So I bought a storage unit and inside was...

[Heavysound]

Hello everyone,
My name is Al. This is my first post and formal introduction (as I did not see a thread dedicated to intro's). Thanks for having me, good to be here, etc..

So anyway, I recently bought an entire storage unit for a record collection and inside was a bunch of audio equipment including:
McIntosh 250 -power amp
Dared MP-15 -power amp
Consonance "Basie" -power amp
Audiosource Model Amp One -power amp
Kenwood KA-7300 -stereo integrated amp
Phase Linear 400 -solid state amp
SAE Mark 1B -stereo preamp equalizer
Akai GX-4000D -reel to reel machine
Rega Planar 3 -audiophile belt drive turntable

And last but not least... Some custom jobs. These appear to be home made tube amps and pre-amps. One of them has a logo on the front which I have never seen before.
(thanks to the guys over at AudioKarma I have since learned that these are Bottlehead amps)

So after a little research I have determined that I have a Foreplay II that has been customized to have an extra output similar to the Foreplay III. The thing that's confusing is that there is super old masking tape next to the outputs with old faded writing that appears to read something like "no follow AEON" next to one, and "cath___ follows AEON cap" next to the other.

So my question is... what's the difference between the 2 outputs? What's an AEON? Which one is better to go to the amp? and to the tape machine?

Any help is greatly appreciated. I have included a photo.
Thanks,
Al

 

[Paul Joppa]

On the left is a Seduction phono preamp. Middle is the Foreplay. Right is a stereo S.E.X. amp with what appears to be stock output transformers.

The Foreplay is probably modified. AEON is a capacitor - actually the "E" is a Greek capital xi, so I always write it as Axon. The marking is kind of cryptic - can you post a photo of the underside? I suspect there is a direct output after the voltage gain stage, and another output after the cathode follower - the presence of four Axon capacitors would tend to confirm that, but someone would have to see the wiring pretty clearly to be sure.

 

[Heavysound]

Gladly,
256k is the max file size for this site. If you need more detail, let me know and I'll post it HI-RES to my server.
Thanks,
Al

 

[Paul Joppa]

Good enough.

Looks like the Axon (black) caps come from tube pin 1 or 7 (they are connected) which is the VA plate, and go to the more forward output jacks. This output will only be able to drive short cables and high-impedance amp inputs, but has only one stage. The CF outputs, tube pin 8, are connect to the rearward output jacks with what appear to be Auricaps (yellow). That output can drive longer cables, and the caps are better, but the cathode follower is a second stage.

There are other changes I can see, for instance the VA bias resistor is bypassed with an electrolytic cap (tube pin 3) - probably to reduce the output impedance of the VA stage - and different resistors in the spike filter at the input of the power supply. Like many Foreplays, looks like this one was used for several experiments and is heavily modified. The mods I see are all intelligent and likely to improve the sound - over the years Bottleheads have been very creative people!

 

[Heavysound]

Good enough.

Looks like the Axon (black) caps come from tube pin 1 or 7 (they are connected) which is the VA plate, and go to the more forward output jacks. This output will only be able to drive short cables and high-impedance amp inputs, but has only one stage. The CF outputs, tube pin 8, are connect to the rearward output jacks with what appear to be Auricaps (yellow). That output can drive longer cables, and the caps are better, but the cathode follower is a second stage.

There are other changes I can see, for instance the VA bias resistor is bypassed with an electrolytic cap (tube pin 3) - probably to reduce the output impedance of the VA stage - and different resistors in the spike filter at the input of the power supply. Like many Foreplays, looks like this one was used for several experiments and is heavily modified. The mods I see are all intelligent and likely to improve the sound - over the years Bottleheads have been very creative people!

Well it's good that he knew what he was doing because I must say these things do make my records sound amazing!

But the rest of what you said was pretty much foreign jibberish to me. You'll have to excuse my ignorance. I probably shouldn't bother asking you to explain what is tube pin 7 or 8 or CF or a VA plate or the difference between first and second stage because I'm sure that's like trying to explain a kaliedoscope to a blind man.

