that this post was up today as i had gotten the old girl off the shelf today, blew the dust off and gave it some time.
In the mean time i have discovered a site with a lot of amps with gutshots and chassis shots.
I had a quick look there today and theres a couple 66's using chokes. I knew the Z28 used a choke but none of the schemos ive seen for the 66 have on on it.
Makes me wonder if thats where mine has gone awry. I dont get the great cleans and the big volume theyre known for. I dropped the UL sometime back and put another filter stage to go non UL, was louder.
I have a couple chokes on hand, but as theyre UL, then ALL the current is passing thru the choke? Its not a big looking choke he uses.
As a side note, i heard heyboer are building a LOT of Z trannies.

[LOUDthud]

UL amps with choke filtered B+ require something a little different in a choke. Since the choke needs to pass all the current of the power supply, the DC resistance need to be lower than typical choke used for Screen Node filtering. The choke used in the old Sunn UL amps was about 50 ohms for a 60W amp. Two in parallel were used for 120W amps. Inductance was on the order of 1 Henry. With 20uF or 30uF caps, this got the ripple down to about 10V p-p. You can juggle these numbers around to get the ripple and voltage regulation as tight or loose as required. Equipment made in the 30's and 40's had 8uF caps and 8 Henry chokes that weighed 10 pounds. I have a 50W amp that uses 100uF on the input, 220uF on the output and a 0.6H 30 ohm choke. Ripple is less than 1V p-p.

[mcrracer]

This was my first build nearly 2 years ago. I loved it at the time but grew weary of it. And of course developed an addiction for building..
Funny that this post was up today as i had gotten the old girl off the shelf today, blew the dust off and gave it some time.
In the mean time i have discovered a site with a lot of amps with gutshots and chassis shots.
I had a quick look there today and theres a couple 66's using chokes. I knew the Z28 used a choke but none of the schemos ive seen for the 66 have on on it.
Makes me wonder if thats where mine has gone awry. I dont get the great cleans and the big volume theyre known for. I dropped the UL sometime back and put another filter stage to go non UL, was louder.
I have a couple chokes on hand, but as theyre UL, then ALL the current is passing thru the choke? Its not a big looking choke he uses.
As a side note, i heard heyboer are building a LOT of Z trannies.

Can you share this "gut shot" web site?

[FYL]

Can you share this "gut shot" web site?

You may try this thread on a German board:
http://www.musiker-board.de/vb/amps-box ... reien.html

Caution: Amp pr0n with large pictures!

[mcrracer]

Thanks, Nice site.

[M Fowler]

Chopstuck,

Nice, but did you know your amp says DO NOT OPEN on the back?

[topbrent]

Can you share this "gut shot" web site?

http://www.proguitar.de/ProGuitarPreisl ... liste.html
This site has a lot of great gutshots.

[chopstuck]

Wow, "Do Not Open" they must have been hiding something in there.

Honestly I thought I was going to get blasted for my patented dissimilar film PI technology. In fact I will make it my tagline !

[azatplayer]

This was my first build nearly 2 years ago. I loved it at the time but grew weary of it. And of course developed an addiction for building..
Funny that this post was up today as i had gotten the old girl off the shelf today, blew the dust off and gave it some time.
In the mean time i have discovered a site with a lot of amps with gutshots and chassis shots.
I had a quick look there today and theres a couple 66's using chokes. I knew the Z28 used a choke but none of the schemos ive seen for the 66 have on on it.
Makes me wonder if thats where mine has gone awry. I dont get the great cleans and the big volume theyre known for. I dropped the UL sometime back and put another filter stage to go non UL, was louder.
I have a couple chokes on hand, but as theyre UL, then ALL the current is passing thru the choke? Its not a big looking choke he uses.
As a side note, i heard heyboer are building a LOT of Z trannies.

Can you share this "gut shot" web site?

This is a pretty cool site. I just saw a pic of a rooter without a choke. So seems the other pics ive seen with one may have been an early iteration of the amp.
http://spinoo.free.fr/projetG5/Images%20Amplis/

[azatplayer]

Hey Mark, would it be possible for you to measure some voltages on your build?
I just never got the cleans i thought there should be, the piano deep tones.
Well looking at your layout as opposed to the one i used, the difference is the lower filtering, and the dropping string.
I have 50-50-47 filtering with a 27k then 47k. Its always been a dirty amp and a little dark.
I just dropped the 47k out for a 27k as per your layout, also mine has a 1.5k in V1 cathode, with a 25uf cap. I increased that to 2.2k as per layout.
These 2 things alone have made a sizeable difference, i can run my tele neck flatout with the amp on half, and theres some nice clean tones. Stil i tiny bit dark, im thinking i might try a cut control in there, as i dont want to make the first cathode smaller/brighter, as the lows are pretty sweet. Just a little cut would be nice, should work ok?
Then im gonna reduce the 3rd stage 47uf to 22uf. See if i can free it a tad.
I have with a GZ34, 460V plate. With a 5U4G i have 444V plate, i like this setting.
What i did notice, when i put the 5U4 in, it was biased pretty cool, as i increased the bias voltage, it got a little brighter. So maybe they need to be run n the hot side.
Im discovering why i got so hooked all over again Cool amp.

[Structo]

Man, a lot of great amps on that site.

http://www.proguitar.de/ProGuitarPreisl ... liste.html

[M Fowler]

azatplayer

I will take some measurements I had trouble biasing mine for initially kept redplating. It sure would have been easier with the correct PT and OT or just bought a used 66 since prices are dropping.

Glad you rediscovered a great amp.

Mark

[azatplayer]

Thanks Mark. I have it sounding pretty decent now. I did drop the last stage filter to 22uf, but it lost a little something so the 47 went back in. I find running at 7o percent bias, sounds the best. Brightens things up nicely.
I need to have a hunt around for some more ef86's now. I have only got a couple JJ's a few svet's, gotta find some more.
Tried a presence control and i can not hear any difference with it? Odd.
Tried a .68 in first cathode, sounded crappy. I think the deep tones it exudes, are the focus, which leads me to think the ef86 is the key to shimmer and brightness. Tried a few 12AX7's too. Not much diff in the PI. I like the idea of a 12AX7 in V1. Might have a play with that.
As an aside, i converted a big bottle vibrachamp recently to this exact tonestack. Single KT66. Wow! I have had trouble cooling the input to the power stage some, but man oh man, the bax/james stack into SE big glass, is something else, and the way the B/T gains work is really really cool.
I must finish tweaking that thing, its really cool and really LOUD!

[M Fowler]

Z made another amp with 5751 in V1 and EF86 hitting hard in V2 maybe that is what a guy needs too.

I will try get that info tomorrow night I got two other amps on the bench right now.

Mark

[M Fowler]

azatplayer

I am adding the changes needed to the layout for when not using the UL OT wire from B+ to pin 6 of each power tube not shown on regular layout.

I need to work on lowering V2 voltage.