[jkarhan1]

Hey guys,
Would the Foreplay preamp be a good mate with the 55W AKSA?
Joe

[AKSA]

Hi Joe,

I'm told by Peter (PSP) that they go together well, but the Foreplay has lots of gain, around 23dB, and since the AKSA is very sensitive (with a gain of 32dB) the two together make for a hair trigger volume control.

You can reduce the gain of the Foreplay, but because of the direct coupled nature of the amp it changes the sonic characteristics and this is not recommended because it effectively redesigns the circuit.  Similar arguments apply to the high gain of the AKSA.  The most accessible way to reduce the Foreplay gain is simply to place a resistor string on the input, say 22K from source to Foreplay input, and 3K3 from Foreplay input to ground.  You could also replace the input level pot on the Foreplay with a 5K audio taper, and place a 33K from the top of the pot to the hot input socket on the Foreplay.  This way all signals are attenuated from infinity to 7.6 ([33+5]/5) and overall gain of the Foreplay is reduced to just 2, or 6dB.  This is the gain of the GK-1, and it works just fine.......

Cheers,

Hugh

[jkarhan1]

Thanks Hugh,
Then the TLP would work better?

[Vinnie R.]

Thanks Hugh,
Then the TLP would work better?

Hugh, are there known hum issues with the TLP?  The foreplay
doesn't come with a PCB and there have been many posts
about hum issues.  The TLP looks like a very straight forward
PCB layout.  Also, what are the dimensions of the TLP PCB?

Thanks,

Vinnie

[ultrachrome]

I have a Foreplay that I intend to mate with the AKSA 55W I just ordered.  Currently it's feeding an Adcom GFA-545II.

My Foreplay did have hum issues but they were easily fixed with a filament snubber.

[AKSA]

Hi Guys,

Yes, because they use sensitive vacuum tubes, both the Foreplay and the TLP need special but routine build techniques to minimize hum issues.

The TLP uses a trick cathode follower, however, which is reasonably resistant to hum by comparison with plate loaded critters because the gain is unity, not 15-25dB.

The biggest issue is hum fields from transformers.  The most effective methods to get it right are:

1.  Mount the transformer at least four inches from the TLP pcb;  orient the transformer (or the pcb) for minimum hum intrusion.
2.  Erect an earthed ferrous barrier between the transformer and the TLP.
3.  Keep the length of the wiper lead from level control to TLP pcb as short as possible.  In rare cases a coax is necessary to prevent hum intrusion.

Some people have found separate boxes for transformer and TLP are a good approach;  others have found that DC filaments are a good idea.  These are extreme measures, and I personally have never found it necessary to go to DC filaments, which I try to avoid because of added cost and complexity and the possibility of carbonizing the filament (they are designed for AC, and putting DC into them does asymmetrically charge the cathode, which technically is not a wonderful thing on a cathode follower.)

These are perennial issues on tubes, and perhaps the final frontier on all tube audio designs.  They are particularly severe on directly heated cathodes, such as 2A3s, 211, 845s, 300Bs - the big guys in tube audio - and most audiophiles with these tubes inevitably tolerate a small amount of hum on their speakers because it's almost impossible to eradicate every last millivolt.  But it's true - you do need a strong stomach with DHT designs, and you need to accept that the wonderful sonics of the DHTs come at a price.  The TLP is not a DHT, but an IDH triode, so these are not such an issue, though still important.

Great questions!  Keep 'em rolling..........      

Cheers,

Hugh
[/list]

[dayneger]

Hi Joe,

I've currently got a Foreplay in front of my AKSA 100W.

My take on this is that high gain plus high gain is not the coolest idea.  I had to massively attenuate the signal in the Foreplay in order to use more than, say, 1 degree of the pot swing.

I think they sound fine together.  Although the Foreplay is quite popular and I'm sure the basic circuit is fine, the actual physical layout of the product is quite odd and it seems to benefit/need an awful lot of tweaks here and additions there to fully come into its own (or simply work without hissing, humming, buzzing, etc.)  Some people seem to be lucky and have no problems with it the first time.  I wasn't, plus you simply cannot use it stock with the AKSAs--the gain is WAY too high.  I also don't like all my interconnects dangling everywhere, and very close to the tubes.

The Foreplay will remain in my system until I have both time and money to make a GK-1 with remote and then it's history.

Hope that helps,

Dayne

[jkarhan1]

Thank you so much for the feedback guys. I think Ill be saving my pesos for the GK-1. Keep it simple!

[PSP]

Hi Joe, et. al.,
As Hugh says, I've used a Foreplay (with filament and HV snubbers, DACT attenuator... I didn't like and my wife hated the 3db steps associated with the Sweet Whispers stepped attenuator, nor did I like the stock volume pot... metal-lined enclosure, 5uf Auricap output caps... basically all of the standard mods except the C4S boards) with my 55w AKSA Nirvana.  This is a very good-sounding combination and I can recommend it highly.  

That said, I like the TLP (and really like the TLP Nirvana) significantly better (GK-1 Stage II will be ordered sometime in early summer I expect).  What's the sonic difference?  Hard to say, because I never really had a chance to sit down and hear them A vs. B... there was a couple of weeks of DIY hammering in the basement workshop between the Foreplay + 55w AKSA system and the TLP + 55w AKSA system and sonic memory is short.  All I remember is turning on the TLP (awful hum for 5 secs, then quiet), putting on some Beethoven and thinking "Yup... this is what I've been looking for."  Then a couple of months later, with the TLP Nirvana thinking "Holy S**t, WOW, This is what I've been looking for!!!"

Right now, as I write, the Foreplay is in my system and the TLP/N is being built into its own chassis... so in a month or so, I should be able to answer this question very, very well.

I intend to keep the Foreplay (it's a good preamp) for a possible system in the family lake home.  Also, having a good spare preamp on hand is comforting, yes?  The TLP/N will mate with a 55w AKSA + Paradox-1s in the bedroom, and the GK-1 will go in the main system (biamped AKSA 55s --> moded Energy exl-26 --maybe these will be replaced with AKSOnics, or possibly the GR-Research MTM version of the Criterion, if/when Danny offers it for sale.

Good luck,
Peter