Maybe it would help to see a simplified diagram that points more clearly to the pins and caps etc? Or do you have to order a kit to get that stuff? Can you tell me if I am using the correct output currently running to my SEX amp kit? When you say the "more forward" output jacks, do you mean the ones furthest away from the tubes?

I feel like an ant.

 

[InfernoSTi]

Congratulations Al...do you mind sending me seven random numbers? I need a bit of your luck and we have this little thing called a Lottery down here in Texas!  I have one thought: buy and build a Quickie pre amp. http://www.bottlehead.com/store.php?crn=220&rn=438&action=show_detail You have NO NEED for it but it will help a LOT with the terminology. It may still be foreign but you will have a perspective and understanding not elsewhere gained.  Besides, you just FOUND all that equipment: what's a hundred bucks at this point?  Oh, and I'm only half joking...  

I think this is my favorite Bottlehead thread ever!!! You are my new hero!!!  Welcome to the club...

John

 

[JC]

I'll take a whack at a few of those for you in the hope that you will be curious enough to want to learn more, and thus become on of us tube addicts!

As originally designed, each channel of the Foreplay consisted of two amplification stages: The first stage is a Voltage Amplifier, which takes the input signal and increases its amplitude or Voltage.  The Voltage Amplifier feeds the amplified signal to the second stage, a Cathode Follower.  The purpose of this stage is to provide a low impedance output signal.  Impedance is a complex subject, but suffice it to say that lower impedance is desirable for the output of the preamp because it has more oomph to drive the interconnects leading to the input of your power amp.

The nine pins on each of the tubes are numbered according to custom, with the wider spacing between Pin One and Pin Nine.  If you have trouble searching up one yourself, write back and I will attempt to link you to a diagram from a specification sheet for the 12AU7 tube in your preamp.  It is readily available on line, I'm just being lazy at the moment!

The 12AU7 actually contains two triodes in its glass envelope, each consisting of a Cathode, an Anode (often referred to as a Plate), and a Control Grid to modulate the current flow between the Cathode and Plate.  That accounts for six of the nine pins on the 12AU7, with the other three pins being used for the Heaters used to heat the Cathodes.

What Paul was explaining was that a previous owner added some parts to allow your Foreplay to output its signal from two places in the circuit.  One output comes directly after the Voltage Amplifier stage, and while its output impedance is relatively high, some prefer a single stage preamp and are willing to accept the lack of drive (using shorter interconnects and a power amp with a high input impedance helps to mitigate the issues) in order to achieve the added clarity that less circuitry in the path of the signal may provide.

The second output in each channel would be from the Cathode Follower, and would essentially follow the original design.  In this way, you have a choice and can audition for yourself which arrangement sounds best to you in your set-up, by simply switching the interconnects from one output jack to the other.

Now, the input impedance of a SEX amp is about 100,000 Ohms, so you should get sound either way.  Also keep in mind, though, that the SEX amp doesn't really require a preamplifier at all.  It can easily be driven to full output with a great many sources directly, so another experiment would be to connect a source directly to the SEX for a listen, thus eliminating BOTH stages of the Foreplay!

So, there's a taste.  If you want more, you've come to the right website, IMO, because there are many, many knowledgeable tube enthusiasts here that are happy to discuss the hobby, and you don't have to be one of them to get answers to your questions.

 

[Heavysound]

I'll take a whack at a few of those for you in the hope that you will be curious enough to want to learn more, and thus become on of us tube addicts!

As originally designed, each channel of the Foreplay consisted of two amplification stages: The first stage is a Voltage Amplifier, which takes the input signal and increases its amplitude or Voltage.  The Voltage Amplifier feeds the amplified signal to the second stage, a Cathode Follower.  The purpose of this stage is to provide a low impedance output signal.  Impedance is a complex subject, but suffice it to say that lower impedance is desirable for the output of the preamp because it has more oomph to drive the interconnects leading to the input of your power amp.

