[mlundy57]

Not sure if this is the right place to ask this or not.

I just bought a used Jolida JD-801A integrated stereo amp. I was planning on using this amp with two part speakers. The top portion covers ~250 Hz and up, is passive and connects via speaker cables. The bottom part covers 20Hz - 250Hz, is active and has its own plate amp.

The JD-801A does not have any preamp outputs. I can use a Y-adapter and split the input signal before connecting to the 801A. While this does send a full range signal to the subs, it does not go through the volume control. I need both signals, active and passive, to pass through the same volume control.

The most elegant solution would be to add left and right preamp outputs to the 801A. I don't even know if that can be done or how to do it if it can.

Anybody got any ideas?

Thanks,

Mike

[richidoo]

Congrats on the new amp, it looks sweet!

Does the plate amp have speaker level inputs? That would be the easy way, so I assume it does not. That would have the advantage of eliminating any phase difference between the pre tube-amp signal and the post tube-amp signal, so that the bass' and mid's phases are always aligned, or at least as aligned as the plate amp allows. The drawback of using the speaker level inputs is that the tube amp may not have preserved the bass "slam" of the original signal, and you may want that harder clearer ss sound in the bass. But the jolida's low freq specs are pretty good, looks like the bass might be pretty taut. Also, I have found that very different type amplifiers don't mix well especially as the crossover freq rises up into the midrange or treble. If you feed the output of the tube amp into the plate amp you will reduce the difference in sound to some degree as compared to feeding each amp the original signal. You are prebuttering the signal for the plate amp to sound like the tube amp to get a better tonal blend.

If your plate amp doesn't have speaker level inputs, you can very easily make your own:
http://www.epanorama.net/circuits/speaker_to_line.html
Your plate amp's volume control will allow fine tuning of the input if it's too strong. The integrated amp will have more gain to ditch than this 10:1 pad offers, so you can adjust it to suit your needs, there are instructions for modding the design. Use DaleVishay C55 or C60 metal film resistors (CMF.)

A good tube tech can add the preamp outputs. Schematics for Jolida are sometimes available online, or call them. I think you would take the signal after the driver tube and its coupling cap (if there is a cap.)  You could take it after the volume control but it would not be buffered, and the plate amp probably has a lowish input impedance, so you'll want the current of the driver tube to drive the sub's input, especially for LF signals. You'll need a resistor pad after the driver tube to bring it down to line level anyway, so your only advantage of preamp outputs is avoiding the output tubes (no big advantage) and the output transformer (more of an advantage because there is more distortion here.) I would try the speaker level pad before modding the amp.
Rich

[mlundy57]

Thanks everybody for both the replies in this post and the PM's. The high level speaker connection from the binding posts to the sub's plate amp worked for integrating the sub with volume control in my current 2.1 system.

I called Jolida and the speaker level connection to the plate amp was their solution for the current 2.1 system also. However, it became apparent during the discussion the there was no way to directly use the 801A (or even the new 801brc) with full range speakers that have both active and passive components and use a capacitor inline as a high pass filter. Since the 801 (either A or brc) is integrated, there is no way to get the HPF between the preamp and the power amp.

The solution is to add a JD-5T tube preamplifier to the 801 basically turning it into separates rather than an integrated amp. The 5T has 4 selectable inputs, 2 sets of outputs and a remote volume control (the 801A's volume control is not remote). At $549 the JD-5T is a relatively inexpensive solution that keeps the 801A making beautiful music.

Thanks again for your help.

Mike