HELL HATH FROZEN OVER! [and a tube question for Earl]

[philodox]

Hey all,

Just heard from my friend Renato [looser101] and Peter has finally dropped my amp off to him, so I will be getting it back tonight.

I'll be sure to take pics and let you know how it is and if there are any improvements. Apparently the faceplate still looks pretty ghetto, but I will be having a nice wood one made by Steve [swt61] anyways.

Now on to the tube question:

He has removed the 4 6H30's from the amp and installed 4 6BZ7's. I haven't talked to him about this, so I don't know the reason, but I am sure he will explain it to me tonight... though I doubt it will make any sense. Anyways, what do you know about hte 6BZ7? What brands would you recommend? Any other tubes that are equivalent to it?

Thanks in advance,

Jay

[JBLoudG20]

Nice man, I hope you like it after all the crap you went through.

[Dusty Chalk]

Dude, I just noticed your sig -- you own an Infiniti? Love those FX series vehicles they have.

Oh, and Philodough -- huzzah.

[Guest sacd lover]

Oh geez .... a 6bz7? The 6bz7 is a lower power tube that was the foreruner to the 6dj8; so the 6dj8/6922 is the closest equivalent. This tube has a heater current draw of around 0.4 amps .... and a gain of around 36 .... which seems sort of odd if these are the output tubes. The good news is the 6bz7 is generally very inexpensive and easy to find. The bad news is these dont have much power output ... think Ear Max Pro. I used this tube in a Woo 3 as a gain tube. I liked the GE 6bz7.

http://www.nj7p.org/Tube4.php?tube=6BZ7

[deepak]

The K340 don't need that much power

Sound great with the Melos

[Guest sacd lover]

The K340 don't need that much power

Sound great with the Melos

The 6h30 is a much more powerful tube than a 6bz7 .... more along the lines of a 5687. Anyway, I am confused, one minute the 340 is a pain to drive and then someone says it is not. Which is it? I remember Phil complaining about the bass. The bass is not likely going to get better with less power even if the 340 needs mostly voltage swing.

[aerius]

I think jpak's being sarcastic, the K340's are a pain in the ass to drive, in an OTL amp I personally wouldn't use anything less than a 6BL7 and with transformer output a 6SN7 is about as low as I'd want to go. A 6BZ7 just doesn't make sense to me.

[deepak]

There was some tongue in cheek humor implied since the Melos does use "lowly" 6DJ8 tubes, but it also has the SS amplification stage.

[kevin gilmore]

The 6bz7's are most certainly in the input section, and not any part of the output section. There are large output

tubes for the active current sources and other tubes with paralleled sections as the output amplification element.

Don't remember the exact tube compliment at the moment. Similar in design to another tube amplifier well

liked around these parts. Also remember that this is a balanced amplifier.

[Guest sacd lover]

The 6bz7's are most certainly in the input section, and not any part of the output section. There are large output

tubes for the active current sources and other tubes with paralleled sections as the output amplification element.

Don't remember the exact tube compliment at the moment. Similar in design to another tube amplifier well

liked around these parts. Also remember that this is a balanced amplifier.

Per Philodox ...

What are the tubes and what is the circuit topology?

"I still need to get more info on that. I think the 4 6GU7's are the input tubes and the 4 6H30's are the output tubes, with the 4 27GB5 Pentodes used in the CCS' and the other Pentode [forget which he used] as a regulator, but I am not 100% on that.

I also know that there is no feedback being used and that he employs negative PSU's for some or all of the stages. There are 8 power supplies in total I believe."

I looked up the amp and the tube complment includes four 27gb5 pentodes. I was thinking of the McAlister preamp. If I remember correctly, the input is a 6cg7 passing on to the 6h30 .... which is now replaced with the 6bz7. The 6h30 and 6bz7 do have the same pin out. The 6bz7 has a lot more voltage gain but a lot less current drive. If he is optimizing the amp for the k340 maybe that is why he is going for more voltage gain. I hope Phil likes the GE 6bz7 becasue GE made most of them. I am still not sure what the output tubes are? The 27gb5's would make the most sense but in the post above that is not what Phil Stated tha last time I remember reading about the amp.

[kevin gilmore]

Jason was wrong.

Before the final upgrade

the 27gb5's were the active top current sources

The 2 sections of each of the 6cg7 were in parallel and

were the output gain stage tubes.

The 6h30's were doing absolutely nothing usefull !!!!!

(If you haven't figured it out by now, I have the schematic!)

After the upgrade (i'm guessing here)

The 2 sections of the 6bz7's are in parallel and 2 of them

form an input stage differential amplifier. Same as the input stage of the B52.

So you can supply balanced input, or unbalanced input.

And then everything else is the same.

[philodox]

Yeah, Kevin knows what he is talking about... the 6H30's were not hooked up originally. This is primarily what needed to be 'finished'.

My guess is that these 6BZ7's are on the input or used as a CCS or something like that.

But, all that aside [no point in figuring it out before Kevin takes a look at some updated pics and draws it out] I got the amp last night... and the right channel was fucked. Swapped all the tubes and it was still pooched. Called Peter and he picked it up from Renato today and will [apparently be dropping it off tomorrow afternoon... or was that thursday?]

weeeeeeee

KG - "Similar in design to another tube amplifier well

liked around these parts."