The nine pins on each of the tubes is numbered according to custom, with the wider spacing between Pin One and Pin Nine.  If you have trouble searching up one yourself, write back and I will attempt to link you to a diagram from a specification sheet for the 12AU7 tube in your preamp.  It is readily available on line, I'm just being lazy at the moment!

The 12AU7 actually contains two triodes in its glass envelope, each consisting of a Cathode, an Anode (often referred to as a Plate), and a Control Grid to modulate the current flow between the Cathode and Plate.  That accounts for six of the nine pins on the 12AU7, with the other three pins being used for the Heaters used to heat the Cathodes.

What Paul was explaining was that a previous owner added some parts to allow your Foreplay to output its signal from two places in the circuit.  One output comes directly after the Voltage Amplifier stage, and while its output impedance is relatively high, some prefer a single stage preamp and are willing to accept the lack of drive (using shorter interconnects and a power amp with a high input impedance helps to mitigate the issues) in order to achieve the added clarity that less circuitry in the path of the signal may provide.

The second output in each channel would be from the Cathode Follower, and would essentially follow the original design.  In this way, you have a choice and can audition for yourself which arrangement sounds best to you in your set-up, by simply switching the interconnects from one output jack to the other.

Now, the input impedance of a SEX amp is about 100,000 Ohms, so you should get sound either way.  Also keep in mind, though, that the SEX amp doesn't really require a preamplifier at all.  It can easily be driven to full output with a great many sources directly, so another experiment would be to connect a source directly to the SEX for a listen, thus eliminating BOTH stages of the Foreplay!

So, there's a taste.  If you want more, you've come to the right website, IMO, because there are many, many knowledgeable tube enthusiasts here that are happy to discuss the hobby, and you don't have to be one of them to get answers to your questions.

Wow. That was quite helpful.
I agree that less circuitry the better but 99% of the time I'm coming from a turntable which needs the initial pre-amp correct? Then realized I needed the RCA outputs to run to my tape machine for recording so I had to incorporate the ForePlay II. Then I needed the amp for the obvious speaker outs etc...  So I suppose I could eliminate the FP II but then I would lose my outputs.

In regards to your explanation of basic tube/electronic theory. It was very insightful but I'm still not clear which output I should be running to the amp. I guess the one with less circuitry which i guess would be the one labeled "no follow AEON". Actually I guess you are saying it's up to my taste?

That amp gets pretty darn hot after a while too. Not tube warmth but the actual metal plate is hot. Normal?

 

[JC]

Yes, going by a cursory look at the photo, and Paul's comments, I'd say the "no follow AEON" output is directly from the Voltage Amplifier.

When you throw a turntable into the mix, there are other considerations.  The output of a turntable requires a phono preamplifier, which the Foreplay does not include.  The Seduction is such a phono preamplifier, but its output could indeed go directly into the input of the SEX.

Having said all of that, I would encourage you both to try the different outputs on the Foreplay with the SEX or another power amp, and to try the SEX being fed directly from the output of a line level source such as a CD player or the output of the Seduction phono preamplifier.  You may not want to keep them in those configurations, but it would make for an interesting experiment.

The same could be said for trying each of the two outputs of the Foreplay in a given setup.  Only you will be able to judge which you like best.

As far as the heat issue goes, it would probably be a good idea if you could specify which piece of gear you are referring to.  The SEX will get pretty warm, but the Foreplay really doesn't.  I'm not sure about the Seduction since I don't own one, but I can't imagine that it gets all that warm either.

BTW, that is quite a haul!

 

[Wardsweb]

If you care to see more on your Bottlehead gear, I've got a few pages on my builds:

http://wardsweb.org/audio/foreplay.html

http://wardsweb.org/audio/seduction.html

http://wardsweb.org/audio/sexamp.html

 

[mediumjim]

Not to hijack...

