Technical Library ACTION VII: Delrin conversion Entire Contents Copyright © 2021 CBH

Two Goble harpsichord jacks: The one on the left retains its original leather plectrum, while the one on the right has had the original tongue replaced ready for a Delrin wedge to be inserted and voiced.

Delrin conversion…
The original leather plectra of many twentieth century revival harpsichords made in the 1950s and 60s are well past their use-by date. As a consequence, most of these instruments now have unreliable touch and tone, with weak, broken or missing plectra making them frustrating to play. Few makers or technicians consider it good practice today to try to replace the original leathers on these instruments with fresh, but they can be somewhat resurrected by converting their tired old leather plectra to Delrin or Celcon, followed by careful revoicing and regulating.

We have movies showing the Delrin conversion process for the action of harpsichords by three prominent English makers of this period: Goble, Morley, and de Blaise. Each movie has accompanying explanatory text:

• Early Goble instruments with leather plectra in plastic jacks are best converted by replacing the original tongues with modern Goble tongues, mortised to hold the usual Delrin quills (see picture at right).
• The plastic jack action of Morley instruments can be converted using Morley’s proprietary moulded Delrin plectra which have a block base. This snaps into the vacant rectangular mortise after the original leather is completely removed from the plastic tongue. Morley are still in business in London, and their moulded plectra can be obtained directly from them. Note they are not suitable for use in other makes of instrument, most of which have square mortises for leather.
• The de Blaise instruments can be converted using our usual Delrin plectra, held in the wooden tongue by the original leather stub which has been punched out and then carefully trimmed for the purpose. Many other makes of revival instruments can be converted to Delrin using this technique. However, some instruments like Sperrhake with particularly fragile tongues are best converted by fitting new wooden tongues punched for Delrin.

We regularly undertake Delrin conversions either in the field or our Sydney workshop. The work is tedious and time-consuming. It should be noted that while the touch and reliability will be much improved, the subject harpsichord remains a thirty- or forty-year old instrument with the typical heavy case construction of the period and corresponding lack of tone. (This is reflected in the resale value of these instruments—much reduced from their true replacement cost or in comparison with instruments of decent quality based on historical principles of construction.)

		Goble Delrin conversion Carey Beebe demonstrating the conversion of the original 4⁠´ leather plectra to Delrin on a 1974 Goble harpsichord.
		Morley Delrin conversion Carey Beebe demonstrating the conversion of the original leather plectra to Delrin on a Morley virginal.
		de Blaise Delrin conversion Carey Beebe demonstrating the conversion of the original leather plectra to Delrin on a de Blaise harpsichord.

	Technical Library overview
	Harpsichords Australia Home Page