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

[kevin gilmore]

After i get the final pictures from jason and then if he will let me i will post the schematic.

Then some of you with the knowledge of whats going on will have a field day with the

design...

[philodox]

No time for pics yet, but it sounds great. Seems to be more bass. Front panel is still as ugly as sin, but hopefully swt61 can help me out with that. I still get a slight ~sort of ringing sound~ in either earcup on occasion... but only noticeable when nothing is playing. I'm thinking it might be tube microphonics but am not positive.

The sound is very textured and the imaging/soundstage is just like I remember. I can't wait to hear it with my zapfilter modded CD-E5 [just waiting on a new transport] as I expect that will add the needed detail in the bass and overall speed.

[n_maher]

Glad to hear you got your amp back, Jay. Sounds like you need to put a call into Herbie and get yourself a slew of dampers for your amp.

[philodox]

Glad to hear you got your amp back, Jay. Sounds like you need to put a call into Herbie and get yourself a slew of dampers for your amp.

Thanks Nate, that is exactly what I was thinking... found some dampers at the place I am going to this afternoon [thetubestore], but they are crazy expensive.

[n_maher]

Definitely don't overspend on dampers, if you can find an agricultural/tractor supply/hardware type store odds are you can find rubber o-rings of the right diameter that will get 90% of the way home until you can get Herbie taken care of.

[NotoriousBIG_PJ]

I bought some dampeners off ebay and they melted on the el34 tubes. The herbies version didn't melt so I like it better.

Biggie.

[pabbi1]

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

Ooh, ooh, I know... but, as usual, just won't say... it would cost me too much down the line, cause I wanna build another amp, and know EXACTLY where to get those tranny's...

Let's just say I'm sending my 'I'm returning the asmp, and want a refund' email today (I've been in London all week, and wanted one last sounding before I send it). It is great for everything except Tool, where it simply clips, whether it be from lack of voltage swing or whatever... if he balks, AT ALL, I will roast him here and on Head-fi. And, dump the EA-6, with full disclosure as to why.

[philodox]

Nate - It is funny, but when I went to the tube store yesterday the guy there suggested the same thing when I mentioned that the 6BZ7's seem to be microphonic. He suggested just taking one of the tubes to home hardware or canadian tire and testing it out for the right size there. Combine that with the Jenga blocks tip that I got at the audio store the other day and it is looking to be 'budget upgrade week'.

[hungrych]

It is great for everything except Tool, where it simply clips,

It's trying to protect your ears!

[pabbi1]

Yeah, too late - does the same thing on Jett and Rolling Stones: Sticky Fingers... except for the clipping, SF has NEVER sounded better. Quite maddening that some things can be so spectacular (yes - POSSIBLY better than the Blue Hawaii (ok, with not the best tubes)), and yet, the clipping just kills the entire mood.

But a day without Tool is like a day without sunshine... to me.

[philodox]

Here are some pictures of the 'finished' amp. There are still some aesthetic changed that I will be making - namely the faceplate.

...like I said, that faceplate just must go.

...I love the look of this tube.

...lights out. I can't wait to get a tripod so that I can take a more detailed picture of this type.

[philodox]

Ok, so here is what Peter said about the design to the best of my memory. Also keep in mind that he is forced to dumb down things quite a bit for me to follow.

- 6BZ7/6BQ7A are on the input in paralled and are setup in a 'proprietary circuit' that provides ~6db of gain and has the primary purpose of presenting 100ohms impedance to the rest of the circuit, regardless of the impedance of the source.

Three seemingly contradictory statements, but perhaps not:

- 6CG7/6GU7 are in parallel and work in conjunction with the 27GB5/PL500 for the output.

- The 27GB5 are in a way setup to be the CCS for the 6CG7.

- If you want to say one tube is on the output, it is the 27GB5.

Again, this is all in my words and taken from memory and sketchy notes.

Someone was asking me the output power of the amp recently... can't remember who. Anyways, he said that if you were to give it a wattage rating, it would be 6 watts. He also said that is not the best way to rate the power of a headphone amp since it tells you hardly anything about its ability to drive various headphones. He said a better way to put it is 98volts peak to peak. When I asked him about current, he said that it could put out 600mA at 100volts easily enough.

I asked him about output impedance again and he gave me the same answer, 40ohms.

Hope that helps. We will know soon enough once I get Kevin to look at some pictures.

EDIT: He also said that the 27GB5s are in triode mode.

[kevin gilmore]

- 6BZ7/6BQ7A are on the input in paralled and are setup in a 'proprietary circuit' that provides ~6db of gain and has the primary purpose of presenting 100ohms impedance to the rest of the circuit, regardless of the impedance of the source.

That would be a differential amplifier with a gain of 6db and cathode follower. Hardly proprietary as this is exactly the same circuit that ray uses in the B52 front end.

