Finished my Foreplay Tuesday evening (thanks Quest).Sounds, well, astonishing. I’m running it through my DH 220 into Klipsch KG-4 speakers. I’m going to need LOTS more attenuation here, the DH 220 is too big for the Foreplay and Klipsch.
I just barely crack the Foreplay open and the KG-4’s produce a wall of near ear damaging sound. Balancing the two sides with the pots on the Foreplay is just plain impossible. I was going to do Paraglows next but the DH 220 is so sweet that I might just wait. I built that from a kit in 1980 or so and I think it was pretty much the last series of amps Dave Halfler designed before he died. I don’t have a lot to compare it too but I think it may be the most tube-like SS amp ever made.
I was listening to Melanie, Tangerine Dream, Miles Davis, and Michael Hedges. On that silly Melanie song about ringing bells, there are background vocals I’d never heard before. Michael Hedges guitar work is transparent, even austere. I can hear his fingers crossing frets. Tangerine Dream is vivid to the point of, well, not discomfort as such, but something.
The down side is that my jazz collection is mostly vinyl and for some reason the change in sound for my vinyl isn’t as vivid or astonishing as for the CD’s. I was really hoping to get more out of the Music Hall mmf-5 (now I’m really going to have to get serious about upgrading the interconnects on that puppy) and the Rotel RQ970BX phono-stage. I know that the Music Hall does really pretty music. The Rotel has served me reasonably well (I'm not thrilled but, what the heck). Still, something is just not happy there. Time for a Seduction I suppose.
The Foreplay has a heck of a hum. Probably my sloppy solder work somewhere. Going to have to live on VoltSeconds web site for a while debugging that.
Let’s see what to do next:
1) need (a lot) more attenuation. What is the fastest way to cut output in half (at least)?
2) Debug the *&(^*$ hum….
3) Snubber.
4) The cascode.My wife is pretty calm about this. It was her birthday yesterday and she was happy to spend the evening (after we came back from a birthday dinner, I’m not a complete lummox) listening to music with me. Apparently the decaffeinated Prozac is working.
Her opinion is that I got a winner here as soon as I get rid of the *&(^ hum. Starting to babble. I’m going away now.
Finish this line:Have Soldering Iron, will....
1) spend weekends in the basement.
2) hold up bits of twisted metal and wire making maniacal laughter.
3) burn myself.
4) expend enormous amounts of money.
5) cauterize the thumb I took off with the band saw.
6) ...
Follow Ups:
- Attenuation - Paul Joppa 16:57:47 05/09/03
(1)
- In Reply to: Another Forplay enters the world posted by Carl F on May 08, 2003 at 14:49:54:
The best place to put attenuation is often the amplifier's input, especially if very sensitive speakers are used. Since you built the amplifier yourself, you won't risk any warranties by adding a couple resistors to the input of each channel.
A good target is to set up the amp/speaker so that 0.316vRMS (-10dBV) will produce 82dB SPL from the speaker. Google tells me the DH220 puts out 115 watts with 1.55vrms input, so 0.316 volts should make 4.78 watts.
The KG4 was rated 94dB at 1 watt, 1 meter. To get 82dB would take 12dB less power, or 1/16 watt.
The ratio is 4.78/.063, or 76.48. The voltage ratio is the square root of the power ratio, so a ratio of 8.75 or 19dB would be about right. Round it to 20dB if you like - what's a few dB among friends, after all?! As others have mentioned, a simple L-pad at the input will do the job.
If further attenuation is needed (and it may well be needed) than it should go at the Foreplay input. There is lots of information on that part.
- Re: Attenuation - Carl F 06:24:17 05/14/03
(0)
- In Reply to: Attenuation posted by Paul Joppa on May 09, 2003 at 16:57:47:
Thanks for your help. Sorry it took so long to respond but we've had a bad week at work and I've been a little over stressed.
Thanks for your input. I'm still new at this and will have to work out the values of the resisters, etc. but this should be a great start.Thanks.
- Re: Attenuation - Carl F 06:24:17 05/14/03
(0)
- Off Topic: Michael Hedges - Jonathan Babiak 16:12:07 05/09/03
(1)
- In Reply to: Another Forplay enters the world posted by Carl F on May 08, 2003 at 14:49:54:
I was lucky enough to see Michael Hedges live in 1985. I went based on some sort of "Around Town" listing in the Dallas paper. I'd never heard of him. Amazing. His death was a tragic, tragic loss. Enjoy the music.
- Re: Off Topic: Michael Hedges - Carl F 07:31:58 05/12/03
(0)
- In Reply to: Off Topic: Michael Hedges posted by Jonathan Babiak on May 09, 2003 at 16:12:07:
Amazing guitarist. Saw him at Ravinia (near Chicago) around 10 years ago. Hard to believe a single guy standing on stage with an acoustic guitar can get that big a place rocking.
He did a version of Prince's (?) 'Love Bazaar' which sounded like a whole band. There was dancing in the aisles. Cool.
Too bad. Someone once told me that single car crashes in the desert are either falling asleep at the wheel or suicide. Don't know which in this case but both are a stupid way to die.
Peace.
- Re: Off Topic: Michael Hedges - Carl F 07:31:58 05/12/03
(0)
- David Hafler is still alive and ... - CharleyW 15:31:34 05/08/03
(5)
- In Reply to: Another Forplay enters the world posted by Carl F on May 08, 2003 at 14:49:54:
I also have a DH-220 (which didn't come out until 1982, by the way) and it doesn't hold a candle to either my Cucio'd ST-70 or Paramours.