Which one?

And Earl, any recommendations for 6BZ7's? Are 6BQ7A's equivalent? From what Kevin told me, the 6BZ7's are a higher gain version of the 6922. Is this a bad tube if it is used on the input or somewhere else? Am I correct that you only thought it was bad since you thought it was used on the output?

[n_maher]

But, all that aside [no point in figuring it out before Kevin takes a look at some updated pics and draws it out] I got the amp last night... and the right channel was fucked. Swapped all the tubes and it was still pooched. Called Peter and he picked it up from Renato today and will [apparently be dropping it off tomorrow afternoon... or was that thursday?]

Oh come on, after 6 weeks and it shows up busted?

[Guest sacd lover]

Yeah, Kevin knows what he is talking about... the 6H30's were not hooked up originally. This is primarily what needed to be 'finished'.

My guess is that these 6BZ7's are on the input or used as a CCS or something like that.

But, all that aside [no point in figuring it out before Kevin takes a look at some updated pics and draws it out] I got the amp last night... and the right channel was fucked. Swapped all the tubes and it was still pooched. Called Peter and he picked it up from Renato today and will [apparently be dropping it off tomorrow afternoon... or was that thursday?]

weeeeeeee

KG - "Similar in design to another tube amplifier well

liked around these parts."

Which one?

And Earl, any recommendations for 6BZ7's? Are 6BQ7A's equivalent? From what Kevin told me, the 6BZ7's are a higher gain version of the 6922. Is this a bad tube if it is used on the input or somewhere else? Am I correct that you only thought it was bad since you thought it was used on the output?

Most 6bz7's were made by GE. The 6bz7 is a good tube. The 6bq7a is the direct sub. Most of the time when I get a 6bz7 the box will say .... 6bz7/6bq7a.

I would be throwing things if I was in your situation.

[JBLoudG20]

Slander time!

[deepak]

Slander time!

Do you have something against McAlister as well, or does stirring the drama pot make you hard?

[philodox]

I just want my amp to work. Fuck, it sounded great before when the 6H30's were not even hooked up!

That said... If I get it back and he throws me any lies about the design and when we open up I see those lies, that will be the time for slander. I am not going to ruin him for being a procrastinating ass. But I will not be lied to.

[JBLoudG20]

Do you have something against McAlister as well, or does stirring the drama pot make you hard?

Wow somebody wake up on the wrong side of the gene pool this morning?

[deepak]

Wow somebody wake up on the wrong side of the gene pool this morning?

Actually all in all a good day, I got off early this afternoon and scut work was minimal

It seems philodox and pabbi are the only ones that had dealings with McAlister (correct me if I'm wrong and you got screwed over as well) so if they want to have a public stoning it's up to them to do so. I'm grateful they brought this to our attention, I know where I'm not going if I want an estat amp.

Good thing you assumed my question was rhetorical

[philodox]

Well, mine is a dynamic amp... but I think it is safe to say I will not be buying another amp from him. The only saving grace is that it sounds great and was *very* cheap. After all the time it has taken the deal seems a bit less attractive though.

[deepak]

Well, mine is a dynamic amp... but I think it is safe to say I will not be buying another amp from him. The only saving grace is that it sounds great and was *very* cheap. After all the time it has taken the deal seems a bit less attractive though.

I know. Around this time I was thinking about getting an O2 and an EA4 as a reward for finishing my boards, but then a good deal on an HP-2 came along

I guess I was a little lucky since I put off buying the O2 setup when I read in another thread that build times were close to 4 months, and obviously now this.

[kevin gilmore]

KG - "Similar in design to another tube amplifier well

liked around these parts."

Which one?

Now that would be cheating NO??? Besides which the person that makes that

"other" tube amp would argue it is completely different when it is actually 95%

the same

This is pretty much the last time i'm going to ask that particular person to send

me the electrostatic portable transformer he has promised to send me for over

6 months now. After that a whole bunch of schematics and pictures may just

have to appear

[bhd812]

Now that would be cheating NO??? Besides which the person that makes that

"other" tube amp would argue it is completely different when it is actually 95%

the same

This is pretty much the last time i'm going to ask that particular person to send

me the electrostatic portable transformer he has promised to send me for over

6 months now. After that a whole bunch of schematics and pictures may just

have to appear

I wanna hear which amp it is now also...

this may get fun, I really have no idea who it could be

[philodox]

This is pretty much the last time i'm going to ask that particular person to send

me the electrostatic portable transformer he has promised to send me for over

6 months now. After that a whole bunch of schematics and pictures may just

have to appear

oooooooooo

The evil in me sort of wishes that he doesn't send it to you.

[Carl]

The 6BZ7 is an unusual heater version of the 12BZ7, which is somewhat similar to the 12AX7. It's a high gain tube (amplification factor around 100), but with about twice the anode current. It's a very non-linear tube and doesn't sound especially good.

Why replace a nice sounding tube like the 6N30 with one? If he needed more gain there are other options, 6C45s are nice, alternatively he could have used a nice pentode or even (gasp) solid state. Makes no sense to me, I'm afraid.