Steve, many thanks for your thoughtful email. I need to properely digest it. I certainly agree with your comments about the way components change the sound but have found that most passive components sound different in different topologies - so I'm not sure how to judge their neutrality in absolute terms. I'm not sure how to judge any systems neutrality in absolute terms either. I've been chasing this for three decades now and still failing - I'm a broadcast engineer and educated to look for the BBC standard of neutrality. The problem is that, in absolute terms it is impossible to get a handle on the neutrality of loudspeakers or microphones. All that one can acheive is a consesus of expert opinion... and, of course, I'm right! Except I know that I, at least in absolute terms, am not right...
Having said all that, over time one certainly starts to narrow down the window that covers neutrality... I need to think some more on your words. Thank you for them.
Frank, Spot on the button again. Sometimes I think your comments are teasing or provocotive but more thought usually shows the insight behind them as well. Occasionally I can't find it - further time usually shows I missed it rather than it wasn't there... Thank you too.
ciao
James
Having said all that, over time one certainly starts to narrow down the window that covers neutrality... I need to think some more on your words. Thank you for them.
Frank, Spot on the button again. Sometimes I think your comments are teasing or provocotive but more thought usually shows the insight behind them as well. Occasionally I can't find it - further time usually shows I missed it rather than it wasn't there... Thank you too.
ciao
James
Thanks James
Thanks James and understand what you are saying.
I don't think the part, itself, actually changes sound characteristics unless a DC voltage causes it for some reason.
Excellent point James, "Narrow down the window that covers neutrality".
Never satisfied with the present, or the past, but moving forward towards perfection.
I think testing parts should be done by keeping the part "outside" of a component. Point one explains.
1) Install part between components (outside of each component), switching between straight wire and part.
Common components, ICs, switch contacts, etc are common to both, so they cancel out sonically.
Weaknesses are switching contacts could lower resolution of system and no DC voltage present on the part.
2) Could install DC component to the part and proceed as in idea 1.
Weakness is again switch contacts, and DC component requires extra part(s) which could color the sound.
Any ideas most welcome.
Hope this helps a little James.
Thanks James and understand what you are saying.
I don't think the part, itself, actually changes sound characteristics unless a DC voltage causes it for some reason.
Excellent point James, "Narrow down the window that covers neutrality".
Never satisfied with the present, or the past, but moving forward towards perfection.
I think testing parts should be done by keeping the part "outside" of a component. Point one explains.
1) Install part between components (outside of each component), switching between straight wire and part.
Common components, ICs, switch contacts, etc are common to both, so they cancel out sonically.
Weaknesses are switching contacts could lower resolution of system and no DC voltage present on the part.
2) Could install DC component to the part and proceed as in idea 1.
Weakness is again switch contacts, and DC component requires extra part(s) which could color the sound.
Any ideas most welcome.
Hope this helps a little James.
I noticed something the other day that worries me a little.
The DC resistance in the primary winding of a Hammond 1629SE (6,5k) OPT is close to 500 ohms, which means a voltage drop of 45V and a dissipation of 4W when running 90mA trought it.
Seems a bit much, or what do you fellows think?
Other options could be the Hammond 1628SE (5k) with ~350 ohms Dcr or 1627SE (2,5k) ~280 ohms with 8 ohm speakers connected to the 4 ohm tap (bad practice?)
After all 5k plate load seems a bit low for 813.
Lundahl OPT´s has much lower Dcr but also way lower primary inductance so they´re out.
The DC resistance in the primary winding of a Hammond 1629SE (6,5k) OPT is close to 500 ohms, which means a voltage drop of 45V and a dissipation of 4W when running 90mA trought it.
Seems a bit much, or what do you fellows think?
Other options could be the Hammond 1628SE (5k) with ~350 ohms Dcr or 1627SE (2,5k) ~280 ohms with 8 ohm speakers connected to the 4 ohm tap (bad practice?)
After all 5k plate load seems a bit low for 813.
Lundahl OPT´s has much lower Dcr but also way lower primary inductance so they´re out.
Paul: Yes, I´ve thought about that too. High DCR can´t be a good thing...
I guess the best thing would be to use a pair of 1642SE´s (5k, 75W 240 ohm) but they cost almost three times as much as the 1629SE.
The "regular" 5k hammond still has a DCR of 355 ohms which also is a bit high. Problems...
I guess the best thing would be to use a pair of 1642SE´s (5k, 75W 240 ohm) but they cost almost three times as much as the 1629SE.
The "regular" 5k hammond still has a DCR of 355 ohms which also is a bit high. Problems...
Ah, a friend gave me some measurements today that he had done on triode wired 813´s. At Ug=+20V the grid current is only 6mA, that invites to peak A2 operation.
+850V, 110mA, -67V, 5k load and +20 to - 154V input swing gives 29W!!!
That is 4W more than a Hammond 1628SE can handle, but what the heck...
Maybe I should mention that I have ordered input and driver tubes, 6C45 for input and 6C19 for driver stage. Those tubes alone would make a really nice ~3W amp so I guess they´re beefy enough to drive those 813´s into light A2 operation.
Setup will be something like this:
6C45 (resistive load) direct coupled to 6C19 - Lundahl IT - 813
+850V, 110mA, -67V, 5k load and +20 to - 154V input swing gives 29W!!!
That is 4W more than a Hammond 1628SE can handle, but what the heck...
Maybe I should mention that I have ordered input and driver tubes, 6C45 for input and 6C19 for driver stage. Those tubes alone would make a really nice ~3W amp so I guess they´re beefy enough to drive those 813´s into light A2 operation.
Setup will be something like this:
6C45 (resistive load) direct coupled to 6C19 - Lundahl IT - 813
Did you ever build an amp using the 813 and a hammond 1629SE? If so did you go straight triode or use the xfmer's 40% screen tap on the 813 G2? What PSU B+?How did it work out for you?
Hi!
No, I have not built this amp (yet). I did gather most of the parts though and the project is not "officially" abandoned.
Instead of Hammond transformers I got me a pair of Lundahl LL1688/80mA and an Antek 720V 400VA power transformer.
I´ve also bought most of the parts for a VCCS* filament PSU
* Voltage controlled current source
No, I have not built this amp (yet). I did gather most of the parts though and the project is not "officially" abandoned.
Instead of Hammond transformers I got me a pair of Lundahl LL1688/80mA and an Antek 720V 400VA power transformer.
I´ve also bought most of the parts for a VCCS* filament PSU
* Voltage controlled current source
Oh good. I am about to purchase a pair of the Hammond 1629SE's and with my recently acquired inventory of several good vintage made 813's I can finally think about making a breadboard of discovery and fun.
I would have been here years ago if Handjob Transformers had not screwed me on my paid order for a pair of 25 watt 10K SE's! Has anyone put a bullet through this criminal's head yet?
There´s a sad story behind my LL1688s: I decided not to use the cheap(ish) Hammonds due to the uneven HF response in the old 1628SE units, I was afraid that there would be similar problems with the 1629 as well.
After paying more than 2 times as much money for the Lundhals I discovered that they also showed HF irregularities. Soon after that Lundahl released a similar model with a less complicated winding scheme to replace the 1688 series...
After paying more than 2 times as much money for the Lundhals I discovered that they also showed HF irregularities. Soon after that Lundahl released a similar model with a less complicated winding scheme to replace the 1688 series...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.