Seduction Heater Resistor

[sl-15]

Hi, This post is pretty much directed at Paul Joppa but maybe somebody else can chime in too. There used to be a post from Paul on capacitor upgrade values for the Seduction. The same post had a chart showing what value heater resistor goes with which tube type. I had this one bookmarked but it is outdated by now. Maybe it got lost in between server switches and such. Paul if you still have that info somewhere and can post it that would be helpful. Thanks, Stefan

[Paul Joppa]

I have an FAQ draft in a file, dated October 2007, though the original may be older - changed computers a couple times... I'm not sure whether it was ever posted, or edited, or anything else.

In fact I found the file while looking for heater resistor values. It seems the poster's measurements are lower voltage than in the table, so it shows the trend but is not accurate.

Were we still on the Asylum back when those posts were made?

Maybe Dan remembers it.

[sl-15]

It was not on the Asylum format it was already Bottlehead being on its own forum. I remember that the post was about different values of caps that could be used in the output and coupling stage as these were substituted often with boutique or different caps. It was called Capacitor upgrade or similar. Sometimes I take screenshots of these posts as a reference but not with this one. Is it fairly easy to calculate the value of the resistor? I often switch between 6DJ8 and 7308 but never paid attention to the heater voltages before but I am about to do some measurements to find out if I need to change the resistor. Instead of searching for this old post of yours maybe it is easier if I just ask again on the forum when I have some data.

[Paul Joppa]

Good idea to ask the cap question in another thread. I don't have any notes on the coupling/output caps, but I'll invent something. I do have some notes on the RIAA equalization components which I will also post.

This thread is specific to the heater resistor, so I'll quote my old notes below. I am leaving out the table of resistances since it is not accurate, but I'll edit in a process to find the value.

Text of old notes from 2007 ==========================================

The world of 6DJ8 "compatible" tubes is a rat's nest - extremely complex, confusing, and rife with little brown pellets. One of the considerations is the heater power required. There are several supposedly compatible variants that actually have different current requirements:

6922: 300mA
6H23Pi: 310mA (this is the Russian so-called 6922)
7308: 335mA
6DJ8: 365mA

The above is important because it affects the heater voltage in the Seduction. Seduction is designed to operate at a nominal 6.0 volts DC; the 5% lower voltage giving a bit longer life and reduced noise. Anything in the range 5.7v to 6.3v will work well. In practice, a few tubes have been found to perform less well with 5.7 volts. Sometimes - but not always - this just means they will take longer to break in.

Remember that all tubes have manufacturing variations, and also the 6DJ8 family is also the most widely faked and mis-labeled, so don't be too surprised if your particular tube draws a different current from what the spec sheet says! :^(

Heater voltage is also affected by your power line voltage. The target voltage is normally achieved with a power line voltage of 122 volts, and the stock 1.2 ohm series resistor, using 6DJ8 tubes.

I recommend that you check your heater voltage before selecting a new tube. If it is high, you might want to look for a higher current tube to try, but if it is on the low side you should stick to the 6922 types. Typically, a 6922 will show 0.45v more than a 6DJ8, with the others falling in between in proportion to their current draw.

NEW TEXT: For those who want to adjust the resistor to adjust the voltage for a particular tube, a first estimate would be to calculate the resistor voltage drop and adjust using Ohm's Law. This will slightly over-estimate the change needed, so plan on iterating a time or two.

Note that, as nice as the 6N1P is, it draws too much current to use with the PT-1 power transformer.

[sl-15]

I found the post from Paul I was talking about:

http://bottlehead.com/smf/index.php?topic=2531.msg20257;topicseen#msg20257

[Paul Joppa]

Thanks, SL-15!

I reviewed that thread and I think it's still as valid as ever.