I recently bought a pair of 50 year old University Speakers from a guy in the San Diego area.  I drove down to him from Los Angeles and this guy has a 2 story house that I'm guessing is 2500sq ft or so that is literally crammed with stereo gear...the guy even has several storage bins in his back yard. 

Most of the stuff has been to hell and back, but a lot of it is clean usable gear.  I asked how he gets it (hoping he wasn't a fence or something) and he cheerfully answered most of it is from storage locker auctions and such.  He had so much stuff that it took one of his helpers about 15 minutes to locate my new 50 year old speakers!  BTW, I paid a whopping $150 for them and the guy told me he only paid $15 for them...we were both happy...I wonder how much they would be if more knew that University Sound was owned and managed by Altec Lansing and that many of their upper end models have the signature Altec Sound and close to same driver quality. 

Jim

 

[Heavysound]

Not to hijack...

I recently bought a pair of 50 year old University Speakers from a guy in the San Diego area.  I drove down to him from Los Angeles and this guy has a 2 story house that I'm guessing is 2500sq ft or so that is literally crammed with stereo gear...the guy even has several storage bins in his back yard. 

Most of the stuff has been to hell and back, but a lot of it is clean usable gear.   I asked how he gets it (hoping he wasn't a fence or something) and he cheerfully answered most of it is from storage locker auctions and such.  He had so much stuff that it took one of his helpers about 15 minutes to locate my new 50 year old speakers!  BTW, I paid a whopping $150 for them and the guy told me he only paid $15 for them...we were both happy...I wonder how much they would be if more knew that University Sound was owned and managed by Altec Lansing and that many of their upper end models have the signature Altec Sound and close to same driver quality. 

Jim

Considering I'm in San Diego too, I probably know the guy. Did you happen to see any records?

 

[mediumjim]

Not to hijack...

I recently bought a pair of 50 year old University Speakers from a guy in the San Diego area.  I drove down to him from Los Angeles and this guy has a 2 story house that I'm guessing is 2500sq ft or so that is literally crammed with stereo gear...the guy even has several storage bins in his back yard. 

Most of the stuff has been to hell and back, but a lot of it is clean usable gear.   I asked how he gets it (hoping he wasn't a fence or something) and he cheerfully answered most of it is from storage locker auctions and such.  He had so much stuff that it took one of his helpers about 15 minutes to locate my new 50 year old speakers!  BTW, I paid a whopping $150 for them and the guy told me he only paid $15 for them...we were both happy...I wonder how much they would be if more knew that University Sound was owned and managed by Altec Lansing and that many of their upper end models have the signature Altec Sound and close to same driver quality. 

Jim

Considering I'm in San Diego too, I probably know the guy. Did you happen to see any records?


No records...he's in Chula Vista...

 

[HF9]

Wow... this seems like something I would dream about and then be disappointed when I wake up Congrats on all the great finds, you've got a lifetime of great equipment to enjoy.

 

[Heavysound]

Good enough.

Looks like the Axon (black) caps come from tube pin 1 or 7 (they are connected) which is the VA plate, and go to the more forward output jacks. This output will only be able to drive short cables and high-impedance amp inputs, but has only one stage. The CF outputs, tube pin 8, are connect to the rearward output jacks with what appear to be Auricaps (yellow). That output can drive longer cables, and the caps are better, but the cathode follower is a second stage.

There are other changes I can see, for instance the VA bias resistor is bypassed with an electrolytic cap (tube pin 3) - probably to reduce the output impedance of the VA stage - and different resistors in the spike filter at the input of the power supply. Like many Foreplays, looks like this one was used for several experiments and is heavily modified. The mods I see are all intelligent and likely to improve the sound - over the years Bottleheads have been very creative people!

Hey Paul, JC, and everyone else,
Just really wanted to say thanks. I've read your posts about a dozen times now and I think it's finally starting to make sense. I may have some more questions coming down the pipeline about another sex kit I just uncovered that looks different in the guts than the first one.
Thanks again,
Al