It's still a good amp (and back then it was a great amp). I have a larger power transformer in mine (8 amp vs. 4 amp stock, 80 or 88 VCT if IIRC).
JMO, YMMV.
- Re: David Hafler is still alive and ... - Carl F 16:37:44 05/08/03
(4)
- In Reply to: David Hafler is still alive and ... posted by CharleyW on May 08, 2003 at 15:31:34:
DH is still alive? Truely? I had heard that he had died a while ago. Never checked it out because it was a reliable source and I had other things to do...
1982? That sounds about right. Late 70s, early 80s were a bit of a blur. Graduated college, several jobs, married, widowered. Tends to screw up your memory time sense.
I'd love to discuss your upgrades to your DH 220 or if you know of a web site... I was just thinking that it was time for a bit of a cleanup and tweaking. I just didn't want to start in on it until I had something to replace it with.
- Re: David Hafler is still alive and ... - CharleyW 09:09:52 05/09/03
(2)
- In Reply to: Re: David Hafler is still alive and ... posted by carl f on May 08, 2003 at 16:37:44:
The tranformer is the only significant thing I did (of course, with the obsession common to all of us, I should add SO FAR). I may have also jacked up the bias a little bit.
Not to continue assaulting your memory, but I believe Erno Borbely generally gets credit for designing the DH-200. The only changes in the 220 were mechanical (the input jacks were changed to side-by-side; the 200 had the left on the extreme left and right on the extreme right), some parts upgrades (carbon film resistors to metal film in some spots, better caps in some places) and a slight difference in the input circuit. This resulted in a new circuit board (the 220 and the 500 both used the same board).
There was a 2 part interview with David Hafler in Vacuum Tube Valley about two years ago focused entirely on his career through the Dynaco years.
- Re: David Hafler is still alive and ... - guycom 12:09:24 05/09/03
(1)
- In Reply to: Re: David Hafler is still alive and ... posted by CharleyW on May 09, 2003 at 09:09:52:
I once had a DH-200 and liked its very warm sound, would anyone know if the DH-500 has a very warm sound and if it was rated for use at 2 ohms? (I am driving infinity kappa 9's with a stock foreplay using RCA cleartops. Thanx for any help.
Guycom
- DH-500 - CharleyW 13:03:19 05/09/03
(0)
- In Reply to: Re: David Hafler is still alive and ... posted by guycom on May 09, 2003 at 12:09:24:
http://www.hafler.com/techsupport/pdf/DH-500_amp_man.pdf is the URL for the DH-500 manual.
I disticntly remember Hafler quoting a 4 ohm spec; the PDF'd manuals are later (they have a Rockford imprint) and don't mention anything but 8 ohm. I would not be suprised that they could drive a 2-ohm load, though; I always had the impression those amps could drive a crowbar.
- DH-500 - CharleyW 13:03:19 05/09/03
(0)
- Re: David Hafler is still alive and ... - guycom 12:09:24 05/09/03
(1)
- Glad you got it rolling - Sturgus 18:17:37 05/08/03
(0)
- In Reply to: Re: David Hafler is still alive and ... posted by carl f on May 08, 2003 at 16:37:44:
I find it simply amazing what the Foreply does for what it cost. You may want to try the (shunt-mode) on the pots. Also if you are looking for mods for your Hafler try Musical Concepts.
Sturgus
- Re: David Hafler is still alive and ... - CharleyW 09:09:52 05/09/03
(2)
- Re: David Hafler is still alive and ... - Carl F 16:37:44 05/08/03
(4)
- Congrats...suggestions - kdy 15:24:22 05/08/03
(0)
- In Reply to: Another Forplay enters the world posted by Carl F on May 08, 2003 at 14:49:54:
Carl F,
Sounds like you are on your way...with some more time spent on the Foreplay (and not much more $ at all), you can make it sing without hum and with the volume you want.
Hum...check this post I made:
http://java.AudioAsylum.com/cgi/m.pl?forum=bottlehead&n=57594&highlight=kdy+hum&r=&session=
I tried several easier things that others suggested before installing the filament snubber, which nailed it down, no matter what tubes I put in the FP.The filament snubber is explained by VoltSecond:
http://www.siteswithstyle.com/VoltSecond/foreplay_filament_snubber/Foreplay_filament_snubber.html
Scroll down to the proposed 6.3V version. Before you jump to this though - try the easier things like the 13-14 jumper and the power supply snubber. Check JOE's page for the power supply snubber and other noise/hum notes:
http://home.att.net/~joemacjr/diyproject/foreplay.html#Attenuation - for immediate relief, install a L-pad as decribed on many posts here. Again, Voltsecond's page will help you out a lot here, even if you only use a tiny fraction of the infor here:
http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html
Scroll down to section 6.0 and go from there.I recommend taking care of hum first, then attenuation, and then install the Anticipation upgrade and caps and whatnot (if you plan to do that). Anticipation before filament snubbers is a royal pain - trust me, I did it.
And for vinyl - when you get the cash and time saved up...replace the Rotel with a Bottlehead Seduction, and the Goldring 1012GX that comes with your Music Hall 5 with something that lives up to FP and other good stuff you have going. I had the 1012GX, and it's not a bad cart., but once I got the FP, Seduction, and other things going well in my system, it was apparent that it had to go. Went with a Dynavector 10x4 mk2, and I could not be happier for my budget. Just about everyone says the Music Hall 5 is a lot like a Rega Planar3, which I have. On the Rega, the 10x4 beat up on the 1012.
Good luck!
- kdy
This post is made possible by the generous support of people like you and our sponsors:
You can not post to an archived thread.
[
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]