(subject to picture verification) Also 100 ohm output impedance of that tube as a cathode follower is just not possible. More like 2k. But still a fairly low impedance

output for tubes.

- 6CG7/6GU7 are in parallel and work in conjunction with the 27GB5/PL500 for the output.

For each side of each channel 2 triode sections are in parallel. True

- The 27GB5 are in a way setup to be the CCS for the 6CG7.

An interesting way to describe an inverted cathode follower.

- If you want to say one tube is on the output, it is the 27GB5.

The 27GB5 certainly has the lowest impedance path to the headphones.

Someone was asking me the output power of the amp recently... can't remember who. Anyways, he said that if you were to give it a wattage rating, it would be 6 watts.

Into what impedance?? Certainly nothing in the range of 32 to 300 ohms. (but i'll go and calculate it)

He also said that is not the best way to rate the power of a headphone amp since it tells you hardly anything about its ability to drive various headphones. He said a better way to put it is 98volts peak to peak. When I asked him about current, he said that it could put out 600mA at 100volts easily enough.

Someone is smoking something! Besides which this is clearly irrevelant.

I asked him about output impedance again and he gave me the same answer, 40ohms.

UH maybe. small signal only into medium impedances.

EDIT: He also said that the 27GB5s are in triode mode.

TRUE.

[philodox]

That would be a differential amplifier with a gain of 6db and cathode follower. Hardly proprietary as this is exactly the same circuit that ray uses in the B52 front end.

(subject to picture verification) Also 100 ohm output impedance of that tube as a cathode follower is just not possible. More like 2k. But still a fairly low impedance

output for tubes.

How can you be so sure when you haven't seen this part of the circuit yet? - Edit: Sorry, just noticed your bracketed comment.

He also said that is not the best way to rate the power of a headphone amp since it tells you hardly anything about its ability to drive various headphones. He said a better way to put it is 98volts peak to peak. When I asked him about current, he said that it could put out 600mA at 100volts easily enough.

Someone is smoking something! Besides which this is clearly irrevelant.

Please explain...

[aerius]

600mA at 100V is a cool 60W. The tubes would quickly melt into slag if you tried to put that much power through them, that is if they don't implode. To get 60W from an OTL will take a large number of 6AS7's as in the Atmasphere designs or a really crazy tube like the 833A.

[philodox]

Oh, I see... well, I will say again: "this is all in my words and taken from memory and sketchy notes"

[kevin gilmore]

With a 120 ohm impedance headphone the small signal spice calculates the output impedance as 79.9 ohms.

[philodox]

Cool, what about 400ohms and 32ohms? Those are going to be the two I will be mainly using... moreso the 400ohms of course.

I took some pics last night when Renato came over and will send them your way in a bit.

[kevin gilmore]

Into 32 ohms the output impedance is 28.5 ohms

Into 400 ohms the output impedance is 150 ohms

[recstar24]

Into 32 ohms the output impedance is 28.5 ohms

Into 400 ohms the output impedance is 150 ohms

Ouch, the output impedance into 32 ohms is awfully high, virtually no damping factor whatsoever. With RS-1's the upper bass is going to be bloated and the upper midrange spike might be a bit on the drilling side.

[kevin gilmore]

first of all for completeness the numbers above are for unbalanced output. balanced output numbers slightly higher.

Just for comparison (actual real numbers tested by me and i'll put my money where my mouth is)

All numbers are 1 volt rms output.

raptor 120 ohm load 106 ohm

raptor 32 ohm load 32 ohm

B52 (balanced) 120 ohm load 101 ohm

B52 (balanced) 32 ohm load 30.6 ohm

(this was a surprise as i thought it would be higher)

singlepower white cathode follower with 5687's (can't keep track of model numbers)

120 ohm load 103 ohm

32 0hm load 31 ohm

singlepower cathode follower with 6as7 (called the extreme)

120 ohm load 29 ohm

32 ohm load 18.2 ohm

dynalo

.3 ohm output impedance, 16 to 300 ohm load

dynahi

.13 ohm output impedance, 16 to 300 ohm load

[philodox]

Interesting... output impedance is obviously not everything though as I much prefer this amp to my old dynahi.

[kevin gilmore]

My guess is that jason would like the singlepower extreme with 6as7's a lot.

In which case there would be 2 more amplifiers that he would like even more.

[philodox]

Those being?

I heard the SDS-XLR at the national and it sounded pretty damn good, but the tubes were tweaked for Mikhails R10's and there were better choices for my K340's. I think the fact that I have gotten to the same level for less than a tenth of the cost is pretty impressive.

I'm not happy with the build quality of my amp either, but I do like the sound of it and I don't want to go through the headache of sending it back to Peter again.

[kevin gilmore]

Those being?

One will be a commercial amp, can't speak any more...

The other is a bamaslama, you gotta build it yourself.

(evidently a number of people have done so)

Seeing the latest pictures you should be able to build a mcalister yourself. Its not possible

to do any worse of a job....